公开(公告)号：US12054799B2

公开(公告)日：2024-08-06

申请号：US16064596

申请日：2016-12-20

Applicant: ArcelorMittal

Inventor： Maya Gospodinova ,  Véronique Hebert ,  Pavan Venkatasurya

IPC: C21D9/46 ,  B23K11/11 ,  B32B15/01 ,  C21D1/18 ,  C21D6/00 ,  C21D8/02 ,  C22C38/00 ,  C22C38/04 ,  C22C38/06 ,  C22C38/22 ,  C22C38/26 ,  C22C38/34 ,  C22C38/38 ,  C23C2/06 ,  C23C2/40

CPC classification number: C21D9/46 ,  B23K11/11 ,  B32B15/013 ,  C21D1/18 ,  C21D6/002 ,  C21D6/005 ,  C21D6/008 ,  C21D8/0205 ,  C21D8/0226 ,  C21D8/0236 ,  C21D8/0247 ,  C21D8/0263 ,  C22C38/00 ,  C22C38/04 ,  C22C38/06 ,  C22C38/22 ,  C22C38/26 ,  C22C38/34 ,  C22C38/38 ,  C23C2/06 ,  C23C2/40 ,  C21D2211/001 ,  C21D2211/002 ,  C21D2211/005 ,  C21D2211/008

Abstract: A method for producing a steel sheet is provided. The method includes providing a cold-rolled steel sheet including in weight %: 0.15%≤C≤0.23%, 1.4%≤Mn≤2.6%, 0.6%≤Si≤1.5%, 0.02%≤Al≤1.0%, with 1.0%≤Si+Al≤2.0%, 0≤Nb≤0.035%, 0≤Mo≤0.3%, 0≤Cr≤0.3%, and a remainder of Fe and unavoidable impurities, annealing the steel sheet at an annealing temperature between Ac1 and Ac3 to obtaining at least 40% austenite and at least 40% intercritical ferrite, quenching the sheet from at least 600° C. at a cooling rate of at least 20° C./s to a quenching temperature between 180° C. and 260° C., heating the sheet to a partitioning temperature between 375° C. and 470° C. and maintaining the sheet at this partitioning temperature for a partitioning time Pt between 25 s and 440 s, then cooling the sheet to room temperature. A steel sheet is also provided.

公开(公告)号：US11827948B2

公开(公告)日：2023-11-28

申请号：US16063740

申请日：2016-12-21

Applicant: ArcelorMittal

Inventor： Maya Gospodinova ,  Véronique Hebert

IPC: C21D8/02 ,  B23K11/11 ,  B23K35/30 ,  C22C38/04 ,  C22C38/22 ,  C22C38/26 ,  C22C38/34 ,  C23C2/06 ,  C23C2/28 ,  C23C2/40 ,  B23K103/04

CPC classification number: C21D8/0236 ,  B23K11/11 ,  B23K35/3073 ,  C21D8/0205 ,  C21D8/0226 ,  C21D8/0263 ,  C22C38/04 ,  C22C38/22 ,  C22C38/26 ,  C22C38/34 ,  C23C2/06 ,  C23C2/28 ,  C23C2/40 ,  B23K2103/04 ,  C21D2211/001 ,  C21D2211/002 ,  C21D2211/005 ,  C21D2211/008

Abstract: A method for producing a coated steel sheet having a tensile strength TS of at least 1100 MPa, a total elongation TE according to ISO standard 6892-1 of at least 12%, the product TSxTE of the tensile strength by the total elongation being at least 14200 MPa %, and a hole expansion ratio HER according to ISO standard 16630:2009 of at least 25%, the method including the following successive steps:



providing a cold-rolled steel sheet, the chemical composition of the steel containing in weight %: 0.15%≤C≤0.23%, 2.0%≤Mn≤2.7%, with C+Mn/10≥0.420%, 0≤Cr≤0.40%, with Mn+Cr≥2.25%, 0.2%≤Si≤1.6%, 0.02%≤Al≤1.2%, with 1.0%≤Si+Al≤2.2%, 0≤Nb≤0.035%, 0≤Mo≤0.1%, the remainder being Fe and unavoidable impurities,
annealing the steel sheet at an annealing temperature TA so as to obtain a structure comprising at least 65% of austenite and at most 35% of intercritical ferrite,
quenching the sheet from a temperature of at least 600° C. at a cooling rate comprised between 20° C./s and 50° C./s down to a quenching temperature QT between 200° C. and 270° C.,
heating the sheet up to a partitioning temperature PT comprised between 400° C. and 480° C. and maintaining the sheet at this partitioning temperature PT for a partitioning time Pt comprised between 50 s and 250 s,
hot-dip coating the sheet at a temperature less than 515° C.,
cooling the coated sheet down to the room temperature,

the steel sheet having a microstructure consisting of, in surface fraction: between 3% and 15% of retained austenite, at least 30% of tempered martensite, at most 5% of fresh martensite, at most 35% of bainite, the sum of the surface fractions of tempered martensite, fresh martensite and bainite being comprised between 55% and 92%, and between 5% and 35% of ferrite.