I get emails every week from foundry managers, maintenance engineers, and plant owners asking the same questions. Some are simple. Some are not. But they all come from the same place: someone trying to make a decision without the information they need.
I have spent 25 years commissioning, troubleshooting, and selecting aluminium melting furnaces. I have written hundreds of articles. But the same questions keep coming back.
So I collected the ten most common ones. These are the ones I answer most often. The answers are not from a brochure. They are from the shop floor.
1. What is the best furnace type for my application?
There is no universal best furnace. The right furnace depends on your feedstock, your alloy, your production volume, and your quality requirements.
| Furnace Type | Best For | Not For |
|---|---|---|
| Crucible | Small volume, frequent alloy changes | High volume, single alloy |
| Reverberatory | High volume, clean scrap | Contaminated scrap, frequent changes |
| Rotary | Contaminated scrap, dross | Clean scrap, high quality |
| Twin-chamber | Mixed scrap, high recovery | Clean scrap only |
| Tower | High volume, clean, sized scrap | Wet, oily, oversized scrap |
| Induction | High purity, aerospace | High volume, general casting |
I have written about how to choose between crucible and reverberatory furnaces and how to choose a secondary aluminium melting furnace for ingot production. The principles are the same. Match the furnace to the job.
2. How much energy should my furnace consume?
Modern aluminium melting systems achieve 550–650 kWh per tonne under well-optimised conditions. Legacy furnaces run at 1,000–1,200 kWh per tonne.
If your furnace is above 800 kWh/t, you have room to improve. Start with burner tuning. Then check heat recovery. Then check door seals.
I have written about how to reduce energy consumption in aluminium scrap melting furnaces. The biggest wins are almost always in the burner and the recuperator.
3. What is the typical metal loss in a melting furnace?
Metal loss varies by furnace type and operation.
| Furnace Type | Typical Metal Loss |
|---|---|
| Tower | 1–2% |
| Twin-chamber | 2–4% |
| Rotary | 3–6% |
| Reverberatory | 3–5% |
| Crucible | 2–4% |
If your metal loss is above 4%, you have a problem. Check your skimming practice, your temperature, and your flux.
I have written about how to improve metal recovery in aluminium scrap melting and why your furnace has high melt loss. The causes are usually temperature and skimming.
4. How often should I change my refractory?
Refractory life depends on the furnace type, the refractory material, and the operation.
| Furnace Type | Typical Refractory Life |
|---|---|
| Crucible | 3–6 months |
| Reverberatory | 2–5 years |
| Rotary | 1–3 years |
| Tower | 5–8 years |
| Induction | 3–6 years |
If your lining is failing early, check the heating cycle, the flux chemistry, and the burner alignment. I have written about how to improve refractory life with proper heating cycles and how to solve refractory erosion problems.
5. What causes dross formation and how can I reduce it?
Dross forms when molten aluminium meets oxygen. The rate depends on temperature, atmosphere, and turbulence.
To reduce dross:
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Lower melt temperature
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Tune the burner
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Skim less often
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Use a cover flux
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Use non-wetting refractory
I have written about why your furnace has excessive dross formation and how to reduce dross in reverb furnace melting operations. The first thing to check is temperature.
6. How do I choose a furnace supplier?
Choosing a supplier is about more than price. Ask these questions:
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What is the guaranteed melt rate?
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What is the guaranteed energy consumption?
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What is the expected lining life?
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Can I visit a reference site?
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What is the lead time for spare parts?
I have written about how to choose a furnace supplier – 10 questions to ask and how to evaluate furnace manufacturer quality in China. The evaluation criteria are the same everywhere.
7. What is the typical lead time for a new furnace?
Lead times vary by supplier and furnace type.
| Supplier Region | Typical Lead Time |
|---|---|
| China | 3–6 months |
| Europe | 6–12 months |
| Japan | 8–12 months |
| US | 6–10 months |
Chinese manufacturers have shorter lead times. European manufacturers have longer lead times but stronger local service. I have written about why Chinese furnace manufacturers are winning contracts in European markets.
8. How do I reduce hydrogen in my melt?
Hydrogen causes porosity. The target for aerospace is below 0.06 ml/100g. For commercial casting, below 0.15 ml/100g.
To reduce hydrogen:
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Use rotary degassing
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Measure hydrogen before every pour
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Pre-dry scrap
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Seal the furnace
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Lower melt temperature
I have written about why your aerospace aluminium has high hydrogen content and how to reduce gas porosity in die casting aluminium melts. The first thing to check is moisture.
9. What is the difference between holding furnace and melting furnace?
A melting furnace melts solid scrap into liquid metal. A holding furnace maintains the metal at temperature for casting.
| Feature | Melting Furnace | Holding Furnace |
|---|---|---|
| Purpose | Melt solid scrap | Hold molten metal |
| Temperature | Higher | Lower |
| Heating capacity | Higher | Lower |
| Dosing | Not usually | Often |
Some furnaces combine both functions. A twin-chamber furnace melts in one chamber and holds in another. I have written about how to achieve consistent melt temperature in a holding furnace.
10. How do I know if my furnace is running efficiently?
Measure these five things:
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Specific energy consumption (SEC). Target 550–650 kWh/t.
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Metal loss. Target below 2%.
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Dross metal content. Target below 30%.
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Flue gas oxygen. Target 2–4%.
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Door seal condition. No leaks.
If any of these are out of range, you have room to improve. I have written about how to choose an energy-efficient aluminium melting furnace. The same principles apply to evaluating an existing furnace.
When to Call Someone
Some problems you can fix yourself. Some require experience. If you have tried the obvious fixes and the problem persists, call someone.
The cost of a consultant is small compared to the cost of a furnace that is not performing.
Final Thoughts
These are the questions I get asked most often. They are not complicated. But they are important.
If you have a question that is not answered here, send me an email. I read every one. If the question is common, I will write about it.
About the Author: Hu Shenyue is a veteran aluminium melting furnace expert with 25 years of hands-on experience in China, Southeast Asia, India, the UK, Europe, and North America. He writes practical, experience-based content on furnace selection, maintenance, and optimisation at SmeltPro.
Internal links: How to Choose Between Crucible and Reverberatory Furnaces for Aluminium Melting, How to Choose a Secondary Aluminium Melting Furnace for Ingot Production, How to Reduce Energy Consumption in Aluminium Scrap Melting Furnaces, How to Improve Metal Recovery in Aluminium Scrap Melting, How to Choose a Furnace Supplier – 10 Questions to Ask.
