304不锈钢钎焊板翅结构疲劳断裂机理分析

Analysis of fatigue fracture mechanism for brazed 304 stainless steel plate-fin structure

对304不锈钢板翅结构进行疲劳试验,分析疲劳断裂机理.疲劳裂纹从上钎角萌生,然后向翅片扩展,最终导致失效.在钎焊过程中,钎角处生成了较多的脆性化合物,且钎角处应力高度集中,使得裂纹从钎角萌生.疲劳裂纹的扩展经历了4个阶段:(1)裂纹在循环载荷作用下,在钎角脆性化合物启裂;(2)裂纹启裂后,在循环载荷作用下,沿钎角扩展;(3)裂纹跨越钎角和固溶体组织的界面,沿固溶体组织扩展;(4)裂纹跨越翅片和固溶体的界面,进入翅片区域扩展,直至完全断裂.

The fatigue tests were carried out to a 304 stainless steel plate-fin structure,and the fatigue fracture mechanism was analyzed.The crack is initiated at the top fillet,and then it propagates to the fin until failure.During the brazing,some brittle phases are generated in the fillet where the stresses are concentrated,which result in the initiation of crack at the fillet.The fatigue crack propagation is composed of four stages.The first stage is the crack initiation around the brittle phases at the fillet under the cyclic loading.The second stage is the crack propagation in the fillet metal.The third stage is that the crack crosses the interface between filler metal and solid solution and then propagates along the solid solution.The fourth stage is that the crack crosses the interface between solid solution and fin,and then it propagates along the fin until the failure.