Using recycled bismuth-tin solder in novel machinable lead-free brass

Abstract

The aim of this work was to create and apply a recycled bismuth-tin (Bi-Sn) solder in novel machinable lead-free brass. The Bi-Sn alloys were obtained from a recycled solder used in the electronics industry to reduce cost and to partially solve electronic waste issue. The relationship between mechanical properties, microstructures and machinability of the brass were investigated. The results showed that a based lead-free Cu-38Zn-0.5Si brass without Bi-Sn alloy addition exhibited highest tensile strength, required the highest machining force and produced an undesirable long continuous chip type. An addition of 1-3 mass% Bi-Sn alloy resulted in significant decrease of both the tensile strength and the machining force. The chip formation changed from an undesirable long continuous chip to a discontinuous chip in moderate size. On the other hand, the addition of 4 and 5 mass% Bi-Sn alloy slightly increased the tensile strength and the machining force, the chip formation changed from a moderate chip size to a very short chip under every test condition. The lead-free brass with 3 mass% Bi-Sn alloy showed the best effective machinability as it required the lowest machining force and produced a short chip. Furthermore, the mechanical properties were about the same as those of the commercial EnviroBrass®III. Thus, the recycled Bi-Sn alloy can be used to improve the machining properties of lead-free brass and offers a possibility for new and better lead-free brass alloys.