Material selection has always been a deciding factor in whether a metal manufacturing project thrives for decades or fails within months.
It’s easy to think of sheet metal as a commodity, with price as the only consideration. However, the chemical makeup and physical characteristics of an alloy affect the entire product lifecycle, from the ease of metal fabrication to the total cost of ownership.
As an engineer, buyer, or project manager, your primary responsibility is to find the best balance between product performance and budget constraints.
But defaulting to industry standards or assumptions risks either over-engineering or under-engineering. Therefore, the decision should be based on the specific use case.
A Brief Overview of Standard Fabrication Materials
To better understand specific decision criteria for metal projects, it helps to explain the “Big Three” materials that comprise the majority of metal manufacturing today.
Carbon steel is an iron-carbon alloy, used primarily for its strength and high manufacturability. It’s the primary structural material for industrial applications
Stainless steel is similar to carbon steel in that it utilizes iron as the primary component. However, stainless steel adds chromium to provide a corrosion-resistant surface. Due to this addition, stainless steel is the preferred choice in hygienic or harsh environments.
Finally, aluminum is a unique material. Unlike carbon and stainless steels, aluminum is lightweight and non-ferrous. It has an exceptionally high strength-to-weight ratio and is highly resistant to atmospheric oxidization.
Bottom line: When it comes to sheet custom metal fabrication, carbon steel, stainless steel, and aluminum account for the majority of all custom projects, each with its own unique strength. Carbon steel is often ideal for achieving structure. Stainless steel is typically the “go-to” material for protection. Aluminum is effective for weight savings.
How Does Environment Dictate Metal Fabrication Choice?
Corrosion costs the U.S. economy over $450 billion each year. The environment, where the part will operate, will determine the degree of corrosion it will experience.
There is little to no chromium in carbon steel (or “mild steel”), making it highly susceptible to oxidation.
If the material will be used outdoors or in human environments, it will need secondary finishes such as powder coating or galvanization to withstand exposure.
In contrast, stainless steel is more useful in caustic environments because of its relatively high chromium content (at least 10.5%). This causes it to develop a “passive” layer that self-repairs when damaged (i.e., scratched), providing excellent resistance to moisture and chemical corrosion.
Aluminum develops a natural oxide layer that protects against moisture, so it doesn’t require paint. However, its ability to maintain strength diminishes rapidly at temperatures above 180°C (356°F).
Therefore, when selecting a material for high-heat applications, such as exhaust systems or furnaces, specific stainless steel grades are more suitable to maintain structural integrity.
In addition to the effects of weather and heat, chemical exposure also dictates material selection. Industrial kitchens, chemical processing facilities, and other environments that require repeated cleaning with harsh chemicals often require stainless steel due to its non-corrosive surface.
Bottom line: Environmental exposure and operating temperature are the primary factors in determining whether carbon steel, stainless steel, or aluminum is the best choice for a given application.
Balancing Physical Properties: Weight, Conductivity, and Magnetism
While durability is an important consideration, material choice also depends on specific performance metrics, such as density and magnetism.
Carbon steel is the benchmark for structural loads. However, its high density and magnetic permeability are often limitations. Aluminum, which is roughly one-third of the weight of steel is a drastically lighter alternative. This makes it essential for aerospace or automotive components, where weight reduction impacts efficiency.
Conductivity and magnetism are also considerations. Because of its excellent thermal and electrical conduction, aluminum is used for heat sink applications.
While stainless steel doesn’t conduct thermal or electrical energy as well, it’s the preferred choice alongside aluminum for sensitive electronic or medical enclosures. This is because both can be non-magnetic.
On the other hand, carbon steel is highly magnetic and can cause interference in these environments.
These properties also affect custom sheet metal fabrication handling. For example, aluminum and polished stainless steel scratch and mar easily, requiring shops to use protective films and non-marking tooling to maintain the integrity of the parts through the assembly process.
Bottom line: Materials are typically selected based on weight savings, thermal conductivity, or magnetic neutrality, all of which impact end-user performance.
How Does Material Choice Impact Fabrication Complexity?
The term “workability” describes how easy it is to shape, form, cut, or join a metal during manufacturing without cracking, tearing, excessive tool wear, or loss of dimensional accuracy.
Workability affects lead times and labor costs. Different metals have varying levels of workability.
The “workhorse” of all metals is carbon steel, as it offers exceptional ease of welding and forming, allowing for maximum efficiency while minimizing tool wear. Stainless steel “work hardens” very easily when it is manipulated. Therefore, stainless steel requires very high-quality tooling and more powerful laser cutting equipment, which increases labor costs.
Aluminum is, in general, easy to form (bend), but it can be “gummy” during machining. Therefore, TIG welding requires more skilled labor because it dissipates heat rapidly.
Both aluminum and stainless steel require tighter control over bend tolerances than carbon steel. Their unique elasticity results in greater springback during the forming process than standard carbon steel.
Bottom line: Fabrication complexity varies significantly. Carbon steel offers the broadest manufacturability, whereas aluminum and stainless steel require specialized production techniques.
Understanding the Total Cost of Ownership
Looking at the “finished” price is more accurate than a raw material quote. Carbon steel is the most budget-friendly raw material, but adding professional powder coating or plating narrows the price gap between it and aluminum or stainless.
Logistics also play a role. Since carbon steel is easier to weld, it often moves through the shop faster, reducing lead times.
Maintenance frequency is the final piece of the puzzle. Carbon steel may require periodic recoating to prevent rot, whereas the “set it and forget it” nature of stainless steel often justifies its higher upfront price over a ten-year lifecycle.
Bottom line: Total cost of ownership in sheet metal fabrication extends beyond raw material pricing to include fabrication effort, finishing requirements, and service life.
Partner With Fabrication Experts
Deciding on the ideal material is a foundational step that influences everything from upfront expenses to the long-term reliability of your product. By partnering with a knowledgeable fabrication team, you benefit from professional expertise regarding which alloys offer the best machinability and which will withstand your specific operating conditions.
To ensure your next project is engineered for maximum value and efficiency, contact Fluid Power Support to consult with our specialists today.
