预镀层不锈钢/铝异种金属高频感应钎焊接头界面及力学性能分析

Study on interfacial structure and mechanical properties of high frequency induction brazed joint of aluminum alloys to pre-coated stainless steel

关键词:  铝/钢异种金属  高频感应钎焊  界面反应层  抗拉强度

Key words:  Al/steel dissimilar alloys  high frequency induction brazing  interfacial reaction layer  tensile strength

摘要:

文中通过热浸镀一层纯铝到不锈钢表面，再对0Cr18Ni9不锈钢和LF21铝合金采用高频感应钎焊.当热浸镀时间从10 s增加到50 s时，镀层厚度从7 μm增加到20 μm，反应层由FeAl₃向Fe₂Al₅发生转变.在热浸镀温度为750℃，浸镀时间为10 s时，镀层成型最好，高频感应电流为270 A，加热时间30 s时，抗拉强度达到167.12 MPa，比不浸镀的接头强度高63.8%.主要是因为镀层限制钢中的Fe原子和Al-Si钎料中的Al，Si原子的相互扩散，在热浸镀不锈钢与铝合金反应中使Fe₂Al₅转化为Fe（Al，Si）₂固溶体而未形成5-Al₈Fe₂Si化合物，降低了界面上硬脆化合物的含量，力学性能随之提高.

Abstract:

The high frequency induction brazing of LF12 aluminum alloy to 0Cr18Ni9 stainless steel was successfully performed with a layer of hot-dip pure aluminum on the surface of stainless steel. The results showed that the thickness of clad layer increased from 7 μm to 20 μm, and FeAl₃ turned to Fe₂Al₅ when the time of hot-dipping increased from 10 s to 50 s. The coated layer formed well when the time is 10 s and the temperature is 750 ℃ during the hot-dipping process. The optimum welding current is 270 A and the holding time is 30 s. Under the optimum welding conditions, the maximum tensile strength of brazing joint is 167.12 MPa which is about 63.8% higher than the joint without hot-dip pretreatment. In the brazing process, Fe₂Al₅ turns to Fe(Al,Si)₂, instead of the formation of τ-Al₈Fe₂Si because the coating layer limits the inter-diffusion of Fe atoms in steel and Al, Si atom in aluminum alloy. The increase of the tensile strength of the joint is due to the decrease of brittle compounds like τ-Al₈Fe₂Si.