Precautions for using laboratory powder sintering furnace
08-08-2025 Author: KJ technology
The laboratory powder sintering furnace is a key equipment for material preparation, and its high temperature, high pressure, or special atmosphere operating environment requires extremely high safety and experimental result accuracy. The following are the core considerations when using a laboratory powder sintering furnace, covering four aspects: preparation before operation, monitoring during operation, maintenance after operation, and safety protection:
1. Preparation before operation: Ensure the compatibility between the equipment and the sample
a. Equipment inspection and calibration
Temperature system:
Check if the heating elements (such as resistance wires and induction coils) are intact and there is no risk of breakage or short circuit.
Use a standard thermometer or infrared thermometer to calibrate the temperature control system, ensuring that the displayed temperature is consistent with the actual temperature (with an error of ≤± 1 ℃).
Atmosphere system:
Verify that the gas pipeline is leak free (can be detected with soapy water), the gas cylinder pressure is sufficient, and the flow meter accuracy meets the standard.
The vacuum sintering furnace needs to check the oil level and sealing ring status of the vacuum pump to ensure that the vacuum degree meets the process requirements (such as ≤ 10 ⁻ ³ Pa).
Pressure system (such as hot pressing sintering):
Confirm that the pressure sensor is calibrated accurately, the hydraulic or pneumatic device is leak free, and the safety valve is set at a reasonable pressure.
b. Sample and tooling selection
Sample pretreatment:
The powder needs to be dried (such as drying at 120 ℃ for 2 hours) to prevent moisture from vaporizing at high temperatures and causing the sample to crack.
Metal powder needs to be sieved (e.g. 200 mesh) to remove agglomerates and ensure particle size uniformity.
Fixture matching:
Choose crucible materials (such as graphite, alumina, molybdenum) based on their properties to avoid reactions with the sample at high temperatures.
During hot pressing sintering, the mold needs to be pre coated with release agent (such as boron nitride spray) to prevent the sample from sticking to the mold.
c. Process parameter setting
Temperature curve:
Set the heating rate in sections (such as 5-10 ℃/min) to avoid sample cracking caused by thermal stress.
The insulation time should be determined according to the material thickness and diffusion rate (such as ceramic sintering usually takes 2-6 hours).
Atmosphere control:
Oxidation sensitive materials (such as titanium alloys) need to be sintered under argon protection with an oxygen content of ≤ 50 ppm.
During vacuum sintering, it is necessary to evacuate to the target pressure (such as 10 ⁻ ² Pa) before heating up.
Pressure loading (if applicable):
The hot pressing sintering pressure needs to be gradually increased (such as 0.5 MPa/min) to avoid mold damage caused by instantaneous high pressure.
2. Running monitoring: real-time response to abnormal situations
a. Temperature and atmosphere monitoring
Temperature tracking:
Real time temperature monitoring through furnace observation windows or thermocouples. If temperature fluctuations exceed ± 2 ℃, heating should be paused and the temperature control system checked.
Atmosphere stability:
Regularly check the gas composition inside the furnace (such as using an oxygen analyzer) to ensure that the purity or vacuum degree of the protective gas meets the requirements.
During vacuum sintering, if the vacuum degree suddenly drops (such as>10 Pa/min), the machine should be stopped immediately to check for leaks.
b. Pressure and mechanical state
Pressure feedback:
In hot pressing sintering, if the pressure display is abnormal (such as continuous decrease), it may be due to hydraulic system leakage or mold deformation, and emergency pressure relief and maintenance are required.
Mechanical noise:
If abnormal vibrations or friction sounds are heard during operation, it may be due to loose heating elements or fan failure, and the machine needs to be stopped for troubleshooting.
c. Observation of sample status
Visual inspection:
Check whether the sample color and deformation (such as expansion and contraction) meet expectations through observation windows or intermittent shutdowns.
If the sample melts, splashes, or emits strong smoke, it may be due to temperature exceeding the limit or uncontrolled atmosphere, and the experiment should be terminated immediately.
3. Post operation maintenance: Extend equipment lifespan
a. Cooling and Sampling
Control cooling rate:
The metal sample needs to be cooled in the furnace to below 200 ℃ before removal to avoid cracking caused by thermal shock.
Ceramic samples can be rapidly cooled (such as by air cooling), but it is necessary to prevent microcracks caused by rapid cooling.
Anti oxidation measures:
When sampling at high temperatures, it is necessary to operate in an inert gas glove box to prevent the sample from coming into contact with air and oxidizing.
b. Equipment cleaning and maintenance
Furnace cleaning:
After sintering, promptly remove the residue (such as oxide scale and molten material) in the furnace to avoid corrosion of the furnace or affecting the next experiment.
Use a soft brush or vacuum cleaner to clean, and do not scratch the surface of the heating element with hard objects.
Fixture maintenance:
After use, the graphite crucible needs to be soaked in hydrochloric acid to remove the oxide layer, dried, and coated with an anti-oxidation coating (such as boric acid).
The alumina crucible needs to be checked for cracking, and if the crack exceeds 1mm, it needs to be replaced.
c. Regular calibration and maintenance
Annual major overhaul:
Replace aging heating elements, sealing rings, and vacuum pump oil, and check the insulation performance of electrical circuits.
Quarterly minor repairs:
Clean the temperature control probe, flow meter, and pressure sensor, and calibrate the accuracy of the display instrument.
4. Security protection: Avoiding operational risks
a. Personal Protective Equipment (PPE)
Basic protection:
Wear insulated gloves (temperature resistance ≥ 800 ℃), splash proof face shields, and lab coats during operation to prevent burns or splash injuries.
Gas protection:
When dealing with toxic gases (such as hydrogen), it is necessary to operate in a fume hood and equip it with a gas detection alarm.
b. Emergency Response Plan
Fire response:
When a fire breaks out in the furnace, immediately cut off the power and close the gas valve, use a carbon dioxide fire extinguisher to extinguish the fire, and do not use water to extinguish the fire.
Vacuum leakage treatment:
If the glass observation window of the vacuum sintering furnace bursts, evacuate personnel quickly and turn on the ventilation system. Wait for the pressure to balance before conducting maintenance.
c. Operation specification training
Before new personnel start working:
Must pass equipment operation assessment and be familiar with the location of emergency stop buttons and escape routes.
Regular refresher training:
Organize safety drills every six months and update emergency response procedures (such as new equipment introduction or process changes).
5. Special scenario precautions
a. High activity material sintering
Titanium alloy, zirconium alloy:
Sintering should be carried out in an environment with argon purity ≥ 99.999% to avoid embrittlement caused by oxygen and nitrogen pollution.
Lithium ion battery materials:
Toxic gases (such as HF) may be released during the sintering process, which requires operation in a closed negative pressure system and equipped with exhaust gas treatment devices.
b. Ultra large temperature difference or high-pressure process
Flash Burning:
Samples need to be placed in an insulated glove box to prevent arcing caused by high voltage electric fields (such as 1000 V/cm).
Hot isostatic pressing (HIP):
Before operation, it is necessary to confirm that the high-pressure vessel has passed the annual inspection and it is prohibited to use it under overpressure (usually ≤ 200 MPa).
6. Record and Trace
Experimental log:
Detailed records of process parameters (temperature, time, atmosphere, pressure), sample status, and abnormal conditions for each experiment, providing a basis for process optimization.
Equipment file:
Establish equipment maintenance records (such as component replacement time, calibration data) for easy traceability of equipment status changes.
