High-toughness hot-rolling high-strength steel with yield strength of 800 MPa, and preparation method thereof

Patent metadata

Field	Value
Publication number	US-10378073-B2
Application number	US-201515514510-A
Country	US
Kind code	B2
Filing date	Jan 15, 2015
Priority date	Sep 26, 2014
Publication date	Aug 13, 2019
Grant date	Aug 13, 2019

Abstract

A high-toughness hot-rolled high-strength steel with a yield strength of Grade 800 MPa with its chemical components, in weight percentages, being C 0.02-0.05%, Si≤0.5%, Mn 1.5-2.5%, P≤0.015%, S≤0.005%, Al 0.02-0.10%, N≤0.006%, Nb 0.01-0.05%, Ti 0.01-0.03%, 0.03%≤Nb+Ti≤0.06%, Cr 0.1%-0.5%, Mo 0.1-0.5%, B 0.0005-0.0025%, and the balance of Fe and unavoidable impurities, and a preparation method thereof. The present invention acquires, via direct quenching, an ultra-low carbon martensite structure with a yield strength of 800 Mpa and an impact energy of more than 100J under a temperature of −80° C.

First claim

What is claimed is:

1. A high-toughness hot-rolled high-strength steel with a yield strength of Grade 800 MPa, consisting of, in weight percentages: C 0.02-0.05%, Si≤0.5%, Mn 1.5-2.5%), P≤0.015%), S≤0.005%, Al 0.02-0.10%, N≤0.006%), Nb 0.01-0.05%), Ti 0.01-0.03%, 0.03%≤Nb+Ti≤0.06%, Cr 0.1%-0.5%, Mo 0.1-0.5%, B 0.0005-0.0025%, and the balance of Fe and unavailable impurities.

2. The high-toughness hot-rolled high-strength steel with a yield strength of Grade 800 MPa of claim 1 , wherein the hot-rolled high-strength steel has a yield strength ≥800 MPa, a tensile strength ≥900 MPa, an elongation ≥13%, and an impact energy at −80° C. of 100 J or higher.

3. The high-toughness hot-rolled high-strength steel with a yield strength of Grade 800 MPa of claim 1 , wherein the hot-rolled high-strength steel has a microstructure of lath martensite.

4. A method of manufacturing the high-toughness hot-rolled high-strength steel with a yield strength of Grade 800 MPa, comprising the following steps:
1) Smelting and casting
A composition of claim 1 is smelted in a converter or electrical furnace, subjected to secondary refining in a vacuum furnace, and cast to a cast blank or ingot;

2) Heating
The cast blank or ingot is heated, wherein the heating temperature is 1100-1200° C., and the hold time is 1-2 hours;

3) Hot rolling
The initial rolling temperature is 1000-1100° C.; multi-pass large reduction rolling is conducted at a temperature of 950° C. or higher with an accumulated deformation rate ≥50%; subsequently, an intermediate blank is held till 900-950° C.; and then, the last 3-5 paths of rolling are conducted with an accumulated deformation rate ≥70%;

4) On-line quenching process
Rapid on-line quenching is conducted at a cooling rate ≥5° C./s from a temperature that is 800-900° C. above the temperature at which ferrite begins to precipitate to a temperature below Ms or room temperature to obtain fine ultralow-carbon lath martensite.

5. The method of manufacturing the high-toughness hot-rolled high-strength steel with a yield strength of Grade 800 MPa according to claim 4 , wherein the hot-rolled high-strength steel has a yield strength ≥800 MPa, a tensile strength ≥900 MPa, an elongation ≥13%, and an impact energy at −80° C. of 100 J or higher.

6. The method of manufacturing the high-toughness hot-rolled high-strength steel with a yield strength of Grade 800 MPa according to claim 4 , wherein the hot-rolled high-strength steel has a microstructure of lath martensite.

7. The method of manufacturing the high-toughness hot-rolled high-strength steel with a yield strength of Grade 800 MPa according to claim 5 , wherein the hot-rolled high-strength steel has a microstructure of lath martensite.

8. The high-toughness hot-rolled high-strength steel with a yield strength of Grade 800 MPa of claim 2 , wherein the hot-rolled high-strength steel has a microstructure of lath martensite.

9. The high-toughness hot-rolled high-strength steel with a yield strength of Grade 800 MPa of claim 1 , wherein the thickness of the steel is in the range of 3-12 mm.

10. The method of manufacturing the high-toughness hot-rolled high-strength steel with a yield strength of Grade 800 MPa according to claim 4 , wherein the thickness of the steel is in the range of 3-12 mm.

Assignees

• Baoshan Iron & Steel

Inventors

• Wang Huanrong
• Yang A'Na
• Wang Wei

Classifications

• C22C38/38

  with more than 1.5% by weight of manganese · CPC title

• C22C38/02

  containing silicon · CPC title

• C21D8/0226

  Hot rolling · CPC title

• C22C38/002

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

• C21D8/0263 Primary

  following hot rolling · CPC title