Characterization of Free Cutting Phase in Free Cutting Stainless Steel Containing High Copper

The machinability of 4Cr13 steel was improved obviously by adding Cu and S. The effect of copper addition on the machinability of 4Cr13 was similar to that of sulphur addition. By means of SEM, EBSD, and HREM, the distribution and size of the free cutting phase in the steel 4Cr13Cu were studied. The results showed that the free cutting phase was copper-rich phase. The copper-rich phases dispersed in the steel and were determined to have about 10 nm in diameter. The content of copper in the copper-rich phase was over 70%.