预热温度和冷却速度对X80抗大变形管线钢焊接粗晶区性能的影响

Effect of Pre-heat Temperature and Cooling Rate on Properties in Coarse Grain Heat-affected Zone for X80 High Deformability Pipeline Steel

采用插销试验和热模拟技术研究了不同预热温度和冷却速度对X80抗大变形管线钢焊接粗晶区的冷裂纹敏感性及组织性能的影响。试验结果表明．随着预热温度的升高，X80抗大变形管线钢焊接粗晶区的临界断裂应力提高，抗冷裂纹敏感性能力增强；当预热温度达到1500C时，粗晶区的冷裂纹敏感性变得很小，断口形貌为韧窝状；随着冷却速度的增加，X80抗大变形管线钢焊接粗晶区的显微硬度升高．而断裂韧性由高到低，再由低到高，当冷却速度达到2-25℃／s时，粗晶区具有优良的断裂韧性：当进一步增大冷却速度时，由于板条马氏体的形成，粗晶区断裂韧性迅速降低。

Implant test and thermal simulating technology were used to study the effect of pre-heat temperature and cooling rate on cold cracking sensibility and structure and properties in coarse grain heat-affected zone （CGHAZ）for X80 high deformability pipeline steel. The experimental results showed that with the pre-heat temperature increasing, the critical fracture stress and the resistance of cold cracking in welding coarse zone were enhanced. When the pre-heat temperature reached 150℃ , the sensibility of cold cracking became so small, and the fracture surface presented toughness cavity. With the cooling rate increasing, the micro-hardness in CGHAZ became greater, but the fracture toughness was from high to low, and then from low to high. When the cooling rate achieved to 2 - 25 ℃/s, the CGHAZ showed excellent toughness. However, when the cooling rate was increased further, the fracture toughness reduced rapidly because of martensite formation.