What is Aluminum Casting?
Aluminum casting is a kind of metalworking process that involves pouring liquid metal into a mold or form. Aluminum casting may be a variation of this that uses only aluminum and aluminum alloys because of the liquid metal that’s poured into the mold. Aluminum castings are used to make complex and detailed die casting parts very efficiently.
How does Dolin Casting Explain Aluminum Casting?
Aluminum is heated to its liquid form within the aluminum casting process then poured into a mold. Molding must be made with precision because of the quality that will have an immediate impact on the form and surface finish of the finished aluminum casting.
The mold is often made up of many various materials, including alloy steel, because aluminum features a lower freezing point than steel. Another material that a mold is often made out of for aluminum casting is sand. For this, the sand is pressed to require the shape of the specified finished part. Once the sand is made, the liquid aluminum is poured into it and allowed to chill.
Aluminum castings have properties almost like other aluminum components. Once the casting process is complete the aluminum castings quickly form an exterior layer of alumina that helps protect against corrosion.
Aluminum Casting Methods
Aluminum casting processes are described as Ingot casting or Mould casting. During the primary process, primary or secondary aluminum is cast into a rolling ingot (slab), extrusion ingot (billet), and wire bar ingot which is subsequently transformed into semi- and finished products.
The second process is employed within the foundries for producing cast products. This is often the oldest and simplest (in theory but not in practice) means of producing shaped components.
This section describes exclusively Mould casting which may be divided into two main groups:
- Sand casting
- Die casting
Other techniques like “lost foam” or “wax pattern” processes also are used but their economical importance is considerably less than both listed techniques.
In sand casting, re-usable, permanent patterns are wont to make the sand molds. The preparation and therefore the bonding of this sand mold are the critical step and really often are the rate-controlling step of this process. Two main routes are used for bonding the sand molds:
- The “green sand” consists of mixtures of sand, clay, and moisture.
- The “dry sand” consists of sand and artificial binders cured thermally or chemically.
The sand cores used for forming the within the shape of hollow parts of the casting are made using dry sand components.
This versatile technique is usually used for high-volume production. An example of a half sand mold is given in this aluminum casting article
Dolin Casting – Metals, ceramics, polymers and composites: Aluminum sand Casting Techniques
Figure 1. Half mold with cores and an example of a cast air intake for a turbocharger.
Normally, such molds are filled by pouring the melted metal into the filling system. Mold designing may be a particularly complex art and is predicated on an equivalent principle as gravity die casting illustrated in Figure 4.
In the “low pressure” sand casting technique, the melted metal is forced to enter the mold by low difference. This more complicated process allows the assembly of cast products with thinner wall thickness.
In this technique, the mold is usually not destroyed at each cast but is permanent, being made from a metal like forged iron or steel. There are varieties of die casting processes, as we described in this article. High dies casting is that the most generally used, representing about 50% of all light alloy casting production. Low-pressure die casting currently accounts for about 20% of production and its use is increasing. Gravity dies casting accounts for the remainder, with the exception of a little but the growing contribution from the recently introduced vacuum dies casting and squeeze casting process. Choose the best Aluminum Die Casting Company.
Most parts constituting a classical mold for gravity die casting. Cores (inner parts of the mold) are generally made from bonded sand.
Gravity dies casting is suitable for production and for fully mechanized aluminum casting.
High-Pressure Die Casting
In this aluminum casting process, the liquid metal is injected at high speed and high into a metal mold with the help of die casting equipment.
This equipment consists of two vertical platens on which bolsters are located which hold the die halves. One plate is fixed and therefore the other can move in order that the die is often opened and closed. A measured amount of metal is poured into the shot sleeve then introduced into the mold cavity employing a hydraulically driven piston. Once the metal has solidified, the die is opened and therefore the casting is removed.
In this high-pressure die casting process, special precautions must be taken to avoid too many gas inclusions which cause blistering during subsequent heat-treatment or welding of the casting product.
Both the machine and its dies are very expensive, and for this reason, pressure die casting is economical just for high-volume production.
Low-Pressure Die Casting
Low-pressure die casting is especially used for the production of components that are symmetric about an axis of rotation. Normally, light automotive wheels are manufactured by this technique.
Vacuum Die Casting
The principle is that the same as low-pressure die casting. The pressure inside the die is decreased by an air pump and therefore the difference of pressure forces the liquid metal to enter the die. This transfer is a smaller amount turbulent than other casting techniques in order that gas inclusions are often very limited. As a consequence, this new technique is particularly aimed toward components that will subsequently be heat-treated.
Squeeze Casting or Squeeze Forming
liquid metal is introduced into an open die, even during a closed die forging process. The dies are then closed. During the ultimate stages of closure, the liquid is displaced into the further parts of the die. No great fluidity requirements are demanded of the liquid since the displacements are small. Thus forging alloys, which generally have poor fluidities which normally preclude the casting route, are often cast by this process.
This technique is particularly fitted to making fiber-reinforced castings from fiber cake perform. Squeeze casting forces liquid aluminum to infiltrate the preformed as compared with non-reinforced aluminum alloy, aluminum alloy matrix composites manufactured by this system can double the fatigue strength at 300°C. Hence, such reinforcements are commonly used at the sides of the piston head of a diesel where solicitations are particularly high.
Which Aluminum Casting Process Should You Choose?
While Dolin Casting focuses on the sand and permanent mold techniques. This article covers the foremost common factors that contribute to a choice on which method is the right one for you. Along a side a quick overview of every factor, we’ll note which of the three processes meets that require best:
Speed: Sand Casting automated processes, like at Dolin Casting Manufacturing, provides a high output of parts during a short amount of your time in comparison to permanent mold processes. Die casting provides the best speed in manufacturing, because of the pressurized injection process.
Strength: Permanent mold casting provides the best material strength within the finished product. Although almost like die casting, the pieces produced via permanent mold casting have a plus during this area thanks to the character of the method.
High quantities: Sand Casting offers the foremost advantageous balance between higher quantities and tooling costs, while a permanent mold may be a closer second. For quantities well in more than 100,000, however, die casting could also be the higher choice.
Prototypes and short runs: Sand casting is that the method of choice when only a couple of pieces are needed, because of its low tooling cost.
Surface finish: Permanent mold casting and die casting offer the smoothest surface round out of the mold.
If you want additional information about the right process, Dolin Casting is ready to help you. To learn more about our one-stop Aluminum casting and permanent mold casting services, contact us today to receive a quote.