For most metal projects, an engineer has to choose between steel and aluminum. Two incredibly common metals, with different mechanical properties. Picking the right option can save you a lot of time and money, and the wrong option can lead to catastrophic failures and parts breaking.
With lots of experience with both options, our expert machinists are here to describe the differences between steel and aluminum, and which option is right for you.
What Is Steel?
Steel is a combination of iron and carbon, plus a few other added elements. Steel can be alloyed with elements such as chromium, nickel, molybdenum, manganese, or vanadium to fine-tune the mechanical properties you get as a result.
Within the world of steel, there are various different options:
- Carbon steel is an affordable, strong type of steel that is used for structural and high-wear parts.
- Alloy steel contains multiple different elements, and it’s used in very similar applications as carbon steel.
- Stainless steel contains at least 10.5% chromium, making an oxide layer that prevents corrosion.
Through the right combination of added elements, steel can change its hardness, wear resistance, corrosion resistance, and strength.
In general, steel is a stronger metal than aluminum, and it weighs more.
Pros of Steel
Steel is a strong metal, often used in industrial and structural applications to support multiple tons of weight. In addition, steel is highly durable; the same part can last for a long time before failing, and it requires less maintenance to upkeep a steel part.
Cons of Steel
The biggest drawback of steel is its weight. It is around three times heavier than aluminum, which can be a disaster for projects that have low weight allowances. Using steel on a vehicle means higher strength but more weight, hurting the fuel efficiency and performance of the vehicle.
Another potential downside of steel is that it is magnetic, since it contains iron.
While steel is easier to weld than aluminum, it can be more difficult to machine. We have to be careful with our feed and speed settings to avoid potential work hardening of steel while CNC machining it.
Unless coated, most steels will corrode over time. This only gets worse when steel is exposed to wet or salty conditions.
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What Is Aluminum?
Aluminum is a lightweight, non-ferrous metal that has an impressive strength-to-weight ratio. Aluminum is naturally corrosion resistant, and doesn’t require additional alloying or finishing steps to achieve this.
Pure aluminum is pretty useless in most industries, so a vast majority of aluminum we work with is an alloy. 6061 is the most common aluminum alloy, and it boasts a nice combination of strength, durability, low weight, corrosion resistance, and ability to be machined, welded, and bent without any issues.
Aluminum is also great at dissipating heat and managing thermal energy.
Pros of Aluminum
Aluminum is a great metal across the board. It has good corrosion resistance, thermal resistance, and electrical conductivity. Aluminum is lightweight and easy to use in manufacturing, so many engineers use it as their go-to metal in most projects.
When you want to cut weight with a metal part, aluminum is the most affordable way to do so.
Additionally, aluminum is a versatile material that can be used in countless applications and industries. It’s hard to think of a single industry that doesn’t use some amount of aluminum, and it’s easy to think of a handful that almost exclusively use aluminum.
Cons of Aluminum
The biggest drawback of aluminum is its inability to handle heavy weights. It fails much sooner than steel, so it’s not a good idea to use aluminum for structural members. In cyclic loading, aluminum will fail before a steel part.
Additionally, aluminum loses strength more quickly in elevated temperatures, so it’s not a good choice for high-temperature operations.
Steel vs Aluminum in CNC Machining & Fabrication
From a machining perspective, there’s no problem with using either steel or aluminum. Our CNC machines and machinists have no issues running either material. However, aluminum does tend to be easier and faster to cut since we can use higher speeds due to aluminum’s ability to dissipate heat well.
As far as surface finishes, aluminum gets a smooth finish quicker since it’s a softer material, and we might have to do post-processing on a steel part to achieve the same finish.
To meet really tight tolerances, steel is a little easier since it is stiffer, making it easier to maintain dimensional stability. But again, both materials are fine options and we can make high-precision steel or aluminum parts.
In general, fabrication for both steel and aluminum poses no issues for our team at Rapid Axis. The only time things get complicated is if you opt for a specialty alloy that meets the needs of your project. Even then, we can handle the fabrication.
Choosing Between Steel and Aluminum
Choosing between steel and aluminum tends to be tricky. Both of these are versatile, readily-available, super ubiquitous materials. In most applications, you can use either material and it will work.
Broadly speaking, aluminum is the better option if you want some added corrosion resistance, you don’t have to worry about heavy loads, and you want to save a little bit of money on material and manufacturing costs.
Steel is the better option if you want a stronger part that lasts longer, and you don’t mind choosing the more expensive stainless steel alloy, or using powder coating to achieve corrosion resistance.
Conclusion
Steel and aluminum are both really popular metals that play major roles in industries across the globe. Our team at Rapid Axis can help you understand which choice is perfect for your next project, and we’re always here to explain the differences between these two metals.
Luckily, our expert machinists and fully-equipped machine shop can handle almost any steel or aluminum project you have for us. As manufacturing experts, we’ve created countless steel and aluminum parts, and we have the background required to achieve great results.
You can get a free quote from us today and learn why you should trust Rapid Axis to be your manufacturing partner.
