JPS5779007A - Reducing mill train for round pipe - Google Patents

Abstract

PURPOSE:To inexpensively manufacture various reduced pipe products with good productivity, by dividing a serial rolling mill train into an optional number of blocks comprising plural rolling stands correspondingly to the reducing amount for the pipe diameter, and by making the phase of angular arrangement of roll axes in each block variable. CONSTITUTION:Between the blocks 1, 2 of a rolling mill train comprising plural, #1-#28 for example, rolling stands respectively provided with plural, three for example, rolls, the angle (phase of angular arrangement of the roll) of the roll axes in a plane vertical to the rolling direction of the roll is shifted by 30 deg., for example. After a reducing pass for reducing the pipe diameter from 180mm. to 34mm., if the next pass is scheduled to reduce the pipe diameter from 180mm. to 60mm., it is judged, for instance, that the reducing pass has to be performed by rolling stands from #1 to #20. In this case, six rolling stands #15-#20 are not capable of sufficiently restraining the squaring phenomenon of the inner surface of te round pipe. Then, the phase of angular arrangement of roll axes of four rolling stands #11-#14 is shifted by 30 deg., and the block 2 is constituted of rolling stands #11-#20 for performing a scheduled diameter reducing rolling pass.