| 摘要 |
PURPOSE:To improve the quality of an electric resistance welded tube by composing the side shape from the bottom surface of a roll to its upper flange of continuity of a straight part and a circular arc part in the side roll of a breakdown area. CONSTITUTION:For one or more side rolls 2 in the breakdown area, the side shape is composed of a continuity of a straight part and a circular arc part. The side shape from the bottom surface 27 of the roll to the midway is made up of a straight line 25 making a sharp angle to the bottom surface 27 of the roll and the side from the terminal point of the straight part to the upper flange 28 is made up of a circular arc 26. The edge of a curved material carried in from an upper stream stand comes in strong contact with the straight part 25, and is compressed forcedly by the upper circular arc part 26 to increase the thickness of the edge. In this way, since the reduced thickness part of the material is modified and increased, the electric resistance welded tube is equalized and improved in quality.
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