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利用Gleeble-3500热模拟试验机在温度为1000~700℃的条件下进行了热拉伸实验,结合应力-应变曲线、析出物、断口组织形貌的观察及分析,研究了冷速对铸坯高温塑性的影响。结果表明,冷速的提高会降低低碳微合金钢的高温塑性,使第Ⅲ脆性区间变窄;冷速从1℃/s增加至3℃/s对钢中含Nb、Ti析出物的形貌、尺寸和γ-α相变开始温度区间无显著影响。较低冷速更有利于晶间铁素体的长大;铁素体薄膜的长大是第Ⅲ脆性区间塑性改善的主要原因。
Thermal tensile test was carried out on Gleeble-3500 thermal simulator at a temperature of 1000-700 ℃. Combined with the observation and analysis of stress-strain curves, precipitates and fracture morphology, Effect of high temperature plasticity. The results show that the increase of cooling rate will reduce the high temperature ductility of low carbon microalloyed steel and narrow the third brittle section. The cooling rate increases from 1 ℃ / s to 3 ℃ / s, There was no significant effect of appearance, size and initial temperature range of γ-α transformation. Lower cooling rate is more conducive to the growth of intergranular ferrite; ferrite film growth is the main reason for the third brittle zone plasticity improvement.