快速加热回火过程中9Ni钢组织的演化
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摘要
采用淬火膨胀仪模拟了9Ni钢的快速加热回火工艺,并结合显微组织观察、淬火后残留奥氏体含量的计算以及回火过程中热膨胀曲线的分析,研究了9Ni钢快速加热回火过程中组织的演变行为。结果表明:淬火终冷温度略高于M_f点时,淬火组织中存在少量的残留奥氏体,经快速加热后能够促进回火过程中逆转变奥氏体的生成;但当终冷温度过高时,残留奥氏体量大幅增加,反而会抑制逆转变奥氏体的形成;快速加热有利于马氏体的逆转变及碳原子在奥氏体中的富集,但这两种机制存在竞争关系,快速加热回火后组织中的奥氏体较少时,碳原子的富集会使其稳定性上升,反之则导致碳原子在奥氏体中的富集程度减弱,稳定性变差。
The rapid heating and tempering process of 9 Ni steel was simulated by means of quenching dilatometer, and the microstructure evolution behavior of the 9 Ni steel during rapid heating and tempering was studied by microstructure observation, the calculation of residual austenite content after quenching and the analysis of thermal expansion curve during tempering. The results show that a small amount of residual austenite exists in the quenched microstructure of the steel when the quenching end cooling temperature is slightly higher than the M_f point, which can promote the formation of reversed austenite during tempering after heating at a high rate. However, when the final cooling temperature is too high, the amount of residual austenite increases significantly, which will inhibit the formation of reversed austenite. Rapid heating is beneficial to the reverse transformation of martensite and the enrichment of carbon atoms in austenite. However, there is a competitive relationship between these two mechanisms. If the content of austenite in the microstructure after rapid heating and tempering is less, the stability of the martensite increases due to the enrichment of carbon. Conversely, the enrichment of carbon atoms in austenite decreases and the stability becomes worse.
The rapid heating and tempering process of 9 Ni steel was simulated by means of quenching dilatometer, and the microstructure evolution behavior of the 9 Ni steel during rapid heating and tempering was studied by microstructure observation, the calculation of residual austenite content after quenching and the analysis of thermal expansion curve during tempering. The results show that a small amount of residual austenite exists in the quenched microstructure of the steel when the quenching end cooling temperature is slightly higher than the M_f point, which can promote the formation of reversed austenite during tempering after heating at a high rate. However, when the final cooling temperature is too high, the amount of residual austenite increases significantly, which will inhibit the formation of reversed austenite. Rapid heating is beneficial to the reverse transformation of martensite and the enrichment of carbon atoms in austenite. However, there is a competitive relationship between these two mechanisms. If the content of austenite in the microstructure after rapid heating and tempering is less, the stability of the martensite increases due to the enrichment of carbon. Conversely, the enrichment of carbon atoms in austenite decreases and the stability becomes worse.
引文
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[2] 战国锋,刘继雄,肖建中,等.Cu及热处理工艺对9Ni钢组织及性能的影响[J].材料热处理学报,2015,36(8):139-143.ZHAN Guo-feng,LIU Ji-xiong,XIAO Jian-zhong,et al.Influence of addition of Cu and heat treatment on microstructure and properties of 9Ni steel[J].Transactions of Materials and Heat Treatment,2015,36(8):139-143.
[3] 熊庆人,霍春勇,李为卫,等.9%Ni钢亚温淬火处理工艺参数试验研究[J].材料热处理学报,2017,38(2):136-142.XIONG Qing-ren,HUO Chun-yong,LI Wei-wei,et al.Experimental investigation of intercritical hardening of a 9%Ni steel[J].Transactions of Materials and Heat Treatment,2017,38(2):136-142.
[4] Nakanishi D,Kawabata T,Aihara S.Effect of dispersed retained γ-Fe on brittle crack arrest toughness in 9% Ni steel in cryogenic temperatures[J].Materials Science and Engineering A,2018,723:238-246.
[5] 王国栋.TMCP技术的新进展—柔性化在线热处理技术与装备[J].轧钢,2010,27(2):1-6.WANG Guo-dong.New progress of TMCP technology -flexible on-line heat treatment process and equipment[J].Steel Rolling,2010,27(2):1-6.
[6] Tsuchiyama T,Tobata J,Tao T,et al.Quenching and partitioning treatment of a low-carbon martensitic stainless steel[J].Materials Science and Engineering A,2012,532:585-592.
[7] Speer J G,Rizzo A F C,Matlock D K,et al.The “quenching and partitioning” process:background and recent progress[J].Materials Research,2005,8(4):417-423.
[8] Gu K X,Wang J J,Zhang H,et al.Effect of minimum temperature on the mechanical properties and reversed austenite content of 9%Ni steel subjected to cryogenic treatment[J].Rare Metal Materials and Engineering,2018,47(11):3277-3283.
[9] 杨跃辉,武会宾,蔡庆伍,等.9Ni钢中回转奥氏体的形成规律及其稳定性[J].材料热处理学报,2010,31(3):73-77.YANG Yue-hui,WU Hui-bin,CAI Qing-wu,et al.Formation of reversed austenite and its stability in 9Ni steel during tempering[J].Transactions of Materials and Heat Treatment,2010,31(3):73-77.
[10] 张玉祥,何亮.钢奥氏体分解转变体积分数计算方法研究进展[J].材料开发与应用,2016,31(1):83-86.ZHANG Yu-xiang,HE Liang.Research progress on calculation method for fraction transformed of austenite decomposition in Steel[J].Development and Application of Materials,2016,31(1):83-86.
[11] 陈俊.9Ni钢的显微组织演变及力学性能研究[D].沈阳:东北大学,2010.CHEN Jun.Study on microstructure evolution and mechanical properties of 9Ni steel[D].Shenyang:Northeastern University,2010
[12] 朱祖昌.马氏体转变(十六)[J].热处理技术与装备,2014,35(2):65-70.ZHU Zu-chang.Martensitic transformation(16)[J].Heat Treatment Technology and Equipment,2014,35(2):65-70.
[13] 武会宾,唐荻,蔡庆伍,等.重加热速率对X80级管线钢中M/A岛的影响[J].材料热处理学报,2012,33(6):100-104.WU Hui-bin,TANG Di,CAI Qing-wu,et al.Effect of re-heating rate on M/A islands in high deformability pipeline steel X80[J].Transactions of Materials and Heat Treatment,2012,33(6):100-104.
[14] Chen S H,Zhao M J,Li X Y,et al.Compression stability of reversed austenite in 9Ni steel[J].Journal of Materials Science and Technology,2012,28(6):558-561.
[15] 张玉妥,李丛,王培,等.9Ni钢拉伸性能的同步辐射高能X射线原位研究[J].金属学报,2016,52(4):403-409.ZHANG Yu-tuo,LI Cong,WANG Pei,et al.In situ synchrotron X-ray diffraction investigation on tensile properties of 9Ni steel[J].Acta Metallurgica Sinica,2016,52(4):403-409.
[16] Zhang J M,Li H,Yang F,et al.Effect of heat treatment process on mechanical properties and microstructure of a 9% Ni steel for large LNG storage tanks[J].Journal of Materials Engineering and Performance,2013,22(12):3867-3871.