Study On Thermal Deformation And Microstructure Evolution Behavior Of 17CrNiMo6 Steel

As a kind of renewable clean energy,wind energy has the characteristics of high energy storage,no pollution and mature technology,and its application prospect is good.17Cr Ni Mo6 steel has good plastic toughness,hardenability and comprehensive machining performance,and is usually used to process wind power gear,the core component of wind power equipment.Wind power equipment is generally arranged in dangerous places and difficult to maintain.The quality of wind power gear directly affects the safety of the whole wind power equipment,which puts forward more stringent requirements for its production and manufacturing process.In order to improve the performance of gears in the whole production process,multi-fire forging is often needed.It is of great significance to study the thermal deformation microstructure evolution of17Cr Ni Mo6 for formulating and improving the forging process of wind turbine gear.In this paper,basic research has been carried out from grain growth,dynamic recrystallization,static recrystallization and other aspects,and the main conclusions are as follows:（1）Through the heat insulation experiment,this paper analyzes the different heating temperature and holding time under 17Cr Ni Mo6 steel austenitic grain size evolution behavior,based on regression of objective function is minimum error sum of squares method,built the steel austenitic grain growth kinetics model,through the experiment proved that the model can accurately reflect 17Cr Ni Mo6 steel austenitic grain growth rule.（2）The single-pass thermal compression test of 17Cr Ni Mo6 steel was carried out on Gleeble-1500 thermal simulation machine.Combined with friction correction and linear fitting method,the Arrhenius hyperbolic sine constitutive equation of 17Cr Ni Mo6 steel under different thermal deformation conditions was established.The thermal working maps of 0.2,0.4,0.6 and 0.8 with different true strains were constructed,and the optimal thermal working parameters(1466K-1523K,0.03s^-1-0.22s^-1)and unstable flow region were determined according to the thermal working maps and microstructure observation.（3）The effect of different deformation conditions on the dynamic recrystallization（DRX）microstructure of 17Cr Ni Mo6 steel was analyzed.It was concluded that the increase of compression temperature and the decrease of strain rate promoted the increase of DRX volume fraction and DRX grain size.The increase of deformation promoted DRX nucleation,and the grain size of DRX increased slightly.The DRX kinetic model and DRX grain size model were established.（4）The influence of different thermal deformation conditions on the static recrystallization（SRX）behavior of 17Cr Ni Mo6 steel was analyzed by two-channel subisothermal thermal compression experiments.The SRX volume fraction increased with the increase of compression temperature,interval time,pre-strain and strain rate.The SRX grain size decreases with the decrease of compression temperature,the increase of pre-strain and strain rate,and the decrease of original grain size.The SRX kinetic model and SRX grain size model are established by fitting regression method.（5）The constitutive model,critical strain model,dynamic and static recrystallization kinetics model and grain size model were embedded in DEFORM-3D software,and the isothermal hot compression numerical simulation of 17Cr Ni Mo6 steel was carried out.The simulation results were compared with the experimental metallographic structure,which was consistent with each other and verified the accuracy of the established model.