Chuiev A. The development of parameters calculations method and improvement of pipe production technology with a decrease of surface defects in aggregates with the double-stand lengthwise rolling mill

The dissertation is devoted to the development of parameters calculations method of technology in order to reduce the formation of uncorrectable defects on internal surface of pipes during the processes of screw piercing in the double-roll piercing mills and lengthwise rolling in the double-stand lengthwise rolling mill. The complex influence of the rolls wear and the roll pass design on changes in shape of piercing mill deformation zone at ensuring the metal pickup has been theoretically established. The method of calculation of the piercing mill settings taking into account changes of profile of rolls during their exploitation in order to ensure minimum acceptable reductions of diameter before the mandrel nose, in order to reduce formation of uncorrectable defects such as " internal scab", has been further developed. The method of calculation of the deformation parameters in the lengthwise rolling mill with complex accounting of the distribution of reductions on diameter and wall thickness around the perimeter of the roll pass and between the stands of the mill has been developed. The recommendations for improving the roll pass design of the stands of the lengthwise rolling mill and improvement of high quality pipes production technology with ultrasonic inspection on 5% artificial defect have been developed. The results of work have been implemented in production and are used in the educational process.