| 摘要 |
<p>PURPOSE:To eliminate the increase of wall thickness to be caused at the pipe end, by altering the ratio of the rotational frequency of each roll according to a specified pattern. CONSTITUTION:The ratio of the rotational frequency of each roll, at the point that the top of the pipe passes over the final stand, is taken as the basic pattern. When the top of the pipe is bitten by the first stand, the ratio of the rotational frequency of each roll is adjusted to a ratio pattern higher than the basic pattern, and then, the rolling work is started. With the advance of the top of the pipe toward the final stand, the ratio of the rotational frequency of each roll is gradually reduced so as to transform the pattern of ratio of the rotationan frequency of each roll into the basic pattern; under this condition, the rolling work is carried on. After the top of the pipe passes over the final stand, the rolling work is carried on according to the basic pattern until the bottom of the pipe arrives at a specifed stand. After the bottom of the pipe passes over the specified stand, the ratio of the rotational frequency of each roll is gradually increased so as to end the rolling work at a high ratio of the rotational frequency of each roll. Hereby, the phenomenon of the wall thickness increase at the top and bottom of the pipe is restricted.</p> |
