Method for manufacturing thin strip continuously cast 700MPa-grade high strength weather-resistant steel

Patent metadata

Field	Value
Publication number	US-9987669-B2
Application number	US-201314372678-A
Country	US
Kind code	B2
Filing date	Feb 18, 2013
Priority date	Mar 14, 2012
Publication date	Jun 5, 2018
Grant date	Jun 5, 2018

Abstract

A method for manufacturing thin strip continuously cast 700 Mpa grade high strength weather-resistant steel, the method comprising the following steps: 1) casting a 1-5 mm thick cast strip in a double roller continuous casting machine, the cast strip comprising the following chemical compositions by weight percent: C 0.03-0.1%, Si≤0.4%, Mn 0.75-2.0%, P 0.07-0.22%, S≤0.01%, N≤0.012%, and Cu 0.25-0.8%, further comprising more than one of Nb, V, Ti and Mo: Nb 0.01-0.1%, V 0.01-0.1%, Ti 0.01-0.1%, and Mo 0.1-0.5%, and the balance being Fe and unavoidable impurities; 2) cooling the cast strip at a rate greater than 20° C./s; 3) hot rolling the cast strip under a temperature of 1050-1250° C. at a reduction rate of 20-50% and a deformation rate greater than 20 s−1; then conducting austenite online recrystallization, the thickness of the hot rolled strip being 0.5-3.0 mm; 4) cooling at a rate of 10-80° C./s; and 5) rolling up under a temperature of 500-650° C. The obtained steel strip microstructure mainly consists of uniformly distributed bainites and needle-shaped ferrites.

First claim

The invention claimed is:

1. A manufacturing method of a continuous strip cast weather-resistant steel having a high-strength of 700 MPa-grade, the method sequentially comprising the following steps:
1) casting a cast strip having a thickness of 1˜5 mm by using a twin-roller continuous casting mill, wherein the cast strip has a chemical composition by weight percentage as follows: C 0.03˜0.1%, Si≤0.4%, Mn 0.75˜2.0%, P 0.07˜0.22%, 0<S≤0.01%, 0<N≤0.012% and Cu 0.25˜0.8%, and at least one microalloy element selected from Nb, V, Ti, and Mo having a content of Nb 0.01˜0.1%, V 0.01˜0.1%, Ti 0.01˜0.1%) and Mo 0.1˜0.5%, and balance being Fe and inevitable impurities;
2) cooling the cast strip after the casting the cast strip, wherein the cooling rate is 23° C./sec. to 42° C./sec.;
3) online hot rolling the cast strip after cooling the cast strip under a hot rolling temperature of 1,050˜1,250° C., a reduction rate of 20˜50%, and a deformation rate of >20 s −1 , wherein the thickness of the steel strip after hot rolling is 0.5˜3.0 mm, and online austenite recrystallization occurs upon the hot rolling of the cast strip;
4) cooling the hot-rolled strip after online hot rolling the cast strip, wherein the cooling rate is 14° C./sec. to 79° C./sec.;
5) coiling the hot-rolled strip after cooling the hot-rolled strip, wherein the coiling temperature of the hot-rolled strip is controlled to be 500˜650° C.; and
wherein the final resulting steel strip has a microstructure substantially consisting of homogeneous bainite and acicular ferrite conferring a strength property and an elongation property to the steel strip.

2. The manufacturing method of claim 1 , wherein, in step 1), the content of each of Nb, V and Ti is 0.01˜0.05% by weight percentage.

3. The manufacturing method of claim 1 , wherein, in step 1), the content of Mo is 0.1˜0.25% by weight percentage.

4. The manufacturing method of claim 1 , wherein, in step 3), the hot rolling temperature is in the range of 1100˜1250° C.

5. The manufacturing method of claim 1 , wherein, in step 3), the hot rolling temperature is in the range of 1150˜1250° C.

6. The manufacturing method of claim 1 , wherein, in step 3), the reduction rate of hot rolling is in the range of 30-50%.

7. The manufacturing method of claim 1 , wherein, in step 3), the deformation rate of hot rolling is 28 s −1 to 76 s −1 .

8. The manufacturing method of claim 1 , wherein, in step 4), the cooling rate of the hot-rolled strip is in the range of 23° C./sec. to 52° C./sec.

9. The manufacturing method of claim 1 , wherein, in step 5), the coiling temperature is in the range of 500˜600° C.

10. The manufacturing method of claim 1 , wherein, the thickness of said steel strip is less than 3 mm.

11. The manufacturing method of claim 1 , wherein, the thickness of said steel strip is less than 2 mm.

12. The manufacturing method of claim 1 , wherein, the thickness of said steel strip is less than 1 mm.

13. The manufacturing method of claim 1 , wherein, said steel strip has a yield strength of 700 MPa or above, a tensile strength of 780 MPa or above, and an elongation of 18% or above.

Assignees

• Baoshan Iron & Steel

Inventors

• Fang Yuan
• Wang Xiufang
• Yu Yan
• Wu Jianchun
• Zhang Feng
• He Wei

Classifications

• C21D8/00 Primary

  Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment (hardening articles or materials formed by forging or rolling with no further heating beyond that required for the formation C21D1/02) · CPC title

• C22C38/16

  containing copper · CPC title

• C21D9/52

  for wires; for strips {; for rods of unlimited length} · CPC title

• B22D11/0622

  formed by two casting wheels · CPC title

• C21D2211/005

  Ferrite · CPC title