METHOD AND APPARATUS FOR STRETCH REDUCING METALLIC TUBE

PROBLEM TO BE SOLVED: To reduce inside angularity which is generated in stretch reducing used in the sizing stage of a metallic tube to a degree that it is practically no problem without remarkably increasing the number of combinations of roll arrangement than that of an ordinary stretch reducer train. SOLUTION: A stretch reducing method of the metallic tube or an apparatus for realizing it is characterized in that in stretch reducing of the metallic tube using a rolling mill constituted so that a plurality of stands comprising three rolls are continuously arranged, the phase difference in the roll arrangement between respective stands is taken as a second kind of phase difference in only one place and others are taken as a first kind of phase difference. The stand position in the rolling mill train to which the second kind of the phase difference is applied is between the rolling stand in the range of cumulative outside diameter draft ratio of 30-70% and a stand in front of it. The the first kind of phase difference is 60° and the second kind of phase difference is 15-45° or 75-105°. COPYRIGHT: (C)2006,JPO&NCIPI