Development of Technology and Equipment for Non-destructive Testing of Defects in Sewing Mandrels of a Three-roll Screw Mill 30-80

Abstract

The conditions of heating and cooling of piercing mandrels made of 4X5MFS steel of a three-roll screw mill 30-80 in the production of a closed cavity of steel vessels of small volume are determined. It is established that multiple cycles of heating up to 600 °C and cooling with water up to 80 °C for about 7 seconds/1 cycle lead to the formation of ridges, shells and cracks on the surface and in the volume of the tool. The loss of structural strength of the material leads to the breakdown of the mandrel during the stitching process. The technique and equipment of magnetic powder control have been developed to establish the dynamics of the growth of internal and external defects of mandrels. An equation is obtained that allows determining the increase in the number of defects in the sewing tool of a screw rolling mill. The technology of non-destructive testing made it possible to develop a rational plan for replacing the sewing mandrels, which allows for predicting the appearance of defects leading to a complex breakdown of the deforming tool at the NPO Pribor machine-building enterprise.