Nb、Mo含量对高钢级管线钢组织性能的影响

Effect of Nb and Mo Content on Microstructure and Mechanical Properties of High Strength Pipeline Steel

采用Gleeble-1500热模拟试验机并结合微观组织和力学性能测试,分析了不同铌、钼含量对管线钢的组织、力学性能和CCT曲线的影响。结果表明:随钼的质量分数增加,针状铁素体的含量增加,并且出现了M-A组织。铌在钢中可抑制奥氏体的再结晶,保持变形效果从而细化铁素体晶粒,得到细小的贝氏体组织,并且铌含量的增加使得管线钢强度和硬度都相应增大,冲击韧度降低。在连续冷却转变过程中,钼元素的加入使相变点温度降低,在相同的冷却条件下容易发生贝氏体转变,并使其CCT曲线向右移。而铌元素的加入增大了过冷奥氏体的稳定性,相变点温度降低,并且推迟珠光体的转变。

Through Gleeble-1500 thermal mechanical simulation and microstructure and mechanical properties test, the effects of Mo and Nb content on microstructure, mechanical properties and CCT curves of the pipeline steel were analyzed. The results show that, with the increase of Mo content, the acicular ferrite＇s content increases, and M-A microstructure appears. Nb may suppress austenite recrystallization in the steel, maintains the distortion effect and fines ferrite grain, which can obtain the tiny bainite microstructure. With the increase of Nb content, the strength and hardness of the pipeline steel increase, but the impact toughness decreases. In the continuous cooling transformation, Mo adding reduces the temperature of phase transformation point, makes the bainite transformation easier under the same cooling condition, and causes CCT curves to move toward right. But Nb adding increases the under-heating austenite stability, reduces the temperature of phase transformation point and postpones the transformation of pearlite.