氧含量对银基粉状钎料熔化及钎焊特性的影响

Effects of Oxygen Content on the Melting Characteristics and Brazing Mechanical Properties of Silver-based Powder Brazing Filler Metals

摘要:

在钎焊过程中，粉状钎料有着广泛的应用，不仅仅可以用于复杂工件，还可以用在补焊和修复未焊透等方面。除此之外，粉状钎料可以用在自动化过程中，有着广阔的前景。由于大的表面能，银基粉状钎料非常容易吸氧，但没有人对氧含量对银基粉状钎料特性的影响开展系统研究。本文通过第一性原理计算和试验等多种分析方法来研究氧含量对熔化特性以及钎焊接头力学性能的影响。研究结果表明，钎料的表观活化能随着钎料中氧含量的增加而增加，导致了熔化时间增加。随着钎料中氧含量的增加，钎焊接头的抗拉强度呈现非线性下降，为了确保钎料的良好性能，应该将钎料中的氧含量控制在200ppm以下。根据疲劳试验结果，氧元素引起的钎焊缺陷被认为是裂纹的源头，我们的研究提供了氧含量对银基粉状钎料钎焊过程影响的详细机制。

Abstract:

In the brazing process, the powder brazing filler metal is widely used. It is often used not only in the production of some complicated workpieces but also in the process production of repair welding and incomplete penetration. Besides, it can also be used in automated production, with a promising future. Due to their large specific surface area, the silver-based powder filler metal easily suffers an increase in oxygen content. However, few systematic studies have been conducted on the effect of the oxygen content on the performance of silver-based powder brazing filler metals. In this study, both density functional theory (DFT) calculations and a variety of analytical methods were employed to study the effects of increased oxygen content on the melting characteristics and brazed joint mechanical properties. The results revealed that the apparent activation energy of the filler metal increased with the increasing oxygen content, resulting an increased melting time. The tensile strength of the brazed joints decreased nonlinearly with the increasing oxygen content in the filler metal. To ensure good performance of brazing filler metals, the filler metal oxygen content should be controlled to be less than 200 ppm. According to the fatigue testing results, the oxygen induced brazing defects severed as a source of fracture cracks. Our studies provided a detailed mechanism of the oxygen effects on the brazing process of the silver-based powder filler metals.