Large Graphite Crucibles | High-Temperature-Resistant Crucibles Designed for Large-Capacity Industrial Smelting and Precious Metal Casting | NHD

▍Core Product Positioning

Jiangxi Ningheda’s large graphite crucibles differ from the small 1–5 kg jewelry-grade crucibles commonly found on the market; they are specifically designed for large-scale, continuous industrial production. Manufactured using isostatic pressing (CIP) or compression molding processes, these products feature a density of 1.72–1.85 g/cm³ and a dense, uniform internal structure. They can withstand the mechanical loads and thermal stresses of hundreds of kilograms of molten metal, ensuring long-term, stable operation under harsh conditions.

Perforated Graphite Crucible

Cylindrical Graphite Crucible

▍Advantages in Materials and Manufacturing Processes

• Carefully Selected Raw Materials

High-Purity Graphite: Graphite purity ≥99%, ash content ≤0.3% (standard grade)/≤0.1% (high-purity grade)

Specialty Asphalt Coke: A blend of high-quality petroleum coke and asphalt coke is used to optimize the degree of graphitization

Additive Formulation:Proprietary additives enhance oxidation resistance and mechanical strength

• Comparison of Molding Processes

• High-Temperature Graphitization Treatment

The crucible blank undergoes graphitization at high temperatures ranging from 2400°C to 3000°C, converting amorphous carbon into crystalline graphite, which significantly improves thermal conductivity, reduces electrical resistivity, and enhances chemical inertness.

Beveled Graphite Crucible

Bottom-Hole Graphite Crucible

Tapered Graphite Crucible

▍Technical Specifications

Thick-Wall Graphite Crucible

Flanged Graphite Crucible

Slender Graphite Crucible

▍Why Choose Jiangxi Ningheda’s Large Graphite Crucibles?

• Advantage 1: Extra-Large Capacity, Industrial-Grade Load-Bearing Capacity Unlike the small, jewelry-grade crucibles on the market (1–5 kg), Ningheda products start at 50 kg per unit and can reach up to 500 kg, designed specifically for large induction furnaces, resistance furnaces, and fuel-fired furnaces. The thick-walled construction (wall thickness options range from 15 to 50 mm) can withstand the static pressure and thermal shock of hundreds of kilograms of molten metal, eliminating the risk of deformation or cracking.

  
  

• Advantage 2: 30% improvement in thermal conductivity, leading to energy savings and reduced consumption. Graphite has a thermal conductivity of 100–130 W/(m·K), which is more than five times that of ceramic materials. Heat is transferred quickly and evenly, shortening melting time by 25%–30% and significantly reducing fuel or electricity consumption. Taking the smelting of a 200 kg aluminum ingot as an example, using Ningheda graphite crucibles can save approximately 15%–20% in energy costs compared to clay-lined graphite crucibles.

  
  

• Advantage 3: Chemical Inertness Ensures Metal Purity. At high temperatures, graphite does not react with aluminum, copper, gold, silver, platinum, or most alloys, thus preventing impurity contamination. High-purity products have ash content ≤0.05% and metal impurities ≤3 ppm, meeting the stringent purity requirements for semiconductor-grade silicon, photovoltaic polysilicon, aerospace high-temperature alloys, and other applications.

  
  

• Advantage 4: Excellent Thermal Shock Resistance, 40% Longer Service Life A low coefficient of thermal expansion (2.5–3.0 × 10⁻⁶/°C) combined with an optimized microstructure enables the crucible to withstand rapid cooling and heating cycles. Standard products withstand ≥50 thermal shock cycles, while high-purity grade products withstand ≥80 cycles, extending service life by more than 40% compared to traditional clay-graphite crucibles and reducing replacement frequency and production downtime losses.

  
  

• Advantage 5: Full-Size Customization for Precise Equipment Compatibility We offer various configurations, including cylindrical, barrel-shaped, conical, spouted, and lidded designs. Inner diameter, outer diameter, height, wall thickness, and bottom curvature can all be customized to match the dimensions of the customer’s furnace. We support CNC precision machining with a dimensional accuracy of ±0.5 mm, ensuring a perfect fit with induction and resistance furnaces and preventing uneven heat distribution or installation interference.

  
  

• Advantage 6: Direct from Manufacturer, Controllable Costs Jiangxi Ningheda New Materials Co., Ltd. possesses full-industry-chain capabilities, from raw material calcination to finished product processing. By eliminating middlemen, our prices are 30%–50% lower than those of imported brands. We support everything from small-batch samples (with no minimum order quantity) to large-scale OEM production, flexibly meeting the needs of all types of customers.

Conical Graphite Crucible

Short Graphite Crucible

Tall Graphite Crucible

▍Application Scenarios and Solutions

• Precious Metal (Gold, Silver, Platinum, Palladium) Refining

Typical Applications: Jewelry casting, electronic scrap recycling, catalyst recovery, dental alloys

Recommended Capacity: 50 kg–200 kg (High-Purity Grade)

Product Advantages: High-purity grade with ash content ≤0.1%, causing no contamination of precious metals; refining recovery rate ≥99.5%; suitable for vacuum induction melting and inert gas atmosphere protection

• Preparation of Carbon-Carbon Composites

Typical Applications: Aerospace thermal structural components, thermal fields in photovoltaic single-crystal furnaces, brake disc preforms

Recommended Capacity: Customized according to CVD/CVI furnace type

Product Advantages: Chemically inert, does not contaminate the carbon-carbon matrix; excellent high-temperature stability, with CVD process temperatures reaching 2000°C+; reusable, reducing production costs

• Semiconductor and Photovoltaic Materials

Typical Applications: Polysilicon ingot casting, monocrystalline silicon pulling, silicon carbide crystal growth

Recommended Capacity: 50 kg–100 kg (High-Purity Grade)

Product Advantages: Metal impurities ≤ 3 ppm, meeting the requirements for electronic-grade silicon feedstock; thermal shock resistance ensures temperature stability during crystal growth; customizable high-purity coatings to further reduce contamination

Metal Melting Graphite Crucible

Graphite Hot Zone Components

Photovoltaic Graphite Crucible

▍FAQ

• Q1: What is the difference between large graphite crucibles and small ones?

  A1: Large graphite crucibles (50 kg–500 kg) are specifically designed for industrial-scale continuous production. They feature thicker walls and a stronger structure, enabling them to withstand the load and thermal stress of hundreds of kilograms of molten metal. Small crucibles (1–5 kg) are suitable for light-duty applications such as jewelry making and laboratory work. Large crucibles are typically manufactured using isostatic pressing or die-pressing processes, resulting in higher density, greater strength, and a longer service life.

• Q2: What is the maximum operating temperature for graphite crucibles?

  A2: In air or an oxidizing atmosphere, the recommended maximum operating temperature should not exceed 800–1000°C (for continuous use). In an inert atmosphere (nitrogen, argon) or under vacuum conditions, graphite crucibles can operate stably up to 1,800°C and briefly reach 3,000°C. Exceeding the oxidation temperature limit will cause rapid graphite burnout; therefore, an anti-oxidation coating or atmosphere protection must be used.

• Q3: Which metals are suitable for melting in graphite crucibles?

  A3: They are suitable for melting the vast majority of non-ferrous metals and alloys, including: aluminum and aluminum alloys, copper and copper alloys (brass, bronze), precious metals such as gold, silver, platinum, and palladium, as well as certain low-melting-point ferrous metals. They are not suitable for melting: high-melting-point ferroalloys (>1600°C, severe erosion) and strong alkali metals (such as sodium and potassium, which react with graphite).

• Q4: How can I tell if a crucible needs to be replaced?

  A4: Replace immediately if any of the following conditions occur: ① Deep pits or grooves (>2 mm) appear on the inner wall (severe erosion); ② Visible cracks appear on the outer wall or bottom (risk of breakage); ③ The crucible is deformed or the bottom is bulging (reduced structural strength); ④ Metal leakage or permeation (increased porosity); ⑤ Under normal operating conditions, the service life has reached 80% of the rated value.

• Q5: Can non-standard sizes and shapes be customized?

  A5: Absolutely. We offer fully customized services, including: dimensions (inner diameter, outer diameter, height, wall thickness, bottom curvature), shapes (straight cylinder, barrel-shaped, conical, with spout, with lid, irregular shapes), purity (standard grade with ash content ≤0.3%, high-purity grade with ash content ≤0.1%), and surface treatments (anti-oxidation coating, anti-adhesion coating, polishing). Simply provide drawings or furnace dimensions, and our engineers will provide a design proposal and quote within 24 hours.

• Q6: How do I choose between graphite crucibles, silicon carbide (SiC) crucibles, and ceramic crucibles?

  A6: Each of the three materials has its own advantages:

  ① Graphite crucibles—offer the best thermal conductivity and the lowest cost, and are suitable for most non-ferrous metals, but have relatively poor oxidation resistance;

  ② SiC crucibles—offer the highest strength and best thermal shock resistance, and are suitable for high-frequency use in induction furnaces, but are more expensive;

  ③ Ceramic crucibles (alumina/zirconia)—offer the highest chemical inertness and are suitable for reactive metals, but have poor thermal conductivity and are highly brittle. For general industrial smelting (aluminum, copper, precious metals), graphite crucibles offer the best value for money.