| 摘要 |
<p>PURPOSE:To make constant the length of elongation and to make little the scatter of thickness of pipe wall, in controlling the length of elongation of the pipe through the continuous elongator, by varying the ratio of circumferential speeds depending on the characteristic value of the mandrel bar and the previously estimated information on the blank pipe. CONSTITUTION:The scatter of the length of elongation (average wall thickness) of the pipe in the mandrel mill depends especially on the weight of blank pipe and characteristic of the mandrel bar. That is, if the friction factor of the mandrel bar is large, a large ratio of circumferential speeds is required for obtaining the same length of elongation, a unit weight and the average wall thickness; if the friction factor is small, a small ratio of circumferential speeds is required. The relation between this ratio of circumferential speeds, the temperature of raw material, etc., is previously estimated through experiments; and s suitable number of revolution is selected and employed for every blank pipe, on purpose to minimize the scatter of length of elongation of the pipe. Besides, the relation between the length of elongation and a unit weight is expressed by the difference of friction factors, mub between the external surface of pipe and the roll, and mua between the internal surface of pipe and mandrel bar; this relation is illustrated. If mub-mua is constant, the average wall thickness becomes constant.</p> |
