由于焊接冷裂纹的萌生与扩展具有时间延迟性，使得对冷裂纹的检测较为困难。采用声发射测试技术，对15 CrMoR材料制作的不同板厚和不同拘束焊缝长度斜Y型坡口对接焊接试件进行焊后自然冷却过程的声发射监测试验。试验结果表明：依据声发射撞击时间、幅值时间分布图，能够准确判别冷裂纹起裂点，确定试件焊后冷裂纹产生及扩展过程，且该过程具有焊接冶金过程、冷裂纹孕育过程、冷裂纹起裂点、微裂纹汇聚过程、主裂纹延迟扩展过程的“一点四过程”特征。

Time delay is one of the characteristics of crack initiation and crack propagation of welding cold cracking, which makes it more difficult to detect the cold cracking. In this paper, acoustic emission testing technique was used for the detection experiments on the natural cooling stage after welding for the inclined yshaped groove butt welding specimens, which were of different thickness and different restraint welding lengths. It can accurately distinguish the cold cracking initiation point according to hitstime and amplitudetime chart of acoustic emission parameters. The analysis result shows that crack initiation and crack propagation of welding cold cracking has a typical characteristic, which can be described as “one point four courses”, including the welding process，birth process, crack initiation point, microcracks convergence process and main cracking propagation process.