Machinability and manufacturing cost in low-lead brass

Today, commercially used brasses commonly contain 2 to 4 wt% lead. As the availability of low-lead and lead-free brass increases, there are environmental incentives for investigating the consequences of replacing the lead-containing brasses with lead-free equivalents. Generally, lead-free brass is expected to have a lower machinability than its lead-alloyed counterpart, implying a higher manufacturing cost. Thus, the aim of this study has been to quantify the added manufacturing cost by replacing a standard brass alloy with a low-lead alternative. This was done through a case study performed at a Swedish SME which replaced CuZn39Pb3 (3.3 wt% Pb) with low-lead CuZn21Si3P (< 0.09 wt% lead) for a select part. Since CuZn21Si3P is almost twice as expensive as CuZn39Pb3, the material cost was found to have a substantial influence on the manufacturing cost. Additionally, the lower machinability implied a longer cycle time and higher losses while machining CuZn21Si3P, resulting in a 77% overall increase in manufacturing cost when using the low-lead material. Arguably, the difference in material cost, and thus manufacturing cost, may decrease over time making production of low-lead and lead-free brass products a viable option, especially when considering the environmental incentive for decreasing the amount of lead in circulation.