Effect of intermediate heat treatment on microstructure and properties of new reduced activation steel
QIU Guoxing1, LI Qi1, PENG Leizhen2, CAO Lei3
1. School of Metallurgical Engineering, Xi’an University of Architecture and Technology, Xi’an 710055, Shaanxi, China; 2. Erzhong(Deyang) Heavy Equipment Co., Ltd., Deyang 618000, Sichuan, China; 3. Materials Engineering Department, Hebei College of Industry and Technology, Shijiazhuang 050091, Hebei, China
Abstract：Reduced activation steel with Y and Ti,produced by vacuum induction melting and electroslag remelting was used as the research object and the effects of two special intermediate heat treatment processes,N2-T(heat preservation at 1 050 ℃ following furnace cooling+heat preservation at 980 ℃ following air cooling+tempering at 755 ℃) and N-N-T(normalizing at 1 050 ℃ + normalizing at 980 ℃+tempering at 755 ℃),on the microstructure and mechanical properties of the materials were investigated. The microstructure of the steel was observed by metallographic microscope. The precipitated phase in steel was analyzed by transmission electron microscope. Finally,the hardness,tensile and impact properties of the experimental steel are tested. The results show that the microstructure of the steel is still martensite after intermediate heat treatment,the hardness of N-T(normalizing at 1 050 ℃ + tempering at 755 ℃),N2-T and N-N-T steels are 284HV,275HV and 312HV,and the grain sizes are 8.8,11.7 and 8.0 μm,respectively. N-N-T process could refine the grain effectively. MX carbonitrides rather than M23C6 precipitated first in the steel with heat treatment,which led to a decrease of carbon concentration in the supersaturated martensitic matrix and correspondingly a reduced mean size and volume fraction of M23C6. The size of M23C6 in N2-T steel is reduced from 128 nm to 80 nm and to 84 nm in N-N-T steel. The volume fraction of M23C6 in N2-T steel is reduced from 0.0110% to 0.008 5% and to 0.009 0% in N-N-T steel. Due to the long holding time with furnace cooling,grain and MX phase in N2-N steel coarsened,deteriorated the performance of the steel. The small grain size and fine M23C6 and MX phases are the main reasons for the excellent mechanical properties of N-N-T steel. The yield strength of the steel is 662 MPa at room temperature,the tensile strength is 787 MPa,the elongation is 26.1%,the DBTT is -91 ℃,and the impact energy is 346 J at room temperature.
邱国兴, 李琦, 彭雷朕, 曹磊. 中间热处理对低活化钢组织及力学性能的影响[J]. 钢铁, 2023, 58(7): 106-112.
QIU Guoxing, LI Qi, PENG Leizhen, CAO Lei. Effect of intermediate heat treatment on microstructure and properties of new reduced activation steel[J]. Iron and Steel, 2023, 58(7): 106-112.
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2023, Vol. 58 
