A method of performing a localized post weld heat treatment on a weld seam in a thin wall metallic body may include attaching thermocouples to the outside surface of the weld seam and covering the weld seam with a thermal insulating blanket. Cooling bands are attached to the outside of the body on both sides of the weld seam. An inert atmosphere enclosure with inlet and exhaust ports is fitted over the weld seam, thermal insulating blanket, and cooling bands. A power supply and control system for an induction coil or coils situated in close proximity to the weld seam are actuated and the weld seam is subjected to a heat treatment without thermally affecting regions of the metallic body adjacent to the weld seam and external to the cooling bands.

A laser welded joint has weld metal provided between a plurality of steel sheets. A chemical composition of the weld metal has predetermined components, and average hardness of the weld metal is 350 to 540 in Vickers hardness. In the weld metal, distribution density of porosities having a diameter of 2 μm to 50 μm is equal to or less than 5.0 pieces/mm.sup.2. In the weld metal, distribution density of oxide inclusions having a diameter of 3 μm or more is 0.1 to 8.0 pieces/mm.sup.2.

A waterwall panel welding apparatus is provided. The apparatus includes an inlet assembly, a welding assembly, an outlet assembly, and a heating system. The inlet assembly is for receiving a plurality of tubes. The welding assembly is for receiving the tubes from the inlet assembly and for allowing the tubes to be welded together to form a waterwall panel. The outlet assembly is for receiving the waterwall panel from the welding assembly. The heating system heats the tubes and operates via magnetic induction.

A process for preparing a multi-thickness welded steel vehicle rail, the process comprises the steps of: (a) forming a first tube having a first outer diameter, an inner diameter and a first wall thickness; (b) forming a second tube having the first outer diameter, a second inner diameter and a second wall thickness different than the first wall thickness; (c) swaging a first end of the first tube to a second outer diameter less than the second inner diameter of the second tube; (d) inserting the swaged first end of the first tube into an end of the second tube to form a joint; (e) welding the first tube and the second tube together to form a weld at the joint to form a tube blank with a heat affected zone of lower metal strength in the area of the weld; (f) preheating the tube blank to create a common crystalline microstructure along a length of the tube blank; (g) introducing the tube blank into a blow molding tool having inner molding walls; (h) molding the tube blank at an elevated temperature by expanding the tube blank against the inner molding walls of the molding tool by injecting a pressurized medium into an interior cavity of the tube blank; and (i) quenching the tube blank by replacing the pressurized medium with a cooling medium through the molding tool and the tube blank to achieve a rapid cooling effect on the tube blank and to create a completed vehicle rail with essentially uniform material strength across the weld. A completed vehicle rail has an overlapped welded structure and uniform microcrystalline structure along the length of the rail.

A friction stir welding method for welding steel sheets together includes a heating device disposed ahead of a rotating tool in an advancing direction that preheats an unwelded portion before the welding thereof by the rotating tool and at the time of preheating, the surface temperature distribution in a direction perpendicular to the advancing direction in a position at which the welding by the rotating tool is initiated is set such that given that T.sub.Ac1 is the Ac.sub.1 point of a steel sheet, the maximum temperature (T.sub.U) thereof is 0.6×T.sub.Ac1<T.sub.U<1.8×T.sub.Ac1, and given that L is the width of the heating region exceeding a temperature (T.sub.L)=0.6×T.sub.Ac1, 0.3×d≦L≦2.0×d is satisfied with a diameter (d) of the shoulder.

A friction stir welding method for welding steel sheets together includes a heating device disposed ahead of a rotating tool in an advancing direction that preheats an unwelded portion before the welding thereof by the rotating tool and at the time of preheating, the surface temperature distribution in a direction perpendicular to the advancing direction in a position at which the welding by the rotating tool is initiated is set such that given that T.sub.Ac1 is the Ac.sub.1 point of a steel sheet, the maximum temperature (T.sub.U) thereof is 0.6×T.sub.Ac1<T.sub.U<1.8×T.sub.Ac1, and given that L is the width of the heating region exceeding a temperature (T.sub.L)=0.6×T.sub.Ac1, 0.3×d≦L≦2.0×d is satisfied with a diameter (d) of the shoulder.

A tube assembly includes at least first and second tubes configured for coupling at respective ends. The first and second tubes each include a base material, and a weld interface at the respective end. The weld interface is proximate to an inner diameter and an outer diameter of the first and second tubes, and includes a weld interface segment extending therebetween. A work hardened weld assembly couples the base material of each of the first and second tubes. The work hardened weld assembly includes a weld fusion zone between the weld interfaces of the first and second tubes and the weld interface segments of the first and second tubes. The weld fusion zone is work hardened and at least the weld interface segments of the first and second tubes are work hardened between the work hardened weld fusion zone and the base material of the first and second tubes.

A tube assembly includes at least first and second tubes configured for coupling at respective ends. The first and second tubes each include a base material, and a weld interface at the respective end. The weld interface is proximate to an inner diameter and an outer diameter of the first and second tubes, and includes a weld interface segment extending therebetween. A work hardened weld assembly couples the base material of each of the first and second tubes. The work hardened weld assembly includes a weld fusion zone between the weld interfaces of the first and second tubes and the weld interface segments of the first and second tubes. The weld fusion zone is work hardened and at least the weld interface segments of the first and second tubes are work hardened between the work hardened weld fusion zone and the base material of the first and second tubes.

A method of manufacturing a hot-stamped part includes: inserting a blank into a heating furnace including a plurality of sections with different temperature ranges; step heating the blank in multiple stages; and soaking the blank at a temperature of about Ac3 to about 1,000° C., wherein in the step of heating the blank, a temperature condition in the heating furnace satisfies the following equation: 0<(Tg−Ti)/Lt<0.025° C./mm, where Tg denotes a soaking temperature (° C.), Ti denotes an initial temperature (° C.) of the heating furnace, and Lt denotes a length (mm) of step heating sections.

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.