US2190486A - Austenitic chromium nickel steel alloy - Google Patents

Description

Patented Feb. 13, 1940 v I v I UNITED 'STATES PATENT OFFICE Paul Schafmeister, Essen, Germany, assignor, by mesne assignments, to Krupp Nirosta 00., Inc., New York, N. Y., a corporation of Delaware No Drawing. Application July 11, 1931, Serial No. 550,288. Renewed July 20, 1939. In Germany July 21, 930

18 Claims. (Cl. 75-128) Experience has shown that austenitic chro not become brittle when they have experienced mium nickel steel alloys thus far used for corroheating to about 500 to 900C. sion-resting material cease to be resistant against It is especially-advantageous to use as the added attack by chemical agents, lose their metallic alloy component one or both of the elements ring, become brittle, and finally even crumble columbium and tantalum, since these elements 5 to metal powder when they are exposed to a heat not only combine with the carbon in a manner treatment comparable to a drawing treatment of which does not deleteriously affect the chemical approximately between 500 to 900 C'., as, for inand mechanical stability of the alloy but they stance, in welding together of individual strucfurthermore result in particularly good welding tural sections or in use, as for instance, in a proconditions. The loss due to burning off of the m cess of hydrogenation. It has already been proelements columbium and tantalum during weldposed with considerable success that for the purng is only very Small and in fact Smaller than pose of making articles of austenitic chromium that of other elements such as zirconium, urannickel steel alloys which either in their manufacium, hafnium, cerium, thorium, lanthanum,

ture or use are exposed to a temperature compay u neodymium. Samarium, other rare rable to a drawing treatment, austenitic chroearth metals, any one or more of which may be mium nickel steel alloys should be used whose carused with columbium or tantalum, or both, to bon content is below 0.07% or which contain 'sineffect the purpose of my invention, as the advangly or together elements such as titanium or vatage of my invention is, at least to a certain exnadium which form stable chemical combinations tent, inherent also in the use of such other elel0 with carbon, the relation between titanium, rements. spectively vanadium, to the carbon being prefer-, The iron content of the alloys forming the subably such that practically the entire carbon enters jest-matter of the invention may be as low as into the inter-combination with the added ele- 50%, or even lower.

ments. The chromium content of the-alloy'may be of '25 I have found that it is not only the type of t e order of approximately 12% to 40%, the

chromium nickel steel alloys having a stable nickel content of the alloy may be of the order surface that is to say, austenitic chromium nickel of approximately 7% to 25%, while the carbon steel alloys .whicheither have a carbon content contenti's preferably less than 1%. In the preof less than about 0.07% or contain, for example, 'ferred embodiment of the invention, the alloy '80 titanium, and/or vanadium which have the adcontains about 18% chromium, 8% nickeL'bevantage that they do not lose their resistance to tween 07% and 2% carbon, and columbium or corrosive agents and do not become brittle when tantalum. or a mixture of these elements, about in manufactureor use they are exposed to tem- 3% to 2.5%. The added element or elemen s peratures comparable to drawing treatments of may be used up to 10%, and should be present in '35 about 500 to 900 C., but that this advantage is amounts at least suflicient to bind practically also inherent in austenitic chromium nickel steel all'the carbon contained in the alloy. alloys which contain one or more of the elements Austenitic chromium nickel steel, alloys, of the columbium (niobium) and tantalum. These eletype to which the present invention relates, are

40 ments also, as has been proven, form such a v in themselves well known and, as ordinarily used, '0 stable chemical combination with the carbon in contain about 12%-30% chromium. (preferably solution in the austenitic base mass that the inthe neighborhood of 18%), about 7% to. 25% chemical-and mechanical stability of the alloy nickel (preferably in the neighborhood of 8%), is not affected for practical purposes after .a heat carbon from about 07% to about .2%, and iron,

all treatment of about 500 to 900 C. In these constituting substantially the entire balance 43 cases, as in the case of titanium and vanadium, (with the exception of normal impurities), the it is also advantageous-to establish such a relairon being substantially all in the gamma form. tion of the stated alloy components with respect One of the principal uses of these alloysis in to the carbon that practically the entire amount the production of chemical apparatus of various 0 of carbon is bound to the added alloy components. types, in which sheets or plates, made of the Te ts with chromium nickel steel alloys having aalloy, are united by fusion welding. These alloys, stable surface and containing about 0.17% carhowever, if exposed to elevated temperatures or bon, 8% nickel, 18% chromium, 1.3% tantalum the approximate range of 500 to 900 C., for inplus columbium, show that such alloys still pre-' stance by uniting individual parts thereof by u serve their resistance to corrosive attack and do fusion welding, and then exposed to corrosive rosion. If they are exposed, for any appreciable length of time, to such temperaturerange, chi-o .mium carbides will precipitate 'therein, robbing the grain boundaries of their protective chromium, thus permitting intergranular corrosion to occur. The temperaure range specified .may therefore be termed the carbide precipitation range,. The difliculty caused by the formation of these carbides, could be cured, as was known, by reheating the metal to a temperature of 1000 C. or higher, and then rapidly cooling it. Such a process is, however, impracticable, if not impossible, with larger articles, not only because it is diflicult, or impossible to heat themto-the necessary high temperature, and then to cool them rapidly, but also because of the liability of distortion of the article, by its own weight, while the metal is in a softened condition.

It should be kept in mind that my invention includes articles made of austenitic chromium nickel steel alloys, to which have been added columbium or tantalum, or both, as equivalent substances,-for the purpose of combining with substantially all of the carbon present, so that the carbon will not be able to combine with the chromium, thus preventing intergranular corrosion when the alloy is subjected to the temperature range (carbide precipitation range) specified, without being thereafter necessarily further heat treated. By way of example, my alloys will thus, even on prolonged heating at a temperature such as 500 C., lessen materially loss of corrosion resistance.

The alloys, containing one or both of these addition materials, may therefore, as hereinabove stated, be used in the manufacture of metal articles, including fusion welded articles, which, in their normal use, are subjected to active corrosive influences, while the metal in at least a part thereof is in a condition resulting from heating, for instance, by fusion welding, at ranges within the carbide precipitation range, without the necessity of curing, that is, without subsequent heating at substantially higher temperatures (and then rapidly cooling); and such articles will nevertheless be resistant to corrosive influences,

that is, will not be subject to intergranular 'cor-,

rosion.

Any departure from the proportions specified in my claims which may, however, result in an alloy which exhibits the advantages of my invention, even though in a less effective manner, would still be within the spirit of my invention, and of the scope of my claims.

Articles made of the alloy hereinabove described containing zirconium as the addition material. are claimed in my divisional application Ser. No. 227,689, issued May 2, 1939, as Patent No. 2,157.060.

I claim:

1. A corrosion-resisting steel alloy containing about 12% to 30% chromium, about 7% to 25% nickel. carbon in appreciable quantity but less than 1%, and an additional material acting to lessen materially loss of corrosion resistance on prolonged holding at 500 C., in an amount sufllcient to combinev with substantially all of the carbon but not in excess of 10%, the balance being substantially all iron, such additional material consisting substantially all of columbium.

' 2. A corrosion-resisting steel alloy containing about 12% to 30% chromium, about 7% to 25% nickel, about 0.07% to 0.2% carbon, and from v 2,190,486 conditions, become liable to intergranular cor-" lessen mate'rially loss of corrosion resistance on prolonged holding at 500 0., the balance substantially all iron, saidadditional material consisting substantially all of. columbium.

3. A corrosion-resisting steel alloy containing about 18% chromium, about 8% nickel, .07% to .2% carbon and from'.3% to 2.5% ofa'nad ditional material acting to lessen materially loss of corrosion resistance on prolonged holding at 500 C., the balance substantially all iron, said additional material consistingsubstantially all of columbium.

4. A fusion Welded article composed of an austenitic corrosion resisting steel alloy containing about 12%to 30% chromium, about 7% to 25% nickel, carbon in appreciable quantity but less than 1%, and an additional material in amount suificient to combine with substantially all of the carbon but not in excessof 10%; said additional material being at least one of the elements of the group consisting of columbium and tantalum, the balance being substantially all iron. I

5. A fusion welded article composed of an aus' tenitic corrosion resisting steel alloy containing about 12% to 30% chromium, about 7% to 25% nickel, about .07% to .2% carbon, and about .3% to 2.5% of an additional material acting to lessen materially loss of corrosion resistance, the balance being substantially all iron, said additional material being at least one of the elements of the group consisting of columbium and tantalum.

6. A fusion welded article composed of an austenitic corrosion resisting steel alloy containing about 18% chromium, about 8% nickel, about .07% to .2% carbon, and about .3% to 2.5% of an additional material acting to lessen materially loss of corrosion resistance, the balance being substantially all iron, said additional material being at least one of the elements of the group consisting of columbium and tantalum.

7. A fusion-welded article composed of an austenitic corrosion-resisting steel alloy containing about 12% to 30% chromium, about 7% to 25% nickel, carbon in appreciable quantity but less than 1%, and an additional material in an amount sufficient to combine with substantially all of the carbon but not in excess of 10%, the

balance being substantially all iron, said additional material consisting substantially all of columbium.

8. A fusion-welded article composed of 'an austenitic corrosion-resisting steel alloy containing about 12% to 30% chromium, about 7% to 25% nickel, about 0.07% to 0.2%. carbon, and from 0.3% to 2.5% of an additional material acting to lessen materially loss of corrosion resistance, the balance substantially all iron, said additional material consisting substantially all of columbium.

9. A fusion-welded article composed of an austenitic corrosion-resisting steel alloycontaining about 18% chromium, about 8% nickel, 0.07% to 0.2% carbon, and from 0.3% to 2.5% of an additional material acting to lessen materially loss of corrosion resistance, the balance substansubstantially all of columbium.

10. A fusion-welded article composed of an austenitic corrosion-resisting steel alloy containing about 12% to 30% chromium, about 7% to 25% nickel, carbon in appreciable quantity but less than 1%, and an additional material in an amount suflicient to combine with substantially all of the carbon but not in excess of 10%, the

balance being substantially all iron, said additional material consisting substantially all of tantalum.

11. A fusion-welded article composed of an austenitic corrosion-resisting steel alloy containing about 12% to 30% chromium, about 7% to 25% nickel, about 0.07% to 0.2% carbon, and

from 0.3% to 2.5% of an additional material acting to lessen materially loss of corrosion resistance, the balance substantially all iron, said additional material consisting substantially all oi tantalum.

12. A fusion-welded article composed of an austenitic corrosion-resisting steel alloy containing about 18% chromium, about 8% nickel, 0.07% to 0.2% carbon, and from 0.3% to 2.5% of an additional material acting to lessen materially loss of corrosion resistance, the balance substantially all iron, said additional material consisting substantially all of tantalum.

-13. A'fusion-welded article composed of an austeniticcorrosion-resisting steel alloy containing about 12% to 30% chromium, about 7% to 25% nickel, carbon in appreciable quantity but less than 1%, and an additional material in an amount sufficient to combine with substantially all of the carbon but not in excess of 10%, the

balance being substantially all iron, said additional material consisting substantially all of columbium and tantalum.

14. A fusion-welded article composed of an austenitic corrosion-resisting steel alloy containing about 12% to 30% chromium, about 7% to 25% nickel, about 0.07% to 0.2% carbon and from 0.3% to 2.5% of an additional material acting to lessen materially loss of corrosion resistance, the balance substantially all iron, said additional material consisting substantially all of columbium and tantalum.

15. A fusion-welded article composed of an austenitic corrosion-resisting steel alloy containing about 18% chromium, about 8% nickel, 0.07% to 0.2%.carbo and from 0.3% to 2.5% of an additional material acting "to lessen materially loss of corrosion resistance, the balance substantially all iron, said additional material consisting substantially all of columbium and tantalum.

16. A metal article which, in its normal use, is subjected to active corrosive influences while the metal in at least part of the article is in a condition resulting from heating at ranges within the carbide precipitation range (approximately 500 to 900 C.) without subsequent heating at substantially higher. temperatures, said article being resistant to said corrosive influences and composed of a corrosion-resisting austenitic steel alloy, the iron of which is substantially all in the gamma form, containing about 12% to 30% chromium, about 7% to 25% nickel, carbon in appreciable quantity but less than 1%, and columbiumin an amount sufllcient to combine with substantially all of the carbon but not in excess of 10%, the balance being substantially all iron.

17. A metal article which in its normal use is subjected to active corrosive influences while the metal in at least part of the article is in a condition resulting from heating at ranges within the carbide precipitation range (approximately 500 to 900 C.) without subsequent heating at substantially higher temperatures, said article being resistant to said, corrosive influences and composed of a corrosion resisting austenitic steel alloy, the iron of which is substantially all in the gamma form, containing about 12% to 30% chromium, about 7% to 25% nickel, about .0'7% to .2% carbon, and from .3% to 2.5% of an additional material consisting substantially all of columbium, the balance being substantially all iron.

18. A metal article which, in its normal use. is subjected to active corrosive influences while the metal in at least part of the article is in a condition resulting from heating at ranges within the carbide precipitation range (approximately 500 to 900 C.) without subsequent heating at substantially higher temperatures, said article being resistant to said corrosive influences and composed of a corrosion-resisting austenitic steel alloy, the iron of which is substantially all in the gamma iorm, containing about 18% chromium, about 8% nickel, about .07% to .2% car- 'bon and about .3% to 2.5% columbium, the balance being substantially all iron.

PAUL SCI-IAFMEISTER.