PURPOSE: To improve the outer diameter controlling accuracy of a product steel pipe, by including the apparent increasing portion of a shrinkage coefficient of outer diam. due to a wear of roll into a shrinkage corfficient of outer diam., in a sizer located at the final stage for manufacturing a seamless steel pipe from a cylindrical billet.
CONSTITUTION: After heating a cylindrical billet 1 by a rotary bed type heating furnace 2, the billet 1 is formed into a sizer blank pipe 10 through a piercer 3, an elongator 5, a plug mill 7, and a reeler 9, and a finished steel pipe 13 is manufactured by finishing the pipe 10 by a sizer 12 after heating the pipe 10 by a reheating furnace 11. In this case; an outer diam. shrinkage coefficient α of the pipe 13 at the time when the outer diam. D of the pipe 13 at the exit side shrinks to the outer diam. (d) in a cold state by the difference between the rolling temperature at the sizer 12 and the outside temperature, is previously fixed, and an apparent outer diam. shrinkage coefficient Δα including the influence of roll wear is added to a true outer diam. shrinkage coefficient αo independent of the roll wear to obtain said α at the time of sizing in which a target outer diam. Do at a prescribed roling temperature is fixed in order to obtain a target outer diam. do in a cold state; then the outer diam. in a cold state is made to coincide with the target outer diam. do.
JPS55147408A | 1980-11-17 | |||
JPS5570408A | 1980-05-27 |