PURPOSE: To make the cut off quantity of crop to be almost zero by rolling only pipe ends, having large wall thickness each, after stretch reducing a pipe stock, and finishing the pipe ends into the prescribed outer diameter and wall thickness in the longitudinal direction.
CONSTITUTION: In a mill, three (or two) rolls 1, 2, 3 are arranged around a plug 5, and the whole body of a box for retaining the rolls 1, 2, 3 is revolved. Further, mills 9, 10 for respectively subjecting the front and rear ends of a pipe to rolling reduction, are arranged at both sides of a cooling bed 8 located at the back of a stretch reducer 7. A material 11 delivered from the stretch reducer 7 advances toward the bed 8 to subject first its front end to rolling reduction by the mill 9, and then retreats to subject its rear end to rolling reduction by the mill 10. In this way, the wall thicknesses at both ends of pipe are made equal to the dimensions at its central part, to make the cut off quantity of crop to be almost zero and improve material yield.
MASUDA ICHIROU
UCHIDA HIDE
TOKITA HIDENORI
