ALUMINIUM AND ALLOYS CASTING
Aluminium and alloys die casting using gravity moulds in metal and injection moulds, and with different compositions, properties and qualities required for every project and use.
Aluminium is a bluish silver-white malleable ductile light trivalent metallic element that has good electrical and thermal conductivity, high reflectivity, and resistance to oxidation. Its symbol is Al. It is found in different minerals, mostly in bauxite. It is obtained by means of an electrolytic process from the alumina extracted from bauxite.
Aluminium has a density of 2.7 g / cm3 and a melting point of 660 ° C. The tensile strength of pure aluminium castings is about 7 Kg / mm2. The compressive strength is 2.1 kg / mm2. Brinell hardness is 22 Kg / mm2 at ordinary temperature.
The elongation is 30%.
Aluminium is a tough, malleable, ductile metal and a good conductor of heat and electricity. To improve its mechanical properties is alloyed with other metals, mainly silicon (Si), magnesium (Mg), manganese (Mn), copper (Cu) and zinc (Zn), sometimes titanium (Ti) and chromium (Cr) are also added.
Aluminium alloys for casting are standardized and their chemical composition and characteristics can be seen in detail in the Table Aluminium Alloys.
Silicon in the range of 5 to 12% is the most important alloying element because it promotes increased fluidity in molten metals. In smaller amounts, magnesium or copper are added in order to increase the resistance of the castings.
Our supplier of aluminium alloys is ALCOA (Aluminium Company of America), which only provides primary aluminium.
Some alloys can be heat -treated to improve mechanical properties. A heat treatment can be carried out only with the alloys that have as a main alloying agent an item or items whose solid solubility in aluminium increases significantly when temperature rises. This feature enables a more uniform and effective distribution of the alloying elements, resulting in an increase in strength and hardness, as the casting will have a more homogeneous structure.