METHOD OF PRODUCING POLYHEDRAL TUBES Russian patent published in 2016 - IPC B21B17/00 

FIELD: pipes.

SUBSTANCE: invention relates to production of polyhedral tubes. Method involves shaping a round tube into a polyhedral one in several consecutive sites of deformation formed by shaping, calibrating and dressing rolls. Higher accuracy of geometrical dimensions at high quality of the surface is provided by that the shaping is performed by idle rolls in the amount as per the number of faces of the finished tube at specified temperature, total reduction by diameter and deformation rate. Also specified are reductions by diameter in shaping, calibrating and dressing sites of deformation.

EFFECT: for deformation of low-plasticity steels prior to rolling a mandrel is introduced into the tube and rolling in the shaping rolls is performed successively on the mandrel, which is displaced synchronously with the tube till the mandrel front end exits the last shaping site of deformation, then the mandrel is stopped and held from an axial movement, and rolling in the calibrating and dressing rolls is performed without the mandrel.

3 cl, 1 tbl, 1 ex