What is die casting and how has been progressing since the 19th century? This and many other basics such as the use of different processes and materials are explained in the following article.
Die casting is one of the most economical and quickest forming processes. The advantages of this production process are that hundreds of thousands of castings can be produced relatively quickly by using just one mold. All components produced have a uniform quality and involve relatively low unit costs. But how exactly does the manufacturing process look like? What materials can be used and in what areas are the castings used?
Die casting is an automated casting process in which the liquid melt is pressed into a mold under high pressure (150 to 1200 bar) and at a high filling speed (up to 540 km/h). Usually alloys with a low melting point are used. This casting process is particularly suitable for series and mass production of components because, unlike sand casting, for example, permanent metal molds are used which do not have to be destroyed after casting. It is possible to produce large and complex components with low wall thicknesses.
The die casting molds, made of high-quality, heat-resistant steel grades, consist of two halves which form a cavity into which the liquid melt is pressed during the casting process. The halves are located on a fixed and a movable machine plate. During the casting process a high pressure is applied to the mold halves, which is why the mold is equipped with latches. In addition, certain parts of the mold are cooled and/ or heated so that the casting solidifies as desired. The production of the molds is very expensive and time-consuming, but several tens of thousands to over a million castings can be produced with just one of them. A further advantage of the reusable casting molds is that the melt cools down quickly.
In die casting, there are two different ways of manufacturing components: hot chamber and cold chamber die casting. In both manufacturing processes, the mold is sprayed with a release agent prior to the casting process in order to ensure that the subsequently cast part can be easily remover from the mold. However, the melt is not poured directly into the mold cavity, but is first filled into the casting chamber of the die casting machine. From there, the alloy is pressed into the mold by a piston (the so-called casting set) through one or more channels. The difference between the two processes lies in the structure of the casting chamber as described below.
A characteristic feature of hot chamber die casting machines is that the casting chamber is constantly in contact with the liquid alloy. The melt passes through a valve into the casting chamber, where it is pressed at high speed into the closed die casting mold by the piston. This process is used for alloys with a low melting point, such as zinc, lead or tin.
Cold chamber die casting machines are designed in such a way that the casting set is located outside the melt. To produce a component, the alloy is filled into the casting chamber and pressed into the die casting mold through channels. This process is suitable for materials with a higher melting point. These include, for example, aluminum and copper.
After the alloy has been pressed into the mold in both processes, the component solidifies under the strong pressure, whereupon the latches of the mold can be opened. The part with gate is removed from the mold by automatically operated ejection pins and can be further processed if necessary. In simple words, the casting process can be divided into the following steps and in practice takes place in hundredths of a second – or even only thousandths of a second:
Fast filling of the casting mold with the alloy
Curing of the component under high pressure
Opening of the mold and removal of the component
In die casting, non-ferrous metals are used to manufacture components, and the choice of alloy for a particular application depends on budget, weight and material properties.
Aluminum is one of the most important materials with a share of more than 80 %, followed by zinc and magnesium. However, copper, lead and tin can also be used. The alloys have different properties. For example, aluminum (600°C) and magnesium (520°C) have a high melting point, zinc (380°C) and lead (320°C) a low melting point.
High corrosion resistance
High strength and hardness
High thermal conductivity
High electrical conductivity
Very good EMI/ RFI isolation
Good processing properties
Die casting is mainly used for large series production, i.e. for many components of the same type to be cast. Despite the high pressure used during the manufacturing process, a high casting quality is achieved. The die casting process is particularly suitable for the production of very thin (up to 1 mm) (lightweight) components.
Most commonly, die cast components are manufactured for the automotive industry, such as wheels, blocks, cylinder heads, valve blocks and manifolds. This sector accounts for around 84 % of the castings produced by German foundries. 3 The use of aluminum parts leads to a reduction in the weight of the vehicles and thus to a reduction in fuel consumption. In addition, there are other industries in which die cast parts are used:
Aerospace
Domestic Appliances
Furniture
Power Tools
Electronics
Machinery
Lighting Technology
In the future, other industries such as electromobility will be of interest to foundries. This offers enormous potential for light metal castings.
Key design factors for aluminium die casting. Here are some additional points that can improve their effectiveness: 1.Material selection: Selection of the right aluminium alloy is critical to achieving the required mechanical properties, surface finish and overall performance of the final part. Factors such as strength, corrosion resistance and thermal conductivity should be considered when
There are multiple reasons to use black oxide treatment for die castings, and it can provide a variety of benefits to the final product. Black oxide treatment, also known as blackening or blackening treatment, is a chemically converted coating that can be applied to a variety of metal surfaces, including die castings. Some of the reasons
Aluminum thin wall die casting is a manufacturing process that generates parts that provide superior strength-to-weight ratios when compared to parts produced through other manufacturing methods. Aluminum die thin wall casting is also an efficient and economical process that can create a nearly unlimited amount of unique product shapes and sizes for industries throughout the world. Aluminum thin walled casts are also commonly used to supplement the aesthetic appeal of its surrounding part.
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