Low-temperature Machinability of Hardened Stainless Steel and Its Chip Morphology Evolution

Abstract The impeller material FV520B hardened stainless steel is a typical difficult-to-machine material. During the cutting process, the force and heat load are large, it is easy to work hardening, the tool fails early, and the chip breaking is difficult, which leads to a series of problems such as low processing efficiency, poor processing quality and high cost. In addition to changing the mechanical properties of materials, low-temperature cooling will also promote forced heat transfer in the cutting area, which is an important development direction for clean cutting in the future. In this paper, the effects of low temperature cooling (18℃~-196℃) on cutting machinability and chip morphology evolution of FV520B were systematically studied from macroscopic and microscopic aspects by setting triaxial milling and orthogonal turning experiments respectively based on low temperature jet formed by mixing liquid nitrogen and compressed air. Explore the influence of different jet temperature on cutting force, cutting vibration, surface roughness and tool life under the conditions of variable cutting speed, variable axial depth and variable feed per tooth; The influence of different jet temperature on chip morphology, chip deformation degree and adiabatic shear zone under variable cutting speed was explored. The analysis of the experimental results shows that: low temperature cutting with liquid nitrogen can significantly improve the machinability of the material FV520B and promote the formation of sawtooth chips. The research in this article lays a practical and theoretical basis for the low-temperature cutting of impeller material FV520B, and provides a potential new process for high-quality, high-efficiency and clean machining of impellers.