What Is Wear-Resistant (Abrasion-Resistant) Steel?
Wear-resistant steel, often called abrasion-resistant or AR plate, is a quenched martensitic steel engineered to survive sliding and impact wear. It is used where ordinary alloy steel plate would be gouged away in weeks: excavator buckets, dump truck bodies, crusher liners, chute liners, and concrete mixer drums.
The key property is hardness, measured in Brinell (HBW). Higher hardness means better wear life but lower toughness and harder welding and forming. Grades are named by their nominal hardness: NM400, NM450, NM500 in the Chinese system; Hardox 400, 450, 500 from SSAB; and AR400, AR450, AR500 as generic names.
Grade Comparison: NM vs Hardox vs AR
| Grade | Nominal hardness (HBW) | Type | Equivalent names | Best for |
|---|---|---|---|---|
| NM400 | 360 to 430 | Through-hardened martensitic | Hardox 400, AR400, XAR400, EVERHARD 400 | Bucket liners, chute liners, general wear; best balance of wear, weldability, and formability |
| NM450 | 410 to 480 | Through-hardened martensitic | Hardox 450, AR450, XAR450 | Higher sliding wear with some impact; a middle ground |
| NM500 | 470 to 540 | Through-hardened martensitic | Hardox 500, AR500, XAR500, EVERHARD 500 | Maximum sliding wear, low impact; cutting edges, hopper liners |
| NM550 / NM600 | 530 and above | Very high hardness | Hardox 550 / 600, AR600 | Extreme sliding wear; very limited forming and welding |
Hardox is the global reference brand; Chinese NM grades meet similar hardness targets at a lower cost. The honest difference is consistency of through-hardness and toughness from batch to batch, which is exactly what a good MTC and inspection protect against.
Specify Hardness, Not Just a Name
The single most important rule: specify the hardness range and test method, not only the grade name. “NM500” from one mill can be 470 HBW and from another 540 HBW. Both pass the name, and the wear life differs. On the PO and the MTC, require:
- Nominal hardness in HBW with an allowed range (for example 470 to 540 HBW for NM500).
- Test method, normally Brinell HBW 10/3000. Do not confuse Brinell with Rockwell or Vickers; see our note on HB, HRC, and HV.
- Through-hardness, not only surface hardness. Ask for hardness at the surface and at the core. Good wear plate is uniform through the thickness; case-hardened or surface-only plate wears through fast.
- Heat number, chemistry, and mechanical properties on the MTC.
Choosing Between NM400, NM450, and NM500
Higher is not always better. The right grade is the lowest hardness that meets the wear life, because harder plate is harder to weld, bend, and cut.
- Sliding abrasion, low impact (hoppers, chutes, liners): NM500 or Hardox 500 for maximum life.
- Mixed sliding and impact (bucket sides, truck bodies): NM450 or Hardox 450 as a balance.
- High impact or heavy structural loading (loader edges, impact zones): NM400 or Hardox 400, or a tougher impact grade.
- Parts needing deep forming or heavy welding: drop to NM400 to reduce cracking risk.
Welding, Cutting, and Forming
Wear plate is workable, but it fights back harder than mild steel.
- Welding: use low-hydrogen filler and preheat according to thickness and hardness. NM500 needs more preheat than NM400. For non-structural joints an under-matched filler is acceptable; for loaded joints match the strength.
- Cutting: plasma and laser are clean; oxy-fuel works but softens a thin heat-affected zone at the cut edge. Choose the process by part requirement, as with laser, plasma, or waterjet cutting.
- Forming: cold bend with a generous radius (typically several times the thickness, more for NM500), bend across the rolling direction, and allow for springback.
- Surface: specify whether the mill scale or decarburized layer must be removed before delivery. A soft surface layer reads low on a portable hardness test and misleads your QA.
Thickness Tolerance and Inspection
Wear plate is sold by weight and thickness; verify plate thickness tolerance on receipt, because under-gauge plate fails early and over-gauge plate wastes money. Confirm the dimensions and weight with the steel weight calculation guide, and run a pre-shipment inspection that re-checks Brinell hardness against the MTC.
Cost, Lead Time, and Next Step
NM500 costs more than NM450, which costs more than NM400. Hardox carries a brand premium over Chinese NM at similar hardness. For cost-sensitive, high-volume wear parts, NM grades are usually the better buy; for projects needing a proven through-hardness guarantee, Hardox. Lead time depends on thickness and quantity.
To compare accurately, use our quote spec template (grade, hardness range, size, quantity, incoterm) and request a quote. We will confirm the hardness range, through-hardness, MTC, and lead time against your specification.