公开(公告)号：US11713502B2

公开(公告)日：2023-08-01

申请号：US16609408

申请日：2018-05-07

Applicant: ArcelorMittal

Inventor： Pavan C. Venkatasurya ,  Anirban Chakraborty ,  Hassan Ghassemi-Armaki

IPC: C23C2/06 ,  C23C2/40 ,  C21D8/02 ,  C21D9/46 ,  B23K11/11 ,  B23K11/16 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/12

CPC classification number: C23C2/06 ,  B23K11/11 ,  B23K11/166 ,  C21D8/0205 ,  C21D8/0226 ,  C21D8/0236 ,  C21D8/0273 ,  C21D9/46 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/12 ,  C23C2/40 ,  C21D2211/001 ,  C21D2211/002 ,  C21D2211/005 ,  C21D2211/008

Abstract: A method for producing a high-strength steel sheet having high ductility, formability and weldability includes providing a cold-rolled sheet, with a composition containing: 0.15% ≤C≤0.23%, 1.4% ≤Mn≤2.6%, 0.6% ≤Si≤1.3%, with C+Si/10≤0.30%, 0.4% ≤Al≤1.0%, with Al≥6(C+Mn/10)−2.5%, 0.010% ≤Nb≤0.035%, 0.1% ≤Mo≤0.5%, annealing the sheet at 860° C.-900° C. to obtain a structure consisting of at least 90% austenite and at least 2% intercritical ferrite, quenching to a temperature between Ms-10° C. and Ms-60° C. at a rate Vc higher than 30° C./s, heating to a temperature PT between 410° C. and 470° C. for 60 s to 130 s, hot-dip coating the sheet, and cooling to room temperature. The microstructure includes 45% to 68% of martensite, consisting of 85% to 95% partitioned martensite having a C content of at most 0.45%, and fresh martensite; 10% to 15% retained austenite; 2% to 10% intercritical ferrite; 20% to 30% lower bainite.