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研究了不同淬火终冷温度对直接淬火配分超高强钢组织与力学性能的影响规律。结果表明:随淬火终冷温度升高,抗拉强度快速降低,屈服强度缓慢下降,冲击吸收能量先增加后降低,伸长率明显增加。直接淬火到马氏体相变区后空冷的组织为板条马氏体和残留奥氏体的复相组织。提高淬火终冷温度,马氏体板条粗化,残留奥氏体的含量增加,导致强度降低而塑韧性提高。淬火终冷温度为360℃时残留奥氏体的含量最高,为8.8%,但由于组织粗化,出现粗大板条马氏体,韧性降低。综合考虑,淬火终冷温度为320℃时具有最好的强度和塑韧性能的匹配,抗拉强度为1632 MPa,冲击吸收能量和伸长率分别为20 J和14.1%。
The effect of different quenching and finishing temperatures on microstructures and mechanical properties of direct quenched and fractionated ultrahigh strength steel was studied. The results show that with the increase of quenching temperature, the tensile strength decreases rapidly, the yield strength decreases slowly, the impact energy absorbs first and then decreases, and the elongation increases obviously. Direct quenching to martensitic transformation zone after the air-cooled lath martensite and retained austenite complex phase organization. Increasing the quenching and cooling temperature, martensite lath coarsening, the content of retained austenite increases, resulting in decreased strength and plasticity and toughness. When the final quenching temperature is 360 ℃, the content of retained austenite is the highest, which is 8.8%. However, due to the coarsening of the structure, coarse lath martensite appears and the toughness decreases. Taken together, the quenching final cooling temperature of 320 ℃ has the best strength and toughness of the match, the tensile strength of 1632 MPa, impact energy and elongation of 20 J and 14.1%, respectively.