Experimental study on the influence of bismuth element on the microstructure and cutting performance of free-cutting steel

Abstract In this paper, through cutting experiments, a comparative analysis was conducted on the differences in cutting performance between ordinary 12L14 free-cutting steel and 1214Bi free-cutting steel with added Bi element under the same cutting process parameters. The experimental results show that the introduction of Bi element significantly reduces the cutting force and cutting temperature of free-cutting steel during the cutting process, effectively improves the flatness and finish of the machined surface of the workpiece, and the surface roughness Ra value is significantly lower than that of the steel without Bi element; in terms of chip morphology, Bi element not only makes it easier for chips to separate from the matrix, but also significantly improves the chip-breaking performance, which is specifically manifested in the formation of hair-like and broken arc chips under low-speed working conditions, and short tube spiral chips during high-speed cutting; in terms of tool wear, Bi element plays a good lubricating and protective role, significantly reducing the degree of tool wear and effectively prolonging the service life. Therefore, the free-cutting steel with added Bi element shows better comprehensive cutting performance during the cutting process, and its cutting performance is significantly improved compared with the traditional 12L14 free-cutting steel.