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采用Gleeble 2000高温力学性能模拟实验机对不同冷却速率及不同拉伸速率下600 MPa级Al-Mo系冷轧双相钢高温热塑性进行了研究。结果表明,随拉伸应变速率增大,双相钢的高温热塑性明显提高;降低冷却速率,能显著提高双相钢高温区(t>1100℃)的塑性性能。为了避免铸坯在连铸过程中产生表面裂纹,矫直温度应保证在1050~1150℃范围内,同时二次冷却应采用弱冷水制度,以降低冷却速率。金相观察发现,沿奥氏体晶界呈网状分布的铁素体薄膜是造成两相区塑性低谷的主要原因,而AlN、FeO等析出相致使奥氏体单相区脆化。
The high temperature thermoplastic properties of 600 MPa Al-Mo cold-rolled dual-phase steel under different cooling rates and different tensile rates were studied by Gleeble 2000 high-temperature mechanical simulation machine. The results show that as the tensile strain rate increases, the high temperature thermoplasticity of the dual phase steel increases obviously. Reducing the cooling rate can significantly improve the ductility of the dual phase steel at high temperature (t> 1100 ℃). In order to avoid surface cracks during slab casting, straightening temperature should be guaranteed in the range of 1050 ~ 1150 ℃, while the secondary cooling should be weak cold water system to reduce the cooling rate. Metallographic observation shows that the ferrite films distributed along the austenite grain boundaries are the main reason for the plastic dullness in the two-phase region. However, the precipitation of AlN, FeO and other causes the austenite single-phase region to embrittle.