Cutting AR500 Steel With Plasma: Tips And Cautions

AR500 steel is considerably different from most other variations of steel or alloys, which is why its applications are also very specific, often limited to mining, production of heavy equipment, armor plates, shooting targets, material handling, hoppers, buckets, etc. When it comes to cutting AR500 steel, you should be ready to learn certain factors.

You can cut AR500 steel using a plasma cutter and a properly tuned table. The AR plate you’re cutting should be 3/8″ or 1/2″ thick. Set the amperage to 65 or 85 keeping the speed to 45 or 25 inches per minute respectively. Keep the “torch-to-work” distance as the manual suggests.

The job involves challenges which might set you off having a second thought even after making all the preparations. This guide is meant to help you handle those difficulties. Start with the properties of AR500 steel to find out how the process is not as simple as a regular plasma cutting job.

Let me explain the stuff in brief.

What Is AR500 Steel?

AR500 steel makes sense for people who deal with a specific type that is abrasion resistant. This ‘high-carbon steel alloy’ possesses exceptional Brinell hardness (500) and outstanding surface hardness (477-534 BHN). The high level of impact along with sliding abrasion resistance makes this type less malleable than most other alloys.

Cutting AR500 Steel With Plasma: Tips And Cautions

Is It Difficult Or Hard To Cut AR500 Steel?

An acceptable way to calculate how much pressure you can expect this steel to withstand is to measure its hardness against a square inch of an AR500 steel plate. I don’t think you would bother about the calculation because most of us wouldn’t either. Put as much as 11o tons of pressure or impact to test its strength. As far as I’ve learned, the steel won’t lose its structural integrity facing the specified pressure.

Stainless steel, mild steel, copper, and aluminum are some of the common materials that can be cut with standard plasma cutters. Here, you’ll be looking at neither an entry-level model nor an expensive unit with too many bells and whistles. Compared to the Brinell hardness of AR500 steel, those metals come with much lower numbers such as 15 for aluminum, 35 for copper, 120 for mild steel, and 200 for stainless steel.

Even T1 which is known for its abrasion and impact resistance is no match for AR500 with a Brinell hardness of 350. Although you might have heard about the varieties of AR steel in terms of hardness, 500 is the closest to what is top on the scale. That brings us to another factor – the thickness of the metal which may seem too much for a regular plasma cutter, I mean something most hobbyists use.

AR500 steel plates or sheets come in a variety of thicknesses, from 3/16 inch to 2 inches where the majority of targets are made out of 3/8-inch plates. Some applications, particularly heavy rifle ammunition, require 1/2-inch AR500 plates depending on preferred distances.

This kind of composition and so much hardness don’t come without some limitations, especially when you’re thinking of working or applying procedures like welding and cutting. Even though you may get away with much of the problems of hardness, you still have to struggle to keep the structural integrity of the metal intact.

Common Methods To Cut AR500 Steel

You can choose from the three most frequently used methods such as laser, water jet, and plasma where laser is considered the best way to go and plasma is the most affordable one.

However, none of these methods are without their drawbacks due to their impacts having high velocity that may leave deep holes or pitting, thereby weakening the steel. So, how can you cut AR500 steel using a plasma machine? Let’s get to the details.

Cutting AR500 Steel With Plasma

You won’t need a lot of tools or a lot of arrangements for this. Only a plasma cutter, a table, and a steel plate should be enough to start with. You might want a few more prepping tools, though. A plasma cutter with 65 amps or 85 amps in output current and duty cycle of at least 50% will be okay. Choose a plasma table accordingly.

Then, you need a software tool to follow the right nesting strategy to optimize the cuts. If you are familiar with a number of such tools, you already know which one works best. If you don’t know much, I recommend Fusion 360 which is a CAD/CAM software solution known for tons of features specific to machine tool programming, industrial design, and mechanical engineering.

Make sure the thickness of your AR500 plate doesn’t exceed one half of an inch. A good guess is 3/8 inch. You could pick something thicker, but I think that would only cause you inconvenience.

Now is the time to learn other settings such as amperage and speed.

You can choose a variety of settings, but I think 65 amps or 85 amps should be enough and the speed should be 45 inches per minute (IPM) for 65 amps and 25 IPM for 85 amps. As experts believe, one should stick around the specs used for cutting steel. In that case, you want to do everything by the book, I mean the user manual that came with your plasma cutter.

Don’t forget your gear. Since you’re cutting with a plasma system and not using a welding machine, choose the safety outfit that is appropriate. Now that you’ve got the process with its specs, you should focus on what comes next.

Should You Really Cut AR500 Steel With Plasma?

I think it is solely your discretion to use or not use a plasma system for the job. I can only provide you with the facts, so you can decide with a better understanding of each method.

As you start cutting AR500 steel or just about any metal alloy, heat will be generated regardless of the process you adopt. Heat affects the strength and hardness of the steel critically. The edges of the sheet or plate are annealed as they are heated using specific cutting temperatures. This creates an area known as the “heat-affected zone or HAZ” which is inevitable.

But you can try to apply heat in a way that the HAZ becomes small. More heat applied to the steel results in larger HAZ. The small amount of heat generated in a laser cutting process is the reason why it is a better choice than either water jet or plasma cutting.

A laser system produces a beam of energy that is precisely focused on the area that needs to be cut through. This way the cutting edge receives very little heat, thereby creating a small HAZ. I would say, minimal HAZ.

Water jet is another acceptable process where a highly consistent flow of water is required to prevent the heat from reaching an extreme temperature. But some problems like hydraulic pressure failure or temperature overheating and low water pressure are so common in this process that you want to be very cautious all the way. In addition, the process is much slower, which makes it less favorable than laser.

So, what is the catch to the method (plasma) in question? Plasma cutting is the most affordable of all these processes. However, heat being produced in excess weakens the steel and makes the other two methods more effective.

I won’t say it is the worst method, chances are very strong that the steel plate you’re cutting could be brittle as the excessive heat gets deposited into your metal plate and softens all of its edges. Needless to say, the HAZ that a plasma machine generates is larger than the one created by either laser or water jet. Cost-effectiveness is perhaps the key consideration for many following this process.

How To Overcome The Limitations?

While I am no expert as far as AR500 steel is concerned, I can offer you a few tips to help you minimize the negatives to some extent, if not completely.

Choosing the Material Thickness

Most plasma cutters allow the operators to cut up to 1-inch mild steel sheets and 3/4-inch stainless steel plates. With some powerful units, the thickness can be up to 2 inches, depending on the hardness of the material being cut. The thicker your steel plate is, the more edge roughness you’ll see. I think you should choose something between 3/4″ and 1″.

Minimizing the Dross

As most people tend to cut the steel maintaining an angled position rather than a perpendicular one to the metal surface, you really have not much to do about the dross created in the process. But you can see less dross by adjusting the cutting speed by the book and setting your “torch-to-work” distance properly. You can consult the operator/user manual to get the right specifics in this regard.

Final Thoughts

At this end, I’ll talk about one of the mistakes many plasma operators commit. Take a look at your gas delivery system before starting to cut. Inspect the system to see if there is any leak. Make sure the regulator is of the appropriate size and the gas lines are okay. Don’t go cheap on gas. Try to get high-quality gas.

Another important task is to inspect the table to know if it is equipped to cut at the speed specified in the manual. It may need tuning. If you cannot do it yourself, contact the manufacturer and ask for advice. Don’t start before getting the table speed right.

That is everything I had to tell you about cutting AR500 steel with a plasma cutter. Do more questions keep coming to your head? Send me a message, so I can write back with the answer.

Last Updated on December 11, 2020 by Gary Hargrave