The metallic HTK range of Carbolite high temperature furnaces consists of metal heaters made of Molybdenum or Tungsten.
The HTK series, made of metal, is available in four distinct sizes. The smaller HTKs with capacities of 8 and 25 liters are usually used in laboratories for research and development. The larger 80 and 120-litre furnaces are mostly utilized as pilot manufacturing systems or for large-scale production. The front door design of these furnaces allows for easy loading and unloading.
The metallic furnaces are constructed using tungsten (HTK W) or molybdenum (HTK MO), resulting in the highest possible purity of the inert atmosphere and final vacuum level. Upon request, a high vacuum upgrade is available. The most commonly used gases include Nitrogen, Argon, Hydrogen, and its mixtures.
The HTK series features heating elements and insulation made of either tungsten (HTK W) or molybdenum (HTK MO). A retort can be utilized to guide the gas flow, particularly for debinding applications or to enhance temperature uniformity. The maximum temperature for the HTK W is 2200 °C, while for the HTK MO, it is 1600 °C.
Application Examples
carbon free atmosphere, metal injection moulding (MIM), metallization, sintering, thermal debinding prior to sintering, pyrolysis, synthesis, annealing, tempering
Product Video: Chamber furnace, metal insulation - HTK
| Furnace Type | Usable Volume | Max temp | Number of heated zones | Debinding Option |
|---|---|---|---|---|
| HTK 8 MO/W | 8 | 1600 °C / 2200 °C | 1 | Torch/ condensate trap |
| HTK 25 MO/W | 25 | 1600 °C / 2200 °C | 1 | Torch/ condensate trap |
| HTK 80 MO | 80 | 1600 °C | 4 | Torch/ condensate trap |
| HTK 120 MO | 120 | 1450 °C | 4 | Torch/ condensate trap |
Chamber furnace, metal insulation - HTK Standard Features and Options
- Metallic furnaces provide a precisely defined atmosphere with the highest possible purity
- Metallic furnaces offer the best possible vacuum
- Hydrogen partial pressure operation is optional available
- Data recording for quality management: CC-TP1200 smart, CC-TP1900 or CC-IPC1900
- The HTK series can be supplied in compliance with AMS-2750 requirements
- Option for debinding processes
- Option for clean high vacuum processes
Required infrastructure
- Gases: hydrogen, argon, nitrogen
- Electric power supply
- Fail safe cooling water
- Exhaust
HTK 8
HTK 25
HTK 80
| | HTK 8 | HTK 25 | HTK 80 | HTK 120 |
|---|---|---|---|---|
| Usable space in the retort H x W x D [mm] | 160 x 180 x 180 | 240 x 240 x 400 | 380 x 410 x 500 | 380 x 400 x 770 |
| Number of plates* | 3 | 3 | 40 | 60 |
| Plate dimensions [sqr. cm] * | 225 | 860 | 930 | 930 |
| Picture of sample rack |
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Chamber furnace, metal insulation - HTK Explanation of the debinding and Sintering process steps of the HTK-MIM-3 furnace
The HTK-MIM-3 furnace program enables debinding and sintering of MIM components in two stages. The program's progress is displayed in a diagram, and important parameters such as pressure, gas flow, and gas type are recorded. The debinding stage utilizes partial pressure and high nitrogen gas flow, while the sintering stage focuses on temperature uniformity, resulting in a consistent density of the MIM parts.
Chamber furnace, metal insulation - HTK Inside the furnace
HTK 8 – 80 furnaces consist of:
- Heaters
- Retort
- Radiation Shields
- Thermocouple
- Gas Inlet
- Gas Outlet
- Vacuum Gauge
- Water-cooled vacuum vessel
Exemplary cross section of a HTK 8 molybdenum
HTK 120 furnaces consist of:
- Heaters
- Radiation Shields
- Gas inlet
- Gas Outlet
Heating cassette of the HTK 120, CAD drawing. Designed for highest lifetime and easy maintenance.
Chamber furnace, metal insulation - HTK Binder handling options HTK8 - 80
HTK 8 – 80 furnaces consist of:
- Heaters
- Retort
- Radiation Shields
- Thermocouple
- Gas Inlet
- Gas Outlet
- Vacuum Gauge
- Water-cooled vacuum vessel
The torch of the afterburner ensures controlled conversion of remaining flammable or toxic volatiles into non-flammable gases.
The condensate trap may be installed for binder handling. During the process the trap is cooled to condense the binder. After the process the trap can be heated to release the binder safely which has been liquified.
Afterburner
Chamber furnace, metal insulation - HTK Some HTK120 options
Afterburner assembly:
- Gas outlet
- Trace heating
- Torch
- Position controlled ball valve
- Fresh oil pump
- Oil condenser
Heated gas outlet and vacuum line of the HTK 120
Stand alone safety purge tank
Leakage rate results
With the high vacuum upgrade the leakage rate results in values below 10-3 mbar*l/s. The leakage rate is determined by evacuating the furnace, closing all valves and meassuring the pressure increase over time. The desorption of water molecules from the metal surface takes approximately 20 h, and leads to a faster increase in pressure, represented by the blue line.
Pump down curve
Measured under controlled laboratory conditions. Results may vary depending on process-specific variables, e.g. gas flow rates, vacuum levels, and sample material, size/density.
Leakage rate
Measured under controlled laboratory conditions. Results may vary depending on process-specific variables, e.g. gas flow rates, vacuum levels, and sample material, size/density.
Chamber furnace, metal insulation - HTK High Vacuum applications
Cross section of HTK 8 with high vacuum upgrade. The turbo pump is at least connected via an DN100 flange.
- Turbo pump
- Vacuum valve
- DN 100 flange
High vacuum upgrade
Schematic of a turbomolecular pump for high vacuum applications.
Chamber furnace, metal insulation - HTK Controller Options
The furnace is operated via a 12" or 19" touch panel controller. It provides an overview of the furnace and its behaviors and allows the user to preform any possible adjustments to the furnace.
- User friendly 12” touch panel, provides a detailed overview of the furnace status.
- Configuration of an automatic programm
- The smart software is mainly used for simple processes
- The full automatic function ensures full flexibility
- The pre-program ensures that the furnace is evacuated prior to heat treatment to ensure safety in case of any occuring errors
- The system is based on an industrial standard Siemens PLC ensuring full safety.
- Full visualization of the furnace with 19’’ touch panel, mainly for fully configured units or for the use of hydrogen (>5%)
- Configuration of an automatic program
- The automatic software is used for more complicated and hydrogen processes
- The CC-IPC1900 version additionally includes an industrial PC with standard windows software
- The system is based on an industrial standard Siemens F-PLC ensuring full safety even for hydrogen applications
- The pre-program ensures a fully automated leakage test which takes place in overpressure and vacuum
Chamber furnace, metal insulation - HTK Examples
HTK 8 MO/16-2G smart 8 L usable volume, 1600 °C, Argon, Forming gas
HTK 25 W/22-1G automatic 25 L usable volume, 2200 °C, Argon
HTK 80 MO/16-3G automatic 80 L usable volume, 1600 °C, Argon, Nitrogen, and optional hydrogen equipment
HTK 120 MO/14-3G automatic 120 L usable volume, 1400 °C, Argon, Nitrogen, Hydrogen, and partial pressure option
Chamber furnace, metal insulation - HTK - FAQ
What is the advantage of the chamber furnace design?
Chamber furnaces are quite easy to load and unload, due to the front loading concept. Smaller furnace can be loadaed manually, bigger units can be loaded by a manual fork lift. The rectangular design of the water cooled vacuum vessels allows the unit be be designed highly compact. This is why the units do not require much space in the workshop and are perfectly suited for laboratories. All HTK type furances are mounted on a single frame and can be easily delivered to customers all over the world. However, for bigger furnace volumes, the vessel is designed cylindrical, as for the HTK 120.
Is a graphite furnace better?
This depends on the process. Some materials, such as stainless steel, 316L, titanium etc. cannot be heat treated in a graphite furnace, especially when the performance of the part is of importance. In such a case metallic furnaces are recommended due to their high purity atmospheres as well as hydrogen and high vacuum abilities.
Why does hydrogen heat treatment require a metallic furnace?
In a graphite furnace, hydrogen would react with the graphite heating elements and insulation above 1000 °C. The higher the temperature, the faster the graphite parts wear which generates hydrocarbons and causes reactions with the sample. In a metallic furnace the resulting atmospthere is pure.
Why is the insulation made from tungsten or molybdenum?
The lower the variaty of materials inside the furnace chamber, the less is the cross-contamination inside the furnace. This leads to a purer atmosphere within the furnace. Furthermore, the working vacuum is better, due to high boiling points and low vapour pressure of the bespoken metals. The Carbolite vacuum furnace design consists of multiple layers of radiation shields to ensure very low energy consumption. Those layers act like a “mirror” reflecting the thermal radiation, hence insulating the furance. The remaining heat is taken away by cooling water surrounding the vacuum vessel.
What is the advantage of (hydrogen) partial pressure?
Carbolite enables adjustable pressure levels between 10 and 1000 mbar. With a variable pressure, the customer can adjust the gas density and therefore the Reynolds number as desired. This ensures a positve gas flow under reduced pressure, evaportating the binder at lower temperatures. This is advantageous for many applications. However, hydrogen partial pressure requires a lot expertise in order to handle it safely. We use dedicated software and hardware solutions to ensure full safety under these conditions.
Chamber furnace, metal insulation - HTK Technical Data
| Insulation material | Dimensions: External H x W x D (mm) | Transport weight (kg) | Usable space | Volume (litres) | H x W x D usable space without retort (mm) | H x W x D usable space with retort (mm) | Thermal values | Tmax vacuum (°C) | -Delta-T between 500 and 1500°C (K) according to DIN 17052 | Max. heat-up rate (K/min) | Cooling time (h) | Connecting values | Power (kW) | Voltage (V) | Current (A) | Series fuse (A) | Vacuum (option) | Leakage rate - clean, cold and empty (mbar l/s) | Vacuum range depending on the pumping unit | Cooling water required | Volume (l/min) | Max entry temperature (°C) | Gas supply | Nitrogen or Argon, others on request (l/h) | Controller | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| HTK 8 MO/16-1G | Molybdenum | 2100 x 1300 x 1100 | 1200 | |
8 | 200 x 200 x 200 | 200 x 180 x 180 | |
1600 | ± 5 | 10 | 6 | |
30 | 400 | 75 | 3x 100 | |
5x10-3 | rough, fine or high vacuum | |
40 | 23 | |
200-2000 | on request |
| HTK 25 MO/16-1G | Molybdenum | 2200 x 1900 x 1800 | 1700 | |
25 | 250 x 250 x 400 | 230 x 230 x 400 | |
1600 | ± 5 | 10 | 6 | |
80 | 400 (3P) | 3x 120 | 3x 160 | |
5x10-3 | rough, fine or high vacuum | |
70 | 23 | |
200-2000 | on request |
| HTK 80 MO/16-1G | Molybdenum | 2300 x 2100 x 2200 | 2000 | |
80 | 400 x 400 x 500 | 380 x 380 x 500 | |
1600 | ± 5 | 10 | 8 | |
100 | 400 (3P) | 3x 150 | 3x 200 | |
5x10-3 | rough, fine or high vacuum | |
100 | 23 | |
200-2000 | on request |
| HTK 8 W/22-1G | Tungsten | 2100 x 1300 x 1100 | 1300 | |
8 | 200 x 200 x 200 | 180 x 180 x 200 | |
2200 | ± 5 | 10 | 6 | |
45 | 400 | 112 | 3x 160 | |
- | rough, fine or high vacuum | |
40 | 23 | |
200-2000 | on request |
| HTK 25 W/22-1G | Tungsten | 2200 x 1900 x 1800 | 1900 | |
25 | 250 x 250 x 400 | 230 x 230 x 400 | |
2200 | ± 5 | 10 | 6 | |
100 | 400 (3P) | 3x 150 | 3x 200 | |
- | rough, fine or high vacuum | |
100 | 23 | |
200-2000 | on request |
| HTK 120 MO/16-3G MIM | Molybdenum | - | - | |
120 | - | - | |
1600 | ± 5 | - | <4 | |
100 | 400 (3P) | 3x 150 | 3x 200 | |
5x10-3 | rough, fine or high vacuum | |
100 | 23 | |
200-2000 | on request |
