Effect of Sb on microstructure and properties of high-tin and high-lead recycled brass ingots

Lead, as a crucial microelement in free-cutting brass, tends to aggregate due to equipment limitations during the direct melting process, forming large Pb-rich particles in the ingots, severely deteriorating the properties of brass ingots. Therefore, eliminating the agglomeration of lead in scrap brass has become an important research direction for preparing high-performance recycled free-cutting brass. In this paper, the Miedema model was utilized to simulate the elemental interactions of Sb in the Cu-Zn-Sn-Pb system at 1 080 ℃. Furthermore, experiments were conducted to profoundly investigate the evolution mechanism of Sb in recycled high-tin lead brass. The experimental results indicated that adding Sb to the brass altered the morphology of Pb from spherical to irregular shapes and effectively inhibited Pb aggregation by forming Cu₄Sb phases that encapsulated the lead. When the Sb content reached 0.25%, the inhibition of Pb agglomeration was most significant, and the ingot exhibited optimal performance. Additionally, Sb also reacted with Sn to form compounds that subsequently precipitated out. As the Sb content increased, these precipitated phases aggregated and gradually grew larger. This study provides an important theoretical basis for preparing high-quality free-cutting recycled brass.