Wear steel

By and |  January 14, 2014

Not all wear-resistant steel is the same, so find out exactly what you’re buying before placing your next purchase order.

Nearly every piece of equipment features wear-resistant steel. As a consumable item, the steel wears out. No one has the time to test 17 different wear plates head-to-head. Nor do they have the time to track which wear plates went where and how long they lasted.

Unfortunately, there is no industry standard for abrasion-resistant (AR) steel. Most people believe all AR400 is the same. But they definitely are not the same, and here is why: Few people understand AR steel because of inaccurate information.

The truth is that any number of steels can be compared in minutes using data found online or in the manufacturer’s printed material. With the information, users will never have to install underperforming wear plates again.

A quick education
Let’s be honest: You don’t think about the wear-resistant steel in your equipment until it completely wears out. But you must take immediate action when it does. So you either order the same steel as last time, or throw in whatever is laying around. As a last resort, you’ll look for something cheaper than last time.

Think about pizza for a moment. Looking at a pizza, you can see every ingredient. Whether piping hot, ready to bake or frozen, one glance tells if you will like the taste.

Why is this important? Different pizzas have different topping quantities. Just like pizza, the same elements are used to make steel wear plate. Creating a longer-lasting wear plate that also handles impact really depends on three critical steps.
■ Getting rid of sulfur and phosphorus.
■ Minimizing oxygen in the molten steel.
■ Having the proper balance of alloying elements to make the steel hard all the way through.

Sulfur and phosphorus make steel brittle. Blasting 1,200 cu. ft. per minute of oxygen into molten steel removes the phosphorus.

As an example, a total of 103 ships were lost in World War I. Many sank from a relatively minor bump with another ship. In another case, Titantic’s, the ship sank after striking an iceberg. After considerable research, it was discovered that the steel used to make the ships had high sulfur and phosphorus levels. This makes steel brittle.

If you have ever had a wear plate break, high sulfur levels are very likely the reason. The top plate has a representation of 0.002 percent sulfur. For comparison’s sake, the 0.002 percent equals one tablespoon of chopped onions. Too much sulfur in a wear plate is like a pizza with too many onions. It quickly becomes undesirable.

One critical detail to remember is that a sulfur level of 0.002 percent has 30 ft. lbs. of impact resistance, while sulfur at 0.004 percent has 10-15 ft. lbs. of resistance. That 0.002 percent more sulfur creates the risk of more cracking problems in every wear plate application. So examine sulfur content closely.

Both manganese and silicon help remove oxygen. They also add strength and are very inexpensive, so everyone uses them. But loading up on manganese and silicon only creates brittle steel. Manufacturers use silicon to add strength cheaply. But adding more than 0.3 percent silicon creates more problems than benefits. On our pizza, let’s let black olives represent silicon. Even a small percent change quickly becomes overpowering. Imagine mozzarella cheese represents manganese: overdosing on cheese in a pizza is just as unappealing as excess manganese in wear plate.

Many people in the aggregates industry are familiar with Hadfield manganese steel. It contains 12 to 14 percent or more manganese. At that level, the manganese can work-harden from repeated impact.

Target these levels
Ultra-low sulfur levels are critical, too. Wear plate having 0.004 percent sulfur has only half the impact resistance of steel with 0.002 percent sulfur. Also, if you don’t remove all the oxygen, the lowest you can get the sulfur level is 0.010 percent. To get all the oxygen out, primary deoxidizers, manganese and silicon are used. Aluminum eliminates the remaining oxygen. So if aluminum is listed, the oxygen is removed.

Look for manganese levels that are less than 1.25 percent, as well. The silicon level should be under 0.3 percent. And the manganese-to-silicon ratio should ideally be three-to-one. Manufacturers do not publish this figure, so divide the manganese by the silicon. Anything less than three-to-one is brittle.

Something else to remember is that all steelmakers list sulfur and phosphorus content as maximums. If other elements are listed at 1.0 percent max, you still don’t know what amounts you have. You might think you have 1.0 percent when, in fact, yours may contain 0.04 percent. One solution is to look for a specific range, such as nickel content between 0.5-0.85 percent.

The standard for at least one steelmaker is Brinell hardness, which is tested on a milled surface once per batch and every 40 tons. Tests are made for every variation of five-eighths of an inch in the thickness of plates from the same heat.

Wear-resistant steel is quenched and tempered plate-by-plate and one at a time. This means manufacturers only test one plate for hardness every 40 tons. Furthermore, this means they can test and certify a 1⁄4-in. plate at whatever hardness it is. Then, manufacturers will state that a 3/4-in. plate from the same batch is at the same hardness.

Considering this, it is likely your plate was never tested. So you cannot be sure what hardness you bought. Verify the hardness of your steel plate so you know what you’re buying.

For you, this means a 1/4-in. plate can be tested and certified at whatever hardness it is. Then, manufacturers will state that a 3/4-in. plate from the same batch is of the same hardness. It is likely your plate was never tested, so you cannot be certain what hardness you bought. Verify the hardness of your steel plate so you know what you buy.

Your payback in doing these checks is longer equipment life. You will seldom make a better investment in time.

Take note
Hadfield manganese steel contains 12 to 14 percent or more manganese. At that level, the manganese can work-harden from repeated impact.

Rich Fercy has more than 20 years experience in wear-resistant steels and specialty welding products. He owns WearAnswers.com and can be contacted at richfercy@gmail.com.

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