Molybdenum crucibles in vacuum heat treatment furnaces requires strict operating procedures. Combined with its high temperature resistance and strong chemical stability, the following are specific usage methods and precautions:
- Preparation before use
Equipment inspection
Ensure that the vacuum system, heating system, cooling system, etc. of the vacuum heat treatment furnace are operating normally, and that safety devices such as pressure gauges, temperature controllers, and pressure relief valves are in good condition.
Check the molybdenum crucible for damage or deformation to ensure its integrity.
Crucible handling
the molybdenum crucible with alcohol to remove oil and impurities, and dry it for later use.
For new molybdenum crucibles or crucibles that have not been used for a long time, pre-burning treatment can be carried out to remove gases and impurities adsorbed on the surface.
Sample preparation
Place the sample to be processed into a molybdenum crucible. Note that the amount of the sample should not exceed the capacity of the crucible to avoid overflow during heating.
- Furnace loading and vacuuming
Furnace loading
Use crucible tongs to gently place the molybdenum crucible into the designated position of the vacuum heat treatment furnace, ensuring that the crucible is stable and in the proper position.
Close the oven door and check for tightness.
Vacuum
Turn on the mechanical pump to pre-evacuate the furnace chamber. When the vacuum degree reaches below 5 Pa, turn on the molecular pump to further evacuate the chamber.
When the vacuum degree of the vacuum chamber is evacuated to about 3×10 ⁻ ³ Pa, the molecular pump and the mechanical pump are turned off in turn, and high-purity argon gas of about 30 kPa is filled into the furnace chamber to form a protective atmosphere. After filling, the vacuum degree in the furnace chamber is maintained at about 400 Pa.
- Heating and insulation
Setting heating parameters
Set the heating temperature and heating rate according to the process requirements. For example, heat to 800℃ at a heating rate of 10℃/min, hold for 1 min, then cool to 500℃ at a rate of 20℃/min and cool to room temperature with the furnace.
For the preparation of crystalline alloys, the sample can be first heated to 500°C at a heating rate of 25°C/min, kept at that temperature for 20 min, and then heated to 700°C at a heating rate of 20°C/min, and kept at that temperature for 1 h.
Monitoring process
During the heating process, closely observe the changes of the molybdenum crucible and the sample to ensure that the heating process is uniform and stable.
Control the heating time to avoid incomplete melting or excessive loss of the sample due to being too long or too short.
- Cooling and Sampling
cool down
After heating is completed, let the molybdenum crucible cool naturally to a safe temperature, or use the furnace cooling method.
Avoid placing the molybdenum crucible on a cold metal table immediately to prevent it from cracking due to rapid cooling.
sampling
Use crucible tongs to take the molybdenum crucible out of the vacuum heat treatment furnace and place it on a dry and clean workbench.
The melted or processed samples can be subsequently processed as needed, such as separation, analysis, etc.
- Handling and maintenance after use
Cleaning the Crucible
To remove the residual samples and impurities in the molybdenum crucible, it can be cleaned with appropriate solvents or mechanical methods.
Avoid using corrosive substances such as strong acids and alkalis to contact the molybdenum crucible to avoid damaging its surface.
Check and save
Check whether the molybdenum crucible is deformed or cracked. If damaged, stop using it immediately.
the cleaned molybdenum crucible properly to avoid moisture, contamination or mechanical damage.
- Safety precautions
Personal protection
During operation, always wear personal protective equipment such as heat-resistant clothing, gloves and goggles.
Avoid touching the overheated parts of the molybdenum crucible to avoid burns.
Equipment Security
Ensure that all safety devices of the vacuum heat treatment furnace are working properly and comply with all safety regulations and operating instructions.
During operation, avoid performing operations that may produce gas in a vacuum environment, and understand and be familiar with emergency plans.
Environmental safety
Keep the operating area clean and tidy, free from obstructions or accumulation.
Ensure that the operating area has proper ventilation to prevent the accumulation of harmful gases or dust generated by the heating process.
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