Sumitomo Metal Industries, Inc.

Nippon Steel Sumitomo Metal Corporation

Sumitomo Pipe & Tube Co., Ltd.

Tatsuya Okui

Kouichi Kuroda

Masayoshi Akiyama

Koichi Kuroda

Tetsuo Yokoyama

Takashi Nakashima

Takuya Hanada

Tsutomu Arita

Tadashi Kawakami

Provided is a method for producing a double-wall tube with braided wires at its interface in which the braided wires are interposed between an outer-wall and inner-wall blank tubes and then a drawing process is applied so as for the braided wires to be brought into close contact with the inner surface of the outer-wall tube and the outer surface of the inner-wall tube, the method comprising: polishing the inner surface of the outer-wall blank tube and the outer surface of the inner-wall blank tube so that a surface roughness thereof satisfies Ra&#x3c;1.0 &#x3bc;m, followed by interposing the braided wires between the outer-wall and inner-wall blank tubes; performing a sinking drawing process so that the difference of the outer diameter of the resulting double-wall tube relative to a die bore diameter is 0.1 mm to 0.3 mm; and subsequently performing heat treatment. The double-wall tube produced is suitable as a heat-transfer tube.

Method for producing double-wall tube with braided wires at its interface

A reducing mill includes a plurality of stands disposed along a rolling direction line. The stands each include n rolls (n&#x2267;3) disposed around the rolling direction line, the n rolls are shifted by 180&#xb0;/n around the rolling direction line from n rolls included in a preceding stand. The n rolls included in each of the stands excluding the last stand each have a groove having an arch shape. The bottom of the groove has a circular arc shape around the rolling direction line having a first radius in cross section. The distance between the surface of a roll flange portion between the bottom and the edge of the groove and the rolling direction line is longer than the first radius. The distance between the edge of the groove and the rolling direction line is longer than the first radius in the groove of a roll included in the preceding stand.

Pipe or tube reducing mill and roll for reducing mill

The plug is for expanding the inside diameter of the end portion of a metal pipe. Its cross section is a circle, and includes a taper portion and a parallel portion connected to the tail end of the taper portion. The diameter of the taper portion gradually increases from the head end of the taper portion to the tail end of the taper portion where the diameter is D. The axial distance LR from the point where the diameter D=D&#xd7;0.99 to the tail end where the diameter is Dsatisfies the Expression 22&#x2266;LR/((D&#x2212;D)/2)&#x2266;115. The taper angle on the surface where the diameter is Dis larger than or equal to the taper angle on the tail surface of the taper portion following the point where the diameter is D. The diameter of the parallel portion is D

Plug, method of expanding inside diameter of metal pipe or tube using such plug, method of manufacturing metal pipe or tube, and metal pipe or tube

A plugincludes a first columnar portion, a tapered portion, and a second columnar portion. The first columnar portionhas an outside diameter D. The second columnar portionhas an outside diameter Dwhich is larger than the outside diameter D. The tapered portionis formed between the first columnar portionand the second columnar portion. The tapered portionhas a tapered surfaceprovided with an outside diameter which is gradually increased from the first columnar portionto the second columnar portion, and an axial direction length L. The outside diameters Dand D, and the axial direction length L meet the following expressions (1) to (4):0.25&#x2266;&#x3c1;&#x2266;2.00&#x2003;&#x2003;(1),0.06&#x2266;2&#x2266;0.8&#x2003;&#x2003;(2),2&#x2266;0.3&#xd7;&#x3c1;+0.575&#x2003;&#x2003;(3), and2&#x2267;0.1&#xd7;&#x3c1;&#x2003;&#x2003;(4)where &#x3c1;=(2&#x2212;1)/1&#xd7;100.Therefore, the cold drawing plug according to the present invention can reduce the tensile residual stress on the outer surface of a metal pipe after the cold drawing.

Plug for cold drawing and method for manufacturing of metal pipe

An apparatus for sizing a pipe end comprising: a plugfor sizing the pipe end; a chuckfor clamping the pipe; and shifting means for shifting the position of the plugand/the chuck, which are placed successively from the end of the pipe, and the plughas a circular cross section, and is constituted by a taper portionand a diameter equivalent portioncontinuously formed from the tip of the plug in succession. The outer diameter of the taper portionis gradually expanding from the tip toward the rear end while satisfying the following formulas (1) and (2). The chuckis capable of changing clamping position of the pipe. This apparatus makes it possible to size the inner diameter of a pipe end with superior dimensional precision/()&#x2266;&#x2003;&#x2003;(1)RR&#x2003;&#x2003;(2).

Apparatus for pipe end sizing and method for pipe end sizing

The present invention provides a mechanical pipe-end expander comprising a cone and a die having tapered wedge bodies whose outer radius is larger towards a flangeless end direction from a flange end, wherein a pipe-end zone is expanded by a wedge effect of the die, which results from a procedure that the cone and the die are inserted together into the pipe-end zone to be expanded, and that then only the cone is axially drawn outwards leaving the die within the pipe-end zone. A seamless steel pipe with an expanded pipe-end zone is manufactured by applying a mechanical pipe-end expander comprising a die having tapered wedge bodies whose outer radius is larger towards a flangeless end direction from a flange end. The resulting seamless steel pipe has satisfactory pipe-end dimensional accuracy, and exhibits characteristics with excellent field welding workability.

Mechanical pipe-end expander and a method of manufacturing seamless steel pipe

A die through hole has an inside surface including a bell portion, an approach portion, and a bearing portion from the entrance side. The diameter of the approach portion is Don its entrance side and Don its exit side and gradually decreases from the entrance side to the exit side. The diameter satisfies Equation (1): 0.7&#x2266;D/D&#x3c;0.97. The die half angle of an inside surface where the diameter Dis D/0.97 is not less than the die half angle Rof an inside surface nearer to the approach portion exit side than the inside surface where the diameter is D. The axial distance LR from the inside surface where the diameter is Dto the inside surface where the diameter is Dsatisfies Equation (2): 20&#x2266;LR/((D&#x2212;D)/2)&#x2266;115. The through hole diameter at the bearing portion is fixed at D, and the length is LB and satisfies Equation (3): 0.3&#x2266;LB/D&#x2266;10.

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Osaka, Japan

Tatsuya Okui