High-strength high-tenacity steel plate with tensile strength of 800 MPa and production method therefor

Patent metadata

Field	Value
Publication number	US-11319607-B2
Application number	US-201515536743-A
Country	US
Kind code	B2
Filing date	Nov 24, 2015
Priority date	Dec 19, 2014
Publication date	May 3, 2022
Grant date	May 3, 2022

Abstract

Disclosed are a high-strength and high-toughness steel plate with an 800 MPa grade tensile strength and a method for manufacturing the same, the chemical composition of the steel plate in weight percentage being: C: 0.15-0.25%, Si: 1.0-2.0%, Mn: 1.2-2.0%, P≤0.015%, S≤0.005%, Al: 0.5-1.0%, N: ≤0.006%, Nb: 0.02-0.06%, O≤0.003%, and the balance being Fe and other inevitable impurities, and 1.5%≤Si+Al≤2.5%. By adopting an isothermal heat treatment a high-strength and high-toughness steel plate with an 800 MPa grade tensile strength, which has a microstructure mainly including bainite ferrite and residual austenite, is obtained impact energy.

First claim

The invention claimed is:

1. A high-strength and high-toughness hot-rolled steel plate with a tensile strength of 800-900 MPa, the chemical composition of the steel plate in weight percentage being: C: 0.15-0.25%, Si: 1.0-2.0%, Mn: 1.2-2.0%, P≤0.015%, S≤0.005%, Al: 0.53-1.0%, N≤0.006%, Nb: 0.02-0.06%, O≤0.003%, and the balance being Fe and other inevitable impurities, and 1.53%≤Si+Al≤2.5%, and
wherein the steel plate has a microstructure consisting of bainitic ferrite and 13.0% or more of residual austenite, wherein the steel plate has a yield strength of ≥390 MPa, an elongation of >20%, and an impact energy at −20° C. of >100 J, and wherein the steel plate has a thickness of 3-12 mm.

2. The high-strength and high-toughness steel plate according to claim 1 , wherein the content of Si, in weight percentage, is in a range of 1.3-1.7%.

3. The high-strength and high-toughness steel plate according to claim 1 , wherein the content of Mn, in weight percentage, is in a range of 1.4-1.8%.

4. The high-strength and high-toughness steel plate according to claim 1 , wherein the content of N, in weight percentage, is ≤0.004%.

5. The high-strength and high-toughness steel plate according to claim 1 , wherein the content of Nb, in weight percentage, is in a range of 0.03-0.05%.

6. A method for manufacturing the high-strength and high-toughness steel plate of claim 1 , characterized by comprising the following steps:
1) smelting, secondary refining, and casting
smelting by using a converter furnace or an electric furnace, secondary refining by using a vacuum furnace, and casting to form a cast slab or cast ingot, with the following chemical components and amounts thereof in weight percentage: C: 0.15-0.25%, Si: 1.0-2.0%, Mn: 1.2-2.0%, P: ≤0.015%, S: ≤0.005%, Al: 0.53-1.0%, N: ≤0.006%, Nb: 0.02-0.06%, O: ≤0.03%, and the balance of Fe and other inevitable impurities, and 1.53%≤Si+Al≤2.5%;
2) heating, hot rolling, coiling, and re-uncoiling the cast slab or cast ingot obtained in step 1) and cutting to plates to obtain a substrate; and
3) heat treatment
heating the substrate obtained in step 2) to Ac3+(30-50)° C., Ac3=955-350C-25Mn+5 I Si+106Nb+68Al, with the various element symbols all referring to the contents in weight percentage in the formula; holding for 10-30 min after the temperature of the core of the substrate arrives at a temperature of Ac3+(30-50)° C., then rapidly cooling to 350-500° C. at a cooling rate >50° C./s, and then subjecting to isothermal transformation for 200-500s, quenching at a cooling rate of greater than 30° C./s to room temperature to obtain a high-strength and high-toughness steel plate with a tensile strength of 800-900 MPa.

7. The method for manufacturing the high-strength and high-toughness steel plate according to claim 6 , characterized in that the microstructure of the steel plate obtained by the manufacturing method consists of bainitic ferrite and 13.0% or more residual austenite.

Assignees

• Baoshan Iron & Steel

Inventors

• Wang Huanrong
• Yang Ana
• Wang Wei

Classifications

• Y02P10/20

  Recycling · CPC title

• C21D8/02 Primary

  during manufacturing of plates or strips (C21D8/12 takes precedence) · CPC title

• C21D2211/001

  Austenite · CPC title

• C21D9/46

  for sheet metals · CPC title

• C22C38/002

  containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60 · CPC title