Hardox is SSAB’s trademarked abrasion-resistant wear plate, chosen because it is hard and resists being worn away. S355 is a structural steel grade to BS EN 10025-2, chosen because it has a guaranteed minimum yield strength and toughness that a structural engineer can design against. They are answers to two different questions, and mixing them up on a drawing causes real problems: either a wear application in the wrong (soft) steel, or a load-bearing member specified in a grade the design code was never written to cover.
What Hardox actually is
Hardox is a brand name, not a generic term. SSAB supplies it as a quenched steel plate, delivered hard and tough straight from the mill. The grades run from around 370 to over 500 Brinell hardness (HBW), with Hardox 400, 450 and 500 covering most of what turns up on UK fabrication drawings. The trade-off is that Hardox is a wear-resistant material first, chosen to survive abrasion and impact, not to be load-rated the way a structural section is.
What S355 actually is
S355 is one of the common structural carbon steel grades made to BS EN 10025-2, the standard our own guide to S275 vs S355 covers in more detail. The number is a guaranteed minimum yield strength of 355 N/mm2, tested and certified, which is what lets a structural engineer calculate how much load a beam, column or frame member can carry. It also comes in impact sub-grades (JR, J0, J2, K2), covered in our S355JR vs S355J0 vs S355J2 guide, describing toughness at different service temperatures rather than yield strength.
The property table
| Material | What it is specified for | Hardness | Yield strength | Standard | Typical uses |
|---|---|---|---|---|---|
| S355 | Guaranteed structural strength and toughness | Around 150 to 200 HBW (not a specified property) | 355 N/mm2 guaranteed minimum (up to 16 mm) | BS EN 10025-2 | Beams, columns, portal frames, bridges, mezzanines |
| Hardox 400 | Abrasion resistance | 370 to 430 HBW | Around 1,000 N/mm2 typical (SSAB datasheet, not guaranteed) | SSAB proprietary | Buckets, chutes, liners, general wear parts |
| Hardox 450 | Higher abrasion resistance | 425 to 475 HBW | Around 1,250 N/mm2 typical | SSAB proprietary | Tipper and trailer bodies, hoppers |
| Hardox 500 | Severe abrasion resistance | 470 to 530 HBW | Around 1,400 N/mm2 typical | SSAB proprietary | Crusher liners, quarry and recycling equipment |
The typical yield figures for Hardox come from SSAB’s published datasheets: they describe what the material usually does, not a certified minimum the way S355’s 355 N/mm2 is.
Why “harder” does not mean “better for a beam”
It is tempting to assume Hardox, with a typical yield several times higher than S355, must simply be the better steel. A beam does not fail because it is not hard enough. It has to meet three things at once: a guaranteed minimum yield the engineer can design against, proven toughness so it bends rather than fractures under overload, and stiffness, governed by the material’s Young’s modulus. Stiffness is essentially identical across all steels, Hardox included, at roughly 210,000 N/mm2, so the one property that actually controls beam deflection does not improve with hardness at all. What Hardox trades away is the certified, code-recognised yield guarantee that Eurocode 3 and BS EN 1090 are built around, and that gap is why it sits outside structural specifications.
Where each one belongs, and why you cannot just swap them
Structural members have to be specified in a grade the design code actually covers. Under Eurocode 3, that means BS EN 10025 grades such as S355 or S275, unless a structural engineer specifically justifies otherwise in writing. Hardox is not on that list: it was never developed as a structural design material, so there are no Eurocode 3 design values published for it, and BS EN 1090 execution assumes the grades the standard was written around. That matters because a beam calculation, a connection design and a Building Control sign-off all depend on the material being a recognised structural grade.
Wear plate, by contrast, is normally a sacrificial or protective layer bolted or welded onto a structure, not the structure itself. A tipper body has a structural chassis underneath the Hardox liner. A hopper has a structural steel frame with Hardox facing the material flow. The wear plate takes the abrasion so the frame beneath it does not have to.
Welding the two also differs in practice. S355 welding is routine fabrication work. Hardox is weldable, but its hardness means the fabricator has to follow SSAB’s guidance on preheat and controlled heat input, because getting that wrong risks cracking in the heat-affected zone. It is a different discipline to standard structural welding, not an extension of it.
What this means for your job
If a drawing calls for wear plate on part of a structure, flag it early rather than assuming any strong-sounding steel will do. As a CE approved fabricator working to BS EN 1090 with our own in-house design and Banbury workshop, we handle the structural side (beams, columns and frames in S355 or S275) as part of our normal structural steelwork and industrial steelwork work. Wear plate itself sits with a specialist supplier, so send the drawing over and we will tell you plainly what we can fabricate and what belongs with someone else. If an existing structure needs sections replaced or reinforced, that is steel repairs and refurbishment territory, and the same rule applies: the replacement matches the design grade, not whatever happens to be hardest.
For more on how the standard structural grades compare, see S235 vs S275 vs S355 and mild steel vs stainless steel if corrosion resistance, rather than abrasion resistance, is the actual concern on your job.
For the underlying material data, SSAB publishes the full Hardox property range and the Steel Construction Institute’s steelconstruction.info covers S355 and the other structural grades in more depth.
Frequently asked questions
Can Hardox be used instead of S355 in a structural frame?
Not without a structural engineer specifically justifying it. Hardox is not one of the BS EN 10025 structural grades that Eurocode 3 design values and BS EN 1090 execution assume, so it has no place in a beam, column or portal frame specification by default. It is a wear-resistant plate, not a design-code structural material.
Is Hardox stronger than S355?
Hardox is harder than S355, and SSAB publishes typical yield figures for Hardox that are well above S355’s guaranteed minimum of 355 N/mm2. But hardness and typical yield are not the same guarantee a structural engineer needs. S355’s 355 N/mm2 is a certified minimum under BS EN 10025-2; Hardox’s figures are typical values from SSAB’s own datasheets, not a structural design minimum.
Why can’t you just weld Hardox into a beam if it is so hard?
Two reasons. First, a beam is sized against a guaranteed minimum yield, toughness and stiffness under Eurocode 3, and Hardox does not carry that certification. Second, high hardness changes how the plate behaves under heat: Hardox is weldable, but the fabricator has to follow SSAB’s preheat and heat-input guidance to avoid cracking, which is a different process to routine S355 welding.
Where does Hardox actually get used?
On the parts of a structure or a machine that wear away, not the parts that carry the load. Typical uses are tipper and trailer bodies, excavator buckets, chutes, hoppers, crusher liners, and other equipment in quarrying and recycling where abrasion is the enemy. The load-bearing frame underneath is still specified in a structural grade such as S355.
Not sure whether your drawing calls for structural steel, wear plate, or both? Get in touch for a free quote.