Research On Hard Cutting And Surface Integrity Of 20CrMnTi Hardened Steel

20CrMnTi hardened steel was widely used in transmission parts in the field of construction machinery and the automobile,because of its excellent comprehensive properties.In order to solve the problems and difficulties of fast tool wear and difficult surface quality control of 20 CrMnTi hardened steel in engineering application,according to the metal cutting theory,the following studies were carried out by means of experiment and finite element analysis.The characteristics of the tool-chip contact zone affects the whole machining process.In order to better study the law of hard cutting,the dynamic changes of friction coefficient,specific heat capacity,and thermal conductivity of materials with the increase of temperature were explored.Based on the friction theory,the friction coefficient expression of temperature was constructed by the cone table-disk friction test.By means of thermophysical experiments,an empirical model of specific heat capacity and thermal conductivity varying with temperature was established.Based on the assumption of uniformity and one-dimensional stress wave,the stress-strain,strain rate sensitivity,and temperature sensitivity of 20 CrMnTi hardened steel were comprehensively analyzed by Hopkinson compression bar tests under different strain rates and temperatures(20? to 800?).The dynamic mechanical behavior of the material was discussed.The results showed that the material was a strain rate and temperature-sensitive material.The J-C(Johnson-Cook)constitutive model with good accuracy was established by data fitting.According to the hypothesis of the three-dimensional to two-dimensional and cutting process,the finite element model of right-angle cutting 20 CrMnTi hardened steel was established in Advant Edge.Through the right-angle cutting tests,the validity of the finite element model was verified.The influence of different cutting parameters on cutting force and cutting temperature was further analyzed.The effects of cutting process parameters on the evaluation indexes of surface integrity(residual stress,surface roughness,white layer)were studied.The residual stress was analyzed by the finite element method,and the distribution law of residual stress under different working conditions was studied.The surface morphology was observed by white light interferometer and the surface roughness was obtained.The white layer was studied by field emission scanning electron microscope.The influence of cutting parameters on surface integrity was discussed.According to the above the finite element model of hard cutting,and the influence of different cutting conditions on the evaluation of machining quality index was analyzed,which provided technical support for the research of eco-friendly cutting technology and optimal cutting parameters of difficult-to-machining materials.the research results can be widely applied to the mechanical manufacturing.