| 摘要 |
PURPOSE:To prevent a crack from occurring on a flange when it is fabricated by interposing an aluminum sheet between a steel board and an aluminum bearing board and pressing them with a roll to reduce the hardness. CONSTITUTION:An aluminum bearing alloy is shaped in the flat board form. An aluminum board is interposed between the flat board and a steel board and bonded thereto with an alloy pressing rate approximately between 35-40%. The hardness of said steel board is approximately Hv160-190. A three-layer composite board of a roll board consisting of a steel back metal layer of the steel board, an aluminum medium layer of aluminum bearing alloy board, and an aluminum surface layer thereof is bent in the cylindrical or the semi- cylindrical form. The composite board has a low hardness, on account of which when said board is flanged, there is no evidence of a crack on the flange part.
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