Longitudinal rolling or cross-rolling of a small amount of deformation without a mandrel on a rolling tube on a vertical rolling or cross-rolling sizing machine, in order to obtain a predetermined outer diameter size of the rolling tube. The number of longitudinal rolling sizing machines is generally 5 to 12, mostly two-roll continuous rolling mills with separate driving. The working frame is arranged at 45 degrees from the ground plane, and the adjacent frames are arranged at 90 degrees. Increasing the number of sizing racks can expand product specifications and bring convenience to production. The cross-rolling sizing is carried out on a two-roll or three-roll sizing machine, and is generally arranged in a three-rolled cross-rolling tube unit. Compared with the longitudinal sizing, the slanted sizing roller has high outer diameter precision, small ovality, convenient change of specifications, no need to change the roll, as long as the roll spacing is adjusted; the disadvantage is low productivity.
After the homogenization of the hot-rolled thick-walled rolling tube, in order to improve the quality, expand the type standard and improve the unit productivity, the thick-walled rolling tube should be further deformed. To this end, two processing methods and three kinds of rolling mill methods, which are basically similar to the deformation principle, are known, namely, the processing method of the sizing and reducing of the rolling tube, and the corresponding sizing machine, reducing machine and tension reducing machine.
The sizing machine is intended to roll the uniformed rolling tube into a round and accurate finished tube, and the outer diameter of the rolling tube is reduced by a small amount. The effect of the reducer is mainly to reduce the diameter, and the tension reducer can not only reduce the diameter, but also reduce the wall.