Friday, January 6, 2012

Hey Grinder Guy, what kind of steel should I buy?

Original Post June 1, 2011
This question comes up all the time, mostly when purchasing screens for wood grinders, but unless you work for a steel company, how do you know the difference?
The steel from each manufacturer is comprised of different steels and alloys to create the chosen strength, hardness and impact and wear resistance required. Each manufacturer uses its own proprietary blend and heat treats and tempers differently. Each has their premium grade, trademark name, overlays, etc. Using ASTM specifications or the Brinell scale, comparing these products may be a little easier, but not always. The American Society for Testing and Materials uses standard specifications to classify steel. The Brinell scale measures hardness of steel and the rating numbers increase the harder the material. Harder is not always better though. The harder the material, the more brittle and less flex steel will have. A typical analysis available from your steel supplier will supply these values so you can compare products. We can help narrow the choices a bit.
The basics are:
Common Steel- Used for framing, constructing, etc. Common quality falls into this category, and then increases with strength. Which regular grade you need is based upon design and load factors.  Say your operator is texting and loading and drives right into the side of your feed hopper. Along with hiring a new operator, what will you be purchasing to reconstruct your feed hopper? Here are a few examples of common steel:
·         A36- Standard, Low Carbon, No Heat Treat. Brinell hardness is approximately 150. Many framing and structural uses that are based on design factors.
·         4140- Heat treated and tempered. Brinell Rating of 250-300. Used mostly for machining parts, molds, etc.
·         T1- Heat Treated for strength and hardness. Brinell rating of 300. Used in mining, farming and construction equipment industry. Has a good combination of strength and wear.
Abrasion Resistant Steel- Used for Wheel Loader Buckets, Screens, Hopper floors, grinding chamber liners, thus the prefix, AR- Abrasion Resistant. Here are some examples:
·         AR400- Common abrasion resistant plate. Brinell rating of 400. Used in all high wear applications, wear plates, cutting edges.
·         AR500- Harder abrasion resistant plate. Brinell rating of 500. Used in all higher wear applications for longer wear life
·         Hardox®- Most common “Name Brand” in the industry. Brinell rating of 400- 600 or more. Used in all high wear applications, grinder screens, dump truck beds and a host of others.
So how do you choose? Ask your local steel or wear parts salesperson for assistance. Hey have much more experience and the good ones will not just sell you the most expensive type. For example, Lori Rheinberger, of, suggests using an abrasion resistant plate for grinder screens with hole sizes below three inches. For screens with larger holes, she suggests using a T1 steel because it has a little more flexibility and strength. But as she said, some customers know their material and equipment and request AR Plate or T1 exclusively.
What is the difference in cost? For this example, we will use Hardox® only because it is the most recognized name in Abrasion Resistant Steel and we will use $500 just for a nominal number. If you use a Hardox® 400, which has a Brinell rating of 400, and switch to Hardox® 450, which has a Brinell rating of 450, for an extra $500, what kind of extra life did you get in hours, yards or tons for the $500 and increase of 50 on the Brinell scale? Then you could estimate the increase if you were to purchase a Hardox® 500 or 550 or 600. You could also do the reverse, and see what you could save by downgrading steel. You could save up to half the cost and get similar wear life. Try half a new cutting edge for your wheel loader bucket using an AR400. Then on the other half, try a T1 for example. Each will wear differently depending on your applications and materials, but they do not cost the same. See which is more economical.
Hard facing, welding and forming are possible with some steels, but each manufacturer has its own specific procedure so as to not lose quality. Most screens and buckets that are welded or hard surfaced end up cracking and falling apart because too much heat has been put to them in the process and they become too brittle. Hard facing a couple inches at a time, then moving to another area and hard facing for a couple inches and repeat is common welding practice.
Remember, each site and material is different and they all vary greatly. What works best with your equipment on your material? With steel prices constantly increasing, find the most cost efficient steel you can get based on cost of wear life.
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