Working principle of bell type lifting high-temperature muffle furnace

The bell shaped lifting high-temperature muffle furnace achieves precise heat treatment in high-temperature environments through the collaborative work of bottom lifting furnace door design, electric heating element heating, intelligent temperature control system, and sealing structure. Its working principle can be disassembled into the following core steps:

1. Lift structure design: balance between ease of operation and thermal field stability
Bottom lifting mechanism
The bottom of the furnace is equipped with a hydraulic or electric lifting system, which can achieve vertical lifting of the furnace door through one click operation on the control panel. This design avoids the heat loss caused by thermal convection in traditional side opening furnace doors (the temperature wave can reach ± 5 ℃ or more when the side opening furnace door is opened and closed), while the temperature wave of the lifting furnace door can be controlled within ± 1 ℃ during the opening and closing process, ensuring the stability of the heat treatment process.
Modular material platform
The material platform can be designed as a platform type structure, supporting manual or automatic lifting. When handling large workpieces (such as ceramic discs with a diameter greater than 300mm), the trolley can be pulled out of the furnace for loading and unloading, increasing operational efficiency by more than 50% while reducing the direct exposure risk of high-temperature environments to operators.

2. Heating system: synergy between electric heating elements and heat transfer
Heating element selection
Resistance wire: suitable for scenarios up to 1000 ℃ (such as metal annealing), with low cost but short lifespan (about 2000 hours).
Silicon carbon rod: Working temperature of 1000-1500 ℃, good high-temperature stability, commonly used for ceramic sintering.
Silicon molybdenum rod: supports high temperatures of 1500-1800 ℃, has strong creep resistance, and is suitable for heat treatment of refractory metals such as tungsten and molybdenum.
Heat transfer mode
Radiant heat transfer: Heating elements radiate energy in the form of electromagnetic waves, accounting for over 80% of the total heat transfer in high-temperature muffle furnaces, ensuring temperature uniformity within the furnace by ± 5 ℃ (test point 1000 ℃).
Convection and conduction: In high-temperature environments, convective heat transfer weakens, while conduction heat transfer is limited to the contact area between the material and the crucible, and the impact can be ignored.

3. Temperature Control System: PID Algorithm and Precise Control of Sensors
temperature sensor
Thermocouple: B-type thermocouple (platinum rhodium alloy) is suitable for high temperatures above 1600 ℃, with measurement accuracy of ± 1 ℃ and shorter response time.
Thermistor: Platinum resistance (PT100) is used in the medium and low temperature range (≤ 800 ℃), with an accuracy of ± 1 ℃.
PID control logic
Proportional link (P): Adjust the heating power based on the deviation between the actual temperature and the set value to eliminate static errors.
Integral stage (I): Accumulate historical deviations and eliminate steady-state errors (such as temperature fluctuations during the heating plateau period).
Differential stage (D): Predict the trend of temperature changes and suppress overshoot (such as reducing power in advance when approaching the set temperature).
Through PID algorithm, the furnace temperature can be accurately controlled within ± 1 ℃, and the data repeatability meets the research level requirements (such as lithium battery material synthesis).

4. Sealing and Safety Design: Protective Barrier in High Temperature Environments
Sealing structure of furnace door
Using double-layer ceramic fiber pressure strips and metal sealing rings, combined with a vacuum pump, can achieve oxygen content inside the furnace, meeting the requirements of metal oxidation protection (such as titanium alloy heat treatment).
Security protection mechanism
Overtemperature alarm: When the furnace temperature exceeds the set value ± 5 ℃, the heating power supply will be automatically cut off and an audible and visual alarm will be triggered.
Leakage protection: automatic power-off.
Power off when opening the door: The furnace door instantly cuts off the power supply to the heating element to prevent heat waves from spraying out and injuring people.

5. Typical application scenario examples
Ceramic sintering
Sintering alumina ceramics at 1600 ℃ and achieving density through PID temperature control.
Metal heat treatment
After annealing the aviation aluminum alloy at 450 ℃ to eliminate internal stress, the elongation rate is increased and the hardness is reduced.
semiconductor process
Under inert gas protection, silicon chips are oxidized at 1200 ℃ with better uniformity of oxide layer thickness, meeting the requirements of integrated circuit manufacturing.