Hot Rolled Wear Resistant Plate: Product Overview
Hot rolled wear resistant plate is a quenched and tempered steel plate with a Brinell hardness in the 270 to 600 HBW range, produced for components that lose material to sliding abrasion and impact. Under GB/T 24186 the NM designation pairs the characters for wear resistance with the nominal average Brinell hardness, so NM400 indicates a plate of roughly 400 HBW. The grades most widely specified for mining and material handling are NM360, NM400, NM450 and NM500, usually stocked in thicknesses from 6 to 50 mm.
Because hardness is obtained by quenching followed by tempering, the plate keeps a hard surface together with enough core toughness to survive impact loading. That is why it far outlasts plain carbon structural plate in hoppers, chutes, buckets, liners and truck bodies.
Grade Range and Mechanical Properties
Hardness increases with the grade number while ductility falls, so grade selection is a balance between wear life and resistance to cracking under impact.
| Grade | Thickness (mm) | Hardness (HBW) | Elongation, min | Tensile strength, min |
|---|---|---|---|---|
| NM300 | Up to 80 | 270 to 330 | 14 percent | 1000 MPa |
| NM360 | Up to 80 | 330 to 390 | 12 percent | 1100 MPa |
| NM400 | Up to 80 | 370 to 430 | 10 percent | 1200 MPa |
| NM450 | Up to 80 | 420 to 480 | 7 percent | 1250 MPa |
| NM500 | Up to 70 | 470 min | Reference | Reference |
| NM550 | Up to 70 | 530 min | Reference | Reference |
| NM600 | Up to 60 | 570 min | Reference | Reference |
NM400 and NM450 are the common compromise for abrasive ore and coal handling. NM500 and harder grades are reserved for high wear points where impact energy is limited, because ductility continues to fall as hardness rises. The NM series also corresponds in hardness class to equivalent wear plate grades offered under other national standards, which helps when converting an existing drawing.
Chemical Composition (GB/T 24186, Max Percent)
| Grade | C | Si | Mn | P | S | Cr | Ni | Mo | Ti |
|---|---|---|---|---|---|---|---|---|---|
| NM300 | 0.23 | 0.70 | 1.60 | 0.025 | 0.015 | 0.70 | 0.50 | 0.40 | 0.050 |
| NM360 | 0.25 | 0.70 | 1.60 | 0.025 | 0.015 | 0.80 | 0.50 | 0.50 | 0.050 |
| NM400 | 0.30 | 0.70 | 1.60 | 0.025 | 0.010 | 1.00 | 0.70 | 0.50 | 0.050 |
| NM450 | 0.35 | 0.70 | 1.70 | 0.025 | 0.010 | 1.10 | 0.80 | 0.55 | 0.050 |
| NM500 | 0.38 | 0.70 | 1.70 | 0.020 | 0.010 | 1.20 | 1.00 | 0.65 | 0.050 |
| NM550 | 0.38 | 0.70 | 1.70 | 0.020 | 0.010 | 1.20 | 1.00 | 0.70 | 0.050 |
| NM600 | 0.45 | 0.70 | 1.90 | 0.020 | 0.010 | 1.20 | 1.00 | 0.80 | 0.050 |
Carbon rises from about 0.23 percent in NM300 to 0.45 percent in NM600 to support hardenability, while chromium, nickel and molybdenum deepen the hardening response and titanium with a small boron addition controls grain growth. Boron is held in the 0.0005 to 0.006 percent range and aluminium to a minimum of 0.010 percent for grain refinement.
Thickness, Size Range and Delivery Condition
Thickness: 6 to 50 mm is the standard hot-rolled wear plate range; 3 to 100 mm can be supplied for specific projects.
Width: up to 2500 mm, with 600 to 2500 mm covering most requirements.
Length: 1000 to 12000 mm, or cut to drawing.
Delivery condition: quenched and tempered, with sheared or flame-cut edges.
Surface: clean mill finish; shot blasting and priming can be applied on request.
Documentation: mill test certificates are issued with the goods, and independent inspection is accepted.
Applications and Fabrication Notes
The main outlets are mining machinery and bulk material handling: excavator and loader bucket liners, dump truck trays, crusher and mill liners, chute and hopper liners, conveyor skirt boards, screen decks, transfer points and wear pads in cement, steel and power plants. Structural plate of this class also serves factory equipment manufacture and ship building structures such as decks and hull sections.
Cutting: plasma, laser or waterjet cutting is preferred; oxy-fuel cutting of the hardest grades leaves a softened edge that should be machined off.
Drilling: carbide or cobalt tooling with coolant is recommended, keeping spindle speeds low to avoid work hardening.
Welding: use low-hydrogen consumables, a moderate heat input and preheat for thick NM450 and harder plate; avoid welding into highly restrained corners where cracking can start.
Forming: keep bend radii generous and orient bends transverse to the rolling direction where possible.
Frequently Asked Questions
Q: What do the letters NM mean in a wear plate grade?
NM stands for the wear resistant series in GB/T 24186, and the following number gives the nominal average Brinell hardness of the plate, so NM400 is roughly 400 HBW.
Q: Which grade should be chosen for a mining truck body?
NM400 or NM450 is typical for trays and liners, giving a good balance of wear life and impact resistance. Harder grades are used only where impact energy is low.
Q: Can wear resistant plate be welded?
Yes. Low-hydrogen consumables, controlled heat input and preheating on thick or hard grades produce sound joints and preserve hardness in the parent plate.
Q: What thickness range is available?
Standard supply covers 6 to 50 mm, and 3 to 100 mm can be produced for specific applications, with widths up to 2500 mm and lengths to 12000 mm.
Q: How is the plate supplied and tested?
It is delivered quenched and tempered with sheared or flame-cut edges. Hardness, chemistry and mechanical results are recorded on the mill test certificate.
Q: Does higher hardness always mean longer service life?
Not always. In high-impact duties a less hard but tougher grade such as NM400 can outlast NM500, because cracking and spalling become the dominant failure mode.