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费彦民,蔡忠贤,陈伟,等. “锻–退”循环对微合金钢晶粒细化的作用机制[J]. 安徽工业大学学报(自然科学版),2024,41(3):256-264. doi: 10.12415/j.issn.1671-7872.24014
引用本文: 费彦民,蔡忠贤,陈伟,等. “锻–退”循环对微合金钢晶粒细化的作用机制[J]. 安徽工业大学学报(自然科学版),2024,41(3):256-264. doi: 10.12415/j.issn.1671-7872.24014
FEI Yanmin, CAI Zhongxian, CHEN Wei, GAO Anyang, SI Tingzhi. Mechanism of Grain Refinement of Microalloyed Steel via “Forging–Annealing” Cycle[J]. Journal of Anhui University of Technology(Natural Science), 2024, 41(3): 256-264. DOI: 10.12415/j.issn.1671-7872.24014
Citation: FEI Yanmin, CAI Zhongxian, CHEN Wei, GAO Anyang, SI Tingzhi. Mechanism of Grain Refinement of Microalloyed Steel via “Forging–Annealing” Cycle[J]. Journal of Anhui University of Technology(Natural Science), 2024, 41(3): 256-264. DOI: 10.12415/j.issn.1671-7872.24014

“锻–退”循环对微合金钢晶粒细化的作用机制

Mechanism of Grain Refinement of Microalloyed Steel via “Forging–Annealing” Cycle

  • 摘要: 提出1种新型的“锻–退”循环热加工工艺,且对Ti−Nb−V−B微合金钢进行热处理实验,研究“锻–退”循环对Ti−Nb−V−B微合金钢晶粒尺寸和力学性能的影响;通过透射电镜组织观察和热力学计算,探究Ti−Nb−V−B微合金钢“锻–退”循环晶粒细化机理,并建立微合金钢晶粒细化模型。结果表明:“锻–退”循环热处理可显著细化Ti−Nb−V−B微合金钢的晶粒,“三锻三退”试样的晶粒度由锻前2.5~4.0级细化到9.5~11.5级;“三锻三退”试样的综合力学性能得到显著改善,与“一锻一退”相比,其抗拉强度(Rm)、屈服强度(Rel)、断后伸长率(A)、断面收缩率(Z)和夏比冲击功(KV)分别提高了10.6%,9.9%,18.8%,30.2%和135.0%;Ti−Nb−V−B微合金钢中NbC,TiC,VC和Cr23C6第二相的析出温度分别为1 202,1 187,897,672 ℃,锻前加热和锻造过程中均发生VC和Cr23C6的溶解,锻后退火可促进第二相的析出,“锻–退”循环过程中发生NbC和TiC的析出,锻前奥氏体重结晶、锻造再结晶和锻后退火第二相析出的协同效应是Ti−Nb−V−B微合金钢获得细晶的重要机制。

     

    Abstract: A new “forging–annealing” cycle heat working process was developed, which was employed in heat treatment experiment on Ti−Nb−V−B microalloyed steel. The effects of “forging−annealing” cycle on the grain size and mechanical property of Ti−Nb−V−B microalloyed steel were studied. The mechanism of grain refinement of Ti−Nb−V−B microalloyed steel was explored by transmission electron microscopy observation and thermodynamic calculations, and its grain refinement model was established. The results show that the “forging−annealing” cycle heat treatment can significantly refine the grain size of Ti−Nb−V−B microalloyed steel. After the “three forging and three annealing” treatment, the grain size is refined from 2.5–4.0 levels before forging to 9.5–11.5 levels. The comprehensive mechanical properties of the “three forging and three retreating” specimens are significantly improved, compared to “one forging and one retreating”, its tensile strength (Rm), yield strength (Rel), elongation after fracture (A), reduction of area (Z), and Charpy impact energy (KV) increase by 10.6%, 9.9%, 18.8%, 30.2%, and 135.0%, respectively. The precipitation temperatures of NbC, TiC, VC and Cr23C6 in Ti−Nb−V−B microalloyed steel are 1 202, 1 187, 897, 672 ℃, respectively, and the dissolution of VC and Cr23C6 occurs during the pre-forging heating and forging process, while annealing promotes the precipitation of the second phase, and the precipitation of NbC and TiC occurs during the “forging−annealing” cycle. The synergistic effect of austenite recrystallization before forging, forging recrystallization, and second-phase precipitation by annealing after forging is the key mechanism for obtaining fine grains in the Ti−Nb−V−B microalloyed steel.

     

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