High-Purity Graphite Crucible for Gold and Silver Melting
Product Overview
Our high-purity graphite crucibles are specifically engineered for melting and refining precious metals including gold, silver, platinum, and palladium. Manufactured from dense, high-purity isostatic graphite with ash content below 200 ppm, these crucibles ensure no contamination of valuable noble metals during melting at temperatures up to 1600°C. The dense, fine-grain structure resists thermal shock, prevents metal penetration, and provides a long service life in induction melting furnaces and torch melting applications used by jewelry manufacturers, refineries, and dental labs.
When melting precious metals, even trace contamination can significantly reduce alloy value and jewelry quality. Graphite is the ideal crucible material because it does not react with gold, silver, or platinum, does not introduce metallic impurities, and can be cast into precise wall thicknesses for efficient heat transfer. At Jincheng Graphite, we supply a full range of precious metal melting crucibles from small 50-gram assay crucibles to 50-kilogram foundry crucibles, with optional SiC coating for extended life in platinum melting.
Key Features
- Ultra-high purity graphite - ash content < 200 ppm prevents noble metal contamination
- Dense, impermeable walls - low porosity prevents metal seepage and crucible failure
- Excellent thermal shock resistance - survives rapid heating and quenching without cracking
- High thermal conductivity - fast, efficient melting in induction and resistance furnaces
- Precise wall thickness - optimized for heat transfer while maintaining structural strength
- Wide size range - from 50 g assay crucibles to 50 kg industrial melting crucibles
- Smooth inner surface - easy pouring and minimal metal retention after melting
- Optional SiC coating - for platinum and palladium melting at higher temperatures
Technical Specifications
| Parameter | Value |
|---|---|
| Material | High-purity isostatic graphite |
| Bulk Density | 1.78 - 1.85 g/cm³ |
| Shore Hardness | 60 - 70 HS |
| Flexural Strength | 45 - 60 MPa |
| Ash Content | < 200 ppm (ultra-pure grade < 50 ppm) |
| Max Temperature | 1600°C (gold/silver), 1800°C (platinum with SiC coating) |
| Available Capacities | 50 g, 100 g, 250 g, 500 g, 1 kg, 2 kg, 5 kg, 10 kg, 25 kg, 50 kg |
| Wall Thickness | 3 - 10 mm (size-dependent) |
| Porosity | < 12% |
| Thermal Conductivity | 100 - 130 W/(m·K) |
| Dimensional Tolerance | ±0.5 mm |
| Finish | machined outside, smooth inside |
Applications
- Gold melting and casting - jewelry casting, gold bar refining, and dental gold alloys
- Silver melting - silver jewelry, silverware, and silver granulation
- Platinum and palladium melting - platinum jewelry and catalyst recycling
- Precious metal assay - laboratory fire assay and cupellation crucibles
- Dental alloy melting - cobalt-chromium and gold dental alloy casting
- Electronics precious metal recycling - refining of gold and silver from electronic scrap
Why Choose Jincheng Graphite?
- Purity guaranteed - every crucible batch tested for ash content and metal contamination
- Jewelry and refinery trust - used by goldsmiths, refineries, and dental labs worldwide
- Wide size selection - from tiny assay crucibles to large foundry melting crucibles
- Custom geometries - lip designs, pouring spouts, and holder-compatible shapes available
- Competitive pricing - factory-direct pricing with no middleman markup
- Fast shipping - standard crucibles in stock for immediate dispatch
- SiC coating option - extend crucible life for platinum and high-temperature applications
- Export packaging - protective foam packaging for safe worldwide delivery
FAQ
Q: Will a graphite crucible contaminate my gold or silver?
A: No. Our high-purity crucibles have ash content below 200 ppm, and graphite does not chemically react with gold, silver, or platinum. This is why graphite is the traditional crucible material for precious metal melting. Always use a high-purity grade, not a low-grade industrial crucible, for precious metal work.
Q: How many melts will a graphite crucible last?
A: Under normal gold/silver melting at 1100-1200°C, a graphite crucible typically lasts 20-50 melts before wall thinning or cracking requires replacement. Crucible life depends on melting temperature, holding time, alloy composition, and whether the crucible is cleaned between uses.
Q: Can you make crucibles with a pouring lip or spout?
A: Yes. We can machine pouring spouts, lip designs, and holder-compatible outer shapes to match your specific furnace or tong setup. Send us your requirements or a drawing.
Q: Do you offer ultra-pure crucibles for laboratory assay work?
A: Yes. We offer an ultra-pure grade with ash content below 50 ppm specifically for fire assay, cupellation, and research laboratory applications where absolute purity is required.
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