Studies Into New, Environmentally Friendly Ag-Cu-Zn-Sn Brazing Alloys of Low Silver Content

Abstract

The paper present selected results of the research conducted for elimination of toxic cadmium from silver based brazing alloys of Ag-Cu-Zn-Cd type. The investigations were conducted with nine new alloys of constant, low silver content (25%) and diversified copper (38.8-46%), zinc (19-32%) and tin (3-10%) contents. Tin was selected as potentially the best cadmium substitute basing on literature review and analysis of equilibrium systems.For examinations and tests a series of ingots in laboratory scale was manufactured, as well as some ingots in pilot scale for the selected, most promising alloys. Complex metallographic examinations of the brazing alloys samples produced in various conditions were made as well as analyses of their phase composition. Also mechanical properties of the samples both in ambient and in elevated temperatures were examined, and physical and technological properties and usability of the alloys were determined. The last stage of the study covered laboratory trials of brazing using the selected alloys.Basing on the results it can be said that there is a possibility to substitute selected cadmium containing silver-based alloys with environmentally friendly alloys of Ag-Cu-Zn-Sn type of relatively low silver content. Low range of melting point was reached, as preliminary assumed. Mechanical properties of the studied alloys strongly depend on temperature, and present limited plasticity in room temperature, while at high temperature (over 500• C) present superplasticity. The examined alloys show good spreadability and the brazing tests confirmed their good reactions both with copper and brass base in a wide temperature range.Keywords: cadmium, silver, environmentally friendly alloys, brazing alloys, mechanical properties, microstructure, phase composition W niniejszym artykule przedstawiono wybrane wyniki prac, których celem jest wyeliminowanie toksycznego kadmu ze srebrowych spoiw twardych typu Ag-Cu-Zn-Cd. Badaniami objęto 9 nowych gatunków stopów o stałej, niskiej zawartości srebra (25%) oraz zróżnicowanej zawartości miedzi (38,8-46%), cynku (19-32%) oraz cyny (3-10%). Cyna została wytypowana, na podstawie analizy literaturowej oraz układów równowagowych, jako potencjalnie najlepszy zamiennik kadmu.Wytworzono szereg wlewków w skali laboratoryjnej oraz dla wybranych, najbardziej obiecujących gatunków spoiw, wlewki w skali półtechnicznej przeznaczone do badań i prób. Przeprowadzono kompleksowe badania metalograficzne próbek spoiw wytworzonych w różnych warunkach oraz dokonano analizy składu fazowego. Wykonano także badania właściwości mechanicznych próbek zarówno w temperaturze otoczenia jak i podwyższonej oraz badania właściwości fizycznych, technologicznych i użytkowych. W ostatnim etapie pracy przeprowadzono laboratoryjne próby lutowanie przy zastosowaniu wybranych spoiw.Uzyskane wyniki badań pozwalają stwierdzić, że możliwe jest zastąpienie wybranych gatunków spoiw srebrowych kadmowych stopami ekologicznymi z grupy Ag-Cu-Zn-Sn o stosunkowo niskiej zawartości srebra. Uzyskano, zakładany we w...

Brazing filler metals

“…Interest was reignited when the health concerns of the then dominant cadmium-containing filler metals became known in the late 1970s, causing many companies to rapidly develop alternatives. Investigations conducted into various ternary and quaternary systems based on silver, copper and zinc, including: Ag-Cu-Zn-Ga [62], Ag-Cu-Zn-Ni [62], Ag-Cu-In [63], Ag-Cu-Sn [64] and Ag-Cu-Zn-Sn [62] eventually led to tin being selected as a suitable replacement for cadmium [65,66], with many manufacturers adopting filler metals of the Ag- Cu-Zn-Sn quaternary system. Eventually, legislation introduced in the European Union (Commission regulation (EU) No 494/2011) banned the sale of brazing filler metals with cadmium concentrations ≥ 0.01wt-% (barring specialist military and aerospace applications) [10].…”

Effects of In and Ga on Spreading Performance of Ag10CuZnSn Brazing Filler Metal and Mechanical Properties of the Brazed Joints

“…Compared with the brazing filler metals with high Ag, the low-Ag brazing filler metals have significant cost advantages, but the decrease in the content of Ag directly results in problems such as high melting points and poor flowability, which limit the application of low-Ag brazing filler metals in industries such as air conditioning, refrigerators, motors and instruments [9][10][11]. Some previous studies have revealed that any element that can decrease the melting temperature of the main element in the brazing filler metal can also decrease the melting point of the filler metal alloy [12][13][14]. The main elements in low-Ag brazing filler metal are Ag, Cu and Zn, with melting temperatures of 961.78 • C, 1083.4 • C and 419.53 • C, respectively.…”

Combined Effect of In and Ce on Microstructure and Properties of Ag10CuZnSn Low-Silver Brazing Filler Metals

“…Recently, researchers mainly improve the performance of the low-silver filler metals through "microalloying" [8], i.e., improving the performance of the filler metal by adding a small amount of an alloy element into a base filler metal. Based on the most widely used AgCuZn or AgCuZnSn low-silver filler metals, trace amounts of beneficial elements such as Ga, In, Mn, Ni, Li, and rare earth elements (RE) have been added to optimize the melting temperature, spreading performance, microstructure, and mechanical properties, to obtain low-silver filler metals with comparable properties to the traditional high-silver brazing filler metals [9].…”