Cutting Mechanism Research On HSC Hardened Die Steels

Due to its high production efficiency, machining accuracy and lower cost, high speed machining technology will be widely used in aerospace, automotive, mold and other manufacturing fields. Compared to non-metallic materials and non-ferrous metals, ferrous metals and difficult-to-machine materials cannot be well machined with high speed machining techniques. Therefore, how to make high speed machining technology apply to ferrous metals and difficult-to-machine material becomes the technical problem to be solved. In this paper, the cutting force, surface roughness, tool wear and chip morphology were investigated during high speed turning of hardened die steel Crl2MoV with PCBN and ceramic tools. It will provide a theoretical basis for high speed machining technology in the machining of high hardened materials.The experiment results of cutting force indicated that with the cutting speed increases, cutting force decreases. With the feed rate and cutting depth increases, cutting force increases. The radial force increases along with the increasing of corner radius. Under the same conditions, the cutting force of PCBN tool is less than that of ceramic tool.According to the results of surface roughness experiments, with the cutting speed increases, surface roughness decreases. With the feed rate and cutting depth increases, surface roughness increases. The surface roughness first increases then decreases along with the increasing of corner radius. Under the same conditions, the workpiece surface roughness of ceramic tool is better than that of PCBN tool.The experiment results of tool wear indicated that cutting speed has a great influence on tool life. When cutting speed is up to241m/min, the tool life of two materials decline rapidly. Under the same conditions, the tool life of PCBN tool is longer than that of ceramic tool. Cutting speed has a significantly influence on tool wear form. The wear form of PCBN and ceramic tool are crater and flank wear under the relatively low-speed, but the wear form is breakage under the relatively high-speed. The breakage forms include cracks, tipping and exfoliated etc. Adhesive wear, oxidation wear and diffusion wear are the main wear mechanisms of PCBN tool, but abrasive wear, adhesive wear and diffusion wear are the main wear mechanisms of ceramic tool. Under the same cutting conditions, the abrasive wear resistance of PCBN tool is better than that of ceramic tool, but the oxidation resistance of ceramic tool is better than that of PCBN tool. The effect of cutting speed on wear mechanism is significant. As the cutting speed increases, abrasive wear and adhesive wear is weaker.According to the results of chip morphology experiments, along with the increases of cutting speed, the chip up-curl radius increases. The chip lateral-curl radius decreases with the increasing of corner radius. It is easy to form a broken-like chip. When the cutting speed is low (27m/min), it has emerged obvious serrated chip, and the microstructure shows that the adiabatic shear band and macrocracks appear in the chip. Along with the increase of cutting speed, the degree of chip aliasing first increases slightly then keeps invariant. The degree of serrated chip fracture in the shear zone is increasing then is almost a whole fracture.