| G13Cr4Mo4Ni4V steel which is the new generation domestic bearing steel is studied in this paper.Aimed to solve the inefficiency and high-cost problems of using a large number of experiments to decide the vacuum carburizing and quenching processes,this paper develops the model of carbon concentration profile of G13Cr4Mo4Ni4V steel during vacuum carburizing and quenching processes.The accuracy of the model is proved by experiment data.The model can provide theoretical instruction when we decide the vacuum carburizing and quenching processes of G13Cr4Mo4Ni4V steel.Various short-time boost carburizing experiments are done,and the carbon profiles of the samples are acquired by using GDS.By fitting the carbon profiles of short-time boost carburizing samples,the diffusion coefficients of carbon under850?,890?,920?and 960?are acquired,which is 6.39×10-12m2/s,11.03×10-12m2/s,17.19×10-12m2/s and 27.37×10-12m2/s separately.By fitting the carbon diffusion coefficients under 850?,890?,920?,960?to Arrhenius equation,the carbon diffusion content and carbon diffusion activation energy are acquired,which is 8.96×10-5m2/s and 153.675kJ/mol separately.And the effect of different alloy elements on the carbon diffusion activation energy is studied.The mechanism of carbon diffusion in G13Cr4Mo4Ni4V steel is that carbon diffuses in the austenite phase between 850?and 1200?,and the carbon diffusion coefficient can be calculated by Arrhenius equation.The diffusion equation is designed to be solved by Crank-Nicolson theme.The accuracy of Crank-Nicolson theme is proved by comparing the analytical solution and numerical solution of two different types of diffusion equation.The boundary condition of vacuum carburizing diffusion equation is developed by using the carbon flow on the boundary.The carbon flow is 24.5mg/?h·cm2?in this research.The error between the calculated solution and the experiment solution is little.This paper also builds the model of carbon profile during quenching process.Based on this model,we can get the carbon profile after quenching from the carbon profile after vacuum carburizing,and we can also get the carbon profile after vacuum carburizing from the carbon profile after quenching.And the accuracy of the model is proved by experiment data.Using the Thermo-Calc software calculates the carbide contents in G13Cr4Mo4Ni4V steel during vacuum carburizing and quenching processes.And the relationship between carbon content and hardness is studied,the carbon content and hardness lie in linear relationship. |
PDF Full Text Request