US2775520A - Cold-stamped articles - Google Patents

Description

Dec. 25, 1956 F. K. BLOOM ET AL COLD-STAMPED ARTICLES Filed Nov. 5, 1951 Z Z mzfl m aw w 0 m mm m m Z 0 WWUWMLM E BM NNM R wm wm N P AMMOM MMCNC/ lltiilrl.. 11 l INVENTORS Fredric/r K. B/aom William C. Clarke, Jr.

THE] R ATTORNEY 2,175,520 COLD-STAMPED ARTICLES Fredrick K. Bloom and William C. Clarke, Jr., Baltimore,

Md., assignorsto Armco Steel Corporation, a corporation of Ohio Application November 5, 1951, Serial No. 254,923

2 Claims. ((175-125 articles such as table flatwear, displaying coined or stamped surface configuration, and this of desired intricate detail. l

. Among the objects of our invention is the production of. coined or embossed metal products, of which table flattion in surface design from austenitic chromium nickel stainless steel sheet metal stock in direct and positive manner by cold-Working technique without necessity of inter United States Patent mediate anneal and in the absence of appreciable workhardening, which products conform closely to required sharpness and refinement of surface and finish detail and ornamentation with close, predictable and reproducible adherence to pattern and dimensions, with minimum wear and long useful life of the stamping and coining dies and with minimum investment in plant and labor, the products thus produced having pleasing lustrous surface appearance and detail together with high resistance to 'corropect of our invention, it may be noted that theauste'nitic:

chromium-nickel stainless steels possess 'many'desirable' 2,775,520 Patented Dec. 25, 1956 hardening properties, yet they do not by any means fully satisfy the many problems encountered in actual practice, Quite on the contrary, the rate of work-hardening had incold-stamping, cold-coining and cold-embossing these increased nickel steels still remains so high, even though materially improved over existing steels, as to remain a definite" limitation of the production of cold-stamped, cold coined and cold-embossed austenitic stainless steel products. 1 i I One of the important factors in the connection noted is the severe wear of the cold-formingdies. Another is the extent to which the coining, stamping and embossing operations may be conducted with reasonable power requirements and size of forming dies. In short, it may be-said that. the rapid work-hardening of the austenitic alloys has severelylimited, except for but comparatively simple patterns, the use of these stainless steels in the production of wear is illustrative, of any desired intricacy or ornamentaa embossed flatwear such as forks and spoons.

Cur invention is directed to alleviating the aforementioned difiiculties and to produce stamped, embossed or coined austenitic chromium-nickel stainless steel articles in much more effective manner than has hitherto been possible. 1 1

Accordingly, an important object of our invention is to minimize the aforementioned difliculties heretofore confronting the art in simple, practical and successful manner, and at the same time to provide botha variety of austeniticchromium-nickel stainless steel articles, and a method of producing the same, of which articles flat wear is illustrative, cold-stamped, cold-coined, or coldembossed in direct manner from annealed metal stock, in

the substantial absence-of intermediate anneal, to a high degree of surface or edge detail or both, and this without appreciable wear of the simple forming equipment required and while maintaining pleasing and lustrous surface finish characteristic of the metal, with high resistance to corrosion, and with non-magnetic characteristics including illustratively,nice surfacea'p pearance, ready susceptibility to high polish with lustrous finish, high resistance to corrosion, its non-magnetic qualities and the like. Unfortunately, however, these stainless steels tendto work-harden under cold-stamping, cold-coining or cold-embossing operations at a much steeper rate than do the straight chromium steels. Perhaps this is due to phase-transformation brought about byjcold-working,whereby part of the metal is converted: froman austenitic to a martensitic phase, thereby be};

coming more stable and harder. Be that as it may, and 1 regardless of the explanation, the austenitic; chromium} nickel stainless steels are found to work-h'arden at;dis-' tressingly high rates, a circumstance which drastically limitsthe number and variety of cold-stamped,-'coldcoined, or cold-embossed articles which may be produced from these steels. V It hasheretofore been observed that in'th'e most common grades of theaustenitic chromium-nickel stainless steels, 'say the 188 chromium-nickel'grade', the detrimental work-hardening phenomenon is diminished to a certain extent-upon substantial increase of the nickel content. A somewhat similar result is had by'increasing the manganese content, or by replacing part of the nickel ,with, manganese. Thus, incertain instances .of coldstrengths at high temperatures.

working, current practice has been to increasethe nickel a,

stainless steels, display .substantially reduced workqualities, together with low cost and investment in both 1 plant, equipment andlaboiz Briefly, We have found that by the addition 'of a small amount of copper to the known ,austenitic'chromium-j nickel stainlesssteels of say the 18-8 chromium-nickel grade, startling results, are achieved .in lowering the rate ofw ork -hardening. The addition of copper is observed to be muchmore effective than an increase in either the nickel or manganese content of the alloy, or both. The surprising character of theresult had is brought into bold reliefwhen it is considered that while copper has heretofore been added to steels for a variety of purposes, it ,l 1as never heretofore been added to selected steels, and in such amount, as to achieve the results presently obtained. I I i Thus, illustratively,.copper has heretofore been added to steels to increase the corrosion resistance displayed to. reducing acids. It has been used to promote physical It has been added to increasethe precipitation-hardening properties; As suggested hereinbefore, .however, copper has never heretofore been added to the austenitic chromium-nickelstainless steels in proper amount to bring about appre-- ciable and important decrease in the rate of work-hardem ing had in cold-stamping, cold-coining, cold-embossing andlike-operations,attended by important decrease in: ultimate tensile strength and with appreciable increasedi ductility. 1 1 k r In point ofcfactthe phenomenon presently observed is somewhat contrary to what would be theoretically antici-- pated because his known that when copperis added to} nickel, the metal is hardened and, in addition, tends to.

upon thc addition of copper in proper amount-toaustenitic chromium-nickel stainless steels, increased ductility is imparted, initial hardness is slightly reduced, and the rate of work-hardening also reduced. The tendency of the copperaddition to produce a detrimentalred-shortening effectis of but little moment. Complete fabrication .to finish dimensions and surface is possible through direct, cold-Working operations, without intermediate anneal.

' We havefound that abroad range of composition well suitedefor=theproduction of cold-stamped, cold-embossed or cold-coined products according to our invention is as .follows, carbon up to l manganese up to 15%, chromium to" 25%, nickel 7% -to-20%, coppe'r 1.0% to 6;0%', and remainder iron.

.The carbon is .kept within such practical limits as to prevent excessive embrittlernent. Moreover, the chromium and.nickellingredients;are present in sufiicientjqua'ntitles toyrangefrom the borderlinecase tothefdll austenitic'ralige. .The copper ispresent in sufiicient quantities to bring about the desired diminished work ha'r dening qualitie's, .while :the manganese is present in partial Substitutionfor :the nickel,an'd to impart tothe-- austcniiicsteel that certain, T comparatively slig'ht degree of;.ducti-l-ity-.characteristic'tof.that alloying additive.

Inasmuch as the stamping, embossing or coining-operations-,aresubstantially ones. involving thev exertion of 1 compressivestresses, certain cold-compression tests which we have undertaken serve'to illustrate the marked advantagesattendant upon the additionof copper. 'lTh'ese results are expressed in terms of the total work required to deform the various samples. The results thus achieved aresetforth in the following table:

It is evident upon considering the foregoing tablethat the addition of important'quantities of copper to either the 18- 6, 18"8,' or 18 -10 grades of austenitic c'hro' miu'm-nickel stainless steel are all accompanied by important decrease in' the cold-workhardening "factor, Additionally, and-having reference to 'the "l-8 l'O grade, an increa'se incopper content-from 3%-'to 5% is accor'npanie'd by a further decrease in-t'he work hardening 'fac- I V I A I While not so important in establishing 'the suitability or copper-containing 'auste'nitic c'hromium nickel stainlessY-st'eels in :the' production of embossed, stamped or coined stainless steel fiatwear, neverthelessa general indicatio'n 'of :the lowered rate of coldwork hardening"is. given by thedecrease in the'ultirnate' strength after colddrawing-whiclris had with the copper is indicate'd-in the following table:

Taib le II Ult. Tensile Stt. 1,000 Sn. f alter cold;drawing from HeatNc. 0 Or Ni Cu annealed'conditlon- 0% 20% 40% cor 1, 75%

-From-a consideration of-Table II it will be seen-that with fairly constant carboncontent, an increase of the nickel content within the austenitic range is accompanied by decreased ultimate-tensile strength, and increased ductility. Similarly, upon the addition of an important amount of copper, sa 3%, to the 'l4-14 chromiumnickel;.grade,,-.,further and .very marked decrease in..ul timate tensile strength, and consequent increaselin ductility, is had upon cold-drawing.

The single view of the drawing efiectively depicts the pleasing ornamentation which can be achieved, the intricate surface detail nrade possiblenbeing shown at 10, while the pleasingly milled edge is shown at 11. Practically any design which: may be. desired can be effectively produced in accordance with the practice of our in-- vention. Y i v we have found that perhaps that range of alloy composition best suited for most satisfactory results is. carbon {10% maximum, manganese .50 .to 2.00%,chromium 10% 101 20%, nickel 10% to. 15%, copper- 2.0% 'to 5.0%, and: remainder iron.

In this 'cornpositionwe maintain the silicon content withinthe normalrange. While phosphorus and sulfur arenormally maintained low, that is, not exceedingabou-t 0.04% phosphorus and 0.03% :sulfu-r (see, MetalsHandbook, 1948 edition, A. S. M. Cleveland, Ohio, page 5.63.), wepermit a range :up to say about 0.40% where some machining is required in addition to the embossing. stfips. Selenium :up to 0.40%, where desired, maybe addedsfor this purpose. And'where wedesire.;to stabilize thecarbon we sometimes include columbium or titanium in the'minirnum amounts, respectively, of 8 x percent-C and-4x percent C. The;addition of up to 4% molybdenum is found to improve corrosion resistance. None of these various additions seems to adversely affect the stamping, coining or V embossing properties.

-By-the-.praotice of our invention we produce, in-highly satisfactory manner, stamped, coined orembossed: prodnets, suchas ornamented stainless steel fiatwear, spoons and forks. .This objective is achieved in simple and positive manner, directly from stainless steel sheet or stripstock. Necessitytfor intermediate anneal. is effectively eliminated. At alltimes the cold hardeningrate isZ-retained within effectivelimits, and theforming equipment,,including shaping-and stampingdies,.display long useful life. vAt the same .time many advantages ,of stainless .steellare availed of 'fullyand effectively including iiolimag'neticpr'operties, pleasing and lustrous surface zippeiarance hghresistance to corrosion, and 'the'like. iAll'th'ese, as well as many other highly practical. advantages tend upon the practice of our invention.

Ifiis'apparentffrom the foregoing that once. the broad aspects of' our invention are disclosed, many'ernbodiririieiit's', thelv'eof will readily occur to those ski lled in the art; aiidiall falling within .the .ambit of .our disclosure. Aecord ngly, we intend. our present disclosure to be. con sidered solely illustrative, and f in nohse'nse 'limitative. we lclaimias our invention: v v

-jl Cold-stamped and machined stainless. steel -artic les analyzing approximately up to 0.15% carbon, up to 15 manganese, from about 10% to about 25% chrpmium, from about --7 to; about 20% nickel, from about {1.0% t01: about56'.0.% .copper, ione elementof the group ,consisting :of about F02,O4% to 0.40% phosphorus and about 0.03i,%'tO' O:40% "sulfur, and remainder iron.

2. Cold-stamped and machined stainlessvsteel articles analyzing approximately, up to 0.10% carbon, about 0.50% toabout 2.00% manganese, about-10% to about 20% chromium,about'10% to about 15% nickel, about 20'% to"-about 5.0% copper, one element 'of'thegroup c si 'ng'bt' about 0.04% to 0.40% phosphorus-and a i 03% rename-arm, and remainder iron.

- Y lkefercnceszon- -following' page) References Cited in the file of this patent UNITED STATES PATENTS Watrous Nov. 26, 1918 Whistler Dec. 29, 1936 Defranoux Sept. 19, 1950 FOREIGN PATENTS Great Britain Oct. 23, 1935 6 OTHER REFERENCES Die Design and Diernaking Practice, 3rd edition, pages 901-904. Edited by Jones. Pub. in 1951 by the Indus trial Press, New York, N. Y.

Claims (1)

1. COLD-STAMPED AND MACHINED STAINLESS STEEL ARTICLES ANALYZING APPROXIMATELY UP TO 0.15% CARBON, UP TO 15% MANGANESE, FROM ABOUT 10% TO ABOUT 25% CHROMIUM, FROM ABOUT 7% TO ABOUT 20% NICKEL, FROM ABOUT 1.0% TO ABOUT 6.0% COPPER, ONE ELEMENT OF THE GROUP CONSISTING OF ABOUT 0.04% TO 0.40% PHOSPHORUS AND ABOUT 0.03% TO 0.40% SULFUR, AND REMAINDER IRON.

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