Mining Wear Parts: AR Plate vs Hadfield Manganese Steel

Two wear mechanisms

Wear parts fail by sliding/grinding abrasion (ore scraping across a surface) or by impact abrasion (rock striking and crushing against it). The two dominant steel families each solve one problem well.

AR / NM plate: hard from the start

Abrasion-resistant plate (NM360–NM550 in the GB system, AR400–AR500 and equivalents elsewhere) is low-alloy steel quenched to a through-hardness of roughly 360–550 HBW, delivered ready to cut, weld and bolt in. It is the default for:

• Excavator bucket skins and cutting-edge backing plates
• Truck beds, chute and hopper liners
• Conveyor and transfer-point wear plates

Wear life scales broadly with hardness for sliding duty, but so do fabrication demands: higher grades need controlled cutting, drilling and weld procedures, and forming radii grow with hardness and thickness.

Hadfield Mn13: soft until struck

Hadfield steel (Mn13, GX120Mn12, ~11–14% Mn, ~1.0–1.4% C) is austenitic and delivered solution-annealed at only ~200 HB — seemingly soft. Under impact or high compressive stress its surface work-hardens to 500 HB and above while the core stays ductile. It dominates where blows are heavy:

• Crusher jaws, mantles, concaves and hammer mill parts
• Rail frogs and crossings
• Shot-blast cabinet liners

The logic cuts both ways: without impact, Mn13 never hardens and wears rapidly under pure sliding. Fitting it to low-impact chute liners is the classic misapplication.

Choosing

Duty	Choice
Sliding ore, moderate impact, fabricated liners/buckets	AR / NM plate
Crushing, repeated heavy impact, cast shapes	Hadfield Mn13
Impact present but part is a welded plate structure	AR plate, heavier gauge, or hardfaced plate

Fabrication notes differ too: AR plate hates excessive heat input on welding; Hadfield must be kept cool (it embrittles with prolonged heating in the few-hundred-°C range) and is welded with austenitic consumables. Hardfacing overlays complement both, adding a very hard sacrificial skin where wear concentrates.

Choosing within the AR family

Higher hardness is not automatically better. NM360/AR400-class plate gives the best combination of weldability, formability and toughness, and is the rational default for buckets and liners that also see dropped-rock impact. The 500-class grades roughly maximise sliding wear life but are less forgiving: minimum bend radii are larger, low-temperature toughness needs checking for cold-climate service, and severe point impact can crack rather than dent them. Specifying plate by hardness grade + thickness + impact requirement (winter mines order Charpy-tested plate) avoids the common error of treating AR500 as a straight upgrade over AR400.

Hardfacing as a third option

For both families, welded overlay (hardfacing) plate — a mild or AR base with a chromium-carbide or complex-carbide layer — serves extreme sliding abrasion where neither base steel suffices, at the cost of no formability and a characteristic crackled surface. It is a lining material, not a structural one, and is normally bolted or plug-welded over a supporting structure.