公开(公告)号：US20190003008A1

公开(公告)日：2019-01-03

申请号：US16064596

申请日：2016-12-20

Applicant: ARCELORMITTAL

Inventor： Maya GOSPODINOVA ,  Véronique HEBERT ,  Pavan VENKATASURYA

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

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：US20180371566A1

公开(公告)日：2018-12-27

申请号：US16061776

申请日：2016-12-21

Applicant: ArcelorMittal

Inventor： Maya GOSPODINOVA ,  Pavan VENKATASURYA

IPC: C21D8/02 ,  C22C38/38 ,  C22C38/26 ,  C22C38/22 ,  C22C38/02 ,  C22C38/06

Abstract: A method for producing a steel sheet, the method containing 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≤2.8%, 1.0%≤Si≤2.1%, 0.02%≤Al≤1.0%, with 1.7%≤Si+Al≤2.1%, 0≤Nb≤0.035%, 0≤Mo≤0.3%, 0≤Cr≤0.4%, 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 up to 35% of intercritical ferrite,quenching the sheet at a cooling rate of at least 20° C./s from a temperature of at least 600° C. down to a quenching temperature QT comprised between Ms-170° C. and Ms-80° C.,heating the sheet up to a partitioning temperature PT between 350° C. and 450° C. and maintaining the sheet at this temperature for a partitioning time Pt comprised between 80 s and 440 s,immediately cooling the sheet down to the room temperature, the steel sheet having a final microstructure consisting of, in surface fraction: between 40% and 70% of tempered martensite, between 7% and 15% of retained austenite, between 15% and 35% of ferrite, at most 5% of fresh martensite, at most 15% of bainite.

公开(公告)号：US20190003007A1

公开(公告)日：2019-01-03

申请号：US16064545

申请日：2016-12-21

Applicant: ArcelorMittal

Inventor： Pavan VENKATASURYA ,  Hyun Jo JUN

IPC: C21D9/46 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C21D8/02 ,  C21D6/00 ,  B32B15/01 ,  C21D1/18

Abstract: A method for producing a steel sheet having a microstructure including 71% to 91% martensite and bainite, 9% to 13% retained austenite, and at most 20% ferrite is provided. The method includes providing a cold-rolled steel sheet including, in weight percent: 0.13%≤C≤0.22%, 1.2%≤Si≤2.3%, 0.02%≤Al≤1.0%, with 1.25%≤Si+Al≤2.35%, 2.4%≤Mn≤3%, Ti≤0.05%, Nb≤0.05% and a remainder of Fe and unavoidable impurities, annealing the steel sheet to obtain 80% to 100% austenite and 0% to 20% ferrite, quenching the steel sheet at a cooling rate between 20° C./s and 50° C./s to a quenching temperature between 240° C. and 310° C., heating the steel sheet to a partitioning temperature between 400° C. and 465° C. and maintaining the steel sheet at the partitioning temperature for 50 to 250 seconds, then immediately cooling the sheet to room temperature. Steel sheets are also provided.

公开(公告)号：US20190003005A1

公开(公告)日：2019-01-03

申请号：US16064513

申请日：2016-12-21

Applicant: ArcelorMittal

Inventor： Hyun Jo JUN ,  Pavan VENKATASURYA

IPC: C21D9/46 ,  C21D6/00 ,  C21D1/22 ,  C21D8/02 ,  C22C38/26 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C23C2/06 ,  C23C2/28 ,  C23C2/40 ,  B32B15/01 ,  B32B15/18

Abstract: A method for producing a steel sheet is provided. The steel sheet has a microstructure including, in area fraction, 20% to 50% intercritical ferrite, 10% to 20% retained austenite, 25% to 45% tempered martensite, 10% to 20% fresh martensite, and bainite. The sum of tempered martensite and bainite is between 30% and 60%. The method includes providing a cold-rolled steel sheet including, in weight percent, 0.18%≤C≤0.25%, 0.9%≤Si≤1.8%, 0.02%≤Al≤1.0%, with 1.00%≤Si+Al≤2.35%, 1.5%≤Mn 2.5%, 0.010%≤Nb≤0.035%, 0.10%≤Cr≤0.40%, and a remainder including Fe and unavoidable impurities. The method further includes annealing the steel sheet to obtain 50% to 80% austenite and 20% to 50% of ferrite, quenching the sheet at a cooling rate between 20° C./s and 50° C./s to a quenching temperature between Ms-50° C. and Ms-5° C., heating the sheet to a partitioning temperature between 375° C. and 450° C. and maintaining the sheet at the partitioning temperature for at least 50 s, then immediately cooling the sheet to room temperature. A steel sheet is also provided.