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研究了含碳量为0.1%～0.4%的冷轧态中锰钢经650℃退火后微观组织和单轴拉伸性能的变化规律。利用SEM进行了组织形貌表征,采用XRD法测量了残余奥氏体量,通过拉伸试验机测试了钢的单轴拉伸性能。结果表明,冷轧态实验钢在退火过程中都发生奥氏体逆相变,获得具有一定量亚稳奥氏体的超细晶组织;随实验钢碳含量从0.1%增加到0.2%时,钢的抗拉强度(Rm)变化不大(约1000 MPa),而断后伸长率(A)从27%升高到43%时,强塑积(Rm×A)从28 GPa%提高到45 GPa%,而碳含量为0.4%时,钢的强度明显提高(约1200 MPa),但塑性却下降。分析认为,冷轧中锰钢中的碳有利于逆转变奥氏体的形成及稳定,但碳含量过高会形成大量碳锰化合物,不利于奥氏体的形成,从而降低塑性。亚稳奥氏体相的TRIP效应以及超细的晶粒尺寸是获得超高强度、高塑性及高强塑积的主要原因。
The variation of microstructure and uniaxial tensile properties of cold-rolled manganese steel with carbon content of 0.1% -0.4% after being annealed at 650 ℃ was studied. The morphology of the microstructure was characterized by SEM. The amount of retained austenite was measured by XRD. The uniaxial tensile properties of the steel were tested by tensile testing machine. The results show that the as-cast austenite phase transformation occurs in the cold-rolled experimental steel during annealing, and the ultrafine-grained microstructure with a certain amount of metastable austenite is obtained. With the increase of carbon content from 0.1% to 0.2% The tensile strength (Rm) of the steel changed little (about 1000 MPa), while the elongation at break (A) increased from 27% to 43%, the plastic product (Rm × A) increased from 28 GPa to 45 GPa%, while the carbon content of 0.4%, the steel strength increased significantly (about 1200 MPa), but the plasticity decreased. The analysis shows that the carbon in cold-rolled medium manganese steel is beneficial to the formation and stabilization of reverse-transformed austenite, but the high carbon content will form a large amount of carbon-manganese compounds, which is not conducive to the formation of austenite and thus reduce the plasticity. The TRIP effect of metastable austenite phase and the ultrafine grain size are the main reasons for obtaining super high strength, high ductility and high strength plastic area.