US2294161A - Flame hardening - Google Patents

Description

Aug. 25, 1942. J, 1 ROwE 2,294,161

FLAME HARDENING Filed DSC. l0, 1940 ZZ' l FLL' gul,

v INVENTOR.

\\\\\\\\\\\\\\\\\\\\\\\\\ BY @1W l y ATTORN Patented Aug. 25, 1942 UNITED sTATEs PIATENr orFicE FLAME I 1 t DEN-ING .lohn J. Crowe, Westfield, N. 3., assigner to Air Reduction Company, lncorporated, New York, N. Y., a corporation of New York Application December 1o, 1940, serial No. 369,394

(ci. 14s-r9.9)

7 Claims.

This invention relates "to flame hardening, and more particularly to the control of the depth of the hardening, especially with Work-pieces of variable section.

Since the surface metal is heated quickly and steep temperature gradients are produced in the metal of the work-piece during name hardening operations, the mass of metal to which heat is 'lost by conduction seriously influences the remore severe .because of the` higher temperature of the metal and the hardening operation therefore more effective. In order to prevent such variations in hardness and depth ofhardness, it has been proposed'to change the amount of heat put into the metal in such a way as to compensate for the variation in conduction losses.

It is an object of this invention to prov'ide a simplified method and apparatus for controlling ing section, and more especially for obtaining uniform hardening of such work-pieces.v With this invention the hardening operation is controlled by regulation of the quenching jets, preferably by changing the velocity and volume of quenching uid in accordance with changes in heat losses to the underlying metal. The amount of heatl supplied is su'icient to heat the metal at the regions of greatest thickness and the supply of quenching uid is made to vary'inversely with the conduction losses from the surface metal to the metal below the surface.

'Ihere is rapid and substantial transfer of heat through the lmetal from the region under the names to the region cooled by the quenching jets. An increase in the supply and velocity of quenching uid causes an increase in the heat,

ow from the region of the names. A decrease in the quenching uid makes the temperature gradient between the heating and quenching regions less steep and causes a reduced heat flow.

With this invention the supply'of quenching fluid is increased when the torch operates on thinner sections to counteract the reduced conduction losses to underlying metal. When the section under the torch is thicker, the volume and ltion.

compensate for the larger conduction losses to the increased mass of metal under the heating torch.

Although this invention can be used in com- `bination with other expedients for obtaining uniform Vuncontrolled hardening at diierent regions of a work-piece, it is not ordinarily neces-v -sary to use any variation in heat or other expedient with the Variable quench of this inven- It is a feature of the invention that a uniform supply of heat can be maintained as the hardening operation progresses along the work-piece, and the variations in conduction losses are compensated for by variations in the quenching fluid supply.

Such a control of the hardening by regulating the quenching uid is simple and has certain y advantages over heat variation in that there 'is -flame hardening results on work-pieces of varyonly one,y quenching Huid supply` line whereas there are two gases, and quenching fluid can be discharged at any desired velocity whereas most heating torches operate best at only one gas pressure, and if the velocity of gas discharge is much reduced the torch will fiash back.

The invention will be described as applied to the hardening of one face of a4 work-piece. In speaking of hardening the face of the piece it should be understood, however, that the term face is used to denote not only the actual surface metal but also the layer of metal immediately below the surface.

. ing fluid control valve andcam 'low' part of the cam. Y

for flame hardening a work-piece in accordance y with this invention. Fig. 2 is an enlarged view, partly in section,

Vshowing the heating torch, quenching head,r and -control valve of Fig. 1.

Fig. 3 is an enlarged detail View of the quenchoperating mechajism, shown in Fig. 1,

Fig. 4 is a. sectional View, taken on'the line 4-4 of Fig. 3, but with the cam-follower on a A supporting -means comprising a torch car-v riage l0 has four wheels tl that run on 'a track l2. The carriage is self-propelled, being driyen by a governor-controlled motor Il that is connected with the front wheels of the carriage hyv suitable reduction gearing, not shown, but well velocity of the'quenching uid is reduced to 55 understood the'art.

A torch holder I6 is supported by a universally adjustable bracket I1 that has a clamp I8 securing it to a post I9 that extends upward from the front end of the carriage.v 'A torch 6| in the torch holder I6 is supplied with oxygen and fuel gas, preferably-acetylene, through separate hose `22 and 23, respectively. The supply of gas fromv these hose is controlled by valves 22' and 23'.'

, be adjusted with respect to the elbow 26 to bring the torch into position with the rows of orices 26 lin the tip face extending at right angles to the direction of movement of the tip as the carriage Il travels along the` track I2.

A quenching head 3| is positioned close behind .the heating torch and supported by abracket 32 whichV is ultimately supported from the carriage. In the illustrated apparatus, the

bracket 32 is attached to the extension tube 24 of the torch by a clamp 33, and the bracket 32 is slightly oiset so as to locate the quenching head 3| .directly behind the heating torch 21. The clamp 33 can be shifted lengthwise along the extension tube 24 to change the spacing of the quenching head 3| lfromthe heating torch 21.

Fig. 2 shows the quenching 4head 3| in section.

A common distributing chamber 34 supplies cool` ing uid to a row of jet. passages 35 that are ,of reduced diameter at their lower ends where they open through the bottom face of the quenching head. The cooling uid, which is' preferably water, is supplied to the quenching head through a supply line comprising a tube or conduit 36 commanded by a valve 31 in `a housing 38 attached to the side of the carriage I0. The water discharges from the quenching .head 3| in quenching jets 39. y

A valve stem 46 extends through a stuilingbox in ythe bottom wall of the housing 38. The valve 31 is urged toward closed position by a spring 4|, and is opened by a lever 42 which is cam-operated. One end of the lever 42 is connected by a pivot 43 to lugs on the valve housing 38. A cam-follower roller 44 at the other' end There, is a dierent cam 46 for every diierent shape of work-piece that the apparatus is called upon to harden. The contour of the cam 46 shown in Fig. 1 is designed for the workpiece 6|.

The hardening operation is started by bringing the carriage I0 into position to locate the tip v21 over the left end oi` the Work-piece 5| with able the heating flames to raise the metal over which they pass to a temperature well above the critical temperature of the metal. By the time the quenching head 3| reaches the work-piece 5| the roller` 44 has reached the cam 46 and been displaced by the steep rise at the left end of the cam. This movement of the cam-follower opens the valve 31 and supplies cooling fluid at `quench the work-piece, but to Withdraw conofthe lever- 42 rolls on a cam 46 extending along the side of the track and preferably attached to head 3| reaches a region where the thickness of the work-piece changes, it is necessary that I.the work-piece be accurately positioned with respectto the cam. A limit stop 62 connected with the work table 50 by bolts 53 serves to position the work-piecev accurately with respect to the cam 46. The bolts 53 extend through a slot 54'in the work table sothat theposition of the stop 52 can be adjusted for anychanges in the spacing of the quenching head 3| from the carriage I6 when the clamp 33 is movedl lengthwise along the extension tube 24'.

siderable heat from the region under the torch where the section is relatively thin and conduction losses limited accordingly,

When the torch 21 reaches the web just beyond the center ofthe work-piece 5|, the supply of quenching iiuid is reduced by a drop in the cam 46. The reduced cooling by the quenching jets-oisets the increased cooling by the addi. tional conduction losses into Aunderlying metal at the region over the web.

As the torch 21 passes beyond theweb, the quenching uid supply is increased by a slight rise in the cam 46, but since the section is considerably thicker than that ahead of the web, the quenching uid supply is less than that used before the torch 21 reached theweb.

Near the end of the work-piece where there is little metal ahead of the torch into which heat can ow, the supply of quenching fluid 'is increased to a maximum in order to compensate for reduced heat ow into metal ahead of the torch by increasing the heat iiow toward the region of quenching.

'Ihus the displacement contour of the cam 46 is so related to the variations in the thickness of thev metal under the top surface of the workpiece 5| that the supply of quenching uid (and consequent velocity or strength of the quenching jets 36) varies in accordance with changes in the thickness of the work-piece. Since conduction lossesV from the face that is heated are greater in proportion to the mass of metal below the surface, the cam operation described changes the .supply of quenching fluid inversely with changes in the thickness of the Work-piece. Any` change in the right direction is benecial in that it makes the hardening results more uniform, but as in the case of all flame hardening operations, the actual numerical values for gas pressure, carriage speed, and water pressure for best results depend upon so many interrelated variables that their determination must be largely empirical in accordance with practices well known in the art.

'Ihe envelope gases from the heating iiames ow over the work-piece and blanket'the surgressively along the length of said surface by face between the heating iiames and quenching jets so that the hot metal is protected from lthe atmosphere.

The invention is not limited to the embodiment described, various changes and modifications can be made, and some features of the invention can be used without others.

I claim:

1. The method of producing a more uniformly hardened face on a work-piece that is of variable thickness below said face and of material that can be hardened by cooling quickly from above a criticaltemperature, which method comprises heating the face to be hardened by means of heating fiames applied progressively to the face .in a manner that supplies substantially equal heat input to the regions of different thickness, directing jets of ,quenching fluid against the heated face close behind the progressivelyapplied heating flames, and reducing the quench at regions where greater thickness of the metal causes larger heat loss by conduction.

2. The method of ame hardening a workpiece that is made of material that can be hardened by cooling quickly from above a critical temperature, which method comprises moving a system of heating flames progressively across the part to be hardened followed by a system of quenching jets, and compensating for variations in the heat loss `by conduction at sections of different thickness by changing the velocity of the quenching jets inversely with changes in the conduction losses to the metal adjacent the lheating of metal that can be hardened by moving heating y ames progressively across the face to be hardened to raise the metal above a critical temperature, followed by quenching jets close behind the heating jets, the improvement which comprises controlling the hardening by varying the supply of quenching fluid to said jets inversely with the variations in the conduction losses from the surface metal against which the heating fiamesare directed.

4. 'Ihe methodof flame hardening a workpiece that is of different thickness at different regions lengthwise of the surface to which heating names and quenching jets are applied and of material that can be hardened by cooling quickly from above a critical temperature, which method comprises heating the work-piece promoving a constant number of uniform heating flames at substantially uniform speed, following said heating flames with quenching jets directed against the heatedwork-piece close behind the heating flames, and regulating the supply of quenching uid to the jets, during the progression of the quenching jets, in accordance with changes in the thickness of the Work-piece.

5. In the flame hardening of a metal work-piece that is heated above a critical temperature by flame jets which are moved progressively across lthe surface of the work-piece but which leave the metal a short distance behind them at various temperatures at different regions across the work-piece because of variations in conduction losses resulting from differences in the mass of metal below the heated surface, the improvement which comprises cooling the metal quickly from above its critical temperature by progressively applying quenching jets to the work-piece close behind the heating flame jets and controlling the quenching jets to cool'the metal more at the regions where the conduction losses to the' underlying metal of the work-piece are the least.

6. Flame hardening apparatus including in combination a carriage movable along a support, means forsupporting a work-piece in a fixed position with respect to the carriage support, a heating torch and a quenching header supported by the carriage, a conduit through which quenching uid is supplied to the header, a valve on the carriage commanding the conduit, a cam-follower on the carriage for operating the valve, a cam extending for considerable distance along the course of movement of thecarriage in position to operate the cam-follower and valve to adjust the rate of flow of quenching fluid to the header, and means holding the cam in a fixed position with respect to the work-piece,l said position being correlated with the distance of the cam-follower from the -quenching header so that longitudinal displacement of the cam-follower along the cam corresponds to displacement of the header over a predetermined section of the workpiece.

'1. Apparatus for dame hardening as described in claim 6 with adjustable means for determining the spacing` of the quenching header from the heating torch.

v. JOHN J. CROWE.

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