Abstract: A method of spot welding aluminum alloy workpieces having electrical conductivity of 18.about.57% IACS and Vickers hardness of 26.about.200 is disclosed. The aluminum alloy workpieces are spot welded by a pair of welding electrodes having an electrical conductivity of not less than 92% IACS and a Vickers hardness of 50.about.130. The differences of the electrical conductivity and Vickers hardness between the welding electrodes and the aluminum alloy workpieces are in a range of 41.about.87% IACS and not larger than 99, respectively.

Abstract: A multilayer plated aluminum sheet suitable for use in automobile body panels comprises a base aluminum sheet made of aluminum or an aluminum alloy and has a first layer of zinc or a zinc alloy formed by displacement plating on the surface of the aluminum sheet and one or more layers of electroplated coating formed on the first layer by electroplating in an acidic bath. Preferably, the upper electroplated coating comprises at least one layer of zinc or a zinc alloy and the uppermost layer of the coating is formed from a metallic material having a melting point above 500.degree. C.

Abstract: A spot welding electrode is made of a copper base material such as copper, copper alloy, or alumina dispersion strengthened copper, and has a Sn coating layer formed at the part making contact with the material being welded. The formed Sn coating layer reduces electrode wear and prolongs electrode life.

Abstract: A vacuum-brazing aluminum cladding material consisting of a core member and a first and a second clad which cover at least one surface of the core member. The first clad consists of 6-14% by weight of Si, 0-0.6% by weight of Mg and the balance being at least Al, and the second clad formed on the first clad consists of 0-14% by weight of Si, 0.8-2.5% by weight of Mg and the balancing being at least Al. The second clad has a thickness of at least 5"m, and this thickness and a content of Si determined so as to satisfy a formula t.ltoreq..vertline.100/(10-c).vertline., wherein, "t" is the thickness (.mu.m) of said second alloy clad, and "c" is the content (% by weight) os Si of the second clad.

Abstract: A process of fixing a double-walled tubing structure to a titanium tube sheet, the tubing structure comprising a non-titanium outer tube and a titanium inner lining tube, comprising the steps of: pressure-welding a titanium collar to an end face of the outer tube to form an integral titanium end portion at one end of the outer tube; inserting the titanium lining tube in the outer tube and fixing the titanium lining tube to the outer tube in pressed contact with the inner surface of the outer tube to form the titanium-lined double-walled tubing structure; and inserting an end section of the tubing structure in a hole in the tube sheet, and welding the titanium end portion of the outer tube and an end portion of the lining tube to the tube sheet. Instead of the titanium collar being directly welded to the outer tube, an auxiliary collar made of a metal material for sound welding to the outer tube may be pressure-welded at its one end to the titanium collar, and fusion-welded at the other end to the outer tube.