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研究了超低碳微合金钢880℃×1 h水淬、不同温度及时间回火后的显微组织及力学性能,结果表明:试验钢经淬火后的显微组织是由粒状贝氏体、板条状贝氏体和残留奥氏体所组成,屈服强度799 MPa,抗拉强度986 MPa,伸长率14.5%,屈强比0.81。随回火温度的升高,屈服强度和抗拉强度增大,并于300℃时达最大值,分别为949 MPa和1053 MPa,此时显微组织中开始有析出物产生,随着回火温度继续升高,析出物开始聚集并长大,屈服强度和抗拉强度逐渐降低,屈强比增加,在450℃处达到最大值后开始下降。试验钢的伸长率与回火温度的变化未发现有明显规律。适当延长于380℃回火的保温时间后,试验钢的显微组织类型无明显变化,但析出物有聚集长大现象,强度稍有降低,塑性略有增加。
The microstructure and mechanical properties of ultra-low carbon microalloyed steel after quenching at 880 ℃ for 1 h and tempering at different temperature and time were studied. The results show that the microstructures of the test steel after quenching are composed of granular bainite, Lath bainite and retained austenite, the yield strength of 799 MPa, tensile strength of 986 MPa, elongation of 14.5%, yield ratio of 0.81. With the increase of tempering temperature, the yield strength and tensile strength increase, reaching the maximum at 300 ℃, which are 949 MPa and 1053 MPa respectively. At this time, precipitates began to appear in the microstructure, The temperature continued to rise, the precipitate began to gather and grow, yield strength and tensile strength gradually decreased, yield ratio increased at 450 ℃ at the maximum and began to decline. Test steel elongation and tempering temperature changes found no obvious rules. Appropriate extension of the tempering at 380 ℃ holding time, the test steel microstructure type no significant change, but the phenomenon of the accumulation of precipitated growth, a slight decrease in strength, plastic slightly increased.