I. Research Background
Aluminum and copper molten metals possess strong permeability and chemical corrosiveness. Traditional clay graphite crucibles have a short service life, with the molten material prone to seeping in. Pure graphite crucibles suffer severe oxidation loss in the high-temperature air environment. The silicon carbide reinforced graphite crucible uses flake graphite as the base material and is modified with SiC particles, making it the mainstream consumable in the aluminum and copper casting industry at present. This paper combines the measured data from over 30 aluminum and copper casting factories in China, conducts a horizontal comparison of the comprehensive performance of the three mainstream crucibles, and calculates the long-term comprehensive cost.
II. Comparison of the Materials and Properties of the Three Types of Crucibles
1. Clay Composite Graphite Crucible: Graphite combined with refractory clay, low cost, high porosity, severe aluminum liquid penetration, suitable only for low-frequency and small-scale melting;
2. Ordinary High-Purity Graphite Crucible: No clay admixture, high purity, but without antioxidant reinforcing phase, the outer wall rapidly powderizes and cracks in the 1400℃ air environment;
3. SiC Reinforced Graphite Crucible: Graphite base with 35%-60% silicon carbide particles uniformly distributed, densified molding, significantly improved three indicators of resisting aluminum and copper erosion, anti-oxidation, and thermal shock resistance.
III. Actual Factory Service Life Measurement Data
Test conditions: Medium-frequency induction furnace, continuous melting of 6061 aluminum alloy and T2 copper, 8-hour continuous production per day
1. Clay Graphite Crucible: On average, 85 out of 6061 aluminum alloy melting and 62 out of 2200 copper melting were scrapped;
2. Ordinary High-Purity Graphite Crucible: 160 out of 6061 aluminum alloy melting and 125 out of 2200 copper melting were scrapped;
3. SiC Reinforced Graphite Crucible: 295 out of 6061 aluminum alloy melting and 268 out of 2200 copper melting were scrapped.
IV. Analysis of the Full-Cycle Usage Cost
Based on an average daily melting of 10 furnaces and a total annual production of 300 days: The clay crucible has a low purchase price, but the replacement frequency is high, along with the labor loss during machine shutdown for changing the crucible, metal seepage loss, and the annual comprehensive cost is the highest; The SiC crucible has a purchase price 40% higher, but the service life is increased by 2.8-4 times, the machine shutdown loss is reduced by 70%, the metal recovery rate is increased by 0.4%, and medium-sized casting factories can save 32,000 yuan or more in consumables and raw material costs throughout the year.
V. Research Conclusion
For large-scale aluminum and copper smelting production lines, the SiC reinforced graphite crucible has the best overall cost performance; For short-term, small-scale, and low-budget temporary smelting scenarios, the clay graphite crucible can be selected; High-purity SiC-free graphite crucibles are only suitable for vacuum sealed smelting environments and are not suitable for continuous aluminum and copper smelting in the air atmosphere.
