ZGM113G型中速辊式磨煤机拉杆断裂分析

Analysis on Tension Rod Rupture of ZGM113G Medium Speed Coal Pulverizers

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。

Tension rods in a power generation company were pulled off several times.Based on the fracture site investigation and macro-rod fracture analysis,the welding rod fracture occurred in the vicinity of the weld fusion line.The pulled off tension rod was compared with two spare rods by hardness test and spectral test.The results show that the implementation of the three rod＇s welding process is not uniform,which can make hardness and chromium element content of the weld zone vary widely.The fracture rod has cracks in the microstructure of weld zone,intergranular cracks exists in the coarse grain zone of the weld heat affected zone.Comprehensive analysis shows that the welding rod material has poor welding performance,if the cooling rate after welding is too rapid,then the welding stress can be too large.Preheating and post weld heat treatment inappropriate is the main reason for tension rod fracture.