US3268370A - Method and apparatus for heat treating - Google Patents

Description

Aug. 23, 1966 L. B. KIMBROUGH METHOD AND APPARATUS FOR HEAT TREATING 2 Sheets-Sheet 1 Filed Dec. 30, 1965 7 6 2 J P M Q F n 5 WV" FAD J'- 4 c A. a 1 wH 6" Q i E w a vTw m ax .M a F 0 mm .m A m INVENTOR Laurence B. Kimbrough WITNESSES Aug. 23, 1966 B. KIMBROUGH METHOD AND APPARATUS FOR HEAT TREATING 2 Sheets-Sheet 2 Filed Dec. 30, 1963 Fig.4.

I Ill/III 71/1] Ill/Ill United States Patent 3,268,370 METHOD AND APPARATUS FOR HEAT TREATING Laurence B. Kimbrough, Baltimore, Md., assignor to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed Dec. 30, 1963, Ser. No. 334,260 9 Claims. (Cl. 148-16) The present invention .relates to method and apparatus for heat treating, and more particularly to such method and apparatus involving induction heating of .a metal workpiece surface while in exposure to a select fluid environment.

The select fluid environment is chosen according to the result desired, such as prevention of oxide formation, surface cleansing in a reducing gas,.carburization, etc. Techniques for maintaining such environment in surround of the heated workpiece surface have included the localized flowing of a gas over such surface, and the surrounding of such surface with a liquid. As previously practiced, such techniques have suffered from inefficiencies; the migration of air into the flowing gas, in the one case, and use of an excessive amount of induction heating power in evaporation and/ or heating of liquid surrounding the heated workpiece surface, in the other case.

In view of the foregoing remarks, it becomes an object of the present invention to provide an improved method and apparatus for induction controlled-fluid-environment heat treating, which overcomes the above-mentioned disadvantages of the exemplified previous techniques.

In accord with general features of the present invention, a workpiece surface is heated by induction heating coil means while a select gas is maintained in contact with such surface and while a pool of liquid is used as a seal against access of air to such surface.

In accord with a supplanting aspect of the present invention, where an immersion quench is suited to the desired heat treatment, the aforesaid pool of liquid may be made to serve as an immersion quench bath.

Other objects, advantages, and aspects of the invention will be made apparent in the following detailed description taken in connection with the accompanying drawings, in which:

FIGURE 1 is an elevation view, substantially in cross section, showing a novel apparatus operable to perform the novel method of the present invention; v

FIGURE 2 is a similar view of a modification of the apparatus of FIGURE 1;

FIGURE '3 illustrates an apparatus in conjunction with a particular surface of a workpiece having a configuration which affords its serving as container for the aforementioned pool of liquid, which assemblage is operable in accord with the novel method of the present invention;

FIGURE 4 is an elevation view, substantially in cross section, showing apparatus of the present invention as applied to horizontal-scanning heat treatment of a workpiece; and

FIGURE 5 is a section view taken along the line 4-4 in FIGURE 1 showing a detail of the heating coil means as exemplified in the apparatus of FIGURES 1, 2, 3 and 4.

Referring to FIGURE 1 in the drawings, in accord with the illustrative embodiment shown therein, an elongated workpiece 5, in the form of a rod or shaft, to be heat treated is arranged to extend vertically into a pool 6 of liquid,'such as water, for example, disposed in a vessel 7. An induction heating coil 8 is disposed in the pool 6 in encirclement of a longitudinal portion of the workpiece, together with a gas housing 9 in contiguous axialwise extension with respect to the heating coil 8.

The vessel 7 for the liquid pool 6 can take the form such assemblage.

pf an open-top cylindrical tank as illustrated in FIGURE l, or otherwise provide for the retention of a liquid pool 3,268,370 Patented August 23, 1966 "Ice while permitting insertion of a workpiece or/ and of heating coil and gas housing, according to convenience and/or requirement. In the FIGURE 1 exemplification, the configuration of the workpiece 5 is such as would permit the induction coil 8 and gas housing 9 assemblage to maintain a fixed position within the vessel 7, inasmuch as the workpiece 5 may be inserted axialwise into Other workpiece configurations might preclude such axialwise insertion and dictate need for radialwise insertion in a hinged or split form (not shown) of gas housing and heating coil, in which case the act of introducing the workpiece to such assemblage might better be carried out outside the vessel 7 and then inserted in toto thereinto.

The induction heating coil 8 as exemplified herein is of a single turn configuration of the water-cooled integralquench type having spaced-apart hollow leads 12 at a circumferential location on the coil. These hollow leads 12 serve the usual function of conveying energizing current, cooling water, and quench water to the coil. This particular coil configuration is particularly suited to the heating of a narrow longitudinal zone of a cylindrical workpiece, as chosen for example herein, and particularly to scanning of the workpiece by such zone by relative axialwise movement between workpiece and coil, while the workpiece is rotated for uniform circumferential induction heating efiect. Where the heat treating requires a rapid quench, as in surface hardening certain steels, for

example, a forced quench such as a water spray is delivered to the heated workpiece surface via spray ports 16 in the coil during the scansion of the workpiece. In accord with certain features of the invention, however, the heating coil may be of another configuration, scansion of the workpiece may not be involved, nor liquid quenching be involved. Per the illustrative examples shown herein, the split in the coil 8 in the region of the leads 12 may be filled with an electrical insulating material 17, FIGURE 5, to prevent flow of liquid from the pool 6 radially therethrough while immersed as in FIGURES 1, 2 and 3.

The gas housing 9 has a liquid-tight connection with the top of the heating coil 8 and extends vertically therefrom in spaced-apart encirclement of the workpiece 5 to a closure portion 19 at its upper end to define a clearanceway 20 which opens downwardly to the interior of the coil 8. The housing 9 is adapted for connection to a source of gas under pressure (not shown) via gas supply conduit means 22 and valve means 23, to avail the clearanceway 20 of such gas via an annular header chamber 24 and ports 25 located at the top of such housing. In the FIG- URE 1 showing, the upper closure portion 19 of the housing 9 comprises a sealing ring 27 for sealing contact with the peripheral surface of the workpiece 5 which is of such length as to extend upwardly beyond the housing 9. In the FIGURE 3 showing, the workpiece 5 is a short hollow cylindrical part, or hub, of a torque converter housing 30, and the closure portion 19 takes the form of a Wall which extends over the end of such part. The housing 9 at its area of connection to the heating coil 8 and within an area of inductive influence by such coil, is made of an electrical insulating material such as polypropylene. For sake of simplicity, the entire housing may be made of such material, as is indicated in the showing in the drawings. For reasons which hereinafter will become apparent, the effective clearanceway 20, including that within the coil 8, may be extended downwardly for a distance beneath such coil by the inclusion of a cylindrical-gas-housing-extension 32 secured in fluid-tight conneciton to such coil.

As aforementioned, one aspect of the invention relates to heating the surface of the workpiece to a temperature which is conducive of oxide formation when exposed to air and therefore a select fluid environment is maintained in surround of such surface when in such heated state to prevent such oxide formation. Referring to FIGURE I,

assume that the parts of the apparatus and the workpiece 5 are positioned as shown, and that the pool 6 of such as water is in existence within the vessel 7 at least to a height above the bottom of the gas-housing extension 32, or of the heating coil 8 if no such extension is employed. Assume also that the valve 23 is open for connection of the interior of the gas housing 9 to a source of inert gas, such as argon or nitrogen, for example, and that such interior previously has been purged of air so that only the inert gas is present in the clearanceway in surround of the outer surface of the workpiece within the region of heatability by the induction coil 8. In accord with the present invention, the liquid of the pool 6, water, for example, in extending to a height above the bottom end of the gas-housing-and-heating-c-oil assemblage 8, 9 acts as a seal which prevents migration of atmospheric air into clearanceway 20 to the workpiece surface to be heated. At the same time, once having purged such clearanceway of air, as by displacement with flow of inert gas thereinto, the liquid in surround of the gas-housing-and-heating-coil assemblage 9, 8, in accord with one aspect of the present invention, may be prevented from entering the interior of such assemblage by merely maintaining a gas pressure, slightly greater than that created by the liquid of pool 6 extending above the bottom of the assemblage. Actually there can be flow of the inert gas under these circumstances, and such flow serves as further assurance that such gas-present liquid-free condition persists. An indication thereof may be obtained by the presence of bubbles 34 rising to the surface of the pool 6. In the horizontal arrangement of FIGURE 4, such gas flow is necessary, since a mere static pressure Will not prevent migration of liquid into the open end of the clearanceway 20.

During the existence of the above-described gas-present liquid-free condition, the induction heating coil 8 will be energized via leads 12 to cause induction heating of a portion of the workpiece 5 disposed therein. At the same time, per the usual practice in accord with the illustrative configuration of heating coil and workpiece, the workpiece may be rotated about its axis within the seal 27 of the gas housing 9 Without disturbance to the gas-present liquid-free condition in immediate presence of the heated workpiece surface. Such condition will be maintained so long as the temperature of such workpiece surface remains critically high with respect to oxide formation. Slow cooling of the heated workpiece surface may be arrived at by de-energization of the heating coil 8 and such as heat transfer via conduction to the liquid pool 6 and radiation to the liquid-cooled coil. After which cooling, the valve 23 will be closed and the workpiece, with its heat treated area, removed from the apparatus. Where immersion in a liquid bath quench is desired for the heated area of the workpiece, as in hardening certain steel alloys, for example, the liquid of the pool 6 can serve as such bath by permitting such liquid to rise upwardly through the clearanceway 20 to quench the heated workpiece surface. This can readily be arrived at by operation of the valve means 23 to establish connection of the gas housing 19 to an atmospheric vent port 38 in lieu of the gas supply; it being understood that the level of the liquid in pool 6 will need be at a height suificient to cause such rising to the desired height within the clearanceway. Where a forced quenching of the heated surface of the workpiece is required for completion of the desired heat treatment, as'in hardening of certain other steel alloys, a liquid spray of such as water is directed onto the heated surface via the spray ports 16, for example, in the exemplified integral-quench heating coil 8.

Where the workpiece 5 is scanned by the heating coil 8 for extension of the heated zone along the axis of such workpiece, it will be appreciated that the gas housing 9 will follow the movement of the coil to maintain the heated surface in surround by the select gas and the liquid of the pool 6 will follow such movement to maintain the air-excluding seal for the gas at the bottom of the moving coil or/and effect progressive quenching of the succeeding portions of the workpiece which become exposed to such liquid as the coil moves to simultaneously heat the advancing preceding surfaces. sion type quench and the forced or spray quench, the gashousing-extension 32 can serve, where desired, to keep the liquid-surrounded portion of the workpiece more remote from the portion being heated within the coil 8.

In the exemplified showing in FIGURE 1, it will be apparent that scanning of the workpiece 5 by a'heated zone can best be effected by movement of the coil-andgas-housing assemblage 8, 9 while the workpiece remains fixed in position within the vessel 7. Where it may be desirable to instead move the workpiece relative to the coil-and-gas-housing assemblage 8, 9, arrangements such as shown in FIGURES 2 and 4 may be employed. In the FIGURE 2 arrangement, the vessel 7 may be provided with an opening 40 at its bottom through which the workpiece 5 may extend for accommodating vertical movement relative thereto and to the coil-and-gas-housing assemblage 8, 9 therein. A resilient annular seal 41 mounted interiorly of the opening 40 provides for retention of the liquid of the pool 6 by slidable sealing cooperation with the exterior of the workpiece. In the FIGURE 4 arrangement, the workpiece 5 may be moved horizontally and axialwise through the coil-and-housing assemblage 8, 9 via a movable workpiece support means 42a driven by such as a screw-threaded rotary shaft 4212. In accord with yet another aspect of the invention, a liquid such as water is used to effect initial displacement of air associated with the workpiece prior to introduction of the select gas, thereby to realize conservation of such gas which otherwise would need be utilized in excess in order to realize such displacement. Referring to FIG- URE 3, for example, this concept is utilized where the hub portion 5 to be heat treated is of hollow configuration. Prior to introduction of the gas housing 9, the bottom of th hub is closed and sealed by a plug 43 and the interior of such hub is filled with water. Following this, the encircling annular well of the workpiece in form of a torque converter housing is filled with water to constitute the pool 6. The gas-housing-and-coil assemblage 9, 8 is then lowered onto and around the hub portion to be heat treated. By opening the top of the gas housing 9 to the atmosphere at this time, as by use of the valve 23, water from. the pool 6 will rise upwardly into the interior of such housing and effect displacement of the air therein to the extent permitted by the depth of such pool, thereby further assuring the purging of the interior of the gas housing of air in order to assure surround by select gas of the workpiece surface to be heated by the coil 8. In the FIGURES 1, 2 and 4 embodiment, an even greater liquid purging can be realized. Here, by virtue of the depth of the pool 6, the entire interior of the gas housing 9 can be filled with the liquid from the pool to displace the .air initially therein. Subsequent to this, the liquid within the housing 9 will then be displaced downwardly by admittance of the select gas thereinto via valve 23, fluid pressure conduit means 22, and the annular header chamber 24, as previously described. From the foregoing it will be apparent that there has been disclosed an improved method and apparatus for controlled-fluid-environment heat treating.

While there have been shown and described what are at present considered to be the preferred exemplifications of the invention, modifications thereto will readily occur to those skilled in the art. It is not desired, therefore, that the invention necessarily be limited to the specific arrangements and steps described and shown, except as are embraced in the appended claims, and it is intended Both in the bath immer-.

to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

I claim as my invention:

1. A method of heat treating a workpiece involving heating of a surface of such workpiece by induction heating coil means proximate thereto while such surface is exposed to a select gas environment, comprising the establishing of a liquid pool environment in surround of the induction heating coil means and of the portion of the workpiece having the surface to be heated, and causing such select gas to displace the liquid away from said workpiece surface while heating same by energization of said heating coil means.

2. A method of heat treating a workpiece as set forth in claim 1, wherein the workpiece surface is to be heated and quenched and the liquid of the pool is caused to come into contact with the heated workpiece surface for immersion quenching thereof.

3. A method of heat treating a workpiece comprising directing a select gas onto the surface of such workpiece while heating same inductively, and employing a liquid pool in a manner serving as a seal against migration of atmospheric air to the workpiece surface While in its heated state and in the presence of said select gas.

4. A method of heat treating a workpiece comprising establishing a liquid environment in surround of the surface of the workpiece to be heated, causing a select gas to displace the liquid away from such surface, and heating said surface inductively in the presence of said select gas while it maintains displacement of the liquid.

5. Apparatus for heating a workpiece surface while in exposure to a select gas, comprising means defining a pool of liquid for surround of the workpiece surface, induction heating coil means disposed in said liquid in inductive coupling relationship with said workpiece surface for heating same, and means for directing a select gas onto said workpiece surface in displacement of said liquid while said surface is in a heated state.

6. The heating apparatus of claim 5, further including means for effecting scanning of said workpiece surface by said heating coil means and by the select gas directing means.

7. Apparatus for heating a peripheral workpiece surface while in exposure to a select gas, comprising an induction heating coil for encirclement of such surface to inductively heat same, a cylindrical gas housing means for encirclement of said surface and cooperation with said heating coil to direct a flow of select gas onto the workpiece surface disposed within said heating coil, and means for defining a pool of liquid to seal against migration of atmospheric air onto the heated workpiece surface in the presence of said select gas.

8. The apparatus of claim 7, wherein said gas housing means includes a mechanical sealing means for cooperation with said workpiece to cause such select gas flow to be unidirectional.

9. Apparatus for heat treating a workpiece surface, induction heating coil means for inductively heating said surface, gas housing means for directing a select gas onto such surface while being so heated, and vessel means for containing a pool of liquid extending to a level above said heating coil means and gas housing means.

References Cited by the Examiner UNITED STATES PATENTS 3/1963 Chang 14820.3 X 8/1965 Snoue l4820.3

Claims (1)

1. A METHOD OF HEAT TREATING A WORKPIECE INVOLVING HEATING OF A SURFACE OF SUCH WORKPIECE BY INDUCTION HEATING COIL MEANS PROXIMATE THERETO WHILE SUCH SURFACE IS EXPOSED TO A SELECT GAS ENVIRONMENT, COMPRISING THE WESTABLISHING OF A LIQUID POOL ENVIRNOMENT IN SURROUND OF THE INDUCTION HEATING COIL MEANS AND OF THE PORTION OF THE WORKPIECE HAVING THE SURFACE TO BE HEATED, AND CAUSING SUCH SELECT GAS TO DISPLACE THE LIQUID AWAY FROM SAID WORKPIECE SURFAE WHILE HEATING SAME BY ENERGIZATION OF SAID HEATING COIL MEANS.

Images