Provided are thick hot-rolled composite-phase steel having excellent durability and a manufacturing method therefor. The thick composite-phase steel having excellent durability according to the present invention comprises, by wt %, C: 0.05 to 0.15%, Si: 0.01 to 1.0%, Mn: 1.0 to 2.3%, Al: 0.01 to 0.1%, Cr: 0.005 to 1.0%, P: 0.001 to 0.05%, S: 0.001 to 0.01%, N: 0.001 to 0.01%, Nb: 0.005 to 0.07%, Ti: 0.005 to 0.11%, Fe, and inevitable impurities, and has a mixed phase of ferrite and bainite as a base structure, wherein, in the base structure, the area fraction of each of a pearlite phase and a martensite and austenite (MA) phase is less than 5%, and the area fraction of a martensite phase is less than 10%.

The invention provides a method for the inductive surface layer hardening of a surface running around an annular component of a hardenable steel, which achieves uniform and uninterrupted hardening. For this purpose, a) an initial zone of the surface is surface layer hardened by it being brought to hardening temperature by means of an inductor and being quenched with a spray. b) The surface is then hardened by means of a stationarily arranged inductor arrangement and a movably arranged inductor arrangement, which each comprise a leading inductor for preheating the region of the surface covered by it, a trailing inductor offset in the direction of the initial zone for finish-heating the pre-heated region to the hardening temperature and a spray for quenching the finish-heated region, wherein the movable inductor arrangement is moved along the surface and at the same time the annular component rotates about an axis of rotation in order to move the surface to be hardened along the stationary inductor arrangement. The speed of the movable inductor arrangement along the surface is greater than its circumferential speed. c) An end zone of the surface is then hardened by the leading inductor of one of the inductor arrangements being moved temporarily in the direction of the end zone at an increased feed rate compared to its trailing inductor when the end zone is located at a certain distance from inductor arrangements such that an enlarged distance results between the leading inductor and the inductor trailing it and the leading inductor is located at the end zone by a time interval earlier, whose duration is equal to the duration required by the trailing inductor to cover the distance resulting between the trailing inductor and the leading inductor such that the at least one leading inductor arriving first at the end zone preheats the end zone until the trailing inductor is located at the end zone and finish-heats the end zone to hardening temperature. Finally, the finish-heated end zone is quenched by means of a spray.

The present invention suppresses leakage of combustion gas from a contact surface. A cylinder head (20) is attached to a cylinder block. The surface (26) of the side of the cylinder head (20) that is attached to the cylinder block includes a first region (AH1) and a second region (AH2) that has higher hardness than the first region (AH1).

The invention concerns a method for production of a steel tubular product (1), in particular an airbag tubular product, with the following steps: a) provision of a steel tube (2), b) shaping of the steel tube (2) into a pre-geometry (3), wherein in an end region (4), an outer diameter (5) of the steel tube (2) is reduced by axial movement into an outer tool, c) calibration of an inner diameter (7) of the pre-geometry (3), wherein the pre-geometry (3) is still laid in the outer tool, and an inner mandrel, with an outer diameter corresponding to the inner diameter (7) of the calibrated pre-geometry (3), is introduced into the end region (4) of the pre-geometry (3), and the pre-geometry (3) is pressed against the outer tool such that the inner diameter (7) of the pre-geometry (3) is calibrated by shaping, d) removal of the pre-geometry (3) from the outer tool (5) and removal of the inner mandrel from the pre-geometry (3), e) axial movement of the pre-geometry (3) into a drawing tool with a roll-in contour having a pot-like concavity, with simultaneous shaping of the pre-geometry (3) into the tubular product (1) with a rotationally symmetrical outlet opening (8) positioned centrally in the end face, f) removal of the tubular product (1) from the drawing tool.

A gas pressure container for an airbag system of a motor vehicle is disclosed having a tube element with a high bursting resistance when internal pressure is being applied. The tube element includes a steel alloy and a first longitudinal portion of the tube element has a tensile strength Rm,.sub.11 higher than (>) 800 MPa, a transition temperature Tu,.sub.11 of at least −40° C., and an outer circumference U1. The tube element also includes at least one second longitudinal portion and/or additional longitudinal portions, which extend axially from the first longitudinal portion. The second longitudinal portion or the additional longitudinal portions and the first longitudinal portion are formed from a seamless or welded single-piece tube made of a uniform material, and more specifically from a hot-rolled or cold-drawn tube.

A welded steel part with a very high mechanical strength is provided. The welded steel part is obtained by heating followed by hot forming, then cooling of at least one welded blank obtained by butt welding of at least one first and one second sheet. The at least one first and second sheets including, at least in part, a steel substrate and a pre-coating which includes an intermetallic alloy layer in contact with the steel substrate, topped by a metal alloy layer of aluminum or aluminum-based alloy. A method for the fabrication of a welded steel part and the fabrication of structural or safety parts for automotive vehicles are also provided.

A leaf spring device includes a main leaf made of a steel plate including an elastic section configured to generate elastic force when bent; and an eye section formed in an end portion of the elastic section, the elastic section and the eye section being tempered. There is also provided a method for manufacturing the leaf spring device. The eye section is formed by rolling the end of the elastic section into a circular form. The eye section is tempered at a higher temperature than the elastic section.

A welded steel part with a very high mechanical strength is provided. The welded steel part is obtained by heating followed by hot forming, then cooling of at least one welded blank obtained by butt welding of at least one first and one second sheet. The at least one first and second sheets including, at least in part, a steel substrate and a pre-coating which includes an intermetallic alloy layer in contact with the steel substrate, topped by a metal alloy layer of aluminum or aluminum-based alloy. A method for the fabrication of a welded steel part and the fabrication of structural or safety parts for automotive vehicles are also provided.

A welded steel part with a very high mechanical strength is provided. The welded steel part is obtained by heating followed by hot forming, then cooling of at least one welded blank obtained by butt welding of at least one first and one second sheet. The at least one first and second sheets including, at least in part, a steel substrate and a pre-coating which includes an intermetallic alloy layer in contact with the steel substrate, topped by a metal alloy layer of aluminum or aluminum-based alloy. A method for the fabrication of a welded steel part and the fabrication of structural or safety parts for automotive vehicles are also provided.

A stud-weldable rebar and a method for making the rebar are disclosed. The rebar has a steel body with a weld end and a diameter that is substantially uniform along a length of the body. A tip portion at the weld end includes a hardened zone and a base portion is formed of the remaining steel body. The hardened zone has a hardness that is about 1.5-3.0 times greater than a hardness of the base portion. Induction hardening is used to form the hardened zone.