Aluminum and steel are undoubtedly among the essential types of metals for many industries today – agriculture, transportation, construction, energy, shipbuilding, automotive, etc.
In your next project, you will most likely have to choose between the two metals because their properties are relevant. As you wonder which is better for your parts and project, the following comparison will make the selection easier.
The Difference Between Steel and Aluminum in Factors
The properties of both aluminum and steel emanate from the manufacturing process and chemical composition. Here are some properties of the two metals that you need to consider:
| Property | Aluminum | Steel |
|---|---|---|
Manufacturing |
Processing aluminum is a three-step process: Bauxite mining, alumina extraction, and alumina transformation to aluminum. | Popularly called ‘man-made’ metal because impurity removal from iron defines the process. |
Appearance |
Aluminum has a relatively soft matte finish. It features a little silver appearance. | A shiny metal that is more reflective than aluminum. Its exact look depends on the type. For instance, the shiny silver look is synonymous with steel for cutlery while carbon steel used in architecture is typically brownish. |
Density |
The average density of aluminum is 2.7 g/cm³. | At a density of 7.9 g/cm³, steel is approximately three times denser than aluminum. |
Weight |
Aluminum is lighter than steel. | Steel is heavier, mostly because it has high carbon proportion. |
Cost |
Costs for both metals tend to fluctuate with market demands. However, the cost of aluminum tends to be higher than the cost of steel. | Steel tends to be cheaper than aluminum, but stainless steel is more expensive than aluminum. |
Tensile Strength |
For aluminum, the tensile strength is generally in the range of 60 to 610 MPa.This value is affected by the aluminum alloy and heat treatment. | The range of tensile strength of steel varies by type.The tensile strength of carbon structural steel is 400-840 MPa, alloy structural steel is 500-1100 MPa, strength alloy steel is 800-2000 MPa, and stainless steel is 530-1310 MPa. |
Yield Strength |
The tensile strength is generally in the range of 15 to 540 MPa.This value is affected by the aluminum alloy and heat treatment. | The yield strength of steel is between 200-400 MPa, while the yield strength of high-strength steel can reach 800-1500 MPa. |
Fatigue Strength |
The fatigue strength of aluminum varies widely due to processing factors, alloy type, and heat treatment. It is in the range of 85-135 MPa for 10^7 cycles. | Steel presents much higher fatigue strength. Some steels used in aerospace and automotive industries can have as much as 700 MPa for 10^7 cycles. Plain carbon steel is rated at about 340 MPa for 10^7 cycles. |
Corrosion Resistance |
Naturally corrosion resistant with the formation of aluminum oxide. | Not naturally corrosion-resistant. Users are often prompted to subject the material to further processing due to its proneness to corrosion. The addition of chromium can make steel corrosion-resistant, e.g. for stainless steel. |
Temperature Resistance |
Aluminum has lower temperature resistance than steel. Its melting point is approximately 660°C. | The temperature resistance of steel is higher, with the metal presenting a melting point of 1,400°C. |
Machinability |
Present higher machinability than steel. | Generally lower machinability than aluminum. Stainless steel, with a rating of below 50%, is one of the poorest performers in this regard. Some steel grades though have good machinability. |
Weldability |
Column 2 Value 6 | Column 3 Value 6 |
Workability (Forming and Extrusion) |
Due to its lower tensile strength, aluminum has higher workability. You can easily extrude, bend, cut, or form the metal. | Since it has higher tensile strength, steel is less workable than aluminum. |
Thermal Conductivity |
Aluminum conducts heat better than steel. | Steel is not as good in thermal conduction. |
Thermal Expansion |
Aluminum has a significantly higher thermal expansion compared to steel. Its linear expansion coefficient is 21 – 24 ×10−6 m/m°C. | Steel has a lower thermal expansion than aluminum. It has a linear expansion coefficient of 10.8 – 12.5 ×10−6 m/m°C. |
Electrical Conductivity |
Aluminum has high electrical conductivity. This property makes the metal prominent in high-voltage power lines. | Steel is poorer in electrical conduction. |
Magnetic Properties |
Aluminum has no magnetic properties because it doesn’t contain cobalt, iron, or nickel. It shares the paramagnetic property with materials such as Lithium and Magnesium. | Steel, an alloy of carbon and iron, is magnetic. |
Lifecycle Durability |
Works better than steel in low environmental impact and light-load conditions. | Better for high-temperature and load conditions. Requires countermeasures for corrosion problems. |
Recyclability |
Highly recyclable. It can be recycled countless times without losing its properties. More than three-quarters of aluminum produced in history is still in application. | A limited number of recycling times. |
Environmental Impact |
Bauxite mining contributes to environmental impact through habitat destruction, resource pollution, and worsening of the water scarcity problem in remote areas. | The environmental impact of steel tends to be higher than that of aluminum. A lot of environmental pollution emanates from the highly damaging coke that is used in the process. Naphthalene and other air pollutants related to steel production are extremely detrimental to human health. |
Applications |
Being lightweight and corrosion-resistant, aluminum suits a wide range of industries. Used in different systems for automotive, aerospace, architecture, and many other industries. Applications are engine blocks, beer cans, bus bars, furniture, and so on. | Common in manufacturing, construction industries, automotive, and infrastructure, among others. Its strength and durability ensure long-lasting performance and stability. The applications include making thermal processors, cookware, and framed glass shower enclosures, etc. |
Summary of Physical Properties |
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Which One Is Best for Your Parts, Steel or Aluminum?
If you are unsure about the better option for your project between aluminum and steel, outlining the specific properties as shown above can help. We have identified the key differences and similarities of the two popular metals, providing a strong starting point for decision-making.
Each of these metals has pros and cons. Aluminum is light, corrosion-resistant, and ideal for complex shapes. However, this comes at the expense of strength and heat tolerance, areas where steel thrives in. These are some of the reasons why it is normally not easy to use the metals interchangeably.
Ultimately, the choice of either aluminum or steel will depend on the specifics of your project. If you can, consider as many of the listed factors as possible. Note that costs for installation, maintenance, and any downtimes resulting from material failure can change the overall cost of the project.
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