Comparative study on the machinability of lead-free brass

Lead is a heavy metal which is toxic even at low exposure levels. Although the amount of lead used in industry is steadily declining, it still constitutes a common alloying element for most conventional brass varieties. Today, conventional brasses contain roughly 3 wt % lead. One of the main incentives for using lead as an alloying element is that it has a markedly positive effect on the machinability of the workpiece material. However, as an increasing amount of lead-free brasses are becoming commercially available and future legislative actions could be expected, even further limiting the use of lead as an alloying element, there is a renewed interest in evaluating the machinability of these new lead-free materials. The current article focuses on evaluating the machinability of the commonly used, lead-containing, CuZn39Pb3 brass as compared to the commercially available, lead-free alternative CuZn21Si3P. An improved understanding of the difference in machinability was obtained by comparing the properties and behavior of these two materials in machining. For instance, it was noted that the tool wear is significantly higher while machining CuZn21Si3P as compared to CuZn39Pb3 under similar conditions. This can, to a certain extent, be counteracted through the use of inexpensive tool coatings, making lead-free brass a viable option for commercial production.