US1317055A - Pressed-steel machine parts and method op making the same - Google Patents

Description

A. L'TOWNSEND AND H. M. NAUGLE. PnEssED STEEL MAcmNEjPARJs AND METHOD of MAKING 1HE SAME.

- APPucATsoM mso Mmm. ma.. 1,317,055. Patentedsept. 23,1919.

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PRESSED STEEL MACHINE PARTS AND METHOD 0F MAKING THE SAME.

APPLICATION rufo MAR. 24.1919.

1,3 1 7,055. Y Patent-ed Sept. 23, 1919.

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. PRESSE() MACHINE PARTS AND OF `MA THE SAME.

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l'atented Sept. 919,

4 S HE A. I. TOWNSEND AND H. M. NAUGLE. A

MACHINE PARTS AND METHOD 0F MAKING THE SAME.

PucATsoN HLED 4l/m24. |919.

'Patented SGpt. 23, 1919.

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I x I l y H w w M I 1 I i I I I v PREssED STEEL '193172055 mined dimensions.

y UNITED sTATEs PATENT oEEI'oE.

ARTHUR J. TOWNSEND AND HARRY M. NAUGLE, 0F CANTON, OHIO.

PRESSED-STEEL MACHINE )PARTS AN D METHOD or MAKING THE SAME.

vthe following is a specification, and vwhich are illustrated 1n the accompanying drawings, forming a part thereof.V

The invention relates to machine parts, meaning thereby the movable parts of maf,

Mchinery, vwhich must have hardness to resist wear in addition to the strength and tough-v ness requir'ed to withstand. shocksiind to transmit force or support weight and thel invention is more especially concerned with vthose machine parts which are desirably made in the lightest possible form consistent with strength, such for example, as the hollow piston pins of internal combustion engines, brake drums for automobiles, wheel hubs and the like. In the commercial manufacture of these parts it has been customary to employ one or the other of two methods of production `both of which comprise the formation of the parts to substantially n ished dimensions from mild steel or steel alloys and the subsequent case hardening of those surfaces of the parts which are exposed to wear in use.A One of the methods of production se employed involves cutting the parts from solid or only partially formed blocks or bars, while in the other of these methods the parts are cold pressed or d rawn to shape from plates or disks of predeter- Inl the one case, a substantial part of the weight of the metal, frequently more than is retained in the; linished articleis removed and lost and s netimes, as in making a hollow piston pin, or example, the partremoved comprises t e dense interior portion of the metal while the part retained that most likely to `be defective because of surface cracks or the like and great ditliculty is experienced in cutting.;V the interior wall exactly concentric withthe extenior surface to obtain the highly`desirable symmetrical distribution of weight inthe finished article. The shaping of the articlesby the cold pressing or drawing method,

on the other hand, usually requires a consid` erable number of partial operations or steps and careful annealing ot the metal `for each of these steps.

Specification of Letters Patent. l Patented Sept. 23, 1919.

pplicatiOIl filed March 24, 1919. Serial Nm 284,540. i

It will thus be understood that both of the said methods of forming the articles are expensive and that they are commercially practicable only when steel or steel alloys containing very little carbon are used. Furthermore, as these low carbon steels and steel alloys are not susceptible of being appreciably hardened by heat treatment, the subsequent case hardening of the parts, heretofore mentioned, is always required. This case hardening of the parts frequently fails to obtain luniform hardness throughout the wearing surfaces and the parts are weakened rather than ,strengthened by this treatment.

The object of the present invention is the provision of machine parts of the kind described of reduced weight but of equal or greater strength and du 'ability and of more uniform and improved hardness, and a method of producing the same: To this end the invention contemplates the selection of plates or the like of steel or steel alloy containinor sullicient carbon to respond to hardening y4 heat treatment in a marked degree, heating the said Plates to a temperature at which they are readily ductile, pressing tlie same while hot between dies to the shape and substantially finished dimensions of the articles desired, but preferably maintaining a like thickness with the original plates, snioothing the wearing surfaces of the articles and then hardening the articles throughout by appropriate heat treatment l in acf/ cordance with theanalysis of the selected steel or steel alloy. I'n the use of steel alloys V which are t'oo hard to be machined when cooled "in the. air from a working temperature, the smoothing of the wearlng surfaces of the articles is permitted without reheat-jl ing the articles for annealing, if the original cooling is substantially retarded, as byliacking the articles in lime immediately upon their removal from the forming dies. In the accompanying drawings g- Figure l is a central sectional view 0f va brake drum formed of medium or high 'carso. is. 1i and i5,

' ,go Fig. 17 but show the dies Fig. 4 is a blank of medium` or high carbon steel or steel alloy of the propei` size and shape to be formed into a hollow piston piu in accordance with the present inventlon,

E Figs. 5 and 6 show the product after successive operations of the present -method to 'form the said piston pin from thev blank illustrated in Fig. 4, and for comparison- Fig 7 is similar to Fig. et but shows a 10 blank of mild or low carbon steel of proper size and shape to be formed into a hollow piston pin by the cold pressingrnethod heretofor used, and

-Figs 8,9, 10, 11 and 12 show the product 15 after successive operations by the said cold pressing process to form the piston pin from ythcblank shown in Fig. 7,

Fig. 13 is a View, partly in section and partly in 'side elevation, showing dies for performing the irst operation of producing a hub =b the presentinethod, a blank of steel ot the e aracter above mentioned in the brief description of Figs. 1 and 1 being in the die, Fig. 14 is similar to Fig. 13 but shows the dies in closed position upon the Work,

' n Fig. 15 is similarto Fig. 1i but shows the dies einfployed in a further step in the operation o ont metliodand for comparison witliFigs.

if ,Fig. 16 is a View, partly in section and partly in side elevation, showing dies tor performing the first operation of producing a hub by the cold pressing method hereto- 35 fore used, a blank of mild steel being shown kin the die,

Fig. 17 is similar to Fig. 16 and shows the n u s i same dies in closed position upon, the work,l

Figs. 18, 19 and 20 are each similar to used to perform the several additional operations necessary to produce the finished shape of the hub, by the cold pressing process,

j Fig. 21 is a detail sectional View greatly enlarged-and conrentially representing the uniform texture of a-niedium onliigh carbon steel or steel alloy after the same has been hardened by heat treatment, and for conn parison* i *i Fig. 22 is similar to 21 butshows, in

il like conventional manner, the texture of a mild or low carbon Asteel after the same has lf been carbonized or case hardened.

` .l i ln carrying out theinvention the selected blank, as

11 (Fig. Lle) .or 28 (Fig. 13) Vwill 'usually be a relatively thin circular diskoi .steel which may have a medium carbon content of approximately .45%.

mately one per cent. oi? chromium this steel has physical properties substantially as followli Y,Elastic limit pounds per square inch 55000 15 Elongation in two incbes.y 25% shape, as

producing the said hub by the pres- `In the an-y nealed state and when alloyed with approxi-v For the production of a hollow piston pin. as 13, (Fig. 6) the blank 11 is heated to a working temperature which is preferably maintained between 1500o and 1700O F.`to

secure the desired ductility Without eXcessive scaling. W'hile so heated, the blank is pressed between appropriate dies to the re quired 'size and shape, a single intermediate 1Q (Fig. 5) being usually suiicient and the entirepressing operation being ordinarily performed without reheating. In event an alloy steel has been used for-` the blank 11 and it is desired to smooth the Wearing surface ofthe article With a cutting j tool, cooling `from the working tems0` perature is preferably retarded bypacking the article in linie, thus annealin the same; and by quickly performingthe rec ueed nuno-v ber of pressing opera-tions, such subsequent annealing as well as the pressing of the arti-7 85 cle, may tbe accomplished by a single heating oi the same. In the case of the piston pin 13 the closedeud may then be removed by cutting tlirough'the article at the place indicated by the dotted line 14 (Fig. 6) WithoutuQO tui-ther annealing. liso-called straight car hon steel has been used for the blank, as 11, the article maybe allowed to cool in the air after being pressed to shape.

Whether formed from straight carbon or alloy steel, the article, as 13, after being trimmed as indicated, and after having had its wearing surface smoothed, when required, is 'hardened by heat treatment andpolished. The finished article `will thus be hard and tough throughout vas conventionally represented at 35 (Fig. 21). As an example illustrating `the inventionit has been 'found that when an alloy steel containing approximately .45T/f carbon and one per cent. chromium is used, the physical properties of the finished article are substantially as lfollows:

Elastic limit pounds per` square 11 inch i 200,000 Reduction of area 10% Elongation of 1two inches 8%.

1While the heat treatment for hardening the article, as 13, and the resulting physical i properties may vary, somewhat with the analysis of the selected steel, thesaidheat treatment will generally comprise quenching in oil from a temperature ab0ve,that of decalescence and reheating to a lower tem-" erature for the purposeof removing cooling strains and modifying the intense hard y ness produced by quenching.

By the method 'ust described` the nuin-l ber o operations necessary in stamping or pressing any article is reduced, at least on'c-v4 A. half, in comparison with the cold pressingi' i method heretofore used. Figs. 7 to 12 inclusive show Ithe operations necessary with" .the pressing process toforin a piston in from mild or low carbon Steel. The*` blank from which the pin is stamped is shown at 5, and represents a blank of mild steel of proper size and shape to form the pin. By successive stamping operations upon suitable dies this blank assumes the forms shown at 6, 7 8 and 9 and after each pressing operation the product is annealed teior or backing.

`said blank 5 before the next pressing operation. After the product has passed through all of the 'necessary stamping operations and assumes the form shown lat 9 (F ig. 12) the closed end of the product isl cut off as indicated by the dotted line l0 and the pin is carbon ized or case hardened, giving it a thin hardened shell upon its surface while the interior of the steel remains soft.

Inu'Fig. 22 the thin hardened shell of a case hardened article, as the pin 9 (Fig. 12) is ,conventionally indicated at 36 while the shading 37 (Fig. 22) indicates the soft in- Itwill be understood tlfat thefpart 3i" is`no stronger than the original blank 5 (Fig. 7 while. to permit the said several cold pressing operations, the must have been formed from Steel containinfr not more than .15% carbon and having p iysieal properties, substantially as follows; Elastic limit pounds per square inch 2600() Reduction of area 55% Elongation 1n twoinches 301)( l Such a steel respondsonly slightly to heat treatment and' cannot be materially increased in strength, hardness or toughness beyond the properties indicated by the above figures. It follows, therefore` since the Vpin 9 (Fig. 12), when case hardened,

cannot be relied upon to possess added strength merely because of its said thin hardened shell 36, the walls of the said pin must he correspondingly thicker than the walls of the pin 13 (Fig. 6) and there will be a similar difference in the weight of the corresponding blanks, as '5 (Fig: T) and I1 (Fig. 4t). Valuable alloy steels may thus be used for the production of the machine parts provided by the present invention without undulyincreasing the cost. while the reduction of weight is of itself of enormous importance in some instances, as in the ease of a piston pin for internal combustion engines where. every effort is made to reduce the momentumy of the reciprocating parts.

,ln Fig. 1, the numeral t designates a brake drum formed of medium or high carboii steel and produced by the method to which this application pertains. On account of the properties of this steel as regards ductility, that is the reduction of area and elongation, it is impossible. to` do any conlamobile, unless some reason `as beforedescribed, it may be readily formed or drawn. Due to the superior physical properties of this steel, the finished product may be reduced in thickness and weight to only a fraction of what is required in the thickness and weight of low carbon steels, formed `or pressed cold, and at the same time the strength and efficiency of the product greatly increased, it being possible to form an article thereby in one or two operations while the same article would require four or five or more operations made by the cold pressing method.

Referring to Fig. 3, a forging of the rough size required for producing a brake drum is shown in section at 1. In producing drop forgings, it is impossible to make the forging any nearer than the rough size of the article to be produced and after the forging is finished a considerable amount ot difficult and expensive machine work is necessary to turn the forging down to the required size'and shape, this machine work involving a great deal of expensive labor and a wasting of at least one-half of the metal in the forging. For instance, the dotted lines at 2 show the cross sectional shape of the finished brake drumwhich is produced from this forging, all of the metal not inclosed by these lilies being wasted in the machine work. F urthermore, to permit of this large amount of machine work, the forging must be softened by annealing and the finished part should be case hardened to resist wear.

Referring to Fig. 2. the numeral 8 indicates a finished brake drum formed of mild or low carbon steel by the usual cold pressing process andfby comparison with Fig. 1, showsthe greater weight of a drum so formed. It is desirable to educe the weight of all parts of a machine. ebpecially an autoexists for desiring weight in some special part, and for this reason. a special grade of steel which combines lightness and strength is best adapted for machine parts.

)Veal-ing parts, such as brake drums, shackle bolts, piston pins and the like havel occasionally been made by the cold pressing process to reduce the. cost of manufacture. ln order that such parts could be so made, it was necessary to use a lnild `or soft steel having a low carbon content and a correspondingly high reduetitm of area and elongat ion. this resulting in a product which was weak structurally.

Figs. lil. l-l and l5 illustrate two pairs of dies. as 2l). Ill). (Figs. 13 and 14), and'32, 33, (Fig. 15) which ma)- be used for forlning a wheel hub from :t medium or high carbon steel ,or steel alloy blank bythe present method, the said pairsof diesbeiig used in succession to form the blalik to the finished dimensions of**the wheel hub. As shown, the

still hot is then placed in the die 32, the-die 33 coperating therewith to form the "finished hub 34.. The finished product of the dies is now strengthened, hardened and toughened throughout its entire structure by heat treatment, as described in connection with the manufacture of the piston pin 13 (Fig. 6) This nished product will beconsiderubly less in Weight than a hub of like size formed bythe cold pressing method and at the saine time will be several times as strong as the other product..

Figs. 16 to 20 inclusive show the severalv pairs of dies required' for forming a wheel hub from a mild or low `carbon steel blank by the cold stampin heretofore used; the ies of each pair operating in conjunction and the several pairs of dies being adapted to be used in succession to transform the blank into the finished wheel hub. The blank 16 of mild or low carbon steel, after being first annealed, is placed in the lower die 16, the upper die 17 cooperating therewith to form the intermediate product as shown at 18, (Fig. 17).k

rlhis interniediate product 18 is now an nealed and then placed in the die 19 Which, in conjunction with the upper die 20, forms the second intermediate product as shown at 21 (Fig. 18). The intermediateproduct 21 is now again annealed and the several operations are repeated with respect to dies 22,

23, forming `the third intermediate product" 24 (Fig. 19) and dies 25 26, forming the finished hub 27 (Fig. 20) which is afterward carbonized or oase hardened to give it a hardened thin shell upon its surface.

It should be noted that the finished productprovi'ded by thepresent invention may have nearly Asin times the strength of products formed from the low carbon yor mild steel-by the-cold pressing process. For this reason, articles formed by the present method, need only weigh a fraction of the weight required in lcorresponding articles which are cold pressed from mild steel. A comparison of Figs. 1 and 2 serves to illustrate the reduction in weight made possible by the use of lighter stock for the production of articles in accordance with the present invention. The iinished product thus combines strength, resistance to Wear and lightness.

By a comparison `of Figs. 1 and-3 the ad vantages obtained by the -invention over the forging `process will be readily seen as this process not only saves considerable material 'but also a great amount of expensive labor.

Forging of such parts as the brake drums shown by dotted lines in Fig` 3 has been or. pressing method minces found impractical, owing tothe enormous waste of material and the expensive machine wort required to finish the product and the usual method of producing articles of this character has been by the cold pressing 7%0 method although, 'to afford the required strength, the finished product must-be considerably heavier than is desirable, as is illustrated by a comparison of Fig. `2 with Fig. 1. 75 t will also be understood that while the articles provided by the invention may be made from either so-called straight carbon or alloy steels theV carbon content must in either case be sufficientlyhigh to provide av 30 material which responds to heat treatmentin a marked degree. .lt is believedithat for this purpose the carbon content 'of both straight carbon and alloy steels used vinthe practice of the invention should be `about .30% or higher and the terms medium and high carbon steels found in certain of the appended claims are to be understood' as ren ferring preferably to such steels. While very desirable results may be secured in the 9e practice of the invention with a straight carbon steel of the analysisy indicated, most excellent results are also secured by the use of a chrome-vanadium alloy steel having a like carbon content. 95

l lt will be observed that in each case, the article produced, as the piston pin13, the brake drum 4:, or the wheel hub` 311, is tubular or cup-shaped and that the saine is formed with male and female die members, as 30 and 29 (Fig. 13) by pressure applied 1n a directionwliich is normal to the plane of the original. late and parallel "with the axis of the finis ed part. There is accordingly a drawing of the metal by which desirable structural characteristics peculiar to articles so formed are obtained in the iinished product.

' We claim as our invention:

1. A uniformly hardened cup-shaped or tubular machine wearing `part ot Inedium or high carbon steel hot pressed to substantially ,finished iorm and 'size from a fiat plate of the said steel and hardened' by heat4 treatment;

2. A uniformly hardenedicup-shaped or tubular machine wearing part of medium or high carbonl alloy steel het pressed to substantially finished form and size from a 'flat plate of the said steel and hardened by 120 heat treatment. i

3. A uniformly hardened cup-shaped or' tubular machine wearing part olf medium or high carbon chrome steel hot pressed to substantially finished form and size from a ich,

consists in heating a d Vt sheet or plate 1130" medium or high earbo'n steel or steelalloy to a temperature at which it is readily duetile, press forming the same while hot to substantially they finished form and size of the said cup-shaped or tubular machine part between lnale and female die members with pressure applied in a direction normal to the plane of the original plate and thereafter hardening the part throughout by heat treatment. v

The method of producing machine parts which consists in heating to a temperature of approximately i500" F. sheet or plate `steel alloy containing carbon in sutiicient amount to markedly respond to heat treatment, `pressing the same while so heated to substantially the liuished dimensions of the said machine part, packing the same in lime or similar substance while still hot and allowing it to cool while so packed, smoothing the wearing surface of the part and then uniformly hardening and toughening the part by heat treatment.

6. The method of producingr machine parts which consists in heating to a temperature of approximately 1500O F. sheet or plate chrome-vanadium steel alloy containingearbon in sufficient amount to markedly respond to heat treatment, pressing the saine while so heated to sul'istantially the finished dimensions ot' the said machine part. packing the same in lime or similar substance while still hot and allowing it to cool while so packed,smoothing the wearing surface ot' the part and then uniformly hardening and toughening the part by heat treatment. i

7. A Cup-shaped or tubularmachine part of medium or high carbon steel hot pressed to substantially finished Jform and size from a lat platel of the said steel and hardened throughout by heat treatment without carhonization.

P. A cup-shaped or tubular machine part of medium orhigh carbon alloy steel hot pressed to substantially finished form and size from a flat plate of the said steel and hardened throughout by vheat treatment without carbonization.

9. A cup-shape fl or tubular machine part of medium or high carbon chrome steel hot pressed to substantially finished4 form and size-from a flat plate of the said steel and hardened throughout by heat treatment without carbonizaton.

ARTHUR J. TOWNSEND. l HARRY M. NA T LE.

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