| 摘要 |
PURPOSE:To reduce remarkably welding defects and to increase product yield by rolling with the specified rolling reduction quantity by rolling roll with forming a forming part on the center part of flange material and by welding a web material with forming a bulging part. CONSTITUTION:A flat projecting part 11 is formed on the center part of a flange material 1 by rolling with the rolling reduction of 3-20% of the plate thickness of the flange 1 by rolls 13, 32. A high frequency welding is performed by butting to the flat projecting part 11 of the flange 1 the end part of the web material 2 without performing any working thereon. By forming a bulging part on the weld zone of the flange like this a high frequency current is concentrated on the forming part 11 and the part thereof is heated at higher temp. compared with others.
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