公开(公告)号：EP3228722A4

公开(公告)日：2017-11-08

申请号：EP16752073

申请日：2016-01-25

申请人： JFE STEEL CORP

发明人： OBATA YOSHIE ,  KAWASAKI YOSHIYASU ,  UEDA KEIJI ,  KANEKO SHINJIRO ,  YOKOTA TAKESHI ,  SETO KAZUHIRO

IPC分类号： C22C38/00 ,  C21D8/02 ,  C21D9/46 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/18 ,  C22C38/60 ,  C23C2/06

CPC分类号： C22C38/60 ,  C21D8/0236 ,  C21D8/0268 ,  C21D9/46 ,  C21D2211/001 ,  C21D2211/004 ,  C21D2211/005 ,  C21D2211/008 ,  C21D2211/009 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/18 ,  C23C2/06

摘要： Provided are a thin high-strength cold-rolled steel sheet having small in-plane anisotropies and a method for producing the thin high-strength cold-rolled steel sheet. A steel having a composition containing, by mass, C: more than 0.20% and 0.45% or less, Si: 0.50% to 2.50%, Mn: 2.00% or more and less than 3.50%, and one or two elements selected from Ti: 0.005% to 0.100% and Nb: 0.005% to 0.100% is hot-rolled and subsequently cold-rolled at a rolling reduction of 30% or more. The resulting thin cold-rolled steel sheet is heated to 800°C to 950°C and subsequently cooled to a cooling-end temperature of 350°C to 500°C at a cooling rate of 5 °C/s or more to form a steel sheet having a microstructure including a martensite phase and a bainite phase such that the total proportion of the martensite phase and the bainite phase is 80% or more by volume. The steel sheet is heated to 700°C to 840°C and maintained at 700°C to 840°C, subsequently cooled to a cooling-end temperature of 350°C to 500°C at a cooling rate of 5 to 50 °C/s, and maintained within the above temperature range for 10 to 1800 s. This enables a microstructure including, by volume, 15% or more and 70% or less ferrite phase, more than 15% and 40% or less retained austenite phase, and 30% or less martensite phase to be formed. Furthermore, a retained austenite phase constituted by acicular and fine crystal grains having an average diameter of 2.0 µm or less and an aspect ratio of 2.0 or more can be formed. As a result, the thin high-strength cold-rolled steel sheet has excellent production consistency, a TS of 980 MPa or more, high ductility, and small in-plane anisotropies.

公开(公告)号：EP3178953A4

公开(公告)日：2017-07-05

申请号：EP15829161

申请日：2015-08-05

申请人： JFE STEEL CORP

发明人： KAWASAKI YOSHIYASU ,  MATSUDA HIROSHI ,  OBATA YOSHIE ,  KANEKO SHINJIRO ,  YOKOTA TAKESHI ,  SETO KAZUHIRO

IPC分类号： C22C38/00 ,  C21D8/02 ,  C21D9/46 ,  C22C18/04 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/60 ,  C23C2/00

CPC分类号： C21D9/46 ,  C21D6/005 ,  C21D6/008 ,  C21D8/0205 ,  C21D8/0226 ,  C21D8/0236 ,  C21D8/0263 ,  C21D8/0273 ,  C21D8/0278 ,  C21D2211/001 ,  C21D2211/002 ,  C21D2211/005 ,  C21D2211/008 ,  C22C18/04 ,  C22C38/00 ,  C22C38/001 ,  C22C38/002 ,  C22C38/005 ,  C22C38/008 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/38 ,  C22C38/60 ,  C23C2/02 ,  C23C2/06 ,  C23F17/00

摘要： Disclosed is a high-strength steel sheet having a tensile strength (TS) of 780 MPa or more and excellent in ductility, stretch flangeability, surface characteristics, and stability as a material that can be obtained by providing a predetermined chemical composition and a steel microstructure that contains, by area, 25-80 % of ferrite and bainitic ferrite in total, and 3-20 % of martensite, and that contains, by volume, 10 % or more of retained austenite, in which the retained austenite has a mean grain size of 2 µm or less, a mean Mn content in the retained austenite in mass% is at least 1.2 times the Mn content in the steel sheet in mass%, an area ratio of retained austenite having a mean C content in mass% at least 2.1 times the C content in the steel sheet in mass% is 60 % or more of an area ratio of the entire retained austenite.

摘要翻译： 本发明提供具有780MPa以上的拉伸强度（TS），延展性，拉伸凸缘性，表面特性和稳定性优异的高强度钢板，作为可通过提供预定的化学组成和钢的微结构而获得的材料 其含有总计25〜80％的铁素体和贝氏体铁素体和3〜20％的马氏体，并且以体积计含有10％以上的残留奥氏体，其中，残留奥氏体的平均晶粒 尺寸为2μm以下时，残留奥氏体中的平均Mn含量以质量％计为钢板中的Mn含量的1.2倍以质量％计，残留奥氏体的平均C含量以质量％计至少为 以质量％计，钢板中的C含量的2.1倍为残留奥氏体整体的面积率的60％以上。

公开(公告)号：EP3178956A4

公开(公告)日：2017-06-28

申请号：EP15830428

申请日：2015-08-05

申请人： JFE STEEL CORP

发明人： KAWASAKI YOSHIYASU ,  MATSUDA HIROSHI ,  OBATA YOSHIE ,  KANEKO SHINJIRO ,  YOKOTA TAKESHI ,  SETO KAZUHIRO

IPC分类号： C22C38/00 ,  C21D8/02 ,  C21D9/46 ,  C22C18/04 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/14 ,  C22C38/32 ,  C22C38/60 ,  C23C2/00

CPC分类号： C21D9/46 ,  C21D8/0205 ,  C21D8/0226 ,  C21D8/0236 ,  C21D8/0263 ,  C21D8/0273 ,  C21D2211/001 ,  C21D2211/002 ,  C21D2211/005 ,  C21D2211/008 ,  C22C18/04 ,  C22C38/00 ,  C22C38/001 ,  C22C38/002 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/12 ,  C22C38/14 ,  C22C38/28 ,  C22C38/32 ,  C22C38/38 ,  C22C38/60 ,  C23C2/06 ,  C23C2/28 ,  C23C2/40

摘要： Disclosed is a high-strength steel sheet having a tensile strength (TS) of 780 MPa or more and excellent in ductility, stretch flangeability, and stability as a material that can be obtained by providing a predetermined chemical composition, satisfying the condition that Mn content divided by B content equals 2100 or less, and providing a steel microstructure that contains, by area, 25-80 % of ferrite and bainitic ferrite in total, 3-20 % of martensite, and that contains, by volume, 10 % or more of retained austenite, in which the retained austenite has a mean grain size of 2 µm or less, a mean Mn content in the retained austenite in mass% is at least 1.2 times the Mn content in the steel sheet in mass%, and an aggregate of retained austenite formed by seven or more identically-oriented retained austenite grains accounts for 60 % or more by area of the entire retained austenite.

摘要翻译： 本发明提供具有780MPa以上的拉伸强度（TS），延展性，延伸凸缘性和稳定性优异的高强度钢板作为可通过提供预定化学组成而获得的材料，满足以下条件：Mn含量 除以B含量等于或小于2100，并且提供钢组织，其按总面积含有25-80％的铁素体和贝氏体铁素体，3-20％的马氏体，并且按体积计含有10％或更多 残留奥氏体的平均结晶粒径为2μm以下的残留奥氏体的残留奥氏体中的残留奥氏体的平均Mn含量以质量％计为钢板中的Mn含量的1.2倍以上， 由7个以上相同取向的残余奥氏体晶粒形成的残余奥氏体占整个残余奥氏体面积的60％或更多。