TECHNOLOGICAL FEATURES OF THE METHOD OF ROLLING OF HOT-ROLLED TUBE ON A STUB MANDREL

A new method of rolling of hot-rolled tube on automatic mill“tandem”consisting of twoa lengthwise rolling mills (a lengthwise rolling mill№1 and №2)is proposed. Methodallowstoachieve the rough tube preovalisation before rollers of a lengthwise rolling mill. The rough tube preovalisationprovides uniform groove filling and a decrease of nonuniform pipe wall thickness. The rough tube preovalisationwill allow to increase elongation ratio from 1,5 to 2,0 on the lengthwise rolling mill №1 and to decrease the elongation ratio on the piercing mill. That will allow to decreasethe risk ofa rolling skin formation of on external tube surface. The way to reduce the probability of the formation of a “guide mark” defect due to the kinematic tension during rolling on a stub mandrel with rough tube preovalisation is investigated. The influence of the kinematic tension on the forming tube in the groove taper at a lengthwise rolling with rough tube preovalisation is investigated