某工程用板式散热器在运行过程中,不锈钢波纹换热片发生了泄漏故障。为此,利用宏观形貌分析、化学成分分析、金相显微组织检测、扫描电子显微镜(SEM)微观形貌观察与X射线能谱分析(EDS)等方法对波纹换热片的泄漏原因进行了综合性分析。结果表明:波纹换热片表面的高温氧化膜特别是“牛顿环”中心的粗糙度较大,且该点为冷冲压槽的凸起处,位错密度较高;在长期运行过程中,Cl-于该位置不断聚集,形成孔蚀核,并最终诱发孔蚀。此外,在换热片基体中冷冲压残余应力的作用下,还会触发局部区域的应力腐蚀。随着孔蚀及应力腐蚀程度的不断加剧,波纹换热片的厚度逐渐减薄,并最终引发泄漏。建议对Cl元素来源和高温氧化膜的形成原因进行排查,从而制定针对性的改进措施。
During the operation of plate type radiator used in a certain project, the stainless steel corrugated heat exchanger plate experienced a leakage fault. In this paper, the leakage causes of corrugated heat exchanger plate were comprehensively analyzed by means of macro morphology analysis, chemical composition analysis, metallographic microstructure examination, observation of microscopic morphology by scanning electron microscope (SEM) and X-ray energy dispersive spectroscopy (EDS). Results indicated that the roughness of the high temperature oxidation film formed on corrugated heat exchanger surface, especially the center of Newton's ring, was large. This point was also the bulge of the cold stamping groove with high density of dislocations. And this point was the protrusion of the cold stamping groove, with a higher dislocation density. During the process of long-term operation, Cl- continuously accumulated at this location, forming pitting nuclei and ultimately inducing pitting. In addition, under the effect of the cold stamping residual stresses remained in the heat exchanger substrate, the stress corrosion in local areas would also be triggered. With the increasing degree of pitting corrosion and stress corrosion, the thickness of the corrugated heat exchanger plate was gradually decreased and ultimately led to leakage. It was suggested that the source of Cl element and the formation causes of high-temperature oxide films should be investigated, then the targeted improvement measures could be developed.
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