Bobukh O. Development of method for calculation of rational deformation mode during cold pilger rolling of boiler tubes with allowance for asymmetry of metal deformation

The thesis focuses on the research into cold pilger rolling of boiler tubes from stabilized austenitic stainless steels and development of the method for calculation of the deformation mode with allowance for metal deformation asymmetry. The paper gives theoretical definition of characteristics of a stress-strain state of metal with allowance for asymmetry of the deformation zone in the cross section during cold pilger rolling of austenitic stainless steel boiler tubes. As a result of experimental and theoretical studies, connections between the mode of deformation of the stress state in the deformation zone and the end-use properties of tubes at the end of the manufacturing lead time were found. New data on the effect of the deformation to diameter and wall thickness relation on the stress state and properties of the finished product were obtained. To calculate the mode of deformation it was proposed to use a new factor that establishes connection between the stress state in the deformation zone during cold pilger rolling and the end-use properties of tubes. The method for calculation of the deformation mode in the production of austenitic stainless steel boiler tubes was developed. A special device to control the properties of tubes in the transverse direction and a method for testing ring samples by stretching were developed.