1) School of Materials Science and Engineering, Shenyang University of Aeronautics and Astronautics, Shenyang 110136, China
2) State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110004, China

The machinability tests were conducted by using a YD-21 dynamometer on a CA6161A lathe. The experiments were conducted to determine the effect of free-cutting additives on machining characteristics of austenitic stainless steels. The conventional austenitic stainless steel 1Cr18Ni9Ti (steel A) and the free cutting austenitic stainless steel (steel B) were prepared. The results have shown that machinable inclusions were composed of MnS and CuO, and they might be also Ti_4C2S₂. The presence of Bi in the inclusion was detected by the atom map and electro-probe microanalysis (EPMA), which might be one of the most important factors to improve the machinability of austenitic stainless steels. The cutting forces for steel B were lower than those of steel A at various cutting speeds; the abrasion depth of theflank of the tool for steel B was less than that of the steel A under the same cutting conditions. The machinability of austenitic stainless steel was visibly improved by adding free-cutting additives, such as S, Cu and Bi. Ultimate tensile, yield strength, and total elongation values of the free cutting austenitic stainless steel were improved due to the addition of these free-cutting additives.

the National Natural Science Foundation of China (No. 50334010), the Educational Department of Liaoning Province, China (No. 2008535) and the Shenyang City Application Basic Research Project, China (No. 1071198-1-00)