New High Fluidity Zinc Die Casting Alloy Covered by ASTM Standard

ASTM International has announced that a new high fluidity zinc die casting alloy is now covered by ASTM standard B989, Specification for High Fluidity (HF) Zinc-Aluminum Alloy in Ingot Form for Thin Wall Die Castings. A new standard was needed because the composition of this alloy is unique. ASTM International, formerly known as the American Society for Testing and Materials (ASTM), is an organization of more than 30,000 members in 150 countries that has created 12,000 global voluntary consensus standards on test methods, specifications, guides and practices for both industries and governments. 

The HF Zinc-Aluminum Alloy is based on ZAMAK alloys, one of two groups of zinc casting alloys made of approximately 4% aluminum that provide excellent die castability. The other family is the ZA alloys, high-strength alloys which contain higher amounts of aluminum. 

The HF Zinc-Aluminum Alloy was developed through the joint efforts of the Cast Metals Coalition, the North American Die Casting Association (NADCA), the International Zinc Association (IZA), and the U.S. Department of Energy. According to the IZA, the HF Zinc-Aluminum Alloy has 40% more fluidity than Alloy 7, which until now was one of the most successful high fluidity zinc alloys. The new HF Alloy also has comparable physical, mechanical, and corrosion properties to Alloy 7 and Alloy 3, comparable fluidity and castability to Superloy/GDSL, and is best suited for casting parts with section thickness less than 0.45 mm. It is also designed for parts that are difficult to fill or that have high surface finish requirements. The new alloy exceeds minimum thickness targets and allows for casting parts with a wall thickness as thin as 0.25 mm.  

Die castings are an important product of the metalworking industry, found in everything from cars to electronics to building materials. Die castings made from zinc alloys offer significant advantages over those made from polymers or other metals, including:

• Strength, durability, formability
• Excellent thermal and electrical conductivity
• Castability at moderate temperatures which reduces energy costs and extends tool life
• Work with almost all casting and finishing processes
• Easier and minimized machining
• High casting fluidity
• Recyclable

Each of the different zinc casting alloys requires a very specific formulation to produce the expected characteristics. HF Zinc-Aluminum Alloy, for example, also contains magnesium, copper, iron, lead, cadmium, and tin. The exact percentages of each element, as well as the purity of the zinc and the absence of contaminants must be verified throughout the manufacturing process to guarantee the integrity of the finished product.

Optical Emission Spectrometry (OES) is a widely-used, industry-established technology for accomplishing the process and quality control required for metallurgy. OES instruments are capable of providing rapid qualitative and quantitative analysis to correct chemistry inconsistent in real-time and are an optimal solution for zinc casting alloy elemental analysis.