JPS5626606A - Preventing method for overlap in sizing machine for seamless steel pipe - Google Patents

Abstract

PURPOSE: To prevent the titled overlap, by making the wall thickness of the pipe blank to be fed to the reeling mill to be gradually increased from the heat to the tail, by holding constant the rolling load of the reeling mill, and by making the outer diameter of the pipe blank after passing the reeling mill to be almost constant in the axial direction.

CONSTITUTION: Since the temperature of the pipe blank to be fed to the reeling mill is higher at the tail than at the head, the deformation resistance decreases from the head to the tail. However, if the wall thickness of the pipe blank is increased from the head to the tail and the reeling work is performed under a constant rolling load, the wall thickness is reduced as much as the increment in the wall thickness. Accordingly, even if the deformation resistance is small, the total deformation work increases; as a result, the power to be supplied to the deformation work increases. Hereby, the reduction of the deformation resistance is compensated, and almost uniform outer diameter is obtained from the reeling work under the constant rolling load. Meanwhile, said gradual increase of the wall thickness in the pipe blank can be obtained by rolling with the plug mill while controlling the gap of upper and lower rolls so as to be gradually increased.

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