If I had a dollar for every time this question arises, I would be retired on an island somewhere in the Pacific with an umbrella drink in my hand. The answer is simple though, all the above can be good but we must determine which is best for your operation. How do we do that you ask?
To determine which steel screen is best for your particular application, we must be knowledgeable of the different alloys of steel and what they are used for. This will help you in your entire operation. Here is a list of the typical types of steel we use in our industry:
A36: This is a low carbon steel (approx. 150 Brinell) used for structural uses. This steel is not heat treated nor hardened and can be formed easily. Most steel fabricators typically carry A36 steel in stock.
What is Brinell and why is it important? Good question! Brinell is simply the measurement of hardness of the steel. It is important to know the harder the steel, the more brittle it becomes. Our goal is to balance hardness (longer wear) against brittleness to decide our best solution for your particular grinding needs.
4140: The 4140 is a steel alloy that is heat treated and tempered. The Brinell level on this alloy is roughly 250-300. With this material being easily machined, 4140 is commonly used in most if not all shafts for your grinders and conveyors. This material is also more expensive than A36.
AR Plate: The “AR” stands for Abrasive Resistant Steel. This steel is harder than the above two alloys as it has more carbon. Carbon is the key. The more carbon, the harder the material.
Why not just buy the hardest material with the most carbon and use it for everything is a common question? The answer is that contrary to popular belief as steel gets harder, it becomes more brittle. There is a point to where it gets too brittle and will crack and break. Remember: When making screens, we must roll them / bump brake to a particular radius so the harder the material the more difficult it is to bend / roll. If the material gets too hard, the ends will crack and these cracks will continue to worsen causing structural failure to your grinder screen.
“AR” Plate comes in a variety of Brinell Hardiness’. Here are the common ones we use in our industry:
AR400: 360-440 BHN This material is commonly used for bed liners, wheel loader buckets, hopper liners, and is commonly used for grinder screens.
AR450: 430-480 BHN This material is slightly harder than AR400 and is also a popular material to make grinder screens.
AR500: 460-544 BHN Although this material is the hardest of the above 3 and will wear long, the steel is brittle and is not recommended for grinders. This material is extremely difficult to roll and will tear / rip due to its brittleness.
T1: This commonly known steel material is on the other spectrum as to hardness from the above. T1 has a Brinell hardness of 300. This material is heat treated and commonly used for screens.
HARDOX: This can be seen advertised everywhere and complicates the choice for many. Hardox is not an alloy of steel but a company in Sweden that makes a high quality AR plate. Hardox makes Hardox 400, Hardox 450, and Hardox 500 so the steel has the same basic characteristics as it counterpart AR Steel.
So what have we learned?? Use A36 for general steel fabrication, 4140 for machining, T1, AR400, AR450, Hardox 400, and Hardox 450 for screens. Now answer the question. What is the best material to use in manufacturing wood grinder screens?
The answer depends on the size of your wood grinder and the material you run through it. I recommend T1 steel for high horse power grinders (850 HP – 1200 HP) with 3” and larger openings if there are potential contaminants in the material. The screen will flex slightly as the contaminants bounce off of it and is the best scenario for a difficult application.
For high horsepower grinders being used as a secondary grinder, I would use either AR400 / Hardox 400 or AR450 / Hardox 450. This will wear noticeably longer than the T1 assuming there are no contaminants in the material. For smaller HP grinders, I recommend AR400 / Hardox 400 or AR450 / Hardox 450. To narrow this down even finer, when do I use AR400 / Hardox 400 and when use AR450 / Hardox 450? This decision is not easy to make. The higher the carbon content the more expensive the screen will cost. It all relies on the abrasiveness of your material. If your wood is extremely abrasive, then it is worth the higher expense for a higher carbon content screen. If your wood has average abrasiveness, then you will most likely select the least expensive screen which is the AR400 / Hardox 400 screen.
After being in this industry for nearly 40 years, most customers ask “How much for the screen?” and rarely ask what the screen is made of. Many customers call and say one type of screen is far superior to other screens on the market, but yet what are they comparing them to? In my career I have heard dozens of times that after market companies have sold Mild Steel screens representing them as AR and T1 screens. (It is hard to differentiate from the two without a trained eye.) Of course they were less money and did not last long. You can buy T1 and AR plate screens and depending on the mill it was made will determine which is better. A great deal of steel plate comes from China. Is this plate as consistent as steel plate made in Sweden or the US or Canada? The answer is NO.
GrinderCrusherScreen manufactures screens in T1, AR-400, AR450, and Hardox as well. We have facilities in the east coast, west coast, and in the Midwest to minimize the freight costs, and we look forward to answering any other questions when you need a grinder screen.