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通过SEM和TEM等方法对Ti-Nb-Mo微合金钢在两种不同冷却工艺下回火处理后的析出相分布、形貌和粒度进行了观察和分析,结合拉伸实验结果和硬度测试结果研究了回火过程中纳米析出颗粒的变化对试验钢强度变化的影响。结果表明,热轧淬火后试验钢基体组织为板条贝氏体,经650℃回火处理后并未形成纳米析出相,因此导致试验钢强度明显下降;而热轧空冷后试验钢基体组织主要为铁素体,部分铁素体中形成了大量的相间析出颗粒并具有良好的热稳定性,经650℃回火0.5 h后屈服强度提升明显,回火过程中铁素体基体和位错上形成了大量的纳米碳化物颗粒,这类碳化物的析出量大,尺度分布均匀,颗粒尺寸细小,是试验钢获得高强度最主要的原因。
The distribution, morphology and particle size of Ti-Nb-Mo microalloyed steel after tempering under two different cooling processes were observed and analyzed by means of SEM and TEM. Combined with the tensile test results and the hardness test results The effect of the change of nano-precipitated particles on the strength of test steel during tempering was studied. The results show that the microstructure of the test steel after hot-rolling is slab bainite, and the nano-precipitated phase is not formed after tempering at 650 ℃, resulting in a significant decrease of the strength of the test steel. However, Is ferrite, a large amount of intergranular precipitates are formed in some ferrite and have good thermal stability. After 0.5 h of tempering at 650 ℃, the yield strength increases obviously, and the ferrite matrix and dislocations are formed during tempering A large number of nano-carbide particles, such carbide precipitation amount, uniform size distribution, small particle size, is the main reason for the test steel to obtain high strength.