How to control impurity content and ensure material purity during the production of zinc alloy metal dog buckles?
Release Time : 2026-02-25
In the production of zinc alloy metal dog buckles, controlling impurity content to ensure material purity is crucial for stable product performance and extended service life. The purity of the zinc alloy directly affects its corrosion resistance, mechanical strength, and surface treatment effectiveness. Excessive levels of impurities such as iron, lead, and cadmium not only reduce the material's susceptibility to intergranular corrosion but can also lead to cracking, deformation, and ultimately, the buckle's load-bearing capacity and durability. Therefore, a systematic impurity control system must be established throughout the entire production process, from raw material selection to final production.
Raw material procurement is the first line of defense in impurity control. Manufacturers must rigorously screen suppliers, prioritizing ultra-high purity zinc ingots as the base material and ensuring that alloying elements such as aluminum, magnesium, and copper meet specific proportion standards. For example, the aluminum content is typically controlled at around 4%, which improves the material's mechanical properties and prevents impurities from being introduced due to compositional deviations. Before raw materials are stored, they undergo professional testing, verifying purity through spectral analysis or chemical titration to prevent the use of zinc ingots with excessive iron content or surface corrosion, thus reducing the risk of impurity introduction at the source.
The raw material storage environment is equally crucial for impurity control. Zinc alloy ingots must be stored in clean, dry, dedicated warehouses to avoid contact with humid air or industrial pollutants. Humid environments easily lead to the formation of white rust (zinc oxide) on the surface of zinc ingots, increasing metal loss and potentially introducing corrosive impurities such as chloride ions. Furthermore, warehouses need to be cleaned regularly to prevent dust and oil from adhering to the raw material surface, forming inclusions during subsequent smelting and affecting material purity.
The smelting process is the core of impurity control. Zinc alloys have a low melting point and good fluidity, but at high temperatures, they easily react with elements such as iron and oxygen to form oxide slag or intermetallic compounds. Therefore, smelting must be done in centralized furnaces, with precise temperature control (usually not exceeding 450℃) to avoid the volatilization loss of elements such as aluminum and magnesium, while minimizing the contact time between the iron crucible and the molten alloy, reducing the risk of iron impurities dissolving into the metal. The use of recycled materials (such as sprue material) must be strictly limited, generally not exceeding 30% of the total input, and must be screened, cleaned, and have surface oil and oxide layers removed before remelting to prevent secondary contamination.
Impurity control during die casting requires a focus on mold design and process parameter optimization. The design of mold runners and gates should avoid sharp bends to prevent turbulence during molten metal filling, which could trap gas or impurities from the mold surface. Die casting temperature, pressure, and speed must be coordinated: excessive temperature increases the amount of gas absorbed by the molten alloy, leading to porosity; insufficient pressure may cause undercasting, resulting in uneven density; and excessive speed can easily cause cold shuts. Optimizing process parameters through simulation software can ensure smooth molten metal filling of the cavity and reduce the chance of impurities entering the mold.
Post-processing is crucial for improving material purity. Burrs and flash must be removed immediately after demolding to prevent residues from embedding in the surface during subsequent processing. Thorough cleaning is required before surface treatment, using a combination of alkaline degreasing agents and ultrasonic cleaning to remove oil, mold release agents, and other organic impurities. Electroplating or spraying processes require the selection of highly corrosion-resistant plating materials (such as nickel and chromium), and pretreatment (such as pickling and activation) should be used to enhance plating adhesion and prevent blistering or peeling due to impurities. Quality inspection is the last line of defense in impurity control. Manufacturers need to establish a multi-level inspection system, including raw material composition analysis, die-cast part dimensional measurement, surface defect inspection, and non-destructive testing of internal defects (such as X-ray inspection). For critical components, mechanical property tests (such as tensile strength and hardness) and corrosion resistance tests (such as salt spray tests) are also required to ensure that impurity content does not exceed industry standards. For example, EU RoHS certification requires lead content to be less than 0.1% and cadmium content to be less than 0.01%, and manufacturers need to ensure compliance through regular testing and internal sampling.
Continuous improvement and employee training are the long-term guarantees for impurity control. Manufacturers need to regularly evaluate their processes and introduce more advanced purification technologies (such as vacuum melting) or testing equipment (such as laser-induced breakdown spectrometers) to improve the accuracy of impurity control. At the same time, strengthening employee skills training ensures they are familiar with impurity sources, control methods, and emergency response measures, fostering a quality control culture with full employee participation. Through a systematic impurity control system, the material purity of zinc alloy metal dog buckles is guaranteed, significantly improving product performance and market competitiveness.