PURPOSE: To easily determine adequate and correct rolling conditions by selecting the equation of the conditions for preventing the generation of a defective bite and tail clogging as well as the equation of the conditions for preventing the rupture of a tail end in the stage of ultrathin wall piercing.
CONSTITUTION: The equation I of the conditions for preventing the generation of the defective bite and tail clogging and the equation II of the conditions for preventing the rupture of the tail end in the stage of ultrathin wall piercing with a cross helical rolling mill for piercing and drawing a hollow rolling stock pipe by rolling rolls. The range where the rolling to satisfy the conditions to decrease the generation of thickness deviation is possible is selected and the rolling conditions including the diameter of a plug, roll gap, forward slip of the plug, guide shoe gap, etc., are so determined that the rolling conditions are brought to approximately the center of the rollable range. Here, L*, DP*, LP*, E*, H*, t1* are respectively the forward slip of the plug with respect to the diameter of the rolling stock pipe, diameter, effective rolling length, roll gap, guide shoe gap, and the wall thickness ratio of the rolling stock pipe. (a) and (b) are coeffts. which depend slightly on the shape of tools (rolls, plug, guide shoes), the steel kind of the rolling stock pipe, rolling conditions, etc.
SAYAMA YASUHIRO
EJIMA AKIO
NAKAGAWA KICHIZAEMON
ABE HIDEO
KANARI SHOHEI
