NM500 is an ultra-high-strength wear-resistant steel plate. Its designation follows the internationally recognized naming system for wear-resistant steels and primarily complies with the performance requirements specified in the European standard EN 13242:2022 "Aggregates for Unbound and Hydraulically Bound Mixtures for Construction Works – Specifications". It is also widely referenced against national industry standards, such as China's GB/T 24186-2019 "High-Strength Wear-Resistant Steel Plates for Construction Machinery". This standard clearly defines the chemical composition, mechanical properties, hardness, and testing methods for NM-series wear-resistant steels and serves as a widely accepted technical basis for production and trade globally. As one of the highest commonly used hardness grades in the NM series, NM500 delivers exceptional performance in extreme wear conditions and is a key material for extending equipment life and reducing maintenance costs.
The designation "NM500" has a clear meaning:
"NM" stands for "Nai Mo", the pinyin abbreviation of the Chinese term for "Wear-Resistant". This naming convention is widely used in China and markets influenced by Chinese standards to identify high-strength low-alloy wear-resistant steels, distinguishing them from ordinary structural steels.
"500" indicates the average Brinell hardness of the steel after quenching and tempering heat treatment is 500 HBW. According to relevant standards (e.g., EN ISO 6506-1), its actual hardness typically ranges from 470 to 530 HBW. This is the highest commonly used grade within the NM series, capable of resisting the most severe abrasive wear. While placing the highest demands on toughness, weldability, and processability, it represents a top-tier wear-resistant steel that achieves the optimal balance between extreme wear resistance and limited toughness.
The primary application of NM500 steel plate is in manufacturing critical components operating under extreme wear conditions, especially where resistance to intense abrasive wear, high-stress impact, and gouging wear is required. Typical applications include:
Mining and Quarry Equipment: High-wear areas of jaw crushers, cone crushers, and impact crushers, such as moving/fixed jaw plates, crushing mantles, concaves, and impact plates, which are in direct contact with hard rock and ore.
Construction Machinery: Bucket teeth, front cutting edges, and base plates of large excavators and loaders—parts subjected to high impact and severe wear.
Dump Trucks and Haulage Vehicles: Floor and side panels of heavy-duty mining trucks and dumper trucks transporting highly abrasive materials like iron ore, granite, and construction demolition debris.
Cement and Building Materials Industry: Critical components such as rollers, mill liners, classifier rotors, and pipeline elbows in vertical mills, ball mills, and conveying systems exposed to high-speed particle erosion.
Power and Metallurgical Industries: Coal chute pipes, raw coal bunkers, and ash hoppers in dust collectors—areas prone to severe wear.
Its main characteristics include:
Extremely High Surface Hardness and Outstanding Wear Resistance: A hardness of 500 HBW provides top-tier resistance to abrasive wear, offering a service life far exceeding that of ordinary steel and medium-hardness wear-resistant steels, significantly reducing maintenance costs.
Optimized Toughness and Impact Resistance: Through advanced alloy design and precise quenching & tempering processes, NM500 maintains relatively sufficient toughness despite its ultra-high hardness, enabling it to withstand moderate impact loads and reducing the risk of cracking.
Limited Weldability: Welding is extremely challenging and must strictly follow welding procedures, including thorough preheating (typically 200–250°C or higher), use of specialized wear-resistant filler materials, control of interpass temperature, and post-weld slow cooling to prevent cold cracking.
Very Poor Cold Formability: Due to its extremely high hardness, cold forming capability is highly limited. Cold working is generally not permitted; only cutting and drilling are feasible for secondary processing.
High Cost-Effectiveness (for Specific Applications): Although expensive, its exceptionally long service life in extreme wear conditions drastically reduces downtime and replacement frequency, resulting in significant overall economic benefits.
Therefore, NM500 is a top-tier high-strength wear-resistant steel, making it an ideal choice for combating the most severe wear challenges.
Ultrasonic Testing (UT)
A key non-destructive testing technique that uses high-frequency sound waves to detect internal flaws in steel plates. The probe emits sound waves, which reflect when encountering defects such as cracks or inclusions. The receiver captures the echoes, enabling precise determination of defect location and size. With high sensitivity, strong penetration, and fast inspection speed, UT effectively ensures internal quality, widely used in the production of heavy plates, pressure vessel plates, and other high-end products to guarantee safety and reliability.
Magnetic Particle Testing (MT)
A common surface inspection method that magnetizes the workpiece, causing leakage magnetic fields at surface or near-surface defects like cracks or inclusions, which attract magnetic particles to form visible indications. Simple to operate and highly sensitive, MT is suitable for rapid inspection of surface and near-surface flaws in ferromagnetic materials, widely used for online or offline inspection of plate edges, ends, and welds, ensuring product quality and safety.
Penetrant Testing (PT)
A non-destructive method for detecting surface-breaking flaws. A penetrant liquid is applied to the cleaned steel surface, allowing it to seep into defects such as cracks or pores. After removing excess penetrant, a developer is applied, causing the trapped penetrant to bleed out and form visible indications. Simple and cost-effective, PT is suitable for inspecting surface defects in various non-porous materials, commonly used for welds, castings, and complex components, effectively ensuring surface quality of steel plates.
