X90管线钢热影响区不同区域组织性能的研究

Research on Performance of Different Regional Microstructure for Heat Affected Zone of X90 Pipeline Steel

采用焊接热模拟技术（Gleeble-3500）、现代物理分析测试技术和金相显微组织分析技术,研究分析了X90管线钢焊接热影响区不同区域的强度、韧性和组织变化规律。研究表明,峰值温度为650℃时性能相比母材稍微有所提高；峰值温度为850~1100℃时材料韧性略有下降；当峰值温度为1300℃时,材料的韧性急剧恶化,成为焊接热影响区最薄弱环节。材料性能急剧恶化的原因是高温引起材料晶粒急剧长大以及粗大板条贯穿奥氏体甚至穿过晶界,同时由于奥氏体晶粒粗大,使得过冷奥氏体转变的稳定性增加且非平衡的低温转变产物增多,组织中的板条和板条间的M-A组元粗大,板条之间的缝隙和粗大的M-A为裂纹的扩展提供了机会,因此导致此区域韧性损失最为严重。

Using welding thermal simulation technique （Gleeble-3500）, modem physics analysis and testing yechnology and metallurgical microstructure analysis technology, the variation of intensity in different regions of X90 pipeline steel HAZ toughness and microstructure was analyzed. The results show that, when the peak temperature is 650℃, the performance of the alloy is slightly improved compared with the base material; when the peak temperature is 850-1100℃, the toughness decreases slightly. When the peak temperature is 1300℃, the toughness of the material deteriorates sharply, which becomes the weakest link in welding heat affected zone. The reason of the sharp deterioration of material performance is that high temperature causes grain growing up rapidly and bulky lath austenitic and even across the grain boundary. At the same time, due to austenite grain bulky, the stability of the super cooled austenite transformation and non-equilibrium low temperature transformation product increases, the strip in the microstructure and the M-A group between strip bulky. The gaps between the strip and massive M-A provides an opportunity for the propagation of the crack, so the tenacity loss in this area is most serious.