This question has come up several times during customer calls, and honestly, I understand why. From the outside, different steel products can often look very similar, making it difficult to know exactly what material you are actually getting.

Today I want to focus on that topic and break down some of the key differences in the steel commonly used for manure spreader paddles and other agricultural wear parts.

When replacing manure spreader paddles or other wear components, material selection plays a major role in long-term performance and service life.

Two common materials used in fabrication and wear components are standard A36/CQ mild steel and AR400 abrasion-resistant steel. While they may appear similar visually, they are designed for very different applications.

What is A36 / CQ Mild Steel?

A36 steel, commonly referred to as mild steel or commercial quality (CQ) steel, is one of the most commonly used steels in general fabrication.

It is widely used because it is:
- Cost effective and generally cheap to produce
- Easy to weld
- Easy to machine
- Easy to form and fabricate

Mild steel is commonly found in:
- Structural components
- Frames and brackets
- General fabrication
- Lower wear applications

Because of its softer composition, A36 steel is easier on tooling and allows for faster machining and fabrication compared to hardened wear plate materials.

However, mild steel is not specifically designed for high-abrasion environments.

What is AR400 Steel?

AR400 is a specially formulated heat-treated abrasion-resistant steel designed specifically for high-wear applications.

Compared to standard mild steel, AR400 offers:
- Higher surface hardness
- Better abrasion resistance
- Improved wear life
- Increased durability in aggressive environments

Typical AR400 hardness ranges around 360–440 Brinell hardness, while mild steel is considerably softer, typically around 100–180 Brinell hardness. In Rockwell C hardness, AR400 commonly falls within approximately the 30s to mid 40s HRC range, while mild steel is substantially softer and is more commonly measured on lower hardness scales.

This increased hardness allows AR400 to perform well in applications involving:
- Constant abrasion
- Material erosion
- Scraping and impact
- Heavy contact wear

AR400 is commonly used for:
- Manure spreader paddles
- Feed mixer wear parts
- Cutting edges
- Plow blades
- Excavator buckets
- Loader and skid steer wear components

Wear Resistance Differences

One of the biggest differences between AR400 and mild steel is wear resistance.

In agricultural applications involving manure, silage, gravel, bedding, sand, or feed, standard mild steel can wear relatively quickly over time.

AR400 is specifically engineered for these types of demanding conditions and generally provides:
- Longer service life
- Reduced downtime
- Fewer part replacements
- Improved long-term durability

For operators running equipment regularly in abrasive environments, the increased wear life can often justify the additional upfront material cost.

Hardness Testing and Real-World Material Comparison

One common way to compare wear plate materials is through hardness testing. While hardness alone does not determine overall material quality, it can provide a general indication of a material’s abrasion resistance and wear characteristics.

The photos below show example hardness testing being performed on both abrasion-resistant AR400 plate steel and standard mild steel materials, see below of Part A on the left, which is the AR400 plate and Part B on the right which is mild steel.

In many cases, AR400 wear plate will test substantially harder than conventional mild steel. This increased hardness is one of the main reasons AR400 performs better in demanding high-abrasion agricultural and heavy equipment environments.

 

Before we begin the test here is the test block showing what its checking, this is a picture of a hardened test block that verifies the machines accuracy. This guage/test block is hardened to RC 56-58.

Below is the reading of the machine coming in at RC56, within spec.

Below is the Rockwell C scale test of Part B the mild steel paddle coming in at RC 3 on the scale. Standard mild steel typically tests substantially softer than abrasion-resistant wear plate materials.

Here is the test of Part A, the AR400 plate, coming in at RC 33 on the scale.

When evaluating wear parts, it is important to understand that not all steels marketed similarly will necessarily perform the same in real-world applications. Material chemistry, heat treatment, and manufacturing processes can all affect final wear performance and durability.

Fabrication and Machining Differences

While AR400 offers major advantages in durability, it can also be more difficult to machine and fabricate compared to mild steel.

AR400 commonly requires:
- Slower cutting speeds
- Higher quality tooling
- More care during welding
- Additional attention during forming and machining

Many AR400 components today are commonly laser cut or plasma cut due to the material’s hardness.

By comparison, mild steel is easier to:
- Drill
- Machine
- Form
- Weld

This is one reason mild steel remains popular for structural and general fabrication applications where extreme abrasion resistance is not required.

Not All “AR400” Is the Same

One important thing many buyers may not realize is that not all wear plate materials are manufactured equally.

Even when products appear visually similar, the actual material properties can vary significantly depending on the steel source, chemistry, heat treatment, and manufacturing process.

When comparing wear parts, it is worth asking:
- Is the material truly abrasion-resistant steel?
- Is the plate properly heat treated?
- Is the hardness consistent through the material?
- Is the steel intended specifically for high-wear applications?

Material selection can significantly affect:
- Wear life
- Durability
- Impact resistance
- Long-term performance

In many applications, labor and downtime often become more expensive than the replacement part itself. Using the correct material can help reduce premature wear and unnecessary equipment downtime.

Can You Tell the Difference Between AR400 and Mild Steel?

In some cases, experienced fabricators or operators may notice differences between abrasion-resistant steel and standard mild steel during fabrication or repair work.

For example:

• AR400 generally feels harder during grinding or drilling
• Mild steel typically machines and cuts easier
• Abrasion-resistant plate may produce different grinding characteristics compared to standard mild steel

Some operators also compare wear patterns over time, especially in high-abrasion applications where mild steel may wear noticeably faster.

However, appearance alone is not always enough to accurately identify material type.

When purchasing wear parts, it is always worth asking the supplier:

• What material is being used?
• Is the steel heat treated?
• Is the material intended for abrasion-resistant applications?

Understanding the material being used can help ensure the part is appropriate for the intended environment and workload.

Final Thoughts

Both AR400 and A36/CQ steel have their place depending on the application.

For general fabrication and lower-wear applications, mild steel remains a practical and economical option.

For high-wear agricultural and heavy equipment applications where abrasion resistance and long-term durability are important, AR400 offers a significant performance advantage.

Here at NWIA Parts, we understand the demanding conditions agricultural equipment faces and the importance of using the right material for the job. That is why we use abrasion-resistant AR400 plate steel for our manure spreader paddles rather than lower-grade mild steel alternatives that may appear similar visually but do not provide the same long-term durability and wear resistance.

We believe using the proper material is critical to delivering a product capable of standing up to the demands of real-world agricultural use. Check out our products and see what we have to offer.

As always, if you want to talk shop, have questions, need help identifying parts, or just have a great idea to discuss, feel free to give us a call. We are always happy to help.

Have a great day.