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为了探明第3代汽车钢板坯角部横裂纹的产生机理,采用数学计算、物理测试、金相分析等方法,类比分析了第Ⅲ脆性区温度范围下钢的热膨胀系数、热塑性、相变特征以及第二相析出行为。结果表明,奥氏体晶界铁素体膜和AlN的析出是降低钢的高温延展性的内因,板坯边角部过冷是促发角部横裂纹产生的外因,而低温下的多次相变和(Mn,Fe)3C的析出会进一步提高钢的裂纹敏感性,由此提出了角部横裂纹的控制措施,实现了约250 t钢的全流程生产。
In order to find out the mechanism of the third-generation automotive slab corner crack, the thermal expansion coefficient, the thermomechanical property and the phase transition characteristic of the steel in the temperature range of the third brittle zone were analyzed by the methods of mathematical calculation, physical test and metallographic analysis And the second phase precipitation behavior. The results show that the precipitation of austenite grain boundary ferrite film and AlN is the internal cause of reducing the high temperature ductility of the steel. The superheat of the corner of the slab is the external cause of the transverse crack in the corner. However, Phase transition and the precipitation of (Mn, Fe) 3C will further increase the crack susceptibility of steel, and thus put forward the control measures of corner transverse cracks and realized the whole flow production of about 250t steel.