Metal fusion bonding – Seam backup means
Patent
1994-08-03
1995-09-12
Heinrich, Samuel M.
Metal fusion bonding
Seam backup means
228 46, B23K 3702
Patent
active
054491070
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a weld backing that is held against the underside of a workpiece to provide adequate weld-metal support in full penetration welding and more particularly, to a weld backing suited for use with a movable backing positioning system.
BACKGROUND ART
In prior art full penetration welding using a backing material, the following procedures are usually taken. Firstly, a weld backing is formed from copper or a copper alloy with its length being identical to the length of the weld line of a workpiece to be welded and its configuration fitting to the shape of the weld line. Such a weld backing is held against the underside of the weld zone where a groove is formed and is fixed in position being supported by a number of supporting members. In this condition, a welding machine is moved along the weld line to weld throughout the entire length of the weld line. After completion of welding, the weld backing as well as its supporting members are removed.
However, the conventional weld backing made from copper or a copper alloy suffers from the following disadvantages: (1) the weld backing is too soft and therefore liable to wear; and (2) the penetration bead tends to stick to the weld backing in high temperature zones. For these reasons, the conventional weld backing is not reusable and cannot withstand long service. The present invention has been made in order to overcome such disadvantages and therefore an object of the invention is to provide a weld backing which is repeatedly usable in full penetration welding and can withstand long service.
DISCLOSURE OF THE INVENTION
The above and other objects can be achieved by a weld backing according to the invention which is held against the underside of a workpiece to provide weld-metal support in full penetration welding, the weld backing comprising: a substrate made from copper or a copper alloy; and a copper-aluminum alloy layer containing 9 to 23% by weight of aluminum and formed at least on the surface of the substrate, the surface being on the side which faces a weld zone.
By forming the copper-aluminum alloy layer which contains 9 to 23% by weight of aluminum and is highly abrasion-resistant, on the substrate made from copper or a copper alloy, the abrasion resistance of the surface of the weld backing can be highly improved. Further, since the copper-aluminum alloy has bad affinity to a bead, the penetration bead does not stick to the surface of the weld backing and therefore the smoothness of the backing surface can be ensured. These characteristics enable the weld backing to be reused and to be used for a long period.
The copper-aluminum alloy layer contains 9 to 23% by weight of aluminum, for the reason that when the aluminum content is less than 9% by weight, satisfactory hardness cannot be obtained and when it exceeds 23% by weight, the weld backing becomes too brittle for practical use although the hardness obtained is satisfactory. The preferable aluminum content is in the range of 16 to 22% by weight. When the content falls in this range, the copper-aluminum alloy layer is not brittle but possesses high hardness. The hardness of the copper-aluminum alloy layer is preferably 250 to 700 mHv in practice and its thickness is preferably 20 to 300 .mu.m.
The weld backing may include a cooling means for cooling the copper-aluminum alloy layer. By cooling the copper-aluminum alloy layer with the cooling means, the solidification of a penetration bead maintained by surface tension can be speeded up and the resistance to abrasion and adherence at the surface of the weld backing can be markedly improved. The cooling means may be a cooling medium that is circulated or stored within an interior space of the weld backing.
In a preferable form, the weld backing is made from copper or a copper alloy, and the copper-aluminum alloy layer is formed on the substrate made from the copper or copper alloy, and the cooling medium serving as the cooling means for cooling the copper-aluminum alloy layer is circulated or stored withi
REFERENCES:
patent: 433589 (1890-08-01), Adams
patent: 1922324 (1933-08-01), Price et al.
patent: 4874439 (1989-10-01), Akutsu
Iwasaki Akio
Kimura Yuichi
Masamura Akitoshi
Oishi Tatsuya
Umeno Kenji
Heinrich Samuel M.
Kabushiki Kaisha Komatsu Seisakusho
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