Die casting is a manufacturing process that uses high pressure to inject liquid metal into a reusable steel die. Rapid cooling solidifies the metal into a final shape.
More details about die casting alloys can be found on the diecastingdesign.org/alloys webpage.
The earliest example of a die casting by pressure injection (as opposed to gravity pressure) occurred in the mid-1800s. A patent was awarded to Sturges in 1849 for the first manually operated machine for casting printing type. This process was limited to printer’s type for the next 20 years, but development of other shapes began to increase toward the end of the century. By 1892, commercial applications included parts for phonographs and cash registers, and mass production of many types of parts began in the early 1900s.
The first die casting alloys were various compositions of tin and lead, but their use declined with the introduction of zinc and aluminum alloys in 1914. Magnesium and copper alloys quickly followed, and by the 1930s, many of the modern alloys still in use today became available.
The die casting process has evolved from the original low-pressure injection method to techniques including high-pressure casting (at forces exceeding 4500 pounds per square inch or 31 megapascals), squeeze casting, and semi-solid die casting. These modern processes are capable of producing high integrity, near net-shape castings with excellent surface finishes.
Die castings are used in every industry. Some of the industries that use large numbers of die castings are:
Examples of die castings can be found on the Casting Award Winners page of this website.
Die casting machine sizes are given in tons (or metric tonnes). This refers to the clamping force, holding the dies halves together, when the machine is closed. So a 900 ton die casting machine would have 900 tons of force holding the die halves together when metal is injected.
Die casters can be found using the Die Casting Companies Directory.
As with any manufacturing process there is an impact on the environment. Melting metal and running machines require significant amounts of energy and wastewater needs to be properly treated. Die casting limits the overall impact on the environment by using a significant amount of recycled materials (which is less energy intensive to produce) and producing thin walled, light weight components (which reduce the fuel consumption on cars and trucks).
Die castings are recyclable components with engineering advantages not available in other metalforming processes. The major cost and performance benefits of parts consolidation possible with plastic components can be carried forward in die casting designs with additional advantages.
Over 95% of the aluminum die castings produced in North America are made of post-consumer recycled aluminum. Since the production of recycled aluminum alloy requires approximately 5% as much energy as primary aluminum production, there is a dramatic conservation of nonrenewable energy resources.
The basis for the die casting process is using high pressures to inject liquid metal into a reusable steel die. There are some variations to the process, such as: hot chamber die casting, cold chamber die casting, structural (or high integrity) die casting.
Hot chamber refers to the relative temperature of the injection mechanism. In the hot chamber process the injection mechanism is submerged in liquid metal inside the melting furnace. Because the metal does not need to be transferred to the injection mechanism production rates can be higher. The hot chamber process is limited to metals with lower melting temperatures or don’t react with steel, such as: zinc, lead, tin, and some magnesium alloys.
Cold chamber refers to the relative temperature of the injection mechanism. In the cold chamber process metal is melted in an external furnace and transported to the injection mechanism when the machine is ready to make a casting. Because the metal needs to be transferred to the injection mechanism production rates are typically lower than the hot chamber process. Aluminum, copper, some magnesium, and high aluminum content zinc alloys are produced using the cold chamber die casting process.
Structural die castings (sometimes referred to as high integrity die casting) are variations of the die casting process used to produce castings for specific applications (typically requiring minimized gas porosity in the casting). These include:
Additional information on design considerations can be found on the diecastingdesign.org website.
The following are some of the considerations taken into account during die design.
Modern die cast engineers utilize a combination of calculations, fluid flow simulation, and finite element analysis to ensure the die is properly designed to make quality die castings.
The die is made from alloy tool steels in at least two sections – the stationary (or cover) die half and ejector die half. Modern dies may also have moveable slides, cores or other sections to produce holes, threads, and other desired shapes in the casting. The stationary die half has a hole to allow metal to enter the die and fill the cavity. The ejector half usually contains the runners (passageways) and gates (inlets) that route molten metal to the cavity. Dies also include locking pins to secure the two halves, ejector pins to help remove cast parts, and water or oil channels for cooling the die.