Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese

Definitions

• Chromium-nickel-manganese steel characterized by good welding properties, which steel in the as-welded condition enjoys a combination of strength, ductility and impact resistance, along with good resistance to intergranular corrosion and good resistance to general corrosive attack.
• the steel contains about 20% to 25% chromium, about 6% to 17% nickel, about 3.5% to 7% manganese, about .15% to .50% nitrogen, with carbon not exceeding about .08, and with at least one of the three ingredients molybdenum, columbium and vanadium. For a best combination of properties at least two of the three ingredients are employed.
• our invention relates to the alloy steels and, more especially, to the high-strength stainless steels.
• One of the objects of our invention is the provision of a stainless steel which is substantially austenitic under all conditions, which readily lends itself to hot-working into plate, sheet, strip or rod and wire products and which, moreover, is readily rolled or drawn in the coldmill as in the production of cold-rolled plate, sheet and strip and cold-drawn rods and wire.
• Another object is the provision of such an alloy steel which is readily fabricated into a host of articles and products of ultimate use, as by pressing, bending, cutting, blanking, tapping and the like and, moreover, is readily welded by conventional welding techniques, which fabricated articles and products possess high strength in combination with good corrosion-resistance and good resistance to intercrystalline corrosion in the as-welded condition without necessity for hardening heat-treatment.
• a further object is the provision of an austenitic stainless steel which preferably, although not necessarily, is fully austenitic and free of delta-ferrite at elevated temperatures, at room temperatures and at cryogenic temperatures, which austenitic structure is fully retained even after drastic cold-reduction.
• a further class of alloys is the chromium-nickel austenitic stainless steels, notably AISI Type 304 (18% to 20% chromium, 8% to 12% nickel, manganese 2% max., carbon 0.08% max, and remainder iron), Type 347 (17% to 19% chromium, 9% to 13% nickel, 2% max. manganese, carbon 0.08% max., with columbium-tantalum at least 10 times the carbon content, and remainder iron).
• a further and more important stainless steel is the Type 316 (16% to 18% chromium, 10% to 14% nickel, 2% to 3% molybdenum, 2% max. manganese, carbon .08% max., and remainder iron).
• a still further stainless steel is the Armco 21-6-9 (20.25% chromium, 6.5% nickel, 9% manganese, .15% to .40% nitrogen, carbon not exceeding .08%, and remainder iron).
• austenitic chromium-nickel stainless steels referred to are less costly than the nickel-base alloys, they either are lacking in weldability, are characterized by a low ratio of strength-to-weight, or have insuflicient strength to meet the requirements of many applications.
• a chromium-nickel stainless steel which is significantly leaner than the nickel-base alloys, which chromium-nickel stainless steel is substantially austenitic under all conditions, which readily lends itself to conversion in the hot-mill and the cold-mill, which lends itself to a variety of forming and fabricating operations, which is readily weldable, and which in welded condition is resistant to intercrystalline corrosion and to the general corrosion conditions encountered in the aerospace, the chemical, and a variety of industries in which welded assemblies are required.
• the chromium content of our steel ranges from about 20% to about 25%, the nickel from about 6% to about 17%, the manganese from about 3.5% to about 7% and for best results to a figure less than 6% (notably 5.9%), the molybdenum from about .5 to about 4%, the nitrogen from about .15 to about .50%, with columbium optional up to about .4% where vanadium is present in the amount of .05 to about .5 and columbium about .l% to about .7% where vanadium is optional in amounts up to about .5 with remainder substantially iron.
• the ingredient molybdenum is optional; it may be employed in amounts up to about 4%, preferably less than 3%. In short, at least one of the ingredients molybdenum, columbium and vanadium is employed.
• the carbon content of our steel is less than 08% and usually is less than .06%, preferably about .03% to .O6%. Silicon may be present in amounts up to about 1% under some circumstances, although the silicon content desirably is maintained at a value under .S% preferably about 25% to about .4% for best results.
• Phosphorus and sulphur commonly present in all stainless steels, are present in our steel up to about .060% phosphorus and up to about 0.30% sulphur. We endeavor, however, to maintain a sulphur content not exceeding about 0.20% and preferably not over about .005% in order to assure a freedom from stringer inclusions in certain applications.
• the ingredient titanium which frequently is employed in certain of the stainless steels for special purposes, is particularly avoided in our steel, for we find that titanium is inclined to give dirty metal with resulting adverse effect on corrosion-resistance.
• each of the several ingredients chromium, nickel manganese, molybdenum and/ or columbium and/ or vanadium and nitrogen is critical to the steel of our invention. None of these may be dispensed with. And by the same token, the percentage ranges of none may be departed from without a loss or sacrifice of one or more of the desried properties.
• a preferred steel according to our invention essentially consists of about 21% to about 25% chromium, about 7.5% to about 16% nickel (especially about 9.5% to about 15.5% nickel), about 4% to less than 6% manganese, at least two of the ingredients molybdenum, columbium and vanadium, with molybdenum about 1% to about 3% (or about 1.5% to about 2.5% molybdenum) about .2% to about .4% columbium, about .1% to about .S% vanadium, about to about .40% nitrogen, silicon less than .5 (especially not over .4% and preferably .25% to .4%), carbon not over about .06% (especially carbon about .03% to about 0.6%), and remainder essentially iron.
• This steel is possessed of good corrosion-resistance even
• a further preferred steel we employ about 20.5% to about chromium, about 11% to about 13% nickel, about 4.5% to about 5.5% manganese, about 1.5% to about 2.5% molybdenum, about 20% to about .40% columbium and/or about 0.5% to about .40% vanadium, about 20% to about .40% nitrogen, carbon up to about .05%, and remainder essentially iron.
• the preferred steel additionally is found to be wholly austenitic and non-magnetic, even after having suffered a cold-reduction of as much as 60%.
• a further ferrite-free steel that is, a steel which is wholly austenitic, essentially consists of about 23.5% to about 24.5% chromium, about 13% to about 15.5% nickel, about 4.5% to about 5.5% manganese, about 1.75% to about 2.25% molybdenum, about .15% to about 30% columbium, about .10% to about 30% vanadium, about 30% to about .40% nitrogen, with a carbon content not exceeding about .06%, and remainder essentially iron.
• a still further steel which, although not entirely free of ferrite nevertheless is useful in most applications, essentially consists of about 23% to 24% chromium, about 9.5% to about 10.5% nickel, about 4.5% to 5.5% manganese, about 1.75 to about 2.25% molybdenum, about .15% to about 25% columbium, about .15% to about 25% vanadium, about 30% to about .40% nitrogen, with carbon not exceeding about .06%, and remainder substantially all iron.
• This steel is of desired corrosionresistance and strength, and additionally is of minimum cost; i.e., it requires a minimum of the costly alloying ingredients nickel, molybdenum, columbium and vanadium.
• Other particular steels according to our invention are described hereinafter.
• the chromium, the nickel, the manganese, the molybdenum, the columbium, the vanadium, and the nitrogen contents of our steel are in every sense critical, and so too the carbon content.
• the ranges of any one of these purposefully added ingredients are departed from there is a loss or sacrifice of one or more of the desired properties.
• the chromium content Where the chromium is less than about 20% there is a loss of the desired general corrosion-resisting properties.
• the nickel content of our steel ranges from about 6% to about 17%, preferably about 9.5% to about 15.5%, as noted.
• the nickel content of our steel ranges from about 6% to about 17%, preferably about 9.5% to about 15.5%, as noted.
• the steel loses its austenitic character, that is, delta-ferrite appears and the steel becomes slightly magnetic.
• an excess of nickel that is, nickel exceeding about 17%, or even where in excess of about 15.5% or about 16%, there is a loss of strength which we in part attribute to the restricting effect of nickel on the solubility for carbon and nitrogen.
• nickel is desirably kept down to such level as to balance the chromium and molybdenum contents of the steel and maintain the desired fully austenitic structure. Any excess of nickel, of course, makes the steel unnecessarily costly.
• the manganese content of our steel ranges from about 3.5% to about 7% and especially to something short of 6% (notably 5.9%), we prefer a manganese content from about 4% to less than 6% or even about 4.5% to about 5.5%.
• a manganese content short of about 3.5% it becomes difficult to retain the necessary nitrogen content and the metal is inclined to become gassy and porous, with undesired loss of mechanical properties. And, too, with insufficient manganese the weldability of the metal directly suffers.
• an excessively high manganese content that is, a manganese content of 6% or more, and certainly a manganese content exceeding about 7%, the steel is inclined to become ferritic and the corrosion-resisting characteristics are adversely affected.
• the steel loses its resistance to intercrystalline corrosion, especially in the sensitized condition, that is, after heating at a temperature of about 1250 F., as encountered, for example, in a welding operation.
• molybdenum is employed in our steel, this in an amount of about .S% to about 4%, and more especially in the amount of about 1.5% to about 3% or about 1.5% to 2.5%.
• molybdenum gives a higher tolerance for carbon and as a result improves the resistance to intercrystalline corrosion following welding or other heating. At least about 1% molybednum usually is necessary to give any significant benefit.
• the ingredient molybdenum also contributes to the strength of the steel, improves the general corrosion-resistance, and lowers the tendency of the metal to pit in corrosive media.
• molybdenum is present in an amount exceeding about 4%, or even about 3%, it becomes difiicult to maintain the austenitic structure of the metal without resorting to an increase in nickel, this at further cost and other undesired result. Actually, we find little increased benefit with a molybdenum content over about 2.5%. Where one or more of the desired properties of our steel may be sacrificed in favor of a lower cost the molybdenum may be omitted in favor of an addition of both columbium and vanadium as pointed to above and more fully developed hereinafter.
• Both the nitrogen content and the carbon content of our steel likewise are critical.
• a nitrogen content in the amount of about .15 to about .50%, more especially about .20% to about .40%, although a best combination of properties is had with a nitrogen content of about 30% to about .40%.
• Nitrogen serves to increase the strength of the steel, this without adversely affecting either the general corrosion-resistance of the metal or the resistance to intercrystalline corrosion following a welding or other heating. With a nitrogen content less than about .20%, and certainly with a nitrogen content less than about .15 there is no significant benefit. But where the nitrogen content exceeds about .40%, and especially where it exceeds about .50%, the corrosion-resistance suffers and, too, there is the danger of the metal becoming gassy, with untoward results as noted above.
• the carbon content of our steel preferably is maintained at a value not exceeding .05
• the steel is essentially insensitive to intercrystalline corrosion, although it may amount to as much as .06% where the chromium content and the molybdenum content are on the high side. And where the columbium and vanadium contents also are on the high side, the carbon content may very well amount to something less than .08%.
• a carbon content of .08% or more the corrosion-resisting properties directly suffer; more particularly, there is a loss of the general corrosion-resisting characteristics of the steel as well as a loss of its resistance to intercrystalline attack. Certain benefits are bad by employing at least about .03% carbon, this ranging up to about .06%; a purposeful carbon content helps to maintain the desired austenitic structure and lend strength to the metal.
• columbium and vanadium are employed in our steel.
• molybdenum is omitted from the steel both columbium and vanadium are used together, as noted above.
• vanadium is present in the amount of about .05% to about .5%
• columbium is employed in amounts up to about .4%.
• columbium is employed in amounts of about 2% to about .4%
• vanadium may be used in amounts up to about .5%.
• the desired columbium addition very well may interact with the molybdenum present in the preferred steel, giving some solution-hardening effect.
• the columbium addition although significantly less than the stoichiometric requirement of the carbon present, contributes to the strength of the steel and at the same time gives resistance to intercrystalline corrosion.
• the columbium-bearing steel is of somewhat finer grain structure, especially in the flat-rolled products, particularly sheet and strip.
• a best combination of mechanical strength and corrosion-resistance is has where both columbium and vanadium are employed in the steel, the columbium there being in the amount of about .15 to about 30% and the vanadium being in the amount of about .10% to about 30%.
• silicon In our steel the ingredient silicon usually is employed in purposeful amount. In general this amounts to about .25 to about .40%, although for certain applications, i.e., resistance to corrosion by the combustion products of the leaded fuels, silicon may be as low as .1%, or even less. Silicon permissibly may be employed in amounts up to 50% as a maximum, however, for we find that with higher silicon contents, that is, silicon above 50%, and certainly in amounts exceeding .7%, there is an inclination toward the development of the sigma phase. And we find that intergranular corrosive attack of the metal increases where the silicon content is in excess of 50%. Silicon in the amount of about .40% serves to assure clean metal, metal substantially free of oxide consistrons.
• the phosphorus and sulphur contents of our steel are low, the phosphorus being permissibly present in amounts up to .030% and the sulphur in amounts up to .020%. Larger amounts of these ingredients appear to lower the general corrosion-resisting qualities of the steel.
• the steel of our invention is melted in the electric arc furnace or in the induction furnace in accordance with known melting practices.
• the vacuum furnace generally is not suited to the melting of our steel because the vacuum operation eliminates some of the nitrogen and manganese necessary and essential to the steel.
• the steel is cast into ingots which in due course are converted into slabs, blooms and billets. As desired, these are reheated and the metal hot-rolled into plate, sheet, strip, bars, rod and wire. These products conveniently are further converted into cold-rolled plate, sheet and strip or cold-drawn wire.
• the metal works well in both the hot-mill and the cold-mill.
• the billets may be converted into forging stock and fashioned into a variety of products.
• the metal may be remelted and cast into a variety of cast articles. Both the forgings and the castings may be finished by known machining and finishing operations.
• the steel of our invention is supplied to various customer fabricators in the form of plate, sheet, strip, bars, rod, wire and the like. It is supplied in the hot-rolled condition or, as desired, it is supplied in the cold-rolled or cold drawn, annealed and pickled condition, with annealing at a temperature of about 1700 F. to 2100 F.
• the steel may be supplied the customer in the form of sheet and strip which have been lightly cold-rolled following annealing and pickling.
• the steel of our invention readily lends itself to a variety of forming operations as noted above, i.e., pressing, bending, drawing, shearing and threading. Moreover, it readily may be brazed or welded as in the fabrication of a variety of products, apparatus and equipment of ultimate use.
• Table 1(a) a series of chromium-nickel-manganese-molybdenum-nitrogen alloy steels of closely related compositions.
• Most of these steels are of such chemical composition that there is enjoyed a combination of many, if not all, of the desired properties of our preferred steel, and are considered to be according to our invention.
• the others are of such composition that they are deficient in properties, with composition falling outside of the acceptable steels of our invention in the matter of one or more of the ingredients employed.
• R6765 and R6767 additionally contain the ingredient columbium, and both steels possess the same or greater strength than the others listed, it rather clearly appears that the higher columbium content does not benefit the resistance to corrosive attack. Because of the greater strength in combination with greater ductility had in these three steels, however, they are suited to many useful applications where welding is not involved.
• the five steels R6766, R6844, R6845, R6862 and R6863 steels which enjo a best combination of properties, have chromium contents ranging from the 21.33% chromium of the steel of Heat No. R6844, with a nickel content of 11.20%, to 23.21% chromium with a nickel content of 12.24% for the steel of Heat No. R6863.
• the carbon contents of these five steels range from 033% for Heat No. R6766 down to 022% for Heat No. R6863.
• the manganese contents all are on the order of about 5%, with nitrogen about .3% and molybdenum about 2.8% (although the Heat Nos.
• R6862 and R6863 are of lower molybdenum content), some with and some without a columbium addition. All five steels are characterized by a low rate of corrosive attack in sensitized condition, as well as being substantially austenitic, that is, with a ferrite content not exceeding about 5%. Moreover, the strength is high, this being best for the steels with a columbium content, that is, a columbium content of .16% for the Heat No. R6862 and .31% for the Heat No. R6863.
• the steel according to our invention which is characterized by a combination of resistance to intergranular corrosive attack in the sensitized condition, a substantially austenitic structure and good tensile properties, employs a chromium content of about 21% to 23% or more, a nickel content of about 11% to about 13%, along with a carbon content not exceeding about 04%, a manganese content of about 5%, a nitrogen content of about 3%, a molybdenum content of about 2% to about 3%, with or without a columbium content of about .1% to about 3%.
• such as steel essentially consists of about 21% to about 24% chromium, about 11% to about 13% nickel, about 4.5% to about 5.5% manganese, carbon not exceeding about 05%, a silicon content not exceeding .4%, with about .25% to about .4% nitrogen, about 2% to about 3% molybdenum, with or without columbium up to about .4%, and remainder substantially all iron.
• a more preferred steel a steel which is wholly austenitic under all conditions and which is virtually insensitive to corrosive attack in the sensitized condition is illustrated in the six examples of specific steels set out in Table 11(a) below.
• Such a steel essentially consists of about 23% to about 24% chromium, about 15% to about 16% nickel, about 4.5% to 5.5% manganese, about 025% to 035% carbon, about .3% to .4% nitrogen, about 2.5% to 3% molybdenum, with columbium in amounts up to about .5 and remainder substantially all iron.
• the preferred steel according to our invention represents a best combination of austenitic structure, virtual freedom from intergranular attack in the sensitized condition, that is, a low Huey rate of attack, a minimum of precipitated carbides after sensitization as reflected by the Solar Carbide rating and good mechanical properties,
• the Huey rating in IPM for the steels in sensitized condition that is, sensitized at 1250 F. for one hour and air cooled
• the Solar Carbide rating of these steels in the sensitized condition the Solar Carbide rating of these steels in the sensitized condition
• the ferrite content the percent magnetism of the steels in a 60% cold-rolled condition and in the annealed and pickled condition are given below in Table III(b).
• All seven of the above steels have a chromium content of about 20.5% to about 22%, a nickel content of about 6% to about 9%, a manganese content of about 3.8% to something just short of 6%, with a carbon content not exceeding about 05%, a nitrogen content of about 3% and with two or more of the ingredients molybdenum, columbium and vanadium, and the remainder substantially all iron.
• 4303-3 contains the ingredients chromium, nickel, manganese, carbon and nitrogen in the amounts of about 21% chromium, about 6% nickel, about 4% manganese, about .05% carbon, together with both of the ingredients columbium and vanadium, one in the amount of about .15% and the other in the amount of about .2%. Molybdenum is absent.
• the steel of Heat No. 4311-3 while of like chromium, manganese, carbon, nitrogen, columbium and vanadium contents, with an absence of molybdenum, employs nickel in the amount of about 9%.
• the steels of Heats 4312-2 and 4312-3 while similarly employing about 21% chromium, about 9% nickel, about 4% manganese, about .05 carbon, about .3% nitrogen, both employ molybdenum in the amount of about 2.2%, with the one additionally employing columbium in the amount of .1% and the other additionally employing both of the ingredients columbium in the amount of about .1% and vanadium in the amount of about .2%.
• the first steel employs columbium in the amount 13 of about .1%
• the third steel the ingredient vanadium in an amount of about .4%
• the second steel both of the ingredients columbium and vanadium, one in the amount of about .1% and the other in the amount o about .2%.
• the single Heat No. 4304-3 employing all three of molybdenum, columbium and vanadium, while of greatest strength, has a rather high Huey rate and is substantially magnetic. Nevertheless, as noted, the steel is suited to many applications.
• the steels having a chromium content of about 21%, with a manganese content of about 4% and a nickel content of about 9% are in full accordance with the teachings of our invention where they employ both columium and vanadium with molybdenum absent (Heat 4311-3) or with molybdenum present (Heat 4312-3). The same may be said for the steel containing molybdenum together with columbium (Heat 4312-2).
• the steel of Heat No. 4311- 1 employing none of the ingredients molybdenum, columbium and vanadium, is deficient in properties and lies outside the scope of our invention.
• the steels having the higher nickel content of about 9%, with a chromium content of about 21%, a manganese content of about 6%, a carbon content of about .05 and a nitrogen content of about .3% enjoy a best combination of properties only where there additionally is included the ingredient molybdenum in the amount of about 2% and one or both of the ingredients columbium and vanadium. Nevertheless the steels containing one or both of columbium and vanadium without molybdenum (Heat Nos. 4290-2, 4290-3 and 4319-3) as well as the steel with molybdenum but without either columbium or vanadium (Heat No. 4292-1) are suited to many uses. The steel which contains none of the ingredients molybdenum, columbium and vanadium (Heat No. 4290-1) is deficient.
• the steel of our invention employs a manganese content of at least 3.5% to somewhat less than 6 with a nickel content of some 6% to 9%, along with a chromium content of about 20.5% to 22%, a carbon content not exceeding about .06%, a nitrogen content of about .3%, say 25% to .4%, with at least two of the ingredients molybdenum, columbium and vanadium, the molybdenum in the amount of about 1.5 to 2.5%, the columbium in the amount of about .2% to about .4% and the vanadium in the amount of about .1% to about .5
• the phosphorus, the sulphur and the silicon contents are low, as noted above.
• the ferrite content, the magnetic content of the steel in the cold-rolled condition, that is, with a reduction of about 60%, and the Huey rate in inches per month in the sensitized condition, that is, heating at 1250 F. for one hour and air cooling, are given below in Table IV(b).
• Such steels more broadly, essentially consist of about 21.5% to about 24% chromium, about 7% to about 8% nickel, about 4.5% to 5.5% manganese, about .2% to about .40% nitrogen, about .5% to about 1.5% molybdenum, about .2% to about .4% columbium, about .1% to about .4% vanadium, carbon not exceeding about .06% and remainder iron.
• the steels having substantially higher nickel content that is, a nickel content of about 9%, are seen to have an objectionably high rate of corrosive attack in the sensitized condition until the chromium content amounts to about 23.7% and more (Heat No. 4453-3), although where the ingredient vanadium additionally is present a somewhat lesser chromium content, that is, 22.3%, is found sufiicient (Heat Nos. 4454-2 and 4454-3).
• the small amount of vanadium requires a somewhat lower chromium content or an increase in nickel.
• These steels of the higher nickel contents essentially consist of about 22% to about 24% chromium, about 9% to about 10% nickel, about 4.5% to about 5.5% manganese, about .2% to about .4% nitrogen, about 1% to about 2% molybdenum, about .2% to about .4% columbium, about .1% to about .4% vanadium, with carbon not exceeding about .05%, and remainder iron.
• the steels having a nickel level of about 7.3% and as much as 21.7% chromium are sensitive to intercrystalline attack in the sensitized condition unless the vanadium is persent in an amount of at least about 2% (Heat Nos. 4456-2, 4456-3, 4457-2 and 4457-3).
• the low vanadium content that is, about .1% (Heat No. 4457-1) the steel is characterized by an objectionably high rate of attack even through the columbium content amounts to about .7%.
• the steels of the 7.3% nickel content in which columbium is absent but in which vanadium is present (Heat Nos. 4458-1, 4458-2 and 4458-3) all are characterized by good resistance to corrosive attack in the sensitized condition, the Heat No. 4458-2 appears to possess somewhat lower yield strength at elevated temperatures (37,400 p.s.i.).
• a good combination of resistance to corrosive attack in the sensitive as-welded condition of the metal in combination with good general resistance to corrosive attack and to pitting, together with good tensile strength at room temperature and at elevated temperatures is had in the steels having a carbon content not exceeding about .06%, and preferably not exceeding about .05 (although preferably being at least .03% this with a chromium content of about 22.5% to 24.5 a manganese content of about 4.5% to 5.5%, a nickel content of about 7.5% to some 15.5% a molybdenum content of about .5 to something less than 3%, a nitrogen content of about .3% to about .4%, with columbium and/or vanadium, with the columbium in the amount of about .l% to .5%, particularly .2% to .4%, and the vanadium from about .1% to .5 and remainder substantially all iron.
• the sulphur, the phosphorus and the silicon contents are low, the phosphorus being up to about .060%, the sulphur up to about .030% and the silicon up to about .40%, in any event, a figure below .5 and certainly below 1%.
• a best combination according to our invention not only is either substantially or fully austenitic under all conditions, but also is comparatively insensitive to intercrystalline corrosion in the sensitized condition, is possessed of high strength at room temperatures and at elevated temperatures as well, has a high level of general resistance to corrosion, and is particularly free of pitting under the corrosive conditions encountered in use.
• Such a steel employs a molybdenum content of about 1.5% to about 2.5%, along with a chromium content of some 23.5% to about 24.5%, a nickel content of at least about 9.5% up to about 15.5%, a manganese content of about 4.5% to about 5.5%, a carbon content not exceeding about .06%, a nitrogen content of about .3% to .4%, with one or both of the ingredients columbium and vanadium.
• the columbium content ranges from about .1% to about .3% and the vanadium content ranges from about .2% to about .4%.
• the phosphorus and sulphur contents are low and the silicon content is about .4%, or not exceeding .5%.
• the steels with nickel contents of and above are characterized by low Huey rates, low ferrite contents, low magnetism in the cold-rolled condition, and high yield strength, both at room temperatures and at elevated temperatures. It is to be particularly noted that it is the steels having a nickel content of some 11.5% to 15.5% which are substantially wholly austenitic (Heat Nos. 4639 3, 46403, 4641-3, 4642-1, 46422 and 46423), the wholly austensitic structure being assured in the three latter steels wherein the nickel ranges from about 13% to 15 .5% and wherein there is contained both of the ingredients columbium and vanadium in the amounts noted above. Best strength, however, is had in those steels wherein columbium about .15% to about .25 is present but vanadium is absent and wherein the nickel content is on the low side (Heat No. R46391).
• a best steel according to our invention in addition to enjoying a surprising combination of strength, ductility, resistance to corrosion in the sensitized condition, and a substantially fully austenitic structure even after drastic cold-reduction, also is characterized by good resistance to corrosive attack by common acids and salts, such as sulphuric acid, hydrochloric acid and ferric chloride.
• common acids and salts such as sulphuric acid, hydrochloric acid and ferric chloride.
• Norm-Specimens are electrolytically activated for the 3rd, 4th and 5th periods. Where specimens exhibited both active and passive conditions, both rates are shown.
• a best steel according to our invention essentially consists of about 23% to about 24% chromium, about 12% to about 14% nickel (more especially about 13% to about 14% nickel), about 4.5% to about 5.5% manganese, about .2% to about .4% nitrogen, about 1.7% to about 2.9% molybdenum (more especially 1.75% to 2.75% molybdenum), about .1% to about .4% columbium (more especially about .2% to about .3% columbium), with or without about .1% to about .4% vanadium (especially about .1% to about .3% vanadium included), carbon not exceeding .67%, and remainder substantially iron.
• our steel is particularly suited to the production of ducting and tubing operating at elevated temperatures, that is, temperatures approaching 1000 F., the ducting and tubing being utilized either in the annealed condition or in the cold-drawn condition. It is particularly suited for pneumatic and structural ducts.
• Our steel also is suited to use in the form of clamps and bellows. Moreover, it is suited to the production of tankage for defoliation chemicals, aswell as tankage, tubing, bellows and the like in various cryogenic applications.
• our steel is eminently suited to the many varying applications where standard austenitic stainless steels are used but where additional strength and/or less weight are found desirable, for our steel enjoys a rather high ratio of strength to weight.
• the steel is characterized by resistance to intercrystalline corrosion in the sensitized condition, that is, in the condition following a welding operation, as well as good general corrosion-resistance under the conditions encountered in use.
• Alloy steel of improved resistance to intergranular corrosion having a tensile strength exceeding some 100,-
• Alloy steel of improved resistance to intergranular corrosion having a tensile strength exceeding some 100,000 p.s.i. at room temperatures together with an elongation in 2" of at least about 30% and essentially consisting of chromium about 21% to about 25%, nickel about 7.5% to about 16%, manganese about 4% to less than 6%, nitrogen about .20% to about .40%, at least two ingredients selected from the group consisting of molybdenum, columbium and vanadium wherein molybdenum is about 1% to about 3%, columbium about .2% to about .4% and vanadium about .1% to about .5%, with carbon not exceeding .03%, silicon up to about .4%, and remainder substantially all iron.
• Alloy steel of improved resistance to intergranular corrosion having a tensile strength of at least about 125,000 p.s.i. with an elongation in 2" of at least about 30% and essentially consisting of about 22.5% to about 24.5% chromium, about 7.5% to about 15.5% nickel, about 4.5% to about 5.5% manganese, about .3% to about .4% nitrogen, about .5 to less than 3% molybdenum, at least one of the ingredients selected from the group consisting of columbium and vanadium wherein columbium is about .1% to about .5% and vanadium about .1% to about .5%, carbon not exceeding about .06%, silicon less than .5 and remainder substantially all iron.
• Alloy steel of improved resistance to intergranular corrosion having a tensile strength exceeding some 100,000 p.s.i. at room temperatures together with an elongation in 2" of at least about 30% and essentially consisting of about 20.5% to about 25% chromium, about 11% to about 13% nickel, about 4.5% to about 5.5% manganese, about .20% to about .40% nitrogen, about 1.5 to about 2.5% molybdenum, at least one of the ingredients selected from the group consisting of columbium and vanadium wherein columbium is about .20% to about .40% and vanadium about .05 to about .40%, carbon not exceeding about .05%, and remainder substantially all iron.
• Alloy steel of improved resistance to intergranular corrosion having a tensile strength exceeding some 100,000 p.s.i. at room temperatures together with an elongation in 2" of at least about 30% and essentially consisting of about 23% to about 25% chromium, about 11.5% to about 15.5% nickel, about 4.5% to about 5.5% manganese, about .30% to about .40% nitrogen, about 1.5 to about 2.5 molybdenum, at least one of the ingredients selected from the group consisting of columbium and vanadium wherein columbium is about .15 to about 30% and vanadium about .10% to about .50% with carbon not exceeding about .05%, and remainder substantially all iron.
• Alloy steel of improved resistance to intergranular corrosion having a tensile strength exceeding some 100,000 p.s.i. at room temperatures together with an elongation in 2" of at least about 30% and essentially consisting of about 20.5% to about 22% chromium, about 6% to about 9% nickel, about 3.5% to less than 6% manganese, about .25% to about .4% nitrogen, with at least two of the ingredients selected from the group consisting of molybdenum, columbium and vanadium wherein molybdenum is about 1.5% to about 2.5%, columbium about .2% to about .4% and vanadium about .1% to about .5%, carbon not exceeding about .06%, and remainder substantially all iron.
• Alloy steel of improved resistance to intergranular corrosion having a tensile strength of at least about 125,000 p.s.i. with an elongation in 2" of at least about 30% and essentially consisting of about 23.5 to about 24.5% chromium, about 9.5 to about 15.5 nickel, about 4.5% to about 5.5% manganese, about .3% to about .4% nitrogen, about 1.5% to about 2.5% molybdenum, at least one of the ingredients selected from the group consisting of columbium and vanadium wherein columbium is about .1% to about .3% and vanadium about .2% to about .4%, carbon not exceeding about .06%, and remainder substantially all iron.
• Alloy steel of improved resistance to intergranular corrosion having a tensile strength of at least about 125,000 p.s.i. with an elongation in 2" of at least about 30% and essentially consisting of about 23.5% to about 24.5% chromium, about 10% to about 12% nickel, about 4.5 to about 5.5 manganese, about .3% to about .4% nitrogen, about 1.75 to about 2.25 molybdenum, at least one of the ingredients selected from the group consisting of columbium and vanadium wherein columbium is about .15% to about .25% and vanadium about .15 to about .30%, carbon not exceeding about .05 and remainder substantially all iron.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Heat Treatment Of Steel (AREA)
• Metal Extraction Processes (AREA)

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• 1968
  • 1968-04-30 US US725516A patent/US3592634A/en not_active Expired - Lifetime
• 1969
  • 1969-04-03 GB GB1259490D patent/GB1259490A/en not_active Expired
  • 1969-04-24 FR FR6913057A patent/FR2007566A1/fr active Pending
  • 1969-04-29 SE SE06114/69*A patent/SE352663B/xx unknown
  • 1969-04-29 DE DE19691921790 patent/DE1921790A1/de active Pending
  • 1969-04-30 JP JP44033534A patent/JPS5024886B1/ja active Pending

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