Study On High-speed Cutting Of P20 Hardened Steel Under Cryogenic Liquid Nitrogen Cooling

Hardened steel is a typical difficult-to-machine material,containing martensite phase,high material hardness(45-65 HRC),good wear resistance and mechanical properties,and is widely used in industrial manufacturing.When high-speed cutting of hardened steel,the cutting edge of the tool is subjected to a larger impact load and a higher cutting temperature,the tool wears rapidly,and the tool life is significantly reduced.In addition,high temperature and high cutting stress will also cause a series of changes in the micro-structure of the machined surface,resulting in a metamorphic layer in the machined surface area.The characteristics and performance of the surface deterioration layer will affect the quality of the processed surface and the service life of the parts.The cooling and lubrication method can control the cutting force and cutting temperature,and then control the physical properties of the processed surface metamorphic layer,as well as improve the processing quality,processing efficiency,and improve tool life.Research in this area is of practical significance.This article will cut hardened steel at high-speed right-angle cutting under the condition of dry cutting and liquid nitrogen at low temperature,analyze the change characteristics of tool life,cutting force,cutting temperature,surface roughness,chips,and processed surface metamorphic layer under various parameters and discuss the processing mechanism.First,under dry cutting condition,designing high-speed right-angle cutting experiments with different cutting speeds and different tool wear to study tool life,cutting force,cutting temperature,surface roughness,chips and the processed surface deterioration layer(the micro-structure,micro-hardness and the basic characteristics of phase composition),analyze the influence of cutting speed and tool wear on the surface metamorphic layer,and grasp the basic processing characteristics of high-speed cutting of P20 hardened steel under dry cutting conditions.Secondly,under the condition of liquid nitrogen at low temperature,designing high-speed right-angle cutting experiments with different cutting speeds and different tool wear to study the cutting force,cutting temperature,tool wear,surface roughness,chips and the processed surface deterioration layer(the micro-structure,micro-hardness and the basic characteristics of phase composition),analyze the influence of cutting speed and tool wear on the surface metamorphic layer,and grasp the basic processing characteristics of high-speed cutting of P20 hardened steel under the condition of liquid nitrogen at low temperature.Finally,a comparative analysis of dry cutting and liquid nitrogen cryogenic cutting is carried out,and the difference characteristics of the two methods are obtained,and cutting simulation is carried out to further discuss the cooling and lubrication mechanism,tool wear mechanism and the formation mechanism of processing surface deterioration layer in the high-speed cutting.