In industrial metal melting, the medium frequency induction melting furnace is valued for its high efficiency, precise control, and clean operation. However, proper preheating before each initial use is essential to protect the furnace components—especially the crucible—and ensure a longer service life.
This guide explains the step-by-step preheating process, along with practical tips for safe and efficient operation.
Why Preheating Matters
Preheating removes moisture from the crucible lining, prevents thermal shock, and reduces the risk of cracking or bursting during the melting stage. It also helps the furnace quickly reach stable operating conditions, improving productivity and product quality.
Step 1: Power and Safety Checks
Before beginning:
- Ensure the main power supply is switched off.
- Wear appropriate PPE (heat-resistant gloves, goggles, protective clothing).
- Confirm all emergency stop systems are functional.
Step 2: Visual Inspection of the Furnace
A quick but thorough inspection can prevent serious damage during operation:
- Crucible – Check the bottom and inner wall for cracks, dents, or wear; repair if needed.
- Furnace Cover, Roof, and Nozzle – Ensure all parts are secure; tighten or repair if loose.
- Induction Coil – Remove any iron filings, dust, or debris.
- Bolts & Connectors – Tighten or replace any loose or missing bolts.
- Water-Cooling System – Inspect hoses, cooling cables, and joints for leaks and ensure smooth water flow.
- Tilting/Turning Mechanism – Test for smooth operation; repair any faults immediately.
Step 3: Prepare the Lining
Apply or touch up refractory coating inside the crucible as needed. This creates an additional barrier against extreme heat and extends lining lifespan.
Step 4: Initial Power-Up
Once all checks are complete:
- Switch on the power supply.
- Set the frequency and power level appropriate for preheating (refer to your furnace specifications).
Step 5: Controlled Heating Process
The preheating stage should be gradual to avoid thermal shock:
- Drying Stage – Heat the empty crucible to approximately 200°C for about 30 minutes, then continue drying for 60 minutes. This removes surface moisture.
- High-Temperature Ramp-Up – Increase temperature to 900°C–1000°C within roughly 2 hours. Hold for 20–30 minutes to pass quickly through oxidation-prone temperature zones.
- Return to Melting Temperature – Adjust temperature to the optimal level for your specific metal.
Tip: Once preheated, the furnace can remain at operating temperature between batches. Only repeat preheating if the crucible becomes damp or after extended shutdowns.
Step 6: Maintain Thermal Stability
Hold the target preheating temperature long enough for thermal equilibrium—ensuring the entire crucible and furnace body are evenly heated.
Step 7: Begin the Melting Process
After preheating:
- Add the prepared metal charge.
- Adjust power and frequency to the desired melting rate.
- Monitor temperature and process parameters closely for consistent results.
Safety Reminder
- Follow all manufacturer guidelines for your furnace model.
- Never skip the preheating stage on a new or repaired lining.
- Keep your workspace clean and free from combustible materials.
Conclusion
By following a structured preheating process, you not only extend the service life of your medium frequency induction melting furnace but also improve melting efficiency and production stability. For high-performance furnaces and technical support, choose a trusted manufacturer like Luoyang Judian—serving global foundries with reliable, efficient, and durable induction melting solutions.
