| 摘要 |
<p>PROBLEM TO BE SOLVED: To obtain the wall thickness variation reducing effect by estimating a draft amount to be applied onto four roll stands based on the external diameter of a core metal bar after heat expansion obtained by calculating and rolling the draft position of every two pairs of hole type rolls of crossing by right angle. SOLUTION: The temperature distribution in axial length direction of a core metal bar 1 on two roll stand series and four roll stands are calculated, the external diameter distributing value after heat expansion is obtained and the average external diameter after heat expansion is calculated. Using the obtained average external diameter of the part used for rolling of the core metal bar 1, the roll gap tightening amount is calculated, the difference of wall thickness between the wall thickness of increased mass part of four places in the circumferential direction and the wall thickness of hole type groove bottom part is calculated. As the standard of an allowable wall thickness one-sided ratio required for the tube after rolling, the target wall thickness at each hole type groove bottom position of four hole type rolls 3... of the four roll stands is calculated, the wall thickness varying reduction requiring amount to be reduced is obtained. Further, the rolling load of the hole type rolls 3... is calculated, the mill spring amount of every two pairs of hole type roll pairs is calculated and the position of two pairs of hole type rolls is set.</p> |
