Core Requirements for Raw Material and Composition Design
High-Purity Raw Material Selection: The casting of non-ferrous metal alloys (such as aluminum and copper alloys) requires metal ingots with a purity ≥99.7% (refer to GB/T 8733-2016). The content of impurity elements (such as Fe and Si) must be strictly controlled below 0.1% to avoid grain boundary embrittlement. For example, aerospace-grade 7075 aluminum alloy requires a Zn content of 5.6%~6.1% and a Mg content of 2.1%~2.5%. A composition deviation exceeding ±0.2% will result in a 10%~15% decrease in strength.
Precise Alloy Proportion Control: Employing intermediate alloy premixing technology ensures uniform distribution of trace elements (such as Ti and B). Taking copper alloys as an example, for every 0.1% increase in Sn addition, conductivity decreases by approximately 1.5% (data from the *Non-Ferrous Metals Processing Handbook*). Composition must be monitored in real-time using a spectrometer; composition fluctuations within the smelting furnace should be ≤±0.05%.
Key Parameters for Melting and Casting Processes
Temperature Management
Melting Temperature: Aluminum alloys are typically controlled at 700~750℃, and copper alloys at 1100~1200℃. Exceeding this temperature by 10℃ will exacerbate oxide slag formation.
Pouring Temperature: Adjusted according to alloy type. For example, the pouring temperature for ZL104 aluminum alloy is 680~720℃. Too low a temperature will lead to cold shut defects.
Gas and Inclusion Control
Argon refining (flow rate 0.5~1.5 L/min·kg) or flux covering (such as KCl+NaCl mixed salt) should be used to ensure a hydrogen content ≤0.15 mL/100g (refer to ASTM E29). Before casting, allow the mixture to stand for 5~10 minutes to allow inclusions to float to the surface; the slag layer thickness should be <3 mm.
Quality Inspection and Defect Prevention
Non-destructive Testing Standards
Ultrasonic testing (defect size >0.5 mm requires rework) and X-ray inspection (porosity <2% is acceptable) are industry-standard methods. For example, aluminum profiles for high-speed rail must meet the Class B testing requirements of EN 12004-2.
Common Defect Solutions
Shrinkage Cavities: Improved through mold temperature control (±5℃) and riser design (height ≥ 1.5 times the casting thickness).
Hot Cracking: Adding 0.01%~0.03% Sr or TiB₂ refines the grains and reduces the risk of cracking.
Equipment and Environmental Requirements
Smelting Equipment Selection
Medium-frequency induction furnaces (efficiency ≥85%) are superior to resistance furnaces and must be equipped with an automatic temperature control system (accuracy ±3℃). Casting machine pressure parameters should be adjusted according to alloy fluidity; for example, magnesium alloy die casting requires 150~300 MPa.
Workshop Environmental Control
Humidity must be <60%, dust concentration <5 mg/m³ (GBZ 2.1-2019) to prevent hydrogen absorption and oxidation of the metal.
