US2321806A - Process of heat treating - Google Patents

Description

June 1943- E. G. GILBERTSON PROCESS OF HEAT TREATING Filed Aug. 29, 1941 'FIG.3

INVENTOR. ELMER G. GILBERTSON d TTORNEY.

YBYJM Patented June 15, 1943 UNITED STATES PATEN -osmosrnocass 02 21: 'mna'rma 4 Elmer G.Gilbertson, Des Plaines, Ill., assignor to Teletype Corporation, Chicago, Ili., a corporailon of Delaware Application August 29, 1941, Serial No. 408,753 8 Claims. (Cl. 148-15) example, in the case ofcertain-surfaces or edges which are to be subjected to excessive wear, it is desirable to obtain a high degree of hardness whereas in certain other portions of said parts which might during use be subjected to strain, it is desirable to obtain the characteristic of relative toughness rather than hardness.

Accordingly. a principal object of the present invention is the provision of a method of treating ferrous piece parts whereby there may be obtained in single piece parts two varying conditions of hardness through the practice of but a single tempering operation.

There is proposed-herewith a practice whereby small or medium sized piece parts may be heat treated through the practice of a single tempering operation which will ermit the attainment of a dual condition; namely, with certain portions of the piece parts hardened to an extreme condition and with other portions thereof relatively soft and tough in contrast with the degree of hardness afore-mentioned.

instead be removed and the piece parts quenched by complete immersion within a quenching fluid. For a. more comprehensive understanding of the present invention, reference may be had to the following detailed specification and to the accompanying drawing wherein similar reference characters designate corresponding parts throughout and wherein;

Fig. l is a transverse sectional view through a processing furnace for containing a molten bath of heat treating fluid and illustrates specifically the suspension of carbon blocks upon the surface of the bath;

Fig. 2 is aperspective view of a carbon block which has been processed so as to accommodate typical piece parts within the contemplation of the instant invention; and

Fig. 3 is a perspective view of a modified form of carbon block processed for another adaptation of the present invention.

In the practice of the instant invention certain well-recognized principles heretofore known in tain a surface Briefly stated, the foregoing and other objects of the present invention are obtained by a practice of embedding those-portions of the piece parts to be excluded from attaining an extreme hardened condition within suitably formed recesses in a protective block constructed of carbonaceous material. While supported in this condition the piece parts with non-excluded portions protruding downwardly beyond the protective region of said carbon block, are floated upon the surface of a heat treating bath of molten cyanide whereby there is imparted a degree of carburization as well as the proper heat characteristics to said protruding portions of said piece parts. The carbonacecus block has a lower specific gravity than the molten cyanide and accordingly, it is floated on the surface thereof. The portions of said piece parts which are permitted to protrude beyond the protection of the carbon extend into the bath, and following the heat treatingprocess Fig. 1. which is then heated to melting or about followed to a limited extent.

the heat treating of ferrous piece parts may be For example, in the hardening of low carbon content iron or steel piece parts, it is recognized that in order to obhardness of sufllcient depth, the piece parts are preferably immersed in a molten bath of carbon containing cyanide salts and that the period of immersion is regulated in propor" tion to the depth of carbon saturation to be imparted to said piece parts. Again, with steel parts which do contain a fair degree-of carbon as a part of their composition, the heat treating procedure may be one'which requires only that the piece parts be heated to a proper temperature following which they may be quenched in a cooling fluid or in air in order to obtain a hardness in whatever degree may be desired.

Accordingly, and since the particular features of the present invention do not concern themselves with the nature of the steel piece parts nor wiih the particulars of the heat treafment except that in preference to a solely atmospheric heating medium, it is deemed more advantageous to utilize a fluid heating medium in order that the carbon supporting block may be floated on the surface of the molten medium. It is proposed that a crucible or container il' be filled to a de-' sired depth with salt I! such as sodium cyanide.

The temperature of the bath may be maintained at any heat variation from about 1250 F. to 1650 F. depending on whether the bath is to be utilized as a carburizing agency in addition to a heat exchange medium. Where the piece parts are of simple form or of drawn material such as the pins i3. and where such piece parts are to be hardened at one end and shielded from hardening at the other end, as in the case bf the cyiindricalmaterial illustrated, it is but necessary to obtain a single carbon block it of appropriate dimension and to drill through one surface of and floating the assembly upon the surface of the sodium cyanide bath I! after the manner illustrated at the right-hand side of Fig. 1.

While the block i4 may be press formed or molded of coke-carbon or graphite material, as is well-known in the construction of kindred heat treatment apparatuses used in other processes, it is to be understood, nevertheless, that the essential characteristics of the block which make it especially appropriate to the practice of the instant invention,-is its quality of imperviousness to the effects of the heating bath and also its preferably lower specific gravity as compared with that of the molten cyanide l2 so that the block M will be floated on the surface of the bath as indicated in Fig. 1 rather than to submerge into the bath, although conceivably if asubstance otherwise suitable partakes of the latter conditions, means may be provided to support the' block, as by the use of a suspension wire, during the period of immersion.

In accordance with the practice illustrated in Fig. 2 of the accompanying drawing, it has been found that the enveloped or shielded portions of the pins i8 are sufficiently protected by the block H to insulate them against obtaining a heat or temperature equivalent to that of the exposed or immersed portions of the pins l3. Accordingly, when following the period of exposure, the pins H are removed from the block I! for quenching or drawing, or if preferred where the pins l3 together with the block I are immersed for treating manufactured quenching in a fluid, it is found that solely the exposed portion of the pins l3 will attain a certain degree of hardness whereas the protected portions of said pins l3 will, by reason of their lower degree of heating, remain with but a slight condition of change and in any event considerably different from the exposed portion.

To accommodate for unusual'conditions of piece parts as where the shapes are of such irregular and special conformation, it is proposed that instead of a single block ll, two cooperating blocks 'IB and i5a may be employed having formed on the engaging surfaces therebetween appropriate recesses such as It, in conformity with those portions of the piece parts ll, which have been designated Ila, in Fig. 3 and which are to be protected from exposure. Accordingly, the remaining portions of the piece parts H such as those indicated extending outside the blocks l5 and Na will upon immersion into the bath i2, Fig. 1, be permitted to extend into the sodium cyanide and obtain a heating in excess of that obtainable by the protected portion l'la.

xF'Ol' the purpose of accommodating specially in the hereunto shaped. piece parts If, it is contemplated that the blocks II and "a be molded in accordance with the practice known in the formation of these blocks so as to provide them with the necessary recesses in advance of the processing herein described, or where this practice is not feasible, it is proposed that the blocks i5 and Ila may be processed by machining the necessary depressions I! in the cooperating surfaces thereof at any time in advance of the herein described processing. One of the features to be noted in the provision of blocks l5 and Ilia, after the manner disclosed in Fig. 3, is the facility whereby the piece parts l'l may thereafter be removed notwithstanding the fact that the irregularity of their protected portions might ordinarily not permit the ready withdrawal thereof, contrasting from the pins II, which may be withdrawn subsequent to their exposure by the simple process of exerting a pull force upon them. To remove piece parts such as the one indicated l1 from between a pair of blocks I5 and l5a it is necessary but to separate the blocks and to lift the piece part from its residence in one or the other of said blocks.

It is to be noted further that in the case of either type of block II or IE and l5a, it is contemplated to suspend those portions of the piece parts, which are to be treated, downwardly. This not only conforms with the particular utility of the practice but also facilitates the proper balancing of the assembled parts with respect to their blocks so that the lowermost portion is heaviest and thereby there may be maintained the proper floating relationship as illustrated in Fig. 1.

Through the afore-described practices, there i is obtainable a method of partially or locally heat piece parts in large quantity by a single exposure operation effective upon a plurality of piece parts or by immersion of said plurality of piece parts by a single operation within a bath of heat communicating material such as sodium cyanide, etc. In contrast with the practice of singly treating dividually exposing them to a flame, it is to be noted that not only is there effected a considerable savings in time through the economy of a single operation which heretofore required a number of individual operations but also through the practice above described there is obtainable a more exact condition uniformly applied throughout all of a large number of piece parts to be thus treated. a l

Since the present invention .has been explained and described with reference to particular illustrations, it is to be understood, that numerous modifications and variations of practice may be instituted without departing from the spirit or scope thereof. Accordingly, it is not intended to be limited to the particulars of the foregoing specification, nor to the specific illustrations in the accompanyfng drawing except as indicated appended claims.

What is claimed is:

1. A method of heat treating or tempering llOl'l piece parts which consists in the steps of forming recesses in a block of protecting material conforming in shape to the shape of such portions of said parts which are to be excluded from heat treatment, inserting said parts into said recesses, placing the parts and block on the surface of a molten bath of sodium cyanide salts, removing said parts and block from the surface of said bath after a predetermined period of exposure, and quenching said parts so as to effect a the piece parts by inhardening of the exposed ortion of said parts to the exclusion of the protected portions thereof.

2. A method of treating ferrous piece parts which consists of forming recesses in a block of carbon material, inserting portions of piece parts to be excluded from heat treatment into said recesses of surface of a heat treating bath of molten salt with said parts suspended downwardly, and quenching said piece parts after a predetermined period of exposure in said bath.

3. A method of locally heat treating portions of piece parts which consists in supporting a plurality of piece parts from a block of material having a specific gravity lower than that of a heat communicating fluid, floating-said block with said piece parts extending downward into .said fluid, removing said block and its supported piece parts from said'fiuid after a predetermined period of exposure. and quenching said. piece parts in a coolant to impart hardness thereto. 4. A method of processing piece parts in a cyaniding or carburizing bath which consists in inserting the piece parts into openings in a block -of coke carbon, floating said block of carbon with the piece parts suspended downwardly in a bath of molten cyanide. exposing the suspended piece parts in said bath of cyanide for a predetermined period of time and quenching said piece parts upon withdrawal from said bath.

5. 'A method of handling a plurality or piece parts for local heat treatment which comprises the steps of recessing a block of coke carbon to provide a plurality of apertures corresponding in shape to the shape of those portions of said piece parts to be excluded from the heat treatment. inserting a plurality of said piece parts into said recesses of said block, floating said block upon the surface of a molten cyanide bath with said piece parts immersed therein, and quenchsaid block, floating saidblock upon the v v 3 ing said block and said piece parts after a predetermined period of exposure in said bath.

6. A method of floating a.plurality of piece parts in a heat treating bath which comprises the steps of partially embeddlng a plurality of piece parts in a block of carbon material having a specific gravity lower than the specific gravity of.said bath with portions of said parts exposed {for heating, floating said block with said exposed portions of said piece parts lowermost on the surface'of said bath, removing said block and said piece parts after a predetermined period of exposure in said bath. and quenching said piece parts to impart hardness to exposed portions of said pieceparts which were heated by immersion in said bath.

- 7. A method of locally heat treating manufactured piece parts which consists in molding a supporting block having recesses corresponding to the portions of the piece parts which are to be excluded from heat treatment, embedding said piece parts so that portions of them are contained within said recesses and other portions protrude therefrom, floating said piece parts and said block upon the surface of molten heat communicating material. removing said piece parts and quenching to impart temper to the protruding portions of said piece parts.

8. A method of treating piece parts which con-' sists in the steps of embedding a'piurality of piece parts partially. within a block of heat insul'ating material having exposed portions of said piece parts extending along one face thereof, floating said block with said exposed portions of said piece parts downward in a bath of molten heat communicating substance, and quenching said block and said piece parts upon removal from said bath. i

- ELMER G. GILBERTSON.

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