When it comes to steel, the two most common options are alloy steel and stainless steel. Picking between them can be a little confusing, since they both offer strength and versatility, but the right choice can help your parts last longer and do more for your operation. Our expert machinists at Rapid Axis are here to make the decision easier for you.
What Is Alloy Steel?
By definition, alloy steel is the combination of carbon and iron (steel), and added elements to achieve specific mechanical properties. For example, one alloy of steel might be really easy to weld, another might be super strong, and a third option might be super inexpensive. It all depends on which elements are added and how much of each element is present.
Chromium increases hardenability and wear resistance. Nickel improves toughness and impact resistance. Molybdenum enhances strength at elevated temperatures and reduces brittleness. Vanadium refines grain structure and increases fatigue resistance.
Low-alloy steels have less than 5% of added elements, and they offer better strength.
High-alloy steels have more added elements, and they’re more specialized.
Pros of Alloy Steel
Alloy steel is a more affordable option, and it is often used in structural or high-strength parts. They can be heat treated to be even harder and stronger, as needed.
Alloy steel is also very fatigue-resistant, so alloy steel can be used for gears that are cyclically loaded without failing.
The big benefit of alloy steel is that it’s inexpensive to source and manufacture, so you can save money on your parts if they don’t need to be corrosion-resistant.
Cons of Alloy Steel
The major downside of alloy steel is that it isn’t corrosion-resistant. These parts are very susceptible to rusting, unless they’re powder coated and maintained over time.
In addition, alloy steels tend to be more expensive than carbon steel options, though they are less expensive than stainless steel.
Since a lot of strength and durability comes from finishing steps applied to alloy steel, you’ll need to factor in extra time and money during the manufacturing process. You’ll also need to use a shop like Rapid Axis that offers different finishing options.
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What Is Stainless Steel?
Stainless steel is technically a form of alloy steel that contains at least 10.5% chromium by volume, which creates a thin oxide layer on the outer layer of a part, preventing corrosion for longer. In most industries, stainless steel is the more common option since it doesn’t require finishing steps to achieve corrosion resistance.
Stainless steel is one of the more common metal options on the market. A lot of engineers we work with will use stainless as their default material, unless the project has requirements that can’t be met with stainless.
Stainless can be used to make anything from enclosures to brackets, housings, structural parts, or frames. Many major industries use stainless steel across their assemblies since it is such a versatile material that is readily available and easily sourced.
Pros of Stainless Steel
Arguably the biggest selling point of stainless steel is its corrosion resistance. The material is also strong and durable, and the right stainless steel alloy can last a long time without any maintenance required.
Stainless steel can be a cleanroom-compatible metal, so you can use it in semiconductor, medical, or food processing operations.
Typically, stainless steel is easier to source and find in specific shapes. Stainless can be found in a variety of plates, sheets, rods, geometric pieces, and tubing. With a starting shape and geometry that’s closer to your final product, you can save a lot of time and money during the manufacturing operation.
Cons of Stainless Steel
Although stainless steel exceeds the performance of alloy steel in many categories, you have to pay a premium for the material; stainless steel can be a lot more expensive than standard alloy steels.
Stainless steel can also be harder to machine, since the parts can work harden during manufacturing, which complicates machining and requires additional expertise.
With the added cost and turnaround time for stainless steel parts, you’ll need to make sure your project has the right budget and timeline. While stainless doesn’t have the same complexity that specialty alloys have, it’s still worth mentioning since alloy steel is so much easier to machine.
Alloy Steel vs Stainless Steel
| Alloy Steel | Stainless Steel | |
| Corrosion Resistance | Poor, requires coating or finishing | Excellent, naturally corrosion-resistant |
| Strength | Very high | High |
| Fatigue Resistance | Excellent | Good |
| Machining | Easy | Moderately complex |
| Finishing Required | Yes | No |
| Material Cost | Low | High |
| Availability | Widely available | Widely available |
| Best For | Gears, bearings, structural parts, cost-sensitive projects | Enclosures, frames, cleanroom use, corrosive environments |
These two categories of steel are not interchangeable. When corrosion is a risk, stainless steel is the only option unless you want to go through different finishing steps on an alloy steel part.
Alloy steel is more affordable and easier to machine, so it’s a good option for generic parts that aren’t exposed to moisture or chemicals. It’s a great choice for gears, bearings, and structural brackets.
Stainless steel tends to be more durable, a little stronger, and more long-lasting than alloy steel. Stainless is the better option for consumer goods, industrial applications, and aerospace projects.
How to Choose Between Alloy Steel and Stainless Steel
Choosing between alloy steel and stainless steel really boils down to three factors: corrosion resistance, strength, and budget.
Any project that requires corrosion resistance would benefit from choosing stainless steel, since it is naturally better at resisting pitting and rust.
Structural parts that require high tensile strength should use alloy steel, since their values are typically better than stainless steel’s.
For projects that need to be low-cost or mass produced while keeping your costs low, alloy steel will probably be the better option. The raw material is more affordable, manufacturing is quicker, and machining is more affordable.
Conclusion
The choice between alloy steel and stainless steel can be simple once you have enough experience with both metals. Our experts at Rapid Axis are always here to help you make the decision for the next project. With extensive experience manufacturing both alloy steel and stainless steel, you can trust our team to handle your upcoming manufacturing needs.
We offer a wide range of finishing operations under one roof, so you can get the best results, regardless of which material you choose. Reach out today to get a free quote.
