Title: Study on the machinability of high-silicon high-carbon graphite-based free-cutting steel in contour turning

Authors: Yong-Hoon Roh; Byeong-Jun Kang; Gyeong-Tae Kim; Doo-Hyun Na; Sangwoo Choi; Namsuk Lim; Kiho Rhee; Youngseog Lee

Addresses: Department of Mechanical Engineering, Chung-Ang University, Seoul, South Korea ' Department of Mechanical Engineering, Chung-Ang University, Seoul, South Korea ' Department of Mechanical Engineering, Chung-Ang University, Seoul, South Korea ' Department of Mechanical Engineering, Daelim University College, Anyang, South Korea ' Steel Products Research Lab., POSCO, Pohang, South Korea ' Steel Products Research Lab., POSCO, Pohang, South Korea ' Steel Solution Research Lab., POSCO, Pohang, South Korea ' Department of Mechanical Engineering, Chung-Ang University, Seoul, South Korea

Abstract: The contour lathe turning test was performed to evaluate the machinability of PosGRAM70 (eco-friendly, free-cutting steel). A high-speed camera was used to capture the shapes of the generated chips. PosGRAM70 with a diameter of 30 mm was machined into jar-shaped specimens with concave and convex contours for different cutting paths, feed rate, and depth of cut. For comparison, SUM24L (most widely used, but harmful to humans by emitting toxic gas during cutting) was employed in the turning test. Finely dispersed graphite particles in PosGRAM70 with low strength served as stress concentration sources and assisted in the nucleation and growth of voids, which caused microcracks, leading to the breakage of continuous chips into smaller pieces. The low-melting-point lead in SUM24L not only facilitated the generation of microcracks but also acted as a lubricant to reduce friction during cutting. Hence, the chip breakability of PosGRAM70 is as good as that of SUM24L.

Keywords: machinability; graphite; microcracks; void nucleation; high-speed camera; free-cutting steel.

DOI: 10.1504/IJMPT.2023.136522

International Journal of Materials and Product Technology, 2023 Vol.67 No.3/4, pp.416 - 434

Received: 02 Nov 2022
Accepted: 30 Aug 2023
Published online: 05 Feb 2024 *

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