铝合金与不锈钢钎焊性能影响因素的研究

Influence factor of brazability of aluminum alloys and stainless steel

本研究使用Al-Si钎料对各种铝合金与不锈钢在电阻炉中实施了钎焊。对接头成败、钎焊界面间铝合金、钎料和钎剂成分的元素扩散状况和组织变化进行了EDX,EPMA分析;并用XRD检测了钎剂对不锈钢的影响;还根据试验结果对熔融钎料层的消失即等温凝固时间进行了理论推定;进而将推定结果和Al-Si与Al-Zn系重叠扩散的理论解析进行了对比考察、验证。其结果为:铝合金与不锈钢的空气中钎焊要得到强固的接头是很困难的;使用钎剂去除不锈钢的氧化膜并使其产生湿润所需的时间比铝合金要长;接头不能形成的主要原因是钎料在对不锈钢产生润湿前,先与铝合金产生润湿、反应后急速等温凝固;而此等温凝固是由钎剂中的Zn扩散到钎料及铝合金母材中所致。

It was well known that was difficulty for brazing of aluminum alloys to stainless steel in the air. Brazing of various aluminum alloys to stainless steel had been carried out in the air using Al-Si brazing filler with flux by electric furnace. the outline of the braze ability and the structure and element diffusion behavior of aluminum alloys, brazing filler and flux for brazed area of joints or no joint were examined by EDX, EPMA. The influence of flux to the stainless steel was detected by XRD. Based on measured experimentally, the disappearance time of the molten brazing layer that was the isothermal solidification time was estimated by the theoretical calculation. The comparison and verify were carried out for the estimation result and the numerical analysis in case of Al-Si and Al-Zn binary system overlapping. As the result, it was difficult to obtain joints between dissimilar metals of aluminum alloys to stainless steel in the air. The cause of joints could not form was clarified as that was reaction and rapidly solidified isothermally between brazing filler and aluminum alloy before the wetting occurrence of brazing filler to stainless steel. The needs time to make the stainless steel surface wet as eliminate the oxide films by flux was longer than aluminum alloys that. The rapidly isothermal solidification of brazing filler was due to the invasion and diffusion of Zn into the brazing filler and aluminum alloy base metal from the flux.