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借助Gleeble1500热模拟试验机测试了含Nb和含Nb、Ti两种中碳微合金化钢的高温力学行为,分析了析出物、相变、动态再结晶对微合金化钢高温延塑性的影响。结果表明:试验钢种无第Ⅱ脆性区出现;含Nb钢第Ⅲ脆性区的温度范围为950~700℃,含Nb、Ti钢第Ⅲ脆性区的温度范围为900~725℃;微合金化元素Ti的加入可以细化奥氏体晶粒使含Nb微合金化钢高温塑性槽变窄、变浅;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。
The high temperature mechanical behavior of Nb and Nb and Ti medium carbon microalloyed steels was tested by Gleeble1500 thermal simulator. The effects of precipitates, phase transformation and dynamic recrystallization on high temperature ductility of microalloyed steels were analyzed. The results show that there is no second brittle zone in the test steel. The temperature range of brittle zone Ⅲ is 950-700 ℃, the temperature range of the third brittle zone of Nb and Ti steel is 900-725 ℃, The addition of Ti can refine the austenite grains and make the Nb-containing microalloyed steel high-temperature plastic trenches narrow and shallow. The precipitation of many and small precipitates along the grain boundaries and γ → α phase transformation are the third brittle zone micro-micro The main reason for the deterioration of ductility of alloyed steel at high temperature. The actual production by optimizing the second cooling zone water, the use of weak cold, micro-alloyed steel can effectively reduce the incidence of surface micro-cracks.