摘要:
Disclosed is a high-strength steel plate with excellent warm workability that has a component composition comprising, in mass %, 0.05 to 0.4% C, 0.5 to 3% Si+Al, 0.5 to 3% Mn, no more than 0.15% P (not including 0%), and no more than 0.02% S (including 0%), with the remainder comprising iron and impurities, and a composition that includes a total of 45 to 80% martensite and/or bainitic ferrite in terms of the area ratio relative to the entire composition, 5 to 40% polygonal ferrite in terms of the area ratio relative to the entire composition, and 5 to 20% retained austenite in terms of the area ratio relative to the entire composition, wherein the C concentration (CγR) within said residual austenite is in the range of 0.6 mass % to less than 1.0 mass %, and that furthermore may include bainite. In the high-strength steel plate, TRIP effects are achieved to the fullest extent in warm working, and increased ductility over prior steel plates is reliably achieved.
摘要:
Disclosed is a high-strength steel plate with excellent warm workability that has a component composition comprising, in mass %, 0.05 to 0.4% C, 0.5 to 3% Si+Al, 0.5 to 3% Mn, no more than 0.15% P (not including 0%), and no more than 0.02% S (including 0%), with the remainder comprising iron and impurities, and a composition that includes a total of 45 to 80% martensite and/or bainitic ferrite in terms of the area ratio relative to the entire composition, 5 to 40% polygonal ferrite in terms of the area ratio relative to the entire composition, and 5 to 20% retained austenite in terms of the area ratio relative to the entire composition, wherein the C concentration (CγR) within said residual austenite is in the range of 0.6 mass % to less than 1.0 mass %, and that furthermore may include bainite. In the high-strength steel plate, TRIP effects are achieved to the fullest extent in warm working, and increased ductility over prior steel plates is reliably achieved.
摘要:
A cold-rolled steel sheet of the present invention which has a composition containing, in terms of % by mass, C: 0.05-0.30%, Si: 3.0% or less (including 0%), Mn: 0.1-5.0%, P: 0.1% or less (including 0%), S: 0.010% or less (including 0%), and Al: 0.001-0.10%, and remainder being mainly iron, and which has a structure comprising, in terms of area ratio, 10-80% ferrite, less than 5% (including 0%) of the sum of retained austenite and martensite, and a hard phase as the remainder. The steel sheet gives a KAM value frequency distribution curve in which the relationship between the proportion of frequency having a KAM value ≦0.4, XKAM≦0.4°, and the area ratio of ferrite, Vα satisfies XKAM≦0.4°/Vα≧0.8 and the proportion of frequency having a KAM value in the range of 0.6-0.8, XKAM=0.6-0.8° is 10-20%. In the hard phase adjoining the ferrite, cementite, grains having an equivalent circle diameter of 0.1 μm or larger exist so that three or less such cementite grains are dispersed per μm2 of the hard phase. The steel sheet has improved balance between elongation and stretch flangeability and has better formability.
摘要:
The invention provides a high-strength cold-rolled steel sheet which is improved in elongation and stretch-flangeability and exhibits more excellent formability. The high-strength cold-rolled steel sheet has a composition which contains by mass C: 0.03 to 0.30%, Si: 0.1 to 3.0%, Mn: 0.1 to 5.0%, P: 0.1% or below, S: 0.005% or below, N: 0.01% or below, and Al: 0.01 to 1.00% with the balance consisting of iron and unavoidable impurities. The high-strength cold-rolled steel sheet has a structure which comprises at least 40% (up to 100% inclusive) in terms of area fraction of tempered martensite having a hardness of 300 to 380 Hv and the balance ferrite. The cementite particles in the tempered martensite take such dispersion that 10 or more cementite particles having equivalent-circle diameters of 0.02 to less than 0.1 μm are present per one μm2 of the tempered martensite and three or fewer cementite particles having equivalent-circle diameters of 0.1 μm or above are present per one μm2 of the tempered martensite.
摘要:
A high-strength steel sheet has a chemical composition including 0.05% to 0.3% of C, 1% to 3% of Si, 0.5% to 3% of Mn, 0% to 0.1% of P, 0.001% to 0.1% of Al, and 0.002% to 0.03% of N, in mass percent; further includes iron and impurities; and has a structure including 50% to 90% of bainitic ferrite, 5% to 20% of retained austenite (γR), a total of 10% to 50% of martensite and the retained austenite, and 0% to 40% of polygonal ferrite, in area percent based on the entire structure. The retained austenite has a carbon content (CγR) of 0.5% to 1.2% by mass, an average equivalent circle diameter of 0.2 to 2 μm, and an average aspect ratio (maximum diameter/minimum diameter) of less than 3.0. The high-strength steel sheet excels both in elongation and deep drawability while having a strength of 980 MPa or more.
摘要:
This high-strength hot-rolled steel plate contains specific amounts of C, Si, Mn, Al, V and also Ti and/or Nb so as to fulfill C−12(V/51+Ti/48+Nb/93)>0.03, and the rest consists of iron and unavoidable impurities. Ferrite is the main microstructure, the remaining microstructure is one or more selected from the group consisting of bainite, martensite and retained austenite, wherein the average particle diameter of precipitated carbides (the total content of V, Ti and Nb is 0.02% or greater) in the ferrite is less than 6 nm.
摘要:
Disclosed is a high-strength cold-rolled steel sheet having improved stretch-flange formability and excellent hydrogen embrittlement resistance. In addition to Fe, C, Si, Mn, P, S, N, and Al, the steel sheet contains V or at least one element of Nb, Ti and Zr. The contents of the at least one element of Nb, Ti and Zr, if present, satisfy the expression of [% C]−[% Nb]/92.9×12−[% Ti]/47.9×12−[% Zr]/91.2×12>0.03. The steel sheet has an area ratio of tempered martensite of 50% or more with ferrite as the remainder. The number of precipitates having a circle-equivalent diameter of 1 to 10 nm is 20 particles or more per 1 μm2 of the tempered martensite. The number of precipitates containing V or the at least one element of Nb, Ti and Zr and having a circle-equivalent diameter of 20 nm or more is 10 particles or less per 1 μm2 of the tempered martensite.
摘要:
A high-strength steel sheet has a chemical composition including 0.05% to 0.3% of C, 1% to 3% of Si, 0.5% to 3% of Mn, 0% to 0.1% of P, 0% to 0.01% of S, 0.001% to 0.1% of Al, and 0.002% to 0.03% of N in mass percent; further includes iron and impurities; and has a structure including 50% to 90% of bainitic ferrite, 3% or more of retained austenite (γR), a total of 10% to 50% of martensite and the retained austenite, and 0% to 40% of polygonal ferrite in area percent based on the entire structure. The retained austenite has a carbon content (CγR) of 0.5% to 1.2% by mass. The steel sheet includes 0.3% or more of the retained austenite that is surrounded by martensite. The high-strength steel sheet has a strength of 980 MPa or more and exhibits better ductility.
摘要:
A cold-rolled steel sheet of the present invention which has a composition containing, in terms of % by mass, C: 0.05-0.30%, Si: 3.0% or less (including 0%), Mn: 0.1-5.0%, P: 0.1% or less (including 0%), S: 0.010% or less (including 0%), and Al: 0.001-0.10%, and remainder being mainly iron, and which has a structure comprising, in terms of area ratio, 10-80% ferrite, less than 5% (including 0%) of the sum of retained austenite and martensite, and a hard phase as the remainder. The steel sheet gives a KAM value frequency distribution curve in which the relationship between the proportion of frequency having a KAM value ≦0.4, XKAM≦0.4°, and the area ratio of ferrite, Vα satisfies XKAM≦0.4°/Vα≧0.8 and the proportion of frequency having a KAM value in the range of 0.6-0.8, XKAM=0.6-0.8° is 10-20%. In the hard phase adjoining the ferrite, cementite, grains having an equivalent circle diameter of 0.1 μm or larger exist so that three or less such cementite grains are dispersed per μm2 of the hard phase. The steel sheet has improved balance between elongation and stretch flangeability and has better formability.
摘要:
This high-strength steel plate has a component composition including, by mass %, C: 0.02-0.3%, Si: 1-3%, Mn: 1.8-3%, P: 0.1% or less, S: 0.01% or less, Al: 0.001-0.1%, N: 0.002-0.03%, the rest consisting of iron and impurities. Said steel plate has a microstructure including, in terms of area ratio relative to the entire microstructure, each of the following phases: bainitic ferrite: 50-85%; retained γ; 3% or greater; martensite+the aforementioned retained γ; 10-45%; and ferrite: 5-40%. The C concentration (CγR) in the aforementioned retained austenite is 0.3-1.2 mass %, part or all of the N in the aforementioned component composition is solid solution N, and the amount of said solid solution N is 30-100 ppm.