The temperature of the laboratory powder sintering furnace cannot rise
08-08-2025 Author: KJ technology
The inability to increase the temperature of the laboratory powder sintering furnace may be caused by various factors such as heating element failure, power and control system issues, thermocouple/temperature controller errors, furnace structure defects, incorrect operating parameter settings, abnormal cooling system, and interference from vacuum/atmosphere environment. The following is a specific analysis of the reasons and solutions:
1. Heating element malfunction
Heating element damage:
Reason: Broken resistance wires, short circuits in induction coils, or oxidation and peeling of graphite heating elements can lead to a decrease in heating power.
resolvent:
Use a multimeter to check the resistance value of the heating element. If the deviation from the nominal value exceeds ± 10%, the element needs to be replaced.
When the oxide layer on the surface of the graphite heating element is too thick, it needs to be polished with sandpaper to a metallic luster, or replaced with a new heating element directly.
poor contact:
Reason: Oxidation or looseness at the connection between the heating element and the electrode can cause obstruction of current transmission.
resolvent:
After turning off the power, use sandpaper to polish the electrode contact surface, re tighten the bolts, and apply conductive paste.
Check if the wiring terminals are loose, and replace the spring plate wiring terminals if necessary.
2. Power and control system issues
Insufficient power supply:
Reason: The actual input power is lower than the rated value due to thin power lines, unstable voltage, or three-phase power shortage.
resolvent:
Check the specifications of the power cord (such as copper core cross-sectional area ≥ 4mm ²) to ensure compliance with equipment requirements.
Use a voltmeter to monitor the three-phase voltage. If there is a phase loss, contact an electrician to repair the circuit.
Temperature control system malfunction:
Reason: Improper PID parameter settings, damage to solid-state relays, or breakdown of thyristors can cause temperature control failure.
resolvent:
Reset PID parameters (such as P=20-50, I=100-300s, D=10-30s), or restore factory settings.
Use an oscilloscope to detect the output waveform of the solid-state relay. If there is any abnormality, replace it with a relay of the same model.
3. Error between thermocouple and temperature controller
Thermocouple aging:
Reason: Long term use at high temperatures can lead to slower thermal response or temperature measurement deviation of thermocouples.
resolvent:
Compare the thermocouple with a standard thermometer (such as a platinum resistance thermometer). If the deviation exceeds ± 2 ℃, a new thermocouple needs to be replaced.
Check if the thermocouple compensation wire is reversed to ensure that the cold end compensation function is normal.
Calibration deviation of temperature controller:
Reason: The internal parameters of the temperature controller drift or the displayed values do not match the actual values.
resolvent:
Use a standard signal source to calibrate the temperature controller and adjust the "range" and "zero" parameters.
If the temperature controller does not have calibration function, contact the manufacturer for replacement or repair.
4. Furnace structure and insulation defects
Failure of insulation material:
Reason: Aging or detachment of alumina fiber cotton or alumina silicate fiber board in the furnace can cause heat loss.
resolvent:
Check if the insulation layer on the inner wall of the furnace is complete. If cracks or detachment occur, the insulation material needs to be refilled.
For graphite furnaces, check if the carbon felt has carbonized. If it has become thinner, replace it with a new carbon felt.
The furnace door is not tightly sealed:
Reason: Aging or deformation of the furnace door sealing ring can cause cold air to seep in.
resolvent:
Replace the silicone rubber sealing ring to ensure that there is no gap after the furnace door is closed.
Apply high-temperature sealant (such as silicone sealant) on the edge of the furnace door to enhance the sealing performance.
5. Operation parameter setting error
Heating rate too fast:
Reason: Setting the heating rate beyond the capacity of the equipment or material can cause the heating system to overload.
resolvent:
Adjust the heating rate according to the thermal stability of the material (such as ceramic sintering, it is recommended to be ≤ 5 ℃/min).
Set the heating program in segments, using a faster rate in the low temperature range (such as room temperature -300 ℃) and a slower rate in the high temperature range (such as 300 ℃ - target temperature).
Target temperature setting error:
Reason: Incorrect setting of target temperature lower than current temperature or unit error (such as confusion between ℃ and ℉).
resolvent:
Check the display unit of the temperature controller to ensure consistency with the process requirements.
Re enter the target temperature and confirm that the "set value" is consistent with the "displayed value".
6. Abnormal interference of cooling system
Insufficient cooling water flow:
Reason: Low flow rate of water-cooled electrodes or furnace cooling water can cause automatic protection shutdown of the equipment.
resolvent:
Check the cooling water pressure (usually ≥ 0.2MPa), and if it is insufficient, adjust the water pump or clean the filter.
Ensure that there are no leaks in the cooling water circuit and that the water flow meter displays a value within the normal range (such as ≥ 5L/min).
Cooling fan malfunction:
Reason: The shutdown of the furnace cooling fan caused heat accumulation.
resolvent:
Check if the power cord of the fan is loose, and use a multimeter to measure the resistance value of the fan motor (usually several tens of ohms).
If the fan is damaged, it is necessary to replace it with a fan of the same specification and clean the dust on the heat sink.
7. Interference from vacuum/atmosphere environment
Insufficient vacuum degree:
Reason: During vacuum sintering, the thermal conductivity of the gas inside the furnace will reduce the heating efficiency.
resolvent:
Check the operating status of the vacuum pump to ensure that the vacuum degree meets the process requirements (such as ≤ 10 ⁻³ Pa).
If gas shielded sintering is used, the gas flow rate should be adjusted (such as argon flow rate ≤ 5L/min) to avoid excessive cooling.
Low purity of atmosphere gas:
Reason: Insufficient purity of protective gases (such as argon and nitrogen) can lead to endothermic oxidation reactions.
resolvent:
Use high-purity gas (≥ 99.999%) and regularly check the residual pressure of the gas cylinder.
Install a filter at the gas inlet to remove impurities and particles.
8. Equipment overload
Excessive sample size:
Reason: Too many or too dense samples can hinder heat transfer.
resolvent:
Reduce the amount of single sintered samples (usually not exceeding 1/3 of the furnace volume).
Use alumina crucibles to disperse and place samples, avoiding direct stacking.
Excessive heat capacity of tooling:
Reason: Excessive quality of graphite molds or crucibles can absorb a large amount of heat.
resolvent:
Choose lightweight fixtures (such as carbon fiber composite materials) or preheat fixtures to near the target temperature.
Optimize equipment design to reduce unnecessary thickness or volume.
9. Maintenance and repair suggestions
Regularly clean the furnace:
After sintering, promptly remove any residue (such as oxide scale and molten material) from the furnace to avoid corrosion of the heating element.
Use a soft brush or vacuum cleaner to clean, and do not scratch the surface of the heating element with hard objects.
Annual overhaul plan:
Replace aging heating elements, sealing rings, and vacuum pump oil.
Check the insulation performance of electrical circuits, calibrate temperature controllers and gas flow meters.
Operation training and records:
New personnel need to pass equipment operation assessments and become familiar with the location of emergency stop buttons and escape routes.
Record the process parameters (temperature, time, atmosphere, pressure) and equipment status for each experiment to facilitate problem tracing.
