Cu/Ni异种金属丝深熔钎焊中接触电阻的影响因素研究

Study on Influence Factors of Contact Resistance in Penetration Brazing of Cu/Ni Dissimilar Metal Wires

电极与石墨棒的接触电阻是影响Cu/Ni基异种金属丝深熔钎焊中稳定可靠焊接热的关键问题。建立了电极与石墨棒的接触电阻数学模型,通过试验研究了电极结构、接触压力及石墨棒的表面形貌等因素对接触电阻的影响规律。结果表明,在相同接触压力下圆弧槽电极的接触电阻较V型槽电极的大,但圆弧槽电极与石墨棒的接触面积大于V型槽电极与石墨棒的接触面积,造成圆弧槽电极通过石墨棒的电流密度小于V型槽电极通过石墨棒的电流密度,与圆弧槽电极接触的石墨棒发热效率比与V型槽电极接触的石墨棒低。在相同电极结构下,随着接触压力的增加接触电阻下降。在相同接触压力、V型槽电极下,普通石墨棒的表面形貌粗糙,初始接触电阻大于精细石墨棒;普通石墨棒与电极的接触点少于精细石墨棒,导致电流密度大,发热效果优于精细石墨棒,但其烧蚀程度大,使用寿命短。

The contact resistance between the electrode and graphite rod is the most important factor that affects the welding heat of penetration brazing of Cu/Ni dissimilar metal wires. The mathematical model of the contact resistance between the electrode and graphite rod was built, and the effects of the electrode structure, contact pressure, and graphite rod＇s surface morphology on the contact resistance were investigated by tests. The results show that under the same contact pressure, the contact resistance of the arc groove electrode is bigger than that of V type groove electrode. However, due to the contact area between the arc groove electrode and graphite rod is bigger than that of the V type groove electrode and graphite rod, the current density through the graphite rod of the arc groove electrode is less than that of the V type groove electrode, and the heating efficiency of the graphite rod contacing with arc groove electrode is lower than that contacing with V type groove electrode. Under the same electrode structure, the contact resistance decreases with the increase of contact pressure. Under the same contact pressure with the V type groove electrode, the surface morphology of the common graphite rod is rough, and the initial contact resistance is bigger than that of the fine graphite rod. The contact point of the common graphite rod and the electrode is less than that of the fine graphite rod, which results in large current density, and the heating effect is better than than that of the fine graphite rod. But the ablation degree of the common graphite rod is big and the service life is short.