The Great Hardness Myth: Just How Hard Is Your Wear Plate?
Creating wear resistant steel that achieves high test hardness values is easy. Super simple in fact.
All you have to do is to add more Carbon and the steel registers harder test readings.
But does higher hardness steel automatically deliver longer life in your applications? Not necessarily.
Looking at any manufacturer’s published data shows you the claimed hardness of their wear plate.
Here Is A Big Question To Look For In Their Data When Evaluating Wear Resistant Steel: How Frequently Do They Test The Steel Hardness?
The name QT Plus ® refers to the Quench and Temper process that delivers outstanding hardness and wear life.
JADCO insists on precise quality control for QT Plus ® at the steel mill in PA. This means every single plate is tested to make certain that the hardness readings are in specific tolerance range. This guarantees the customer get exactly what we promise.
This is often different than other abrasion resistant steel
When steel is made, they melt scrap steel into a ‘heat’ at the electric arc furnace. In steel mill terms a ‘heat’ is like a ‘batch’ for a baker making cookies. The average heat in our mill is 160 tons.
For a comparison, let’s look at our standard 96” x 288” plate of QT Plus ®. The 1/4” plate weighs 1960 pounds or close to one ton. When you melt 160 tons at a time, the molten steel is poured out, and cast into slabs. After cooling, the slabs are rolled to the requested dimensions of thickness, length and width.
While there are ZERO standards for wear resistant steel, ASTM requires property measurements are taken once every heat, and each 40 tons of steel within that heat.
(Note: ASTM International, formerly known as the American Society for Testing and Materials (ASTM), is a globally recognized leader in the development and delivery of international voluntary consensus standards.)
After rolling to the correct size ordered, the steel goes through the heat treat process. This is done by heating the steel plate to 1650°F and is then quenched (lowered) into a water tank. While the plate at this point will be about 600 BHN; it will not tolerate impact. That is why quality wear resistant steel plates are not just quenched, but tempered as well.
Tempering means they re-heat the steel up to a specific temperature between 400°F and 500°F and hold it for a period of time (about an hour) before allowing it to slowly air cool. This quench and temper process results in the optimal balance of hardness and toughness in the steel.THIS TEMPERING STEP IS CRITICAL FOR ANY ALLOY WEAR PLATE TO BE ABLE TO WITHSTAND IMPACT AND NOT CRACK IN USE.
NOTE: mild steel is not heat treated; does not require quenching and tempering, and therefore its properties and performance do not match that of abrasion resistant steel.
Here is a bit of critical information not included in our competitors data:EACH PLATE IS QUENCH AND TEMPERED ONE SINGLE PLATE AT A TIME.
Remember our ¼” plate weighs about one ton. If you take just one hardness reading for every 40 tons, you have no idea of the hardness results are on the other 39 plates. Depending on the heat treatment process, the hardness can vary anywhere between 200 BHN to 600 BHN.
In the past you may have had one wear plate application last for several years. When you replaced it with the same type of AR steel did it fail after only a couple of months? Chances are it was not quenched and tempered, or perhaps it was not precisely quenched and tempered like our steel and was the cause of why you experienced a breakdown.
Since each steel plate is individually heat treated, JADCO tests every single plate to make certain each one meets our strict quality standards. It is the heat treat process that determines the hardness of the steel wear plate.LET’S PEEK INTO THE FINE PRINT, AND DISCOVER THE DIRTY LITTLE SECRETS HIDDEN IN PLAIN SIGHT.
So you didn’t know this information existed. Chances are no one ever brought this to your attention, and it is not your fault.Examining the fine print in the Hardox® 450 literature published online, we see this notice listed under Mechanical Properties:
Footnote 1): Brinell hardness, HBW, according to EN ISO 6506-1, on a milled surface 0.5 – 3 mm below surface. At least one test specimen per heat and 40 tons. (This matches the ASTM specifications for testing frequency.)
Footnote 2): Hardness test is not performed or guaranteed for Hardox 450 cold rolled material. The hardness is a conversion from the tensile strength.
The nominal thickness of supplied plates will not deviate more than +/- 15 mm from the thickness of the test specimen used for hardness testing.
Here Is What Footnote 2) Means To You:
1. They do not do any hardness testing on their cold rolled Hardox 450 steel. Rather, they use a math formula; and have not physically tested the hardness on any of these plates.
2. As long as the thickness of your plate doesn’t exceed the plate they hardness tested by over the 15 mm (0.59055”) thickness difference; they can claim both plates have the same hardness. The thinner a plate is, the easier it is to have a higher overall hardness test values closer to the center of the plate thickness.
This means they test the hardness on a ¼” plate. Since a ¾” plate is also from the same heat falls within the allowed thickness variation; they also certify a ¾” plate as having the same hardness. The difference between the hardness at the center of the plate thickness comparing a ¼” and a ¾” plate can vary significantly.
If you buy a ½” plate, there is no guarantee they tested your specific plate out of the entire heat.WE MAKE CERTAIN YOU KNOW WHAT YOU ARE GETTING FROM JADCO.
We believe you deserve to know exactly what the hardness is of every single plate you invest in with JADCO.
We can guarantee the hardness of your steel because the detailed information from the steel mill; follows every single every project through where every plate is used.