Aluminium die casting machines use aluminium alloys that are lightweight and have high dimensional stability for complex part geometries and thin walls. Aluminium withstands good corrosion resistance and mechanical properties, as well as high thermal and electrical conductivity, making it a good alloy for die casting. Low-density aluminium metals are essential in the foundry industry.
The aluminium die casting machine adopts a process that maintains durable strength at very high temperatures, which requires the use of cold chamber machines. The molten metal is still in the open storage vessel which is placed in the furnace where it is melted to the required temperature. The open holding vessel is separate from the die casting machine and molten metal is poured out of the vessel on each casting as these high temperatures would damage the normal pumping system. The pressure requirements for cold chamber die casting are usually higher than for hot chamber die casting.
There are many reasons why aluminium is the most widely cast non-ferrous metal in the world. As a lightweight metal, the most common reason for using die cast aluminium is because it creates very light parts without sacrificing strength. Aluminium die cast parts also have more surface finish options and can withstand higher operating temperatures than other non-ferrous materials. Aluminium die cast parts are corrosion resistant, highly conductive, have good stiffness and strength-to-weight ratio.
The aluminium die casting process is based on high-speed production which enables high volumes of die cast parts to be produced very quickly and cheaper than alternative casting processes. Aluminium die casting has become the preferred option for buyers all over the world. Big advantages of aluminium and therefore aluminium die casting machines include great processability thanks to the lightweight and durable characteristics of aluminium, great corrosion resistance and full recyclability and reusability in production.
There are three basic operations for aluminium die casting machines that use natural gas fired equipment. In the first process, aluminium ingots and / or pure aluminium scrap are heated to about 650 ° C, where the aluminium melts. In a second stage, the molten aluminium is then transferred to a holding furnace, where the molten aluminium is melted and degassed if necessary, and then heated to a casting temperature of around 750 ° C. In the final stage, the molten aluminium is then transferred through a ladle or tundish to pre-heated die or mold.
Flame furnaces heat aluminium to melting points using direct-fired wall-mounted burners. The primary way of heat transfer is through radiation from refractory brick walls to aluminium, but convective heat transfer also provides additional heating from the burner to the aluminium. Reverberant furnaces for aluminium die casting are available with capacities up to 150 tons of molten aluminium. The advantages of reverberant aluminium melters are the high processing speed and low operating and maintenance costs. The disadvantages of aluminium reverberation melters are the high rates of metal oxidation, low efficiency and high surface requirements.
The vats used to transfer and pour molten aluminium should be heated before loading to minimize thermal shock and damage to the refractory brick. Old practices have used inefficient open gas pipes to heat the ladles. This practice has largely been superseded by efficient ladle heating systems using sealed lids, combustion control and even recuperation. Most of the work was on large ladles, but recent changes have focused on ladle-sized preheating stations that are used to heat more than one ladle.
Electric reverberation furnaces are mainly used as hold-up furnaces and are rarely used for aluminium die casting. These furnaces are refractory-lined vessels with resistance heating elements mounted in the roof of the furnace above the hearth. These furnaces are used for smaller melting applications where the limitation of emissions, product quality, and efficiency are of high priority. Advantages over gas-fired reverberation furnaces include low emissions, low metal oxidation, and less furnace cleaning. The disadvantages include high fuel costs, low production rates, higher capital costs, and frequent replacement of heating elements.
Crucible furnaces are low capacity intermediate aluminium holders, typically used for small melting applications or solely as holding furnaces for aluminium die casting processes. The aluminium is placed or poured into a ceramic crucible that is housed in a circular gas burner furnace. The energy is fed indirectly to the metal by heating the crucible. Crucible furnaces have the advantage of being able to quickly change alloys, low oxidation losses, and low maintenance costs.
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