借助gleeble1500热模拟试验机测试了含Nb和含Nb、Ti两种典型中碳微合金化钢的高温力学行为,分析了析出物、相变、冷却速率、动态再结晶对微合金化钢高温延塑性的影响。结果表明：实验钢种无第Ⅱ脆性区出现；含Nb钢第Ⅲ脆性区的温度范围约为950～700℃，含Nb、Ti钢第Ⅲ脆性区的温度范围约为900℃～725℃；析出物沿晶界多而细小的析出和γ→α相变是第Ⅲ脆性区微合金化钢高温延塑性变差的主要原因。实际生产中通过优化二冷区水量，采用弱冷，可以有效降低微合金化钢表面微裂纹的发生率。
High temperature mechanical behaviors of Nb and Nb、Ti containing steel were tested by Gleeble1500 thermal simulation testing machine. Meanwhile, influences of precipitate, phase change, cooling rate and dynamic recrystallization on hot ductility of the micro-alloy steel were also analyzed utilizing Gleeble. The results demonstrate that: the embrittlement region Ⅱ does not exist in Nb nor Nb、Ti containing steel. The temperature range of ductility region Ⅲ is about 950～700℃ in Nb containing steel and 900～725℃ in Nb、Ti containing steel respectively. Precipitation along the grain boundaries and during γ→α phase transformation are main factors which lead to a decrease on hot ductility of Nb and Nb、Ti containing steel. In the practice process the incidence of surface micro-cracks in micro-alloying steel can be reduced dramatically by decreasing specific water rate in secondary cooling zone.
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