A Design Of Cooling System And Cutting Experiments For The Cryogenic Machining Of Difficult-to-Cut Materials

The cutting process of difficult-to-cut materials has been one of the difficult problems in the field of machining.This is not only reflected in the rapid tool wear,but also the machining quality is not easy to control.With the development of modern cutting technology,cryogenic machining with liquid nitrogen as the coolant has received extensive attention in recent years.In this paper,based on the design of a temperature-controlled cooling system for cryogenic machining,the research on cryogenic machining of TC4 titanium alloy and 35 Cr Mn Si A high strength steel is deeply conducted under the condition of liquid nitrogen and different temperature nitrogen jet cooling.The major research works are as follows:(1)Based on the research status of cryogenic machining cooling system and experimental requirement,a cryogenic machining cooling system with liquid nitrogen as the cooling medium is designed.It can provide liquid nitrogen and low-temperature nitrogen jet from-196? to normal temperature,by controlling the mixing ratio of liquid nitrogen and normal temperature nitrogen.(2)The influence of cutting speed and jet temperature on the cutting force is studied through milling experiment of TC4 titanium alloy and 35 Cr Mn Si A high strength steel.And the cutting temperature of cryogenic machining TC4 titanium alloy using liquid nitrogen as the coolant is measured and analyzed by applying Semi-artificial thermocouple technique.(3)The influences of jet temperature and cutting speed on the macroscopic morphology of chips are studied in orthogonal machining of TC4 titanium alloy and 35 Cr Mn Si A high strength steel.The influence of cutting speed and jet temperature on the micro-morphology of chips is analyzed from the aspects of cross section metallographic structure of chips and serrated degree of chips.(4)The cryogenic milling experiments of TC4 titanium alloy and 35 Cr Mn Si A high strength steel are carried out.The effects of jet temperature and cutting speed on the machined surface integrity are analyzed from the aspects of surface microhardness,metallographic structure of surface layer and surface residual stress.(5)According to the characteristics of cutting tool wear under cryogenic high feed milling TC4 titanium alloy,the corresponding criterion of tool wear is presented,tool life under the condition of liquid nitrogen cooling and dry cutting is analyzed.