| 摘要 |
PURPOSE:To manufacture inexpensively an electric welded steel pipe with high squeezing strength by drawing an open pipe through a fin pass at a high overall drawing rate in a draw forming process. CONSTITUTION:After being sized and straightened in a draw forming process, an open pipe is drawn through a fin pass at an overall drawing rate of 1.0- 4.0%, and its residual stress is reduced to obtain an electric welded steel pipe having high squeezing strength without performing its heat treatment. Further, the manufacturing cost of the pipe is remarkably reduced by eliminating the heat treatment. The residual stress increases sharply when said overall drawing rate is less than 1%, and when the rate exceeds 4% it begins to increase resulting the generation of roll marks in the open pipe, then the rate is limited as mentioned above. |
