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AR400 vs. AR500 vs. Chromium-Carbide Overlay: Wear Liners for Bulk Service

Wear liners protect the chutes, hoppers, troughs, and transfer points of a bulk handling line from the material that runs across them, and three liner families compared here are through-hardened 400 HBW-class plate, 500 HBW-class plate, and chromium-carbide overlay plate. UTEC Industrial designs, engineers, machines, fabricates, and installs custom material handling systems for aerospace and heavy industry from its Spokane Valley, WA facility, integrating Allen-Bradley PLC and motion control with in-house CNC machining, heat treating, and stress relief. This article explains that AR400 and AR500 are industry shorthand for 400 and 500 HBW-class plate, not ASTM designations (in ASTM A829, "AR" means as rolled), what the plate producers' data sheets specify, how overlay plate resists abrasion and why it cracks, what a laboratory abrasion test can and cannot tell a buyer, and how welding, forming, sensing, and monitoring decide how long a liner lasts. Liner selection is made early in the build chain, design → engineering → parts machining → fabrication → assembly → weld fatigue → stress relief → drives → controls → tuning → monitoring, and its consequences show up at the end of that chain, in the wear and temperature data the controls collect.

What do "AR400" and "AR500" actually mean on a liner specification?​

In purchasing shorthand, AR400 and AR500 name abrasion-resistant plate by its nominal Brinell hardness, about 400 HBW and 500 HBW. They are not ASTM designations. Each is a producer's hardness class, bought against that producer's data sheet, and two ASTM plate specifications that can be confused with them are structural specifications whose published scopes state no wear or abrasion requirement:

  • ASTM A514/A514M-22 covers high-yield-strength, quenched-and-tempered alloy steel plate of structural quality, 6 in (150 mm) and under, intended primarily for use in welded structures and other non-welded structures. Conformance is shown by tension and Brinell hardness tests, but it is a high-yield-strength structural specification, not an abrasion specification.
  • ASTM A829/A829M-25 covers structural-quality alloy steel plate, usually specified to chemical composition requirements, although tensile properties may also be specified, and available in five conditions: as rolled, annealed, normalized, normalized and tempered, and quenched and tempered. In that specification "AR" is the as-rolled condition, not "abrasion resistant."

The named failure mode is a purchase order or drawing note that writes "AR" against an ASTM number and receives as-rolled structural plate, which will wear like the chute it was meant to protect. A liner callout should name the hardness class, the producer's data sheet, and the thickness, and this article uses "400 HBW-class" and "500 HBW-class" plate for the two grades (ASTM A514/A514M-22; ASTM A829/A829M-25; SSAB 2026, 400 HBW plate data sheet).

What does a 400 HBW-class wear plate data sheet specify?​

A producer's data sheet for 400 HBW-class plate describes a through-hardened plate supplied quenched and tempered or as quenched. In its mechanical-properties table, the hardness range is the one figure not labelled typical; the strength and impact figures are typical values, and the tensile strength is marked not guaranteed:

  • Hardness: 360 to 444 HBW, measured by the Brinell method of ASTM A370 on a milled or ground surface 0.020 to 0.118 in below the plate surface.
  • Strength (typical): transverse 0.2% yield strength of 150 ksi and tensile strength of 184 ksi, with 23% elongation in 2 in; the tensile figure is marked not guaranteed.
  • Impact (typical): longitudinal Charpy V-notch energy of 25 ft-lb at −40 °F for 3/4 in plate.
  • Chemistry: carbon no more than 0.18% and boron no more than 0.005% (ladle-analysis maxima).
  • Applications: the producer lists hoppers, chutes, crushers, and conveyor troughs among the potential applications.

Two practical points follow. First, the hardness range is 84 HBW wide, so two plates of the same class can differ noticeably at the bottom and top of the range. Second, because the data-sheet hardness is measured on a milled or ground surface below the plate skin, a portable hardness reading taken on the as-received surface is a different measurement and should not be used to reject plate against the data sheet. A liner support or a structural chute wall should not be designed on the typical strength figures, since the producer gives them as typical values and marks the tensile strength not guaranteed (SSAB 2026, 400 HBW plate data sheet, Mechanical Properties and Chemical Composition tables).

How does 500 HBW-class plate differ, and what limits it in hot service?​

The 500 HBW-class data sheet describes a harder plate, with a higher carbon maximum, and a temperature ceiling that matters in hot bulk service:

  • Hardness by thickness: 470 to 530 HBW for plate from 0.157 to 1.260 in thick, and 450 to 540 HBW from 1.264 to 4.055 in, measured by the Brinell method of EN ISO 6506-1 on a surface milled 0.019 to 0.118 in below the plate surface.
  • Through-hardening: a minimum core hardness of 90% of the guaranteed minimum hardness, so the plate does not rely on a thin hard skin.
  • Chemistry and weldability: carbon up to 0.30% in plate, with a maximum carbon equivalent (CEV) rising from 0.53 to 0.91 as thickness increases.
  • Delivery and heat: the plate is delivered quenched, or quenched and tempered, it is not intended for further heat treatment, and its delivery-condition properties are not retained above 482 °F (250 °C).

The 482 °F limit is the one to check first. Material leaving a cooler, kiln, or roaster above that temperature, or a chute that sees hot material during an upset, can take a 500 HBW-class liner out of the condition it was bought in. As design reasoning drawn from that limit, not a statement on the data sheet, the same limit bears on fabrication: any thermal stress relief of a chute or hopper structure should be done before 500 HBW-class liners are fitted, with the liners attached afterward.

The 400 HBW-class and 500 HBW-class data sheets cited here are different product lines, with hardness measured to different standards (ASTM A370 and EN ISO 6506-1) and typical Charpy values reported for different plate thicknesses (3/4 in and 0.787 in), so their typical Charpy values do not rank the two classes for toughness and should not be read that way (SSAB 2026, 500 HBW plate data sheet, Delivery Conditions and Chemical Composition tables).

Which wear mode favors 400 HBW plate, 500 HBW plate, or overlay?​

Wear mode, not hardness alone, decides the liner. ASM's wear handbook has separate articles on abrasive wear, impact wear, the wear resistance of steels, and wear of hardfacing alloys, and a liner choice should start by naming which one each location sees:

  • High-stress sliding abrasion. Along a chute floor or trough bottom where material slides under pressure, a harder plate loses less. In Ratia and co-authors' tests, higher hardness lowered mass loss in every test they ran.
  • Impact from lumps. At drop points and crusher discharges, the same tests found the benefit of hardness smaller under impact-abrasion than under high-stress abrasion. The authors add that this may, at least partly, result from softer materials deforming over the sample edges, which does not show as mass loss. As engineering reasoning, the impact result therefore argues against ranking drop-point liners by an abrasion test, but it does not by itself show how much hardness buys at a drop point. Their test matrix and its reading for drop points are covered in abrasion and dust control in cement plant handling.
  • Fine hard minerals and slurry. The overlay producer lists sliding and moderate-impact wear from hard minerals in small size, such as gravel, slurry, and sand with quartz content, among the situations where overlay plate is the most suitable material.
  • Hot wear. Complex-carbide overlays, in which alloys such as niobium, molybdenum, vanadium, and tungsten are added to the chromium carbide, are usually the preferred overlay for hot wear; the producer states they can maintain full wear resistance up to 1,100 °F (600 °C). That is well above the 482 °F ceiling on 500 HBW-class plate.

These are qualitative selections. None of the sources cited here gives a same-basis service-life ratio between overlay and 400 or 500 HBW-class plate in bulk handling, and vendor life multiples are not a substitute for a trial in the plant's own material (Totten 2017, ASM Handbook Vol. 18, contents; Ratia et al. 2013, Tribology Online vol. 8 no. 2, §4; SSAB 2026, chromium carbide overlay page).

What is chromium-carbide overlay, and why does it resist abrasion?​

Chromium-carbide overlay (CCO) plate is a steel base plate with a hardfacing layer of chromium-rich carbides in a steel matrix welded onto it. The overlay is deposited in one, two, or sometimes three layers, and the producer's own overlay plates use a mild-steel or quenched-and-tempered wear-plate base. The base carries the load and takes the fasteners; the overlay takes the wear.

Chotěborský and co-authors studied why the overlay works. They deposited four commercial high-chromium and complex-carbide hardfacing wires by gas metal arc welding, in one and two layers with no preheat, on low-carbon structural plate and tested them on an abrasive-cloth pin-on-disk machine. Their findings:

  • Carbides do the work. In the chromium-rich deposits, proeutectic M7C3 chromium carbides of about 1500 HV0.1 sit in a eutectic matrix. The authors conclude that the M7C3 carbides had the decisive influence on abrasion resistance, acting as an effective barrier against the advance of the abrasive particles.
  • Microcutting dominates. The main wear mechanism was microcutting of the surface by the abrasive.
  • Pass count matters. In the chromium-rich deposits, the second layer carried a higher volume fraction and larger mean size of chromium carbides than the first, with a volume fraction of 41.5% by image analysis.
  • Chemistry matters. Two-layer complex-carbide deposits showed the best abrasion resistance of the deposits tested.

The design consequence is that the number of layers and the consumable are part of the liner specification. In these tests, every one-layer deposit lost more weight in the abrasion test than the second layer of a two-layer deposit of the same wire (Chotěborský et al. 2008, Research in Agricultural Engineering vol. 54 no. 4, pp. 192-197; SSAB 2026, chromium carbide overlay page).

Why does overlay plate check-crack, and how does that limit forming?​

A new overlay plate shows a pattern of fine cracks across its face, and that pattern is expected. The overlay producer's technical page states that the fine cracks form perpendicular to the welding direction as the welds cool, that they are intended, and that they do not reduce wear resistance. That is the producer's own statement about its plate, and a buyer should confirm the same for any other overlay product on the bid list.

The same page gives the forming rules that follow from the crack pattern:

  • Roll-forming works across the beads. The cracks let overlay plate be roll-formed, usually with the overlay on the inside of the curve, which suits curved chute bottoms and trough liners.
  • Bending parallel to the beads is out. Overlay plate should not be bent parallel to the weld beads.
  • Shop hardfacing is an alternative. Wear parts can also be hardfaced in the shop with wire or stick electrodes rather than cut from overlay plate.

For the drawing, this means bead direction is a dimension. A curved trough or a chute bend has to be laid out so the bend axis runs across the weld beads, and a liner that must be bent both ways is a candidate for flat segments or a shop-hardfaced part instead of a single formed overlay plate (SSAB 2026, chromium carbide overlay page, sections on welding overlay products and the staggered cracking pattern).

What does a G65 abrasion number tell a buyer, and what does it not?​

ASTM G65 is a laboratory test method for ranking metallic materials by abrasion resistance, and a liner data sheet or bid comparison may quote it. As its scope describes, the dry sand/rubber wheel test is intended to produce data that reproducibly rank metallic materials by their resistance to scratching abrasion under a specified set of conditions. Results are reported as volume loss in cubic millimetres for the particular procedure specified, lower being more resistant, and the method covers five recommended procedures appropriate for specific degrees of wear resistance or thicknesses of the test material, one of them for thin coatings. It ranks materials; as the method's significance and use statement says, because it does not attempt to duplicate all of the process conditions, it should not be used to predict the exact resistance of a given material in a specific environment, such as a particular plant.

Three cautions follow for a buyer comparing liners:

  • Same procedure only. G65 volume losses compare only when the same procedure was used.
  • Different tests do not cross-compare. Chotěborský and co-authors' overlay results come from an abrasive-cloth pin-on-disk test to Czech standard CSN 01 5084, not G65, and Ratia and co-authors used a crushing pin-on-disc, a uniaxial crusher, and an impeller-tumbler. Numbers from these tests cannot be placed on one scale.
  • Scratching is not impact. A scratching-abrasion ranking says little about a drop point where lumps strike the liner, which is where Ratia's impact-abrasion test showed a weaker hardness dependence than the abrasion tests, a difference the authors say may be at least partly an edge-deformation effect that mass loss does not capture.

The named failure mode is choosing an impact-zone liner from a scratching-abrasion ranking (ASTM G65-16, reapproved 2021; Chotěborský et al. 2008, p. 192; Ratia et al. 2013, abstract, Table 1, and §4).

How do welding and forming limits shape a lined chute?​

A liner is a fabricated part, and the plate's weldability and formability set how it is cut, bent, and attached. The 400 HBW-class data sheet gives the limits in numbers:

  • Carbon equivalent: typical CEV rising from 0.43 to 0.48 to 0.58 as thickness increases.
  • Preheat: minimum preheat and interpass temperature rising from 60 °F for plate up to 3/4 in, to 210 °F from 3/4 to 1.25 in, to 300 °F from 1.25 to 2 in, with a weld-deposit hydrogen potential of no more than 5 ml/100 g.
  • Bending: minimum recommended inside bend radius of 4.0t to 6.0t, depending on thickness and on the bend axis relative to the rolling direction.

The 500 HBW-class sheet gives a maximum CEV rising from 0.53 to 0.91 with thickness, with typical values above the 400 HBW-class typical figures, and states the plate is not intended for further heat treatment; for welding and bending recommendations it refers to that producer's separate brochures and bending guarantees, so the 400 HBW-class figures above do not carry over. For overlay, the hardfacing consumable is itself a classified product: AWS A5.21/A5.21M:2024 classifies bare solid and tubular (metal-cored and flux-cored) electrodes and rods for surfacing, solid products by their as-manufactured composition and metal-cored and flux-cored tubular products by their deposited weld-metal chemistry, while tubular tungsten carbide rods are classified by the mesh range, quantity, and composition of their tungsten carbide granules.

The rest of this paragraph is design reasoning from these limits. They favor bolted, replaceable plates on a mild-steel structure. The structure is welded and stress-relieved to its own procedure, and the hard plate is attached afterward without heat, which also makes the liner change a maintenance task rather than a weld repair (SSAB 2026, 400 HBW plate data sheet, Carbon Equivalent, Weldability, and Formability tables; SSAB 2026, 500 HBW plate data sheet, Carbon Equivalent table; AWS A5.21/A5.21M:2024).

What sensing and controls protect a liner and track its wear?​

A liner has no sensors of its own, but the controls around it decide whether it wears out on schedule or fails early. The intelligence layer for a lined bulk line typically covers four things:

  • Temperature at the liner. Where the material can arrive above 482 °F, the ceiling above which 500 HBW-class plate loses its delivery-condition properties, a temperature measurement at the chute or hopper inlet with an alarm and a feed stop protects the liner as well as the downstream equipment. On a complex-carbide overlay, which its producer states keeps full wear resistance up to 1,100 °F, the same measurement confirms the liner is inside that limit.
  • Flow and blockage. Plugged-chute switches at transfer points, level sensing in hoppers, and zero-speed sensing on the conveyors and screws below them stop the feed when material stops moving, before a packed chute is cleared by hand.
  • Load on the drive. Trending the current of a screw, drag chain, or feeder at a known feed rate shows buildup and wear as a rising load.
  • Thickness records. Liner thickness read at fixed points and logged against tonnage gives a wear rate per location; the abrasive mineral processing article sets out how that record turns into a scheduled change.

A liner change is also an energy-isolation task. OSHA 29 CFR 1910.147 covers the servicing and maintenance of machines and equipment in which the unexpected energization or start-up of the machines or equipment, or release of stored energy, could cause injury to employees. Under it, push buttons, selector switches, and other control-circuit devices are not energy-isolating devices, and 1910.147(d)(5)(i) requires that, after lockout or tagout devices are applied to energy isolating devices, all potentially hazardous stored or residual energy be relieved, disconnected, restrained, and otherwise rendered safe, which includes material hung up above a chute. ASME B20.1-2024, the safety standard for conveyors and related equipment, applies to the design, construction, installation, maintenance, inspection, and operation of conveyors and conveying systems in relation to hazards, and excludes any conveyor designed, installed, or used primarily for moving people. UTEC Industrial, a Rockwell Automation Recognized System Integrator, integrates Allen-Bradley ControlLogix and CompactLogix control with the sensing described here (SSAB 2026, 500 HBW plate data sheet; SSAB 2026, chromium carbide overlay page; OSHA 29 CFR 1910.147-1989; ASME B20.1-2024).

What should a wear-liner specification state?​

A liner request that says only "AR plate" leaves the supplier to guess at every decision that sets liner life. A complete specification states:

  • The material: its classification under ANSI/CEMA 550-2020, the standard that classifies bulk materials by physical characteristics and handling properties, together with its abrasiveness, lump size, moisture, and maximum temperature.
  • The wear mode at each location: sliding, impact, fine-particle or slurry, or hot, so the liner family is chosen per location rather than once for the whole line.
  • The plate or overlay: hardness class and producer data sheet for plate, never an ASTM number with "AR" appended; for overlay, the base plate, the number of layers, and the consumable class under AWS A5.21/A5.21M:2024.
  • Forming and layout: bend radii, and bead direction relative to every bend for overlay plate.
  • Attachment and access: bolted or welded, liner segment weight for handling, and access doors sized for the change.
  • Test basis: if an abrasion ranking is part of the bid comparison, the ASTM G65 procedure used, and a statement that it is a ranking, not a life guarantee.

For where liners concentrate in a mineral line, see the abrasive mineral processing article; for insert and material-on-material liners, where the flowing material wears against a trapped bed instead of the steel, see the cement plant abrasion article (ANSI/CEMA 550-2020; AWS A5.21/A5.21M:2024; ASTM G65-16, reapproved 2021).

Where does liner selection sit in the design-to-monitoring chain?​

A liner looks like a single part, but it depends on every link of the build chain:

  • Design and engineering. The wear mode, temperature, and material class at each location set the liner family and thickness, and the structure is sized to carry the liner weight as well as the material.
  • Parts machining and fabrication. Liner segments are cut and drilled for fasteners, overlay plate is formed across its beads, and 400 HBW-class plate is welded only inside its preheat and consumable limits.
  • Assembly, weld fatigue, and stress relief. A chute or hopper that vibrates under continuous flow loads its welds in fatigue. As design reasoning from the 482 °F limit on the 500 HBW-class data sheet, any thermal stress relief should come before a 500 HBW-class liner is fitted.
  • Drives, controls, tuning, and monitoring. Feed rate, temperature alarms, plug detection, drive-current trends, and thickness records decide whether the liner wears at the rate it was designed for.

UTEC Industrial performs automated vibratory stress relief and NDT and CMM inspection on the fabricated structures it builds, which is where the chute and hopper bodies behind the liners are qualified (SSAB 2026, 500 HBW plate data sheet; SSAB 2026, chromium carbide overlay page; Ratia et al. 2013, §4).

Related Articles

References​

  • ASTM A514/A514M-22: Standard Specification for High-Yield-Strength, Quenched and Tempered Alloy Steel Plate, Suitable for Welding. ASTM International, 2022.
  • ASTM A829/A829M-25: Standard Specification for Alloy Structural Steel Plates. ASTM International, 2025.
  • SSAB. AR400F Data Sheet (undated web documentation, accessed September 2026). SSAB, 2026.
  • SSAB. Hardox 500 Data Sheet (undated web documentation, accessed September 2026). SSAB, 2026.
  • SSAB. Chromium Carbide Overlay (CCO) Solutions (undated web documentation, accessed September 2026). SSAB, 2026.
  • Totten GE (ed.). ASM Handbook, Volume 18: Friction, Lubrication, and Wear Technology. ASM International, 2017. ISBN 978-1-62708-141-2.
  • Ratia V, Valtonen K, Kemppainen A, Kuokkala V-T (2013). "High-Stress Abrasion and Impact-Abrasion Testing of Wear Resistant Steels." Tribology Online, 8(2), 152-161. DOI 10.2474/trol.8.152
  • Chotěborský R, Hrabě P, Müller M, Savková J, Jirka M (2008). "Abrasive wear of high chromium Fe-Cr-C hardfacing alloys." Research in Agricultural Engineering, 54(4), 192-198. DOI 10.17221/1/2008-RAE
  • ASTM G65-16(2021): Standard Test Method for Measuring Abrasion Using the Dry Sand/Rubber Wheel Apparatus. ASTM International, 2021.
  • AWS A5.21/A5.21M:2024: Specification for Bare Electrodes and Rods for Surfacing. American Welding Society, 2024.
  • OSHA 29 CFR 1910.147-1989: The Control of Hazardous Energy (Lockout/Tagout). Occupational Safety and Health Administration, 1989.
  • ASME B20.1-2024: Safety Standard for Conveyors and Related Equipment. ASME, 2024.
  • ANSI/CEMA 550-2020: Classification and Definitions of Bulk Materials. Conveyor Equipment Manufacturers Association, 2020.

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