Is Brass Valuable?


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Yes.Ordinary brass

(1) Common brass Common brass is copper and zinc at room temperature organization binary alloy, the zinc content varied greatly, so the room temperature is very different organizations. According to Cu-Zn binary state diagram (Figure 6), brass at room temperature in three organizations: The volume of 35% zinc brass, at room temperature by the single-phase micro-structure of α-solid solution, known as the α Huang copper; zinc content of 36% to 46% range of brass, the micro-structure at room temperature by the (α + β) two phases, called the (α + β) brass (two-phase brass); with more than 46% zinc to 50% of the brass, the micro-structure at room temperature only by the β phase, known as β brass.
(2) pressure processing properties
α single-phase brass (from H96 to H65) has a good plastic, can withstand the cold and hot processing, but the α single-phase brass forging and other hot working hours in the prone in the brittle temperature, the specific temperature range as there are with different Zn content The changes, generally between 200 ~ 700 ℃. Therefore, when thermal processing temperature should be higher than 700 ℃. Single-phase α brass brittle zone temperature causes mainly in the Cu-Zn alloy system there Cu3Zn α phase region and Cu9Zn two ordered compounds, when heated in the orderly transition temperature, the alloys become brittle; other , there is trace amounts of lead alloy, bismuth harmful impurities and the formation of low melting point eutectic copper film on the grain boundaries, the heat generated when processing the inter-granular fracture. Practice has shown that adding small amounts of cerium can effectively eliminate the temperature brittleness.
Two-phase brass (from H63 to H59), in addition to alloy with good ductility α phase, but also emerged from the e-Cu-Zn-based compound β-solid solution. β-phase at high temperature with high plasticity, and low temperature β 'phase (ordered solid solution) the nature of hard and brittle. Therefore, (α + β) brass should be carried out under the hot forging. Zinc is higher than 46% to 50% of the β brass because of performance of hard and brittle, the pressure can not be processed.
(3) mechanical properties of brass, zinc content because of different mechanical properties are not the same, Figure 7 is a brass mechanical properties vary with the zinc content of the curve. For α brass, with the increase in zinc content, σb and δ have been increased. For the (α + β) brass, when the zinc content increased to about 45% before the room temperature strength improved. Ruozai further increase the zinc content, due to appear in the alloy more brittle r phase (in Cu5Zn8 compounds based solid solution), the intensity decreased dramatically. (Α + β) brass with zinc at room temperature ductility is always the amount of increases. Therefore, more than 45% zinc zinc alloy no practical value.
Very wide range of general purpose brass, such as the water tank with, for drainage, medals, corrugated pipe, snake-like tube, condenser, shell and various forms of complex impulse products, hardware fittings. With the increase of zinc from H63 to H59, which can well withstand thermal processing, are used for a variety of mechanical and electrical parts, stamping parts and musical instruments, etc..

Special brass
In order to improve the corrosion resistance of brass, strength, hardness and cutting and so on, in the copper - zinc alloy by adding a small amount (usually 1% to 2%, a small number of 3% to 4%, a very few up to 5% ~ 6 %), tin, aluminum, manganese, iron, silicon, nickel, lead elements, constitute or three or four or even five-alloy, namely copper complex, also known as a special brass.
(1) zinc equivalent coefficient of complex organizational brass, brass adding elements according to the "zinc equivalent factor" to project. Because a small amount of copper and zinc alloy other alloying elements, usually only to Cu-Zn state diagram of the α / (α + β) phase region to the left or right. Therefore, the organization of a special brass, brass is usually the equivalent of general increase or decrease in zinc content in the organization. For example, in Cu-Zn alloy after adding 1% silicon organization, which is equivalent to the Cu-Zn alloy in 10% zinc alloy. Therefore silicon "zinc equivalent" is 10. Silicon, "zinc equivalent factor" the greatest, so that Cu-Zn system in the α / (α + β) phase boundary copper side of a significant shift, which strongly reduce the α phase region. Nickel's "zinc equivalent factor" is negative, that the expansion of α phase region.
(2) the performance of special brass special brass in the α phase and β phase is a multi-complex solid solution strengthening effect of its large, ordinary brass in the α and β phase is a simple Cu-Zn solid solution strengthening effect of its lower. Though zinc equivalent rather, multiple solid solution and the nature of a simple binary solid solution is not the same. Therefore, the small number of multiple reinforcement is a way to improve the alloy properties.
(3) the specific deformation of several commonly used brass bodies and pressure processing properties
Brass Lead: Lead is not soluble in the real brass, which showed the distribution of free particle states in the grain boundary. Brass lead their organizations to α and (α + β) two. α lead brass because the harmful effects of lead large, high temperature plastic is very low, it can be cold or hot extrusion deformation. (Α + β) brass at high temperatures of lead has good plasticity, can be forged.
Tin Brass: Brass adding tin alloy can significantly improve the heat resistance, especially to improve the capacity of resistance to seawater corrosion, so tin brass have "the Navy brass," said.
Tin in solid solution can integrate into the copper, from solid solution hardening effect. But with the increase of tin content, the brittleness of the alloy appears r phase (CuZnSn compound), is not conducive to plastic deformation of the alloy, so the amount of tin brass, tin-containing generally 0.5% to 1.5% range.
Commonly used tin brass HSn70-1, HSn62-1, HSn60-1 and so on. The former is the α alloy, has a high plasticity, can be cold, hot pressure processing. The latter two grades of alloys with (α + β) two-phase structure, and often a small amount of r phase occurs at room temperature plasticity is not high, only under the hot deformation.
Brass Manganese: Manganese in solid brass have a greater solubility. Brass added 1% ~ 4% manganese, can significantly improve tensile strength and corrosion resistance, without reducing its plasticity.
Manganese brass with (α + β) organization, commonly used are HMn58-2, cold and hot processing performance under the pressure quite well.
Iron Brass: Brass Rail, the rail in order to iron-rich phase particle precipitation, as the nuclei and the grain refinement, and can prevent recrystallization grain growth, thereby enhancing the mechanical properties of alloy and process performance. Brass in the iron content of iron is usually below 1.5%, its organizations (α + β), with high strength and toughness, high temperature and good plasticity, even under cold deformation. Commonly used grade for the Hfe59-1-1.
Nickel Brass: Nickel and copper can form a continuous solid solution, a significant increase in α phase region. Brass containing nickel could significantly increase the brass in the atmosphere and seawater corrosion resistance. Brass Nickel also increases the recrystallization temperature, to promote the formation of finer grain.
HNi65-5 nickel-brass phase α with a single organization, with very good ductility at room temperature can also be deformed in the hot state, but a lead content of impurities must be strictly controlled, whether the system would be a serious deterioration in the thermal processing performance.

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