The content of lead-free free free-cutting hollow brass bars shall not be greater than 0.002010. Bismuth, tellurium, sulfur and other elements are extremely harmful to other copper alloys. Strict control must be exercised in production to prevent the mixing of raw materials, used materials, lining materials and auxiliary tools. Hollow brass bars have high conductivity, and can prevent the switch from bonding, improve its working life and ensure safe operation. Bi has little effect on the thermal conductivity and electrical conductivity of copper. The contact copper of vacuum switch can contain 0.7%~1.0% Bi. Generally used in quenching and processing state, no tempering is needed to avoid precipitation of Cu2 Te along grain boundary and brittle material. Copper containing 0.06%~0.7% Te has been applied in industry. Bi, Te and other alloying elements in copper have similar characteristics, forms and lead. They are basically insoluble in copper. They exist at grain boundaries as free particles. After sequential processing, they disperse in the copper matrix, play the role of lubrication and friction reduction, make the alloy chips fragile and easy to arrange, and ensure the smooth surface of the products. In some special applications, such as electrical contacts requiring high conductivity, high copper alloy series is used. As far as processing function is concerned, the processing function of this kind of alloy is not very good, especially for high copper alloy, its composition control and processing function are not easy to guarantee. In lead-free free free-cutting brass bar, the addition of zinc increases its solubility to a certain extent, and improves its composition and processing function. Trace (0.003 010) selenium and tellurium (0.00050/0-0.003%) significantly reduce the weldability of copper rods. Lead-free free free-cutting brass rod is a replacement product of free-cutting lead brass rod, because lead is harmful to human body. Lead-free free free-cutting brass rod is replaced by non-toxic third alloy element. The lead-free brass rod alloying system has been developed at present: Cu-Zn-Bi, Cu-Zn-Te, Cu-Zn-Bi-Te. At the same time, some research has been done on high-copper alloy systems such as Cu-Bi, Cu-Te, Cu-C and Cu-S. Because of the factors such as machinability, machinability and cost-effective ratio of the products, the main practical application at present is the copper-zinc-Bi lead-free free free cutting brass rod. The solubility of tellurium in solid copper is very small. It exists as dispersed particles of Cu2 Te. It has little effect on the conductivity and thermal conductivity of copper, but it can obviously improve the cutting mechanism of copper. Bismuth forms eutectic with copper at 270 C. Bismuth distributes at the grain boundary of copper as a thin film, which severely reduces the processing function of copper. The solubility of bismuth in copper is very small, and it is only 0.01% at 800 C.