US3645721A - Heat-treatable, high-strength, high-toughness, low-carbon, ni-mo alloy steel - Google Patents
Heat-treatable, high-strength, high-toughness, low-carbon, ni-mo alloy steel Download PDFInfo
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- US3645721A US3645721A US700440A US3645721DA US3645721A US 3645721 A US3645721 A US 3645721A US 700440 A US700440 A US 700440A US 3645721D A US3645721D A US 3645721DA US 3645721 A US3645721 A US 3645721A
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- 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
- C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
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- An object of the invention is to provide a low-carbon alloy steel containing nickel and molybdenum as essential constituents and in proportions such that a controlled proportion of austenite is retained in the steel after quenching, thus to impart increased toughness to the steel along with high strength.
- a further object of the invention is to provide an alloy steel having a composition which displays an optimum combination of high toughness and strength when heat treated as aforesaid.
- one of the properties which is required in some of the foregoing applications includes the ability to retain strength and toughness up to about l,000 F.
- the maraging steels have found commercial acceptance because of their excellent mechanical properties developed without necessity for quenching. These steels, however, are expensive because of their relatively high-alloy content.
- the present invention is concerned with steels of relatively lowalloy content and of improved composition, in the quenched and tempered category.
- nickel and molybdenum are essential constituents, in amounts of about 8-12 percent nickel and 0.50 to 1.50 percent molybdenum,
- lron Balance substantially Other constituents have been, or can be, used in the steel of the present invention in very minor amounts and may replace all or a portion of the manganese and silicon.
- additional ingredients may comprise chromium, cobalt and certain other deoxidizing elements such as aluminum, titanium or zirconium.
- composition range there is a preferred range for the elements which produce a steel having excellent combinations of toughness and strength.
- the preferred range is as follows: about 0.18 to 0.22 percent of carbon, about 9.8 to 10.2 percent nickel and about 1.10 to 1.20 percent molybdenum, and 0.01 to 0.15 percent each of Mn and Si.
- the steel of the present invention is in general, subjected to normalizing at a temperature within the range of about 1,625 to 1,650 F. for a period of about 1 hour. Thereafter it is allowed to air-cool to room temperature. The steel may then be austenitized at a temperature above 1,500 F. and thereafter oil-quenched with sufficient rapidity that substantially all of the austenite is converted to martensite. Some austenite, however, in the amount of about 2-5 percent of the quenched microstructure is retained in the steel after quenching to room temperature, and for purposes as hereinafter explained.
- the quenched steel may then be tempered over a wide range of temperature which may typically be between about 400 to l,000 F. for a time of about 4 hours. Additional heat treatments may be utilized either prior or subsequent to the tempering, depending on particular desired characteristics of the steel. For instance, low-temperature treatment such as refrigeration at about 1 20 F., may be used, followed by tempering as above.
- a typical steel made in accordance with the present invention and which as heat treated displays excellent high-toughness and strength properties contains about 0.20 percent carbon, 0.11 percent manganese, 0.10 percent silicon, 9.9 percent nickel and 1.15 percent molybdenum.
- the steel is normalized for 1 hour at a temperature of l,625 F., air cooled to room temperature, austenitized for 1 hour at 1,525 F., oil quenched and then tempered for 4 hours at l,000 F.
- the steel has a 0.2 percent ofiset yield strength of 172 k.s.i.
- a low-alloy, lowcarbon steel has been developed having relatively few alloying elements, and yet which achieves an optimum combination of strength and toughness.
- a feature of the invention is the development of a low-carbon steel alloy wherein some of the.
- steel produced in accordance with the present invention is capable of displaying combined high-strength and toughness characteristics without the addition of cobalt, which addition is undesirable in applications of such a steel for atomic power reactors.
- the temperature at which the formation of martensite commences (M,) is lowered, and thereby the transformation of austenite to martensite is controlled on cooling to assure the retention of a selected amount.
- M the temperature at which the formation of martensite commences
- the quenched alloy exhibits favorable characteristics of ductility as well as the high-tensile strensthglgrmally aa ie s wit ma nefi twgee
- the steel may be further toughened by subsequent tempering operations.
- the tempering cycles may include multiple tempering steps.
- the steel may be normalized at l,625 F. for 1 hour followed by air-cooling to room temperature, then austenitized at l,525 F. for 1 hour. After austenitizing, the steel is oil quenched, again to room temperature, followed by subsequent tempering, preferably at about 1,000 E, although acceptable results may be obtained by tempering at temperatures as low as about 400 F. Tempering durations are generally up to about 4 hours.
- FIG. 1 is a graphical chart showing the relationship between room temperature yield strength and Charpy V-notch (CVN) impact energy values for steels of the compositions shown, as austenitized, quenched and thence tempered at l,0O0 F.
- CVN Charpy V-notch
- FIG. 2 is a similar graphical chart in which the steels have been tempered ata temperature of 400 F.
- V568, V569 and V576 are steels according to the present invention while the remaining steels are not, including extraneous elements such as Co, Cr, etc., and/or excess Mn.
- B Norm. 1,6500), AU, Aust. 1,5500), 0Q, DT1.000(2 2)
- C Norm.1,650(1), AC.
- D Norm. 1,6250), AC, Aust. 1,6250), 0Q, '1 400(4).
- the test results further show that optimum strength and toughness is found where the alloy composition has the least amount of extraneous alloying elements.
- the test data thus shows that elimination of certain alloying elements, such as cobalt, chromium, vanadium and aluminum increases the austenite stability and enhances the optimum combination of strength and toughness in the steel alloy.
- the effect of such additional alloying elements tended to decrease either the toughness or the strength of the steel alloy.
- the effect of increasing the amount of manganese from 0.10 percent to 1.1 percent raised the overall yield strength of the alloy by only 1,000 p.s.i. (1 k.s.i.) but caused the toughness to decrease by some 19 ft.-lbs.
- the increase of carbon content caused a similar decrease in the toughness but a relatively small increase in the yield strength. This is illustrated by a comparison of heat V576 having a carbon content of 0.19 percent with heat V524 having a carbon content of 0.24 percent and a higher manganese percentage. Although, in this comparison, the higher carbon heat V524 caused an increase in yield strength of 7,000 p.s.i., it was accompanied by a decrease in the impact toughness of 23 ft.- lbs.
- the subsequent heat treatment of the steel determines its eventual characteristics and, in particular, the temperature at which tempering is carried out is an important factor in the final values.
- An alloy steel consisting of about: 0.15 to 0.25 percent carbon, 8 to 12 percent nickel, 0.5 to 1.5 percent molybdenum, up to 1 percent manganese, up to 1 percent silicon, up to 0.25 percent vanadium, and the balance all iron, characterized as normalized at about 1,625 to 1,650 F., thence austenitized above 1,500 F., oil quenched and tempered at about 4001,000 F., by a yield strength of at least 170,000 p.s.i., a Charpy V-notch impact strength of at least 60 ft.-lbs. at 70 F. and a substantially martensitic microstructure.
- a heat-treated alloy steel according to claim 1 having a microstructure consisting substantially of martensite and about 2-5 percent austenite in the quenched condition.
- a heat-treated alloy steel according to claim 1 having a preponderantly martensitic microstructure having a room temperature yield strength of at least k.s.i. and a Charpy V-notch impact strength of at least 60 ft.-lbs. at 70 F.
- An alloy steel according to claim 1 containing about: 0.18 to 0.22 percent carbon, 9.8 to 10.2 percent nickel, 1.1 to 1.2 percent molybdenum, 0.01 to 0.15 percent manganese, 0.01 to 0.15 percent silicon.
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- Heat Treatment Of Steel (AREA)
Abstract
Description
Claims (3)
- 2. A heat-treated alloy steel according to claim 1 having a microstructure consisting substantially of martensite and about 2-5 percent austenite in the quenched condition.
- 3. A heat-treated alloy steel according to claim 1 having a preponderantly martensitic microstructure having a room temperature yield strength of at least 170 k.s.i. and a Charpy V-notch impact strength of at least 60 ft.-lbs. at 70* F.
- 4. An alloy steel according to claim 1 containing about: 0.18 to 0.22 percent carbon, 9.8 to 10.2 percent nickel, 1.1 to 1.2 percent molybdenum, 0.01 to 0.15 percent manganese, 0.01 to 0.15 percent silicon.
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US70044068A | 1968-01-25 | 1968-01-25 |
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US3645721A true US3645721A (en) | 1972-02-29 |
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US700440A Expired - Lifetime US3645721A (en) | 1968-01-25 | 1968-01-25 | Heat-treatable, high-strength, high-toughness, low-carbon, ni-mo alloy steel |
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Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3969158A (en) * | 1972-08-10 | 1976-07-13 | Youngstown Sheet And Tube Company | Process for treating 9% nickel steel |
US4366859A (en) * | 1975-04-02 | 1983-01-04 | Keyes John M | Refractory heat exchange tube |
WO2001081638A1 (en) * | 2000-04-26 | 2001-11-01 | Lockheed Martin Corporation | HEAT TREATMENT FOR 9Ni-4Co-0.03C TYPE STEELS |
EP1594997A2 (en) * | 2003-01-24 | 2005-11-16 | Ellwood National Forge Company | Eglin steel - a low alloy high strength composition |
Citations (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2244064A (en) * | 1937-06-10 | 1941-06-03 | Babcock & Wilcox Co | Welded pressure vessel and method |
US2337049A (en) * | 1942-01-06 | 1943-12-21 | Pittsburgh Des Moines Company | Welded steel structure |
US2451469A (en) * | 1946-08-02 | 1948-10-19 | Int Nickel Co | Steels and structural embodiments thereof for use at low temperatures |
US2992148A (en) * | 1959-04-23 | 1961-07-11 | Int Nickel Co | Alloy steels |
GB1079036A (en) * | 1963-10-23 | 1967-08-09 | Donald Hardwick | Improvements in or relating to alloy steels |
US3366471A (en) * | 1963-11-12 | 1968-01-30 | Republic Steel Corp | High strength alloy steel compositions and process of producing high strength steel including hot-cold working |
US3444011A (en) * | 1963-11-18 | 1969-05-13 | Yawata Seitetsu Kk | Low-temperature tough steel |
US3496034A (en) * | 1966-02-21 | 1970-02-17 | United States Steel Corp | Steel resistant to embrittlement by neutron radiation |
-
1968
- 1968-01-25 US US700440A patent/US3645721A/en not_active Expired - Lifetime
Patent Citations (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2244064A (en) * | 1937-06-10 | 1941-06-03 | Babcock & Wilcox Co | Welded pressure vessel and method |
US2337049A (en) * | 1942-01-06 | 1943-12-21 | Pittsburgh Des Moines Company | Welded steel structure |
US2451469A (en) * | 1946-08-02 | 1948-10-19 | Int Nickel Co | Steels and structural embodiments thereof for use at low temperatures |
US2992148A (en) * | 1959-04-23 | 1961-07-11 | Int Nickel Co | Alloy steels |
GB1079036A (en) * | 1963-10-23 | 1967-08-09 | Donald Hardwick | Improvements in or relating to alloy steels |
US3366471A (en) * | 1963-11-12 | 1968-01-30 | Republic Steel Corp | High strength alloy steel compositions and process of producing high strength steel including hot-cold working |
US3444011A (en) * | 1963-11-18 | 1969-05-13 | Yawata Seitetsu Kk | Low-temperature tough steel |
US3496034A (en) * | 1966-02-21 | 1970-02-17 | United States Steel Corp | Steel resistant to embrittlement by neutron radiation |
Non-Patent Citations (1)
Title |
---|
Brophy, G. R., and A. J. Miller, The Metallography and Heat Treatment of 8 to 10% Nickel Steel, In Trans. of American Society for Metals, Vol. 41, 1949, pp. 1185 1203. * |
Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3969158A (en) * | 1972-08-10 | 1976-07-13 | Youngstown Sheet And Tube Company | Process for treating 9% nickel steel |
US4366859A (en) * | 1975-04-02 | 1983-01-04 | Keyes John M | Refractory heat exchange tube |
WO2001081638A1 (en) * | 2000-04-26 | 2001-11-01 | Lockheed Martin Corporation | HEAT TREATMENT FOR 9Ni-4Co-0.03C TYPE STEELS |
US6402863B1 (en) * | 2000-04-26 | 2002-06-11 | Lockheed Martin Corporation | Heat treatment for 9Ni-4Co-0.30C type steels |
GB2377226A (en) * | 2000-04-26 | 2003-01-08 | Lockheed Corp | Heat treatment for 9Ni-4Co-0.03C type steels |
GB2377226B (en) * | 2000-04-26 | 2003-11-05 | Lockheed Corp | Heat treatment for 9Ni-4Co-0.03C type steels |
EP1594997A2 (en) * | 2003-01-24 | 2005-11-16 | Ellwood National Forge Company | Eglin steel - a low alloy high strength composition |
EP1594997A4 (en) * | 2003-01-24 | 2006-11-02 | Ellwood Nat Forge Company | Eglin steel - a low alloy high strength composition |
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AS | Assignment |
Owner name: LTV STEEL COMPANY, INC., Free format text: MERGER AND CHANGE OF NAME EFFECTIVE DECEMBER 19, 1984, (NEW JERSEY);ASSIGNORS:JONES & LAUGHLIN STEEL, INCORPORATED, A DE. CORP. (INTO);REPUBLIC STEEL CORPORATION, A NJ CORP. (CHANGEDTO);REEL/FRAME:004736/0443 Effective date: 19850612 |
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Owner name: FIRST NATIONAL BANK OF BOSTON, THE, MASSACHUSETTS Free format text: SECURITY INTEREST;ASSIGNOR:REPUBLIC ENGINEERED STEELS, INC.;REEL/FRAME:005203/0955 Effective date: 19891128 |
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Owner name: REPUBLIC ENGINEERED STEELS, INC. Free format text: CHANGE OF NAME;ASSIGNOR:BAR ACQUISITION CO., A CORP. OF DELAWARE;REEL/FRAME:005741/0514 Effective date: 19890627 |
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Owner name: BANKBOSTON, N.A., AS AGENT, MASSACHUSETTS Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:REPUBLIC ENGINEERED STEELS, INC.;REEL/FRAME:010188/0230 Effective date: 19990813 |