Deha Tech and Yildiz Technical University has casted its first Magnesium Product with patented design Cold Chamber Die-Casting Machine.
Die casting is a metal casting process that is characterized by forcing molten metal under high pressure into amould cavity. The mold cavity is created using two hardened tool steel dies which have been machined into shape and work similarly to an injection mold during the process. Most die castings are made from non-ferrous metals, specifically zinc, copper, aluminium, magnesium, lead, pewter and tin based alloys. Depending on the type of metal being cast, a hot- or cold-chamber machine is used.
||Magnesium Physical properties
||Aluminium Physical properties|
|Density (near r.t.)
|Liquid density atm.p.
||923 K, 650 °C, 1202 °F
||933.47 K, 660.32 °C, 1220.58 °F|
||1363 K, 1091 °C, 1994 °F
||2792 K, 2519 °C, 4566 °F|
|Heat of fusion
|Heat of vaporization
|Molar heat capacity
Aluminum vs Magnesium
The difference between aluminum and magnesium is based upon many factors, such as brittleness, heat dissipation, tool life, die casting and cost. Magnesium, when compared to aluminum, is lightweight and valuable, whereas forged aluminum is stronger.
Aluminum and magnesium are both used for manufacturing automobile parts, and many experiments have been done to substitute aluminum with magnesium. Magnesium, when compared to aluminum, is softer and more expensive, and has the tendency to bend easily. Magnesium versus aluminum is highly reactive and less stable than aluminum.
Energy requirements for aluminum and magnesium provide us with a comparison between both materials. We can compare them by looking at economic advantages versus energy requirements for melting each of the two materials in the die casting process. Magnesium and its alloys are more cost effective in terms of energy requirements than aluminum and its alloys. Aluminum has the advantage over magnesium when comparing the use of steel for melting and holding aluminum. The melting of magnesium used to be expensive in the past, but it can be as economical as melting aluminum for die cast parts with the advent of new technology. Magnesium die casting has a definite cost advantage over aluminum. Magnesium has a rapid solidification rate when compared to aluminum, which usually requires high shot pressure.
Automotive parts can be easily formed from magnesium, and companies like Ford are running tests to substitute aluminum with magnesium. The die casting cycle of aluminum versus magnesium has more advantages, since the magnesium injected speed should be very fast due to its rapid solidification rate, whereas magnesium die casting’s eject time is shorter than the amount of time required for aluminum. Magnesium die casting needs a shorter dwelling and lubrication time, with faster shot speed, when compared to aluminum.
The tool life of aluminum is another favorable economic advantage. As aluminum has an affinity for tool steel, its die castings have a cosmetically better finish when compared to magnesium. An estimated tool life for aluminum versus magnesium production die is 100,000 to 150,000 shots.
The machine ability of magnesium die casting versus aluminum has advantages over aluminum, since magnesium machines dry up rapidly due to heat dissipation. Magnesium also requires a protective coating to save it from corrosion. Magnesium used for lightweight component applications largely depends upon casting technology, for magnesium is less costly and has low environmental hazards. Magnesium has potential benefits for the environment and better design options when compared to aluminum, since it is lighter in weight and can be substituted for aluminum transmission case applications. Lightweight magnesium components in vehicles may increase the fuel economy, and be an important design metric. Automobile manufacturers in North America and Europe are involved in developing new generation, highly fuel-efficient cars that are light weight, while substituting aluminum with magnesium.
1. Aluminum versus magnesium is heavier and more corrosion resistant.
2. Magnesium is a lightweight substitute for aluminum.
3. Magnesium needs a protective coating to make it an anti corrosive material.
4. Aluminum has a lower die casting cost when compared to magnesium.
5. Magnesium is soft and flexible when compared to aluminum, which is stronger.
Hot-chamber machines, also known as gooseneck machines, rely upon a pool of molten metal to feed the die. At the beginning of the cycle the piston of the machine is retracted, which allows the molten metal to fill the "gooseneck". The pneumatic or hydraulic powered piston then forces this metal out of the gooseneck into the die. The advantages of this system include fast cycle times (approximately 15 cycles a minute) and the convenience of melting the metal in the casting machine. The disadvantages of this system are that high-melting point metals cannot be utilized and aluminium cannot be used because it picks up some of the iron while in the molten pool. Due to this, hot-chamber machines are primarily used with zinc, tin, and lead based alloys.
These are used when the casting alloy cannot be used in hot-chamber machines; these include aluminium, zinc alloys with a large composition of aluminium, magnesium and copper. The process for these machines start with melting the metal in a separate furnace. Then a precise amount of molten metal is transported to the cold-chamber machine where it is fed into an unheated shot chamber (or injection cylinder). This shot is then driven into the die by a hydraulic or mechanical piston. This biggest disadvantage of this system is the slower cycle time due to the need to transfer the molten metal from the furnace to the cold-chamber machine.