JPS585749B2 - Casting method for titanium castings made of pure titanium or alloys whose main component is titanium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for casting titanium castings that enables casting of titanium casting materials made of pure titanium or alloys mainly composed of titanium with little or no oxidation. This is what we provide.

Titanium materials made of pure titanium or titanium-based alloys have high heat resistance, excellent toughness, wear resistance, and corrosion resistance, are light, and have far superior physical and mechanical properties in many other respects. It also has good wettability with living organisms (a property that is compatible with living organisms and does not cause harm to living organisms even when implanted into living organisms during surgery), so it is used not only in industry but also in dentures, plastic surgery, etc. It is eagerly awaited that it will be put to use in the surgical medical field.

However, titanium material has extremely high activity and oxidizes rapidly even during cold forging, making it extremely difficult to process and requiring special equipment and techniques to be cold forged in a vacuum atmosphere. It has only been processed in detail.

For this reason, titanium products cannot be manufactured on an industrial basis for complex and elaborate shapes such as dentures, and even for simple and rough shapes, the productivity is extremely low and the processing cost is extremely high, making it extremely impractical. Inferior.

The inventor repeatedly conducted experiments in which titanium casting materials were cast into silica molds under an inert gas atmosphere using a dental casting machine, and found that despite maintaining an almost perfect inert gas atmosphere, , the titanium castings that were cast had a high degree of oxidation and turned black, making them unusable for practical use.

We also considered various casting machines, but were unable to produce a practical titanium cast product.

Furthermore, after repeated experiments with molds made from various materials, it was found that titanium castings have a relatively low degree of oxidation and are superior in formability as molds, and molds made from magnesia were found to be slightly better. Although the results have been obtained, it is still far from practical.

As we continued to make further improvements, we discovered that when titanium casting material was cast into a magnesia forging die while keeping it at a certain low temperature, or when a small amount of titanium casting material was cast into a magnesia forging die, almost no oxidation occurred. As a result of investigating the cause of this,
The following was discovered.

That is, oxides such as silica are suitable as materials that allow the mold to be easily made with high precision.

However, titanium castings made using oxide molds are severely oxidized and are not practical.

The cause of oxidation is that the molten titanium casting material (melting point 1
It was confirmed that the titanium casting material was oxidized by removing oxygen from the oxide mold with very high activity (668°C, standard casting temperature 1800-1900°C).

This shows that in the temperature vs. oxide formation energy diagram in Figure 6, the diagram A or B for titanium and the diagram for silica 2SiO or S
This was also supported by the relationship between C and D in the diagram for iO2.

Furthermore, from the relationship between diagram A or B in the case of titanium and diagram E in the case of magnesia, titanium casting materials are severely oxidized even in an atmosphere with an appropriate casting temperature of about 1900 to 2000°C. It is confirmed that this will happen.

The first invention of the present application has developed a method for casting titanium castings in which little or no oxidation occurs, in which a titanium casting mold is molded with pure magnesia or a magnesia molding material containing magnesia as a main component, When the titanium casting material is melted and cast, the magnesium content of the magnesia molding material is reduced by keeping the titanium casting material in the titanium casting mold made of magnesia molding material below a certain temperature from the beginning or cooling it quickly. The bond between the magnesia mold material and the oxygen component is maintained in a stable manner, and while the molten titanium casting material solidifies and cools after being cast, the oxygen in the magnesia mold material is taken away and oxidation occurs little to no. hand,
The purpose of the present invention is to provide a casting method that allows titanium castings to be cast well without oxidizing them.

The second invention of the present application further improves the first invention to improve the casting performance of titanium castings with almost no oxidation, so that it is possible to cast high-quality products with precision and no casting defects. To this end, we provide a casting method in which molten titanium casting material is vigorously poured into a mold using an inert gas flow, and even after casting, the molten metal is compressed with inert gas to maintain the strong action of the riser. .

Next, an example of an automatic precision casting machine for carrying out the present invention and an example of the procedure for carrying out the present invention will be described in detail.

The drawing shows an automatic precision casting machine, and the basic principle of its casting is as follows.

That is, in the melting chamber 1, a high voltage is applied between the arc discharge electrode rod 2 and a predetermined cylindrical titanium casting material 3,
An arc discharge 4 is generated there, and the titanium casting material 3 is melted.

As shown in FIGS. 4A to 2, the titanium casting material 3 is collected in the crucible 5, which melts down from the top, and when it is completely melted to the bottom, the tap hole 6 in the bottom wall of the crucible 5 becomes solid. The material is no longer blocked at the bottom, and the molten material 3a passes through the tapping hole 6 and the pouring hole 7 under its own weight, and flows into the forming cavity 11 from the sprue 10 of the titanium casting mold 13 in the casting chamber 8.

From before melting titanium casting material 3 to after casting, melting chamber 1
By maintaining the casting chamber 8 in an inert gas atmosphere, deterioration such as oxidation of the material is prevented.

In addition, an inert gas is supplied from the melting chamber 1 at a differential pressure of about 4 kg/ffl to the communication groove 12, the pouring hole 7, the sprue 10 in the mold 13, the modeling cavity 11, and the titanium casting mold 1 consisting of an air-permeable investment material.
3 and continues to flow into the casting chamber 8, when the titanium casting material 3 is completely melted and flows into the mold 13, the melted material 3a is carried by the inert gas flow and is poured into the molding cavity 11 of the mold 13.
After flowing smoothly deep into the body, the differential pressure is approximately 4 kg.
Continue pressing with /ffl to make the hot water flow better.

The inert gas flow for this purpose is controlled as follows.

That is, when the start button 15 of the electric control device 14 is pressed, the vacuum pump 16 is started, and the melting chamber 1 is connected to the gas pipes 17, 20,
The casting chamber 8 is evacuated via the electromagnetic three-way valve 18 and the connector 19, and the casting chamber 8 is evacuated via the gas pipes 20, 21 and the strainer 22.

When the degree of vacuum in the melting chamber 1 and the casting chamber 8 reaches 7001 Hg, the vacuum switch 23 is activated, the valve body 18a of the electric aE-way valve 18 is moved to the left, and the evacuation of the melting chamber 1 is stopped. At the same time, inert gas such as argon is supplied from the cylinder 24 to the pressure setting valve 25 at a rate of 3 kg/cr? t, gas pipe 1
7.25', is injected through the electromagnetic three-way valve 18 and maintained at 3 atmospheres.

The casting chamber 8 continues to be evacuated until the casting is completed.

When the melting chamber 1 exceeds O-5 kg/ffl,
The pressure switch 26 is activated to turn on the melting device M arc discharge power panel 27, causing an arc 4 between the arc discharge electrode rod 2 and the titanium casting material 3.

After the casting is completed, the electric control device 14 turns on the vacuum pump 16.
Then, the electromagnetic three-way valve 18 is deactivated, the valve body 18a is moved to the right, and evacuation and inert gas injection are stopped. 19 to the atmosphere from the check valve 28,
A part of it is drawn into the casting chamber 8.

As a result, the melting chamber 1 and the casting chamber 8 are brought to atmospheric pressure, and casting is completed.

As the titanium casting material 3, pure titanium or an alloy mainly composed of titanium is used.In order to prevent oxidation of the titanium casting material 3, which has extremely high activity and easily generates oxides, titanium casting mold material 3 is used. Pure magnesia or a magnesia mold material containing magnesia as a main component is used as the material.

In other words, as can be seen from the temperature vs. oxide formation energy diagram in Figure 6, at temperatures below about 1700°C, the 2MgO diagram H is located below the 2TiO diagram, and pure magnesia (MgO) The oxide formation energy when is generated is smaller than the oxide formation energy of titanium.

That is, it is shown that at temperatures below about 1700° C., there is little or no bonding reaction between the oxygen in the magnesia molding material and the titanium casting material.

However, the temperature of the molten metal during casting of titanium casting materials is approximately 19
Since the temperature is 00 to 2000°C, it is higher than the above temperature of 1700°C, and an oxidation reaction between the titanium casting material to be cast and oxygen in the mold 13 cannot be prevented.

Therefore, in the present invention, while forming a titanium casting mold using magnesia mold material, at least the part of this mold 13 that contacts the molten metal 3a of the titanium casting material 3 is maintained at a temperature of about 1700° C. or less from the beginning or immediately It should be cooled or cooled down.

In this embodiment, a method is used in which the mass of the titanium casting material 3 to be cast is reduced and the molten metal 3a of the titanium casting material 3 is quickly cooled using a large-mass mold 13 during casting.

In addition, as the magnesia mold material containing magnesia as the main component, for example, 40% each of magnesia clinkers M2 and M4 (components are shown in Table 1) manufactured by Nihon Kagaku Togyo Co., Ltd., which are commercially available for heat-resistant materials, The mixture is mixed at a ratio of 60%, and 10% of zirconia or zircon sand is added as a particle size control agent to 90% of this mixture.

Magnesia is a heat-resistant material whose contact point is 1100℃ higher than that of silica, and because of its excellent high-temperature stability, it has traditionally been used as a highly refractory cement for stamping materials in vacuum melting furnaces and backup materials for crucibles. .

Magnesia mold material not only has excellent heat resistance, but also has the following advantages:

In other words, the magnesia clinkers M2 and M4 solidify like Boltland cement just by adding water and kneading them, so it is easy to make molds.Q Moreover, magnesia does not undergo transformation like silica. , its thermal expansion curve shows a substantially straight line like that of metal, and expands by about 1.1% at 1000°C.

This characteristic is advantageous when manufacturing precision cast products such as dentures.

That is, by preheating the titanium casting mold 13 made of magnesia casting material to a predetermined temperature with a heating device and expanding it, and then pouring the molten metal 3a of the titanium casting material 3, the titanium casting material after casting is solidified and expanded. A method is possible that reduces the degree to which a titanium casting becomes smaller than a casting master due to shrinkage during cooling.

Next, the structure of the automatic precision casting machine will be specifically explained.

That is, the reference numeral 29 is a casting machine body made of aluminum alloy or zinc alloy, in which a melting chamber 1 and a casting chamber 8 are separated by a bird wall 4.
2, it is formed by dividing it vertically.

The front wall portion of the casting machine main body 29 is formed into a flange shape, and an operation port 31 of the melting chamber 1 and an operation port 32 of the casting chamber 8 are opened in the flange portion 30 side by side vertically.

The crucible 5 containing the titanium casting material 3 has an operation port 31 in the melting chamber 1.
The mold body 9 consisting of the mold 13 and its cylindrical frame 47 can be taken in and out of the casting chamber 8 through the operation port 32.

Both operation ports 3L32 are opened and closed simultaneously by a single door type lid 33, and closed and locked by a closing lid locking mechanism 34.
5, 36.

That is, the lid 33 can be opened and closed with respect to the flange portion 30 using both the upper and lower hinges 37 at the right end as fulcrums, and is locked at the intermediate height portion at the left end.

The lid closing lock mechanism 34 is formed on the back surface of the flange portion 30 to lock a lever 38 pivotably supported on the lid 33 and a locking pawl 40 formed at the rear end of the shaft 39 of the lever 38. It consists of a locking receiving part 41.

A mounting hole 67 is drilled in the center of the ward wall 42, and the mounting hole 67
A crucible holder 43 made of copper alloy or copper such as a planer is removably fixed in a penetrating manner, and a hot water through hole 7 is provided in the center of the crucible holder 43.
is dawned.

A crucible 5 is disposed in the melting chamber 1 and a mold body 9 is disposed in the casting chamber 8, sandwiching the pouring hole 7, and abuts on the upper and lower surfaces of the crucible holder 43.

In the center of the upper space of the melting chamber 1, the arc discharge electrode rod 2 of the melting device M is arranged to face the titanium casting material 3 placed on the crucible 5 from above.

The crucible 5 is constructed as shown in FIG.

That is, the crucible body 44 is made of copper, a copper alloy containing copper as a main component, or a carbon material made of pure carbon or a substance containing carbon as a main component, and is formed into a short cylindrical shape. is formed.

A receiving surface 46 for the cylindrical titanium casting material 3 is formed in the shape of an inverted cone on the central bottom surface of the material chamber 45, and a tap hole 6 for dissolving the melted material is formed in the bottom wall of the crucible body 44 at the center of the material receiving surface 46. It's dawning.

The tap hole 6 has a conical surface at its upper part, and a cylindrical surface at its lower part.

The communication groove 12 is cut out in a cross shape on the bottom surface of the crucible body 44.

And, the crucible 5 has a capacity of
It is formed into a thick wall with a large mass, and has a high quality. When melting the titanium casting material 3 in the crucible 5 made of copper material, the thermal energy transmitted from the molten metal 3a of the titanium casting material 3 to the crucible 5 is quickly and widely diffused to each part of the wall of the crucible 5. By making I'c, the rate of temperature rise of the part of the crucible 5 that contacts the molten metal 3a of the titanium casting material 3 is significantly reduced, and the titanium casting material is heated before that part of the crucible 5 reaches the melting temperature. It is assumed that the molten metal 3a of the material 3 has been poured from the crucible 5 into the titanium casting mold 13.

Next, as shown in FIG. 2, one pole 27a of the output terminal of the arc discharge power supply board 2γ is connected to the arc discharge electrode rod 2,
The ten poles 27b are electrically connected to the casting material 3 in the crucible 5 through the crucible holder 43 and the crucible 5, which are connected to the casting machine main body 29.

The mold body 9 is made by placing a prototype in an iron cylindrical mold 47, pouring an investment material of magnesia mold material kneaded with water into it and solidifying it, and then heating it at about 800°C in an electric furnace. It is formed by sintering.

This mold 13 is porous and highly breathable, and has a sprue 10 in its upper part and a modeling cavity 11 in its lower part.

The mold body 9 is placed on the mold pedestal 48, and by tightening the rotary operating tool 49, it is pushed up via the support shaft 51 and the mold pedestal 48 by a spiral plate cam 50, which is a type of one-rotation cam. Then, it is brought into airtight contact with the mold receiving surface 53 on the lower surface of the peripheral wall of the pouring hole 7 of the pedestal 43 with the sealing member 52 in between.

That is, a bracket 54 with an inverted L-shaped side surface is fixed to the bottom wall of the casting chamber 8, and a lifting guide hole 55 is vertically oriented in the clay wall of the bracket 54, and a pivot hole 56 is oriented longitudinally in the front wall of the bracket 54. It's dawning.

An intermediate portion of a camshaft 57 is rotatably supported in the pivot hole 56, and a rotation operating tool 49 is externally fitted and fixed to the front end of the camshaft 57, and a spiral plate cam 50 is externally fixed to the rear end thereof.

A support shaft 51 passes through the elevating guide hole 55 so as to be movable up and down, and the fitting gap therebetween is sealed with an 01J ring 52.

The upper end of the support shaft 51 fixedly supports the mold pedestal 48 in the casting chamber 8, and the lower end thereof is formed into a cam follower 58 having an arcuate surface and is in line contact with the cam 50.

The cam follower 58 is prevented from rotating by coming into planar contact with a rotation stopper 59 on the back surface of the front wall of the bracket 54 so as to be slidable up and down.

The mold pedestal 48 is urged downward by a pull-down spring 60, and the pull-down spring 60 is connected to both spring locking devices 61 . 62.

The mold pedestal 48 is an upper and lower halves 63. 64, the upper divided body 64 is connected to the lower divided body 63 with dowels 65 holes and 6
By fitting with 6 holes, it can be placed concentrically or removed freely.

Concentric and cross ventilation grooves 68 are formed on the upper surface of each divided body 63,64.

Incidentally, reference numeral 69 is a water cooling hole, which is provided through the wall of the partition wall 42 to surround the pedestal 43.

The present invention is a method of casting a titanium casting material as described above using the automatic precision casting machine according to the embodiment described above, but the first invention is a method that involves the following steps.

A titanium casting mold 13 used for casting a titanium casting material 3 made of pure titanium or an alloy mainly composed of titanium.
is molded using pure magnesia or a magnesia molding material containing magnesia as a main component, and the titanium casting material 3 is melted in a melting device in an oxygen-free atmosphere in a crucible 5 of a forging machine, and titanium is melted while maintaining an oxygen-free atmosphere. The molten metal 3a of the casting material 3 is poured from the crucible 5 into the titanium casting mold 13 made of magnesia mold material, and the oxide production energy of the titanium casting material 3 is set to a value larger than the oxide production energy of magnesium when magnesia is produced. At least the part of the titanium casting mold 13 made of magnesia molding material that comes into contact with the titanium casting material 3 is either held from the beginning or quickly cooled at a temperature of The titanium casting material 3 contained in the titanium casting material 3 is made to have little or no bonding reaction with the oxygen in the magnesia molding material 13 forming the titanium casting mold 13, thereby producing a titanium casting product with little to no oxidation. This is a casting method to obtain

Moreover, the second invention is a method having the following steps.

The melting chamber 1 and the casting chamber 8 in the casting machine main body are vertically opposed to each other with a partition wall 42 in between, and are formed in an independent airtight manner.
A melting hole 7 is opened in the melting chamber 1, a crucible 5 and a melting device M are installed in the melting chamber 1, a titanium casting mold 13 is installed in the casting chamber 8 in airtight communication with the pouring hole 7, and the titanium casting mold 13 is made of pure metal. A titanium casting material 3 made of magnesia or a magnesia mold material containing magnesia as a main component is placed in a crucible 5, and a titanium casting material 3 made of pure titanium or an alloy containing titanium as a main component is placed in a melting chamber 1, a casting chamber 8, and a titanium casting mold. 13 is filled with an inert gas to maintain an inert gas atmosphere, the titanium casting material 3 is melted in the crucible 5 by the melting device M, the melting chamber 1 is kept at a higher pressure than the casting chamber 8, and the inert gas atmosphere is maintained. The gas continues to flow from the melting chamber 1 to the casting chamber 8 via the through hole 7 and the titanium casting mold 13, and the titanium casting material 3 is transferred to the melting device M in the crucible 5.
The molten metal 3a thus obtained is placed in an inert gas flow from the crucible 5 and poured into the titanium casting mold 13 through the through hole 7, and then the melting chamber 1 and the casting chamber 8 are The titanium casting mold 13 made of magnesia molding material is compressed by a differential pressure to a temperature where the oxide formation energy of the titanium casting material 3 becomes larger than the oxide formation energy of magnesium when magnesia is generated. At least the part that contacts the titanium casting material 3,
The titanium casting material 3 cast into the titanium casting mold 13 is either held from the beginning or cooled quickly.
This is a casting method that produces a titanium cast product with little or no oxidation by causing little or no bonding reaction with oxygen in the magnesia mold material forming the titanium casting mold 13.

Here, as a modification of the above method, a part thereof can be modified as follows.

A In the case of the above example, an inert gas atmosphere of argon was used as the oxygen-free atmosphere, but instead of this, the melting chamber 1
It is also possible to evacuate the inside of the casting chamber 8, melt the titanium casting material 3 in the crucible 5 in a vacuum state, and then cast it.

B. A cooling means is provided to prevent the temperature of the titanium casting mold 13 made of magnesia mold material from rising.

For example, it is also possible to form a refrigerant passage in the mold 13 so as to surround the modeling cavity 11 in the mold 13, and to cool the mold 13 by supplying a refrigerant such as cooling water to this refrigerant passage.

The above cooling method is particularly effective when casting a relatively large cast product.

C The melting device M for melting the titanium casting material 3 is not limited to the arc melting devices 27 and 2, but can also be melted by a high frequency melting device that heats with high frequency.

Since the present invention has the above-described procedural configuration, it has the following effects.

First, the effects of the first invention are as follows.

1. Titanium castings made of pure titanium or titanium-based alloys can be cast with little or no oxidation.

This allows titanium products to be manufactured easily, efficiently, and accurately without impairing titanium's excellent physical and mechanical properties.

2. Magnesia mold material is a highly refractory material that is widely commercially available and used as a filling material for furnace walls, so it is easy to obtain, and it can be used as a mold by simply adding water, kneading it, and sintering it at about 800℃. Since the strength of the mold is sufficiently increased, it is possible to omit the addition of a binder to increase the strength of the mold, and the mold can be manufactured simply, inexpensively, and efficiently.

3. Molds made with magnesia mold material have sufficient fire resistance and pressure resistance just by sintering them at 700 to 800°C using electric furnaces, which are widely used in foundries, so they are not widely used in foundries. Titanium casting molds can be easily sintered using an existing electric furnace without the need to purchase a new high-temperature heating furnace.

4. The thermal expansion curve of magnesia mold material is not only linear like that of metal materials, but also has a large coefficient of thermal expansion and expands significantly when preheated.By utilizing these characteristics, titanium casting material can solidify after being cast. However, even if the titanium cast product shrinks due to cooling, the degree to which the titanium cast product becomes smaller than the cast master mold is reduced, and a titanium cast product that approximates the master mold and has high dimensional accuracy can be obtained.

This effect is particularly valuable in the case of dental castings where the casting pattern cannot be made thick in advance.

The effects of the second invention are as follows in addition to the effects of the first invention.

5. The molten titanium casting material is pushed into the mold with a strong force that combines the falling force of its own weight with the flow force of the inert gas, so the molten metal flows extremely well, and can be used in both thin and wide areas as well as long and narrow areas.
It pours evenly and deeply, and has excellent casting accuracy and formability.

6. After the molten metal is poured into the mold, it continues to be pressurized due to the pressure difference between the melting chamber and the casting chamber, and is strongly influenced by the riser.
It is possible to produce fine, high-quality titanium castings that are free from stains and stains.

7. When tapping holes are drilled in the bottom wall of the crucible, when all of the titanium casting material has been melted, each tap hole that was previously blocked by solid titanium casting material will be opened automatically. .

As a result, the molten metal is automatically tapped out from the tapping hole in a timely manner, so that the molten metal is poured while being stably heated within the appropriate casting temperature range, and underheating or overheating does not occur at all.

Therefore, it is possible to obtain a high-quality titanium cast product by preventing defects such as defects due to poor water flow due to insufficient heating and defects such as rough skin, cracks, etc. due to excessive heating.

[Brief explanation of drawings]

1 to 5 show a casting machine etc. for carrying out the present invention, FIG. 1 is a perspective view of the casting machine main body, FIG. 2 is a vertical side view, FIG. 4A to 4D are action diagrams from the start of melting to the start of casting, FIG. 5 is a view taken along the V arrow in FIG. 2, and FIG. 6 is a diagram of temperature versus oxide formation energy. 1... Melting chamber, 2... Arc furnace electrode rod, 3...
Titanium casting material (3a... molten metal), 4... arc discharge, 5... crucible, (45... material chamber, 6... tapping hole), T... pouring hole, 8... ...Casting room, 13...
Titanium casting mold, 29... Casting machine body, 42...
Section wall, M...dissolving device.

Claims (1)

[Scope of Claims] 1. A titanium casting mold used for casting a titanium casting material made of pure titanium or an alloy whose main component is titanium, is molded with pure magnesia or a magnesia mold material whose main component is magnesia, Titanium casting material is melted in a melting device in an oxygen-free atmosphere in a crucible of a casting machine, and while maintaining an oxygen-free atmosphere, the molten titanium casting material is poured from the crucible into a titanium casting mold made of magnesia molding material.
At least one of the titanium casting molds made of magnesia molding material is brought into contact with the titanium casting material at a temperature at which the oxide formation energy of the titanium casting material is greater than the oxide formation energy of magnesium when magnesia is generated. A magnesia mold in which the titanium casting material is cast into a titanium casting mold by either holding it from the beginning or cooling it quickly. Made of pure titanium or an alloy whose main component is titanium, which is characterized by almost or no bonding reaction with oxygen in the material to obtain a titanium cast product with little or no oxidation. Casting method for titanium castings. 2. In the method for casting titanium castings described in claim 1, when the casting mass of the titanium casting material is reduced and this small mass of the titanium casting material is cast into the titanium casting mold. , by rapidly cooling the mold, at least the part of the titanium casting mold made of magnesia molding material that comes into contact with the titanium casting material, the oxide production energy of the titanium casting material is absorbed by the magnesium when magnesia is produced. A method of holding the temperature from the beginning or cooling it quickly to a temperature that is greater than the energy of oxide formation. 3. In the method for casting a titanium casting product as set forth in claim 1 or 2, at least when the molten titanium casting material is poured into the titanium casting mold, the titanium casting mold is heated by a cooling means. How to cool. 4. In the method for casting a titanium casting product as set forth in claim 3, a method in which a refrigerant passage is formed in the wall of a titanium casting mold, and the titanium casting mold is cooled with a refrigerant passing through the refrigerant passage. . 5. In the method for casting a titanium casting product as set forth in any one of claims 1 to 4, the oxygen-free atmosphere in the place where the titanium casting material is melted and cast is
A method using an inert gas atmosphere. 6 Any one of claims 1 to 4
In the method for casting titanium castings described in 2. above, a vacuum atmosphere is used as an oxygen-free atmosphere in the place where the titanium casting material is melted and cast. 7 Any one of claims 1 to 6
In the method for casting titanium castings described in 1., a titanium casting mold made of magnesia molding material is preheated and expanded with a heating device, and then molten titanium casting material is poured into the titanium casting mold after casting. A method of reducing the degree to which a titanium casting product becomes smaller than a casting master mold due to contraction during solidification and cooling of the material by large preheating expansion of a titanium casting mold made of magnesia molding material. 8 Any one of claims 1 to 7
In the method for casting titanium castings described in section 1, a method of manufacturing a titanium casting mold by kneading magnesia mold material in water, shaping it, and heating it to increase its strength. 9 Any one of claims 1 to 8
In the method for casting titanium castings described in Section 1, the crucible is made of a steel material made of pure copper or an alloy containing copper as a main component, and is formed into a thick-walled material having a large mass relative to the volume of the material chamber,
When a titanium casting material is melted in this large-mass copper material crucible, the thermal energy transferred from the molten titanium casting material to the crucible is immediately transferred to each part of the wall of the large-mass copper material crucible. Moreover, by dispersing it over a wide range, the rate of temperature rise in the part of the crucible that comes into contact with the titanium casting material is greatly reduced, and the molten titanium casting material is removed from the crucible before the part of the crucible reaches the melting temperature. How to finish pouring into a titanium casting mold. 10 Any one of claims 1 to 8
In the method for casting titanium castings described in item 1, the crucible is manufactured from a carbon material made of pure carbon or a substance whose main component is carbon, and the titanium casting material is melted in the crucible made from the carbon material. 11 Inside the main body of the casting machine, a melting chamber and a casting chamber are placed vertically with a wall between them to form an independent airtight structure. A device is installed in the casting chamber in airtight communication with the titanium casting mold through hole, and the titanium casting mold is made of pure magnesia or a magnesia mold material whose main component is pure titanium or titanium. A titanium casting material made of an alloy is placed in a crucible, the melting chamber, casting chamber, and titanium casting mold are filled with inert gas to maintain an inert gas atmosphere, and the titanium casting material is placed in the crucible using a melting device. The melting chamber is kept at a higher pressure than the casting chamber, and the inert gas continues to flow from the melting chamber through the pouring hole and the titanium casting mold, and the titanium casting material is melted in the crucible by the melting device. dissolve,
The molten metal thus obtained is placed in an inert gas atmosphere from the crucible and poured into the titanium casting mold through the pouring hole, and then compressed by the differential pressure between the melting chamber and the casting chamber to oxidize the titanium casting material. From the beginning, at least the part of the titanium casting mold made of magnesia mold material that comes into contact with the titanium casting material is heated to a temperature at which the energy for producing magnesium oxides is larger than the energy for producing oxides of magnesium when magnesia is produced. By holding or cooling rapidly, the titanium foundry material cast into the titanium foundry mold undergoes little or no bonding reaction with the oxygen in the magnesia mold material forming the titanium foundry mold. A method for casting a titanium cast product made of pure titanium or an alloy mainly composed of titanium, which is characterized in that a titanium cast product with little or no oxidation is obtained in this way. 12 In the method for casting a titanium casting product described in claim 11, when the casting mass of the titanium casting material is reduced and this small mass of the titanium casting material is cast into the titanium casting mold, By rapidly cooling the mold, at least the part of the titanium casting mold made of magnesia molding material that comes into contact with the titanium casting material can be cooled to absorb the oxide formation energy of the titanium casting material from the magnesium when magnesia is produced. A method in which the temperature is maintained from the beginning or quickly cooled to a value greater than the oxide formation energy. 13. In the method for casting a titanium casting product according to claim 11 or 12, at least when the molten titanium casting material is poured into the titanium casting mold, the titanium casting mold is cooled by a cooling means. how to. 14. The method for casting a titanium casting product as set forth in claim 13, in which a refrigerant passage is formed in the wall of a titanium casting mold, and the titanium casting mold is cooled with a refrigerant passing through the refrigerant passage. 15 In the method for casting a titanium cast product according to any one of claims 11 to 14, a tap hole is formed in the bottom wall of the crucible, and the tap hole is closed with a titanium casting material. Then, the titanium casting material is melted in order from the top using the melting device in the crucible, and when all of the material is melted, the tapping hole is no longer blocked, and the molten metal is tapped out from the tapping hole, passing through the pouring hole to start titanium casting. A method of being cast into a mold. 16 In the method for casting a titanium casting product as set forth in claim 15, the molten metal in the crucible is tapped out from the tap hole by its own weight while maintaining the same pressure in the crucible sandwiching the tap hole and in the tap hole. Method. 17. In the method for casting a titanium cast product according to any one of claims 11 to 16,
A crucible made of pure copper or an alloy containing copper as a main component is formed into a thick wall with a large mass relative to the volume of the material chamber, and a titanium casting material is When melting the titanium casting material, the heat energy transferred from the molten titanium casting material to the crucible is quickly and widely diffused to each part of the wall of the crucible made of a large mass of copper material. A method that significantly reduces the temperature rise rate of the part that comes into contact with the crucible, and finishes pouring the molten titanium casting material from the crucible into the titanium casting mold before the crucible part reaches the melting temperature. 18. In the method for casting a titanium cast product according to any one of claims 11 to 16,
The crucible is pure carbon or has carbon as its main component. A method of melting titanium casting material in a crucible made of carbon material. 19 In the method for casting a titanium cast product according to any one of claims 15 to 18,
A method that uses an arc melting device as the melting device, places a shear arc electrode facing the titanium casting material from above, generates an arc between the arc electrode and the titanium casting material, and melts the casting material from above. 20 In the method for casting a titanium cast product described in any one of claims 11 to 18,
A method of melting titanium casting materials using a high-frequency melting device as the melting device. 21. In the method for casting a titanium cast product according to any one of claims 11 to 20,
By preheating the J mold for titanium casting made of magnesia mold material with a heating device and expanding it, and then pouring the molten titanium casting material, the titanium casting material shrinks during solidification and cooling after casting. A method of reducing the degree to which a titanium casting product becomes smaller than a casting master mold by preheating expansion of a titanium casting mold made of magnesia molding material. 22. In the method for casting a titanium cast product according to any one of claims 11 to 21,
A method of manufacturing titanium casting molds by kneading magnesia molding material with water, then heating it to increase its strength.