What material should I use?
Sometime during the design process of a part, the question of what material to use arises. Should I use aluminum? What about stainless steel? Mild or high carbon steel? The world of sheet metal fabrication is hardly one-size-fits-all. This article aims to break down some of the important differences between common metals; however, it should be noted that the below descriptions are subject to variation based on different alloys and grades of the material.
Aluminum is a very common material used in custom parts manufacturing. There are numerous benefits to using this material. Aluminum is typically more malleable and elastic than steel. As stated previously, there are a couple of notable exceptions, such as alloys 6061 and 2024. Also, the corrosion resistance of aluminum is always a huge plus. It also has a high strength/weight ratio. Notably, it is a good conductor of both heat and electricity. Finally, depending on the grade, aluminum is cheaper than its corrosion resistant counterpart, stainless steel.
Although there are numerous benefits to using aluminum, there are some drawbacks. Steel is much harder than aluminum. Aluminum is more likely to warp, deform, or scratch under heat over 400°F and force. Due to the high thermal conductivity, aluminum is harder to weld. Finally, aluminum is not suitable in culinary applications as it reacts with and changes the color and flavor of food products.
Typical uses: Weight reduction (1/2 the strength of steel at 1/3 the weight), aircraft bodies
Stainless steel is an alloy of steel that contains a minimum of 10.5% chromium which leads to one of the many benefits of the material. The added chromium contributes to the corrosion resistance of stainless steel. Chromium adds a shine to the material that makes it great to use in cases where aesthetics matters. Secondly, stainless is easier to weld than aluminum. Finally, stainless steel is much harder than aluminum. Consequently, stainless is much less likely to warp, deform, or scratch under heat or force. The heat resistance lends stainless steel to be used when sanitation is an important criterion.
The main downside to stainless steel is the cost. Depending on the alloying metals such as chromium, nickel, manganese, and silicon, stainless is typically much more expensive than aluminum or carbon steel. Finally, stainless steel has the lowest strength/weight ratio. This means that while stainless steel is incredibly hard, it is also incredibly heavy. Weight may be a determining factor in some applications.
Typical uses: Food service industry, corrosive environments, household appliances
Mild/Low Carbon Steel
Mild, also known as low carbon, steel contains between 0.14%-0.20% carbon. At Axis, this is the type of material we use the most as it has many benefits. Due to its low carbon content, mild steel is very easy to fabricate. Additionally, mild steel is more malleable than stainless and very easy to weld. Mild steel is also much cheaper than stainless and typically cheaper than aluminum as well. The material exhibits both ductility and great heat transfer.
Although mild steel is very common, it requires galvanizing to prevent corrosion. The susceptibility to corrosion makes mild steel inappropriate in marine settings or in any setting that would frequently come in contact with water. Finally, mild steel is typically lower in strength than stainless.
Typical uses: Most all steel sheet products, automobile panels, computer boxes
High Carbon Steel
High carbon steel is an alloy that contains between 0.60%-2.5% carbon. Due to the increased carbon content, the material has increased hardness compared to stainless steel. Consequently, it is more durable than either aluminum or stainless steel. It is very unlikely to warp, deform, or scratch under heat or force. Finally, depending on the grade, it is the cheapest material.
However, there are some downsides to high carbon steel. Although the high carbon content leads to increased hardness, it also leads to increased brittleness compared to stainless steel. Additionally, it is also not corrosion resistant. It needs to be painted or finished in some way otherwise the material could rust or erode.
Typical uses: Wear plates, springs
Things to Note
- This is a very general comparison of stainless to carbon steel as many of the material’s properties are dependent upon alloying metal content. Varying the amount of carbon, chromium, nickel, sulfur, and others greatly affects the behavior of the material.
- Cost can very based on current metal prices. Once again, in general price/lb goes SS>Al>CS
- Weight/strength: Al>CS>SS
- While both stainless steel and aluminum are resistant to corrosion, it’s hard to compare their relative resistance. Aluminum is more corrosion resistant that stainless at pH around 4-6 while stainless is more corrosion resistant when the pH is above 10. Aluminum will quickly corrode under highly acidic conditions.