The effect of tempering temperature on mechanical properties and microstructure of low alloy Cr and CrMo steel
The effect of tempering temperature on mechanical properties and microstructure of low alloy Cr and CrMo steel
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回火温度对低合金Cr、CrMo钢力学性能和显微组织的影响
DOI：
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发表时间：
1998
期刊：
影响因子：
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通讯作者：
P. Matković
中科院分区：
文献类型：
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作者：
M. Gojić;L. Kosec;P. Matković
研究了碳、锰、铬含量相近的两种低合金铬和铬钼钢的回火温度对力学性能和显微组织的影响。用高速膨胀仪对钢进行了淬火和回火处理。钢的平均冷却速度为30K S-1，淬火温度范围为1123~573K，回火温度分别为673、823和973K。淬火时形成的马氏体为全板条状，残余奥氏体量为2%。结果表明，经973K回火后，CrMo钢铁素体中只含有正交渗碳体，而CrMo钢铁素体中含有渗碳体和六方Mo2C颗粒。在相同回火条件下，与铬钢相比，CrMo钢具有较高的强度和较低的塑性。结果表明，这种差异是由于原始奥氏体晶细小、基体中的亚结构和以Mo2C为主的析出弥散强化所致。透射电子显微镜的明、暗场显微照片以及择优取向关系的选区衍射图分析表明，渗碳体从铁素体基质中析出。断口分析表明，随着回火温度的升高，断口形貌发生变化。在973K回火时，通过微孔结合机制获得延性断裂。
Two low alloy Cr and CrMo steels with similar levels of carbon, manganese and chromium have been studied to determine the effect of tempering temperature on the mechanical properties and microstructure. The quenching and tempering of steels were carried out using a high-speed dilatometer. The steels were quenched at the average cooling rate of 30 K s-1 in the temperature range from 1123 to 573 K by flowing argon and tempered at 673, 823 and 973 K. The martensite of steels formed during quenching was of entire lath morphology with 2 vol% retained austenite. It was found that after tempering at 973 K the Cr steel contained only orthorhombic cementite, while the CrMo steel contained the cementite and hexagonal Mo2C particles in the ferrite matrix. At the same tempering conditions, the CrMo steel shows higher strength but lower ductility as compared to those of Cr steel. It is shown that this difference results from finer prior austenite grain, substructure within matrix and precipitate dispersion strengthening, primarily by Mo2C. Transmission electron microscopy (TEM) bright- and dark-field micrographs as well as selected area diffraction pattern analysis of orientation relationship showed that the cementite precipitated from the ferrite matrix. Fractography analysis showed that the morphology fracture surface was changed by increasing tempering temperature. Tempering at 973 K obtained ductile fracture by the microvoid coalescence mechanism.