中国古代铅锡焊料的分析

Analysis of ancient Pb-Sn solder in China

用金相显微镜、扫描电子显微镜及X射线能谱分析仪、X射线衍射分析仪对江苏淮阴高庄战国墓及四川绵阳石塘乡东汉墓出土的四件焊料样品进行检测分析.结果表明,焊料为锡铅二元合金.其中从一件铜器腿中发现的游离焊料,铅的平均质量分数为68.1%,锡21.4%,组织由铅锡α相和β相组成.而在与两件铜器上焊接点接触的焊料,不仅含有锡、铅,还含铜,铜的质量分数分别为1.6%和3.8%.在铜器与焊料接触点截面样品上,有铜锡η相(Cu6Sn5)由焊料与青铜本体相接触的界面向焊料深入,呈一个个相连的小扇贝形凸起状.在焊料基体上也存在块状η相.其生成原因是在焊接时熔化成液相的铅锡焊料与基材青铜接触,基材中的铜溶解在熔融的焊料中与锡发生反应,在界面处和焊料内部生成铜锡金属间化合物.

Four ancient solder samples were examined by using optical microscope, scanning electron microscope （SEM）, X-ray energy dispersive spectrometry （EDS）, and X-ray diffraction spectrometry （XRD）. Among these samples, three were unearthed from the tombs of the Warring State period （the 5th-3rd centuries BC） at Gaozhuang, Huaiyin, Jiangsu Province of China and one from the tomb of the Eastern Han Dynasty （the ist-3rd centuries AD） at Shitang, Mianyang, Sichuan Province of China. The results show that all the solders are made of Pb-Sn alloys. One of the Gaozhuang samples contains 68. 1% Pb and 21.4 % Sn, and its mi- crostructure consists of α and β phases. This sample was taken from a bronze Jian vessel leg, but it seems to have not been involved in welding. The other two samples that were clearly involved in welding contain not only Pb and Sn, but also Cu, and the Cu contents are 1.6 % and 3.8 %, respectively. It is pointed out that Cu in these two solder samples resulted from the dissolution of Cu into the molten Pb-Sn solder. At the interface between the liquid solder and the bronze substrate, a scallop-type layer of Cu-Sn inter-metallic compound （Cu6Sns） formed and grew. Some irregular pieces of Cu6Sn5 also formed within the bulk solder.