Author(s)

T. Wada, K. Okayama, Y. Morigo

Abstract

Hardened steel is used for dies and molds, and is quenched and tempered to improve its mechanical properties and wear resistance. For dimensional accuracy, hardened steel is machined by a metal removal process. High-speed cutting is an effective method of improving productivity. As, the cutting temperature rises very high in high-speed cutting, the tool materials require both good wear-resistance and heat-resistance, and the cutting parts must be cooled for efficacy and efficiency. In this study, hardened steel was turned with a high-pressure coolant supplied, the chip configurations, the tool wear and the surface roughness were experimentally investigated. The hardened steel used was an ASTM D2 cold-worked die steel (60HRC). The results are as follows: (1) In turning with a high-pressure coolant supplied, the effectiveness of chip breaking performance was improved. In this case, the chip length was shorter with the increase of the coolant pressure, and the chip length was longer with the increase of the cutting speed. (2) In the case of a cutting speed of 10.00 m/s, large wear on the flank face was observed in the dry cutting. It was possible to suppress the tool wear on the flank face with a high-pressure coolant supplied. (3) In the high-pressure coolant cutting method of hardened steel with a cBN tool at a cutting speed of 10.00 m/s, a cBN grain size of 5.0 μm, 45 cBN grain/55 binding phase and main element of the binder phase of TiCN-Al was an effective tool material. The surface roughness by cutting with this cBN tool was almost constant up to a cutting distance of 1080 m.

Keywords

sintered cubic boron nitride compact (cBN), hardened steel, high-pressure coolant supplied, machinability