Lead-free zinc alloys can be used to create a variety of items—from gears for toys to antique car parts
Most people are familiar with zinc. They know it’s a dietary supplement that helps boost their immune system. However, zinc also is used to make alloys. Brass, for example, typically contains 55 percent to 95 percent copper, with the remainder made up by zinc. Zinc also is used to produce die-casting alloys, and it is often alloyed with lead and tin to make solder, which has a low melting point and is used to join electrical components and pipes.
Like lead-free pewter alloys, lead-free zinc alloys are useful for many types of spin casting applications. Spin casting uses centrifugal force to produce parts. During the process, a mold rotates on its axis while molten metal is poured into it. The centrifugal force pulls the metal into the furthest corners of the mold, which makes fine details stand out. Spin casting is a quick and economical alternative to die casting, especially for short-run parts, prototypes, and high-volume production runs of novelty and promotional items.
People who restore antiques often have trouble finding certain types of parts. Take old toys, for example. It might be easy to sand and paint the outside to look like new, but the inner gears were likely lost long ago or could be too old to function properly. Spin casting with zinc alloys can help re-create those parts, as well as custom castings for antique cars, such as moldings, light bezels, dashboard parts, manufacturer logos and even certain engine parts.
Lead-free zinc alloys have a higher melting point than their lead-free pewter counterparts, so manufacturers must have equipment that can generate the temperature needed to melt zinc. Pewter generally begins to soften around 470 degrees Fahrenheit and reaches a fully molten state around 560 degrees Fahrenheit. Ideal casting temperatures are generally a bit higher to ensure the metal is completely molten so it will fill the mold completely, reaching into all crevices before it begins to harden. Zinc alloys, on the other hand, have a melting point of about 787 degrees Fahrenheit.
NEY Metals & Alloys, Brooklyn, N.Y., can provide manufacturers with several options for lead-free zinc alloys. NEY’s S1 zinc alloy is ideal for spin casting with silicon molds and is made up of 90 to 94 percent zinc, as well as proprietary grain refiners for improved casting properties. It works well for designs with thick cross sections or minimal detail. The company also produces an economical alternative to the S1 alloy, called S1A. For parts that require thin cross sections and fine detail, NEY offers its J1 zinc spin casting alloy, which also is made up of between 90 and 94 percent zinc and contains proprietary grain refiners for improved casting properties. S1, S1A and J1 are all sold in ingot form.
Growing concern about lead’s harmful effects on the human body has resulted in more stringent regulation of lead content in items that will come into contact with humans, particularly children. In addition to their casting properties, these zinc alloys are classified as lead free and can be used to help manufacturers meet or exceed requirements for lead content.