Brass heat treatment

Copper in pure form has found its significant use only in electrical applications. But with the continued study of copper, the addition of other metals called alloys was developed which enhanced its various properties. Now, different Copper-based alloys were widely used in different aspects of engineering and manufacturing. One of the best known and is widely used is the Copper-Zinc Alloy or Brass. Brasses according to Yu Lakhtin are “binary and multiple-component alloys based on copper with which the main component is zinc. ” Below is the phase diagram of Copper-Zinc Alloy at different Cu-Zi percentage and temperature. The commercial value of Brass is in its, and ? +? phases. At these two different phases, different characteristics were distinct. Their distinction according to Lukhtin (1979) depended on Zinc content from 48% to 50%. The single-phase or  -brasses were characterized by Lukhtin (1979) as “can be readily worked in both the hot and cold conditions” while the two-phase ? +? ’ brasses are “hot-worked at temperatures corresponding to the regions of the ? ’ or ? +? ’ phases. ” He also described? +? ’ brasses as “having higher strength and wear resistance but less ductility. According to him, “? +? ’ brasses were often alloyed with Al, Fe, Ni, Sn, Mn, Pb, and other elements. ” And “the addition of these alloying elements, except Ni, reduces Zi solubility in Cu and promotes the formation of ? -phase. ” Further he wrote, “the addition of alloying elements, except Lead, raised the strength and hardness of brass but reduced its ductility. Lead improved the machinability and gentrification properties of brasses.
” According to De Garmo, et. al, “Copper-based alloys are commonly identified through a system of numbers standardized by the Copper Development Association (CDA) which was adopted later by the American Society for Testing and Materials (ASTM), Society of Automotive Engineers (SAE), and the US government. ” Brasses were classified into wrought and casting brasses. According to Lakhtin (1979), “wrought brasses are used to make sheets, band stock, tubing, wire, and other semi-fabricated products; and casting brasses for making foundry castings. ” Owen Ellis (1948) further classified Brasses casting alloys into Red Brass, Leaded Red Brass, Semi-Red Brass, Leaded Semi-Red Brass, Yellow Brass, Leaded Yellow Brass, High-Strength Yellow Brass (Manganese Bronze), Leaded High-Strength Yellow Brass (Leaded Manganese Bronze), Silicon Brass, Tin Brass, Tin-Nickel Brass, Nickel Brass (Nickel Silver) and Leaded Nickel Brass (Leaded Nickel Silver). In his classification, Red Brasses consisted of 2%-8% zinc, less 0.
5% lead, and with tin less than the zinc; the same amount consisted the Leaded Red Brass except that lead is over 0. 5%; Semi-Red Brass consisted 8%-17% zinc, less than 6% tin, and less than 0. 5% lead; the same amount consisted the Leaded Semi-Red Brass except that lead is over 0. 5%; Yellow Brass consisted over 17% zinc, less than 6% tin, under 2% total of aluminum, manganese, nickel, iron, or silicon, and with less than 0. 5% lead; the same constitutes for Leaded Yellow Brass except for lead which is over 0. 5%; High-Strength Yellow Brass consisted of over 17% zinc, over 2% total of aluminum, manganese, tin, nickel and iron, under 0. 5% silicon, under 0. 5% lead and less than 6% tin; Leaded High-Strength Yellow Brass has the same constituents except that lead is over 0. 5%; Silicon Brass has over 0. 5% silicon and over 5% zinc; Tin-Nickel Brass has over 6% tin, over 4% nickel and with zinc more than tin; Nickel Brass has over 10% zinc, with nickel in amount sufficient enough to give white color, and with lead under 0.

5%; and Led Nickel Brass has the same but with a lead over 0. 5%. From these different compositions of Copper-Zinc Alloys, different properties were possessed which gave them different uses. Ellis (1948) also wrote that. The different required properties of Brass such as conductivity and hardness can be secured through heat treatment,” Below is a table of the different compositions, properties, and uses of common Copper-Zinc Alloys.
Reference

De Garmo, P., Black, J., Kohser, R. (1997).
Materials and processes in manufacturing. (8th Ed.). Upper Saddle River, NJ: Prentice-Hall International, Inc. Ellis, O. (1948).
Copper and copper alloys. Cleveland, Ohio: American Society for Metals. Lakhtin, Y. (1979).
Engineering physical metallurgy and heat treatment. (Weinstein, N., Trans. ). Moscow: MIR Publishers. Mayers, J. Visual library.
http://www.sv.vt.edu/classes/MSE2094_NoteBook/96ClassProj/pics/Cu_Zn1.gif.