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Aluminum vs. Steel Properties: Strength, Ductility, Cost & Weight

aluminum vs. steel properties

Both aluminum and steel are hallmarks of metal manufacturing. Both are useful, commonly used metals. Both don't commonly appear nature like silver or gold. So who wins the battle of aluminum vs. mild steel when it comes to your specific needs?

Aluminum goes through a few phases before it looks like the shiny silver metal we're all familiar with. The base ingredient of aluminum is a mineral called bauxite, which is mined primarily in tropical areas. The bauxite is ground into a thick paste called alumina, which is then smelted with molten cryolite and shocked with electricity. The ions separate, and the residual liquid cools and becomes the aluminum we know and love.

Steel, on the other hand, is a mixture of the elements iron and carbon. Iron is mined, smelted (forming the intermediate material pig iron), the impurities are removed, carbon is added, and the result is carbon steel. This is the base for other types of steel, such as stainless and chrome-molybdenum.

Knowing the pros and cons of aluminum vs. steel properties gets your project off to the right start. How do you know which one is better for your design?

Aluminum Vs. Steel Properties

  Mild/Carbon Steel Stainless Steel Aluminum
Cost Low High Medium
Weight High High Low
Strength High High Low
Ductility Low for carbon,
medium for mild
High High



Cost

Steel cost vs. aluminum cost is always a hot topic, especially with all the tariffs on imported goods our U.S. administration is throwing around.

Steel tubing varies in price due to the differences in carbon, mild, and stainless steel. Stainless steel alloys are made with a certain percentage of chromium and other trace minerals, which drives the price up.

Basic carbon steels and mild steels are much cheaper, and aluminum's price falls somewhere between carbon and stainless steel. These basic steels win in the cost category.

However, as with most things, there are other sacrifices made if you choose the low prices of carbon steel over aluminum alloys. But, for most components, carbon or mild steel are perfectly acceptable materials, even when taking those sacrifices into account.

Related: 4 Ways to Cut Aluminum Tubing Costs with the Right Vendor

Weight

For steel, one of the biggest sacrifices is in the material's strength-to-weight ratio. Carbon steel is heavy. Aluminum is often preferred for its lightweight composition -- steel is much denser compared to aluminum, which causes its weight to skyrocket.

Mild steel is lighter than its carbon counterpart, but it's much flimsier than aluminum at the same weight. Is stainless steel heavy too? You bet -- aluminum is about 1/3 the weight of basically any steel.

In the weight category, aluminum takes the prize. Overall, it's a very lightweight yet sturdy material.

Strength

How strong is aluminum compared to steel?

Steel tube vs. aluminum tube strength is not even close in most cases. The amount of carbon in steel makes it unyielding (and heavy). This is especially true for carbon steel -- the higher the amount of carbon in an alloy, the harder it becomes.

Mild steel is a "low carbon" steel, which is why it's so flimsy compared to other steels and aluminum (and much cheaper in comparison).

Ductility

Which is more ductile, steel or aluminum? This may be very important if your application will involve electricity.

Carbon steel is NOT very ductile. Carbon, which is a benefit to the strength of the metal, ultimately makes the material harder to manipulate.

Is aluminum ductile? More so than carbon steel and even mild steel. If your project requires a malleable metal, you might be able to get away with mild steel, though.

Steel Vs. Aluminum Is About More Than Just Cost

These are some of the things you should think about when choosing the right type of metal for your project. There may be other factors to consider, but we would suggest not making your decision based on cost alone.

If you're searching for one of the qualities not mentioned here, such as corrosion resistance, check out this blog post about 316 stainless steel and other related alloys. Or, if you're got materials squared away and are ready to start designing, click below for a free bending guide:

tube bending design guide for design engineers

 

(Editor's note: This article was originally published in September 2015 and was recently updated.)

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