AR400 abrasion-resistant plate: hardness, properties, equivalents

AR400 is abrasion-resistant quenched and tempered plate at a nominal 400 HBW. No standard defines it. Hardness band, composition, bending and welding, and how to specify it properly.

Last updated 12 October 2026

What is AR400?

AR400 is abrasion-resistant quenched and tempered plate at a nominal hardness of 400 HBW — the default wear plate, and by volume the most used material in the class. It is roughly three to four times as resistant to sliding abrasion as the S355 structural plate around it, at perhaps twice to three times the price per tonne, which is why a 10 mm AR400 liner is bolted into a 12 mm S355 chute rather than the chute being made thicker.

The first thing to establish is that AR400 is not a grade. No EN or ASTM specification defines it; there is no composition table, no mechanical table and no test regime with independent backing. "AR400" is a trade description meaning *abrasion-resistant plate, about 400 Brinell*, and every mill's version is its own product: SSAB's Hardox 400, ThyssenKrupp's XAR 400, Dillinger's Dillidur 400, NLMK's Quard 400, and a dozen others. Two plates can both be correctly labelled AR400 and differ in analysis, guaranteed impact energy, minimum bend radius and thickness tolerance. The one standard that does apply is EN 10029 or ASTM A6, for thickness and flatness.

The second thing is what the hardness is for. Abrasive wear resistance tracks hardness only within a given microstructure, and that is precisely why wear plate is quenched and tempered martensite rather than simply high-carbon steel: the hardness has to come from a tough, uniform structure that will not spall when a rock hits it. The analysis is designed around hardenability in thickness — the chromium, nickel, molybdenum and boron are there so that a 40 mm plate transforms right through, not to add hardness of their own.

The third is why 400 and not 500. Every step up the hardness ladder costs formability and weldability. AR400 can still be press-brake bent to about 3 × thickness across the rolling direction, welded with ordinary low-hydrogen consumables at modest preheat, and plasma or laser cut without special precautions. AR500 can do none of those things comfortably. The right plate is usually the softest one that outlives the maintenance interval, because the fabrication penalty is paid once per part and the wear saving is paid once per plate change.

AR400 chemical composition

**These are indicative ceilings across the AR400-class products, not a specification.** No standard defines AR400 and no two producers' analyses are identical; the figures above bracket what the common brands declare. The composition exists to deliver hardenability in thickness, not hardness as such — the ~0.2 % carbon sets the achievable hardness, while the chromium, nickel, molybdenum and especially **boron** at a few thousandths of a per cent are there so a 40 mm plate transforms to martensite through its whole thickness in a water quench. Read the mill's own declared analysis from the certificate.

AR400 mechanical properties

Wear plate is **sold on hardness, not on strength**, and the tensile figures are a consequence rather than a requirement — most datasheets quote them as typical and some do not quote them at all. Two cautions follow. First, the hardness that matters is **through-thickness**, because a surface reading on a quenched plate flatters it. Second, several brands publish impact energy as a *typical* value; a typical value is not a requirement and cannot be inspected against, so if the part sees impact at low temperature the guarantee must appear on the certificate.

Impact toughness

AR400 requires a minimum Charpy V-notch energy of 27–45 J longitudinal (brand dependent) J at −40 °C °C (Not required by any standard, because no standard applies. Some producers guarantee a minimum at −40 °C on specified thicknesses, others publish typical values only, and the dedicated high-toughness variants (Hardox HiTuf, XAR HT and similar) are sold on exactly this property.). Impact energy is the most commonly over-claimed figure in a wear-plate quotation. Ask whether the number is guaranteed, at what temperature, in which orientation, and over which thickness range.

AR400 equivalent grades

Identical = same composition and mechanical limits within rounding. Near = one limit differs (e.g. carbon max or impact temperature). Functional = interchangeable for most uses after an engineering check. Full cross-reference for AR400 →

Old and superseded designations

Product forms and tolerance standards

Product forms: hot-rolled quenched and tempered plate, typically 3 to 80 mm, profile-cut parts, laser and plasma cut blanks, press-brake formed liners, chutes and buckets, wear strip, bar and cut-to-size blanks.

Dimensional tolerances: thickness and flatness: EN 10029 (class A, B or C as ordered) or ASTM A6 — the only part of a wear-plate order backed by an independent standard; flatness is normally ordered to a tighter class than EN 10029 normal, because quenched plate is harder to flatten and a wavy liner does not fit; hardness: the producer's own datasheet band, measured through thickness.

Key property values

AR400 hardness

Nominally 400 HBW, delivered in a band that varies with the producer — commonly 370–430 HBW, with some brands quoting 370–430 and others 380–430. Brinell is the reference scale for wear plate because the 10 mm ball averages over a large area and is insensitive to the local variation a Rockwell indent would pick up; 400 HBW corresponds to roughly 43 HRC. Insist on a through-thickness figure: hardness is measured below the surface, typically at a stated depth, because a surface reading on quenched plate reads high and tells you nothing about what the part will look like after the first few millimetres have worn away.

Hardness against wear life — and the limits of the relationship

In pure sliding abrasion against a harder abrasive, life rises roughly in proportion to hardness, so AR400 lasts about three to four times as long as S355 and AR450 adds perhaps 20–30 % over AR400. The relationship breaks down in three situations. Where the abrasive is softer than the plate — most sand against 400 HBW — extra hardness buys little, because the abrasive is being crushed rather than cutting. Where the wear is impact-dominated, as in a crusher liner or a rock box, toughness governs and a harder plate chips. And where the mechanism is gouging by large lumps, work-hardening austenitic manganese steel can outlast martensitic plate entirely. Matching the plate to the mechanism matters more than the hardness number.

Bending and forming

AR400 is the hardest wear plate that bends comfortably. Typical minimum inner bend radius is about 3 × thickness with the bend line transverse to the rolling direction, and 4–5 × thickness for a bend parallel to it — the difference is real and is the commonest cause of cracked liners. Allow a generous die opening, use a large punch radius, and check the cut edge before bending: a plasma- or laser-cut edge carries a hardened, notched zone that initiates cracks, and grinding it smooth is standard practice on a part that will be formed. Cold forming at below about 10 °C increases the cracking risk; warming the plate to room temperature is worth the delay. Roll forming to large radii is routine.

Welding

Readily weldable with low-hydrogen consumables, and this is another reason the 400 class is the default. Carbon equivalent is typically 0.40–0.50, so preheat of 75–100 °C is usual above about 20 mm and often unnecessary below it; check the producer's own table, which is thickness and combined-thickness based. Use a softer consumable than the plate — an ordinary 355–500 MPa class filler — because a hard weld in a tough plate cracks, and the weld is not the wearing surface. Keep heat input moderate: the heat-affected zone is tempered by welding and loses hardness over a few millimetres, which is unavoidable and is why a liner is bolted or plug welded rather than seam welded along its wearing face. No post-weld heat treatment: tempering the plate would remove the hardness it was bought for.

Cutting and machining

Plasma, laser and oxy-fuel cutting are all standard and are how most wear parts are made; abrasive waterjet is used where no heat-affected zone is acceptable. Expect a locally hardened cut edge of 1–3 mm, which should be ground off where the part will be bent or fatigue loaded. Machining is possible but slow — about 30–35 % relative to 1 % C free-cutting steel — with coated carbide, rigid set-ups and low speeds; drilling at 400 HBW needs cobalt or carbide drills and firm feed, and holes are better punched in the soft grade and plug-welded, or cut by waterjet, than drilled. Shearing is practical only in thin gauges and within the shear maker's hardness limit.

How to specify it instead of naming a brand

A requirement written as "Hardox 400 or equivalent" has no referent, because there is no document to be equivalent to. Specify the properties and several mills can quote the same thing: through-thickness hardness range (for example 370–430 HBW at a stated depth), guaranteed impact energy and temperature if the part sees impact, maximum carbon equivalent if it will be field welded, minimum inner bend radius at the ordered thickness if it will be formed, and thickness and flatness class to EN 10029 or ASTM A6. Those five lines are inspectable on arrival; a brand name is not.

Weldability

Weldable with all arc processes using low-hydrogen consumables and a filler softer than the plate — a hard weld in a tough plate cracks, and the weld seam is not where the wear happens. Carbon equivalent typically 0.40–0.50; preheat 75–100 °C above roughly 20 mm thickness, often none below, with the producer's combined-thickness table taking precedence. Keep interpass temperature and heat input moderate, and accept that the heat-affected zone will be softened by a few millimetres: that is inherent to welding a quenched plate and is why liners are plug welded or bolted rather than seam welded across a wearing face. Never post-weld heat treat — a stress-relief cycle tempers the plate and destroys the hardness. Weld-on wear buttons and overlays are the normal way to protect a weld line that must sit in the wear path.

Machining, forming and heat treatment

Machinable but slow and demanding: roughly 30–35 % relative to 1 % C free-cutting steel at 400 HBW. Coated carbide, rigid work holding, low cutting speeds and firm feeds; interrupted cuts on a cut edge are the usual tool-killer because of the hardened edge zone. Drilling needs cobalt HSS at best and carbide for production, with constant feed — dwelling work-hardens the hole bottom. Tapping is avoided; where a threaded fixing is needed, weld a boss on instead. For holes and profiles, thermal or waterjet cutting is the normal route, not machining. Grinding is straightforward with conventional wheels and is used to dress cut edges before forming.

Typical applications

• Dump truck and tipper bodies, bucket and loader liners
• Chutes, hoppers, bins and transfer points
• Conveyor skirts, scrapers and deflector plates
• Screen decks, grizzly bars and feeder pans
• Excavator bucket wear strips, cutting edges and side protectors
• Mixer and pug-mill liners, concrete plant wear parts
• Recycling and shredder housings, baler wear plates

Frequently asked questions

Related grades

Verified against ; EN 10029 (plate thickness and flatness tolerances); ASTM A6/A6M (general requirements for rolled plate); EN 10025-6 (S690QL comparison); ASTM A514/A514M (comparison). Last checked: October 2026.