CA1120005A - Capsules and pressings for extruding objects, particularly tubes, and a process for producing the capsules and pressings - Google Patents
Capsules and pressings for extruding objects, particularly tubes, and a process for producing the capsules and pressingsInfo
- Publication number
- CA1120005A CA1120005A CA000338386A CA338386A CA1120005A CA 1120005 A CA1120005 A CA 1120005A CA 000338386 A CA000338386 A CA 000338386A CA 338386 A CA338386 A CA 338386A CA 1120005 A CA1120005 A CA 1120005A
- Authority
- CA
- Canada
- Prior art keywords
- capsule
- wall
- pressing
- insert
- powder
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/12—Both compacting and sintering
- B22F3/1208—Containers or coating used therefor
- B22F3/1258—Container manufacturing
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/20—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces by extruding
Landscapes
- Manufacturing & Machinery (AREA)
- Mechanical Engineering (AREA)
- Engineering & Computer Science (AREA)
- Powder Metallurgy (AREA)
- Extrusion Moulding Of Plastics Or The Like (AREA)
- Formation And Processing Of Food Products (AREA)
- Extrusion Of Metal (AREA)
- Pressure Welding/Diffusion-Bonding (AREA)
- Jellies, Jams, And Syrups (AREA)
- Blow-Moulding Or Thermoforming Of Plastics Or The Like (AREA)
- Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)
- Closures For Containers (AREA)
- Treatment Of Steel In Its Molten State (AREA)
- Press-Shaping Or Shaping Using Conveyers (AREA)
- Food-Manufacturing Devices (AREA)
- Meat, Egg Or Seafood Products (AREA)
- Auxiliary Devices For And Details Of Packaging Control (AREA)
- Forging (AREA)
- Heterocyclic Carbon Compounds Containing A Hetero Ring Having Oxygen Or Sulfur (AREA)
- Medicines Containing Plant Substances (AREA)
- Medicinal Preparation (AREA)
Abstract
A b s t r a c t This invention relates to a capsule for pressings pressed by isostatic pressure and to these pressings used for extruding metallic objects, particularly tubes, of stain-less steel, the outer and inner wall of the capsule con-sisting of thin-walled sheet metal, and at least the outer wall having substantially the same strength properties in the axial direction over its circumference and particularly consisting of a spiral-welded tube and being preferrably provided with a bulge which is directed outwardly against the shrinkage occurring during isostatic pressing, and at least on the front end of the capsule an insert being pro-vided, which consists of one or more pieces of a ductile solid material or a ductile material pressed from powder.
The invention further relates to a process for the pro-duction of such capsules and pressings and to a process for extruding tubes and to the tubes obtained according to this process.
The invention further relates to a process for the pro-duction of such capsules and pressings and to a process for extruding tubes and to the tubes obtained according to this process.
Description
_ 3 _ 1 l'his invention relates to a further development of the process for the production of tubes of stainless steel described in German printed application DE-AS 24 19 014.
Said German printed application DE-AS 24 19 014 relates to a process for the~production of tubes of stainless steel having a uniform structure~ uniform physical and chemical properties and good urther processing properties, in which powder-form steel of the type in question is introduced into metallic capsules; the capsules are closed and compressed by a pressure actin~ on all sides thereof and the pressing obtained is extruded into tubes, steel powder of predominantly spherical particles produced by sputtering or atomizing melt in an inert gas atmosphere being used and the capsules used being thin~walled capsules of a.
ductile metal ha~ing a ma~i~um wall thickness corresponding to approximately 5 % of the external diameter of the capsule;
the density of the steel powder introduced into the capsule is increased to between about 60 ~nd 70 % of the --theoretical density by vibration and/or ultrasound; the density of the steel powder is increased to a~ least 80 %
and pre~erably to between ~0 % a~d 92 % of the theoretical density by isostatic cold pressing of the capsule under a pressure of at least 1500 bars; the pressing is heated ~nd subsequently hot-extruded, preferably at temperatures of at least about 1200~C5 to form the required semi-finished product.
According to the German printed application DE-AS 24 19 014 it can be of advantage to evacuate the metallic capsules filled with the steel powder before they .' , ~.
~26~0~5 1 are closed and/or to fill the~ ~ith a gas, particularly an inert gas, for example argon, In addition, according to the German printed application DE-AS 24 19 014, it is preferred to use metallic capsules of which the wall thicl;ness amounts to less than 3 % and more particularly to less than 1 % of the external diameter of the capsule, metallic capsules ha~in~ a wall thiclcness of from about 0.1 to 5 mm and preferably from about 0.2 to 3 mm being particularly preferred.
Using the process according to said German ~rinted application DE-~S 24 19 014, it is also possible to produce composite tubes using thin-walled metallic capsules which are separated by one or more concentric partitions into two or more compartments. The predominantly spherical powder particles of the various steel qualities are respectivellJ introduced under vibration into one of these compartments, after which the partitions are removed and the capsules closed, followed by isostatic cold pressing and extrusion at elevated temperature~ For extruding the pressings into tubes, glass is normally used as the lubricant. Since stringent demands are imposed on the lubricant in the extrusion of 9 in particular, stainless steels at elevated temperatures, the pressing is required to have a substantially flat end face so that the lubricant applied to the end face of the pressing in the form of a gLass disc is effectively utilis ed.
It has now been found that extrusion is accompanied by the development of surface faults in the front part of the extruded product on account of the fact that the flow pattern in the transition between the cover and the jacket is seriously disturbed through the disturbing effect of welding. This causes significan~ losses in the yield of end produc~.
V~3~
The object of the present invention is to increase the yield, i.e.
to reduce the percentage of defective products after extrusion.
The invention provides a capsule for producing a pressing for use in extrusion of a dense metallic tube said capsule comprising a tubular thin-walled sheet metal container having an inner and outer wall and a space therebetween of annular cross-section to be filled with powder of metal or metal alloys or mixtures thereof or with mixtures of powders of metals and/or metal alloys with ceramic powders9 and having inserts for closing each of its opposite ends~ at least said outer wall of the capsule being provided with a bulge which is directed outwards and against the direction in which shrinkage will occur during subsequent isostatic pressing, the dimensions of said bulge being selected such that said bulge will be substantially eliminated by said shrinkage.
From another aspect, the invention provides a process for forming a capsule for producing a pressing for use in extrusion of a dense metallic tube, said process comprising providing a tubular, thin-walled, sheet metal container, said container having an inner and an outer peripheral wall;
reducing the diameter of opposite end portions of the outer peripheral wall, so that intermediate those end portions said outer peripheral wall defines a bulge which is directed outwards against the direction of shrinkage which will occur during subsequent isostatic pressing, the dimensions of said bulge being selected such that it will be substantially eliminated by such shrink-age, and providing inserts for closing the opposite ends of said container.
The construction of the capsule according to the invention affords the advantage that, after the cold isostatic pressing of the capsule, the pressing is not in the form of a "sand glass" with a central constriction.
In many cases, this so-called "sand glass" form arises out of the fact that the ends of the capsule, which are closed by covers or the like, undergo less shrinkage during cold isostatic pressing than the central part of the capsule.
Since a pressing having a substantially cylindrically outer wall is required for extrusion, the ends of the pressing have to be trimmed where it is in the form of a "sand glass", which is not only a very expensive operation, but also i~ ` A
~ 5 -involves the danger of cracks being formed. The construction of the capsule according to the invention affords the advantage that there is no longer any need for the pressing to be trimmed to make it cylindrical. In addition, it is possible by the invention to obtain pressings of which the diameters exactly correspond to the required diameters. According to the invention, it is possible to obtain accuracies of + 0.2 % and, more particularly, of + 0.1 %. In other words, the pressings can be produced with absolute diameters accurate to + 0.2 mm and more particularly to + 0.1 mm.
The outer wall and/or inner wall of the capsule according -- Sa -' , , ~ , , ' ~ : , s 1 to the invention are preferably produced in the form of substantially cylindrical sections at the ends of the capsule, the diameters of ~hich exactly correspond to those of the required pressing and which steadily merge into a bulged, S central region of the capsule.
According to the invention, the outer and/or inner ~all of~the capsule is/are ad~Jantageously shaped in such a way that, from each of the cylindrical sections at the ends of the capsule, the bulge gradually and steadily increases in the axial direction (looking towards the middle of the capsule) initially in a region having an ou~ardly concave cross section~ the inclination of the outer and/or inner ~all relatively to the axis of the capsule also gradually and steadily increasing, followed preferably by a conical intermediate region in which the inclination of the outer and/or inner wall remains substantially constant, this conical intermediate region being followed by a region in which the outer and/or inner wall has an outwardly convex cross-section and gradually and steadily merges into an axially parallel central section which preferably has a substantially constant diameter.
According to the invention, it is also possible to improve the dimensional accuracy of the pressing and to reduce the number of rejects by arranging a plate-shaped, conical, hemispherical or funnel-shaped insert of solid material at the front and/or rear end of the capsule.
The provision of inserts such as these considerably improves the flow properties during extrusion of the pressing and increases the yield of stainless material bec~use the inserts ~ich preferably consist of an electrically Cc~ G~
co~uct~ material, preferably soft iron or a low carbon sof~ steel, form the ends of the extruded tubes which have to be cut off ~2c~ 5 1 in any case In addition, the presence of the inserts preferably consisting of an electrically ~ metal at the front and/or rear end of the capsule makes the pressing much easier to heat by induction before extrusion because the metallic inserts may readily be treated by induction and give off their heat to the remaining parts of the pressing, particularly to the powder-filled interior thereof, thus contributing towards the rapid heating of the pressing as a whole.
It has proved to be of particular advantage to combine the provision of the above-mentioned-inserts at the front and/or rear end of the capsule with the provision in the outer and/or inner wall of the capsule of a bulge which is directed outwards and against the shrinkage occurring during isostatic pressing and of which the dimensions are such that it is substantially eliminated again by the shrinkage effect.
According to the invention, this combination enables the dimensions of the pressing tv be kept considerably more accurate. In particular, it is possible to keep the dimensions of the pressing accurate to ~ 0.05 % or, in absolute terms7 accurate to ~ 001 mm or more~ which is of considerable importance for the fault-free production of extruded articles, particularly extruded tubes.
According to the invention, the inserts may be in the 25 form of covers ~hich close the capsule at its ends and may ~
be tightly welded to the outer and inner ~alls of the capsule. ~-Sheet metal inserts in the oxm of covers may with advant~ge also be provided between the inserts ~nd the interior of the capsules and may be tightly welded to the outer and inner walls.
According to the invention, it is possible in the case of capsules for the production of pressings for extruding ~Z6~
1 tubes to use funnel-shaped, centrally bored inserts for the front end face of the capsules, the angle ~ between the ~all of the central bore for the inner wall of the capsule and the conical outer surface of the funnel-shaped insert amounting to between about 40 and 609 preferably to between about 40 and 50 and, more particularly, to about 45.
According to the invention, it can be of advantage in the production of tubes to provide at least on the front end of the capsule a centrally bored annular insert which _ 9 _ 1 has a substantially flat end surface and of which the boundary suxface between the wall of the cen~ral bore and its largest diameter has a substantially f3rcuate cross-.~ectional profile, the centre of the arcuate profile lying substantially in the vicinity of the intersecting line between the flat end face and the central bore.
According to the invention9 Enother significant improvement in the capsules and the pressings and ex~ruded articles, particularly extruded tubes, produced from them9 may be obtained in combination with or independently of the above described inserts constructed in accordance with the inve~tion by ensuring that at least the outer wall of the capsule has substantially the same strength properties ~
in the axial direction over its entire circumference. ~ -According to the invention, at least the outer wall of the capsule is preferably ~ormed by a thin-~alled, spiral ~elded or extruded tube. Forming the outer wall of the capsule in this way affords the advantage that extruded products~
particularly tub s, characterised by a considerably reduced number of ~aults and~ hence~ rejects are obtained.
The pitch of the spiral formed by the weld seam in relation to the length of the capsule is preferably such that the weld seam approximately forms one complete turn.
An outer wall provided with a weld seam such as this has only one weld seam at any point along its circumference in the axial direction and, therefore~ shows substantially the same strength properties in the axial direction.
Alternatively, the weld seam may form two, three or more complete turns.
The present invention is appli~ble ~o capsules and pressings for extruding objects, particularly tubes J bars or similarly profiled, elongate, dense metalli~ objects, 20(?~5 _ 10-1 particularly of stainless steel or highly alloyed nickel steels, particularly heat~resistant steels for heat exchangers, for example highly alloyed nickel steels containing approximately 80 % of nickel and 20 % of chromium, powder S of metal or metal alloys or mixtures thereof or mixtures of powders of metals and/or metal alloys with cerami~ powders beingintroduced into the capsule according to the invention.
The powder used is preferablyspherical or predominantly spherical powder having a mean particle diameter of preferably less than 1 mm. According to the invention7 ;t is preferred to use spherical powder which has been produced from the required starting material, i.e. the re~uired metal and/or metal alloy, by sputtering in an inert gas atmosphere, preferably an argon atmosphere.
Powder particles larger than 1 mm in diameter are preferably separated out, at least to a predominant extent, because argon is in danger of being included into powder particles larger than 1 mm in diameter. An inclusion of argon such as this can oc~ur during sput~ering, for example through turbuIence. Any incluslon of argon w~uld give rise during extrusion to un~avourable properties of the extruded articles and would lead to inclusion lines~
According to the invention, the capsule used for producing the pressings for the tubes to be extruded is filled with the powder~ the density of the powder introduced into the capsule being increased by vibration to between about 60 and 71 % o the theoretical density and the frequency of the vibration preferably amounting to at least about 70 Hz and advantageously to between 80 and 100 Hz. By vibration at a frequency of from 80 to 100 Hz, it is possible to obtain a density o~ from about 68 to 71 % of the theoretical density.
1 After the powder has bPen introduced and compacted by vibration9 the capsule is ~losed, preferably after evacuation and/or filling with an inert gas. Thereafter the density of the powder is increased to at least 80 to 93 % of the theoretical density by isostatic cold pressing under a pressure of at least 4000 bars, preferably under a pressure of from 4200 to 6000 bars and, more particularly, under a pressure of from 4500 to 5000 bars.
Capsules of thin sheet steel9 preferably about 1 to 2 mm thick sheet steel and, more particularly, approximately 1.5 m6n~ick sheet steel~ have prc~ved to particularly advantageous.
The material used for these capsules is preferably low-carbon soft steel, particularly steel having a carbon content of less than 0.015 ~/O and, better still, less than 0.004 % in order to prevent the powder from carburising during heating and extrusion.
Under the effect of the pressure applied on all sides during cold isostatic pressing, the capsule is uniformly compressed both in the longitudinal and in the radial direction and t~us forms a pressing. This pressing should h~ve no irregularities because this ~ould give rise to difficulties during extrusion~ particularly during the extrusion of tubes.
In order to produce a pressing for extruding a tube, an annular capsule is used, the outer wall of this annular capsule being ~ormed by a spiral-welded tube sectionproduced for example ~rom an approx;mately 1.5 mm thick sheet.
An inner wall, for example in the fo~m of a iongitudinally welded tube sectîon9 is introduced into the interior of the outer wall, ha~ing a smaller diameter than but the same wall thickness as the outer wall~ An annular cover is then ~ixed between the outer wall and the inner wall a~ one end ~Z~ 5 1 and the annular space between the two tubes is thus closed at one end. Spherical powder is then introduced into the an~ular space and compacted to around 68 % of the theoretical density by vibration at a ~requency of, for example~ 80 Hz.
A vacuum is then applied and the other end of the annular body is sealed off by a corresponding second cover. This is followed by cold isostatic pressîng in a liquid, for example water, under a pressure of9 for example~ 4700 bars.
Under the effect of the pressure applied on all sides, a pressing having a density of 9 for exampleg 85 % of the theoretical density is obtained.
In the capsule according to the invention, the spiral weld searn is required to be as smooth as possible with as --little effect as possible on the properties of the sheet steel. Accordingly, the weld se~m is preferably smoothed by rclling and/or grinding. The smoothing of the weld seam by rolling may be carried out immediately after welding.
In the case of capsules for the production of ~ubes, it can be of advantage to produce not only the ou~er wall, but also the inner wall from a tube wh;ch has substantially the same strength properties in the axial direction along its circumference. In this case, the inner wall may consist either of a spiral-welded tube or of an extruded tube. The use of an extruded or spiral-welded tube for the inner wall is particularly advisable in the production of large tubes.
In the production of smaller tu~es, it is generally sufficient in accordance with the invention for the outer wall of the capsule to be produced from a tube section which has substantially the same strength properties in the axial direction along its circumference.
An embodiment of the invention is described by way of example in the following with reference to the accompanying ~2~
1 diagrammatic dra~ings, wherein:
Figure 1 is an elevation of a capsule open at its upper end~
Figure 2 is a longitudina1 section through 8 modified embodiment of the capsule.
Figures3 to 6 are partial sections through other embodiments.
In Figure 1, the capsule is generally denoted by the reference 1~ ~he capsule has an outer wall 2 and inner wall 4. ~he outer wall 2 consists of a spiral-welded tube section ha~ing a length L. The weld seam 5 extends spirally over the circumference of the outer wall 2, the spiral having a helix angle a such that the spiral orms approximately one complete turn.
It has been found to be of advantage to arrange the weld seam 5 in such a way that it forms one complete turn between the weld seam 16, which is used to weld the cover (not shown in Figure 1) of the capsule firmly to the outer wall 2, and the weld seam 26 by means of which the base of the capsule is joined to the outer wall. The distance between the weld seams 16 and 26 is denoted by the reference L~ in Figure 1~ This length Ll may be regarded as the effecti~e length of the oapsule. It is advisable to select the helix angle a of the spiral weld in such a way that tg ~ ~ L
n Otr O D
where D is the diameter of the c~psule and n the number of turns ~ich the spiral weld seam 5 is required to oomprise.
- It has been found to be advi~a~le for n to have a value of 1, However, it may also be of advantage for n ~o have a value of 2,3~4 or to be equal to a larger whole n~mber.
In one practical example, the outer wall 2 and also the 1 inner wall 4 o~ the capsule 1 consisted of 115 mm thick soft sheet steel having a carbon content of less than 0.004 %.
The cover, which is not shown in Figure 1,was welded in along the weld seam 16. To produce the pressing, powder which consisted predominantly of spherical particles having a mean diameter of less than 1 mm and ~lich had been produced from the required starting material, for example stainless steel9 by sputtering in an argon atmosphere, was introduced into the capsule, After it had been introduced into the ~apsule, the powder was compacted to a density of, for example~
approximately 68 % of the theoretical density by vibration at a frequency of, for example, 80 Hz. The capsule was then evacuated and closed by means of a cover~ The cover was directly joined to the outer wall 2 of the capsule by welding substantially along the line 16 in Figure 1. - In the example in question7 the capsule had a len~th of 60Q mm and an external diameter of 150 mm The internal diameter of the inner wall 4 was approximately 55 mm. The inner wall 4 consisted of a longitudinally welded tube section with a longitudinal weld seam 6. The powder was then compressed for example to around 88 /~ of the theoretical density by cold isostati~ pressing under a pressure of, for example, 4700 ~ars, ~he pressing thus obtained was extruded into a tube a~ described in said German printed application DE-AS 24 19 014.
In the embodiment illustrated in Figure 2, inserts 30 and 40 are arranged in the region of the cover 10 and the base 20, fonming the front and rear end face, respectively, of the capsule. The front insert 30 is generally conical and comprises a central bore 32 for receiving the inner wall 4 of the capsule. The conical surface 36 of the conical or funnel-shaped insert 30 fonms wi~h the wall of the bore 32 1 an angle ~ ~hich is preferably in the range from about 40 to 60, advantageously in the range from about 40 to ~bout 50 and, more particularly, of the order of 45~.
The insert 30 comprises a substantially flat end face 34.
However, it is bevelled or rounded off at its outer edge (at 35) and then comprises a cylindrical section 37 which merges into the conical surface 36. The transition from the conical surface 36 to the wall of the central bore 32 is rounded off at 39. The cover 10 in the form of a sheet-metal insert corresponds exactly in its contour to the adjbining parts of the insert 30. More particularly, the co~er 10 comprises along its outer edge a cylindric~l section 17 which provides for firm contact between the cover 10 and the outer wall 2, the outer edge of this cylindrical sec~ion 17 being joined to the outer wall 2 by means of a weld seam 16. In its inner region, too, the cover 10 comprises a short, substantially cylindrical section 19 which is in contact with the inner wall 4 of the capsule and w~ich is tightly welded to the i~ner wall 4 `
at .18 by means of a weld seam. The cover 10 also comprises a rounding-off corresponding to the rounding-off 39 of the insert 30.
Arranged at the rear end of the c~psule 1 is an insert 40 in the form of a substantially flat plate which comprises a central bore 42 ~nd an outwardly directed ~nd face 44.
This plate-like insert 40 is also bevelled or rounded o~
at its edge (at 45) and comprises an outer cylindrical section 47. The base 20 of the capsule corresponds in shape to the shape of the insert 40 and also comprises an ou~er cylindrical section 27 and an inner cylindrical section 29~ The base 20 is tigh~ly welded to the outer wall 2 and the inner ~all 4 by means o weld seams 26 and 28, o~
respectively. The inserts 30 and 40 preferably consist of soft iron or low carbon soft steel.
Figure 3 shows a modified embodiment of the capsule in which an insert 130 provided at the front end of the capsule 5 comprises a substantially arcuate cross-s~ctional profile 136, a flat end face 134 and a central bore 132. The centre of the arcuate cross-sectional profile 136 are situated on a circle substantially in the ViCiTlity of the intersecting line between the flat end face 134 and the wall of the 10 bore 132) i.e. in the region of the front boundary line of the bore 132. This circle is indicated by two crosses at 138 in Fig. 3. The substantially arcuate cross-sectlonal profile 136 affords the advantage that, during extrusion of the pressing, the insert 130 consisting of soft iron or 15 a similar metal,, together with the cover 110, the weld seams 116, 118 ~nd the adjacent parts of the outer wall 102 and the inner wall 104, forms the first part of the ~ube ~ich is cut off or even drops off automatically after extrusion if the connection to the following tube preferably consisting 20 of stainless s~eel and produced from the powder filling of ~he capsule lacks sufficient strength. The effect of the substantially arcuate shape o che boundary llne 136 of ~hP
insert 130 is ~hat the d;viding line between the front part of the extruded tube, which acc~nulates as waste, and the 25 a~tual tube consisting of high quality stainless steel is clearly defined and is in the form of a separation surface extending substantially perpendicularly of the longitudinal axis o the tube. The cover 110 also comprises a substantially cylindrical section 117 which is welded at 30 116 to the outer wall 102 of the capsule7 and a substantially cylindrical inner section 119 ~ich is in contact with the inner wall 104 and w~ich is tightly welded to the inner wall .
l~LZ¢)~5 - 17 _ 1 at 118 by means of an encircling weld seam~ The transition from the wall of the central bore 132 to the circular cross-sectional profile 136 is rounded of~ at 139.
It can also be of advantage for the inserts 30 and 40 to be directly welded to the outer wall 2 and the inner ~all 4 In this case, the cover 10 and the base 20 may be omitted. Similarly, the insert shown in Figure 3 may be directly welded to the outer wall 102 and to the inner wall 104.
In cases where sheet-metal inserts are used as cover and base, it may be of advantage to join the inserts 30, 40~ 130i~to them by spot welding. In many cases, howe~erg it is also sufficient to fix the inserts 30, 40 and 130)l~0 through the flanged ends 15, 25 and 115t~f the outer ~all 2 and 102.
During extrusion, the insert at the front end of the capsule leads to a type of tunnel effect providing it is made of a ductile material~ for example ductile iron, soft iron, low-alloyed carbon steel or cast iron. The 20 pressure required in the container of the extrusion press ~ ~-for extruding the pressing is reduced where the front insert consists of ductile material wh~ch can be made to flow more easily than the powder filling of the pressing.
Once the flow process taking place during extrusion has 25 started, it also affects the powder filling~ even when I -~
the yield point of the powder filling is higher than the yield point of the ductile material of the insert.
Accordingly, a type of tunnel effect is obtalned.
,' , , - ~ . . ...
s 1 In Figure 3, the outer ~all 102 comprises a bulge 103 which is directed against the shrinkage occurring during cold isostatic pressing. In Figure 3, the insert 140 also has a substantially arcuate cross-section 146 at the base 120 of the capsule. In the region of the central bore 142, this substantially arcuate cross-section merges into the wall of the bore 142 via a rounded region 149. Externally the insert 140 has a substantially cylindrical section 147 with which a cylindrical section 127 of the base 120 comes into contact. The cylindrical section 127 is welded at 126 to a substantially cylindrical section 166 of the ~ -outer ~all 102. The cover 120 rests on the inner wall 104 at its cylindrical section 129 and is welded to the inner wall àt 128. The outer end 144 of the insert 140 is flat, being rounded off or bevelled at its outer edge at 145 so that the flang~d lower edge 125 of the outer wall 102 is able firmly to hold the insert 1~0. The dimensions of -`
the bulge 103 are such that, after cold isos~atic pressing9 the lnner surface of the outer wall 102 contracts up to the line 170 ~h;ch corresponds to the ideal cylindrical form. Accordingly, the cylindrlcal sections 156 and 166 of the outer wall 102 are also drawn in, preferably by rolling, : :
until they are in alignment with the line 170.
In order to pre~ent crease foxmation and to ohtain an accurately ~entered pressing, it is of advantage in accordance with the invention to confine the change in :
diameter of the outer wall 102 subs~antially to the region of the inserts 130 and 1400 Between these inserts, the outer wall 102 has a substantially constant external diameter in the region shown at 150. It has proved to be ofparticular advantage for the cylindrical sections 156 9 166 to be. 7 adjoined towards the middle of the capsule by regions~ and 167
Said German printed application DE-AS 24 19 014 relates to a process for the~production of tubes of stainless steel having a uniform structure~ uniform physical and chemical properties and good urther processing properties, in which powder-form steel of the type in question is introduced into metallic capsules; the capsules are closed and compressed by a pressure actin~ on all sides thereof and the pressing obtained is extruded into tubes, steel powder of predominantly spherical particles produced by sputtering or atomizing melt in an inert gas atmosphere being used and the capsules used being thin~walled capsules of a.
ductile metal ha~ing a ma~i~um wall thickness corresponding to approximately 5 % of the external diameter of the capsule;
the density of the steel powder introduced into the capsule is increased to between about 60 ~nd 70 % of the --theoretical density by vibration and/or ultrasound; the density of the steel powder is increased to a~ least 80 %
and pre~erably to between ~0 % a~d 92 % of the theoretical density by isostatic cold pressing of the capsule under a pressure of at least 1500 bars; the pressing is heated ~nd subsequently hot-extruded, preferably at temperatures of at least about 1200~C5 to form the required semi-finished product.
According to the German printed application DE-AS 24 19 014 it can be of advantage to evacuate the metallic capsules filled with the steel powder before they .' , ~.
~26~0~5 1 are closed and/or to fill the~ ~ith a gas, particularly an inert gas, for example argon, In addition, according to the German printed application DE-AS 24 19 014, it is preferred to use metallic capsules of which the wall thicl;ness amounts to less than 3 % and more particularly to less than 1 % of the external diameter of the capsule, metallic capsules ha~in~ a wall thiclcness of from about 0.1 to 5 mm and preferably from about 0.2 to 3 mm being particularly preferred.
Using the process according to said German ~rinted application DE-~S 24 19 014, it is also possible to produce composite tubes using thin-walled metallic capsules which are separated by one or more concentric partitions into two or more compartments. The predominantly spherical powder particles of the various steel qualities are respectivellJ introduced under vibration into one of these compartments, after which the partitions are removed and the capsules closed, followed by isostatic cold pressing and extrusion at elevated temperature~ For extruding the pressings into tubes, glass is normally used as the lubricant. Since stringent demands are imposed on the lubricant in the extrusion of 9 in particular, stainless steels at elevated temperatures, the pressing is required to have a substantially flat end face so that the lubricant applied to the end face of the pressing in the form of a gLass disc is effectively utilis ed.
It has now been found that extrusion is accompanied by the development of surface faults in the front part of the extruded product on account of the fact that the flow pattern in the transition between the cover and the jacket is seriously disturbed through the disturbing effect of welding. This causes significan~ losses in the yield of end produc~.
V~3~
The object of the present invention is to increase the yield, i.e.
to reduce the percentage of defective products after extrusion.
The invention provides a capsule for producing a pressing for use in extrusion of a dense metallic tube said capsule comprising a tubular thin-walled sheet metal container having an inner and outer wall and a space therebetween of annular cross-section to be filled with powder of metal or metal alloys or mixtures thereof or with mixtures of powders of metals and/or metal alloys with ceramic powders9 and having inserts for closing each of its opposite ends~ at least said outer wall of the capsule being provided with a bulge which is directed outwards and against the direction in which shrinkage will occur during subsequent isostatic pressing, the dimensions of said bulge being selected such that said bulge will be substantially eliminated by said shrinkage.
From another aspect, the invention provides a process for forming a capsule for producing a pressing for use in extrusion of a dense metallic tube, said process comprising providing a tubular, thin-walled, sheet metal container, said container having an inner and an outer peripheral wall;
reducing the diameter of opposite end portions of the outer peripheral wall, so that intermediate those end portions said outer peripheral wall defines a bulge which is directed outwards against the direction of shrinkage which will occur during subsequent isostatic pressing, the dimensions of said bulge being selected such that it will be substantially eliminated by such shrink-age, and providing inserts for closing the opposite ends of said container.
The construction of the capsule according to the invention affords the advantage that, after the cold isostatic pressing of the capsule, the pressing is not in the form of a "sand glass" with a central constriction.
In many cases, this so-called "sand glass" form arises out of the fact that the ends of the capsule, which are closed by covers or the like, undergo less shrinkage during cold isostatic pressing than the central part of the capsule.
Since a pressing having a substantially cylindrically outer wall is required for extrusion, the ends of the pressing have to be trimmed where it is in the form of a "sand glass", which is not only a very expensive operation, but also i~ ` A
~ 5 -involves the danger of cracks being formed. The construction of the capsule according to the invention affords the advantage that there is no longer any need for the pressing to be trimmed to make it cylindrical. In addition, it is possible by the invention to obtain pressings of which the diameters exactly correspond to the required diameters. According to the invention, it is possible to obtain accuracies of + 0.2 % and, more particularly, of + 0.1 %. In other words, the pressings can be produced with absolute diameters accurate to + 0.2 mm and more particularly to + 0.1 mm.
The outer wall and/or inner wall of the capsule according -- Sa -' , , ~ , , ' ~ : , s 1 to the invention are preferably produced in the form of substantially cylindrical sections at the ends of the capsule, the diameters of ~hich exactly correspond to those of the required pressing and which steadily merge into a bulged, S central region of the capsule.
According to the invention, the outer and/or inner ~all of~the capsule is/are ad~Jantageously shaped in such a way that, from each of the cylindrical sections at the ends of the capsule, the bulge gradually and steadily increases in the axial direction (looking towards the middle of the capsule) initially in a region having an ou~ardly concave cross section~ the inclination of the outer and/or inner ~all relatively to the axis of the capsule also gradually and steadily increasing, followed preferably by a conical intermediate region in which the inclination of the outer and/or inner wall remains substantially constant, this conical intermediate region being followed by a region in which the outer and/or inner wall has an outwardly convex cross-section and gradually and steadily merges into an axially parallel central section which preferably has a substantially constant diameter.
According to the invention, it is also possible to improve the dimensional accuracy of the pressing and to reduce the number of rejects by arranging a plate-shaped, conical, hemispherical or funnel-shaped insert of solid material at the front and/or rear end of the capsule.
The provision of inserts such as these considerably improves the flow properties during extrusion of the pressing and increases the yield of stainless material bec~use the inserts ~ich preferably consist of an electrically Cc~ G~
co~uct~ material, preferably soft iron or a low carbon sof~ steel, form the ends of the extruded tubes which have to be cut off ~2c~ 5 1 in any case In addition, the presence of the inserts preferably consisting of an electrically ~ metal at the front and/or rear end of the capsule makes the pressing much easier to heat by induction before extrusion because the metallic inserts may readily be treated by induction and give off their heat to the remaining parts of the pressing, particularly to the powder-filled interior thereof, thus contributing towards the rapid heating of the pressing as a whole.
It has proved to be of particular advantage to combine the provision of the above-mentioned-inserts at the front and/or rear end of the capsule with the provision in the outer and/or inner wall of the capsule of a bulge which is directed outwards and against the shrinkage occurring during isostatic pressing and of which the dimensions are such that it is substantially eliminated again by the shrinkage effect.
According to the invention, this combination enables the dimensions of the pressing tv be kept considerably more accurate. In particular, it is possible to keep the dimensions of the pressing accurate to ~ 0.05 % or, in absolute terms7 accurate to ~ 001 mm or more~ which is of considerable importance for the fault-free production of extruded articles, particularly extruded tubes.
According to the invention, the inserts may be in the 25 form of covers ~hich close the capsule at its ends and may ~
be tightly welded to the outer and inner ~alls of the capsule. ~-Sheet metal inserts in the oxm of covers may with advant~ge also be provided between the inserts ~nd the interior of the capsules and may be tightly welded to the outer and inner walls.
According to the invention, it is possible in the case of capsules for the production of pressings for extruding ~Z6~
1 tubes to use funnel-shaped, centrally bored inserts for the front end face of the capsules, the angle ~ between the ~all of the central bore for the inner wall of the capsule and the conical outer surface of the funnel-shaped insert amounting to between about 40 and 609 preferably to between about 40 and 50 and, more particularly, to about 45.
According to the invention, it can be of advantage in the production of tubes to provide at least on the front end of the capsule a centrally bored annular insert which _ 9 _ 1 has a substantially flat end surface and of which the boundary suxface between the wall of the cen~ral bore and its largest diameter has a substantially f3rcuate cross-.~ectional profile, the centre of the arcuate profile lying substantially in the vicinity of the intersecting line between the flat end face and the central bore.
According to the invention9 Enother significant improvement in the capsules and the pressings and ex~ruded articles, particularly extruded tubes, produced from them9 may be obtained in combination with or independently of the above described inserts constructed in accordance with the inve~tion by ensuring that at least the outer wall of the capsule has substantially the same strength properties ~
in the axial direction over its entire circumference. ~ -According to the invention, at least the outer wall of the capsule is preferably ~ormed by a thin-~alled, spiral ~elded or extruded tube. Forming the outer wall of the capsule in this way affords the advantage that extruded products~
particularly tub s, characterised by a considerably reduced number of ~aults and~ hence~ rejects are obtained.
The pitch of the spiral formed by the weld seam in relation to the length of the capsule is preferably such that the weld seam approximately forms one complete turn.
An outer wall provided with a weld seam such as this has only one weld seam at any point along its circumference in the axial direction and, therefore~ shows substantially the same strength properties in the axial direction.
Alternatively, the weld seam may form two, three or more complete turns.
The present invention is appli~ble ~o capsules and pressings for extruding objects, particularly tubes J bars or similarly profiled, elongate, dense metalli~ objects, 20(?~5 _ 10-1 particularly of stainless steel or highly alloyed nickel steels, particularly heat~resistant steels for heat exchangers, for example highly alloyed nickel steels containing approximately 80 % of nickel and 20 % of chromium, powder S of metal or metal alloys or mixtures thereof or mixtures of powders of metals and/or metal alloys with cerami~ powders beingintroduced into the capsule according to the invention.
The powder used is preferablyspherical or predominantly spherical powder having a mean particle diameter of preferably less than 1 mm. According to the invention7 ;t is preferred to use spherical powder which has been produced from the required starting material, i.e. the re~uired metal and/or metal alloy, by sputtering in an inert gas atmosphere, preferably an argon atmosphere.
Powder particles larger than 1 mm in diameter are preferably separated out, at least to a predominant extent, because argon is in danger of being included into powder particles larger than 1 mm in diameter. An inclusion of argon such as this can oc~ur during sput~ering, for example through turbuIence. Any incluslon of argon w~uld give rise during extrusion to un~avourable properties of the extruded articles and would lead to inclusion lines~
According to the invention, the capsule used for producing the pressings for the tubes to be extruded is filled with the powder~ the density of the powder introduced into the capsule being increased by vibration to between about 60 and 71 % o the theoretical density and the frequency of the vibration preferably amounting to at least about 70 Hz and advantageously to between 80 and 100 Hz. By vibration at a frequency of from 80 to 100 Hz, it is possible to obtain a density o~ from about 68 to 71 % of the theoretical density.
1 After the powder has bPen introduced and compacted by vibration9 the capsule is ~losed, preferably after evacuation and/or filling with an inert gas. Thereafter the density of the powder is increased to at least 80 to 93 % of the theoretical density by isostatic cold pressing under a pressure of at least 4000 bars, preferably under a pressure of from 4200 to 6000 bars and, more particularly, under a pressure of from 4500 to 5000 bars.
Capsules of thin sheet steel9 preferably about 1 to 2 mm thick sheet steel and, more particularly, approximately 1.5 m6n~ick sheet steel~ have prc~ved to particularly advantageous.
The material used for these capsules is preferably low-carbon soft steel, particularly steel having a carbon content of less than 0.015 ~/O and, better still, less than 0.004 % in order to prevent the powder from carburising during heating and extrusion.
Under the effect of the pressure applied on all sides during cold isostatic pressing, the capsule is uniformly compressed both in the longitudinal and in the radial direction and t~us forms a pressing. This pressing should h~ve no irregularities because this ~ould give rise to difficulties during extrusion~ particularly during the extrusion of tubes.
In order to produce a pressing for extruding a tube, an annular capsule is used, the outer wall of this annular capsule being ~ormed by a spiral-welded tube sectionproduced for example ~rom an approx;mately 1.5 mm thick sheet.
An inner wall, for example in the fo~m of a iongitudinally welded tube sectîon9 is introduced into the interior of the outer wall, ha~ing a smaller diameter than but the same wall thickness as the outer wall~ An annular cover is then ~ixed between the outer wall and the inner wall a~ one end ~Z~ 5 1 and the annular space between the two tubes is thus closed at one end. Spherical powder is then introduced into the an~ular space and compacted to around 68 % of the theoretical density by vibration at a ~requency of, for example~ 80 Hz.
A vacuum is then applied and the other end of the annular body is sealed off by a corresponding second cover. This is followed by cold isostatic pressîng in a liquid, for example water, under a pressure of9 for example~ 4700 bars.
Under the effect of the pressure applied on all sides, a pressing having a density of 9 for exampleg 85 % of the theoretical density is obtained.
In the capsule according to the invention, the spiral weld searn is required to be as smooth as possible with as --little effect as possible on the properties of the sheet steel. Accordingly, the weld se~m is preferably smoothed by rclling and/or grinding. The smoothing of the weld seam by rolling may be carried out immediately after welding.
In the case of capsules for the production of ~ubes, it can be of advantage to produce not only the ou~er wall, but also the inner wall from a tube wh;ch has substantially the same strength properties in the axial direction along its circumference. In this case, the inner wall may consist either of a spiral-welded tube or of an extruded tube. The use of an extruded or spiral-welded tube for the inner wall is particularly advisable in the production of large tubes.
In the production of smaller tu~es, it is generally sufficient in accordance with the invention for the outer wall of the capsule to be produced from a tube section which has substantially the same strength properties in the axial direction along its circumference.
An embodiment of the invention is described by way of example in the following with reference to the accompanying ~2~
1 diagrammatic dra~ings, wherein:
Figure 1 is an elevation of a capsule open at its upper end~
Figure 2 is a longitudina1 section through 8 modified embodiment of the capsule.
Figures3 to 6 are partial sections through other embodiments.
In Figure 1, the capsule is generally denoted by the reference 1~ ~he capsule has an outer wall 2 and inner wall 4. ~he outer wall 2 consists of a spiral-welded tube section ha~ing a length L. The weld seam 5 extends spirally over the circumference of the outer wall 2, the spiral having a helix angle a such that the spiral orms approximately one complete turn.
It has been found to be of advantage to arrange the weld seam 5 in such a way that it forms one complete turn between the weld seam 16, which is used to weld the cover (not shown in Figure 1) of the capsule firmly to the outer wall 2, and the weld seam 26 by means of which the base of the capsule is joined to the outer wall. The distance between the weld seams 16 and 26 is denoted by the reference L~ in Figure 1~ This length Ll may be regarded as the effecti~e length of the oapsule. It is advisable to select the helix angle a of the spiral weld in such a way that tg ~ ~ L
n Otr O D
where D is the diameter of the c~psule and n the number of turns ~ich the spiral weld seam 5 is required to oomprise.
- It has been found to be advi~a~le for n to have a value of 1, However, it may also be of advantage for n ~o have a value of 2,3~4 or to be equal to a larger whole n~mber.
In one practical example, the outer wall 2 and also the 1 inner wall 4 o~ the capsule 1 consisted of 115 mm thick soft sheet steel having a carbon content of less than 0.004 %.
The cover, which is not shown in Figure 1,was welded in along the weld seam 16. To produce the pressing, powder which consisted predominantly of spherical particles having a mean diameter of less than 1 mm and ~lich had been produced from the required starting material, for example stainless steel9 by sputtering in an argon atmosphere, was introduced into the capsule, After it had been introduced into the ~apsule, the powder was compacted to a density of, for example~
approximately 68 % of the theoretical density by vibration at a frequency of, for example, 80 Hz. The capsule was then evacuated and closed by means of a cover~ The cover was directly joined to the outer wall 2 of the capsule by welding substantially along the line 16 in Figure 1. - In the example in question7 the capsule had a len~th of 60Q mm and an external diameter of 150 mm The internal diameter of the inner wall 4 was approximately 55 mm. The inner wall 4 consisted of a longitudinally welded tube section with a longitudinal weld seam 6. The powder was then compressed for example to around 88 /~ of the theoretical density by cold isostati~ pressing under a pressure of, for example, 4700 ~ars, ~he pressing thus obtained was extruded into a tube a~ described in said German printed application DE-AS 24 19 014.
In the embodiment illustrated in Figure 2, inserts 30 and 40 are arranged in the region of the cover 10 and the base 20, fonming the front and rear end face, respectively, of the capsule. The front insert 30 is generally conical and comprises a central bore 32 for receiving the inner wall 4 of the capsule. The conical surface 36 of the conical or funnel-shaped insert 30 fonms wi~h the wall of the bore 32 1 an angle ~ ~hich is preferably in the range from about 40 to 60, advantageously in the range from about 40 to ~bout 50 and, more particularly, of the order of 45~.
The insert 30 comprises a substantially flat end face 34.
However, it is bevelled or rounded off at its outer edge (at 35) and then comprises a cylindrical section 37 which merges into the conical surface 36. The transition from the conical surface 36 to the wall of the central bore 32 is rounded off at 39. The cover 10 in the form of a sheet-metal insert corresponds exactly in its contour to the adjbining parts of the insert 30. More particularly, the co~er 10 comprises along its outer edge a cylindric~l section 17 which provides for firm contact between the cover 10 and the outer wall 2, the outer edge of this cylindrical sec~ion 17 being joined to the outer wall 2 by means of a weld seam 16. In its inner region, too, the cover 10 comprises a short, substantially cylindrical section 19 which is in contact with the inner wall 4 of the capsule and w~ich is tightly welded to the i~ner wall 4 `
at .18 by means of a weld seam. The cover 10 also comprises a rounding-off corresponding to the rounding-off 39 of the insert 30.
Arranged at the rear end of the c~psule 1 is an insert 40 in the form of a substantially flat plate which comprises a central bore 42 ~nd an outwardly directed ~nd face 44.
This plate-like insert 40 is also bevelled or rounded o~
at its edge (at 45) and comprises an outer cylindrical section 47. The base 20 of the capsule corresponds in shape to the shape of the insert 40 and also comprises an ou~er cylindrical section 27 and an inner cylindrical section 29~ The base 20 is tigh~ly welded to the outer wall 2 and the inner ~all 4 by means o weld seams 26 and 28, o~
respectively. The inserts 30 and 40 preferably consist of soft iron or low carbon soft steel.
Figure 3 shows a modified embodiment of the capsule in which an insert 130 provided at the front end of the capsule 5 comprises a substantially arcuate cross-s~ctional profile 136, a flat end face 134 and a central bore 132. The centre of the arcuate cross-sectional profile 136 are situated on a circle substantially in the ViCiTlity of the intersecting line between the flat end face 134 and the wall of the 10 bore 132) i.e. in the region of the front boundary line of the bore 132. This circle is indicated by two crosses at 138 in Fig. 3. The substantially arcuate cross-sectlonal profile 136 affords the advantage that, during extrusion of the pressing, the insert 130 consisting of soft iron or 15 a similar metal,, together with the cover 110, the weld seams 116, 118 ~nd the adjacent parts of the outer wall 102 and the inner wall 104, forms the first part of the ~ube ~ich is cut off or even drops off automatically after extrusion if the connection to the following tube preferably consisting 20 of stainless s~eel and produced from the powder filling of ~he capsule lacks sufficient strength. The effect of the substantially arcuate shape o che boundary llne 136 of ~hP
insert 130 is ~hat the d;viding line between the front part of the extruded tube, which acc~nulates as waste, and the 25 a~tual tube consisting of high quality stainless steel is clearly defined and is in the form of a separation surface extending substantially perpendicularly of the longitudinal axis o the tube. The cover 110 also comprises a substantially cylindrical section 117 which is welded at 30 116 to the outer wall 102 of the capsule7 and a substantially cylindrical inner section 119 ~ich is in contact with the inner wall 104 and w~ich is tightly welded to the inner wall .
l~LZ¢)~5 - 17 _ 1 at 118 by means of an encircling weld seam~ The transition from the wall of the central bore 132 to the circular cross-sectional profile 136 is rounded of~ at 139.
It can also be of advantage for the inserts 30 and 40 to be directly welded to the outer wall 2 and the inner ~all 4 In this case, the cover 10 and the base 20 may be omitted. Similarly, the insert shown in Figure 3 may be directly welded to the outer wall 102 and to the inner wall 104.
In cases where sheet-metal inserts are used as cover and base, it may be of advantage to join the inserts 30, 40~ 130i~to them by spot welding. In many cases, howe~erg it is also sufficient to fix the inserts 30, 40 and 130)l~0 through the flanged ends 15, 25 and 115t~f the outer ~all 2 and 102.
During extrusion, the insert at the front end of the capsule leads to a type of tunnel effect providing it is made of a ductile material~ for example ductile iron, soft iron, low-alloyed carbon steel or cast iron. The 20 pressure required in the container of the extrusion press ~ ~-for extruding the pressing is reduced where the front insert consists of ductile material wh~ch can be made to flow more easily than the powder filling of the pressing.
Once the flow process taking place during extrusion has 25 started, it also affects the powder filling~ even when I -~
the yield point of the powder filling is higher than the yield point of the ductile material of the insert.
Accordingly, a type of tunnel effect is obtalned.
,' , , - ~ . . ...
s 1 In Figure 3, the outer ~all 102 comprises a bulge 103 which is directed against the shrinkage occurring during cold isostatic pressing. In Figure 3, the insert 140 also has a substantially arcuate cross-section 146 at the base 120 of the capsule. In the region of the central bore 142, this substantially arcuate cross-section merges into the wall of the bore 142 via a rounded region 149. Externally the insert 140 has a substantially cylindrical section 147 with which a cylindrical section 127 of the base 120 comes into contact. The cylindrical section 127 is welded at 126 to a substantially cylindrical section 166 of the ~ -outer ~all 102. The cover 120 rests on the inner wall 104 at its cylindrical section 129 and is welded to the inner wall àt 128. The outer end 144 of the insert 140 is flat, being rounded off or bevelled at its outer edge at 145 so that the flang~d lower edge 125 of the outer wall 102 is able firmly to hold the insert 1~0. The dimensions of -`
the bulge 103 are such that, after cold isos~atic pressing9 the lnner surface of the outer wall 102 contracts up to the line 170 ~h;ch corresponds to the ideal cylindrical form. Accordingly, the cylindrlcal sections 156 and 166 of the outer wall 102 are also drawn in, preferably by rolling, : :
until they are in alignment with the line 170.
In order to pre~ent crease foxmation and to ohtain an accurately ~entered pressing, it is of advantage in accordance with the invention to confine the change in :
diameter of the outer wall 102 subs~antially to the region of the inserts 130 and 1400 Between these inserts, the outer wall 102 has a substantially constant external diameter in the region shown at 150. It has proved to be ofparticular advantage for the cylindrical sections 156 9 166 to be. 7 adjoined towards the middle of the capsule by regions~ and 167
2~
~ 19 -1 having an outwardly concave cross-section and for these regions to be followed by frustoconical intermediate regions ~58 and 168 which are in turn followed by regions 159, 169 which have an outwardly convex cross-section and merge into th~ cylindrical~ axially parallel central region 150. It is essential for the outwardly concave regions 157 and 167 to be virtual mirror images of the cross-sectional profiles 136 and 1~6 of the inserts, the line 170 representing the mirror symmetry axis and the angle of curvature of the outer wall indicated at ~ being reduced substantially commensurately with the percentage shrinkage to-the angle of curvature of the adjacent insert.
Figure 4 shows a modified embodiment similar to Figure 3 in which all identical or similar components are denoted by reference numerals increased by 100~ The main difference lies in the fact that the inserts 230 and 240 have a substantially pointed cross-sectional profile at 239 and 249, respectively, so that the correspondingly shaped cover 210 and the correspondingly shaped base 209 20 extend right up to the inner wall 204 and form obtuse `
angles a and a~ therewith~ It has been found that this ~ ~ c~
configuration is advantageous for exactly ~e*~g ~he pressing. In the em~odiment sho~n in Figure 4, the inner wall 204 does not have to be provided with a bulge whereas, in the embodiment sho~m in Figure 3, it can be of advantage to provide the inner wall with a slight outwardly directed bulge~ According to the invention, it c~n be of advantage to provide the outer and~or inner wall with a bulge in conjunction with inserts of any shape.
It can also be of advantage to combine the bulge with a spirally welded outer and/or inner tube.
Figure 5 shows a modified embodiment similiar to 1 Figure 4 in whicll all identical or similar components are denoted by reference numera ls încreased by 100. The main difference lies in the fact that the insert 330 ~nd 340 are provided with points 339 and 349 and that no sheet metal S liners are provided. From each of the cylindrical sections 356, 366, the bulge 303 increases gradually and steadily in the axial direction, looking towards the middle of the capsule, initially in a region 357y 367 having a concave cross-section9 the inclination of the outer wall 302 relatively to the axis of the capsule also increasing gradually and steadily. Thereafter, the inclin ation of the outer wall 302 remains substantially constant via a conical intermediate region 358, 368, followed by a region 359, 369 in ~hich the outer wall 302 has an out~ardly convex cross-sectional profile and merges gradually and steadily into an &Yially parallel central region 350. lhose regions of the outer wall 302 which have a changing cross-section each form a transitional region 355, 365 which is situated in the region o~ an insert 330 or 340. The cross-section 336, 346 of the insert 3307 340 is a virtual mirror image of the contour of the outer wall in the transitional regions 355, 365 which is reflected at the line 370 o~ the required cylindrical fonm of the pressing, but extended in the radial direction, the de~ree of extension substantially corresponding to the ratio of the difference between the e~ternal and internal diameters of the pressing to ~he reduction in diameter of the capsule, preferably taking into account the change in the cross-sectional area with decreasing radius.
The insert 330 and 340 are tightly welded to the outer and inner walls at 316, 3187 326 and 328 337 and 347 are ~ylindrical sections o~ the inserts 330 and 340 ~hich correspond to the cylindrical sections 137, 147 and 237, 247 ~z~
1 of Figures 3 and 4.
EXA~LE
To produ.ce a pressing having an external diameter of 144 mm for e~truding a tube of stainless ~eel having an S external diameter of S0 mm and a wall thiclcness of 5 mm, a spirall~r welded 600 mm long tube having an external diameter o~ 154 mm and wall thicl;ness of 1.5 mm, used as the outer wall for the capsule, was necked at its two ~ ends by rolling or pinching in such a way that c~t~lnri~
sections having an e~ternal diameter of 1~ mm, corresponding to the sections 1569 166; 256,266; 356, 366 in Figures 3 to 4, were present at the ends~ being adjoined by transitional regions formed in accordance with the transitional regions 155, 165; 255, 265; 355, 365. The ends of the outer wall were then ground flat. At a f~ end, a sheet metal insert forming a base, similar to the insert 120 in Figure 3, was tightly welded on the one hand to the outer wall and, on the other hand, to an inner wall which consisted of a 590 mm long longi~udinally welded tube having a ~all thickness of 1~5 mm and an internal diameter of 40 mm.
An annular or funnel-shaped insert similar to the insert 140 consisting of low-alloyed carbon steel containing approximately 0.004 % of carbon was then inserted from the above-mentioned front end of the outer wall up to the ~-base sheet to which i~ was fixed by spot welding6The capsule was placed vertically on a plate, filled with powder, vibrated at 80 Hz, compacted to around 68 % of the theoretical density and, at the same time, provided ~th a funnel-shaped sheet-metal insert similar to 110 in Figure 3 acting as cover which was inserted under high pressure from above between the inner and outer ~alls. The sheet metal insert w~s then tightly welded to the inner and outer walls, as shown 1 at 116 and 118 in Figure 3. The front annular or funnel-shaped insert similar to 130 in Figure 3 and consisting of lo~ alloyed carbon steel containing approximately 0.004 %
of carbon was then inserted from a~ove. This annular insert ~as advantageously spot-welded to the funnel-shaped sheet metal insert or to the inner or outer wall.
The capsule was the subjected to cold isostatic pressing (4700 bars) in water to a density of 88 % of the theoretical density. The pressing contracted to an external diameter of 144 mm, i.e. to the same diameter as the dra~n-in cylindrical sections at its ends. ~e diameter of 1~4 mm also corresponded to the internal diameter of the container of the extrusion press. Perfect c~ntr~g ~ s thus guaranteed. ¦
In addition, the internal diameter of the pressing wasalmost exactly ~0 mm. Moreover, the pressing was also completely straight and, after inductive heating to 1200C, could be directly extruded to form the required stainless and seamless tube without any need for further machining operations.
The front section of the tube consisting of low-alloyed carbon steel was cut off. None of the stainless was cut off. By virtue of the fact that the insert is conical, a substantially ~ertical (relative to the tube ~is) parting line between the extruded insert and the stainless steel w~s obtained in the extruded tube. That part o~ th e tube ~lich consisted o stainl~ss material had a fault-free surface. In this way, the loss o material was reduced to a minimum.
All the particulars and features disclosed in the documents, particularly the spatial con~iguration disclosed, are claimed as being essen~ial to the invention where they are new either individually or in combination in relation to the prior art.
~26~0~5i In order to obtain good separation between the front section of the extruded tube, which consists of a low alloy carbon steel, and the desired seamless tube of stainless steel, a layer of glass can according to the invention be applied to the front insert at the surface facing the powder Eilling 308. It can be suitable for this purpose to heat the front inser~ member 330 and to sprinkle glass powder onto the surface 336, the temperature of the insert mem- -ber 330 being selected so that the glass powder becomes soft and adheres. By such an intermediate layer of glass, the SepaTation between the low alloy carbon steel and the stainless steel is made very much easier when the extruded tube is obtained so that the two steel grades are obtained completely separately from each other and without mixing. -Analogously, also the surface,which is adjacent to the powder filling 308, of the insert member 340 on the bottom of the tube may be provided with a layer of glass facili-tating a separation of the stainless steel material and the low alloy carbon steel.
The insert members 30, 40, 130, 140, 230, 240, 330, and 340 ~ ~-can also be pressed from powder material. For this purpose, for example powder obtained by water-atomizing soft iron or water-atomizing low-carbon steel can be used, which powder is subjected to isostatic cold pressing ~o the desired shape of the aforementioned insert members and ~2~
subsequently to sintering. Cold isostatic pressing of the soft iron powder can take place in a plastic mould, the pressure being ~ selected at least as high if not higher than the pressure for cold isostatic pressing which is applied to the aforementioned capsules~
By subsequent hot sintering, a dense material can be ob-tained. Alternatively or additionally, in this case also a sealing can be obtained at the front end faces 34, 134, 234, 334 and 44, respectively, 144, 244, and 344 as well as onto the circumferential surfaces by applying an outer layer of glass thereon.
The embodiment according to Fig. 6 corresponds extensively to the embodiment according to Fig. 5. Only the insert members have a modified shape. The front insert 330' comprises two rings 380 and 381 held together by several -spot weldings 382. Instead of two rings 380, 381, of course three or more rings can also be provided, whereby the outer contour of such rings constitute an approximation to the ideal contour of the front insert member which is - -determined by the curve 336 in Fig. 5 and the arcuate cross-section 236 in Fig. 4 9 and 136 in Fig. 3, respec-tively~ In the embodiment according to Fig. 6 9 the insert 340' at the bottom end of the capsule consists of an annular plate. ~lso here, if desired, additional rings having a stepwise increasing or decreasing outer diameter and/or inner diameter can be provided in order to achieve s that the insert 340' constitutes an approximation to the desired ideal profile, ~or example the profile 346 according to Fig. 5.
All particulars and features disclosed in the documents, particularly the spatial configuration disclosed, are ;.
claimed as being essential to the invention where they are new either individually or in combination in relation to the prior art.
' ~' , ~,
~ 19 -1 having an outwardly concave cross-section and for these regions to be followed by frustoconical intermediate regions ~58 and 168 which are in turn followed by regions 159, 169 which have an outwardly convex cross-section and merge into th~ cylindrical~ axially parallel central region 150. It is essential for the outwardly concave regions 157 and 167 to be virtual mirror images of the cross-sectional profiles 136 and 1~6 of the inserts, the line 170 representing the mirror symmetry axis and the angle of curvature of the outer wall indicated at ~ being reduced substantially commensurately with the percentage shrinkage to-the angle of curvature of the adjacent insert.
Figure 4 shows a modified embodiment similar to Figure 3 in which all identical or similar components are denoted by reference numerals increased by 100~ The main difference lies in the fact that the inserts 230 and 240 have a substantially pointed cross-sectional profile at 239 and 249, respectively, so that the correspondingly shaped cover 210 and the correspondingly shaped base 209 20 extend right up to the inner wall 204 and form obtuse `
angles a and a~ therewith~ It has been found that this ~ ~ c~
configuration is advantageous for exactly ~e*~g ~he pressing. In the em~odiment sho~n in Figure 4, the inner wall 204 does not have to be provided with a bulge whereas, in the embodiment sho~m in Figure 3, it can be of advantage to provide the inner wall with a slight outwardly directed bulge~ According to the invention, it c~n be of advantage to provide the outer and~or inner wall with a bulge in conjunction with inserts of any shape.
It can also be of advantage to combine the bulge with a spirally welded outer and/or inner tube.
Figure 5 shows a modified embodiment similiar to 1 Figure 4 in whicll all identical or similar components are denoted by reference numera ls încreased by 100. The main difference lies in the fact that the insert 330 ~nd 340 are provided with points 339 and 349 and that no sheet metal S liners are provided. From each of the cylindrical sections 356, 366, the bulge 303 increases gradually and steadily in the axial direction, looking towards the middle of the capsule, initially in a region 357y 367 having a concave cross-section9 the inclination of the outer wall 302 relatively to the axis of the capsule also increasing gradually and steadily. Thereafter, the inclin ation of the outer wall 302 remains substantially constant via a conical intermediate region 358, 368, followed by a region 359, 369 in ~hich the outer wall 302 has an out~ardly convex cross-sectional profile and merges gradually and steadily into an &Yially parallel central region 350. lhose regions of the outer wall 302 which have a changing cross-section each form a transitional region 355, 365 which is situated in the region o~ an insert 330 or 340. The cross-section 336, 346 of the insert 3307 340 is a virtual mirror image of the contour of the outer wall in the transitional regions 355, 365 which is reflected at the line 370 o~ the required cylindrical fonm of the pressing, but extended in the radial direction, the de~ree of extension substantially corresponding to the ratio of the difference between the e~ternal and internal diameters of the pressing to ~he reduction in diameter of the capsule, preferably taking into account the change in the cross-sectional area with decreasing radius.
The insert 330 and 340 are tightly welded to the outer and inner walls at 316, 3187 326 and 328 337 and 347 are ~ylindrical sections o~ the inserts 330 and 340 ~hich correspond to the cylindrical sections 137, 147 and 237, 247 ~z~
1 of Figures 3 and 4.
EXA~LE
To produ.ce a pressing having an external diameter of 144 mm for e~truding a tube of stainless ~eel having an S external diameter of S0 mm and a wall thiclcness of 5 mm, a spirall~r welded 600 mm long tube having an external diameter o~ 154 mm and wall thicl;ness of 1.5 mm, used as the outer wall for the capsule, was necked at its two ~ ends by rolling or pinching in such a way that c~t~lnri~
sections having an e~ternal diameter of 1~ mm, corresponding to the sections 1569 166; 256,266; 356, 366 in Figures 3 to 4, were present at the ends~ being adjoined by transitional regions formed in accordance with the transitional regions 155, 165; 255, 265; 355, 365. The ends of the outer wall were then ground flat. At a f~ end, a sheet metal insert forming a base, similar to the insert 120 in Figure 3, was tightly welded on the one hand to the outer wall and, on the other hand, to an inner wall which consisted of a 590 mm long longi~udinally welded tube having a ~all thickness of 1~5 mm and an internal diameter of 40 mm.
An annular or funnel-shaped insert similar to the insert 140 consisting of low-alloyed carbon steel containing approximately 0.004 % of carbon was then inserted from the above-mentioned front end of the outer wall up to the ~-base sheet to which i~ was fixed by spot welding6The capsule was placed vertically on a plate, filled with powder, vibrated at 80 Hz, compacted to around 68 % of the theoretical density and, at the same time, provided ~th a funnel-shaped sheet-metal insert similar to 110 in Figure 3 acting as cover which was inserted under high pressure from above between the inner and outer ~alls. The sheet metal insert w~s then tightly welded to the inner and outer walls, as shown 1 at 116 and 118 in Figure 3. The front annular or funnel-shaped insert similar to 130 in Figure 3 and consisting of lo~ alloyed carbon steel containing approximately 0.004 %
of carbon was then inserted from a~ove. This annular insert ~as advantageously spot-welded to the funnel-shaped sheet metal insert or to the inner or outer wall.
The capsule was the subjected to cold isostatic pressing (4700 bars) in water to a density of 88 % of the theoretical density. The pressing contracted to an external diameter of 144 mm, i.e. to the same diameter as the dra~n-in cylindrical sections at its ends. ~e diameter of 1~4 mm also corresponded to the internal diameter of the container of the extrusion press. Perfect c~ntr~g ~ s thus guaranteed. ¦
In addition, the internal diameter of the pressing wasalmost exactly ~0 mm. Moreover, the pressing was also completely straight and, after inductive heating to 1200C, could be directly extruded to form the required stainless and seamless tube without any need for further machining operations.
The front section of the tube consisting of low-alloyed carbon steel was cut off. None of the stainless was cut off. By virtue of the fact that the insert is conical, a substantially ~ertical (relative to the tube ~is) parting line between the extruded insert and the stainless steel w~s obtained in the extruded tube. That part o~ th e tube ~lich consisted o stainl~ss material had a fault-free surface. In this way, the loss o material was reduced to a minimum.
All the particulars and features disclosed in the documents, particularly the spatial con~iguration disclosed, are claimed as being essen~ial to the invention where they are new either individually or in combination in relation to the prior art.
~26~0~5i In order to obtain good separation between the front section of the extruded tube, which consists of a low alloy carbon steel, and the desired seamless tube of stainless steel, a layer of glass can according to the invention be applied to the front insert at the surface facing the powder Eilling 308. It can be suitable for this purpose to heat the front inser~ member 330 and to sprinkle glass powder onto the surface 336, the temperature of the insert mem- -ber 330 being selected so that the glass powder becomes soft and adheres. By such an intermediate layer of glass, the SepaTation between the low alloy carbon steel and the stainless steel is made very much easier when the extruded tube is obtained so that the two steel grades are obtained completely separately from each other and without mixing. -Analogously, also the surface,which is adjacent to the powder filling 308, of the insert member 340 on the bottom of the tube may be provided with a layer of glass facili-tating a separation of the stainless steel material and the low alloy carbon steel.
The insert members 30, 40, 130, 140, 230, 240, 330, and 340 ~ ~-can also be pressed from powder material. For this purpose, for example powder obtained by water-atomizing soft iron or water-atomizing low-carbon steel can be used, which powder is subjected to isostatic cold pressing ~o the desired shape of the aforementioned insert members and ~2~
subsequently to sintering. Cold isostatic pressing of the soft iron powder can take place in a plastic mould, the pressure being ~ selected at least as high if not higher than the pressure for cold isostatic pressing which is applied to the aforementioned capsules~
By subsequent hot sintering, a dense material can be ob-tained. Alternatively or additionally, in this case also a sealing can be obtained at the front end faces 34, 134, 234, 334 and 44, respectively, 144, 244, and 344 as well as onto the circumferential surfaces by applying an outer layer of glass thereon.
The embodiment according to Fig. 6 corresponds extensively to the embodiment according to Fig. 5. Only the insert members have a modified shape. The front insert 330' comprises two rings 380 and 381 held together by several -spot weldings 382. Instead of two rings 380, 381, of course three or more rings can also be provided, whereby the outer contour of such rings constitute an approximation to the ideal contour of the front insert member which is - -determined by the curve 336 in Fig. 5 and the arcuate cross-section 236 in Fig. 4 9 and 136 in Fig. 3, respec-tively~ In the embodiment according to Fig. 6 9 the insert 340' at the bottom end of the capsule consists of an annular plate. ~lso here, if desired, additional rings having a stepwise increasing or decreasing outer diameter and/or inner diameter can be provided in order to achieve s that the insert 340' constitutes an approximation to the desired ideal profile, ~or example the profile 346 according to Fig. 5.
All particulars and features disclosed in the documents, particularly the spatial configuration disclosed, are ;.
claimed as being essential to the invention where they are new either individually or in combination in relation to the prior art.
' ~' , ~,
Claims (31)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A capsule for producing a pressing for use in extrusion of a dense metallic tube said capsule comprising a tubular thin-walled sheet metal container having an inner and outer wall and a space therebetween of annular cross-section to be filled with powder of metal or metal alloys or mixtures thereof or with mixtures of powders of metals and/or metal alloys with ceramic powders, and having inserts for closing each of its opposite ends, at least said outer wall of the capsule being provided with a bulge which is directed outwards and against the direction in which shrinkage will occur during sub-sequent isostatic pressing, the dimensions of said bulge being selected such that said bulge will be substantially eliminated by said shrinkage.
2. A capsule as claimed in claim 1 wherein said outer peripheral wall is fabricated in low-carbon steel.
3. A capsule as claimed in claim 2 wherein said steel has a carbon content of less than 0.015%.
4. A capsule as claimed in claim 2 wherein said steel has a carbon content of less than .004%.
5. A capsule as claimed in claim 1, 2 or 3 wherein a said insert is plate-shaped, conical, hemispherical or funnel-shaped with a central bore for receiving the inner wall of the capsule and fabricated in one or several pieces from solid material or pressed from powder.
6. A capsule as claimed in claim 1, wherein one said insert is a plate-shaped, conical, hemispherical or funnel-shaped insert produced in one or several pieces from solid material or pressed from powder.
7. A capsule as claimed in claim 5 wherein the or each insert is in the form of a cover closing the capsule at one end and provided at least towards the powder filling with an intermediate layer of glass.
8. A capsule as claimed in claim 7, wherein the inserts are welded to the outer wall and inner wall of the capsule.
9. A capsule as claimed in claim 1, 2 or 3, wherein sheet-metal covers are arranged between the inserts and the interior of the capsule.
10. A capsule as claimed in claim 1, 2 or 3, wherein the inserts consist of an electrically conductive metal, preferably soft iron.
11. A capsule as claimed in claim 1, 2 or 3, wherein a funnel-shaped insert provided with a central bore is used for the front end of the capsule, the angle between the wall of said central bore and the conical outer surface of the funnel-shaped insert amounting to between 40 and 60°.
12. A capsule as claimed in claim 1, 2 or 3, wherein a funnel-shaped insert provided with a central bore is used for the front end of the capsule, the angle between the wall of said central bore and the conical outer surface of the funnel-shaped insert amounting to approximately 45°.
13. A capsule as claimed in claim 1, 2 or 3 wherein an annular insert provided with a central bore is provided at least at the front end of the capsule, said annular insert having a substantially flat end face and a boundary surface of substantially arcuate cross-section between the wall of the central bore and its largest external diameter, the centre of curvature of said arcuate cross-section lying substantially in the region of the inter-section between the flat end face and the central bore.
14. A capsule as claimed in claim 1, wherein at least the outer wall of the capsule has substantially uniform strength properties in the axial direction around its circumference.
15. A capsule as claimed in claim 14, wherein at least said outer wall is spirally welded.
16. A capsule as claimed in claim 14, wherein at least said outer wall is an extrusion.
17. A capsule as claimed in claim 14 or 15, wherein the spiral formed by the weld seam has a pitch angle which in relation to the length of the capsule is such that the weld seam forms at least one complete turn.
18. A capsule as claimed in claim 14, 15 or 16 wherein the spiral weld seam is smoothed by rolling and/or grinding.
19. A capsule as claimed in claim 1 wherein at the ends of the capsule, the outer and/or inner wall has substantially cylindrical sections of which the external and/or internal diameter corresponds to around ? 0.1% of the required diameter of the pressing, the bulge of the outer wall opening tangentially into these cylindrical sections.
20. A capsule as claimed in claim 19 wherein from each of said cylindrical sections the bulge increases gradually and steadily in the axial direction, towards the middle of the capsule, initially in a region having a concave cross-section, the inclination of the outer wall relative to the axis of the capsule also increasing gradually and steadily, after which the inclination of the outer wall remains substantially constant via a conical intermediate region followed by a region in which the outer wall has an out-wardly convex cross-section and merges gradually and steadily into an axially parallel central region, those regions of the outer wall which vary in cross-section each forming a transitional region which is situated in the region of an insert of which the cross-sectional contour is a virtual mirror image of the contour of the transitional region which is reflected at the line of the required cylindrical form of the pressing, but which is increased in the radial direction in the ratio of the diameter of the pressing to the reduction in diameter.
21. A capsule as claimed in claim 20 wherein the cylindrical central region of the outer wall which has a substantially constant diameter extends substantially over the entire region between the inserts.
22. A process for forming a capsule for producing a pressing for use in extrusion of a dense metallic tube, said process comprising providing a tubular, thin-walled, sheet metal container, said container having an inner and an outer peripheral wall; reducing the diameter of opposite end portions of the outer peripheral wall, so that intermediate those end portions said outer peripheral wall defines a bulge which is directed outwards against the direction of shrinkage which will occur during subsequent isostatic pressing, the dimensions of said bulge being selected such that it will be substantially eliminated by such shrinkage, and providing inserts for closing the opposite ends of said container.
23. A process as claimed in claim 22, wherein at the ends of the capsule, the outer and/or inner wall is provided with substantially cylindrical sec-tions of which the external and/or internal diameter corresponds within around ? 0.2% to the required diameter of the pressing, and wherein the bulge of the outer and/or inner wall opens tangentially into these cylindrical sections.
24. A process as claimed in claim 22, wherein a plate-shaped, conical, hemispherical or funnel-shaped insert, produced in one or several pieces from solid material or pressed from powder, is arranged at the front and/or rear end of the capsule.
25. A process as claimed in claim 24, wherein the insert or inserts is/are welded to the outer wall and optionally to the inner wall of the capsule.
26. A process as claimed in claim 24, wherein layers of glass are arranged between the inserts and the interior of the capsule.
27. A process as claimed in claim 22, wherein at least the outer wall of the capsule is made of a spiral-welded or extruded tube section.
28. A process as claimed in claim 27, wherein the pitch of the spiral weld seam in relation to the length of the tube section is such that the weld seam of the tube section forms at least substantially one complete turn.
29. A process for producing a pressing for use in extrusion of a dense metallic tube; said process comprising:
providing a capsule by the process set forth in claim 22;
filling said capsule with a powder of metal or metal alloys or mixtures thereof with or without ceramic powders;
increasing the density of said powder by vibration to between 60 and 71% of the theoretical density;
sealing said inserts to the opposite ends of said container and further increasing the density of said powder to at least 80 to 93% of the theoretical density by isostatic cold pressing under a pressure of at least 4000 bars to produce a pressing; and extruding said pressing in an extrusion means to form said dense metallic tube.
providing a capsule by the process set forth in claim 22;
filling said capsule with a powder of metal or metal alloys or mixtures thereof with or without ceramic powders;
increasing the density of said powder by vibration to between 60 and 71% of the theoretical density;
sealing said inserts to the opposite ends of said container and further increasing the density of said powder to at least 80 to 93% of the theoretical density by isostatic cold pressing under a pressure of at least 4000 bars to produce a pressing; and extruding said pressing in an extrusion means to form said dense metallic tube.
30. A process as claimed in claim 29, wherein at least the insert pro-vided at a forward end of said container is of a ductile material which has a yield point lower than the yield point of the compacted powder filling within the pressing.
31. Process according to claim 29, wherein for obtaining good lubrica-tion when extruding, glass for lubrication is placed in form of a glass disc on the front end of the pressing in the container or receiver of the extrusion press, said glass being supplied and substantially uniformly distributed in the circumferential direction between tool and the object being extruded during the entire extrusion operation by means of the bevelled front edge of the front insert and by the very precise adaptation of the substantially exactly cylindric outer diameter of the pressing to the substantially cylindric inner diameter of the container or receiver of the extrusion press.
Applications Claiming Priority (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE2846660A DE2846660C2 (en) | 1978-10-26 | 1978-10-26 | Annular casing for extrusion bolts for the powder metallurgical production of pipes |
| DEP2846658.2 | 1978-10-26 | ||
| DEP2846660.6 | 1978-10-26 | ||
| DE19782846658 DE2846658C2 (en) | 1978-10-26 | 1978-10-26 | Metallic shell for the production of extrusion billets for the powder metallurgical production of pipes |
| DE19782846659 DE2846659A1 (en) | 1978-10-26 | 1978-10-26 | Powder filled capsule for use as extrusion blank - for making stainless steel or nickel-chromium alloy tubes, is isostatically pressed after filling |
| DEP2846659.3 | 1978-10-26 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1120005A true CA1120005A (en) | 1982-03-16 |
Family
ID=27187716
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000338386A Expired CA1120005A (en) | 1978-10-26 | 1979-10-25 | Capsules and pressings for extruding objects, particularly tubes, and a process for producing the capsules and pressings |
Country Status (23)
| Country | Link |
|---|---|
| EP (1) | EP0020536B1 (en) |
| AT (2) | AT374387B (en) |
| BE (1) | BE879623A (en) |
| BR (1) | BR7906929A (en) |
| CA (1) | CA1120005A (en) |
| CH (1) | CH652054A5 (en) |
| CS (1) | CS216687B2 (en) |
| DE (1) | DE2967396D1 (en) |
| DK (1) | DK153742C (en) |
| ES (3) | ES485385A0 (en) |
| FI (1) | FI61649C (en) |
| FR (1) | FR2439639A1 (en) |
| GB (1) | GB2034226B (en) |
| HU (1) | HU179975B (en) |
| IT (1) | IT1127798B (en) |
| MX (1) | MX150474A (en) |
| NL (1) | NL7907894A (en) |
| NO (1) | NO151779C (en) |
| PL (1) | PL132096B1 (en) |
| RO (1) | RO79124A (en) |
| SE (1) | SE441336B (en) |
| SU (1) | SU1369666A3 (en) |
| WO (1) | WO1980000803A1 (en) |
Families Citing this family (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2492291A1 (en) * | 1980-10-22 | 1982-04-23 | Uk I Sp | Container for hot extrusion of metal powder - with flow-modifying profiling element(s) to improve prod. yield |
| DE3530741C1 (en) * | 1985-08-28 | 1993-01-14 | Avesta Nyby Powder AB, Torshälla | Process for the manufacture of powder metallurgical objects |
| US4640815A (en) * | 1985-10-17 | 1987-02-03 | Crucible Materials Corporation | Method and assembly for producing extrusion-clad tubular product |
| US4640814A (en) * | 1985-10-17 | 1987-02-03 | Crucible Materials Corporation | Method for producing clad tubular product |
| SE8603686D0 (en) * | 1986-09-03 | 1986-09-03 | Avesta Nyby Powder Ab | HAUL |
| FR2704465B1 (en) * | 1993-04-29 | 1995-06-23 | Alsthom Intermagnetics Sa | Mono or multifilament composite billet closure piece. |
| SE505247C2 (en) * | 1994-12-07 | 1997-07-21 | Sandvik Ab | Process for manufacturing memory metal tubes |
| US5689976A (en) * | 1996-10-24 | 1997-11-25 | Ansell Edmont Industrial, Inc. | Reinforced glove and method for forming the same |
| GB201119238D0 (en) * | 2011-11-08 | 2011-12-21 | Rolls Royce Plc | A hot isostatic pressing tool and a method of manufacturing an article from powder material by hot isostatic pressing |
| GB201119240D0 (en) * | 2011-11-08 | 2011-12-21 | Rolls Royce Plc | A hot isostatic pressing tool and a method of manufacturing an article from powder material by hot isostatic pressing |
| CZ308392B6 (en) * | 2017-09-08 | 2020-07-22 | UJP PRAHA a.s. | Powder moulding for efficient sintering |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CH316476A (en) * | 1952-06-13 | 1956-10-15 | Ici Ltd | Process for protecting bodies formed from metal powder against oxidation |
| FR1164348A (en) * | 1956-01-10 | 1958-10-08 | Oerlikon Buehrle Ag | Manufacturing process of extruded profiled bodies in ferrous powder |
| BE709814A (en) * | 1968-01-24 | 1968-05-30 | ||
| US3823463A (en) * | 1972-07-13 | 1974-07-16 | Federal Mogul Corp | Metal powder extrusion process |
| DE2419014C3 (en) * | 1974-04-19 | 1985-08-01 | Nyby Bruks AB, Nybybruk | Method of manufacturing stainless steel pipes and application of the method to the manufacture of composite pipes |
| US3892030A (en) * | 1974-04-29 | 1975-07-01 | Us Air Force | Method of fabricating a billet from metal preforms and metal powder |
| DE2737248C2 (en) * | 1977-08-18 | 1985-09-19 | MTU Motoren- und Turbinen-Union München GmbH, 8000 München | High strength component with a complex geometric shape and process for its manufacture |
-
1979
- 1979-10-19 SE SE7908702A patent/SE441336B/en not_active IP Right Cessation
- 1979-10-23 DK DK445879A patent/DK153742C/en not_active IP Right Cessation
- 1979-10-24 NO NO793403A patent/NO151779C/en unknown
- 1979-10-24 AT AT0692379A patent/AT374387B/en not_active IP Right Cessation
- 1979-10-24 CS CS797212A patent/CS216687B2/en unknown
- 1979-10-24 CH CH9544/79A patent/CH652054A5/en not_active IP Right Cessation
- 1979-10-25 BR BR7906929A patent/BR7906929A/en not_active IP Right Cessation
- 1979-10-25 ES ES485385A patent/ES485385A0/en active Granted
- 1979-10-25 SU SU792841453A patent/SU1369666A3/en active
- 1979-10-25 GB GB7937062A patent/GB2034226B/en not_active Expired
- 1979-10-25 CA CA000338386A patent/CA1120005A/en not_active Expired
- 1979-10-25 HU HU79GA1303A patent/HU179975B/en not_active IP Right Cessation
- 1979-10-25 FI FI793336A patent/FI61649C/en not_active IP Right Cessation
- 1979-10-25 BE BE0/197811A patent/BE879623A/en not_active IP Right Cessation
- 1979-10-26 IT IT84147/79A patent/IT1127798B/en active
- 1979-10-26 DE DE7979901411T patent/DE2967396D1/en not_active Expired
- 1979-10-26 PL PL1979219241A patent/PL132096B1/en unknown
- 1979-10-26 NL NL7907894A patent/NL7907894A/en not_active Application Discontinuation
- 1979-10-26 AT AT79901411T patent/ATE11881T1/en not_active IP Right Cessation
- 1979-10-26 RO RO7999059A patent/RO79124A/en unknown
- 1979-10-26 FR FR7926603A patent/FR2439639A1/en active Granted
- 1979-10-26 WO PCT/EP1979/000083 patent/WO1980000803A1/en unknown
- 1979-10-26 MX MX179801A patent/MX150474A/en unknown
-
1980
- 1980-05-07 EP EP79901411A patent/EP0020536B1/en not_active Expired
- 1980-06-30 ES ES1980251783U patent/ES251783Y/en not_active Expired
- 1980-06-30 ES ES1980251782U patent/ES251782Y/en not_active Expired
Also Published As
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA1120005A (en) | Capsules and pressings for extruding objects, particularly tubes, and a process for producing the capsules and pressings | |
| US4486385A (en) | Tubular composite elements processes and a pressing for their production | |
| US4401723A (en) | Capsules and pressings for extruding objects, particularly tubes, and a process for producing the capsules and pressings | |
| US5903815A (en) | Composite powdered metal component | |
| US4142888A (en) | Container for hot consolidating powder | |
| AU621684B2 (en) | Hollow charge with a metallic lining, method and device for its manufacturing | |
| US5972521A (en) | Expanded metal structure and method of making same | |
| RU2100145C1 (en) | Process of manufacture of articles with through hole by method of powder metallurgy | |
| EP0356584B1 (en) | Process for forming shapes from powder in a container | |
| US5005756A (en) | Method of producing bimetallic tubes and the tubes obtained by this method | |
| US4373012A (en) | Casings and pressed parts utilized for the extrusion of articles, particularly pipes, and manufacturing process of such casings and pressed parts | |
| USRE31355E (en) | Method for hot consolidating powder | |
| US4364162A (en) | Process for the after-treatment of powder-metallurgically produced extruded tubes | |
| JPH02141506A (en) | Manufacture of tubular cam shaft | |
| SE460345B (en) | PRESSURE FOR PREPARATION OF COMPOUNDROS | |
| US20240100595A1 (en) | Hot isostatic pressing container with enhanced directional consolidation | |
| KR840001303B1 (en) | Capsules and pressings for extruding objects partieularly tubes,ana a process for producing the capsules and pressings | |
| CN109648769A (en) | A kind of molding machine of polytetrafluoroethylcontainer container backing layer | |
| SU1026965A1 (en) | Method of producing bimetallic cutting tool | |
| EP0483139B1 (en) | Hot pressing of particulate materials | |
| FR2796322A1 (en) | Mechanical component able to be heated by the internal circulation of a fluid and a method for the fabrication of such a mechanical component | |
| JPS61186407A (en) | Production of wear-resistant circular cylindrical member | |
| JPS63206408A (en) | Production of composite member by diffusion joining | |
| FI97452B (en) | Production of a piece | |
| JPH03170604A (en) | Manufacture of clad tube using powder |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |