US2196902A - Method of heat treating metal bodies - Google Patents

Description

April 9, 1940. w JONES I r 2,196,902 u'ruonior HEAT TREATING METAL BODIES I 1 Filed Aug. 24, 195'1- 2 sheets-am 1 INVENTQR HOMER WQJQNES ATTORNEY p i 9,1940- 'H. w; JON-Es 2.196.902

IITHOD OF HEAT TREATING METAL BODI [BS Filed Aug. 24, 1937 2 Sheets -She et 2 V ,;/VH F sn F mm 5 HHHHII: E r

I 9/F/7/"// l Tss- A 56 HOMER WJONES ATTORNEY Patented Apr. -9, 1940 f UNITED STATE-s PA ENT OFFICE METHOD OF HEAT TREATING METAL BODIES Homer W. Jones, Westiield, N. 1., minor to The Linde Air Products Company, a corporation of Ohio.

ApplicationAugust 24,1931, Serial no. mam

3 Claims.

meeting edge and a portion of the interior of the I body immediately adjacentthe meeting edge.

The method of this invention will be described herein chiefly as'it may be applied to the hardening of the comers of steel bodies or machine tool parts-which are subjected to high stresses,

such as large dies of the type used in the manufacture of bodies and tops of automobiles. The

' size of the sheets of metal which are utilized in.

forming the bodies and tops of automobiles necesg sitates the use of large steel'dies, the hardening of which by previous methods has been'diflicult and expensive.

The hardening of such dies has heretofore been accomplished by either ordinary heat-trutment g or case-hardening methods. 'In ordinary heattreating operations, the entire die is placedin afurnace and heated to a temperature above the critical, whereupon the die is quenched to :pro-;

This method produce a hardened structure. r so duces a hardened structure throughout the whole of the die, and it is necessary to temper the hardness by a further heat-treatment so that-the interior of the die will have sufllcient ductility to withstand the impact stresses produced by .shear- 3; ing or cutting metal. The entire die is'heated in each operation, and it is impossibleto attain 40 heat-treatment also distorts the die, necessitating the use of special expedients to assure the production of an accurately sized and shaped die.

In ordinary case hardening operations, the entire dieis heated in a carburizing box packed 45 with a carburizing agent which will add carbon to a portion of the outer surface, and, after carburizing, the die is cooled to produce a hardened outer surface or case. After carburizing, it is necessary to reheat the die .to relieve stresses 50 produced by theprevious operations The entire die is heated in each operation, producing distortion, and the hardened caseproduced is usually so shallowthat, in heavy service, it tendsvto 1 break, crack, chip and spallif so In most instances, the greatest amount of wear ('Gl. Ill-21) on a die occurs at andnear its corners. Accordingly, for a maximum life, such dies should have tough bodies, a moderate hardness over the portions of the surface remote from the corners,

and the greatest hardness at and adjacent to the 5 corners.

The principal objects of this invention are to ,provide amethod of hardening the comer of a steel die or other hardenable metal body which will produce amaximum hardness atthe shearing edge without seriously impairing the ductility and toughness of the interior or body of the die; to provide such a method which will be facile, simple and economical; and to provide a method of flame hardening the corners of metal bodies 15 which may be made automatic or semi-automatic.- According to this invention, successive portions of a die corner to be hardened are heated uniformly to a temperature within or above the hardening or ,critical range, and the portions so heated are cooled to harden the same and alsoto restrict the depth of hardening. The uniform heating of successive portions of the corner is effected by high temperature heating flames applied to each of the intersecting surfaces at places 25 adjacent'to' but spaced from the meeting edge of "said surfaces, the edge and the portion of the corner closely adjacent thereto being heated chiefly by conduction from the, directly heated portions. Preferably, relatively wide heating flames having an equalized velocity front'are used and are disposed transversely or substantially perpendicularly to the edge.

The inventionwill more readily be understood 7 from the following description and the accom- 36 panying drawings, in which: simultaneously a maximum hardness in the wear ing portions of the die and a maximum ductility" and toughness in the interior of the die. Such Fig. 1 is a perspective view of apparatus adapted for use in hardening acorner of a metal body;

Fig. 2 is a vertical sectional view of a comer 40 of a metal body or steel die, illustratingthe application thereto of relatively wide, elongated heating flames; 1 Fig. 3 is a longitudinal sectional view illustrating the application of a heating flame and cooling fluid to a surface of a metal body; Fig. a bottom view of a "heat-treatin head'forming part'of the apparatus-of Fig. -1;

Fig. 5 is a longitudinal sectional view of the head of Fig. 4, taken along the lined-4; and v Fig. 6 is a. transverse longitudinal sectional view of the head of Fig. 4, taken along the ing part of blow-pipes B and B' are supplied with a combustible gas mixture and a cooling or quenching fluid by suitable fluid-control mechanisms and are positioned at a comer A of a metal body or steel die M. The heat-treating heads H and H and blowpipes B and B are supported in working position from a suitable carriage C by structure which includes means for independent adjustment of each head H and H vertically and horizontally in a plane perpendicular to the corner to be treated, so-that portions of each surface on opposite sides of the edge of the corner will be treated simultaneously. The supporting structure also includes means for moving the heads H and H simultaneously, and longitudinally of the corner to be treated, to permit progressive treatment of successive longitudinal portions of the corner manually, automatically, or semi-automatically. The carriage C travels along a suitable track T supported at a convenient height above the metal body M.

The heat-treating heads H and H may be of any type adapted to project a heating flame F upon a portion of the corner of the metal body M adjacent to, but not at, the edge of the corner, and thereafter to project a stream of quenching fluid W upon the heatedportion, as

indicated in Fig. 3. It is preferred, however, to use a head of the type shown in Figs. 4-6, which projects a ribbonlike flame having an equalized velocity front, in a manner subsequently described. A flame of the latter type heats the treated portions uniformly and, as shown in Fig. 2, produces a hardened corner portion A of the desired depth andhardness, at the same time leaving the' unhardened interior of the metal body or die sufllciently tough and ductile to withstand severe impact stresses. The construction of. this preferred type of head is described and claimed in my co-pending application Serial No. 160,575 filed concurrently herewith.

' reasons which will be explained below. A control mechanism which, by reason of its simplicity, availability, and effectiveness, is a suitably modified oxy-acetylene blowpipe body of the type that permits control of flame temperatures by mixing fuel gas, oxygen, and air in various proportions. Each blowpipe should be provided with valves I I! or l0 and II or II for controlling the flow of fuel gas (preferably acetylene), and oxidizing gas, respectively, to a conventional mixer andsubsequently through a conduit H or ll to the head H or H. Conventional means (not shown) are preferably provided for supplying either pure oxygen or oxygen-nitrogen mixtures of controllably variable composition and pressure to the inlets of the valves II and II. If desired, air may be admitted to the oxygen stream below the valves II .and II. Other conventional means (not shown) are provided to supply fuel gas at a controllably variable pressure. to the inlets of the valves l0 and I 0'. Valves l2 and I 2' may be provided to control the flow of quenching fluid, usually water, through conduits l3 and I3 to the heads H and H.

The carriage C, which supports the blowpipes B and B and heat-treating heads H and H comprises a frame or case 20 provided with wheels or runners, or'both, to permit travel along the track T. The carriage may be propelled either by hand or by a motor, as desired. Upon the case 20 there is mounted a slide 2| which is rotatable about an axis perpendicular to the top of the case 20. Bya rack and pinion device operated by a handwheel 22, the slide 2| may be moved back and forth horizontally across the top of the case 20'. On one end of the slide 2| there is a post 30 provided with an elevating screw 3| operated by a handwheel 32, and a vertical slide, in threadedengagement with the elevating screw-3| and guided by the post 30, is

provided with an arm 33. The arm 33 may. be

raised a'l'zd lowered vertically withrespect to the to of the case 20 through operation of the handwheel 32 and elevating screw 3|. Pivotally secured at right angles to the end of the arm 33 is a second arm 34, and pivotally secured at right angles to the second arm 34 is a supporting member 35. The blowpipe B is directly and rigidly secured to the member 35, and the blowpipe B is supported by the member 35 through suitable adjustable sliding supports 36 and 3! disposed at right angles to each other. By adjusting the angular positions of the slide 2|, arm 34, and member 35, the blowpipe B and B' and the heattreating' heads H and H may be set at any desired angle to the work. By operating the handwheels 22 and 32, horizontal. and vertical adjustment of the blowpipes B and B and the heads H and H may be effected, and horizontal and vertical adjustment of the head H independent of the head H may be obtained by tuming handwheels 36' and 31' to adjust the slidin supports 36 and 31, respectively.

In use, the heat-treating heads are positioned,

one on each side of a corner, with theflames applied to a portion of each of the surfaces of the corner, the portions directly heated in this manner being spaced from the edge E of the comer, as

shown in Figs. 1 and 2. A jet or jets W of water or other quenching fluid is projected simultaneously with each heating flame and rearwardly thereof, away from the direction of travel of the heattreating heads H and H, as indicated in Fig. 3, so that the entire length of the comer may be hardened in a single pass. The edge E of the corner is heated and cooled chiefly by conduction from and to the directly heated and cooled parts of the comer, and thereby attains substantially the same hardness as the directly heated and cooled parts.

While it will usually be necessary to harden onlya single corner of a metal body or 'die, in some instances it may be desirable to harden a plurality of corners, two adjacent comers, or two adjacent corners and the surface common to the corners, such as in the case of punches used in producing elongated slots in sheets of metal. In such instances, a corner A" of the metal body M of Fig. 2 may be hardened simultaneously with the corner A by two blowpipes and heads (not shown) similar to the blowpipes B and B and heads H and H' of Figs. 1 and 2. These additional heads maybe supported from and moved by the carriage C by suitable supporting means similar to the supporting means for blowpipes B and B, and the heads disposed in substantially the same relation with respect to the corner A" as the heads I! and H .are disposed with respect to the comer A. In other instances, it may also be desirable to harden the entire surface common Y a head H" (shown partially in full and partially in dotted linesin Fig.2), head H, and a head H' (shown in dotted lines in Fig. 2) may direct heating flames F", F, and F', respectively, onto the surface common tothe corners A and A" and the surfaces of the corners intersecting-the common surface. head H' and directs the elongated flame F" over the greater portion of the surface common to the corners, the flame F" preferably being applied to this surface in such a manner as to heat chiefly or primarily by conduction the edges E and E of the corners A and A",.respectively. The flame F' is applied to the corner A'f from the head H' in a manner similar to that in which the flame F is applied to the corner A. The heads H, H", and H'" may be supported from the'carriage C by suitable means similar to the support- .ing means for heads H and H, and as the heads H, H", and H'" are moved simultaneously by the carriage C, they are also adapted to direct cooling jets upon the heated corners and common surface immediately following the heating flames in the manner previously described.

In most instances, the mass of metal to be treated will be sumciently small that a very high i flame temperature and a brief heating period will produce the desired hardening, and in such instances it will be most advantageous to use a heating flame of acetylene and pure oxygen. In some instances, however, the section to be treated will be so heavy 'that the mass effect, encountered in heat-treating heavy sections of metal,

, will. make it more desirable to use a lower flame temperature and a longer heating perlodto permit the heat to soak into the metal without danger of overheating-and in such an instance it is preferred to lower the flame temperature by diluting the oxygen with nitrogen, as by mixing air with uniform pressure over the length-of an elongated orifice in the heat-treating heads H and H; Such a flame may be produced by the preferred type of head illustrated in Figs. 4-6, towhich reference is now made.

The head H of the blowpipe B, as in Figs. 4--s,

, comprises a front block 40, a rear block 4|,and a 'U-shaped gasket. 42 clamped therebetween.

The rear block 4| is provided with an inletpassage 43 to which the conduit I4 is connected. The passage 43, which'extends centrally through the'rear block 4| in a direction perpendicular to the inner surface thereof terminates in a chamber 45; the chamber 45 preferably having a concave back surface conforming in shape to a right segment of a -cylinder. The inlet passage 43 preferably terminates at a point adjacent the greatest distance between the concave surface and that opposite thereto, and substantially in the, center of the concave surface. Leading from the chamber is a relatively thin and wide passage 41 terminating in an elongated orifice 48, the passage 41 being formed between the blocks 40 and 4| by the opening in the gasket 42, which The head H" is wider than the preferably extends to a point 49 somewhat be-, yond the entrance of the inlet passage into the chamber. The width of the passage 41 andorifice 48 may be varied at will by using U-shaped gaskets having openings of various widths. The combustible mixture is led into the chamber 45 by the inlet passage 43 and isprojected therefrom, in a direction angular to that of its, inlet, through the relatively thin passage '41 and e the elongated orifice 48, thereby forming a rela tively wide, elongated jet extending across the .width of the orifice 48 and producing aflam'e' having an inner cone of substantially uniform sage 43 and the passage 4! is approximately 90.

The rear block 4| is provided with a cooling fluid inlet 50 to which the conduit I3 is connected. Two passages 5| and 52, one on each side of the combustible mixture inlet passage 43, lead from the cooling inlet 50 to a chamber 54 disposed within the rear block 4|. adjacent the orifice or front end thereof. The chamber 54 may be a hole drilled from the side of the block, the outer end thereof being closed by suitable means, such as a plug 55.

. .To direct the cooling-fluid upon a surface portion previously heated, a' plurality of fluid discharge passages 56 terminate in a row of discharge orifices 5'! spaced from and preferably parallel to the combustible mixture orifice 48. For more uniform quenching, the discharge passages are preferably sufiiciently closetogether so that the cooling jets projected therefrom will merge laterally to form a continuous wide cooling stream of substantially the same width as the relatively wide, heating jet. The fluid dis- .chargepassages 56 are preferably inclined away from the combustible mixture discharge passage,

suitably at an angle of approximately 5, to prevent the cooling fluid, after being directed upon the surface, from interfering with the heating flame. The cooling. fluid, when utilized in the above manner, not only prevents the blowpipe head from becoming overheated, but also cools previously heated portions of the metal body M.

The blocks and 4| are provided with a plurality of holes 58 in which bolts 59 are inserted to clamp the gasket tightly between the blocks.

It will be understood that other blowpipes than those described may be used in carrying out the method of this invention; that the blowpipes may be held stationary, and the metal body or die moved relatively thereto; and that other changes may be made which will not depart from the spirit and scope of this invention.

What is claimed is:

1. A method of heat treating a comer of a ferrous metal body which comprises directing a wide high temperature heating flame against a portion of one of the surfaces forming said corner; directing a second wide high temperature heating flame against a portionof the other surface forming said corner, such second-named portion being disposed directly opposite the first-named portion on the other side of the edge of said comer, and said wide high temperature heating flames being of substantially the same width, dis- .posed in the same plane perpendicular to said edge, and.so directed that the portions of said surfaces directly heated are spaced from the'edge of said corner substantially equal distances and at such distances that said edge will be heated chiefly by conduction of substantially the same amounts ofheat from each of the portions di- .such portions being disposed on opposite sides of the edge of said corner and also being spaced from the edge of said comer, so as to heat said spaced portions directly and to heat said edge and parts of said corner closely adjacent thereto chiefly by conduction from the portions directly heated; cooling the heated surface portions of said corner immediately after heating; and similarly heating and cooling successive surface portions of said corner to harden the same.

3. A method of heat treating adjoining portions of two angularly disposed and merging surfaces of a ferrous metal body which comprises applying localized high temperature heat to said surfaces at points directly opposite each other on each side of and spaced from the merging portion of said surfaces so as to heat simultaneously a portion of each of said surfaces directly and to heat the merging portion of said surfaces chiefly by conduction from the portions heated directly; cooling the heated surface portions simultaneously and immediately after such heating; and similarly heating and cooling successive portions of said surfaces to harden the same.

HOMER W. JONES. v

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