PURPOSE: To detect an influence degree on a torsion angle and deflected thickness at a practical accuracy level when searching a factor of generation of deflected thickness, by evaluating in advance a torsion angle being a factor of generation of deflected thickness in case of manufacture a seamless steel pipe, and setting a measured pitch in the longitudinal direction of the pipe in accordance with said evaluation.
CONSTITUTION: When measuring the thickness of a steel pipe by a Mannesmann system pipe manufacturing method, a measured pitch M in its longitudinal direction is set to 0.4 time or below of a thickness variation pitch (p) calculated by a torsion angle β of a spiral deflected thickness pattern being inherent to an expected thickness variation factor. That is to say, the measurement is executed as M≤0.4p, and (p) is given by the expression (D is an outside diameter of a pipe). In this regard, the angle β is different depending on a shape of a tool, a pass schedule, a rolling condition, etc., therefore, it is necessary to evaluate it in advance in accordance with each manufacturing process. Even if the angle β is limited to a blank pipe which is pierced, that which is caused by deflected head of a billet, a core shift of a plug, and deflection of the blank pipe is about 10W30°, 30W60° and -60W85°, respectively.
SAYAMA YASUHIRO
JPS56168903A | 1981-12-25 |