摘要:
To establish a method for obtaining a hot-press-formed steel member, which exhibits high strength, high tensile elongation (ductility) and high bendability, thereby having excellent deformation characteristics at the time of collision crush (crashworthiness), and which is capable of ensuring excellent delayed fracture resistance. A method for producing a hot-press-formed steel member by heating a steel sheet, which has a chemical component composition containing 0.10% (% by mass, and hereinafter the same shall apply) to 0.30% (inclusive) of C, 1.0% to 2.5% (inclusive) of Si, 1.0% to 3.0% (inclusive) of Si and Al in total and 1.5% to 3.0% (inclusive) of Mn, with the balance consisting of iron and unavoidable impurities, and hot press forming the steel sheet one or more times. The method for producing a hot-press-formed steel member is characterized in that: the heating temperature is set to not less than the Ac3 transformation point; the starting temperature of the hot pressing is set to not more than the heating temperature but not less than the Ms point; and the average cooling rate from (the Ms point−150° C. to 40° C. is set to 5° C./s or less.
摘要:
In a method for obtaining a hot-press-formed steel member, a steel sheet containing 0.10-0.30 mass % of C, 1.0-2.5 mass % of Si, 1.0-3.0 mass % of Si and Al in total, and 1.5-3.0 mass % of Mn is heated at a heating temperature of not less than the Ac3 transformation point. The steel sheet is hot-press formed for one or more times. The starting temperature of the hot pressing is not more than the heating temperature but not less than the Ms point. The average cooling rate from (Ms point−150)° C. to 40° C. is 5° C./s or less. The hot-press-formed steel member has high strength, high tensile elongation, high bendability, excellent deformation characteristics at the time of collision crush, and excellent delayed fracture resistance.
摘要:
A press forming method forming an extended part by extension in a later forming period after deep drawing, the deep drawing process carried out with working at 100-250° C., and the extension forming process carried out colder at less than 50° C., whereby the extended part is formed by extension in a cup shaped low parts formed by deep drawing. Thus, press forming products containing formed elements can be deep drawing formed and extension formed at a high forming rate of 10 mm/sec or greater, which can assure high productivity. By making a steel plate temperature 100-350° C. during press forming and by making the forming rate in the later forming period where extension forming is carried out slower than the forming rate in an earlier forming period where extension forming is not carried out, cracking of the extended part can be prevented and press forming limitations can be improved.
摘要:
A press forming method forming an extended part by extension in a later forming period after deep drawing, the deep drawing process carried out with working at 100-250° C., and the extension forming process carried out colder at less than 50° C., whereby the extended part is formed by extension in a cup shaped low parts formed by deep drawing. Thus, press forming products containing formed elements can be deep drawing formed and extension formed at a high forming rate of 10 mm/sec or greater, which can assure high productivity. By making a steel plate temperature 100-350° C. during press forming and by making the forming rate in the later forming period where extension forming is carried out slower than the forming rate in an earlier forming period where extension forming is not carried out, cracking of the extended part can be prevented and press forming limitations can be improved.
摘要:
Disclosed is a method wherein when a steel sheet is subjected to warm or hot forming to produce a formed product by drawing with a punch and a die, the steel sheet is formed while the forming start temperature is controlled in accordance with the heating temperature of the steel sheet. By this method, when a steel sheet is subjected to warm or hot forming, good formability is obtained without the occurrence of fracture, cracking or the like during forming and also a formed product having good ductility is obtained.
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:
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:
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.
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 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.