Classification of Sulfides in High‐Sulfur Steel and Establishment of Automatic Sulfide Classification Method

Abstract

Sulfides with different distribution states may have different effects on steel properties. How to separately count each kind of sulfide remains a question. In the current study, sulfides in 1215 free‐cutting and 416 free‐cutting stainless steel are counted by Image‐Pro Plus image‐processing software. The sulfides can be divided into three categories, that is, cluster‐like sulfides, chain‐like sulfides, and individual sulfides. The features of each kind of sulfide are summarized and an automatic sulfide classification method is proposed. By using this method, sulfides in a metallographic photograph of 1215 steel are successfully classified into three types and counted separately. The quantity percentage of chain‐like, cluster‐like, and individual sulfides is 24.65%, 56.79%, and 18.56%, respectively, while the area percentage of different types of sulfides is 34.33%, 52.80%, and 12.87%. Individual sulfides have the highest‐quantity percentage of sulfides with a diameter smaller than 3 μm and with an area smaller than 10 μm2. Through this method, different types of sulfides can be deeply analyzed. It offers reliable data to evaluate whether the sulfides are well controlled or not, providing a guideline for the improvement of sulfide control methods.