As a manufacturing process, die casting is famous for its ability to manufacture parts with high uniformity, close to design accuracy and high-quality surface finish. In many cases, die casting can reduce or eliminate the demand for post-processing, improve the cost-effectiveness of the process and shorten the manufacturing time. Although it is difficult to mold solid cast metals, such as some steel grades, there are many other types that are very suitable for die casting methods. Here is everything you should know about alloy for die casting.
Molds are usually made of hardened steel, which are usually the most expensive components in die casting machines. These molds can handle a range of different alloy families and produce different results, but die casting is usually more effective on metals with lower melting temperatures. For this reason, common die casting alloys are divided into several categories according to their composition and material properties.
Zinc based materials are relatively easy to die cast and respond well to the die casting process. These materials consist of several specific proportions of metals. For example, a typical zinc based die casting consists of 86% zinc, 4% to 7% copper and 7% to 10% tin. A slightly higher tin ratio makes the parts more flexible, while the increased copper content improves the rigidity. The melting point of zinc alloys ranges from 700 to 800 degrees Fahrenheit.
Zinc alloy is usually used to replace cast iron or brass, but its tensile strength is often lower than that of more robust similar products. Unless specially strengthened during alloying, the strength of zinc based materials shall not exceed about 17000 psi. Therefore, cast zinc products are usually not used in applications involving high mechanical loads. Zinc castings may also be corroded by alkaline substances or brine and are often electroplated to maintain their luster under atmospheric conditions.
Alloys made with a large amount of tin as the base metal are most commonly used in applications requiring corrosion resistance, such as those involving the food industry or internal and external bearings. Although the proportion of metals in these alloys may vary greatly, a typical tin alloy consists of 90% tin, 6% antimony and 4% copper, which are added to improve the durability of the material. Tin alloy die castings usually weigh less than ten pounds and rarely exceed 1 / 32 inch thick. They are valued for their resistance to alkali, acid and water, but their tensile strength grade is relatively low, less than 8 pounds.
Bronze and brass alloys
Most bronze and brass die casting materials can be as effective as zinc based alloys, although small holes can only be drilled into the part after casting rather than during casting. Bronze and brass are commonly used in the manufacture of gaskets, camshaft components and decorative products (due to their color and potential for unique surface finish). Brass alloys usually consist of 60% copper, 40% zinc and 2% aluminum, but this mixture varies a lot. Bronze and brass pressure melting can provide products with durable surfaces and very accurate internal specifications.
Some copper cannot withstand the shrinkage caused by high-temperature processes, but despite these challenges, most of these alloys can still be used in products weighing up to 15 pounds and less than 1 / 32 or 1 inch thick. They are generally suitable for applications requiring a tensile strength of less than 8000 psi.
Die cast aluminum alloy is often used in automobile parts and gears. It was used to make surgical instruments in the past. They are generally stronger and lighter than most zinc based materials, but they are often more expensive to manufacture. The use of aluminum alloy helps to reduce the demand for finishing treatment such as electroplating. The common grade is a mixture of 92% aluminum and 8% copper. Magnesium can be added to this alloy to increase its tensile strength from about 21000 pounds per square inch to about 32000 pounds per square inch, while nickel can be added to increase stiffness and provide excellent surface finish. Melting point of
As a tin alloy, lead based materials tend to be used in applications where the tensile strength per square inch does not exceed 8000 pounds due to their corrosion resistance. Common applications include fire safety equipment, bearings and various decorative metal products. Producing parts under 15 pounds is relatively cheap, but lead alloys cannot be used in products in contact with food. Typical lead alloys may contain 90% lead and 10% antimony, and tin is also a common additive. The melting point is usually around 600 degrees Fahrenheit, and the thickness of the product rarely exceeds 1 / 32 inch.