Effect of Microstructure and Surface Defects on the Capacity of Special Alloy Steel Round Bar for Cold Upsetting

Abstract

Surface defects of special alloy steel round bar of different grades, reasons for their occurrence and degree of influence with a change in microstructure on the capacity for cold upsetting according to groups 66 and 66T by GOST 10702–78 are studied. It is established that necessary conditions for obtaining positive test results for cold upsetting are simultaneous preparation of a favorable granular pearlite microstructure and the absence of round bar surface defects more than 100 μm deep. The absence of surface defects with an unfavorable microstructure does not guarantee positive test results.