摘要:
A high-strength die-quenched part 1 is formed by heating a high-strength steel sheet 11 up to an austenite region, hot stamping and cooling inside a mold, and its microstructure has the martensite wherein carbide particles 2 are finely dispersed over an entire region including prior-austenite grain boundaries. It is desirable that the prior-austenite grain size in the microstructure of the high-strength steel sheet, which is a base material, be 10 μm or smaller. The high-strength die-quenched part has high-strength and high-ductility thanks to its martensite.
摘要:
A high-strength die-quenched part 1 is formed by heating a high-strength steel sheet 11 up to an austenite region, hot stamping and cooling inside a mold, and its microstructure has the martensite wherein carbide particles 2 are finely dispersed over an entire region including prior-austenite grain boundaries. It is desirable that the prior-austenite grain size in the microstructure of the high-strength steel sheet, which is a base material, be 10 μm or smaller. The high-strength die-quenched part has high-strength and high-ductility thanks to its martensite.
摘要:
A welding structural part 1 is manufactured by overlapping the surfaces of steel sheets 2, and forming a weld zone by spot welding. The weld zone 3 includes: a weld nugget 4; and a heat affected zone 5 surrounding the weld nugget 4, wherein the hardness in the weld zone increases along an exterior region 6 of the heat affected zone 5 toward the heat affected zone 5, and then decreases along the heat affected zone 5 toward the central region of the weld nugget 4. In the boundary region between the weld nugget 4 and the heat affected zone 5, the weld nugget 4 may have a convex portion 4A bulging into the heat affected zone 5 along the overlapped portion. The steel sheets 2 contain carbon in 0.15 mass % or more.
摘要:
A welding structural part 1 is manufactured by overlapping the surfaces of steel sheets 2, and forming a weld zone by spot welding. The weld zone 3 includes: a weld nugget 4; and a heat affected zone 5 surrounding the weld nugget 4, wherein the hardness in the weld zone increases along an exterior region 6 of the heat affected zone 5 toward the heat affected zone 5, and then decreases along the heat affected zone 5 toward the central region of the weld nugget 4. In the boundary region between the weld nugget 4 and the heat affected zone 5, the weld nugget 4 may have a convex portion 4A bulging into the heat affected zone 5 along the overlapped portion. The steel sheets 2 contain carbon in 0.15 mass % or more.
摘要:
A welding equipment for metallic materials capable of performing heat treatment such as tempering based on partial heating in spot welding is provided. The welding equipment sandwiches metallic materials with a pair of electrodes, and heats different regions of the metallic materials by energization, with the pair of electrodes maintained at the same position with respect to the metallic materials. The welding equipment includes a first heating means connected to the pair of electrodes for heating and welding the internal region of the circle defined by projecting the cross-sectional area of the axis of the electrodes on the metallic materials by applying power having a low first frequency, a second heating means for heating a ring-shaped region along the circle by applying power having a second frequency that is higher than the first frequency, and an energization control unit for independently controlling the first and the second heating means.
摘要:
A welding equipment for metallic materials capable of performing heat treatment such as tempering based on partial heating in spot welding is provided. The welding equipment 1 sandwiches metallic materials 9 with a pair of electrodes 4, 4, and heats different regions of the metallic materials 9 by energization, with the pair of electrodes 4, 4 maintained at the same position with respect to the metallic materials 9. The welding equipment includes a first heating means 6 connected to the pair of electrodes 4, 4 for heating and welding the internal region of the circle defined by projecting the cross-sectional area of the axis of the electrodes on the metallic materials by applying power having a low first frequency, a second heating means 8 for heating a ring-shaped region along the circle by applying power having a second frequency that is higher than the first frequency, and an energization control unit 10 for independently controlling the first and the second heating means 6, 8.
摘要:
A welding equipment for metallic materials capable of performing heat treatment such as tempering based on partial heating in spot welding is provided. The welding equipment 1 sandwiches metallic materials 9 with a pair of electrodes 4, 4, and heats different regions of the metallic materials 9 by energization, with the pair of electrodes 4, 4 maintained at the same position with respect to the metallic materials 9. The welding equipment includes a first heating means 6 connected to the pair of electrodes 4, 4 for heating and welding the internal region of the circle defined by projecting the cross-sectional area of the axis of the electrodes on the metallic materials by applying power having a low first frequency, a second heating means 8 for heating a ring-shaped region along the circle by applying power having a second frequency that is higher than the first frequency, and an energization control unit 10 for independently controlling the first and the second heating means 6, 8.
摘要:
There is provided an ultrahigh strength steel sheet containing 0.10 to 0.40 mass % of C, 0.01 to 3.5 mass % of Cr, at least one selected from the group consisting of 0.10 to 2.0 mass % of Mo, 0.20 to 1.5 mass % of W, 0.002 to 1.0 mass % of V, 0.002 to 1.0 mass % of Ti and 0.005 to 1.0 mass % of Nb, 0.02 mass % or less of P and 0.01 mass % or less of S as impurities and the balance being Fe and unavoidable impurities based on the total mass of the steel sheet and having a base structure of lower bainite, a prior austenite grain size of 30 μm or smaller and a tensile strength of 980 MPa or higher. There is also provided an automotive strength part using the ultrahigh strength steel sheet.
摘要:
A wire rod or a steel wire of a bamboo nano-structure, whose mean grain diameter in a C-direction section is 200 nm or smaller, is prepared by applying a hot or warm working and additionally applying a cold working to a steel and next, by performing a forging, by a tool or a die such as cold pressure production, to a section, of a desired, limited site, other than a section parallel to an L-direction, an equiaxed nano-structure, whose mean grain diameter is 200 nm or smaller, is formed in this site. As a typical example of a formed article, there is enumerated a high strength micro screw in which a shaft outer diameter is 1.6 mm or smaller, a surface layer part of a head part recess has equiaxed nano-structure and a hardness Hv≧300, and a screw main body portion has bamboo nano-structure and a hardness Hv≧250.
摘要:
A high strength phosphorus-containing steel having fine texture free from the problem of embrittlement by positively using the presence of P, which is a carbon steel having an average ferritic grain diameter of 3 &mgr;m or less and containing from 0.04 to 0.1% by mass of P, wherein the volume fraction of P segregated in the grain boundary accounts for 0.3 or less in case the grain boundary is covered by a P layer 1 nm in thickness.