The molybdenum crucible and the temperature control system need to be optimized from multiple dimensions such as temperature matching, control strategy, equipment selection and safety protection to ensure efficient and accurate process control. The following are the specific coordination methods and key points:
- Matching principle of temperature control system and molybdenum crucible
Temperature range matching
molybdenum crucible: ≤ 2000℃ (long-term use temperature ≤ 1800℃).
Temperature control system range: must cover the working temperature of the molybdenum crucible and leave a margin of 100-200℃.
Example: If the process needs to be carried out at 1600°C, the temperature control system should support 0-1800°C.
Heating rate matching
molybdenum crucible: ≤ 50℃/min (to avoid thermal stress cracking).
Temperature control system response speed: must support a temperature adjustment accuracy of ≤ 1°C/s.
- Collaborative control strategy of temperature control system and molybdenum crucible
Staged heating and cooling
Stage 1 (heating): slowly increase the temperature to 500°C at 10-30°C/min to avoid cracking of the molybdenum crucible.
Stage 2 (high temperature stage): Raise the temperature to the target temperature at 20-50℃/min and maintain constant temperature.
Stage 3 (cooling): Slowly cool at ≤ 50℃/min to avoid deformation caused by rapid cooling.
Closed-loop control
Feedback mechanism: The crucible temperature is monitored in real time by thermocouples and fed back to the temperature control system to adjust the power.
Example: If the target temperature is 1600°C, the temperature control system needs to be stably controlled within the range of ± 5°C.
Inert gas protection
Temperature control system linkage: when the temperature exceeds 800℃, argon or nitrogen protection is automatically started to prevent the molybdenum crucible from oxidation.
- Equipment selection and configuration
Heating equipment
Recommended Type:
Resistance furnace: suitable for processes ≤ 1800℃, low cost and uniform heating.
Induction furnace: suitable for high temperature processes of 1800-2000℃, with fast heating, but attention should be paid to the influence of electromagnetic fields on samples.
Thermostat
PID control: Proportional-integral-differential control algorithm to achieve precise temperature regulation.
High-precision sensor:
Accuracy: ± 0.1% FS (full scale accuracy).
Multi-stage program control: supports multi-stage program heating and a resolution of 0.1°C.
Multi-channel control: supports simultaneous control of multiple heating zones to meet complex process requirements.
sensor
Thermocouple Type:
Type K (0-1200℃): suitable for medium and low temperature range.
S type (0-1700℃): suitable for high temperature range.
Installation position: It needs to be close to the outer wall of the molybdenum crucible to avoid contact with the sample and affect the measurement accuracy.
- Safety protection and emergency measures
Over temperature protection
Temperature control system setting: When the temperature exceeds the set value by 10℃, the power supply will be automatically cut off.
Mechanical protection: Install a temperature limit switch for double protection.
Oxidation protection
Gas flow monitoring: Real-time monitoring of inert gas flow to ensure oxygen content < 10 ppm.
Pressure alarm: When the pressure inside the furnace is abnormal, it will automatically alarm and start emergency ventilation.
Crucible breakage detection
Acoustic wave detection: Monitor crucible cracks through acoustic wave sensors and provides early warning.
Visual inspection: Install a camera to monitor the crucible surface status in real time.
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