Super bainite steel and method for manufacturing it

Patent metadata

Field	Value
Publication number	US-2016304985-A1
Application number	US-201615190544-A
Country	US
Kind code	A1
Filing date	Jun 23, 2016
Priority date	Sep 9, 2010
Publication date	Oct 20, 2016
Grant date	—

Abstract

The invention relates to a super bainite steel consisting of the following elements in weight %: C: 0.4-1.1 Mn: 0.4-2.1 Si: 0.15-1.2 Al: 0.0-2.0 Cr: 0.0-1.4 Ni: 0.0-2.5 Mo: 0.0-0.6 V: 0.0-0.3 Co: 0.0-3.0 P: <0.025 S: <0.025 the balance being iron and unavoidable impurities. The invention also relates to a method for manufacturing such a super bainite steel.

First claim

We claim:

1 . A method for manufacturing a super bainite steel consisting of the following elements in weight %:
C: 0.4-1.1 Mn: 0.4-2.1 Si: 0.15-1.2 Al: 0.0-2.0 Cr: 0.0-1.4 Ni: 0.0-2.5 Mo: 0.0-0.6 V: 0.0-0.3 Co: 0.0-3.0 P: <0.025 S: <0.025 the balance being iron and unavoidable impurities, said method comprising the following steps: preparing molten steel having the required composition; continuously casting the molten steel into a slab; hot rolling the slab into strip; coiling the strip; austenising the strip at least once; heat treating the steel.

2 . Method according to claim 1 , wherein the super bainite steel strip is decoiled, cut into plates and leveled before heat treatment.

3 . Method according to claim 2 , wherein the plates are perforated in the hot rolled condition prior to heat treatment, the perforating preferably being performed by laser cutting or water cutting or drilling or mechanical punching.

4 . Method according to claim 1 , wherein the austenising is performed using austempering during a soak time of at least 30 minutes at a temperature of at least 900° C.

5 . Method according to claim 4 , wherein the austenising is performed in an endothermic atmosphere having a carbon potential of at least 0.4 carbon.

6 . Method according to claim 1 , wherein the heat treatment is performed by quenching in a salt bath at a temperature between 220 and 300° C.

7 . Method according to claim 6 , wherein the heat treatment is performed with a cooling rate of 2-20° C. per second, preferably at a cooling rate of 5-20° C. per second.

8 . Method according to claim 1 , wherein the steel is descaled prior to the heat treatment, preferably before any levelling of the plates.

9 . Method according to claim 5 wherein the austenising is performed in an endothermic atmosphere having a carbon potential of at least 0.8

10 . Method according to claim 6 wherein the heat treatment is performed by quenching in a salt bath at a temperature between 230 and 260° C.

11 . Method according to claim 7 , wherein the heat treatment is performed at a cooling rate of 5-20° C. per second.

Assignees

• Secr Defence

Inventors

• Clarke Richard
• Davies Paul
• Madill John
• Rose Andrew James
• Smith Andrew
• Thomas Alun

Classifications

• C21D8/02

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

• C22C38/02

  containing silicon · CPC title

• C21D8/0242

  Flattening; Dressing; Flexing · CPC title

• B24C1/006

  using material without particles or pellets for deburring, removal of extended surface areas or jet milling of local recessions, e.g. grooves · CPC title

• C21D8/0263

  following hot rolling · CPC title