What are the differences between NM500 and NM400?

What is NM500?

NM500 is a domestically produced high-strength wear-resistant steel plate. "NM" stands for "wear-resistant" in pinyin, and "500" indicates its Brinell hardness is approximately 500 HBW (actually 480–525 HBW).

It is typically delivered in a quenched and tempered state. Its wear resistance is 3 to 5 times that of ordinary steel plates.

It is widely used in high-wear components such as excavator buckets, crusher liners, mine chutes, and dump truck floor plates, significantly extending equipment life and reducing maintenance costs.

What is NM400?

NM400 is a commonly used low-alloy high-strength wear-resistant steel plate in China. NM represents wear resistance, and 400 indicates an average Brinell hardness of approximately 400 HBW. The typical hardness range is 360–440 HBW.

This steel plate combines high wear resistance, good impact toughness, and excellent machinability, such as bendability, cutting, and welding.

It offers excellent cost-effectiveness and is widely used in mining machinery, construction machinery, dump truck bodies, crusher liners, silo chutes, cement and coal conveying equipment, and other wear-prone applications.

 NM400

NM400 is a medium-hardness wear-resistant steel plate designed to balance hardness and toughness. According to the national standard GB/T 24186, trace amounts of boron (0.0005%–0.006%) are added to improve its hardenability. This relatively conservative alloying ratio allows NM400 to maintain good impact toughness and weldability while ensuring hardness.

 NM500

NM500 is a high-hardness wear-resistant steel plate. To achieve higher hardness and wear resistance, the content of alloying elements has been significantly increased. The addition of trace amounts of boron (0.0005%–0.006%) further enhances hardenability. Due to the increased total alloy content, the carbon equivalent (CEV) of NM500 rises to approximately 0.65, meaning that it is much more difficult to weld and machine than NM400.

 NM400:

NM400 is a widely used medium-hardness wear-resistant steel plate. Its Brinell hardness is 400~450 HBW, around 2-3 times harder than Q235 and other common structural steels for reliable anti-abrasion performance.

Thanks to its low carbon and alloy content, it balances hardness and toughness perfectly. It maintains Charpy V-notch impact energy >=27J at -20℃ and resists cracking effectively. This grade offers superior weldability and cold bending capability.

 NM500:

NM500 is a premium high-hardness wear-resistant steel plate. Its Brinell hardness is minimum 500 HBW, with typical delivery hardness from 500 to 580 HBW. It is 25%~45% harder than NM400 and features outstanding abrasion resistance for high-stress and heavy-wear applications.

The higher carbon and alloy content (C <= 0.35%, Mn, Cr, Mo, B) leads to lower impact toughness. Welding requires proper preheating and interpass temperature control, and the material is harder to cut and bend compared with medium-hardness wear plates.

NM400

 NM400

NM400 wear-resistant steel plate boasts low carbon equivalent and great cold bending performance. The minimum bending radius is over 3 times the plate thickness.

It is easy to weld with regular low-hydrogen welding materials and moderate heat input. Combining good hardness and easy fabrication, NM400 is well suited for parts needing frequent welding and bending.

 NM500

NM500 is much more challenging to fabricate compared with NM400. Its high hardness and carbon equivalent make cold bending unadvisable due to high cracking risk.

Hot bending is recommended if forming is required, with heating temperature kept between 600 and 800 ℃. All processing steps need to be carried out strictly as required.

 NM400

The NM400 is suitable for general working conditions with moderate wear. For example: dump truck bed plates, loader buckets, sand and gravel silos, chutes, coal conveyor liners, cement machinery, sanitation and agricultural machinery parts, etc. It is suitable for soft and moderately abrasive materials such as sand, gravel, coal powder, and soil.

 NM500

The NM500 is suitable for harsh working conditions with severe wear and tear. For example, crusher liners, large mining car bodies, ore hoppers, wear-resistant parts for heavy excavators, sintering equipment liners, and high-hardness rock conveying equipment. It is suitable for hard ores, granite, and high-intensity impact and wear scenarios.

The key to choosing between NM400 and NM500 lies in balancing impact toughness and excellent wear resistance. If your operating environment involves high-speed impacts from large materials (such as excavator bucket teeth or primary crusher feed inlets), NM400 should be prioritized because it has higher elongation and impact energy, absorbing energy through slight deformation, thus preventing brittle fracture or lateral fracture under high-intensity impacts.

Conversely, if the operating environment primarily involves simple sliding wear, NM500 is a more economical choice. Its high hardness of 500 HBW extends its service life by approximately 50%-80% compared to NM400.

1. Can NM400 and NM500 be used interchangeably?

It is not advisable to replace NM400 and NM500 with each other directly. They feature distinct hardness and mechanical properties; blind replacement will compromise equipment service performance and cause early wear or damage. Any cross-grade replacement must be confirmed and assessed by professional design engineers.

2. How should wear-resistant steel plates be cut?

Wear plates can be processed by either flame cutting or plasma cutting. Particularly for NM500, preheating before cutting and slow cooling after cutting are mandatory to avoid delayed cracking.

3. Can NM500 be welded?

NM500 is weldable but demands strict welding procedures. It needs preheating at 100–150℃, matched low-hydrogen welding materials, and proper post-weld tempering treatment to guarantee welding quality.

4. Why can't NM500 be cold-bent?

NM500 owns extremely high hardness and low ductility, so cold bending is very likely to trigger bending cracks or even material fracture. If forming by bending is needed, hot bending process is recommended instead.