Unqualified Causes of Percentage Reduction Area for 45 Round Steels

A batch of 45 round steels have low primary qualified rate of percentage reduction area. The causes of the low primary qualified rate of percentage reduction area for the 45 round steels in this batch were analyzed by means of macroscopic observation, tensile test, chemical composition analysis, metallographic examination, non-metallic inclusion detection and microscopic analysis. The results show that there were many non-metallic inclusions and hydrogen induced flake defects in this batch of the 45 round steels, which make stress concentrated at the defects, destroyed the continuity of the matrix, reduced the mechanical properties of the 45 round steels, and caused the low primary qualified rate of percentage reduction area for the 45 round steels in this batch.