Abstract: A bent member having excellent dimensional accuracy is manufactured by stably forming a high temperature portion uniformly in the circumferential direction of a steel tube and in a narrow region in the axial direction of the steel. The bent member is manufactured by supporting a steel tube at a first position while feeding it, performing induction heating of the steel tube at a second position with an induction heating coil, cooling the steel tube at a third position to form a high temperature portion which moves in the axial direction of the steel tube, and three-dimensionally varying the position of a gripping mechanism for the steel tube in a region to apply a bending moment to the high temperature portion.

Abstract: An induction heating coil for stably heating a steel tube which is being fed in its axial direction without rotating, the heating being uniform in the circumferential direction and in a narrow range in the axial direction has at least two 1-turn coils in the form of a first turn coil body and a second turn coil body. The inner peripheral length Ln (the non-effective coil length) where the effective number of coil turns is less than the total number of coil turns when the coil is projected in the axial direction and the inner peripheral length L0 of the projected coil bodies (the inner coil length) satisfy Ln/L0<0.05. First and second coil bodies have insulating portions on their connecting portions, and the insulating portions are present in locations separated by a central angle of 5-45° measured from the center of the coil bodies.

Abstract: A front side member having a single body formed from a tubular body having a closed cross section has a front portion which extends in the fore and aft direction of a vehicle body, a sloping portion which is continuous with the front portion and slopes downwards along a dash panel, and a rear portion continuous with the sloping portion and extending along the bottom surface of a floor panel joined to the dash panel. A portion of the front portion is an unquenched portion which has not undergone quenching treatment and the remainder is a high frequency quenched portion which has undergone high frequency quenching. The sloping portion is a high frequency quenched portion. A portion of the rear portion is an unquenched portion which has not undergone quenching and the remainder other than that portion is a high frequency quenched portion which has undergone high frequency quenching.

Abstract: An arm material for an upper arm or a lower arm is provided which constitutes a double wishbone suspension or the like of an automobile and which has a flat, hollow, closed cross-sectional shape and enables further decreases in size, decreases in weight, and increases in strength. An arm material for an automobile suspension has a body made from a parts material made by metal. The parts material made by metal has a flat, hollow, closed cross-sectional shape having a pair of opposing long sides and is formed from a single member in its lengthwise direction. The body has at least a first bent portion which is bent in a plane roughly parallel to the pair of long sides.

Abstract: An arm material for an upper arm or a lower arm is provided which constitutes a double wishbone suspension or the like of an automobile and which has a flat, hollow, closed cross-sectional shape and enables further decreases in size, decreases in weight, and increases in strength. An arm material for an automobile suspension has a body made from a parts material made by metal. The parts material made by metal has a flat, hollow, closed cross-sectional shape having a pair of opposing long sides and is formed from a single member in its lengthwise direction. The body has at least a first bent portion which is bent in a plane roughly parallel to the pair of long sides.

Abstract: A manufacturing method for a bent product which can guarantee a high working accuracy and which can provide a large bending angle without damage to the surface condition of a metal material even when a widely varying bent shape is desired or when it is necessary to perform bending of a high strength metal material.

Abstract: A strength member for an automobile body such as a side member or a pillar which has a bent portion which is bent two-dimensionally or three-dimensionally and which has an ultrahigh strength with a tensile strength exceeding 1100 MPa is provided. The strength member for an automobile body has a tubular body which has a closed cross section which does not have an outwardly-extending flange and which has a bent portion which is bent two-dimensionally or three-dimensionally, a portion to be cut or punched, and a portion to be welded.

Abstract: A lightweight hollow member having excellent stiffness and impact properties and which is suitable for automotive parts due to having a high strength such as at least 780 MPa and a complicated shape is provided. A hollow member 11 has a hollow steel body 14. The body 14 is constituted by a single member at least in the lengthwise direction. The body 14 has a flat cross section having at least a portion with a maximum outer dimension L1 and a portion with an outer dimension L2 shorter than the maximum outer dimension L1. The body 14 has a twisted portion in a portion of its length.

Abstract: A bent metal member which is obtained by bending accompanied by heat treatment of a zinc-based coated metal material and which is suitable for use in components of automobiles due to having a high strength and excellent post-painting corrosion resistance is manufactured. The outer surface of a tubular metal material having on its surface a Zn—Fe alloy coating layer with a coating weight of 30-90 g/m2 per side, an Fe content of 8-20%, and a surface roughness Ra of at most 0.8 ?m is supported at two locations spaced in the axial direction of the metal material so that the material can move in its axial direction, the metal material is heated between the two locations to a temperature range of at least the Ac3 point at a heating speed such that the rate of temperature increase is at least 3.0×102° C. per second while feeding the metal material in its axial direction, holding so that the length of time for which the surface of the metal material is at 8.0×102° C.

Abstract: A heat treated galvannealed steel material having excellent post-painting corrosion resistance and a high strength which is suitable for use as an automotive part and a method for its manufacture are provided. A galvannealed steel material having a galvannealed coating on at least one side thereof is heat treated by heating at least a portion thereof to a temperature range in which hardening is possible. The coating remaining on the surface of at least a part of the portion which underwent heat treatment has a coating weight of at least 20 g/m2 and at most 80 g/m2 per side and an Fe content of at least 15% and at most 35%, an ? phase is present in the coating, and the centerline average roughness Ra of the surface of the coating is at most 1.5 ?m.

Abstract: An arm material for an upper arm or a lower arm is provided which constitutes a double wishbone suspension or the like of an automobile and which has a flat, hollow, closed cross-sectional shape and enables further decreases in size, decreases in weight, and increases in strength. An arm material for an automobile suspension has a body made from a parts material made by metal. The parts material made by metal has a flat, hollow, closed cross-sectional shape having a pair of opposing long sides and is formed is from a single member in its lengthwise direction. The body has at least a first bent portion which is bent in a plane roughly parallel to the pair of long sides.

Abstract: A strength member for an automobile body such as a side member or a pillar which has a bent portion which is bent two-dimensionally or three-dimensionally and which has an ultrahigh strength with a tensile strength exceeding 1100 MPa is provided. The strength member for an automobile body has a tubular body which has a closed cross section which does not have an outwardly-extending flange and which has a bent portion which is bent two-dimensionally or three-dimensionally, a portion to be cut or punched, and a portion to be welded.