The process of refining and purification is critical in the production of pure and high-quality zinc alloy die casting parts. Static clarification, chloride treatment, inert gas blowing, and filtration are some of the methods used to purify zinc alloy. In this article, we will discuss some of the most commonly used purification treatments for zinc alloy die casting.

Treatment of Zinc Alloy Die Casting to Remove Impurities

1. Chloride treatment
Chloride treatment is one of the most widely used methods. As soon as the alloy is melted, press 0.1% – 0.2% chlorination or 3.5% to 4.5% chloroethane into the bell jar and slowly stir it for a couple of minutes.

2. Metal liquid filtered through a fine ceramic filter
By filtering molten metal through fine-grained ceramics, a better purification effect can be achieved as well. Using a filter with an average particle size of 2-35 microns and a layer thickness of 105 microns, it is possible to remove nearly 90% of the oxides and 85% of the metal compounds in za4-1 alloy. When in use, the filter is placed in the bell jar and heated to 5000 degrees Celsius before being placed in the holding furnace or ladle to collect the liquid. Because rare earth elements are relatively active chemical elements, their chemical properties are also relatively active. When combined with impurities such as O, N, and h, they can form compounds with a low relative density and a high melting point. These compounds, as well as slag, can be easily removed from liquid metal by heating it.

3. Refining Agent (also known as a refinery agent)
The use of a refining agent in a variety of casting furnaces helps to refine, protect, and remove slag from molten metal, allowing for the production of high purity products and the purification of the melt. Hexachloroethane, zinc oxide, rare earth elements, inert gas, and other refining agents are commonly used in the refining of zinc alloys, as are other refining agents. Before refining, the tools should be coated with a protective coating to prevent impurities, particularly iron, from infiltrating into the liquid alloy. The coating is primarily made up of zinc oxide, fossil powder, water glass, and water, among other ingredients.

- Because it is non-hygroscopic, it does not melt and is less corrosive than other chemicals. It is also easy to preserve. A wide range of casting alloys can benefit from the use of this compound instead of chloride refining agent.
- Zinc oxide flux is a type of casting raw material and auxiliary material that is primarily used in the removal of slag and the refining of zinc alloys. Before use, zinc oxide is remelted and dried in a drying oven at 100-130 degrees Celsius. It is used in Zn-containing alloys as well as alloys where there are no strict requirements for Zn impurities. In contrast, it has the disadvantage of producing a large amount of harmful gases during the manufacturing process, and environmental protection is extremely inadequate. The slag removal and refining effect of zinc alloy flux is insufficient, resulting in the impurities and bubbles in the alloy liquid not being completely removed, as well as an increase in the amount of waste products produced during die casting.
- Because rare earth elements are relatively active chemical elements, their chemical properties are also relatively active.  When combined with impurities such as 0, N, and h, they can form compounds with a low relative density and a high melting point. The majority of the time, these compounds are easily removed from liquid metal along with slag in order to achieve refining effect.
- Inert gases, such as nitrogen or argon, are low-cost, pollution-free, and can be used in a variety of alloys because of their purity.

The degassing and slag removal properties of the alloy liquid are enhanced by the use of the refining agent. It has been reported that when the chlorination press is pressed into the bell jar at 450-470 degrees Celsius, nearly 80% of the oxides and 70% of the intermetallic compounds in the zinc alloy liquid are removed, thereby ensuring the quality of the alloy produced. Experimental evidence, on the other hand, has demonstrated that the use of chlorination (0.12% of the total amount of refining metal) increases the melting loss rate of the alloy and results in a significant amount of smoke and ammonia gas being produced during the process, thereby deteriorating the operating environment. In many cases, static clarification is the only method available for producing ingots with a compact cross-section structure and free of slag and inclusions. As a result, the amount of recycled materials used in the slag making operation and the amount of chlorination that must be added can be calculated based on the amount of slag produced.