NM400 Wear Plate Chemical Composition and Hardness
NM400 should not be purchased from an unattributed chemical-composition table. The designation identifies a nominal abrasion-resistant steel class within a controlled specification, while actual chemistry limits, hardness acceptance, delivery condition and thickness coverage must come from the ordered standard and the steelmaker’s applicable certificate.
This buyer guide explains what “NM400 chemical composition and hardness” information is useful, what can be misleading, and how to write a traceable chute-liner RFQ.
Identify the governing standard first
China’s official national-standard database lists GB/T 24186-2022, High strength abrasion resistant steel plate, sheet and strip for construction machine, as current, with implementation from 1 May 2023. A quotation should state the standard number and year, grade, suffix or toughness class where applicable, plate thickness and delivery condition.
Do not cite “GB/T 24186” without an edition when the contract needs unambiguous requirements. Do not silently use values from the superseded 2009 edition. If a proprietary grade is ordered, identify its exact producer and current product specification.
Why internet NM400 chemistry tables disagree
Many pages reproduce maximum percentages without stating edition, thickness, delivery condition, heat analysis versus product analysis, or grade suffix. Some mix one steelmaker’s proprietary composition with a national grade. Others present a typical value as a guaranteed maximum. These differences make the table unsuitable as purchase acceptance criteria.
| Table entry | Question to ask | Risk if unclear |
|---|---|---|
| C, Mn, Cr, Ni, Mo, B | Is the value a maximum, range, typical result or actual heat analysis? | A typical recipe may be mistaken for a contractual limit. |
| P and S | Which analysis and standard edition apply? | Values may come from a different grade or thickness. |
| CEV/CET | Is it guaranteed, calculated from the certificate or merely typical? | Welding controls may be based on the wrong value. |
| Hardness | What scale, range, location, thickness and test method apply? | A single converted reading may be treated as proof of grade. |
Chemistry supports processing, but does not replace properties
Carbon and alloying elements help the producer achieve hardenability, strength, toughness and processability through a controlled steelmaking and heat-treatment route. Two compliant plates do not need identical chemistry if the governing specification allows a composition envelope and both meet all ordered requirements.
For the buyer, chemistry is most useful for identity, traceability, welding review and comparison with the specified limits. It does not by itself prove abrasion performance, impact suitability or finished-panel quality.
Heat analysis, product analysis and certificate identity
The purchase specification should state which analysis is required and how it is reported. The material certificate must link the heat or plate identity to the finished liner. When parts are nested from a parent plate, the fabricator needs a controlled method to preserve traceability after cutting, forming, machining and painting.
| Certificate field | Buyer verification | Reason |
|---|---|---|
| Standard/grade | Matches the PO, drawing and approved deviation list. | Prevents substitution by a similarly named grade. |
| Heat and plate number | Matches transferred markings or cutting records. | Links actual results to finished parts. |
| Dimensions | Covers the ordered thickness and product form. | Properties and tolerances may be thickness dependent. |
| Chemistry and tests | Clearly states actual values and contractual limits where required. | Allows a real conformity review instead of logo checking. |
| Issuer and authorization | Identifiable document source, pages and issue date. | Supports document control and authenticity review. |
Understand the NM400 hardness designation
The number “400” is a nominal hardness-class identifier, not an instruction that every test must equal 400 HBW. The applicable standard and ordered variant define the range, test position, sampling and any thickness effects. Purchase documents should reproduce or reference those controlled requirements rather than create an unofficial range.
ISO 6506-1:2014, confirmed in 2025, specifies the Brinell test method for metallic materials and applies to fixed and portable machines. The material/product specification still governs sampling and acceptance.
HBW, HRC and hardness conversions
If the order specifies Brinell hardness, report HBW under the required method whenever practical. ISO 6508-1:2023 defines Rockwell test methods. ISO 18265:2013, confirmed in 2024, explains hardness conversions and cautions that converted values are directly applicable only to the exact material tested; for other materials they are indicators and should not replace the correct standard method.
Therefore, a portable HRC reading converted to HBW is not automatically equivalent to a specified Brinell acceptance test. Record the original scale, method, instrument, surface, location and conversion basis.
Surface preparation and test location
Scale, decarburization, rough cutting, curvature, inadequate support and a shallow or improperly prepared surface can distort readings. State whether the test is on the parent plate, a milled subsurface, a finished panel or an installed component. Avoid testing too close to an edge, bend, hole, weld or heat-affected zone unless the procedure specifically addresses that location.
The wear-plate hardness testing guide provides a sampling and reporting checklist.
Hardness does not prove toughness or weldability
Two materials with similar surface hardness can have different toughness, through-thickness behaviour, processing recommendations and certificate requirements. A harder reading does not prove that a plate will resist impact cracking. Chemistry and carbon-equivalent information can support welding review, but the approved procedure must follow the actual material producer’s recommendations and project requirements.
Thickness and hardness must be read together
Hardness ranges and test positions may vary by product thickness. The finished liner thickness also changes mass, clear opening, countersink residual section and forming capability. Confirm that the certificate covers the supplied thickness, then review the application with the chute liner thickness decision framework.
NM400 versus proprietary 400-class products
A branded 400-class plate can provide a useful comparison, but it is not automatically interchangeable with NM400. For example, SSAB’s official Hardox 400 product page publishes its own thickness ranges, mechanical properties, chemistry and test notes. Those values govern that brand, not all NM400 plate.
If alternatives are allowed, the purchaser should define an equivalence-review process covering standard, hardness, toughness, thickness, forming, welding, tolerances, certificates and service evidence. Never approve substitution from the nominal number alone.
Application review for chute liners
| Evidence | Material question | System question |
|---|---|---|
| Stable sliding abrasion | Does the ordered hardness class and wear allowance suit the history? | Are joints smooth and flow direction controlled? |
| Impact dents or cracks | Is toughness information required? | Is the panel supported and is the impact footprint controlled? |
| Extensive bending | What are the producer’s forming limits for this thickness? | Can geometry be segmented or changed without harming flow? |
| Field welding | What certificate chemistry and producer guidance apply? | Can attachment be redesigned for controlled shop processing? |
| Repeated loose bolts | Is grade really the cause? | Review holes, backing, torque procedure and panel movement. |
Pre-shipment inspection package
Request the controlled drawing, material certificate, transferred traceability, dimensional report and hardness evidence defined by the order. Verify part number, drawing revision, heat/plate link, finished thickness, hole or bend geometry and permanent orientation marking. A certificate cannot compensate for a panel manufactured to the wrong revision.
RFQ checklist
- standard number and edition, full grade and suffix;
- plate thickness, dimensions, quantity and delivery condition;
- liner layout, individual drawings and flow direction;
- handled material, impact, moisture, temperature and wear history;
- cutting, drilling, bending, machining and welding requirements;
- required material certificate type and traceability level;
- hardness test method, scale, location, sampling and acceptance range;
- dimensional report, marking, packing and approved-alternative procedure.
Related pages: NM400 Wear Plate, NM400 vs NM450 vs NM500, quality documents for custom chute liners and custom processed wear plates.
Technical review boundary
This guide does not reproduce controlled standard tables and does not certify material from a grade name or photograph. Updated by the EB China engineering-content team against the official current GB/T listing and cited ISO scopes. The purchase order, applicable standard, approved drawing and verified certificate govern acceptance.