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在实验室研究了回火温度对C-Si-Mn双相钢力学性能与显微组织的影响。力学性能测定结果表明,250℃以下的低温回火,对改善双相钢的伸长率具有良好作用,但是其它力学性能的变化不明显。高于300℃的高温回火对改善双相钢的延性作用不大,但会引起双相钢的屈服强度升高,抗拉强度、加工硬化与烘烤硬化值降低,使双相钢性能恶化。扫描电镜与透射电镜的观察结果表明,低温回火双相钢的显微组织变化不明显,马氏体为板条状,马氏体前沿的铁素体基体中分布着大量的可动位错,高温回火双相钢的显微组织则有较大变化,马氏体分解,边界变得模糊,岛内出现碳化物颗粒,铁素体中的位错密度减小,位错线附近出现粗大的析出物。高温回火后,马氏体的分解软化以及铁素体中位错密度减小是导致双相钢性能恶化的主要原因。
The effects of tempering temperature on the mechanical properties and microstructure of C-Si-Mn dual-phase steel were studied in laboratory. Mechanical properties of the results show that the low temperature below 250 ℃ tempering, to improve the elongation of dual-phase steel has a good effect, but the other changes in mechanical properties is not obvious. High temperature tempering above 300 ℃ has little effect on improving the ductility of dual phase steel, but it will cause the yield strength of dual phase steel to increase, and the tensile strength, work hardening and bake hardening value will be reduced and the dual phase steel will deteriorate . Scanning electron microscopy and transmission electron microscopy observations show that low-temperature tempering duplex steel microstructure changes are not obvious, the martensite lath-like, martensite front ferrite matrix distribution of a large number of mobile dislocations , The microstructure of the high temperature tempering duplex steel is greatly changed, the martensite decomposition, the boundaries become blurred, carbide particles appear on the island, ferrite dislocation density decreases near the dislocation line Coarse precipitate. After tempering at high temperature, the decomposition and softening of martensite and the decrease of dislocation density in ferrite are the main reasons leading to the deterioration of dual phase steel.