Aluminium alloy smelting furnace

Aluminum alloy and its melting
Aluminum alloy series: there are three series of aluminum alloys, according to the elements formed with their alloy and some differences.
1, Al Si: silicon content in near eutectic point, the fluidity of the alloy, the casting performance is good, not easy to crack, density, thermal expansion, thermal conductivity, corrosion resistance, suitable for casting large complex thin-walled castings. However, its mechanical properties are not high enough, the machinability is slightly worse, and the anodizing is not ideal.
2, aluminum silicon copper system: alloy has the best comprehensive performance, widely used, especially in the automotive and motorcycle industry.
3 、 Al Mg system: the strength, plasticity, corrosion resistance and surface quality of the alloy are the best, but the shrinkage and expansion are large, and the casting performance is poor.

Two, the role of alloying elements:
1, Si: Al and Si eutectic point in 11.7%, solidification temperature range of eutectic alloy minimum, feeding and thermal cracking resistance alloy eutectic point near the best, have good fluidity, suitable for casting, casting large and complex. With the increase of silicon content, the strength and hardness also increased, but the elongation decreased, the cutting performance became worse, and the alloy also increased the crucible corrosion.
2, copper: copper for aluminum alloy can improve the mechanical properties, improve machinability, but the corrosion resistance is reduced, the hot crack tendency increases.
3, magnesium: aluminum magnesium alloy corrosion resistance is good, but because of the temperature range of solidification is large, there is hot brittleness, so the casting is easy to produce cracks, its liquidity with the magnesium content improved, but the corresponding shrinkage also increased. For Al Si alloy, magnesium has strengthening effect, improving corrosion resistance, improving the performance of electroplating, anodizing and casting surface quality. But for aluminum, silicon and copper, the content must be controlled, because magnesium will cause hot cracking, cold brittle, reduce elongation and impact toughness.
4, iron: iron can ease the affinity between aluminum and mold, usually controlled between 0.6% ~ 1%, high iron content in the casting FeAl3 needle phase, reduce performance. In the Al Si system and Al Si Cu system, excessive Fe forms intermetallic compounds and leads to brittleness, which will affect the surface roughness during cutting.
5, manganese: moderate manganese can neutralize the detrimental effect of excessive iron, but not greater than 0.5%.
6, zinc can improve flowability, improve mechanical properties, but high temperature brittleness, produce hot crack.
7: Tin: improve cutting performance, reduce strength and corrosion resistance, high temperature brittleness.
8, nickel: a small amount of nickel can improve the mechanical properties, detrimental to corrosion resistance.
9: lead: improve cutting performance, but damage corrosion resistance.
10, chromium: improve corrosion resistance. 11, titanium: refining crystallization, improve performance.
Three. Melting of aluminium alloy:
Melting of aluminum alloy is an important link for die casting enterprises. There are two processes of smelting and heat preservation, one side is die casting
Smelting is not allowed.
1, die casting aluminum alloy liquid has the following requirements:
The chemical composition meets the requirements and the composition is uniform.
(2) the gas is small in amount of melting, oxide inclusion, less flux, so as to avoid formation of blowhole and slag in the casting.
The refinement of the microstructure makes the casting obtain compact crystallization.
The casting defects caused by improper melting process include leakage, blowhole inclusion, segregation, crack, coarse grain and so on.