Mild Carbon Steel vs. AR Steel vs. Stainless Steel

The good thing about customizable process flow systems for bulk material handling is the freedom to make sure the equipment is a perfect fit.

All steel containing carbon as the main alloying element is carbon steel, but the amount of carbon present dictates the type of steel and its properties. Here, we break down the differences between mild steel, medium carbon steel, and high carbon steel.

Mild steel, also known as “low-carbon steel,” is the most common form of steel for many reasons. It costs less while providing the material properties needed for most industrial applications. Mild steel contains approximately 0.05–0.25% carbon making it malleable and ductile. While mild steel has a lower tensile strength than other carbon steel types, it is more pliable and easier to form. You can also harden mild steel with various treatment processes. Mild steel is machinable and weldable, which aids in its usefulness for most applications.

Common uses of mild steel include:

• Building construction
• Pipelines
• Automobile manufacturing
• Wiring
• And more

Medium-carbon steel has approximately 0.3–0.6% carbon content. Mild-carbon steel may be heat-treated by austenitizing, quenching, and then tempering to improve its mechanical properties. It’s most often utilized in a tempered condition, having microstructures of tempered martensite. Medium-carbon steel balances ductility and strength. This grade of steel is primarily used for applications that call for a combination of high strength and wear resistance, including:

• machine components
• gears
• axles
• forgings

High-carbon steel has approximately 0.60 to 1.00% carbon content. High-carbon steel almost always used in a tempered condition and, making it wear-resistant and capable of holding a sharp cutting edge. This makes it useful for applications such as knives, hammers, and other hand tools.

High-carbon steel’s hardness is higher than other steel grades, but that comes with a price when it comes to ductility. The higher the carbon content in steel, the less ductile it is. It is also typically much higher in price compared to mild steel.

The tricky part is figuring out the perfect fit.

With so many options, it gets overwhelming if you aren’t an expert. It’s like standing in the toothpaste aisle deciding between hundreds of brands.

Let’s make it simpler and look at one aspect of the decision process:

Should you use mild carbon steel, abrasion-resistant (AR) steel or a form of stainless steel for your gates, valves and diverters?

Mild Carbon Steel: Carbon steel has a higher carbon content (duh) – around 0.05 to .25 percent of its weight. The upside of mild carbon steel is it’s stronger and harder than other forms of steel. This comes in handy if you’re dealing with mild to moderately abrasive materials or high temperatures.

However, mild carbon steel is more susceptible to rusting and corrosion if exposed to heavy moisture. It’s strength and hardness also mean it’s less malleable than other steels – making it more likely to crack when under extreme stress.

Mild carbon steel is a great choice if you handle dry and non-corrosive materials (such as grains, rice, frac sand, etc.) and the surrounding area of your plant doesn’t have a lot of moisture

For example, mild carbon steel is a good choice if you run a rice plant in California or a grains facility in Colorado.

Abrasion-resistant steel: Abrasion-resistant steel is a high-carbon steel that’s been hardened. AR steels feature the strength from adding carbon along with a resistance to oxidization from added alloys.

This best-of-both-worlds combination results in a steel that is somewhat in the middle: Not quite as strong as carbon steel but better resistance to rusting. Not quite as resistant to rusting as stainless steel, but also stronger and harder.

Well, on the Brinell scale – which measures the hardness of steel, with the higher the number meaning the harder it is – mild carbon (130-160BHN) and stainless steel (160-200BHN) are relatively similar. AR steel tends to come in between 235-550BHN.

AR steels are a great choice to build a gate, valve or diverter if you deal with high abrasive, low corrosive materials.

This could be a solid option if, for example, you run a quarry in Indiana or handle cement in Minnesota.

Stainless steel’s strengths and weaknesses are somewhat a mirror image of carbon steel.

It doesn’t rust because it’s protected against the oxidation process because it contains at least 10.5% of chromium. Therefore, the outer layer of chromium protects it against rusting. However, it’s not as strong as carbon steel.

(Quick science lesson: oxidation is a chemical transformation when the steel changes its properties when it’s exposed to oxygen, causing it to rust.)

Stainless steel is a great choice if the material you handle is moist or corrosive with low abrasive properties (such wet fly ash, gravel, fertilizer, etc.) and/or the surrounding area of your plant could have a lot of moisture.

For example, it’s a good option if you run a fertilizer plant in Mississippi or handle petroleum coke in a wet outdoor environment like Oregon.

But the most important thing…

No matter the steel, find a conveyor system manufacturer that works hand-in-hand with you throughout the process. A knowledgeable and experienced partner could be a major influence in purchasing the perfect gate, valve and diverter.

SunnySteel understands that one-size-fits-all is a recipe for disaster. That’s why we make our equipment custom-ordered, only after we understand the needs of your facility. There are a lot of factors that make up the perfect fit for your specific plant.

Let us help you find it.