Traditional die casting technology is mainly composed of four steps, or called high pressure die casting. These four steps including mould preparation,filling,injection mould and shakeout.They are also the basis of various modified die-casting process. In preparing process,we need to spray lubricants to cavity of mold, lubricants can help to control the temperature of the mold,but can also help casting mold release.Then you can close the mold, with high-pressure injecting molten metal into the mold.The pressure ranges between 10 to 175 million mpa.After filling molten metal,pressure will remain until the casting solidification.Then push rod will push out all the castings.As there may be multiple mold cavities in a mold, so every time may produce multiple castings during casting process.Shakeout process requires the separation of residue, including gate, runner, gate and flash. This process is usually through a special trimming die extrusion casting. Other methods of doffing including sawing and grinding.
Die casting machine mainly can be divided into two different types,hot chamber die-casting machine and cold chamber die casting machine.The difference is that they can withstand how much power,the typical stress ranges between 400 and 4000 kg.
Metals used in die casting
Metals used in die casting include zinc, copper, aluminum, magnesium, lead, tin and lead tin alloy.
*Zinc die castings:Most easy die casted metal.It is very economic to make small parts,easy to coating, high compressive strength, plasticity,long service life.
*Aluminum die castings:Light quality, high dimension stability for manufacturing complex and thin wall castings,strong corrosion resistance,good mechanical performance,high thermal conductivity and electrical conductivity, high strength under high temperature.
*Magnesium die castings:Easy to do machining, high strength weight ratio, is the lightest weight in all die casted metals.
*Copper die castings:High hardness, strong corrosion resistance,best mechanical properties in commonly used die casted metals, wear resistance,strength close to the steel.
Advantages and disadvantages
The advantages of die casting include good size accuracy. Comparing with other casting process(investment casting and sand casting), the casting surface is smooth, rounded corners radius is approximately 1-2.5 microns It can be directly casting internal structure, such as silk, heating element,high strength and bearing surfaces. Other benefits include that it can reduce or avoid the secondary machining, high production speed and the tensile strength could reach 415 million mpa, can casting high liquid metal.
The biggest disadvantage of die casting is high production cost.Casting equipment and mold, mold related components are all expensive compared with other casting method.Therefore die casting production is more suitable for a large number of products. Other disadvantages include: this process applies only to liquid metal and the casting weight must be between 30 grams to 10 kilograms.Usually, die castings in the last batch will always exsit porosity. So can't make any heat treatment or welding, because the gas inside the gap will be expanded under the effect of heat ,leading to micro defects of the internal.