PURPOSE: To manufacture the above clad steel tube without generating peeling and crack by giving a negative convergence angle to each roll of a three roll elongator and providing guide shoes freely movably forwards and backwards between every rolls.
CONSTITUTION: A tubing is rolled by inserting a mandrel 3 (or plug) into a metallic tubing 2' with skew rolling method in the three roll elongator and of which each roll 1 is given with a negative convergence angle. Between a pair of adjacent rolls 1, the guide shoe 7 with which bulge between every rolls 1 with rolling the metallic tubing 2' is prevented are provided. Those guide shoes 7 are made to be movable freely forwards and backwards from a roll stand 4 which supports each roll 1 toward the axial line of the metallic tubing 2'. In this way, the angle of torsion is reduced and the generation of flaring can be restrained.
NANBU YOHEI
OZEKI YOSHIHISA
NISHIJIMA SHIGEHIRO
