A spot welded joint of at least two steel sheets is provided. At least one of the steel sheets presents yield strength above or equal to 600 MPa, an ultimate tensile strength above or equal to 1000 MPa, uniform elongation above or equal to 15%. The base metal chemical composition includes 0.05≤C≤0.21%, 4.0≤Mn≤7.0%, 0.5≤Al≤3.5%, Si≤2.0%, Ti≤0.2%, V≤0.2%, Nb≤0.2%, P≤0.025%, B≤0.0035%, and the spot welded joint contains a molten zone microstructure containing more than 0.5% of Al and containing a surface fraction of segregated areas lower than 1%, said segregated areas being zones larger than 20 μm.sup.2 and containing more than the steel nominal phosphorus content.

A butt joint deep penetration laser welding method is used for joining facing end sections of flat steel products, each having a carbon content CS<0.02%. In order to improve such a method such that an improved weld quality in terms of geometry and strength is achievable with it, at least one carbon-containing carrier material is inserted into a butt joint gap between the end sections, the carbon content of which is C.sub.T≥20.Math.C.sub.S, preferably C.sub.T≥100.Math.C.sub.S, and/or carbon is inserted into the butt joint gap or applied to at least one end section, such that the volume of the carbon inserted into the butt joint gap corresponds to 1% to 20% of the volume of a melt produced by a butt joint deep penetration laser welding process.

Provided a fixture for automatic assembly, overturning and welding of sidewall aluminum profile of rail vehicle, comprising a lifting mechanism, a supporting overturning device mounted on the lifting mechanism, an automatic assembling sidewall profile device mounted on the supporting overturning device, and a self-positioning locking device; the automatic assembling sidewall profile device comprises a sidewall-shaped support steel beam, and a rodless cylinder track platform and a fixing seat mounted on a top end thereof; the self-positioning locking devices are respectively mounted on the rodless cylinder track platform and the fixing seat, comprising a self-positioning base and a locking device; the self-positioning base comprises an outer housing of which the one side is provided with the locking device and inside which are provided with two symmetrically set self-positioning supports, and faces of the two self-positioning supports matching with the rail vehicle aluminum profile are provide with rollers formed a V-shaped crack.

A pre-coated steel sheet wherein at least a region at the periphery (7) of at least one (6a,6b) of the opposite faces (6a,6b) of said pre-coated sheet (1,1′) is coated with an additional coating (8) selected for increasing the vapor pressure between the pre-coating (2) and said additional coating (8) during a laser welding method up to a critical pressure at which the pre-coating (2) is ejected away from the weld (14). Preferably, the vaporization temperature of the additional coating (8) is greater than the vaporization temperature of the pre-coating (2) and the additional coating includes gammagene elements like carbon and/or nickel. A steel part obtained by laser welding, preferably butt laser welding, of at least a first and second pre-coated steel sheet (1,1′) as above indicated is also provided.

A joining method includes: an overlapping step of overlapping a front surface of a first metal member with a back surface of a second metal member; and a welding step of welding the first metal member with the second metal member by hybrid welding, using a hybrid welding machine including a leading laser welding unit and a trailing arc welding unit. In the welding step, laser welding, by irradiating with a laser beam, and arc welding are performed from a front surface of the second metal member, along a preset travel route which is set on an overlapped part formed by the first metal member and the second metal member overlapped with each other, to the overlapped part, and the laser beam is oscillated to cross the preset travel route.

The present invention relates to a pre-stressed steel sheet and a method a method of manufacturing the same.

An embodiment of the present invention provides a pre-stressed steel sheet comprising: a base material; and a plurality of weld lines formed on the base materials, wherein the average spacing between each pair of the weld lines is equal to or greater than five times the width of the weld lines and equal to or less than half the width of the steel sheet.

According to an aspect of the present invention, a pre-stressed steel sheet having improved bendability can be provided, and accordingly when the pre-stressed steel sheet is applied to a structural member such as a girder or beam, the bendability of a structure can be improved.

A method of joining a multiple member work-piece includes providing a first steel work-piece having a first thickness and a second steel work-piece having a second thickness. The first thickness is at least twice the second thickness. A third material is disposed in contact with the second steel work-piece. For example, the third material may be in the form of a rivet, a plurality of pins, or a coating material. The method includes resistance welding the first and second work-pieces together. A bonded assembly includes the first and second steel members and the third material being bonded together, where the thickness of the first member is at least twice the thickness of the second member.

A plasma ejection unit (21) of an arc welding device includes a plasma torch (26), a copper plate (27), a container (28), and a gas supplying unit (29). Plasma gas inside the container (28) is pressurized by argon gas supplied from the gas supplying unit (29), and ejected from first to eighth ejection ports. The plasma gas ejected from the first to eighth ejection ports is concentrated in a concentration area (CA) between vehicle body plates (16-17) to form through holes (40) in the vehicle body plates (16-17), and is separated. The air pressures, in eight areas, of the plasma gas reaching a vehicle body plate (18) are approximately one-eighth of the air pressure of the plasma gas in the concentration area (CA). Accordingly, while the through holes (40) are formed in the vehicle body plates (16-17), no through hole is formed in the vehicle body plate (18).

A method of laser welding a workpiece stack-up that includes at least two overlapping metal workpieces is disclosed. The method includes advancing a beam spot of a laser beam relative to a top surface of the workpiece stack-up and along a beam travel pattern to form a laser weld joint, which is comprised of resolodified composite metal workpiece material, that fusion welds the metal workpieces together. And, while the beam spot is being advanced along the beam travel pattern, between a first point and a second point, which may or may not encompass the entire beam travel pattern, at least one of the following laser beam parameters is repeatedly varied: (1) the power level of the laser beam; (2) the travel speed of the laser beam; or (3) the focal position of the laser beam relative to the top surface of the workpiece stack-up.

Provided is a fixture for automatic assembly, overturning and welding of sidewall aluminum profile of a rail vehicle, comprising a lifting mechanism, a supporting overturning device mounted on the lifting mechanism, an automatic assembling sidewall profile device mounted on the supporting overturning device, and a self-positioning locking device. The automatic assembling sidewall profile device comprises a sidewall-shaped support steel beam, and a rodless cylinder track platform and a fixing seat. The self-positioning locking devices are mounted on the rodless cylinder track platform and the fixing seat, and have a self-positioning base and a locking device. The self-positioning base comprises an outer housing is provided with the locking device and two symmetrically set self-positioning supports, and faces of the two self-positioning supports matching with the rail vehicle aluminum profile are provided with rollers having a V-shaped gap formed therebetween.