Daido Tokushuko Kabushiki Kaisha

Ryuzo Yamada

Takao Shimizu

Hirotsugu Horio

Shigeyuki Inagaki

Kazushige Kito

Toshio Endo

Tomikazu Yagi

Kazushige Kitou

Taizo Yano

Nobuo Ishikawa

In diffusion bonding a metal pipe and a metal pipe via a bonded interface formed at the end parts, a portion that is inclined with respect to the radial direction of metal pipes and is provided at least at part of bonded interface In this case, the inclination angle &phgr; of bonded interface and the tip angle 2&thgr; of a pipe expansion tool are preferably in the relationship, 0<&phgr;&lE;&thgr;&plus;60&deg;. In performing pipe expansion of such a metal pipe bonded body the pipe expansion tool is moved from the metal pipe at which the inclined portion of junction face is formed to have a protruding shape, towards the metal pipe at which the inclined portion of junction face is formed to have a recessed shape. Furthermore, the inner diameter at the vicinity of the junction face of the metal pipe junction may be made larger than the inner diameter at positions away from the junction face.

Metal-pipe bonded body, pipe expansion method of metal-pipe bonded body, and method for inspecting metal-pipe bonded body

Carbon steel pipes are joined to each other in a non-oxidizing atmosphere by using an insert constituted by a Ni-base alloy or a Fe-base alloy having a melting point which is lower than 1200&deg; C. and a thickness of 80 mm or smaller under conditions that the surface roughness Rmax of the joined surfaces of the carbon steel pipes is 20 &mgr;m or smaller, the joining temperature is not lower than 1250&deg; C. nor higher than 1330&deg; C., duration at the joining temperature is 30 seconds or longer and the pressure is not lower than 2 MPa nor higher than 4 MPa. The expanding operation is performed such that the maximum difference in level of the joined portion is not larger than 25% of the carbon steel pipe and the expansion ratio is 25% or lower.

Method for manufacturing joint of carbon steel pipes suitable for expansion and expanding method

A method for evaluating bonding properties of a metallic pipe, the method comprises steps of measuring, in advance of a pipe expansion operation, at least one selected from a degree of shape discontinuity, a degree of defect at a bonding portion, and a degree of change in crystal structure, and comparing a measurement value with a predetermined threshold value to evaluate suitability of the bonding properties for applying pipe expansion.

Method for evaluating bonding properties of a metallic pipe

The surface of the member to be inspected is covered with powder deposited by using, for example, static electricity prior to the flaw detection. The member surface is covered so as to be partly exposed by setting the average thickness of the powder layer to 0.1D-0.6D, where D is the average particle diameter of the powder, under an assumption that the powder particles in the powder layer are virtually leveled into a uniform thickness film. Subsequently, the surface region of the member is heated by high frequency induction heating, and then the temperature distribution on the surface is measured with a radiation thermometer. The part for which the temperature measured is different from the surroundings is judged as a flaw. The surface of the member is covered with the powder so that the surface emissivity becomes almost uniform, and the resulting temperature distribution measured with the radiation thermometer becomes almost equal to the real one. Therefore, flaws existing on the surface of the member are precisely detected according to the measurement with the radiation thermometer even in the case that there are parts of low emissivity, such as handling marks, on the surface.

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Nagoya, Japan

Ryuzo Yamada