Metal fusion bonding – Process – Diffusion type
Patent
1996-08-06
1999-03-02
Heinrich, Samuel M.
Metal fusion bonding
Process
Diffusion type
228265, 2852889, 28528811, B23K 3102, B23K10104
Patent
active
058759549
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a bonded pipe produced by butting end faces of pipes against each other so as to be bonded, and to a method of bonding the pipes by the liquid phase diffusion bonding process.
DESCRIPTION OF RELATED ART
Heretofore, there has been known the liquid phase diffusion bonding process as a method of butting and bonding end faces of materials such as steel bars and steel pipes in which an insert material such as an amorphous metal lower in melting point than materials to be bonded is interposed between end faces to be bonded, and the end faces are butted; the butted portion is heated to be raised in temperature higher than the melting point of the insert material, for example, about 1100.degree.-1300.degree. C. (depending on the melting point of the insert material); and then the portion is kept at the temperature for a predetermined time so that the element of the melted insert material is diffused into the material to be bonded, thereby bonding the pipes to each other. Compared with the gas pressure welding process, this liquid phase diffusion bonding process performs bonding at a lower working temperature and at a smaller applied pressure, so that the method is characterized in that a secure bonding is performed without involving a large deformation in the bonded portion.
Generally in the liquid phase diffusion bonding process, the butted portion is heated in a state that an initial load is applied to the portion, and when a specified temperature is reached so that the element of the insert material is diffused, the load applied to the butted portion is allowed to be lowered, thereby preventing an excessive deformation. However, also in the liquid phase diffusion bonding process, when utilized for the connection of line steels such as steel bars, it may be desirable that a large pressure is applied to the bars in the axial direction in order to prevent an mismatch, so that the bars are compressed, thereby increasing the thickness of the butted portion. It is considered that increasing the butted portion needs to apply an compression force larger than the initial load when a specified temperature for the liquid phase diffusion bonding is reached at which the butted portion is in a plastic deformation-prone state.
Then, the application of this process to the solid material such as steel bars caused the periphery of the butted portion to develop an increased thickness. This allowed the contact of the end faces with each other to become secure, and the scraping/finishing to be performed without developing an insufficient wall thickness, thereby eliminating a dislocation.
As a method of increasing thickness securely, there have been proposed a method of making larger initial load than prior art (Japanese Patent Application Laid-Open No. 2-75478 (1990), Japanese Patent Application Laid-Open No. 3-71950 (1991)), a method of making larger initial load and performing arc welding at temperature higher than melting point of insert material (Japanese Patent Application Laid-Open No. 5-220585 (1993)), and a method of making larger initial load and applying further pressure during holding temperature after specified temperature is reached (Japanese Patent Application Laid-Open No. 6-277859 (1994)).
On the other hand, for the bonding of steel pipes, it is an essential subject that the rupture strength of the butted portion (hereinafter called the joint strength) is made larger than the rupture strength of the base metal of steel pipes (hereinafter called the base metal strength). In order to increase the joint strength by increasing bonding area on the butted portion, the present inventors tried to bond steel pipes by the use of the above-mentioned method of increasing thickness of steel bars, that is, a method in which a large compression force is applied to the steel pipes when a specified temperature for the liquid phase diffusion bonding is reached at which the butted portion is in a plastic deformation-prone state. Contrary to expectations, as shown in FIG. 1, i
REFERENCES:
patent: 647468 (1900-04-01), Brown et al.
patent: 3149415 (1964-09-01), Hyver
Kishi Shinsuke
Maenosono Tsukasa
Sato Michio
Heinrich Samuel M.
Sumitomo Metal Industries Ltd.
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