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45钢摆臂轴套开裂失效分析
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摘要
45钢冷轧管摆臂轴套在压配实心轴过程中出现纵向穿透开裂现象。利用体式显微镜、扫描电镜、直读光谱仪、计光学显微镜和显微硬度等设备对开裂管的断口形貌、化学成分、显微组织和显微硬度进行观察与检验分析。结果表明:由于退火温度偏高管体晶粒较大且呈非等轴状态,加之冷轧时减径量过大导致组织晶粒畸变严重,存在较大的残余应力,在装载过程中装配应力与管体残余应力相互叠加而发生脆性开裂;另外,轴套内壁的块状翘皮与铁索体脱碳层均对管体的脆性开裂起到促进作用。通过改进工艺,采用调制处理(860℃淬火,保温30 min,500℃回火,保温2 h空冷),使得零件不仅满足工艺要求的同时其综合力学性能得到显著提高,避免了装配时管体开裂现象的发生。
45 cold-rolled steel made of arm bushings appear longitudinally through the crack in the press-fitting process solid shaft.By mean of stereo microscope,scanning electron microscopy,direct-reading spectrometer,optical microscope and micro-hardness tester and other equipment on fracture morphology,chemical composition,microstructure and micro-hardness of crack pipe is observed and test analysised.The results show that:Since the annealing temperature is high,rezulting in larger pipe grains was non-isometric,combined with cold rolling reduces diameter excessively cause grain serious distortion and exsit large residual stress in tube,,the superposition of the tube assembly stress and residual stress produce a brittle crack during the assembling.In addition,the inner wall of the sleeve block Qiao Pi and ferrite decarburization are all on the crack pipe body play a promotion.By improving technology,adopting quenching(quenching860'C,insulation30 min,tempering500℃,insulation 120 min,Cooling in Air)makes parts that are not at the same time meet the technical requirements of their mechanical properties has been significantly improved,avoid the assembly tube cracking phenomenon.
引文
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