Strain compensation constitutive equation and hot processing map of RAFM steel
QIU Guo-xing1, BAI Chong1, CAI Ming-chong1, WANG Jian-li1, LI Xiao-ming1, CAO Lei2
1. School of Metallurgical Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, Shaanxi, China; 2. Department of Materials Engineering, Hebei Vocational University of Industry and Technology, Shijiazhuang 050091, Hebei, China
Abstract：Reduced activation ferritic martensitic (RAFM) steels have low irradiation swelling rates and excellent mechanical properties,which are considered to be the preferred structural materials for fusion reactors. However,the high strength of RAFM steels and the high resistance to cold plastic deformation make it difficult to achieve large-scale production through cold or low-temperature processing. The thermal simulation compression test investigated the single-pass thermal compression experiment of the RAFM steel(0.11C-9.4Cr-1.35W-0.22V-0.05Si-0.11Ta-0.50Mn) in the MMS-200 thermal simulator under the temperature of 950 ℃ to 1 200° C,strain rate of 0.01 s-1 to 5 s-1,and maximum deformation of 0.5. Based on the dynamic material model,a strain compensation constitutive equation and hot processing map of RAFM steel under different strain rates were constructed,and the optimal hot deformation parameters were determined. The law of microstructure evolution during the deformation process was observed by a metallographic microscope,which provides a theoretical reference for the hot processing forming process and microstructure optimization of RAFM steel. The results show that the flow stress of nuclear power steel gradually decreases with the increase of deformation temperature at the same strain rate,and the flow stress increases with the increase of strain rate at a certain deformation temperature. The effect of temperature and strain rate on the microstructure is mainly determined by the dynamic,recrystallization,and other softening mechanisms that occur inside the metal. The mathematical model of RAFM steel was established by a sixth-order polynomial. It has high prediction accuracy with a square correlation coefficient of 0.972. The results show that the rising temperature provides sufficient energy for recrystallization,and the softening mechanism of materials changed from dynamic recovery to dynamic recrystallization. When the strain rate decreases,the energy has enough time to diffuse,which is beneficial to dynamic recrystallization. The optimal range of hot processing parameters for obtaining a uniform dynamic recrystallized structure of RAFM steel is that the deformation temperature is 1 060-1 130 ℃,the strain rate is 0.13-0.36 s-1,and the alloy dissipation coefficient η reaches 36%.
邱国兴, 白冲, 蔡明冲, 王建立, 李小明, 曹磊. RAFM钢应变补偿本构关系及热加工图[J]. 钢铁, 2022, 57(11): 157-166.
QIU Guo-xing, BAI Chong, CAI Ming-chong, WANG Jian-li, LI Xiao-ming, CAO Lei. Strain compensation constitutive equation and hot processing map of RAFM steel[J]. Iron and Steel, 2022, 57(11): 157-166.
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