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
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper

Definitions

• the steel comprises about 10 percent to 17 percent chromium, about 3.7 percent to 10 percent nickel, with or without about 2.5 percent to 5 percent copper, 0.01 percent to 0.06 percent carbon, manganese not exceeding 0.50 percent, silicon not exceeding 0.15 percent, phosphorus not exceeding 0.30 percent, sulphur not exceeding 0.020 percent, nitrogen not exceeding 0.025 percent, with or without columbium up to about 0.25 percent and with or without titanium up to about 0.15 percent, and remainder substantially all iron.
• the chromium content exceeds 13 percent and copper is present in the amount of about 2.5 percent to 5 percent
• at least three of the four ingredients manganese, silicon, sulphur and nitrogen are further limited: the manganese to 0.30 percent max., silicon 0.10 percent max. and each of sulphur and nitrogen 0.010 percent max.
• One of the objects of my invention is the provision of a chromium-nickel stainless steel which is substantially fully martensitic and is peculiarly suited to high-temperature applications over prolonged periods of time without encountering losses of strength, ductility and toughness, and especially without undue sacrifice of impact strength.
• Another object is the provision of a precipitation-hardenable chromium-nickel martensitic stainless steel which readily may be melted to desired specification, which handles well in the hot-mill and the cold-mill, which readily lends itself to a variety of forming and shaping operations and yet which may be hardened by simple treatment at rather modest temperatures to give desired hardness and strength yet with retained ductility and impact strength over prolonged periods of use.
• a further object is the provision of a precipitation-hardenable martensitic chromium-nickel stainless steel of good sustained impact strength which readily lends itself to the production of bar, rod and wire, as well as to the production of plate, sheet, strip and other converted forms, in addition to the production of castings and forgings of desired size and shape.
• a still further object of my invention is the provision of a precipitation-hardenable chromium-nickel stainless steel which in cast, forged or machined form is peculiarly suited to the production of jet engine compressor blades, discs, bearings, and the like and which in such form, moreover, is suited to the production of drive shafts and scram mechanisms of atomic reactors, and which in the form of sheet and strip is peculiarly suited to the production of frames and skin of supersonic aircraft.
• Typical of the known and used precipitation-hardenable steels is the copper-bearing chromium-nickel stainless steel essentially consisting of about 17 percent chromium, about 4 percent nickel, about 3.5 percent copper, with carbon not exceeding about 0.10 percent, and remainder iron, this being the subject of my prior U.S. Letters Patent 2,482,096 entitled Alloy and Method.
• Another is the aluminum-bearing chromium-nickel stainless steel essentially consisting of about 17 percent chromium, about 7 percent nickel, about 1 percent aluminum, with a carbon content not exceeding about 0.10 percent, and remainder iron.
• a further aluminum-bearing steel essentially consists of about percent chromium, about 7 percent nickel, about 2 percent molybdenum, about 1 percent aluminum, with a carbon content not exceeding 0.10 percent, and remainder iron.
• Another aluminum-bearing steel contains about 13 percent chromium, about 8 percent nickel, about 2 percent molybdenum, about 1 percent aluminum, with carbon not exceeding 0.10 percent, and remainder iron.
• the known titanium-bearing chromium-nickel stainless steel essentially consisting of about 18 percent chromium, about 8 percent nickel, about 1 percent titanium, and remainder iron, and the further titanium-bearing steel essentially containing about 12 percent chromium, about 9 percent nickel, about 2.5 percent copper, about 1.2 percent titanium, and remainder. iron.
• a chromium-nickel martensitic stainless steel in which the chromium and nickel contents are properly correlated one to the other and which essentially requires the presence of a small but critical amount of carbon.
• the steel moreover, essentially requires that the silicon found in all chromium-nickel stainless steels be maintained at a critically low value. And the best steel also contains copper in substantial amount.
• my steels a best combination of properties is had where the manganese content, an ingredient also found in virtually all chromium-nickel stainless steels, is maintained at a critically low value, along with a critically low sulfur content.
• the steel is substantially fully martensitic with any austenite ordinarily not over some 4 percent or 5 percent by volume. Even with unusually high temperatures of precipitation-hardening treatment, that is, about 1 F., the austenite does not exceed some 10 percent or 12 percent; certainly it is less than 15 percent.
• the precipitation-hardenable chromium nickel stainless steel according to my invention in preferred broad aspect essentially consists of about 10 percent to about 17 percent chromium, about 3.7 percent to about 10 percent nickel, about 2.5 percent to about 5 percent copper, about 0.01 percent to about 0.06 percent carbon, particularly about 0.02 percent to about 0.05 percent carbon, with a silicon content not exceeding 0.40 percent and for best results not exceeding 0.15 percent or even not exceeding 0.10 percent, and remainder substantially all iron.
• the manganese present in the steel is maintained at a value not exceeding 0.10 percent and certainly at a value not exceeding 0.40 percent or 0.50 percent.
• the phosphorus content is maintained at a value not exceeding 0.030 percent, preferably not exceeding 0.020 percent or even 0.010 percent, with sulfur not exceeding 0.020 percent, preferably not exceeding 0.005 percent or 0.010 percent. And in the best steel nitrogen should not exceed 0.010 percent; certainly, it should not exceed 0.025 percent. In my steel there may be present the ingredient columbium, this in amounts up to about 0.25 percent, and/or titanium, this in amounts up to about 0.15 percent. For I find, as more fully described hereinafter, that both columbium and titanium employed in small amount lend something to tensile strength without at the same time sacrificing ductility and resistance to impact.
• the copperfree precipitation-hardenable chromium-nickel stainless steel while of approximately the same chromium and nickel contents, actually contemplates about percent to about 12 percent or 15 percent chromium, about 4.5 percent to about 9.5 percent nickel, with a carbon content of 0.01 percent to 0.05 percent, manganese not exceeding 0.30 percent, silicon not exceeding 0.15 percent, phosphorus not exceeding 0.020 percent, sulfur not exceeding 0.010 percent, nitrogen not exceeding 0.015 percent, and remainder substantially all iron.
• manganese content of my steel is not as sensitive as the silicon content, yet I find that manganese should not exceed 0.50 percent, and for best results should not exceed 0.10 percent, for otherwise there is a loss of ductility and gain in brittleness following sustained elevated-temperature duty. In general, the same may be said with respect to the nitrogen content of my steel, for where nitrogen exceeds 0.015 percent, or even where it exceeds 0.010 percent, brittleness is detected and impact values suffer.
• the carbon content of my steel must not exceed 0.06 percent, and for best results is maintained at a value not exceeding 0.05 percent, for otherwise the steel becomes too stable. In order to assure desired transformation and precipitationhardening effect the 0.06 percent figure and preferably the 0.05 percent figure must not be exceeded. Moreover, with an excess of carbon there is noted a brittleness following prolonged use at high temperatures. A small critical amount of carbon, however, is essential to the steel of my invention, for with a carbon content less than 0.01 percent, and even less than about 0.03 percent, I note the presence of delta-ferrite and a loss of strength as well as a loss of impact resistance.
• columbium While neither columbium nor titanium is essential to the steel of my invention, for a best combination of properties I include one or both of columbium in amounts up to about 0.25 percent and titanium in amounts up to about 0.15 percent. These, too, are critical because where the columbium is in excess of about 0.25 percent and/or the titanium is in excess of about 0.15 percent brittleness seems to appear with prolonged elevated-temperature use.
• nickel of course is a necessary and essential ingredient, as pointed to above.
• the nickel content should not be less than about 3.7 percent, for with a lesser nickel content delta-ferrite appears and the hot-working properties suffer.
• the coldworkability and forrnability suffer as a result of a loss of duetility.
• the nickel content should not exceed about 10 percent, for with an excess of nickel the metal becomes fully austenitic and not subject to precipitation-hardening treatment.
• the copper-free chromium-nickel steel of my invention a somewhat higher nickel content is employed, the nickel there ranging from about 4.5 percent to about 9.5 percent, with chromium ranging from about 10 percent to about 12 percent or even to about 15 percent.
• a nickel content less than about 4.25 percent results in a sacrifice of the working and forming characteristics as noted, and a nickel content exceeding about 9.5 percent results in a steel not subject to precipitation hardening.
• the ingredient nitrogen should not exceed 0.025 percent and preferably should not exceed 0.010 percent.
• the structural balance is upset; the metal is inclined toretain too much austenite, the hot-working characteristics are adversely affected, and the metal becomes brittle and the impact strength immediately suffers.
• chromium content of the steel exceeds 13 percent, I find that it becomes necessary to further restrict at least three of the four ingredients manganese, silicon, sulfur and nitrogen in order to achieve the desired retained impact strength.
• the further limiting figure for the manganese content is 0.30 percent max., that for silicon is 0.10 percent max., and that for each of sulfur and nitrogen is 0.010 percent max., all as more particularly pointed to hereinafter.
• the steel of my invention conveniently is melted in the vacuum furnace, although, where desired, it may be melted in the electric arc furnace. I find, however, that where I melt the steel in the electric arc furnace considerable care is required in the selection of raw materials in order to enjoy the required low contents of silicon, manganese, nitrogen, sulfur and even carbon. As a practical matter, the steel is best melted in the vacuum furnace or in the electric arc furnace with subsequent remelt in the vacuum furnace. In any event, the steel is suitably produced in the form of ingots, billets or slabs which are readily converted in the mill through appropriate hotand cold-working operations into plate, sheet and strip, or into bars, rods and wire of desired specification. Of course, the steel lends itself to forging from suitable forging stock. Or it may be cast into articles of desired size and configuration.
• One steel according to my invention essentially consists of about 1 1 percent to about 16 percent chromium, about 4 percent to about 8 percent nickel, about 3 percent to about 4 percent copper, 0.02 percent to 0.05 percent carbon, with manganese not exceeding 0.30 percent, silicon not exceeding 0.15 percent, and remainder substantially all iron.
• phosphorus is in an amount not exceeding 0.020 percent and sulfur and nitrogen each is of a value not exceeding 0.010 percent.
• a somewhat better steel, that is, a steel enjoying a better combination of properties essentially consists of about 11 percent to about 15 percent chromium, about 4.5
• a further preferred steel essentially consists of about 12 percent to about 16 percent chromium, about 4 percent to about 7 percent nickel, about 3 percent to about 4 percent copper, 0.03 percent to 0.04 percent carbon, manganese not exceeding 0.10 percent, silicon not exceeding 0.15 percent, phosphorous not exceeding 0.020 percent, sulfur not exceeding 0.010 percent, nitrogen not exceeding 0.010 percent, and remainder substantially all iron.
• Such a steel sufiers very little embrittlement with prolonged use at high temperatures, as more fully appears hereinafter.
• the steel which perhaps enjoys the best combination of tensile strength and ductility, which properties are retained through prolonged use at elevated temperatures, essentially consists of about 1 1 percent to about 13 percent chromium, about 5 percent to about 7 percent or about 8 percent nickel, about 2.5 percent to about 5 percent copper, 0.02 percent to 0.05 percent and preferably 0.01 percent to 0.035 percent carbon, with manganese and silicon each not exceeding 0.10 percent, and preferably sulfur not exceeding 0.010 percent, with remainder substantially all iron. In a more preferred form of this steel columbium is present, this in the amount of about 0.10 percent to about 0.25 percent.
• such a steel in somewhat more specific composition such a steel essentially consists of chromium about 10.5 percent to about 1 1.5 percent or about 11.5 percent to about 12.5 percent, with nickel about 5.75 percent to about 8.5 percent for the one and about 5.75 percent to about 6.25 percent for the other, about 3 percent to about 4 percent copper, 0.03 percent to 0.05 percent carbon, manganese and silicon each not exceeding 0.10 percent, phosphorus not exceeding 0.020 percent, sulfur not exceeding 0.010 percent and preferably not exceeding 0.005 percent, nitrogen not exceeding 0.010 percent, and remainder substantially all iron. in this steel columbium preferably is included, this in the amount of about 0.05 percent to about 0.25 percent, for l find that with this addition the tensile strength is noticeably improved, as more particularly noted below.
• a steel enjoying a combination of tensile strength and impact strength adequate for many applications essentially consists of about 10 percent to about 12.5 percent or 13 percent 50 chromium, about 4 percent or 5 percent to about 9 percent nickel, about 2.5 percent to about 5 percent copper, 0.02 percent or 0.03 percent up to 0.05 percent carbon, manganese not exceeding 0.50 percent and preferably not exceeding 0.10 percent, silicon not exceeding 0.40 percent and preferably not exceeding 0.10 percent, phosphorus not exceeding 0.030 percent, sulfur not exceeding 0.020 percent, nitrogen not exceeding 0.015 percent, and remainder substantially all iron.
• Such a steel may be melted in the electric arc furnace.
• This steel in broad view essentially consists of about 10 percent or 1 1 percent to about 15 percent chromium, about 4.5 percent to about 9.5 percent nickel, more particularly about 5 percent to about 6 percent nickel, 0.01 percent or even 0.02 percent to 0.05 percent carbon, manganese not exceeding 0.30 percent, particularly not exceeding 0.10
• a best preferred steel of gOOd tensile strength and good sustained impact strength essentially consists of about 10 percent to about 12 percent chromium, about 4.5 percent to about 9.5 percent nickel, 0.02 percent to 0.05 percent carbon, manganese and silicon each not exceeding 0.20 percent, phosphorus not exceeding 0.020 percent, sulfur not exceeding 0.005 percent, nitrogen not exceeding 0.010 percent, and remainder substantially all iron.
• a steel of good retained impact strength but in which some loss nevertheless is observed is the 15 percent chromium steel of Heat No. 347 (15.09 percent chromium, 4.69 percent nickel, 3.20 percent copper, 0.037 percent carbon, less than 0.02 percent manganese, 0.009 percent phosphorus, 0.005 percent sulfur 0.04 percent silicon, 0.005 percent nitrogen, and remainder iron). That steel, having an impact strength of 6 172/162 ft.-lbs. prior to exposure, retains a strength of 112/112 ft.-lbs. following the 500-hour exposure. The same may be said for the 16 percent chromium steel of Heat No. 348, suffering a loss of impact strength from 182/ 1 73 ft.-lbs.
• the 0.60 percent silicon steel of Heat No. 350 (16.28 percent chromium, 4.38 percent nickel, 3.19 percent copper, 0.040 percent carbon, 0.02 percent manganese, 0.009 percent phosphorus, 0.005 percent sulfur, 0.63 percent silicon, 0.010 percent nitrogen, and remainder iron), having an impact strength of 171/151 ft.- lbs. prior to exposure, retains only a strength of 58/59 ft.-lbs. following 500-hour exposure at 800 F.
• the initial tensile strength and the initial impact strength are in favor of the columbium-bearing steel, although following prolonged high-temperature treatment little difference between the two appears either in matters of tensile properties or impact properties. It is the steels of the lower chromium and higher nickel balance l 1 percent chromium, 7 percent nickel of Heat No. 344 and 15 percent chromium, 5
• the effect of the columbium addition in my steel is perhaps better revealed by a comparative study of the several steels presented below, these having a chromium content of about 12 percent, a copper content of about 3.5 percent, with nickel contents of about 6 percent, 6.5 percent and 7 percent, and carbon contents of about 0.03 percent, 0.04 percent and 0.05 percent. in general, it appears that in all of these steels the columbium addition improves the tensile properties. In the steels of the lower carbon contents, the columbium addition has little effect on the tendency toward embrittlement with prolonged use at elevated temperatures. in the steels of the higher carbon contents the columbium has no adverse effect on impact strength, as noted hereinafter.
• Table ll(b) below the tensile properties of ultimate tensile strength in kilopounds per square inch, 0.2 percent yield strength in kilopounds per square inch, percent reduction in area, percent elongation in 2 inches and Rockwell hardness on the C-scale are given for each of the steels in the three conditions of prior-to-elevated-temperature treatment, subsequent-to-elevated-temperature treatment for 500 hours and for 1,000 hours at 800 F. Additionally, there are given in table ll(b) for all steels the impact strength prior to elevatedtemperature treatment and following the treatments at 800 F. for 500 hours and for 1,000 hours, this in terms of ft.-lbs. for the two samples of each steel.
• the columbium-bearing steel of Heat No. VR 77 having a tensile strength of 137 K s.i. prior to elevated-temperature treatment and 140 K s.i. following that treatment for 1,000 hours, is recognizably better than the 125 K s.i. tensile figurefor the steel of Heat VR 76 prior to treatment and 127 K s.i. following prolonged treatment.
• a series of six chromium-nickel-copper stainless steels of differing silicon contents, of differing nitrogen contents and of differing chromium and nickel contents is given below in table lll(a).
• the steel of low silicon and nitrogen contents, as well as low manganese and sulfur is characterized by a high retained impact strength following prolonged exposure to elevated temperatures, although one of the low-silicon steels, the steel of the lower chromium content and higher nickel content, is possessed of good retained impact strength.
• the steel of Heat No. 4734 where all four of the ingredients manganese, silicon, sulfur and nitrogen fail to meet the further restriction in composition, is characterized by poor retained impact strength. Although not quite so poor, the steel of Heat No. 4735, where three of the ingredients (manganese, silicon and nitrogen) fail to meet the further restriction, also has an unsatisfactory impact strength following prolonged heating.
• the steel of Heat No. 4736 having a chromium content under 13 percent as against the steels of Heat Nos. 4734, 4735, 4737, 4738 and V179, all with chromium contents well over 13 percent, is seen to have good retained impact strength, the initial impact strength of 79/80 ft.-lbs. falling i feel, as noted above, that my chromium-nickel-copper stainless steel, wherein the chromium content exceeds 13 percent, requires that at least three of the four ingredients manganese, silicon, sulfur and nitrogen be further limited to achieve good sustained impact values.
• This is exemplified, as pointed to above, by the Heat No. V179 of Table III(a) with the further restrictions on manganese, sulfur and nitrogen, and the Heat No. 348 of table I(a), with the further limitations on silicon, sulfur and nitrogen.
• VR 130 actually shows somewhat improved impact strength as a result of the 500-hour treatment at 800 F., the initial impact figures of 98/100 ft.-lbs. for the steel prior to exposure rising to 108/1 1 l ft.-1bs. following exposure.
• the impact strength of the 12 percent chromium steel of Heat No. VR 131 falls from 120/126 ft.-1bs. prior to exposure to the figure 1 17/99 ft.-lbs. following exposure.
• the somewhat higher initial impact strength of the steel of Heat No. VR 131 over that of the steel of Heat VR 130 I attribute to the higher carbon content, namely, 0.041 percent as compared to 0.023 percent.
• the steels of the Heat Nos. VR 138 and VR 139 having chromium contents approaching 17 percent and respectively having nickel contents of about 2 percent and about 4 percent, both have fairly good values of retained impact strength, the one initially having an impact strength of 240/240 ft.-lbs., falling to 187/126 ft.-lbs. following heating at elevated temperatures and the other having an initial impact strength of 205/207 ft.- lbs. falling to 155/130 ft.-lbs.
• the known commercial steel of Heat No. 4233 containing about 16 percent chromium, 4 percent nickel, 0.04 percent carbon, with manganese 0.25 percent, silicon 0.37 percent, sulfur 0.015 percent; columbium 0.17 percent, and nitrogen exceeding 0.025 percent, is characterized by impact properties which are wholly unacceptable. Note, for example that the impact resistance only amounts to some 42.5/37.0 ft.-1bs. prior to exposure to elevated temperatures, and that this falls to some 9.0/7.0 ft.-1bs. following a 500-hour exposure at 800 F.
• the 15 percent chromium steel of my invention Heat No. VR 134
• the 16 percent chromium steels of Heat No. VR 135 and Heat No. 4233 As noted above, the 15 percent chromium, low nitrogen steel of my invention, with initial impact strength of 143/146 ft.-lbs. prior to exposure at elevated temperatures and 78/103 ft.-lbs.
• No'rE.Heats 5713 and 6715 respectively contain titanium in amounts 9f .09% and .13%.
• the three steels of the higher nitrogen content are characterized by an impact strength which is low and which, moreover, drastically suffers with prolonged exposure at elevated temperatures.
• the 1 1 percent chromium, 8 percent nickel steel of Heat No. 713 having a nitrogen content of 0.176 percent (well above the 0.025 percent limit for all steels according to the invention) has an initial impact strength of 52/57 ft.-lbs., which with the 500-hour exposure at 800 F. falls to 19/19 ft.-lbs.
• the same effect to somewhat lesser extent is had with the 16 percent chromium, 4 percent nickel steel of Heat No. 5727 (with nitrogen exceeding the 0.010 percent max., silicon exceeding the 0.10 percent max. and sulfur exceeding the 0.010'percent max.
• the percent chromium, 5 percent nickel steel of Heat No. 5715 (with nitrogen exceeding the 0.010 percent max. and silicon exceeding the 0.10 percent max. for the steels having chromium contents exceeding 13 percent) has insuffv cient retained impact strength following prolonged high-temperature exposure.
• the low nitrogen steels according to applicants invention which additionally are low in manganese, silicon and sulfur (Heat Nos. 344 and 347) are characterized by high initial impact strengths, strengths which are substantially retained over prolonged exposure at elevated temperatures.
• the preferred steel of Heat No. 344 having a chromium content of about 1 1 percent and a nickel content of about 7 percent, and with an initial impact strength of 125/123 ft.-lbs., is seen to have an impact strength of 125/121 ft.-lbs. following the 500-hour exposure.
• the acceptable 15 percent chromium, 5 percent nickel steel of Heat No. 347 has an initial impact strength of 172/ l 62 ft.-lbs. prior to exposure, which falls only to l 12/ 1 12 ft.-lbs. upon exposure.
• Alloy steel essentially consisting of about 10 percent to about 17 percent chromium, about 3.7 percent to about 10 percent nickel, up to about 5 percent copper, 0.01 percent to 0.06 percent carbon, manganese not exceeding 0.50 percent, silicon not exceeding 0.15 percent, phosphorus not exceeding 0.030 percent, sulfur not exceeding 0.020 percent, nitrogen not exceeding 0.025 percent, and remainder substantially all iron, in which steel where the chromium content exceeds 13 percent and the copper content is about 2.5 percent to 5 percent, at least three of the four ingredients manganese, silicon, sulfur and nitrogen are further limited, the manganese to 0.30 percent max., silicon 0.10 percent max., sulfur 0.010 percent max., and nitrogen 0.010 percent max.
• Alloy steel essentially consisting of about 10 percent to about 17 percent chromium, about 3.7 percent to about 10 percent nickel, about 2.5 percent to about 5 percent copper, 0.02 percent to 0.05 percent carbon, manganese not exceeding 0.40 percent, silicon not exceeding 0.10 percent, phosphorus not exceeding 0.020 percent, sulfur not exceeding 0.010 percent, nitrogen not exceeding 0.010 percent, and remainder substantially all iron.
• Alloy steel essentially consisting of about 11 percent to about 16 percent chromium, about 4 percent to about 8 percent nickel, about 3 percent to about 4 percent copper, 0.02 percent to 0.05 percent carbon, manganese not exceeding 0.30 percent, silicon not exceeding 0.15 percent, phosphorus not exceeding 0.020 percent, sulfur not exceeding 0.010 percent, nitrogen not exceeding 0.010 percent, up to about 0.25 percent columbium, up to about 0.15 percent titanium, and remainder substantially all iron.
• Alloy steel essentially consisting of about 1 1 percent to about 15 percent chromium, about 4.5 percent to about 7.5 percent nickel, about 2.5 percent to about 5 percent copper, 0.03 percent to 0.05 percent carbon, manganese not exceeding 0.10 percent, silicon not exceeding 0.10 percent, phosphorus not exceeding 0.020 percent, sulfur not exceeding 0.010 percent, nitrogen not exceeding 0.010 percent, up to about 0.25 percent columbium, and remainder substantially all iron.
• Alloy steel essentially consisting of about 10 percent to about 13 percent chromium, about 4 percent to about 9 percent nickel, about 2.5 percent to about 5 percent copper, 0.03 percent to 0.05 percent carbon, manganese not exceeding 0.10 percent, silicon not exceeding 0.10 percent, phosphorus not exceeding 0.030 percent, sulfur not exceeding 0.020 percent, nitrogcn not exceeding 0.025 percent, and remainder substantially all iron.
• Alloy steel essentially consisting 0.020 about 12 percent to about 16 percent chromium, about 4 percent to about 7 percent nickel, about 3 percent to about 4 percent copper, 0.03 percent to 0.05 percent carbon, manganese not exceeding 0.10 percent, silicon not exceeding 0.15 percent,
• Alloy steel essentially consisting of about 10 percent to about 12.5 percent chromium, about 5 percent to about 9 percent nickel, about 2.5 percent to about 5 percent copper, 0.03
• Alloy steel essentially consisting of about 11 percent to about 13 percent chromium, about percent to about 8 percent nickel, about 2.5 percent to about 5 percent copper, 0.02 percent to 0.05 percent carbon, manganese not exceeding 0.10 percent, silicon not exceeding 0.10 percent, nitrogen not exceeding 0.025 percent, sulfur not exceeding 0.010 percent, and remainder substantially all iron.
• Alloy steel essentially consisting of about 1 1 percent to about 13 percent chromium, about 5 percent to about 7 per cent nickel, about 2.5 percent to about 5 percent copper, 0.02
• B rcent to 0.035 percent carbon, manganese not exceeding .10 percent, silicon not exceeding 0.10 percent, nitrogen not exceeding 0.025 percent, sulfur not exceeding 0.010 percent, about 0.10 percent to about 0.25 percent columbium, and remainder substantially all iron.
• Alloy steel essentially consisting of about 10.5 percent to about 1 1.5 percent chromium, about 5.75 percent to about 8.5 percent nickel, about 3 percent to about 4 percent copper, 0.03 percent to 0.05 percent carbon, manganese not exceeding 0.10 percent, silicon not exceeding 0.10 percent, phosphorus not exceeding 0.020 percent, sulfur not exceeding 0.010 percent, nitrogen not exceeding 0.010 percent, and remainder substantially all iron.
• Alloy steel essentially consisting of about 11.5 percent to about 12.5 percent chromium, about 5 .75 percent to about 6.25 percent nickel, about 3 percent to about 4 percent copper, 0.03 percent to 0.05 percent carbon, manganese not exceeding 0.10 percent, silicon not exceeding 0.10 percent, phosphorus not exceeding 0.020 percent, sulfur not exceeding 0.05 percent to about 0.25 remainder substantially all iron.
• Alloy essentially consisting of about 10 percent to about 15 percent chromium, about 4.5 percent to about 9.5 percent nickel, 0.01 percent to 0.05 percent carbon, manganese not exceeding 0.30 percent, silicon not exceeding 0.15 percent, phosphorus not exceeding 0.020 percent, sulfur not exceeding 0.010 percent, nitrogen not exceeding 0.015 percent, and remainder substantially all iron.
• Alloy steel essentially consisting of about 10 percent to about 15 percent chromium, about 5 percent to about 6 percent nickel, 0.02 percent to 0.05 percent carbon, manganese not exceeding 0.10 percent, silicon not exceeding 0.10 percent, phosphorus not exceeding 0.020 percent, sulfur not exceeding 0.010 percent, nitrogen not exceeding 0.015 percent, and remainder substantially all iron.
• Alloy steel essentially consisting of about 1 1 percent to about 15 percent chromium, about 5 percent to about 6 percent nickel, 0.02 percent to 0.05 percent carbon, manganese not exceeding 0.10 percent, silicon not exceeding 0.10 percent, phosphorus not exceeding 0.020 percent, sulfur not exceeding 0.005 percent, nitrogen not exceeding 0.010 percent, up to about 0.25 percent columbium, and remainder substantially all iron.
• Alloy steel essentially consisting of about 10 percent to about 12 percent chromium, about 4.5 percent to about 9.5 percent nickel, 0.02 percent to 0.05 percent carbon, manganese not exceeding 0.10 percent, silicon not exceeding 0.10 percent, phosphorus not exceeding 0.020 percent, sulfur not exceeding 0.005 percent, nitrogen not exceeding 0.010 percent, and remainder substantially all iron.

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