热处理工艺与氮含量对1Cr12NiMo马氏体不锈钢组织和性能的影响

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	热处理工艺与氮含量对1Cr12NiMo马氏体不锈钢组织和性能的影响
	范瑞成
学位类型	硕士
导师	刘奎
	2012
学位授予单位	中国科学院金属研究所
学位授予地点	北京
学位专业	材料工程
关键词	马氏体不锈钢正交试验热处理工艺氮含量回火脆性 Martensitic Stainless Orthogonal Experiment Heat Treatment Process Temper Embrittlement Nitrogen Content
摘要	" 核电站反应堆控制棒驱动机构可拆接头材料采用1Cr12NiMo马氏体不锈钢，作为核电站反应堆内关键部件，其性能直接影响核电站的安全可靠运行。本文主要研究了热处理工艺和氮含量对1Cr12NiMo马氏体不锈钢微观组织和性能的影响规律及作用机理，为制备出性能优异的材料提供可靠的参考依据，具有重要的科学意义和应用价值。通过选取退火、淬火和回火温度为因子来建立正交实验方案，系统地研究了热处理工艺对1Cr12NiMo马氏体不锈钢性能的影响。采用极差分析和方差分析方法证明了回火温度是影响1Cr12NiMo马氏体不锈钢力学性能的主要因素，并最终确定这种不锈钢的最佳热处理制度为：830℃×1h退火+ 985℃×1h油淬+ 630℃×4h空冷回火。 1Cr12NiMo马氏体不锈钢产生回火脆性的温度区间为450~500℃，利用俄歇电子能谱分析仪的分析结果证实了晶界上杂质元素的偏聚不是该不锈钢出现回火脆性的主要原因。脆性的M7C3碳化物的沉淀析出导致不锈钢的韧性较低，而长条状的M7C3碳化物对材料的性能最为不利，是导致材料出现回火脆性的主要原因。利用金相显微镜、SEM、TEM、EDS、XRD等分析手段深入地研究了氮含量对1Cr12NiMo马氏体不锈钢微观组织和力学性能的影响。结果表明：氮的添加，使不锈钢晶格常数增加且晶粒尺寸减小，组织得到细化，从而提高了不锈钢的强度和硬度，而其冲击韧性出现了小幅的降低。随着氮含量从27ppm增加到150ppm时，材料的冲击韧性值持续降低，而当氮含量由150ppm增加到220ppm时，材料的冲击韧性几乎保持不变。此外，1Cr12NiMo马氏体不锈钢的耐Cl—离子腐蚀能力随氮含量增加而增强，当氮含量增加到220ppm时，沉淀析出的Cr2N氮化物对不锈钢的耐腐蚀性能产生不利影响。
其他摘要	" As a key component of nuclear reactor, a 12% Cr stainless steel named 1Cr12NiMo, which is used to manufacture detachable fitting of Control Rod Drive Mechanism, requires superior mechanical properties in order to ensure operation safely and reliably. In this research, the effects of heat treatment process and nitrogen content on microstructure and mechanical properties of 1Cr12NiMo martensitic stainless steel and the mechanisms have been investigated to provide a reference for fabrication of high performance materials. The temperatures of annealing, austenitizing and tempering were chosen as orthogonal factors, when designing the orthogonal experiment though which the effect of heat treatment process on properties of 1Cr12NiMo martensitic stainless steel were investigated. According to direct analysis and variance analysis of experiment results, the tempering temperature was found the main factor on mechanical properties of 1Cr12NiMo martensitic stainless steel. In this experiment, the optimal heat treatment was to anneal at 830℃ for 1h, quench at 985℃ for 1h followed by oil cooling, and temper at 630℃ for 4h followed by air cooling. According to the results of impact experiment and analysis of SEM fractography，the temper brittleness occurred at 450~500℃．The results of Auger electron spectroscopy (AES) confirmed that segregation of? impurities at grain boundaries were not the reason for temper embrittlement of this steel. However，it was observed that the impact toughness was lower when brittle M7C3 carbides precipitated, among which the long strip ones could lead to the lowest impact toughness. The effects of nitrogen content on the microstructure and mechanical properties of stainless steel have also been studied by means of optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The results indicated that nitrogen addition in 1Cr12NiMo steel can increase the strength and hardness by increasing lattice parameters of stainless steel, effectively hindering the austenite grain growth, and refining the martensite lath. Nevertheless, the impact toughness of this steel only showed a minor decrease as the nitrogen content increased. When the nitrogen content increased from 27ppm to 150ppm, the impact toughness decreased, but when increased from 150ppm to 220ppm, the impact toughness was nearly constant. Additionally, the corrosion resistance of stainless steels in solution containing chloride ion was enhanced as nitrogen content of 1Cr12NiMo martensitic stainless steel increased. However, the precipitation of Cr2N nitrides showed a detrimental influence at the same time.
文献类型	学位论文
条目标识符	http://ir.imr.ac.cn/handle/321006/64544
专题	中国科学院金属研究所
推荐引用方式 GB/T 7714	范瑞成. 热处理工艺与氮含量对1Cr12NiMo马氏体不锈钢组织和性能的影响[D]. 北京. 中国科学院金属研究所,2012.