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研究了抗拉强度超过1000MPa的冷轧TRIP钢的热处理工艺对组织和力学性能的影响,并对其工艺进行了优化。结果表明,超高强TRIP钢在两相区的加热温度升高到820～840℃时,钢的抗拉强度下降而伸长率增加;贝氏体等温温度偏低(380℃)或者偏高(440℃)时,钢的伸长率较低。两相区加热温度对铁素体量的影响不大,降低贝氏体等温温度和延长等温时间都能增加贝氏体量。当贝氏体量高于38%时再增加贝氏体量来提高TRIP钢的强度效果不明显,可通过提高残留奥氏体量及其碳含量来提高力学性能。试验钢优化的热处理工艺:820℃×90s+420℃×240s;优化的组织含量配比:53%铁素体+36%贝氏体+11%奥氏体;优化的力学性能组合:抗拉强度1140MPa和伸长率22%。
The effects of heat treatment process on the microstructure and mechanical properties of the cold-rolled TRIP steel with a tensile strength exceeding 1000 MPa were studied and the process was optimized. The results show that the tensile strength of the steel increases with the increase of the heating temperature of the ultra-high strength TRIP steel in the two-phase zone from 820 ℃ to 840 ℃. The isothermal temperature of the bainite is low (380 ℃) or high 440 ℃), the steel elongation is lower. The heating temperature of the two-phase zone has little effect on the amount of ferrite. It can increase the amount of bainite by reducing the isothermal temperature of bainite and prolonging the isothermal time. When the amount of bainite is higher than 38%, increasing the amount of bainite to improve the strength of TRIP steel has no obvious effect. The mechanical properties can be improved by increasing the amount of residual austenite and its carbon content. Optimized heat treatment process for test steel: 820 ℃ × 90s + 420 ℃ × 240s; Optimized content ratio of steel: 53% ferrite + 36% bainite + 11% austenite; Optimized mechanical properties: Strength of 1140MPa and elongation of 22%.