Sumitomo Metal Industries, Inc.

Kawasaki Jukogyo Kabushiki Kaisha

Sumikin Stainless Steel Tube Co., Ltd.

Munekatsu Furugen

Shigetomo Matsui

Hiroyuki Matsumura

Hisahiko Miyazaki

Kazuhiro Ogawa

Masanari Kimoto

Kunihiro Fukui

Takao Taka

Hisao Hasegawa

Koji Kadota

Hiroshi Okamoto

Shotaro Hamazaki

Toshio Tsuta

Hiromichi Nakamura

Yoichi Imamura

Tetsuro Noma

Hajimu Choba

Atsushi Satoh

Jun-ichi Uchida

Atsuhumi Okamoto

Norimasa Kameoka

Stainless steel pipe of bright annealing finish type, having

A method of manufacturing hollow steel bars comprising the steps of preparing a hollow billet with the dimensions meeting a condition expressed by the following formula (1) by piercing a steel billet with a piercer after heating, inserting a mandrel as an inner surface sizing tool into a hollow billet, and then rolling the hollow billet on a cross-rolling mill having three rolls arranged around a pass line to provide plastic working for reduction of the outside diameter and adjustment of the wall thickness of the hollow billet so as to meet a condition expressed by the following formula (2), and a manufacturing apparatus comprising an electric resistance heating unit, the piercer, and the cross-rolling mill, wherein

Method and apparatus for manufacturing hollow steel bars

Clad pipe having an inner pipe and an outer pipe metallurgically bonded to each other is manufactured by a process comprising the steps of: (a) preparing an inner pipe and an outer pipe made of different metallic materials, the outer pipe having an inner diameter larger than the outer diameter of the inner pipe; (b) forming an Ni-B layer by electroplating or electroless plating on the surface of one of the pipes facing the other pipe when the two pipes are assembled, the Ni-B layer having a thickness of 2-100 .mu.m and consisting essentially, on a weight basis, of B: 0.5%-7%, Fe: 0%-30%, P: 0%-7%, and a balance of Ni and inevitable impurities; (c) assembling the two pipes by inserting the inner pipe into the outer pipe; (d) subjecting the assembled pipes to cold working for reduction in diameter to such a degree that the outer diameter of the inner pipe is reduced by from 0.5% to 10% to form raw clad pipe in which the inner and outer pipes are in contact; and (e) subjecting the raw clad pipe to heat treatment in the temperature range of 1050.degree.-1250.degree. C. for a time sufficient to metallurgically bond the inner and outer pipes by diffusion bonding.

Process for manufacturing clad pipe

A method of manufacturing a long tube having a small diameter, such as a tube for use in a heat exchanger, by cold working. A plug drawing using a pressurized lubricating oil of 500 kgf/cm.sup.2 or more accompanied by the reduction in wall-thickness is adopted as at least the final cold work. In the case where a tube having desired dimensions is not obtained by this plug drawing, subsequent free-loaded drawing can be conducted.

Long tube having a small diameter

Method of manufacturing long tubes having small diameters

An apparatus for continuous production of seam-welded steel tubing is proposed. The apparatus includes a series of shaping rolls for shaping a strip taken out from a strip coil into a tubular intermediate product, the roll series including a finpass roll group. The tubular product is subjected to seam welding under the action of a seam welder. Before arrival at the welder, a substantial main part of the preformed tubing with exception of opposing edge zones thereof is subjected to heating by a heater compensate for excess compressive stresses induced in the edge zones, while these zones are subjected to cooling by a cooler for avoiding otherwise formation of disadvantageous edge wavings which would otherwise occur.

Method of and apparatus for continuous production of seam-welded metal

A process of continuous production of seam-welded steel tubing is concerned. A steel strip is taken out from a strip coil and conveyed to a tube-preshaping step including a plural of shaping roll stand positions. In the preshaping step, the strip is laterally rounded up gradually from band strip to a rough-shaped tubing until the side edges are brought into a mutually abutting state ready for seam-welding. The preshaping step is divided into a plurality of local regions. In these local regions, substantially body portion with exception of corresponding marginal edge zones of the tubing stock is separately subjected to heating. The heating width and heating intensity at these regions are increased stepwise as the tubular stock advances from upstream to downstream for avoiding conventionally appearing edge wavings and buckling undulations in the material of the steel tubing.

Continuous production of seam-welded metal tubing

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Amagasaki, Japan

Munekatsu Furugen