Study On The Hot Deformation Behavior And Spinning Process Of Thin Wall Cylindrical Hastelloy C276 Alloy Parts

The independent manufacturing capability of key components determines the manufacturing level of nuclear power equipment in our country.Solving the manufacturing problem of nuclear power equipment is the only way for the industrial upgrading of China.Hastelloy C276 alloy,as the shielding sleeve material of the nuclear main pump,is selected in this study.The macro-flow behavior and the microstructural evolution mechanisms,as well as the thermal-forced spinning process are detailly investigated and analyzed.This provides important theoretical basis and technical support for the manufacturing of high-performance shielding sleeve.Meanwhile,it is of great importance for exploring the accurate forming technology of ultra large diameter/thickness ratio thin-walled components in nuclear power,aerospace and other fields.The main conclusions are as follows:(1)The hot deformation behavior of Hastelloy C276 alloy was studied by single pass thermal simulation experiment.Based on the measured data,the depth automatic encoder intelligent constitutive model,the Hensel spittel carofalo model,and the physical mechanism constitutive model were established.Results show that the predicted values of the models were in good agreement with the experimental values,and there precisely describe the hot deformation behavior of Hastelloy C276 alloy.(2)The effect of hot deformation parameters on the microstructure morphologies of Hastelloy C276 alloy were studied by OM,EBSD and TEM observations.According to the sensitivity of material flow properties to strain rate,the dynamic recrystallization kinetics model was established based on strain rate zoning.The correlation coefficient and the average relative error absolute value of the experimental and predicted values are 0.996 and 6.4%,respectively.Meanwhile,the dynamic recrystallization grain size model is established,and the correlation coefficient and the average relative error absolute value are0.992 and 6.28%,respectively.It implies that the dynamic recrystallization behavior during the hot deformation process can be described by the established model.(3)Through the double pass thermal simulation experiments and microstructure analysis,the effect of thermal deformation process parameters on the microstructure morphology during the metadynamic recrystallization process was studied.The metadynamic recrystallization kinetics and grain size model were established.The correlation coefficient and average relative error absolute value between the predicted and experimental value of the metadynamic recrystallization fraction were 0.994 and 2.89%,respectively.Meanwhile,the correlation coefficient and average relative error absolute value between the predicted and experimental values of grain size are 0.988 and 3.44%,respectively.It indicates that the metadynamic recrystallization behavior can be described by the established metadynamic model.(4)The hot processing map of Hastelloy C276 alloy was established,and the safe zone and unstable zone of Hastelloy C276 alloy were obtained.The integrated development of phenomenological constitutive model,dynamic recrystallization model with the corresponding grain size model,and metadynamic recrystallization model with the corresponding grain size model were carried out.The influence of process parameters on the spinning behavior and microstructural evolution mechanism of thin wall cylindrical parts were studied.Combined with the hot processing maps,the suitable process parameters of Hastelloy C276 alloy were found.Taking nuclear main pump as an example,the optimized spinning process parameters is obtained,i.e.,the temperature of 1070-1145℃ and the feed rate of 0.39-4.9 mm/r.It is beneficial to improve the forming quality of thin wall cylindrical parts with Hastelloy C276 alloy.