Abstract: A clad steel pipe excellent in corrosion resistance and low-temperature toughness, which comprises a cladding sheet of high corrosion resistant steel and a substrate sheet of low-alloy high-strength steel, the substrate sheet consisting, as the fundamental constituents, essentially of:carbon: from 0.002 to 0.050 wt. %,silicon: from 0.05 to 0.80 wt. %,manganese: from 0.80 to 2.20 wt. %,niobium: from 0.01 to 0.10 wt. %,aluminum: from 0.01 to 0.08 wt. %,nitrogen: from 0.002 to 0.008 wt. %, and,the balance being iron and incidental impurities;or, the substrate sheet further additionally containing, as the strength-improving constituents, at least one element selected from the group consisting of:copper: from 0.05 to 1.00 wt. %,nickel: from 0.05 to 3.00 wt. %,chromium: from 0.05 to 1.00 wt. %,molybdenum: from 0.03 to 0.80 wt. %,vanadium: from 0.01 to 0.10 wt. %, and,boron: from 0.0003 to 0.0030 wt.

Abstract: For producing steel pipe from thick steel plate, an up-set shrinker is employed for reducing and processing an O-shaped pipe-blank in a facility for producing thick wall steel pipe. The up-set shrinker is provided with a plurality of reducing shrinker dies located around the pipe-blank in correspondence to parts other than abutting parts of the edges of the pipe-blank, and with at least one edge processing shrinker die located in correspondence to the butting parts of the edges of the pipe-blank. The edge processing shrinker die is formed at its die surface with a projecting portion over the length of the die. The edge processing shrinker die is actuated independently of the reducing shrinker dies.

Abstract: For producing steel pipe from thick steel plate, a foreign member is arranged on a die at the center of its caliber in the length thereof such that the member meets the edge groove of the steel, and in such a condition O-ing is carried out thereon, thereby to produce a thick welded pipe having very little the peaking amount.

Abstract: Circular pipe of large diameter progressively formed of flat stock, the pipe having a single longitudinal seam is seam-welded by preparing welding grooves such that the inner groove is smaller in size and angle than the outer groove, sequentially carrying out submerged arc welding on the inner welding groove, and large current MIG welding to then first layer of the outer welding edge and a submerged arc welding to a second layer thereof.

Abstract: An arc welding method for manufacture of a welded steel pipe wherein the edges of a steel plate bent into a pipe shape are welded together on one side for forming a pipe and then the seam line of the thus formed pipe is welded by a second welding operation at the side opposite to the side where the first welding was performed. During such second welding, the weld is cooled forcedly from the side where the first welding was performed. Such forced cooling compensates for any physical effects accompanying the welding and imparts elevated toughness to both the weld metal and the heat affected zone.