Nippon Kokan Kabushiki Kaisha

Toshifumi Kojima

Itaru Watanabe

Jinkichi Tanaka

Motoaki Suzuki

Fusao Koshiga

Tatsumi Osuka

Kenji Takeshige

Osamu Hirano

Hiroyoshi Matsubara

Takashi Nagamine

Hiroshi Kagechika

Yasuhiro Ueno

Shigeyoshi Kosuge

Insert 1 comprises thin substrate made by cold-rolling, and two bonding alloy layers formed by plating on the upper and lower surfaces of substrate, respectively. Both layers is extremely thin, and is made of an alloy having a melting point lower than that of substrate. Insert 1 is used to achieve liquid phase diffusion bonding of first and second base metals. Insert 1 is interposed between first base metal and second base metal. Then, insert 1 and base metals are clamped together with a pressure of, for example, 0.5 kgf/mm.sup.2, and are placed in a atmosphere of a low pressure of about 10.sup.-4 Torr and heated to the melting point of alloy layers or to a temperature above this melting point but below the melting points of substrate and plates.

Method of liquid phase diffusion bonding of metal bodies

In longitudinally seam-welding a pipe-blank for welded steel pipe from the inside along a groove by the GMA welding process which comprises using direct electric current supplied to a plurality of consumable electrodes in tandem through at least one cable as the welding current, at least two even-numbered consumable electrodes are used, half of said consumable electrodes being connected to said direct current so as to be positive in polarity and the remaining half of said consumable electrodes being connected to said direct current so as to be negative in polarity, to enable lines of magnetic force produced by said direct electric current for welding flowing through said at least one cable introduced into said pipe-blank to cancel each other, thereby preventing magnetization of said pipe-blank and the resulting magnetic arc blow of the welding arc.

Preventing magnetization of pipe blank in GMA welding

In longitudinally seam-welding a pipe-blank for welded steel pipe from the inside along a groove by the reverse-polarity GMA welding process comprising using direct electric current supplied to a consumable electrode through a cable as the welding current with said consumable electrode as the anode, the direction of said direct electric current for welding flowing through said cable introduced into said pipe-blank is set in the same direction as that of welding, thereby preventing occurrence of a magnetic arc blow of the welding arc from said consumable electrode toward the upstream side of the welding direction, i.e., in the opposite direction to that of welding.

Method for longitudinally seam-welding pipe-blank for welded steel pipe

After longitudinally seam-welding a pipe-blank for welded steel pipe from the inside along a groove by the arc welding process which comprises using direct electric current supplied to a consumable electrode through a cable as the welding current, the polarity of said consumable electrode applied for said longitudinal seam-welding is switched over to the opposite polarity, an arc from said consumable electrode is ignited again on a tab plate attached to the end of said pipe-blank on the completion side of said longitudinal seam-welding to cause a direct electric current for eliminating magnetism to flow through said cable in the opposite direction to that of said direct electric current for welding, thereby eliminating residual magnetism in said pipe-blank produced by said direct electric current for welding flowing through said cable introduced into said pipe-blank during said longitudinal seam-welding.

Method for eliminating residual magnetism in pipe-blank for welded steel

Growing community of inventors

Yokohama, Japan

Toshifumi Kojima