High-strength steel with yield strength of 800 mpa and production method therefor

Patent metadata

Field	Value
Publication number	US-2017349987-A1
Application number	US-201515536200-A
Country	US
Kind code	A1
Filing date	Dec 8, 2015
Priority date	Dec 19, 2014
Publication date	Dec 7, 2017
Grant date	—

Abstract

A high-strength steel having a yield strength at a level of 800 MPa and a method of manufacturing the same, with the components and amounts thereof by weight percentage being: C:0.06-0.14%, Si: 0.1-0.30%, Mn: 0.8-1.60%, Cr: 0.2-0.70%, Mo: 0.1-0.40%, Ni: 0-0.30%, Nb: 0.01-0.030%, Ti: 0.01-0.030%, V: 0.01-0.05%, B: 0.0005-0.0030%, Al: 0.02-0.06%, Ca: 0.001-0.004%, N: 0.002-0.005%, P≦0.02%, S≦0.01%, O≦0.008%, the balance of Fe and unavoidable impurities; wherein the above elements meet the following relationships: 0.40%<Ceq<0.50%, Ceq=C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15; 0.7%≦Mo+0.8Ni+0.4Cr+6V≦1.1%; 3.7≦Ti/N≦7.0; 1.0≦Ca/S≦3.0.

First claim

1 . A high-strength steel having a yield strength at a level of 800 MPa, consisting of the following components by weight percentage: C: 0.06-0.14%, Si: 0.10-0.30%, Mn: 0.80-1.60%, Cr: 0.20-0.70%, Mo: 0.10-0.40%, Ni: 0-0.30%, Nb: 0.010-0.030%, Ti: 0.010-0.030%, V: 0.010-0.050%, B: 0.0005-0.0030%, Al: 0.02-0.06%, Ca: 0.001-0.004%, N: 0.002-0.005%, P≦0.020%, S≦0.010%, O≦0.008%, and the balance of Fe and unavoidable impurities; wherein the above elements meet the following relationships: 0.40%<Ceq<0.50%, Ceq=C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15, 0.7%≦Mo+0.8Ni+0.4Cr+6V≦1.1%; 3.7≦Ti/N≦7.0; and 1.0≦Ca/S≦3.0.

2 . The high-strength steel having a yield strength at a level of 800 MPa according to claim 1 , wherein the high-strength steel has a microstructure of tempered martensite.

3 . The high-strength steel having a yield strength at a level of 800 MPa according to claim 1 , wherein the high-strength steel has a yield strength of 800-950 MPa, a tensile strength of 850-1000 MPa, an elongation >12%, and an impact energy at −40° C.>40 J.

4 . A method of manufacturing the high-strength steel having a yield strength at a level of 800 MPa according to claim 1 , comprising the following steps:
1) Smelting and casting smelting a composition as described in claim 1 in a converter or electrical furnace, refining, and casting to a cast blank; 2) Slab Heating heating the cast blank in a furnace at 1150-1270° C., wherein, when the temperature of the core of the cast blank arrives at the furnace temperature, the temperature is held, and the holding time is >1.5 h; 3) Rolling rolling the cast blank to a target thickness by single-stand reciprocating rolling or multi-stand hot continuous rolling, wherein a final rolling temperature is 820-920° C., and the final rolling temperature Tf meets: Ar 3 <Tf<Tnr, wherein Ar 3 is a temperature at which hypo-eutectoid steel austenite begins to convert to ferrite: Ar 3 =901−325C−92Mn−126Cr−67Ni−149Mo; Tnr is non-recrystallization critical temperature: Tnr=887+464C+(6445Nb−644 sqrt(Nb))+(732V−230 sqrt(V))+890Ti+363Al−357Si; a rolling reduction rate at a final rolling path is >15%; 4) Quenching heat treatment process conducting on-line quenching to (Ms−150) ° C. or lower after the rolling by using a laminar cooling system to control a cooling speed V>e (5.3−2.53c−0.16Si−0.82Mn−0.95Cr−1.87Mo−160B) ° C./s, so as to guarantee formation of full martensitic structure, wherein Ms is a temperature at which transformation of martensite begins, Ms=539−423C−30.4Mn−17.7Ni−12.1Cr−11.0Si−7.0Mo; 5) Annealing heat treatment process subjecting to annealing heat treatment at an annealing temperature of 400-550° C.; wherein when the temperature of the core of the steel plate arrives at the furnace temperature, the temperature is held, and the holding time is 20-180 min.

5 . The method of manufacturing the high-strength steel having a yield strength at a level of 800 MPa according to claim 4 , wherein the high-strength steel manufactured by the method has a microstructure of tempered martensite.

6 . The method of manufacturing the high-strength steel having a yield strength at a level of 800 MPa according to claim 4 , wherein the high-strength steel manufactured by the method has a yield strength of 800-950 MPa, a tensile strength of 850-1000 MPa, an elongation >12%, and an impact energy at −40° C.>40 J.

Assignees

• Baoshan Iron & Steel

Inventors

• Liu Gang
• Yang Ana
• Li Zigang
• Song Fengming

Classifications

• C21D8/0226

  Hot rolling · CPC title

• C21D2211/008

  Martensite · CPC title

• C21D7/13

  by hot working · CPC title

• C21D8/0263

  following hot rolling · CPC title

• C22C38/44

  with molybdenum or tungsten · CPC title