Title:
METHOD FOR PRODUCING A HIGH STRENGTH STEEL SHEET HAVING IMPROVED STRENGTH AND FORMABILITY AND OBTAINED SHEET
Document Type and Number:
WIPO Patent Application WO/2016/001893
Kind Code:
A3
Abstract:
A method for producing a high strength steel sheet having a yield strength YS > 850 MPa, a tensile strength TS >1180 MPa, a total elongation > 13 % and a hole expansion ratio HER > 30%, by heat treating a steel sheet wherein the chemical composition of the steel contains: 0.13% ≤ C ≤ 0.22%, 1.2% ≤ Si ≤ 1.8%, 1.8% ≤ Mn ≤ 2.2%, 0.10% ≤ Mo ≤ 0.20%, Nb ≤ 0.05 %, Ti < 0.05 %, Al ≤ 0.5%, the remainder being Fe and unavoidable impurities. The sheet is annealed at an annealing temperature TA > 865°C and < 1000°C for a time of more than 30 s, then quenched by cooling it to a quenching temperature QT between 275°C and 375°C, at a cooling speed > 30°C/s in order to have, just after quenching, a structure consisting of austenite and at least 50% of martensite, the austenite content being such that the final structure can contain between 3% and 15% of residual austenite and between 85 % and 97% of the sum of martensite and bainite without ferrite, then heated to a partitioning temperature PT between 370°C and 470°C and maintained at this temperature for a time Pt between 50 s and 150 s, then cooled to the room temperature
Inventors:
MOHANTY RASHMI RANJAN (US)
JUN HYUN JO (US)
FAN DONGWEI (US)
VENKATASURYA PAVAN K C (US)
JUN HYUN JO (US)
FAN DONGWEI (US)
VENKATASURYA PAVAN K C (US)
Application Number:
PCT/IB2015/055037
Publication Date:
March 17, 2016
Filing Date:
July 03, 2015
Export Citation:
Assignee:
ARCELORMITTAL (LU)
International Classes:
C21D8/02; C21D1/18; C21D9/46; C21D9/48; C22C38/02; C22C38/04; C22C38/12
Domestic Patent References:
| WO2004022794A1 | 2004-03-18 | |||
| WO2014020640A1 | 2014-02-06 |
Foreign References:
| EP2325346A1 | 2011-05-25 | |||
| JP2012240095A | 2012-12-10 | |||
| JP2006083403A | 2006-03-30 | |||
| EP2524970A1 | 2012-11-21 | |||
| JP2012021225A | 2012-02-02 |
Other References:
"PRICM", 16 August 2013, JOHN WILEY & SONS, INC., Hoboken, NJ, USA, ISBN: 978-0-47-094309-0, article NING ZHONG ET AL: "Microstructual Evolution of a Medium Carbon Advanced High Strength Steel Heat-Treated by Quenching-Partitioning Process", pages: 885 - 889, XP055166044, DOI: 10.1002/9781118792148.ch109
DE MOOR E ET AL: "Quench and Partitioning response of a Mo-alloyed CMnSi steel", NEW DEVELOPMENTS ON METALLURGY AND APPLICATIONS OF HIGH STRENGTH STEELS : BUENOS AIRES 2008 ; INTERNATIONAL CONFERENCE, MAY 26 - 28, HILTON HOTEL, BUENOS AIRES, ARGENTINA,, vol. 2, 26 May 2008 (2008-05-26), pages 721 - 730, XP009182284, ISBN: 978-0-87339-729-2
DE MOOR E ET AL: "Quench and Partitioning response of a Mo-alloyed CMnSi steel", NEW DEVELOPMENTS ON METALLURGY AND APPLICATIONS OF HIGH STRENGTH STEELS : BUENOS AIRES 2008 ; INTERNATIONAL CONFERENCE, MAY 26 - 28, HILTON HOTEL, BUENOS AIRES, ARGENTINA,, vol. 2, 26 May 2008 (2008-05-26), pages 721 - 730, XP009182284, ISBN: 978-0-87339-729-2
Attorney, Agent or Firm:
DOMENEGO, Bertrand et al. (2 place d'Estienne d'Orves, Paris, FR)
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