| 摘要 |
PURPOSE:To decrease the number of heating and to prevent generation of defects by inserting a sacrifical pipe into a pipe material then inserting a mandrel into the sacrificial pipe and subjecting the pipe to hollow forging. CONSTITUTION:A sacrificial pipe 5 is inserted into a pipe material 1 and the material 1 is heated to an optimum hot working temp. region. While the pipe 5 is held inserted into the material 1, a mandrel 4 is inserted into the pipe 5 and load is exerted to an upper anvil 2 to forge the material 1. The material 1 is drawn together with the pipe 5. The pipe 5 is gas-cut after forging and the drawn pipe product is obtd. The inside surface of the material 1 is held covered by the heated pipe 5 during working and therefore the heat radiation from the material to the mandrel 4 is considerably decreased, by which the number of heating the material 1 is decreased and the generation of defects such as crack, etc. during working is prevented as well.
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