PURPOSE: To prevent flaring in a joint part in a device for gas pressure welding of a steel pipe by providing a means for absorbing the allowance for thermal expansion of the steel pipe by heating between a clamp on a moving side and a hydraulic cylinder for upsetting.
CONSTITUTION: A spring 25 and a seat 28 to be attached with a strap 26 are provided on the rear of a clamp 5 which moves along a clamp body 22 in order to absorb the allowance for thermal expansion of a steel pipe by heating in the stage of clamping the steel pipe to a gas pressure welding device and heating the joint part by a burner. The pre-load by the spring 25 is exerted between the strap 26 and the seat 28 apart at a distance (l) corresponding to the allowance for thermal expansion. On the other hand, the stroke of a hydraulic cylinder 6 for upsetting is so adjusted as to coincide with the extent of upsetting and the cylinder 6 is advanced by a nut 24 until the cylinder collides against the strip 26, when the cylinder is stopped. The distance (l) is narrowed to 0 in the stage of heating. Flaring during joining of the steel pipe is thus prevented.
TACHIKAWA HIROSHI
UMADA TOYOAKI
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