{"id":5259,"date":"2026-08-26T11:51:12","date_gmt":"2026-08-26T11:51:12","guid":{"rendered":"https:\/\/aboutfoundry.com\/melting-heat\/"},"modified":"2026-08-26T11:51:12","modified_gmt":"2026-08-26T11:51:12","slug":"melting-heat","status":"publish","type":"post","link":"https:\/\/aboutfoundry.com\/en\/melting-heat\/","title":{"rendered":"Melting Heat"},"content":{"rendered":"\n

Melting heat, also called latent heat of fusion, is the amount of thermal energy a metal absorbs to change from solid to liquid at its melting point, without any further rise in temperature.<\/strong><\/p>\n\n\n\n

Melting Heat Versus Sensible Heat<\/h2>\n\n\n\n

Melting a piece of cold metal takes three separate amounts of energy: sensible heat to warm the solid up to its melting point, latent heat (the melting heat) to convert it from solid to liquid at that fixed temperature, and further sensible heat to superheat the liquid above the melting point for pouring. The melting heat is the step where temperature does not rise even though energy keeps going in, because the energy is used to break the solid’s atomic bonds rather than to speed up atomic motion.<\/p>\n\n\n\n

Typical Values for Foundry Metals<\/h2>\n\n\n\n

Melting heat is a physical constant of each element, not a specification value, so it is quoted in materials handbooks rather than in a DIN standard. Published values vary somewhat between sources, generally within about ten percent, which is normal for this kind of thermophysical data.<\/p>\n\n\n\n

Metal<\/th>Melting Point (approx.)<\/th>Melting Heat (approx.)<\/th><\/tr><\/thead>
Iron<\/td>1538°C<\/td>247 kJ\/kg<\/td><\/tr>
Aluminum<\/td>660°C<\/td>397 kJ\/kg<\/td><\/tr>
Copper<\/td>1085°C<\/td>205 kJ\/kg<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

Practical Relevance: Furnace Energy Demand<\/h2>\n\n\n\n

Melting heat is one of the figures a foundry needs to size furnace energy demand, alongside sensible heat and superheat. Aluminum illustrates why melting point alone is misleading: at 660°C it melts far below iron, yet its melting heat per kilogram is higher than that of iron or copper, which is one reason melting and remelting aluminum is comparatively energy-intensive for the tonnage produced. Alloys behave differently from pure metals here, because they generally solidify over a temperature range instead of at one fixed point, so a single melting-heat figure for an alloy such as cast iron is an approximation rather than a defined constant, the same way its eutectic temperature<\/a> only applies exactly at one specific composition.<\/p>\n\n\n\n

Frequently Asked Questions About Melting Heat<\/h2>\n\n\n\n

Is melting heat the same as melting point?<\/h3>\n\n\n

No. The melting point is a temperature. Melting heat is an amount of energy, usually given in kJ\/kg or kJ\/mol, needed at that temperature to complete the change from solid to liquid.<\/p>\n\n\n\n

Why does aluminum need so much energy to melt despite its low melting point?<\/h3>\n\n\n

Because its melting heat per kilogram is comparatively high, around 397 kJ\/kg, higher than iron or copper. Melting point and melting heat are independent figures, and a low melting point does not guarantee a low energy demand.<\/p>\n\n\n\n

Does alloying change the melting heat?<\/h3>\n\n\n

Yes, and it also changes how cleanly the concept applies. Alloys typically solidify over a temperature interval rather than at a single point, so their effective melting heat is spread across that interval instead of released at one fixed temperature, unlike a pure metal or a composition at the eutectic point.<\/p>\n\n\n\n

Standard Reference<\/h2>\n\n\n\n

No DIN standard defines melting heat; it is a tabulated physical property, not a specification figure.<\/p>\n\n\n\n

Further Terms<\/h2>\n\n\n\n