What melting loss is
Melting loss (also called metal loss or melt loss) is the amount of metal lost between charging the furnace and pouring. It is expressed as a percentage of the charged weight:
Melting loss % = (charged weight − available liquid weight) ÷ charged weight × 100
The main causes are oxidation of the metal, metal held in the slag or dross, and the loss of some volatile elements. The value varies widely depending on the alloy, the furnace and the quality of the charge.
What it depends on
- Alloy: light alloys and alloys with easily oxidised elements tend to have higher losses.
- Furnace type: induction, crucible, reverberatory and cupola furnaces behave differently.
- Charge: thin material, turnings, dirty or oxidised scrap increase losses compared with clean ingots and returns.
- Temperatures and times: a melt that is held for a long time or overheated loses more.
- Slag handling and melt treatments.
Why melting loss affects costs
Metal is the largest cost item in a casting. Melting loss increases the metal to be bought for every kg poured: if it is not accounted for correctly, the casting cost is underestimated in every quotation. In the same way, component requirements calculated without melting loss lead to material shortages.
Alloy composition
Every alloy is made from a combination of components: ingots or pig iron, internal returns, scrap, ferroalloys, grain refiners, inoculants. The recipe determines:
- the final chemical composition, which must meet the limits of the standard or specification;
- the alloy cost, which depends on the price and percentage of each component;
- the inventory consumption of components.
Controlling chemistry
Composition is checked with a spectrometer on samples taken from the melt. Results must be compared with the minimum and maximum limits of each element for the alloy grade and, if out of tolerance, the melt is corrected before pouring. The final analyses go into the certificates delivered to customers.
How it is usually handled
The alloy recipe often lives in a melt-shop spreadsheet, melting loss is a “historical” value that is never updated, and spectrometer analyses are printed or exported and then retyped into certificates. Component consumption is reconstructed from stocktakes.
The limits of spreadsheets and generic ERP systems
- A fixed, forgotten melting loss: nobody checks whether the value used in costing is still realistic.
- Alloys as plain items: without composition, chemical limits and component prices.
- Disconnected analyses: spectrometer results are not linked to heats, castings and certificates.
- Unreliable component inventory: without issue from production, stock is only corrected at stocktake.
How FOND/WISE handles it
In FOND/WISE every alloy is a complete record linking composition, chemistry, costs and inventory.
- Alloy components: ingots, returns, ferroalloys, grain refiners and other components with their percentages.
- Automatic inventory issue: components are issued from the production declaration, with no manual stock movements.
- Melting loss per alloy: taken into account in MRP requirements and in metal cost.
- Chemical elements per grade: minimum and maximum limits per element, referenced to the EN or ISO standard.
- Automatic import of spectrometer analyses, linked to the heat and to the certificates.
- Price trends: standard price, last price and price history of components.
Key features
Component list
Percentage composition of each alloy with component prices.
Melting loss
Loss percentage per alloy, used in requirements and costs.
Chemical limits
Minimum and maximum per element, by grade and standard.
Spectrometer
Analyses imported automatically.
Automatic issue
Component consumption recorded from production.
Price history
Component prices over time.
Worked example
An aluminium foundry produces 20,000 kg of liquid EN AC-46000 metal per week. The average cost of the charge (ingots, returns and alloying additions) is €2.40/kg. Illustrative values.
| Melting loss | kg to charge | kg lost | Cost of loss per week | Cost of loss per year (46 weeks) |
|---|---|---|---|---|
| 3% | 20,619 | 619 | ≈ €1,490 | ≈ €68,300 |
| 5% | 21,053 | 1,053 | ≈ €2,530 | ≈ €116,200 |
Two percentage points of melting loss are worth about €48,000 a year on this alloy alone. If the standard metal cost was calculated with a 3% loss but the real loss is 5%, every quotation underestimates the casting cost without anyone noticing.
Frequently asked questions
What is melting loss?
It is the difference between the weight of metal charged into the furnace and the weight of liquid metal actually available for pouring. It includes oxidation, metal trapped in slag or dross, and losses from the evaporation of some elements.
How is melting loss calculated?
Melting loss % = (charged weight − liquid weight tapped) ÷ charged weight × 100. To estimate how much to charge: weight to charge = liquid weight required ÷ (1 − melting loss %).
What does melting loss depend on?
On the alloy, the type of furnace, the quality and size of the charge (thin, dirty or oxidised material increases losses), temperatures and holding times, melt treatments and slag handling.
Why import spectrometer analyses into the ERP?
To avoid transcription errors, link each analysis to the heat and the castings produced, compare it automatically with the alloy limits and include it in certificates without retyping it.