Abrasion-resistant (AR) steel is a type of high-carbon alloy steel. The alloys in it make it formable and weather resistant, and the amount of carbon in the steel can affect the hardness when heat treated. When reading these types of steel grades, such as AR400 and AR500, it is important to note that the number that the number following the letters AR represents the hardness range of the steel. AR steel is often used in applications where the material will experience failure via wear and tear or abrasions over time.
As mentioned earlier, the number in the AR steel description represents the hardness range of the steel, a number which is based on the Brinell Scale. The Brinell Scale characterizes hardness of steel through the scale of penetration of an indenter loaded on a material test-piece. AR400 steel falls between 360 BHN and 440 BHN, whereas AR500 steel falls somewhere between 477 BHN and 550 BHN on the Brinell Scale. Though these two grades have similarities, they key difference between the two is a characteristic called impact resistance.
Impact resistance describes the energy required to break a piece of test material in two pieces or more. AR400 steel is known to have a high impact resistance, so it is used in applications like in the bed of a dump truck. The bed of the dump truck will experience impacts when things are loaded in and out of the bed, so it is important you use a steel like AR400 that has a high impact resistance and will not shatter over time. Comparatively, AR500 steel is known to have a high abrasion resistance. This results in AR500 steel being used for applications where the material will be exposed to wear and tear from materials rubbing against them rather than being dropped onto them such as in AR400 applications. It is important to be aware of the physical and chemical properties of the materials you use in, and it is equally important to know the difference between those properties amongst grades. This will ensure you select the best material for the given objective at hand.