Geometric Distortion Research Of Carburizing-quenching Process Of Wind Power Gear

As key component in the wind power equipment, wind power gear need to have high surfacehardness and good abrasion resistance. So the heat treatment is essential in the gear manufacturingprocess. But heat treatment of the wind power gear inevitably causes distortion. In this thesis, basedon experiment and simulation approaches, the distortion law and mechanism of18CrNiMo7-6windpower gear after the carburizing-quenching process was obtained. The main work and results are asfollows:1. A non-linear finite element model for the carburizing process was established. Experimentswere conducted in order to verify the simulation results. The results prove that the finite elementmodeling results are in good agreement with the experimental values. Chemical method (peeling),metallographic method, effective hardening layer method were used to characterize the carburizingresults. Also, the result relationships between different methods were obtained. The carbon content inthe boundary of effective hardening layer was also discussed. The results indicate that the carboncontent is round0.35%in the boundary independent of the carburizing process.2. Based on the results of numerical simulation of carburization, the accurate model for thewhole heat treatment process was established. The material behaviors of the18CrNiMo7-6wereacquired by the software JMatPro. The heat transfer coefficient (HTC) under nitrate and waterquenching condition were obtained based on the inverse heat transfer methods-the iterativeapproximation method. The influences of radiation and air convection on air cooling were considered.The air cooling HTC in function form deduced from the heat transfer theory was loaded. Experimentswere conducted in order to obtain temperature, microstructure and stress of the specimen. The resultsprove that the finite element modeling results are consistent with the experimental values.3. The distortion law and mechanism were discussed by the experiment and simulation.Geometry quantities including common normal length, addendum circle diameter, ovality, conicitywere measured. Based on statistical principle, the distortion law of the gear was obtained. At the sametime, the distortion mechanism was analyzed considering the results of numerical calculation andactual heat treatment conditions. The distortion laws received respectively by the experiment andsimulation approach are consistent and both of them satisfy the technical requirements.