US3149965A - Valve steel - Google Patents

Description

Sept. 22, 1964 P. A. JENNINGS VALVE STEEL.

- Y. Filed oct. :51, 195e 2.555. uEEEsom E zoem 96cm ED-EOKIO nEEEaom o nPEncoo oEEElom. s nEnEncoo o Q Time for; Melting in Seconds INVENTOR Pbu/ A. Jenn/hgs d i f m ORNEY United States Patent 3,149,965 VALVE STEEL Paul A. Jennings, Baltimore, Md., assigner to Armen Steel Corporation, a corporation of Ohio Filed Oct. 31, 1956, Ser. No. 619,548 9 Claims. (Ci. 7S--128) My invention relates to stainless steels, more particularly to internal combustion engine valve steels and Valve parts fashioned thereof.

Among the objects of my invention is the provision of an improved stainless steel, especially an internal combustion engine valve steel and forged valves and valve parts fashioned thereof, which steel is substantially fully austenitic, is precipitation-hardenable, is strong and hard at high temperatures of operation, Which readily may be forged or otherwise formed to desired specification, just as the valve steels of my prior U.S. Patents 2,602,738 and 2,698,785 of July 8, 1952, and January 4, 1955, respectively, for example, and which steel, valves and valve parts additionally possess good welding qualities as in the fabrication of internal combustion engine Valves with applied facings.

Other objects of my invention in part will be obvious and in part pointed out during the course of this specifcation.

Accordingly, my invention may be considered to reside in the combination of elements, mixture of materials, and composition of ingredients and in the valves, valve parts, and the like as described herein, the scope of the application of all of which forms the subject of the claims at the end of this specication.

In the accompanying drawing forming a part of this application for patent the single figure graphically illustrates the critical character of the composition as affecting the welding qualities of the steel and valves of my invention.

To promote a better understanding of the steel of my invention, it may be noted at this point that the austenitic chromium-manganese steels with or without nickel are becoming increasingly important. These steels typically analyze about 21% chromium, 10% manganese, 4% nickel, and the remainder iron for the grade designated Armco 2l-4Mn; and about 21% chromium, manganese, 4% nickel, .40% nitrogen and the remainder iron for the Armco grade 21-4N. Another is the grade analyzing about 21% chromium, 10% manganese, 3% nickel, .30% nitrogen and remainder iron for the Armco grade 2l-3N.

The austenitic chromium-manganese steels with or Without nickel have found particular favor in the internal combustion engine valve field, especially valves, valve seats, valve guides, and the like. Because of their corrosion-resisting characteristics, the steels are particularly suited to the construction of internal combustion engine exhaust valves for passenger vehicles, For here the valve seldom operates at a temperature exceeding l450 F. The stresses are comparatively low and there is little corrosion, oxidation and scaling at the temperatures encountered, particularly where the silicon content of the steel is maintained at a low value, as described and claimed in my prior US. patents referred to above.

The austenitic chromium-manganese steels with or without substantial nickel contents also find favor in the construction of heavy duty internal combustion engine exhaust valves where temperatures are encountered on the order of 1600D F. But in the heavy duty internal combustion engine exhaust valves there is employed a welded-on facing of Stellite or other high alloy metal. In general, Stellite may be considered to be an ironcobalt alloy containing chromium and/or tungsten, on the order of some 10% to 50%. Although expensive, it is most effective in resisting the wash and scour of exhaust gases at high temperature under the shock, vibration and impact encountered in actual use.

In applying the Stellite facing to a partially formed internal combustion engine valve it is common practice to resort to an automatic or at least semi-automatic welding technique. Illustratively, the roughly formed valves are seated with heads down and stems up in suitable refractory cups spaced about the periphery of a rotatable machine. And as the machine is rotated the valves, one after another, are brought into a position beneath a Welding torch which serves to bring the head of the valve to a proper welding temperature. The Stellite metal in form of an uncoated weld rod is melted and then applied to the valve head, the valve being uniformly rotated about its axis as the Stellite weld metal is applied to give a uniform applied facing.

Now in heating the austenitic chromium-manganese stainless steels with the Oxy-acetylene torch it was found that a thick, viscous and tenacious scum formed on the surface of the metal. This made welding most diflicult. Welding tests comparing the slag-forming characteristics of the austenitic chromium-manganese steels with the well known austenitic chromium-nickel steels conclusively show that the presence of large quantities of chromium and manganese together produces an unusually tough, impervious oxide coating on the heated surface, and that this coating or film is detrimental to Welding. Although there have been developed numerous fluxes for this film or coating in order to facilitate the Welding operation, these fluxes do not completely solve the problem.

Accordingly, one of the objects of my present invention is the provision of an austenitic chromium-manganese steel which possesses the age-hardening characteristics and hardness at room temperatures and at elevated temperatures of the steels of my prior patents referred to above, and, as distinguished from the prior steels noted below, is characterized by a free-flowing scum in melting, and in addition readily lends itself to welding when heated to welding temperatures by the Oxy-acetylene torch, with any scum formed during the heating operation readily breaking and reforming only with difficulty.

Referring now particularly to the practice of my invention, I find that the scum-forming tendency of the austenitic chromium-manganese stainless steels of my prior US. Patents 2,602,738 and 2,698,785 are intimately related to the silicon contents of the steels. And that in the melting of these steels there is considerable scum formation in the steels of the low silicon contents. In point of fact, there is little or no change in the character of the scum for steels of differing low silicon contents until there is reached a silicon value of at least about 0.5%. This point is in every sense critical because with less than about 0.5% there is a Very definite tough, dense, adherent and impervious scum on the steel heated to welding temperature; whereas, for austenitic chromiummanganese steels with about 0.5% silicon and more there is a sharp break in the scum. And it is noted that the scum reforms only with greatest diiiiculty.

In accordance with the practice of my invention I prepared a series of button `type samples of 21-4Mn stainless steel of differing silicon contents and melted them with the Oxy-acetylene torch; observed the time for melting, that is, until the buttons were completely melted to form pools, and also observed the characteristics of the scum, if any, formed during the melting. These samples of course were melted with no ux whatever. The composition of the samples and the results in terms of time of 3 melting and the scumming characteristics are given in Table I below:

TABLE I Melting Characteristics of 21-4Mn Stainless Steels of Difering Silicon Contents While all the samples of the 21-4Mn stainless steel set forth in Table I contained nickel in the amount of about 4%, it will be recognized that nickel does not oxidize, that it does not go into the slag and the presence or absence of nickel in the samples is wholly immaterial to the scumming properties of the steel. The same obtains with respect to the nitrogen content, some of the samples having a nitrogen content on the order of .30% and the others having this in residual amounts, on the order of .06%.

As a matter of interest, the data of Table I is presented in graphic form, this as the single figure of the accompanying drawing. The time for melting the various samples of 21-4Mn stainless steel and the scumming characteristics of the steel is given as a function of the silicon content of that steel. The graph forcefully reveals the critical nature of the scurnming characteristics of the steel at about 0.5% silicon. Below about 0.5% silicon content there is considerable scum; at the point of about 0.5 silicon there is a sharp break in the scum that forms and the scum reforms only with diculty. lt loses its dense, adherent and impervious quality and the tendency to reform does not appear with high silicon contents, that is, about 0.5% and above. And with the scumming had in the steel of .the lower silicon contents, it is noted that the time for melting is high. Moreover, the melting time sharply falls until there is reached a silicon content of about 0.5% and then virtually levels oif for the higher silicon contents, i.e., silicon contents from 0.5 up to about 3.0%. Actually, it will be seen that the time required for melting the steel decreases slightly for silicon contents between about 0.5% and 1.00%, and thereafter slightly increases with increasing silicon contents above 1.00%.

The free-scumming austenitic chromium-manganese stainless steel of my invention therefore essentially consists of about 0.40% to 1.50% carbon, 12% to 30% chromium, 5% to 20% manganese, up to 6% nickel, up to .6% nitrogen, with a silicon content of 0.5% to 1.5%, with remainder substantially all iron. Additionally it will be understood that the various ingredients are in such relative proportions as to ensure a substantially fully austenitic structure. The preferred steel of my invention includes nickel as an essential ingredient, the steel consisting essentially of about 0.40% to 1.00% carbon, 12% to 30% chromium, 5% to 12% manganese, 2% to 6% nickel, .1% to .6% nitrogen, .5% to 1.0% silicon, with the various ingredients in such proportions as to ensure a substantially austenitic structure and the remainder substantially all iron. And an even more specific embodiment of my invention possessing freescumming characteristics at welding temperatures consists essentially of about 0.40% to 0.65% carbon, 19% to 23% chromium, 8% to 10% manganese, .2% to .6% nitrogen, .5 to 1.0% silicon, with the various ingredients in such proportions as to assure a substantially austenitic 4 structure, and the remainder iron. Also a steel consisting essentially of about 0.40% to 0.60% carbon, 19% to 23% chrominum, 8% to 10% manganese, 2% to 6% nickel, .2% to .6% nitrogen, .5% to 1.0% silicon, with the ingredients in such proportions as to assure a substantially austenitic structure, and the remainder iron.

The steel of my invention not only is free-scumming and may be welded with ease, but it readily lends itself to forging and other hot-working and cold-working operations to yield the roughly formed article or product to be welded. Typically, the steel of my invention is readily forged or headed in the production of rough formed internal combustion engine exhaust valves which then may be heated with the Oxy-acetylene torch in automatic or semi-automatic machinery for the application of a Stellite or like welded facing.

rihus it will be seen that l provide in my invention an age-hardenable austenitic chromium-manganese stainless steel in which there is had the various objects hereinbefore set forth, together with many thoroughly practical advantages. The steel and the roughly formed internal combustion engine valves or other articles fashioned thereof possess the hardness at room temperatures and at high temperatures of the steel and valves of my prior US. patents identified above, and in addition, are freescumming at welding temperatures.

Since, in the light of the above disclosure, numerous embodiments of my invention will occur to those skilled in the art to which the invention relates, it will be understood that all matter described herein or shown in the accompanying drawing is to be interpreted as illustrative and not as a limitation.

l claim as my invention:

1. Austenitic stainless steel consisting essentially of about 0.45% to 1.50% carbon, about 12% to 30% chromium, about 5% to 20% manganese, about 3.25% to 6% .ickel, about .1% to .6% nitrogen, about .5% to 1.5% silicon, with the various ingredients in such proportions as to assure a substantially fully austenitic structure, and the remainder substantially all iron.

2. Austenitic stainless steel consisting essentially of about 0.40% to 1.50% carbon, about 19% to 23% chromium, about 8% to 10% manganese, about 3.25% to 6% nickel, about .2% to .6% nitrogen, about .5% to 1.5% sil-icon, with the various ingredients in such proportions as to assure a substantially fully austenic structure, and the remainder substantially all iron.

3. Forgeable austenitic stainless steel consisting essentially of about 0.40% to 0.7% carbon, about 12% to 30% chromium, about 5% to 12% manganese, about 2% .to 6% nickel, abou-t .2% to .6% nitrogen, about .5% to 1.0% silicon, with the various ingredients in such proportions as to assure a substantially austenitic structure, and the remainder substantially all iron.

4. Forgeable austenitic stainless steel consisting essentially of about 0.40% to 0.60% carbon, about 19% to 23% chromium, about 8% to 10% manganese, about 2% to 6% nickel, about .2% to .6% nitrogen, about .5 to 1.0% silicon, with the various ingredients in such proportions as to assure a substantially austenitic structure, and the remainder substantially all iron.

5. Forgeable internal combustion engine valve steels consisting essentially of about .40% to 65% carbon, about 20% to 22% chromium, about 8% to 10% manganese, about 2% to 4.5% nickel, about .35% to .45 nitrogen, about .5 to 1.0% silicon, rand remainder substantially all iron.

6. Austenitic internal combustion engine valves, valve seats, valve guides and like valve parts consisting essentially of about 0.40% to 1.50% carbon, about 12% to 30% chromium7 about 5% to 20% manganese, about 3.25% to 6% nickel, about .1% to .6% nitrogen, about .5% to 1.5 silicon, with the various ingredients in such proportions as to assure a substantially fully austenitic structure, and the remainder substantially all iron.

7. Forged internal combustion engine valves, valve seats, valve guides and the like consisting essentially of about .40% to .60% carbon, about 20% to 22% chromium, about 8% to 10% manganese, about 3.25% to 4.50% nickel, about .35% to .45% nitrogen, about .5% to 1.0% silicon, and remainder substantially all iron.

8. Austenitic internal combustion engine valves, valve seats, valve guides and like valve parts consisting essentially of about 0.40% to about 0.7% carbon, about 12% to 30% chromium, about 5% to 12% manganese, about 2% to 6% nickel, about .2% to .6% nitrogen, about .5% to 1.0% silicon, with the Various ingredients 4in such proportions as to assure a substantially austenitic structure, and the remainder substantially all iron.

9. Internal combustion engine valve part comprising an austenitic stainless steel portion and a highly alloyed facing Welded thereon, said austenitic stainless steel portion essentially consisting of about 0.40% to 1.50% carbon, about 12% to 30% chromium, about 5% to 20% manganese, about 2% to 6% nickel, about .2% to .6% nitrogen, about .5 to 1.5% silicon, with lthe various ingredients in such proportions as to assure a substantially fully austen-itic structure, and the remainder substantially all iron.

References Cited in the file of this patent UNITED STATES PATENTS 2,657,130 Jennings Oct. 27, 1953 2,698,785 Jennings Jan. 4, 1955 2,706,696 Payson Apr. 19, 1955 2,764,481 Dyrkacz et al Sept. 25, 1956 2,789,049 De Long et al. Apr. 16, 1957 2,820,725 Wasserman et al lan. 21, 1958 OTHER REFERENCES UNITED STATES P CERTIFICATE 0E Patent Noo 3l49965 ATENT OFFICE CORRECTION September 22Y 1964 Paul A, Jennings It is hereby certified ent requiring corr corrected below.

that error appears in the above numbered patectoh and that the sa id Letters Patent should read as Column .l,T line 63Y Ul4u5%h M'- a45% en for "65% read same line 65 for ".,45HM read @EAD Attest:

ERNEST W. SWlDER EDWARD J. BRENNER Allesting Officer Commissioner of Patents

Claims (1)

1. AUSTENITIC STAINLESS STEEL CONSISTING ESSENTIALLY OF ABOUT 0.45% TO 1.50% CARBON, ABOUT 12% TO 30% CHROMIUM, ABOUT 5% TO 20% MANGANESE, ABOUT 3.25% TO 6% NICKEL, ABOUT .1% TO .6% INTROGEN, ABOUT .5% TO 1.5% SILICON, WITH THE VARIOUS INGREDIENTS IN SUCH PROPORTIONS AS TO ASSURE A SUBSTANTIALLY FULLY AUSTENITIC STRUCTURE, AND THE REMAINDER SUBSTANTIALLY ALL IRON.

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