材料期刊网

奥氏体不锈钢是难加工的材料。通过在传统的奥氏体不锈钢中添加硫、稀土和铋，经过钢锭熔炼、切削试验、组织性能检测，对其切削性能和力学性能进行了研究。结果表明，奥氏体不锈钢中的夹杂物主要由MnS组成。稀土包裹在MnS中，金属夹杂物铋以尾状物附于MnS的两端。稀土具有明显的变质作用，易切削奥氏体不锈钢中的夹杂物大部分呈球状或纺锤状。硫、稀土和铋合金元素的添加降低了切削力、减轻了刀具的磨损、改善了切屑的形状。所开发的合金获得了极好的切削性能。由于硫和铋都是软的相，在变形过程中它们并不诱发裂纹的形成。呈球状的夹杂物不仅有利于切削性能的改善，而且还有利于钢获得良好的力学性能。

Austenitic stainless steels are difficult-to-machine materials. Sulfur, rare earths and bismuth were added to conventional austenitic stainless steel. The machinability and mechanical properties were investigated by vacuum melting, cutting testing as well as microstructure and mechanical properties measuring. The results have indicated that the inclusions are almost composed of MnS. Rare earths are enwrapped in MnS inclusions, and bismuth element is attached to double end of MnS inclusions. The shape of MnS inclusions are mainly spherical and spindle, and this is attributed to metamorphose and spheroidization of rare earth. Sulfur, rare earths and bismuth addition decreases the cutting force and tool wear, and improves the chip shape. An excellent machinability can be obtained for the developed alloy. The mechanical properties of free cutting austenitic stainless steel without lead still exhibit a satisfactory combination of tensile strength and total elongation in spite of the presence of the inclusions. This is because the sulfides and bismuth are all soft phases, and they do not induce formation of cracks during deformation. On the other hand, the spheroidized inclusions can improve not only the machinability, but also the mechanical properties for free cutting austenitic stainless steel.