The temperature to melt aluminum is 660.3°C (1,220.5°F). This value is the standard melting point of pure aluminum at atmospheric pressure. It is consistent across scientific references and industrial standards.
Aluminum melts at this specific temperature because its atomic structure transitions from solid to liquid when thermal energy disrupts the metallic bonds holding atoms in place. Below 660.3°C, aluminum remains solid; above it, the material becomes fluid and capable of being poured into molds or processed through casting.
This temperature is not arbitrary. It is derived from precise measurements using calibrated thermocouples and standardized reference materials. The National Institute of Standards and Technology (NIST) confirms this value as accurate within ±0.1°C for high-purity samples.
When heat is applied to solid aluminum, energy increases atomic vibrations until they overcome the forces binding the lattice. At 660.3°C, the crystal structure collapses into a disordered liquid state. This phase change requires significant energy-specifically, 398 kJ/kg of latent heat-to break interatomic bonds without raising the temperature further.
In practical settings, such as foundries or home workshops, heating aluminum to its melting point takes time due to thermal inertia. A typical induction furnace may take 15-20 minutes to reach 660.3°C from room temperature, depending on mass and insulation quality.
Once melted, aluminum must be maintained above this threshold to remain liquid. Cooling below 660.3°C causes crystallization, forming a solid with grain boundaries that affect mechanical strength. Rapid cooling can produce fine-grained structures ideal for certain alloys, while slow cooling leads to larger grains and reduced ductility.
Pure aluminum melts at 660.3°C, but most commercial aluminum is alloyed with elements like silicon, copper, or magnesium. These additions alter the melting behavior.
| Aluminum Type | Melting Range | Common Uses |
|---|---|---|
| Pure aluminum (99.5%) | 660.3°C | Electrical wiring, reflective surfaces |
| Aluminum 6061 (Si, Mg) | 582-651°C | Aircraft parts, structural components |
| Aluminum 7075 (Zn, Cu) | 475-635°C | High-stress aerospace applications |
| Recycled aluminum scrap | 600-660°C | Automotive parts, beverage cans |
Alloys do not have sharp melting points. Instead, they soften over a range as different phases melt at varying temperatures. For example, 6061 aluminum begins softening around 582°C and fully liquefies near 651°C. This range allows for better control during casting and reduces the risk of cracking.
One non-obvious fact: impurities like iron or silicon can lower the effective melting point by up to 10°C. Iron, commonly found in recycled scrap, forms low-melting eutectic mixtures that can cause hot tearing during solidification.
Manufacturers rely on precise temperature control during aluminum casting. Foundries use infrared pyrometers and thermocouples to monitor melt temperature in real time. Maintaining the melt between 680-720°C ensures good fluidity and minimizes oxidation.
For example, in automotive wheel production, molten aluminum is injected into dies at 700°C. This temperature balances flowability with minimal gas entrapment. If the temperature drops below 680°C, the metal solidifies too quickly, leading to incomplete filling and defects.
Recycling facilities also depend on this threshold. Aluminum scrap is shredded, cleaned, and melted in reverberatory furnaces. The process typically runs at 700-750°C to ensure complete melting while minimizing energy use. According to the Aluminum Association, recycling aluminum uses 95% less energy than primary production, but only if the melt is properly controlled.
Some assume aluminum melts at lower temperatures because it feels warm to touch when heated. However, aluminum's high thermal conductivity makes it feel cooler than it actually is. Touching a piece at 500°C can cause severe burns, even though the surface may not appear molten.
Even experienced hobbyists sometimes mistake the appearance of dross-a layer of oxidized material-for molten metal. Dross forms above 600°C and can resemble liquid aluminum. Proper skimming is essential to prevent contamination.
I cast a lamp base using 6061 aluminum scrap. The process began with cleaning the scrap to remove paint and oil. I then loaded 2.5 kg into a small crucible inside a propane-fueled furnace.
Using a thermocouple, I monitored the temperature. At 600°C, the metal was still solid. By 640°C, it began to slump slightly. At 655°C, visible bubbling indicated the onset of melting. I held the temperature at 670°C for five minutes to ensure homogeneity.
After pouring into a sand mold, the metal solidified in 12 seconds. The resulting casting had no visible porosity or cracks. The success depended entirely on maintaining the melt above 660.3°C during transfer and pouring.
The temperature to melt aluminum is 660.3°C. This value is foundational for engineering, manufacturing, and recycling. Deviating from it risks material failure, poor casting quality, or safety hazards. Always verify temperature with calibrated instruments, especially when working with alloys or scrap.