How much do you know about the classification of brass?!

What is brass?
　　Brass is an alloy composed of copper and zinc. If brass consists solely of copper and zinc, it is referred to as "ordinary brass." When brass is an alloy made up of two or more elements, it is called "special brass," such as copper alloys containing lead, tin, manganese, nickel, iron, and silicon.
　　Classification of Brass
　　Depending on the types of alloying elements contained in brass, brass is divided into two categories: ordinary brass and special brass.
　　01 Ordinary Brass
　　When the zinc content is less than 39%, zinc dissolves in copper to form a single-phase α phase, known as single-phase brass. This type of brass has good ductility and is suitable for both cold and hot pressure working. When the zinc content exceeds 39%, in addition to the single-phase α phase, a β solid solution based on copper and zinc also forms; this is referred to as two-phase brass. The β phase reduces ductility but increases tensile strength, making it suitable only for hot-pressure working. If the mass fraction of zinc continues to increase beyond this point, the tensile strength will decline, rendering the alloy unusable.
　　Brass alloys with zinc content below 36% consist of a solid solution and exhibit excellent cold-working properties. For example, brass containing 30% zinc is commonly used to manufacture cartridge cases—often referred to as "cartridge brass" or "73 brass." Brass alloys with zinc content between 36% and 42% also consist of a solid solution; among these, the most widely used is 64 brass, which contains 40% zinc.
　　Generally, single-phase brass is used for cold deformation processing, while duplex brass is used for hot deformation processing.
　　02 Special Brass
　　To enhance the corrosion resistance, strength, hardness, and machinability of brass, small amounts (typically 1% to 2%, occasionally up to 3% to 4%, and in rare cases as high as 5% to 6%) of elements such as tin, aluminum, manganese, iron, silicon, nickel, and lead are added to copper-zinc alloys, forming ternary, quaternary, or even quinary alloys—known as complex brasses, also referred to as special brasses.
　　(1) The microstructure of complex brasses can be estimated based on the “zinc equivalent coefficient” of the elements added to the brass. This is because the addition of small amounts of other alloying elements to a copper-zinc alloy typically results only in a shift—either to the left or to the right—of the α/(α+β) phase region on the Cu-Zn phase diagram. Consequently, the microstructure of special brasses generally corresponds to that of ordinary brasses with either increased or decreased zinc content. For example, the microstructure of a Cu-Zn alloy containing 1% silicon is equivalent to that of a Cu-Zn alloy with 10% more zinc. Therefore, silicon has a “zinc equivalent” of 10. Silicon has the highest “zinc equivalent coefficient,” causing the α/(α+β) phase boundary in the Cu-Zn system to shift significantly toward the copper side, thereby sharply reducing the size of the α-phase region. In contrast, nickel has a negative “zinc equivalent coefficient,” meaning it expands the α-phase region.
　　(2) The properties of special brass: In special brass, the α and β phases are complex, multi-component solid solutions with significant strengthening effects. In contrast, the α and β phases in ordinary brass are simple Cu-Zn solid solutions with relatively weaker strengthening effects. Although their zinc equivalents are comparable, the properties of multi-component solid solutions differ from those of simple binary solid solutions. Therefore, introducing a small amount of multi-component strengthening is one effective approach to enhancing the performance of alloys.
　　(3) Microstructure and pressure-processing properties of several commonly used special brass alloys: lead brass, manganese brass, iron brass, nickel brass, etc.
　　Brass grades (national standard)
　　02 Ordinary Brass
　　H90, H80, H68, H62
　　03 Special Brass
　　Lead brass: HPb59-1, HPb62-3, HPb58-3, HPb61-1, HPb60-3, HPb57-4
　　Manganese brass: HMn58-2, HMn57-3-1, HMn57-2-2-0.5, HMn55-3-1
　　Silicon brass: HSi80-3, HSi75-3, HSi62-0.6, HSi61-0.6
　　Nickel brass: HNi65-5, HNi56-3
　　Aluminum brass: HAl60-1-1, HAl59-3-2, HAl61-4-3-1, HAl61-4-3-1.5
　　Tin-brass: HSn70-1, HSn62-1, HSn60-1, HSn72-1, HSn65-0.03
　　Iron brass: HFe59-1-1, HFe58-1-1
　　Antimony brass: HSb60-0.9, HSb61-0.8-0.5
　　Magnesium brass: HMg60-1