Picking the right material is a critical first step for any manufacturing project. Although they sound like the same thing, carbon steel and alloy steel are drastically different materials, both having their own set of mechanical properties that can make or break your project. With these two common steel choices, it might not seem clear which option is right for you.
In this guide, you’ll learn the difference between alloy steel and carbon steel, and which steel option is better for your projects.
What Is Carbon Steel?
Carbon steel is a simple version of steel that only includes trace amounts of other metals and elements. Also called “mild steel”, it is composed primarily of iron and carbon. Fun fact: since there is no element on the periodic table called “steel”, technically every type of steel is an alloy, since it is a combination of iron and carbon. In this case, carbon steel is the simplest version of this alloy, with other materials added to create different alloys of steel, which we’ll discuss later.
Since carbon steels consist of carbon and iron, there are different ranges, going from “low-carbon” to “high-carbon” steels. Lower carbon values under 0.3% are easier to weld and form, so you might use low-carbon steel for stamped parts or typical machined parts. Higher concentrations of carbon, usually above 0.6%, are brittle and harder to work with, but they’re stronger and more abrasion-resistant.
Carbon steel’s mechanical and physical properties rely solely on the concentration of carbon within the material, so there isn’t a lot of flexibility when it comes to the properties you’ll find. Comparatively, alloy steels can almost be fine-tuned to achieve the exact physical properties you’re looking for.
For example, 6061 is often chosen for CNC machining because it offers stable cutting behavior and balanced strength. In contrast, 5052 is preferred for aluminum sheet applications where bending and corrosion resistance are critical. Knowing these tradeoffs early helps avoid issues such as cracked bends, warped welds, or unnecessary machining cost.
Pros and Cons of Carbon Steel
Since the alloy of carbon steel is so simple, it’s much easier to manufacture the stock material. This translates to lower costs for raw material, and more availability. If your project has strict budget constraints or you just want to quickly put together a part, a carbon steel like 1045 or 1018 is a great starting point.
You’ll find carbon steel bars, plates, sheets, tubes, and other geometries off-the-shelf, so we can produce custom parts with less machining, which saves you money. In addition, machining carbon steel is relatively easy for our guys to do. Since it saves us time and tooling costs, we can pass the savings on to you.
The downside is that high-carbon steels can be trickier to machine and might need some post-processing to smooth out the finish.
The major downside to carbon steel is that there are no added elements to prevent corrosion, so carbon steel parts will rust over time. In humid or wet environments, the rust can start pretty quickly. A quick workaround is to powder coat your carbon steel parts, which adds some time, money, and complexity to parts, but it can still be more affordable than using an alloy steel or stainless steel.
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What Is Alloy Steel?
Alloy steel takes carbon steel a step further by adding extra elements. Typically, these added elements are a combination of chromium, nickel, molybdenum, manganese, and vanadium in varying concentrations.
These elements are added to fine-tune the mechanical properties of the resulting alloy steel parts. With many elements to choose from, you can find alloy steels with a huge range of performance characteristics. Chromium makes the alloy harder and more corrosion-resistant, nickel makes the part tougher and more impact-resistant, molybdenum adds high-temperature strength and makes parts less brittle, and so on.
With the right combination of the right elements, you can find steel alloys that match the exact demands of your projects.
Aerospace projects will rely on alloys that balance strength and ductility, while marine operations will use parts that are great at handling moisture without corroding.
Pros and Cons of Alloy Steel
With the added flexibility when it comes to mechanical properties, the major benefit of alloy steel is that you can find an alloy that is perfect for your project.
Alloy steels are still (for the most part) easy to machine and manufacture, and we can work with a variety of alloy steels at Rapid Axis with no problems. Alloy steels can perform better under mechanical stress and high loads, have better fatigue strength, toughness, and high-temperature performance.
Importantly, alloy steel is corrosion-resistant without added finishing steps, leading to more durable and long-lasting parts.
However, alloy steels are often more expensive than carbon steel. Not only is the raw material more expensive, but the extra tooling and machining complications can make alloy steel projects even more expensive. In addition, welding can be very difficult for certain alloys of steel.
For standard alloys like 4140, it’s not hard to find raw material, but specialty alloys can be really tough to source.
Carbon Steel vs Alloy Steel
The decision between carbon steel and alloy steel comes down to the requirements of your project. It doesn’t make sense to just suggest one of these steels for you to use moving forward, it’s a consideration you have to make with each design.
Carbon steel is less expensive, easier to work with, and easier to source. For that reason, we suggest it for any “general use” projects, such as machine guards, part fixtures, jigs, load-bearing frames or brackets, and parts that will be used in controlled, dry environments. We also suggest considering powder coating for all of your carbon steel parts so you can fight against corrosion.
For any project that has specialized mechanical requirements, alloy steel is likely the better option. Even common alloy steels like 304 or 316 offer great corrosion resistance, better mechanical properties, and better durability over carbon steel. They are more expensive to source and manufacture, which is why we only suggest using alloy steels when the project demands it.
| Carbon Steel | Alloy Steel | |
| Cost | Lower | Higher |
| Machinability | Easier to work with | Harder to manufacture |
| Availability | Easy to source | Can be harder to source, depending on alloy |
| Corrosion Resistance | Low (needs powder coating) | Higher (e.g., 304 or 316 alloys) |
| Best For | General use projects | Specialized projects with demanding mechanical requirements |
While there is technically nothing wrong with using alloy steels for every project and never using carbon steel, you will likely overpay for simple alloy steel parts that could be made out of carbon steel instead.
Our experts are here to field questions about your specific project to ensure you’re choosing the right material.
Conclusion
As you saw, carbon steel and alloy steel have some key differences that make either option better for certain projects. Understanding the difference between the two can mean saving money and time on your upcoming projects, while avoiding parts that fail due to being made out of the wrong material.
For help with either alloy steel or carbon steel manufacturing, you can trust Rapid Axis. Our expert machinists have tons of experience working with all types of steel alloys, and we know the right machine settings to get the best results. We also offer a range of finishing options to ensure your parts are set up for success.
Reach out today to get a free quote and get started with Rapid Axis.
