PURPOSE: To roll smoothly a pipe stock while preventing its squeezing-out phenomenon by setting the starting position of the thickness-reduction of pipe stock, performed by rolling rolls and a plug, from the gorge part of rolling roll to the outlet side of rolling, based on the equation, in elongating a hollow pipe stock by a skew rolling mill.
CONSTITUTION: The distance Y created toward the outlet side of rolling, by the starting position of the thickness-reduction of a pipe stock, performed by rolling rolls 21 and a plug 34, with respect to the gorge part of rolling roll 21, is obtained and set by the equation I. The signs used in the equation I are as follows, D: outlet side pipe diam., α: slant angle of rolling roll 21, η: feeding efficiency, : elongation ratio of pipe. Accordingly, after reducing the diam. of pipe stock, before thickness-reduction and expanding, as small as possible, the thickness-reduction and expanding of pipe stock is started, to prevent the pipe stock from squeezing out of the gap between the roll 21 and a guide shoe.
TOGASHI FUSAO
KAGAWA MASAHIRO
