Effect of initial temperature on cutting speed in liquid nitrogen assisted abrasive suspension jet machining of tungsten steel

Abstract

Liquid nitrogen assisted abrasive suspension jet (LN2-ASJ) is a combined machining method of cooling before cutting, which can greatly improve the efficiency of ASJ machining tungsten steel (hard alloy). The reduction in machining temperature changes the mechanical properties of the material, thereby affecting the fracture mode and failure speed. This paper focused on YG8/YG20 tungsten steel, analyzed its failure process at low temperatures, established a mathematical model for cutting speed, elucidated the effect of initial temperature on cutting speed, and conducted LN2-ASJ cutting experiments. The results showed that ductile fracture always occurs at the initial kerf. As the kerf depth increases, tungsten steel may begin to undergo brittle fracture, with the occurrence coordinates of brittle fracture depending on the initial temperature. The cutting speed in the brittle fracture area (18.88-21.21mm/s) is approximately 8 times that in the ductile fracture area (2.39-3.87mm/s), with the optimal cutting performance achieved when the initial temperature is controlled at -80°C. Compared to room temperature, LN2-ASJ increased the average cutting speed of YG8 by 32% (from 3.71mm/s to 4.90mm/s) and that of YG20 by 37% (from 3.95mm/s to 5.43mm/s).