| 摘要 |
The curved shape of square or circle type steel pipe is produced by placing an electric heater(4) and liquid paraffin(5) in a straight steel pipe, inserting air bags(1,1a) on both ends of a pipe, solidification of liquid paraffin, bending of straight pipe, liquefaction and removing of solid paraffin(5a) by electric heaters(4,4a,4b). The curved pipe has a clear and correct size by minimization of the inner diameter change during bending.
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