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某发电公司磨煤机拉杆多次发生断裂。通过对最近的一次断裂拉杆现场调查和宏观断口分析,发现断裂发生在拉杆的补焊焊缝熔合线附近。将断裂拉杆和库存的两个备用拉杆进行了对照性的硬度检验和光谱检验,结果表明,三个拉杆执行的焊接工艺不统一,以致使焊缝的硬度和含Cr量有很大差别。进一步比较了断裂拉杆和已经产生裂纹的拉杆焊缝区的显微组织,发现在焊缝的热影响区粗晶区存在沿晶裂纹。综合分析表明,拉杆材料焊接性能差,焊后冷却速度过快,以致焊接应力过大。焊前预热及焊后热处理工艺不当是拉杆断裂的主要原因。
Pulverizer rod of a power generation company breaks several times. Based on the field investigation and macroscopic fracture analysis of the latest rupture rod, it was found that the rupture occurred near the welding line of the weld bead of the tie rod. The control of hardness test and spectrum test of the two tie rods of the rupture rod and the stock are carried out. The results show that the welding process performed by the three tie rods is not uniform, so that the hardness and the Cr content of the weld seam are greatly different. The microstructure of the weld zone of the tie rod and the rod that has cracked is further compared. It is found that there are intergranular cracks in the HAZ of the weld. Comprehensive analysis shows that the welding rod material poor performance, cooling too fast after welding, resulting in excessive welding stress. Welding preheating and post-weld heat treatment improper process is the main reason for rod rupture.