Graphite Crucible for Metal Melting
Three material types cover the graphite crucible. Pure graphite crucible has a carbon content generally above 99.9% and is made from pure artificial graphite. It is recommended for electric furnaces and should be used in other furnace types only with care. Clay graphite crucible is made from natural graphite powder mixed with clay, other binders and oxidation-resistant additives, rotationally formed — it suits factories with low labour cost and a low operating rate. Silicon carbide graphite crucible is also rotationally formed, from natural graphite powder, silicon carbide and aluminum oxide with an anti-oxidation layer added; its service life is about 3–8 times that of clay graphite and its bulk density is between 1.78 and 1.9.
1. Three material grades, so the crucible can be matched to furnace type and duty cycle.
2. Silicon carbide graphite type with a service life about 3–8 times that of clay graphite.
3. High bulk density of 1.78–1.9 in the silicon carbide type, which is what gives it the erosion resistance.
4. Anti-oxidation layer applied to the silicon carbide type.
5. Standard sizes from 1 kg to 10 kg aluminum capacity, plus larger on request.
| product name | Product Size | |||||
|---|---|---|---|---|---|---|
| Upper outer diameter | Step | Bottom Outer Diameter | Inner Diameter | H Height | Inner Height | |
| 1kg graphite crucible | 58 | 12 | 47 | 34 | 88 | 78 |
| 2kg graphite crucible | 65 | 13 | 58 | 42 | 110 | 98 |
| 2.5kg graphite crucible | 65 | 13 | 58 | 42 | 125 | 113 |
| 3kg graphite crucible | 85 | 14 | 75 | 57 | 105 | 95 |
| 4kg graphite crucible | 85 | 14 | 76.5 | 57 | 130 | 118 |
| 5kg graphite crucible | 100 | 15 | 88 | 70 | 130 | 118 |
| 5.5kg graphite crucible | 105 | 18 | 91 | 70 | 156 | 142 |
| 6kg crucible A | 110 | 18 | 98 | 75 | 180 | 164 |
| 6kg crucible B | 115 | 18 | 101 | 75 | 180 | 164 |
| 8kg graphite crucible | 120 | 20 | 110 | 85 | 180 | 160 |
| 10kg graphite crucible | 125 | 20 | 110 | 85 | 185 | 164 |
| All sizes can be customized | ||||||
Physical and Chemical Indicators of Silicon Carbide Graphite Crucible
| physical properties | Max Temperature | Porosity | Bulk density | Fire resistance |
| 1800℃ | ≤30% | ≥1.71g/cm2 | ≥8.55Mpa | |
| chemical composition | C | Sic | AL203 | SIO2 |
| 45% | 23% | 26% | 6% |
Graphite crucibles are used wherever aluminum is melted in batches rather than continuously — foundries, die-casting cells, test and laboratory melting, and precious or special alloy production.
1. Crucible furnaces and induction furnaces for aluminum melting.
2. Die-casting cells holding a small molten reserve.
3. High-temperature test smelting and alloy development.
4. Small-batch remelt where a full furnace is uneconomic.
5. Larger plants will generally use a fixed aluminum melting and holding furnace instead.
1. Storage and Handling
Store the graphite crucible in a dry, well-ventilated environment to prevent moisture absorption. Handle it carefully during transportation and installation. Avoid dropping, striking, or rolling the crucible to protect its surface coating.
2. Preheating Before Use
Gradually increase the heating temperature from low to high, rotating the crucible regularly to ensure even heating and remove internal moisture. The preheating temperature should gradually reach above 500°C. Improper preheating may cause peeling or cracking due to thermal shock.
3. Furnace Installation and Heating
Select a furnace that matches the crucible specifications and ensure adequate clearance around the crucible. The furnace cover must not press against the crucible body. During operation, direct the burner flame toward the crucible base rather than the sidewall to prevent localized overheating.
4. Material Charging and Melting
Add metal materials gradually, preferably in smaller pieces, and avoid overloading or tightly packing large pieces to prevent mechanical damage. Use properly fitted crucible tongs during loading and unloading. Continuous operation and periodic rotation help maintain uniform heating and extend service life.
5. Flux and Alloy Modifier Addition
Add refining fluxes and alloy modifiers only after the metal has melted. Never add them to an empty crucible or before melting. Place bulk flux near the center of the crucible, approximately one-third of the way up from the bottom, and ensure powdered flux does not directly contact the crucible walls. Avoid spilling flux into the furnace, as it may corrode the crucible's outer surface.
Use only the minimum recommended amount of compatible flux and stir the molten metal promptly after addition. Avoid excessive melt temperatures and prolonged contact with corrosive refining agents, particularly fluoride-containing modifiers, sodium-rich or phosphorus-rich aluminum dross, which can accelerate crucible erosion.
6. Slag Removal and Cleaning
Remove slag and residue from the crucible walls daily, preferably while the crucible is still hot and the slag remains soft. Use rounded cleaning tools that match the curvature of the inner wall. Pay particular attention to removing residue after the first heating and use, as accumulated slag becomes harder to remove over time. Avoid forceful scraping or impact.
7. Routine Maintenance
Inspect the crucible regularly for surface coating damage, cracks, and signs of corrosion. Maintain proper heating temperatures, control flux additions, and clean the crucible after each operating shift to reduce chemical erosion and prolong service life.
