Abstract: An automobile chassis part which is excellent in low cycle fatigue characteristics, characterized by being formed by steel which contains, by mass %, C: 0.02 to 0.10%, Si: 0.05 to 1.0%, Mn: 0.3 to 2.5%, P: 0.03% or less, S: 0.01% or less, Ti: 0.005 to 0.1%, Al: 0.005 to 0.1%, N: 0.0005 to 0.006%, and B: 0.0001 to 0.01 and has a balance of Fe and unavoidable impurities, in which 80% or more of the part structure comprises a bainite structure and in which a portion where a ratio R/t of the thickness “t” and external surface curvature radius R is 5 or less has an X-ray half width of an (211) plane of 5 (deg) or less.

Abstract: A method of press-forming a tubular part having a cross section of an irregular shape crushes a steel tube between an upper die and a lower die in order to form a V-shaped cross section. When the curvature radius of a tip of the upper die is defined as R1, the curvature radius of a bottom portion of the lower die corresponding to the tip of the upper die is defined as R2, and the wall thickness of the steel tube is defined as t; R1, R2, and t satisfy R1+2t=R2 and 1.5t?R1?3t.

Abstract: The present invention provides a steel material for automobile chassis parts which has high fatigue characteristics, does not require much cost for heat treatment, and further is superior in shapeability and a method of production of automobile chassis parts using this steel material, that is, one being a steel material to which Nb and Mo have been compositely added and having a difference 50 to 150 points between a Vicker's hardness of the center of plate thickness and a maximum value of Vicker's hardness within 0.5 mm from the surface after bending by a bending R of the plate outer surface of 2 to 5 times the plate thickness. The surface is high in hardness and the center part is low in hardness, so the fatigue characteristics and shapeability are superior. Note that if annealing under conditions giving a tempering parameter ? defined by ?=T(20+log(t)) of 14000 to 19000 (where T is the absolute temperature, t is the time (h), and the temperature rise is 660° C.

Abstract: The present invention provides a steel material for automobile chassis parts, having high fatigue characteristics, without a heat treatment, and superior shapeability, and a method of production of such automobile chassis parts. The surface of the steel has a high hardness and the center has a low hardness, providing the superior characteristics. With an annealing step of the invention, it is possible to relieve internal stress and further improve fatigue characteristics.

Abstract: An automobile chassis part which is excellent in low cycle fatigue characteristics, characterized by being formed by steel which contains, by mass %, C: 0.02 to 0.10%, Si: 0.05 to 1.0%, Mn: 0.3 to 2.5%, P: 0.03% or less, S: 0.01% or less, Ti: 0.005 to 0.1%, Al: 0.005 to 0.1%, N: 0.0005 to 0.006%, and B: 0.0001 to 0.01 and has a balance of Fe and unavoidable impurities, in which 80% or more of the part structure comprises a bainite structure and in which a portion where a ratio R/t of the thickness “t” and external surface curvature radius R is 5 or less has an X-ray half width of an (211) plane of 5 (deg) or less.

Abstract: The present invention provides a steel material for automobile chassis parts, having high fatigue characteristics, without a heat treatment, and superior shapeability, and a method of production of such automobile chassis parts. The surface of the steel has a high hardness and the center has a low hardness, providing the superior characteristics. With an annealing step of the invention, it is possible to relieve internal stress and further improve fatigue characteristics.

Abstract: A method of press-forming a tubular part having a cross section of an irregular shape crushes a steel tube between an upper die and a lower die in order to form a V-shaped cross section. When the curvature radius of a tip of the upper die is defined as R1, the curvature radius of a bottom portion of the lower die corresponding to the tip of the upper die is defined as R2, and the wall thickness of the steel tube is defined as t; R1, R2, and t satisfy R1+2t=R2 and 1.5t?R1?3t.

Abstract: The present invention provides a steel material for automobile chassis parts which has high fatigue characteristics, does not require much cost for heat treatment, and further is superior in shapeability and a method of production of automobile chassis parts using this steel material, that is, one being a steel material to which Nb and Mo have been compositely added and having a difference 50 to 150 points between a Vicker's hardness of the center of plate thickness and a maximum value of Vicker's hardness within 0.5 mm from the surface after bending by a bending R of the plate outer surface of 2 to 5 times the plate thickness. The surface is high in hardness and the center part is low in hardness, so the fatigue characteristics and shapeability are superior. Note that if annealing under conditions giving a tempering parameter ? defined by ?=T(20+log(t)) of 14000 to 19000 (where T is the absolute temperature, t is the time (h), and the temperature rise is 660° C.

Abstract: A highly impact-resistant member has a round or square sectional shape, that is excellent in strength and toughness, does not undergo the deterioration of toughness in the vicinity of the welded portion, and a highly impact-resistant steel pipe has a tensile strength TS of 1,700 MPa or more and a yield ratio YR of 72% or less, the yield ratio being the ratio of a 0.1%-proof stress YS to a tensile strength TS (YS/TS). The toughness of the welded portion of the steel pipe is enhanced by controlling the Si amount in the steel of the steel pipe in the range from Mn/8?0.07 to Mn/8+0.07. The steel contains, in mass, 0.19 to 0.35% C, 0.10 to 0.30% Si, 0.5 to 1.60% Mn, not more than 0.025% P, not more than 0.01% S, 0.010 to 0.050% Al, 2 to 35 ppm B and 0.005 to 0.05% Ti as indispensable components.

Abstract: Lubricative stainless steel sheet and pipe having a chromate film on at least one of the surfaces of a stainless steel sheet or pipe substrate, the chromate film having an amount of adhered Cr of 5 to 100 mg/m2, and, on the chromate film, a lubricant film obtained by applying, on the chromate film, a water-base coating containing (a) a urethane resin of ether-ester type having a skeleton of bisphenol type, a skeleton of ester, and a carboxyl group, (b) an epoxy resin, and (c) a polyolefin wax, and baking the applied coating, the sum of the amount of the urethane resin of (a) and the epoxy resin of (b) being 70 to 95% by weight of the total solids of the coating, the amount of the polyolefin wax of (c) being 5 to 30% by weight of the total solids of the coating, and the lubricant film having a thickness of 0.5 to 5 micrometers and a Vickers hardness of at least 15. A method of producing a lubricative stainless steel pipe is also disclosed.