铝合金电阻点焊的形核特点

Nucleation process of resistance spot welding of aluminum alloys

在铝合金的电阻点焊过程中 ,由于接触电阻具有随机性和分布不连续的特征 ,而且铝合金材料本身具有优良的导电、导热能力 ,这使得其点焊的形核过程具有独特的特点。文中采用数值模拟与试验研究相结合的方法对铝合金点焊形核过程进行了分析研究。研究结果表明 ,铝合金点焊的形核过程与低碳钢等材料的形核过程显著不同 ,它可以分为以下三个阶段 :随机形核阶段、扩展融合阶段和熔核增厚阶段。文中详细介绍了每个阶段的特点和规律。特别是在工频交流焊接的情况下 ,前两个阶段一般在第一个半波内就已经完成 ,因此第一个半波对铝合金点焊的焊接质量起着决定性作用。

Because the contact resistance in spot welding of aluminum alloys is random and non-continuous in distribution, and also the aluminum alloys have excellent electric and heat conduct ability, the nucleation process has the unique properties. In this paper, the nucleation process is studied by the numerical simulation and experiments, separately. The results indicates that the nucleation of aluminum alloy is significant different from the traditional spot welding process. This nucleation process could be divided into three stages; the random nucleation stage, the radial extension and merger stage and the thickness extension stage. The features of each stage are discussed. Especially, when welding with 50 Hz AC power source, the former two stages will be finished within the first half cycle and a initial nugget is formed. So the first half cycle is a key factor for the quality of the welding spot. Referring to these features of each stage, some suggestions are given for the control of the spot welding of aluminum alloys.