Bell Furnace
Factory-direct bell furnace for heat pipe copper powder sintering & powder metallurgy. N2/H2/NH3 atmosphere.
Product Description
In heat pipe manufacturing, the copper wick structure is the core component that drives capillary action and fluid return. The bell furnace — also known as a hood-type furnace — is the industry-standard equipment used to sinter this copper powder layer onto the inner wall of the copper tube.
The process follows a controlled sequence: copper powder is filled into the tube around a central mandrel, the loaded tubes are placed vertically inside the furnace, and the bell-shaped hood is lowered to seal the chamber. A protective atmosphere — typically nitrogen (N₂), hydrogen (H₂), or decomposed ammonia (NH₃) — is introduced to prevent oxidation. The furnace then ramps through a precise multi-stage temperature profile, reaching peak sintering temperatures between 850°C and 1000°C, bonding the copper powder particles into a dense, uniform wick structure.
After sintering, the furnace cools under continued atmosphere protection before the hood is raised for unloading. This sealed, atmosphere-controlled process ensures the wick structure achieves consistent porosity, thermal conductivity, and bond strength — all critical to heat pipe performance.
Atmosphere Control — N₂ Protection, H₂ Reduction & NH₃ Decomposition
Atmosphere control is the most critical variable in copper powder sintering. Oxygen contamination at sintering temperatures causes irreversible copper oxidation, destroying wick porosity and bonding quality. Our bell furnaces support three primary protective atmosphere configurations used in industrial heat pipe production:
Nitrogen (N₂) Protection
The most widely used atmosphere for copper sintering. Nitrogen creates an inert blanket inside the furnace chamber, effectively displacing oxygen and preventing surface oxidation throughout the entire heating and cooling cycle. Suitable for standard heat pipe wick sintering where reducing conditions are not required.
Hydrogen (H₂) Reduction
Hydrogen atmosphere provides both oxidation protection and active reduction of surface copper oxides already present on the powder. This results in a cleaner sintered surface, improved inter-particle bonding, and better thermal conductivity in the final wick structure. Recommended for high-performance heat pipe applications.
Decomposed Ammonia (NH₃)
Decomposed ammonia (a mixture of 75% H₂ and 25% N₂) combines the benefits of both nitrogen protection and hydrogen reduction, while offering lower operating costs compared to pure hydrogen supply. Widely used in high-volume heat pipe and powder metallurgy production lines.
Our gas control system supports programmable flow rate adjustment and atmosphere switching across heating stages, ensuring optimal sintering conditions throughout the full process cycle.
Technical Parameters
| Parameter | Specification |
| Max Temperature | 1000°C – 1200°C |
| Temperature Uniformity | ±1°C (within working zone ) |
| Atmosphere | N₂ / H₂ / NH₃ decomposition / Vacuum |
| Heating Element | Resistance wire / Silicon carbide (SiC) |
| Chamber Inner Diameter | 600mm – 1200mm (custom available) |
| Effective Height | 800mm – 2000mm (custom available ) |
| Temperature Control | PID + multi-segment programmable ramp PID |
| Power Supply | 380V / 3-phase |
| Cooling Method | Natural cooling / Forced water cooling |
Applications — Heat Pipe Sintering, Powder Metallurgy & Electronic Components
Our bell furnaces have been deployed across multiple industries requiring precision atmosphere sintering. Core application areas include:
Heat Pipe Copper Powder Sintering
The primary application. Bell furnaces are used to sinter the copper powder wick structure inside heat pipes for consumer electronics cooling modules, server thermal management, EV battery thermal systems, and industrial heat exchangers. Compatible with standard round heat pipes (Ø3–Ø12mm) and flat heat pipes.
Vapor Chamber (VC) Sintering
Bell furnaces support VC copper powder sintering processes, providing the high-temperature uniformity and atmosphere control required for vapor chamber wick layers used in high-power chip cooling applications.
Powder Metallurgy Components
Used for sintering structural metal components including copper-based bearings, bushings, and self-lubricating parts requiring controlled porosity and density.
Electronic Components & Magnetic Materials
Suitable for atmosphere sintering of soft magnetic cores, ceramic capacitors, and other electronic components requiring oxidation-free thermal processing.
Custom Bell Furnace Configurations & Factory Direct Supply
thermalmachinery supplies bell furnaces direct from our manufacturing facility in Kunshan, Jiangsu. All furnaces are custom-configured to match your specific sintering process parameters, production volume, and facility requirements.
Customization options include
• Chamber dimensions (inner diameter & effective height)
• Maximum temperature rating
• Atmosphere type and gas control system
• Heating element selection (resistance wire / SiC)
• Cooling method (natural / forced water cooling)
• Temperature control program (number of segments, ramp rates)
• Loading fixtures and tube holder design
• Integration with existing heat pipe production line
We have supplied bell furnaces to leading heat pipe manufacturers including Nidec, EVERWIN PRECISION, and VIESSMANN, supporting sintering lines with daily output from 500 to 300,000+ pieces.
OEM and ODM configurations are available. Lead time, pricing, and technical consultation are available upon request.
Applications — Heat Pipe Sintering, Powder Metallurgy & Electronic Components
Our bell furnaces have been deployed across multiple industries requiring precision atmosphere sintering. Core application areas include:
Heat Pipe Copper Powder Sintering
The primary application. Bell furnaces are used to sinter the copper powder wick structure inside heat pipes for consumer electronics cooling modules, server thermal management, EV battery thermal systems, and industrial heat exchangers. Compatible with standard round heat pipes (Ø3–Ø12mm) and flat heat pipes.
Vapor Chamber (VC) Sintering
Bell furnaces support VC copper powder sintering processes, providing the high-temperature uniformity and atmosphere control required for vapor chamber wick layers used in high-power chip cooling applications.
Powder Metallurgy Components
Used for sintering structural metal components including copper-based bearings, bushings, and self-lubricating parts requiring controlled porosity and density.
Electronic Components & Magnetic Materials
Suitable for atmosphere sintering of soft magnetic cores, ceramic capacitors, and other electronic components requiring oxidation-free thermal processing.
Custom Bell Furnace Configurations & Factory Direct Supply
thermalmachinery supplies bell furnaces direct from our manufacturing facility in Kunshan, Jiangsu. All furnaces are custom-configured to match your specific sintering process parameters, production volume, and facility requirements.
Customization options include
• Chamber dimensions (inner diameter & effective height)
• Maximum temperature rating
• Atmosphere type and gas control system
• Heating element selection (resistance wire / SiC)
• Cooling method (natural / forced water cooling)
• Temperature control program (number of segments, ramp rates)
• Loading fixtures and tube holder design
• Integration with existing heat pipe production line
We have supplied bell furnaces to leading heat pipe manufacturers including Nidec, EVERWIN PRECISION, and VIESSMANN, supporting sintering lines with daily output from 500 to 300,000+ pieces.
OEM and ODM configurations are available. Lead time, pricing, and technical consultation are available upon request.
FAQ
What is a bell furnace and how is it different from a regular box furnace?
A bell furnace (also called a hood-type furnace) features a vertically lifting bell-shaped hood that seals over a fixed base loaded with product. Unlike a box furnace where trays are pushed in horizontally, the bell furnace allows large batches of vertically-standing copper tubes to be sintered simultaneously with excellent temperature uniformity and atmosphere sealing. This makes it the preferred choice for high-volume heat pipe copper powder sintering lines.
What atmosphere gases does your bell furnace support?
Our bell furnaces support nitrogen (N2) protection, hydrogen (H2) reduction, decomposed ammonia (NH3, a 75% H2 / 25% N2 mixture), and vacuum operation. The gas control system allows programmable flow rate adjustment and atmosphere switching between heating stages. The right atmosphere depends on your copper powder spec and wick performance requirements — our engineering team can advise based on your process.
What is the typical sintering temperature profile for heat pipe copper powder?
A standard cycle involves four stages: a low-temperature drying/burnout stage (200-400°C) to remove binder and moisture, a ramp-up stage, a peak sintering stage at 850-1000°C held for 30-90 minutes depending on powder spec and wick thickness, and a controlled cooling stage under continued atmosphere protection. Our furnaces support fully programmable multi-segment temperature profiles via PID control.
How many heat pipes can be sintered per batch?
Batch capacity depends on chamber size and your heat pipe dimensions. For a standard bell furnace with 1000mm inner diameter and 1500mm effective height, a single batch typically accommodates 800-2,000 heat pipes (O.D. 6-8mm, length 150-500mm) depending on fixture design. We custom-engineer the loading fixtures for your specific tube dimensions to maximize utilization per batch.
Can the bell furnace also be used for vapor chamber (VC) sintering?
Yes. Bell furnaces can be configured for vapor chamber copper powder sintering, though VC sintering often requires customized fixture designs to hold the flat VC plates in the correct orientation. For VC diffusion bonding (a higher-pressure process), we offer a separate vacuum diffusion bonding furnace. Contact us to discuss your specific VC sintering process requirements.