Aluminum is a popular light alloy, only second to oxygen and silicon in abundance. When it comes to aluminum, understanding the melting point is crucial for material science, engineering, and many other fields. Let’s explore the basics of melting aluminum together.
Does Aluminum Melt?
Like any metal or alloy, aluminum melts at a certain temperature. The temperature at which aluminum melts depends on various factors, including the alloy.
The metal comprises numerous grains that are arbitrarily set in the material. The result is a polycrystalline structure, which is subject to change in volume upon heating. This melting process defines the melting point, which we describe next.
What Is The Melting Point of Aluminum?
The melting point of aluminum is the temperature at which the volume change we have described above takes place, as the metal changes state from solid to liquid. For pure aluminum, this volume change is rapid. The heat involved in this transformation is termed the latent heat of fusion. As we have indicated, the melting point of pure aluminum and its alloys can differ.
Pure Aluminum’s Melting Point
Pure aluminum melts at the temperature 660.32 °C, which is approximately 1220.58 °F. Compared to stainless steel and zinc, this melting point is about double and half respectively.
Melting point of Wrought Aluminum Alloys
Wrought aluminum alloys are alloys that have undergone extrusion, forging, or any other mechanical process. Take these alloys 2024, 3003, 6061, and 7075 for example. Their melting points are as indicated in the table below.
| Aluminum Alloy | Melting range (°C) | Melting Point (°F) |
|---|---|---|
| 2024 (Copper alloy) | 500 to 635 | 932 to 1175 |
| 3003 (Manganese alloy) | 640 to 655 | 1184 to 1211 |
| 6061 (Magnesium and silicon alloy) | 580 to 650 | 1076 to 1202 |
| 7075 (Zinc alloy) | 475 to 635 | 887 to 1175 |
Melting Point of Cast Aluminum Alloys
Cast aluminum alloys emanate from sand casting, die casting and other casting processes. They are markedly different from standard aluminum in properties and microstructure and are designed to become fluid upon melting. This fluidity is attained by the addition of special alloying elements, for instance, silicon. Examples of cast aluminum alloys are Cast Aluminum A360, Cast Aluminum 380, and Cast Aluminum A356.
The melting points for these cast aluminum alloys are captured in the table below.
| Aluminum Alloy | Melting Point (°C) | Melting Point (°F) |
|---|---|---|
| B390 | 510 to 649 | 950 to 1200 |
| A360 | 577 | 1071 |
| A380 | 566 | 1051 |
| A356 | 555 to 615 | 1031 to 1139 |
Melting Point of Aluminum with Different Finishing
The type of surface finish of aluminum does not affect the melting point of the metal. That’s because the melting point is intrinsic to the material. However, the type of surface finish can determine how heat reaches the metal.
The main finishings to highlight are anodized aluminum, powder-coated aluminum, and painted aluminum.
Melting Point of Aluminum in Different Applications
| Application | Melting Point of Aluminum Alloy |
|---|---|
| Aluminum Foil | Aluminum foil is available in the following alloys, which are corrosion-resistant and strong.
Their melting points are indicated:
|
| Aluminum Wire | Aluminum wire is typically
|
| Aluminum Cans | Aluminum cans are available in a variety of aluminum alloys including
|
| Aluminum Scrap | Aluminum scrap potentially contains a wide range of aluminum alloys.
Thus, the melting point can be anything from 500°C to 660°C. |
| Aircraft Aluminum | Aircraft manufacture uses aluminum alloys, the most predominant ones being:
|
| Aluminum in Automotive | Aluminum alloys for the automotive industry are
|
| Construction Industry | Uses 6063 (600 – 650°C) and 6005 (605°C), among others. |
| Electrical and Electronics | Common alloys are
|
| Marine Industry | Common alloys are
|
| Packaging Industry | Common alloys used are
|
| Casting Applications | Alloys include A380 (566°C), A360 (577 °C), and A356 (555-615℃). |
| Cookware | Common aluminum alloy is 3003 (644 to 654°C) |
Knowing Aluminum Melting Point in Manufacturing and Fabrication Process
Heat control is paramount in manufacturing and fabrication processes. Whether you are welding or using the CNC cutting method on aluminum, you need to know the potential reaction of the material to the heat generated.
Aluminum Welding
Compared to many engineering materials, aluminum melts at a much lower temperature. At 660.32 (°C), welding pure aluminum can be challenging. Even for the alloys, a good grasp of the melting points, hot cracking, among other dynamics, and suitable welding methods, is necessary. Common aluminum welding techniques are MIG welding, TIG welding, and laser welding.
Aluminum Casting
In aluminum casting, the goal is to mold molten aluminum into specific shapes. The automotive, aerospace and many other industries apply this method to create a wide range of components. Aluminum’s melting point is significant in aluminum casting.
Aluminum Forging
Aluminum forging entails subjecting the material to compressive forces via molds or dies, a process that is common in the automotive and construction industries. During this process, the temperature of aluminum is important because exceeding or falling below the recommended temperature can cause defects.
If the temperature during forging exceeds the melting point of the material, extreme cracking will occur. Due to the reduced complexity of the aluminum part, more machining may be required, potentially increasing the manufacturing cost.
Aluminum Extrusion
Aluminum extrusion has many applications in automotive parts, trucks and trailers, golf carts, windows and doors, architectural construction, solar panel frames, and LED lights. Aluminum extrusion involves passing the material through a special die to generate the required cross-section. Preheating the material during this process is crucial, but this temperature must not be too high because it can cause the formation of cracks and bubbles in the material.
Factors Affecting Aluminum Melting Point
Like other metals, aluminum’s melting point is dependent on several factors.
Presence of chemical impurities in the metal. Practically, aluminum and its alloys contain impurities. These impurities, however insignificant, can alter the melting point of aluminum. On the introduction of impurities in the aluminum, the original crystalline lattice becomes defective. Some impurities will increase the melting point while others will lower it. For instance, lithium usually increases the melting point of aluminum while iron lowers it.
External conditions can also affect the aluminum melting point of aluminum. Notable conditions include air humidity and air pressure. High altitudes and the associated low air pressure tend to reduce the metal’s melting point. Aluminum may also react with oxygen and moisture, leading to corrosion and a change in the melting point.
Alloying elements present in the metal can also influence the melting point. You can add an alloy in the metal to attain the melting point that you desire. For example, there are instances when the altered melting point reduces the challenges of machining. That said, it is rare to find pure aluminum in applications.
Properties of Aluminum in High-Temperature Applications
When subjected to high temperatures, aluminum shows varied properties, which can either be advantageous or disadvantageous.
At a low melting point of just 660°C, aluminum may not be useful in applications where the temperature is close to this melting point. Traditionally, A2618, A4032, and several other aluminum alloys have been used in high-temperature applications, including in aerospace. However, these materials tend to weaken at temperatures above 300°C.
For aluminum to be suitable for higher temperatures, newer alloys with superior temperature resistance properties have emerged. These aluminum alloys are so good at these elevated temperatures that they can even replace steel.
To attain these superior properties, these alloys are processed using powder processing and other advanced methods.
Creep is another challenge of aluminum at elevated temperatures. In creep, the material under constant stress experiences deformation over time. At lower temperatures usually below 95 °C is not a problem. It does become an issue as the temperature exceeds this level.
Aluminum presents decent thermal conductivity, but many people usually overlook this property. Aluminum is more capable of conducting heat than many other alternatives, so users in industries such as electronics and aerospace opt for it.
Aluminum has high thermal expansion capability, a property that could be undesirable in various applications. Its expansion and contraction capability under temperature changes is higher compared to what steel and other metals offer. So, if you are looking for tight tolerances in your product, aluminum may not be a recommendable material.
Another property of aluminum to be concerned about at high temperatures is specific heat capacity. Approximated at 900 J/kg°C, the specific heat capacity of aluminum is relatively low, meaning that the heating and cooling process of the material is fast. For this property, aluminum is prominent in cookware, radiators, HVAC systems, and energy storage.
Melting Point Comparison of Aluminum to Other Metals
Melting Point vs. Boiling Point of Aluminum
What’s the difference between the melting point and boiling point of aluminum? While the melting point is where the metal changes phase from solid to liquid, the boiling point refers to the temperature of the liquid metal changing to a gaseous state. Pure aluminum melts at 660.32 (°C) and boils at 2579 (°C).
Melting Point of Aluminum vs. Steel
Similar to aluminum, the melting point of steel varies with the composition. For instance, standard steel melts at 1370°C, and stainless steel at about 1450°C. Pure aluminum melts at the temperature of 660.32 (°C). As a result, steel has a much higher melting point than aluminum, which gives it an advantage in high-temperature use.
Melting Point of Brass vs. Aluminum
Brass has a higher melting point (930°C) compared to that of pure aluminum (660.32 °C). Most aluminum alloys have a lower melting point than brass.
Melting Point of Copper and Aluminum
The melting point of copper (1084°C) is higher than that of pure aluminum (660.32 °C). Copper has a higher melting point than aluminum, giving it an advantage over aluminum in some applications that require high-temperature environments.
Conclusion
Understanding the melting point of aluminum is paramount for stakeholders in diverse industries, manufacturing included. Aluminum melting points vary, and recognizing this fact will help fabricators and manufacturers make the right decisions. Consider the temperature limits identified here when processing or manufacturing aluminum for enhanced safety, efficiency, and profits.
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