铌对管线钢奥氏体分解的影响

The Effect of Niobium on Austenite Decomposition in Line Pipe Steels

为了研究铌对管线钢奥氏体分解的影响规律,采用激光超声波技术对低Nb钢和高Nb钢的原始晶粒生长行为进行测量,并对不同冷却速率、钢中不同Nb状态(固溶或析出)和不同奥氏体晶粒尺寸下的试样进行了光学金相和显微硬度检测,研究了在连续冷却过程中奥氏体晶粒尺寸、冷却速率和Nb状态的函数关系。结果表明, Nb的溶解对奥氏体分解有很强的影响,其抑制了贝氏显微组织细化的转变温度,增加了HAZ粗晶区的硬度,特别是在大奥氏体晶粒尺寸及钢中Nb含量较高的情况下,其影响效果更加明显。

In order to study the influence of niobium on the austenite decomposition of pipeline steel,the laser ultrasonic technique was used to measure the original grain growth behavior of two steels with a low and high Nb content.The metallographic microhardness tests were carried out on samples with different cooling rates,different Nb states(solid solution or precipitation)and different austenite grain sizes.At the same time,the functional relationship between austenite grain size,cooling rate and Nb state during continuous cooling was also studied.The results show that the dissolution of Nb has a great influence on the austenite decomposition,which inhibits the transformation temperature of bainite microstructure refinement and increases the hardness of the HAZ coarse grain region,especially when the austenite grains are coarse and Nb in steel.When the content is high,the effect is more obvious.