The invention relates to a method for manufacturing a sandwich panel as a semi-finished product where at least one layer of a non-metallic material is positioned between at least two metallic layers. At least one of the metal layers is shaped into a three dimensional layer, and the metal layers are in direct mechanical contact to enable resistance weldability of the semi-finished product in order to connect the semi-finished product to a desired combination of solutions in a subsequent manufacturing process.

A lap-joined structure including at least one similar metallic material weldable to each other and a different material different in type from the at least one similar metallic material and difficult to be welded to the similar metallic material. The different material is sandwiched and fixed between the similar metallic material. The similar metallic material has at least one exhaust hole or exhaust groove around the weld zone where the similar metallic material is melted and joined together. The exhaust hole or exhaust groove extends through the similar metallic material along its thickness. Thus, the similar metallic material and the different material are fixed and joined together.

The arc spot welding method for joining dissimilar materials, in which a first sheet (10) made of an Al-based material or an Mg-based material and a second sheet (20) made of ultra-high tensile steel having a tensile strength of 1180 MPa or more are joined, includes a step of forming a hole in the first sheet (10), a step of overlapping the first sheet (10) and the second sheet (20), a step of inserting a joining auxiliary member (30) made of steel, in which a hollow portion is formed, into the hole of the first sheet (10), and a step of joining the first sheet (10) and the second sheet (20) via the joining auxiliary member (30) using a welding material containing 13 mass % or more of Ni.

A junction structure includes a first metallic material, a second material different in type from the first metallic material, and a welding wire as a third material similar to the first metallic material. The second material is stacked on the first material. The molten metal of the third metallic material is deposited by arc welding into the through part of the second material so as to form a flanged or tapered bead, so that the first and third metallic materials and the second material are fixed together.

A method of welding panels overlapping each other includes a one-directional clamping step that performs one-directional clamping by positioning electrodes of a pair of one-directional spot welding guns with respect to an upper panel and a lower panel overlapping each other, a pressure welding step that forms a plurality of pressure welding portions in a zero gap status by pressure-welding the upper panel to the lower panel in a temporary welding status, by pressing and supplying electricity to the upper panel with the electrodes of the one-directional spot welding guns, plasma spot step that forms a molten portion between the pressure welding portions by performing plasma welding on the pressure welding portions with a plasma welding machine, and a cooling step that forms a welded portion by overlapping the pressure welding portions and the molten portion between the upper panel and the lower panel by cooling the molten portion.

The invention pertains to a welding apparatus, particularly to a spot sa welding apparatus which utilizes a single welding electrode/torch to weld vertically adjacent metallic sheets or plates together. The apparatus comprises a MAG welding apparatus with a welding torch and shielding inert or semi-inert gases gas source configured to protect the welded working place, an apparatus for creating holes in at least one of the welded metallic sheets and at least one frame part for assembling the MAG welding apparatus and apparatus for creating holes.