What role do various elements play in brass alloys?
The basic metal elements of brass alloy are copper and zinc. In addition to copper and zinc, the reasonable addition of other elements can also change or enhance the performance of brass. At the same time, the excessive addition of some elements can also reduce the performance of brass. Due to the different characteristics of elements, they can be insoluble in copper, slightly soluble, largely soluble, infinitely soluble, and their solubility decreases sharply with the decrease of temperature, and there are complex phase changes in the solid phase. Therefore, the effects on copper properties vary greatly. The role of each element in copper alloy is introduced separately.
Iron Fe
1. The dissolution of iron in solid copper is very small, and it is distributed in the α matrix as iron-rich phase particles, which has the effect of refining grains. H60 brass adds 0.3%~0.6, which has a strong grain refining effect, but the iron content of antimagnetic copper materials should be less than 0.3%.
2. Impurity iron has no obvious effect on the mechanical properties of brass.
Lead Pb Bismuth Bi
1. Lead and bismuth are harmful impurities in general brass, and bismuth is more harmful than lead. 2. Lead exists in the form of particles in the fusible eutectic on the grain boundary. If the lead content of α brass is greater than 0.03%, hot brittleness will occur, and there will be no obvious effect on the cold processing performance. Lead has no significant effect on the processing performance of duplex brass, and its allowable content can be slightly higher. 3. Bismuth is distributed on the grain boundary in brass as a continuous brittle film, making brass brittle during cold and hot processing. 4. If the cold-rolled brass containing lead and bismuth exceeding the allowable limit is heated too fast during annealing, "fire cracking" or sudden bursting will occur. 5. Adding a small amount of zirconium and other elements to brass containing lead and bismuth to form high-melting point compounds can eliminate their hazards.
Phosphorus P
1. The solid solubility of phosphorus in α copper is very small. A small amount of phosphorus has a grain refinement effect and improves the mechanical properties of brass. When the phosphorus content in brass is greater than 0.05%, brittle phase Cu3P will be formed, reducing the processing performance of brass. 2. Phosphorus significantly increases the recrystallization temperature of brass, making the recrystallized grains uneven.
Antimony Sb
1. The solubility of antimony in copper decreases sharply with the decrease of temperature. When its content is less than 0.1%, Cu2Sb will be formed, which is distributed in the grain boundary in a network, which greatly reduces the cold working performance of brass. 2. Antimony also makes copper alloys hot brittle. 3. Adding trace lithium to brass can form a high melting point compound Li3Sb, which is evenly distributed in the grains in the form of fine particles, thereby eliminating the adverse effects of antimony. 4. Since antimony has a high solubility in copper at high temperatures, solid solution treatment can improve the cold working performance of antimony-containing brass.
Tin Sn
1. It can be dissolved in a small amount in α phase and (α+β) brass, inhibiting dezincification, improving the corrosion resistance of the material, and improving wear resistance, but Sn can cause reverse segregation of ingots.
Manganese Mn
1. It has a high solubility in brass, which can improve the strength and hardness of brass;
2. High manganese brass can be quenched and aged to improve its strength and hardness.
Aluminum Al
1. Aluminum significantly reduces the α zone of brass. When the aluminum content increases, the γ phase will appear. Although it can increase the hardness, it greatly reduces the plasticity of the alloy;
2. Increase the fluidity of brass.
