US3795507A - Semi-austenitic cr-ni-al-cu stainless steel - Google Patents
Semi-austenitic cr-ni-al-cu stainless steel Download PDFInfo
- Publication number
- US3795507A US3795507A US00240292A US3795507DA US3795507A US 3795507 A US3795507 A US 3795507A US 00240292 A US00240292 A US 00240292A US 3795507D A US3795507D A US 3795507DA US 3795507 A US3795507 A US 3795507A
- Authority
- US
- United States
- Prior art keywords
- steel
- austenitic
- maximum
- exceeding
- semi
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
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
-
- 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
- C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
Definitions
- a semi-austenitic chromium-nickel-aluminum stainless steel consisting essentially of, by weight percent, about 7.0-18.0% chromium, about 6.0-12.0% nickel, about .5-2.5% aluminum, manganese and silicon each not exceeding about 1.0%, carbon not exceeding about 042%, phosphorus not exceeding about 040%, sulfur not exceeding about .015%, nitrogen not exceeding about .05%, molybdenum up to about 8.0%, about l.0-3.0% copper, about .0005-.003% boron, and the balance essentially iron.
- Said steel, in the precipitation hardenable conditions is characterized by a U.T.S.
- the family of precipitation hardening stainless steels which includes the Cr-Ni-Al steels of this invention, may be classified into three distinct groups, each characterized by a particular crystalline structure and a thermal treatment to achieve the superior properties. While each is generally known in the prior art, a brief description may help in the understanding of the present invention.
- One member of the family is the austenitic PH stainless steels which are characterized by an austenitic crystaline structure at all times throughout its processing and heat treatment. The hardening reactions are achieved by means of a single heat treatment.
- a second member is the martensite grades which are never austenitic at room temperature. In fact, the crystalline structure is always substantially martensitic.
- the thermal treatment involves a single step.
- the final member of the family is the semi-austenitic grades, the steels of the present invention. While greater detail will be given hereinafter, these steels may be solution treated to yield a stable austenitic structure. However, they can be heat treated to a martensitic structure by a suitable thermal treatment, then staged to high strength levels. In the practice known to the prior art, this treatment is termed a double heat treatment.
- the semi-austenitic precipitation hardening stainless steels precipitation hardening hereinafter referred to as PH, captured the imagination of designers looking for materials which possessed high strength at elevated temperatures, along with resistance to corrosive environments.
- Such steels combine the advantages of the wellknown AISI 300 and 400 series stainless steels.
- the production of these PH stainless steels was not without the imposition of critical controls to develop the outstanding properties.
- the high strength in these ice steels is achieved by a heat treatment which includes three essential steps.
- the steels of this invention possess certain advantages over the standard stainless steels and others of the precipitation hardening varieties.
- the steel may be shipped from the producing mill in very cold weather without the risk of premature hardening. After forming or fabrication the material may then be given the first of said three treatments.
- the treatments may be continued to develop the desired high strength and toughness.
- the carbon content plus six (6) times the boron content should not exceed about .045, preferably no greater than about .042.
- the steel in the form of plate, sheet, strip, bars, rods, wire and the like is given an annealing or solution-treatment at a temperature in the range of about 1800 F.2000 F.
- a treatment may be afiected either by the steel producer or the customer-fabricator.
- the material in this condition is ideally suited for fabrication, as the steel has a relative softness on the order of about R 80-90.
- the annealing or solution-treatment apparently places the metal in an austenitic condition in which the aluminum and copper content of the steel are dissolved. Upon quenching the steel, the aluminum and copper constituents remain in solution. Thus, since the steel is essentially austenitic at this stage, it is relatively soft, ductile and readily formable to the shapes and sizes desirable.
- one of the significant steps of this total heat treating cycle is a refrigeration treatment which results in the transformation of the austenite to martensite. Accordingly, unless a proper balance is maintained in the steel of this invention, the shipment of the steel in the solution-treated condition might encounter cold weather, which could result in a partial transformation of the material or the steel might be so stable as to preclude good heat treatment response.
- chemistry balancing is critical within the ranges stated above. For example, the total alloy content, as well as the austenite-ferrite balance isv critical. If the austenite balance (C, Ni, Mn, Cu, N) is too high at a given ferrite level (Cr, Si, Al, M0), the steel is too stable to transform.
- austenite-conditioning heat treatment at a temperature on the order of about 1300 F.-1750 F. for a period of time of at least one hour.
- the steel is cooled or refrigerated at a sub-zero temperature of about F. for about eight hours, to effect the transformation from austenite to martensite.
- Final hardening of the steel is achieved by reheating the material at a temperature of about 700 F. to about 1200 F. and cooling to room temperature. Ordinarily, the preferred heating range is between about 900 F. to 1050 F. for about one hour.
- This treatment results in a material having a hardness on the order of R 40-53, a U.T.S. of at least 230 k.s.i., and a toughness of 1000 as measured in W/A [in.-lbs./in.
- the amounts of chromium, nickel, aluminum and copper employed in the steel of this invention and the correlation between same are particularly critical.
- the desired resistance to corrosion is not achieved.
- the structural balance of the steel is upset, with a resultant loss in hardness in the precipitation-hardened condition.
- the chromium be present in an amount between about 10.015.0%, or more preferably at least 13.5-15.0%.
- nickel is used than the prescribed minimum a tendency towards instability results and the steel inclines to harden prematurely in cold Weather.
- the nickel be present in an amount between about 7.0-l0.0%, or more preferably in the range between about 7.25-8.75
- the copper and aluminum content While there may be some latitude with respect to the copper and aluminum content, it is believed that these ingredients which when found in the steel of this invention precipitate as an intermetallic compound, such as with nickel, to develop the higher final strengths obtained by the final agging treatment. Therefore, it is important to maintain the copper and aluminum within the prescribed limits so as not to disturb the structural balance and resulting undesired change in the overall mechanical properties.
- the inclusion of the interstitial elements are not without significance in the attainment of the properties of the steel of this invention.
- the carbon content as noted above, must not exceed 0.042%, by weight, for the carbon-boron relationship will be exceeded and the toughness of the steel lowered. From the standpoint of mere toughness, the lower carbon contents are desirable, even though this may result in a lowering of the strength. Thus, while lower carbons are desirable, it is preferred that at least .02% be included.
- Another factor affecting the carbon content is the holding time required for the conditioning treatment. At carbon levels of about .02%, the conditioning treatment must be on the order of several hours. On the other hand, if the carbon is increased to even about 025%, the treatment time may be reduced to about one hour.
- the sulfur content of this steel should not exceed about .015%, and preferably should not exceed .010%, for the reason that this ingredient appears as an interstitial in the crystal lattice of the metal. This may generate dislocations. Thus, by minimizing the sulfur content, hence, reducing the number of dislocations in the lattice structure, there results an increase in the toughness of the metal.
- the nitrogen content it is preferable to maintain same below about .05%, and more preferably below about .01%, so as not to impair the toughness and resistance to impact. Optimum toughness will be obtained with nitrogen below about .003%. It is believed that with larger amounts of nitrogen in the presence of the aluminum of this steel, there is a tendency for the elements to form aluminum nitrides, which when dispersed throughout the steel may affect the properties thereof.
- Boron is desirable in the steel of this invention as it helps to secure good hot-rolling and other hot-working properties. For this reason, at least .0005 is used. However, the boron content should not exceed about .003% because boron like the sulfur discussed above, is an intestitial in the crystal lattice structure, and this causes an attending loss in toughness. It was further discovered that when working with steels having a U.T.S. greater than about 230 k.s.i., the boron in the range described has six times the effect of carbon on the final toughness of the heat treated steel. Accordingly, to achieve both the high strength'and good toughness it is important that the carbon content plus six times the boron content should not exceed .042.
- Phosphorus normally is present in the steel of this invention in relatively small amounts. While the lowest values are most desirable, the phosphorus content should not exceed .040%. As to the manganese and silicon contents, optimum mechanical properties are achieved with maximum contents of .1%.'
- the molybdenum content has been shown in this steel to be an optional element, it is preferred that the element be used to the extent of about 2%. Accordingly, the preferred figure for the molybdenum is a maximum of 6% with the most preferred range thereof being between about LSD-3.00%.
- Sample C Cr Ni M0 Al Cu N B C-I-GXB Cu+Al 1 Sample 6 contained 27% V, where V 2Cr.
- a semi-austenitic precipitation-hardenable stainless steel consisting essentially of, by weight percent, about 7.0-18.0% chromium, about 6.0-12.0% nickel, about .5- 2.5% aluminum, a maximum of 1.0% manganese, a maximum of 1.0% silicon, a maximum of .042% carbon, a
- a semi-austenitic precipitation-hardenable stainless steel consisting essentially of, by weight percent, about 10.0-15.0% chromium, about 7 .0-10.0% nickel, about .75-2.0 aluminum, a maximum of .75% manganese, a maximum of .75 silicon, a maximum of .042% carbon, a maximum of .040% phosphorus, a maximum of .015% sulfiur, a maximum of .05 nitrogen, a maximum of 6.0% molybdenum, about 1.0 -3.0% copper, about .0005- .0015 boron, with the balance essentially iron, the sum of the aluminum plus copper contents being at least 3.00%, and the carbon content plus six times the boron content not exceeding .042.
- a semi-austenitic precipitation-hardenable stainless steel consisting essentially of, by weight percent, about 13.50-15.00% chromium, about 7.25-8. nickel, about l.001.75% aluminum, a maximum of .75 manganese, a maximum of .75 silicon, a maximum of 039% carbon, a maximum of .020% phosphorus, a maximum of .010% sulfur, a maximum of .0l% nitrogen, about 1.50-3.00% molybdenum, about LSD-2.50% copper, about .0005- .0015% boron, and balance substantially iron with the sum of the aluminum plus copper contents being at least 3.00%, and the carbon content plus six times the boron content not exceeding about .039.
- a precipitation-hardened stainless steel havng a hardness of about R 40-53, an ultimate tensile strength of at least about 230 k.s.i., and a pre-cracked sheet charpy toughness of at least 1000 W/A (in.-lb./in.
- said steel consisting essentially of, by weight percent, about 10.0-15.0% chromium, about 7.0-10.0% nickel, about .752.0% aluminum, a maximum of .75 manganese, a maximum of .75 silicon, a maximum of .042% carbon, a maximum of .040% phosphorus, a maximum of .015% sulfur, a maximum of .05 nitrogen, a maximum of 6.0% molybdenum, about 1.0-3.0% copper, about .0005-.0015% boron, and the balance iron, with the sum of the aluminum plus copper contents being at least 3.00%, and the carbon content plus six times the boron content not exceeding .042.
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Heat Treatment Of Steel (AREA)
Abstract
Description
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US24029272A | 1972-03-31 | 1972-03-31 |
Publications (1)
Publication Number | Publication Date |
---|---|
US3795507A true US3795507A (en) | 1974-03-05 |
Family
ID=22905966
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US00240292A Expired - Lifetime US3795507A (en) | 1972-03-31 | 1972-03-31 | Semi-austenitic cr-ni-al-cu stainless steel |
Country Status (1)
Country | Link |
---|---|
US (1) | US3795507A (en) |
Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3910788A (en) * | 1973-04-21 | 1975-10-07 | Nisshin Steel Co Ltd | Austenitic stainless steel |
FR2339679A1 (en) * | 1976-02-02 | 1977-08-26 | Avesta Jernverks Ab | HIGH MOLYBDENE AUSTENITIC STAINLESS STEEL |
US4055448A (en) * | 1973-04-10 | 1977-10-25 | Daido Seiko Kabushiki Kaisha | Ferrite-austenite stainless steel |
US4125260A (en) * | 1976-05-17 | 1978-11-14 | True Temper Corporation | Tubular golf shaft of stainless steel |
US4141762A (en) * | 1976-05-15 | 1979-02-27 | Nippon Steel Corporation | Two-phase stainless steel |
US4218268A (en) * | 1977-06-30 | 1980-08-19 | Kubota Ltd. | High corrosion resistant and high strength medium Cr and low Ni stainless cast steel |
US4224061A (en) * | 1977-06-30 | 1980-09-23 | Kubota Ltd. | High corrosion resistant and high strength medium Cr and low Ni stainless cast steel |
US4902472A (en) * | 1985-07-19 | 1990-02-20 | Daido Tokushuko Kabushiki Kaisha | High strength stainless steel |
-
1972
- 1972-03-31 US US00240292A patent/US3795507A/en not_active Expired - Lifetime
Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4055448A (en) * | 1973-04-10 | 1977-10-25 | Daido Seiko Kabushiki Kaisha | Ferrite-austenite stainless steel |
US3910788A (en) * | 1973-04-21 | 1975-10-07 | Nisshin Steel Co Ltd | Austenitic stainless steel |
FR2339679A1 (en) * | 1976-02-02 | 1977-08-26 | Avesta Jernverks Ab | HIGH MOLYBDENE AUSTENITIC STAINLESS STEEL |
US4141762A (en) * | 1976-05-15 | 1979-02-27 | Nippon Steel Corporation | Two-phase stainless steel |
US4125260A (en) * | 1976-05-17 | 1978-11-14 | True Temper Corporation | Tubular golf shaft of stainless steel |
US4218268A (en) * | 1977-06-30 | 1980-08-19 | Kubota Ltd. | High corrosion resistant and high strength medium Cr and low Ni stainless cast steel |
US4224061A (en) * | 1977-06-30 | 1980-09-23 | Kubota Ltd. | High corrosion resistant and high strength medium Cr and low Ni stainless cast steel |
US4902472A (en) * | 1985-07-19 | 1990-02-20 | Daido Tokushuko Kabushiki Kaisha | High strength stainless steel |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
EP0440948B1 (en) | Chromium-nickel steel for surgical needles | |
US5876521A (en) | Ultra high strength, secondary hardening steels with superior toughness and weldability | |
US3726723A (en) | Hot-rolled low alloy steels | |
US3795507A (en) | Semi-austenitic cr-ni-al-cu stainless steel | |
US3303061A (en) | Bainitic iron alloys | |
EP0314649B1 (en) | Ferritic-martensitic stainless steel alloy with deformation-induced martensitic phase | |
US2903386A (en) | Heat-hardened stainless steel and method for cold treating same | |
JP3169978B2 (en) | Precipitation hardening high strength non-magnetic stainless steel | |
JPH10504354A (en) | High hardness martensitic stainless steel with excellent pitting resistance | |
US3318690A (en) | Age hardening manganese-containing maraging steel | |
US2505763A (en) | Stainless steel and method | |
US6080359A (en) | Maraging steel | |
US5147475A (en) | High strength stainless steel | |
US3832244A (en) | Stainless steel | |
JPS625986B2 (en) | ||
KR20200045907A (en) | Austenitic stainless steels excellent in fatigue life and manufacturing method thereof | |
US2482098A (en) | Hardenable iron alloy | |
US3658514A (en) | Martensitic steel | |
US4353755A (en) | Method of making high strength duplex stainless steels | |
US2505762A (en) | Stainless steel and method | |
US5951788A (en) | Superconducting high strength stainless steel magnetic component | |
US2967770A (en) | Transformable stainless steel | |
JPH10245656A (en) | Martensitic stainless steel excellent in cold forgeability | |
US3741822A (en) | High strength steel | |
US3083095A (en) | Alloy steel and method |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
AS | Assignment |
Owner name: ARMCO ADVANCED MATERIALS CORPORATION, STANDARD AVE Free format text: ASSIGNMENT OF ASSIGNORS INTEREST. , EFFECTIVE DEC. 31, 1987.;ASSIGNOR:ARMCO, INC.;REEL/FRAME:004850/0157 Effective date: 19871216 Owner name: ARMCO ADVANCED MATERIALS CORPORATION,PENNSYLVANIA Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:ARMCO, INC.;REEL/FRAME:004850/0157 Effective date: 19871216 |
|
AS | Assignment |
Owner name: ARMCO INC., A CORP OF OHIO, OHIO Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:ARMCO ADVANCED MATERIALS CORPORATION, A CORP OF DE;REEL/FRAME:005489/0132 Effective date: 19900430 |