铌对管线钢连续冷却过程相变温度和显微组织的影响

通过热模拟试验,研究了相同的工艺条件下不同Nb含量管线钢的组织及性能,分析了合金元素Nb对相变温度、显微组织、显微硬度的影响。结果表明,在同样工艺条件下,随着Nb含量的增加,过冷奥氏体连续冷却相变温度降低,尤其在冷速较低时(1℃/s),相变开始温度降低约70℃,结束温度降低100℃以上,显微组织中出现明显的粒状贝氏体及针状铁素体;Nb促进低温贝氏体组织的形成,并且细化晶粒,使材料的显微硬度升高。

Influence of Nb on transformation temperature and microstructure of pipeline steel during continuous cooling

Microstructure and properties of pipeline steels with different Nb contents under the same processes were studied by thermal simulation test.The effect of alloy element Nb on transformation temperature,microstructure and microhardness was analyzed.The results show that with the increasing of Nb content,the transformation temperature is decreased during continuous cooling of super-cooling austenite,at the low cooling rate such as 1 ℃/s,the initial transformation temperature is decreased about 70 ℃/s and final transformation temperature is decrease over 100 ℃/s.The granular bainite and acicular ferrite appear in microstructure obviously.Nb promotes low-temperature bainite microstructure and grain refinement,at the same time,the microhardness of the materials is also increased slightly.