材料期刊网

高温铝钎剂基本上可以分为:覆盖剂、去膜剂和界面活性剂三个组成部分。研究了15个不同组分和组成的覆盖剂,发现LiCl-SrCl_2,LiCl-NaCl-KCl与CaCl_2-NaCl-KCl依次为良好的覆盖剂体系,排除了碘化物和溴化物使用的现实性;去膜剂由含氟的化合物构成.详细筛选了周期系中所有可能用作界面活性剂的金属氯化物,研究了它们对纯铝、Al-Mg2.8和Al-Cu4.9-Mg1.8等铝合金的作用特性,发现TlCl对各种母材都有突出的活性作用。 铝钎焊过程中钎剂失效主要是由于活性的液态金属层消失。ZnCl_2最易失效,而TlCl最不易失效。针剂中絮状物主要是由LiCl脱水过程中产生的水解产物OH~-所造成。 提出了适用于不同铝合金的最佳钎剂组成。

The flux for aluminum brazing is constituted by three agents, e.g. the cov-ering, the oxide-film removal and the interfacial activating agent. Fifteen systemsof various covering agents were examined based on the spreading area of filler onparent metal. The systems of (Li+Sr)Cl, (Li+Na+K)Cl and (Ca+Na+K)Cl werefound to be suitable, those containing iodides and bromides, however, were worstbecause of deposition during melting. The oxide-film removal agents tested werefluorides or fluorine-containing complex compounds, in which LiF was the best.Many chlorides adaptable as interfacial activating agents were scanned. TlCl wasfound to be suitable for all the three metallic base plates tested, e.g. the pure al-uminum, the Al-Mg2.8 and the Al-Cu4.9-Mg1.8. ZnCl_2 and CdCl_2 were good forpure aluminum. BiCl_3 and PbCl_2 were rejected because of causing "dirt" on theparent metal. The most effective content of interfacial activating agent was foundto be about 3 mol%. Owing to the absence of a liquid-metal activated layer, theaction of the flux would not be apparent during brazing. In such a case, ZnCl_2acted the worst, and TlCl the best. The non-fusible loose-cotton-like clusters form-ed in the pool of molten fluxes may be resulted from the LiCl dehydration pro-cess. For convenience, suitable constituents of fluxes for aluminum brazing arelisted in the text.