Longitudinal rolling or cross-rolling with small deformation without a mandrel is performed on the rolled pipe on a longitudinal rolling or cross-rolling sizing machine in order to obtain the specified outer diameter of the rolled pipe. The number of longitudinal rolling and sizing mills is generally 5 to 12, most of which are independently driven two-roller continuous rolling mills. The working frames are arranged at 45 degrees to the ground plane, and adjacent frames are arranged at 90 degrees to each other. Increasing the number of sizing racks can expand product specifications and bring convenience to production. Cross-rolling sizing is carried out on a two-roller or three-roller sizing machine, which is generally configured in a three-roller cross-rolled pipe unit. Compared with longitudinal rolling sizing, cross-rolling sizing products have high outer diameter accuracy, small ovality, and are easy to change specifications and varieties. There is no need to change rolls, just adjust the roll spacing; the disadvantage is low productivity.
In order to improve the quality, expand variety standards and improve unit productivity of the hot-rolled thick-walled rolled pipes after leveling, further deformation processing should be performed on the thick-walled rolled pipes. To this end, two processing methods and three rolling mill methods with basically similar deformation principles have been developed, namely, sizing and reducing processing methods, corresponding to sizing machines, reducing machines and tension reducing machines.
The purpose of the sizing machine is to roll the smoothed rolled pipe into a round and accurately sized finished pipe with a small reduction in outer diameter. The main effect of the diameter reducer is to reduce the diameter, while the tension reducer can not only reduce the diameter, but also reduce the wall.
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