The Main Classification of Brass
Lead is practically insoluble in brass and is distributed on the grain boundaries in the form of free particles. Lead brass has two kinds of α and (α+β) according to its organization. Since α lead brass has a large harmful effect of lead and has high temperature plasticity, it can only be cold-deformed or hot-extruded. (α+β) lead brass has good plasticity at high temperatures and can be forged.
The addition of tin to brass can significantly improve the heat resistance of the alloy, especially the ability to resist seawater corrosion. Therefore, tin brass is known as "navy brass".
Tin can be dissolved in a copper-based solid solution to provide solid solution strengthening. However, as the tin content increases, a brittle r-phase (CuZnSn compound) appears in the alloy, which is detrimental to the plastic deformation of the alloy. Therefore, the tin content of tin brass is generally in the range of 0.5% to 1.5%.
Commonly used tin brasses are HSn70-1, HSn62-1, HSn60-1 and the like. The former is an alpha alloy and has a high plasticity. The alpha alloy can be processed by cold and hot pressing. The latter two grades of alloy have a (α + β) two-phase structure, and often a small amount of r phase, the room temperature plasticity is not high. They can only be deformed in the hot state.
Manganese has a greater solubility in solid brass. Adding 1% to 4% manganese to brass can significantly improve the strength and corrosion resistance of the alloy without reducing its plasticity.
Manganese brass has (α + β) structure, commonly used HMn58-2, the pressure processing performance in cold and hot state is quite good.
In iron brass, iron precipitates as an iron-rich phase, refines grains as a nucleus, and prevents recrystallized grains from growing, thereby improving the mechanical properties and process properties of the alloy. The iron content in iron brass is usually less than 1.5%, its structure is (α + β), it has high strength and toughness, plasticity is good at high temperature, and it can be deformed in cold state. The commonly used grade is Hfe59-1-1.
Nickel and copper form a continuous solid solution, significantly expanding the alpha phase region. The addition of nickel to brass significantly improves the corrosion resistance of brass in the atmosphere and seawater. Nickel also increases the recrystallization temperature of the brass, which promotes the formation of finer grains.
HNi65-5 nickel brass has a single-phase α structure, which has good plasticity at room temperature and can also be deformed in a hot state. However, the content of lead in the production process must be strictly controlled, which will seriously deteriorate the hot workability of the alloy.