The NM Family in Service
NM360, NM400, NM450 and NM500 are quenched and tempered martensitic plates produced to GB/T 24186-2009. They protect equipment surfaces against sliding, scouring and low-to-moderate impact wear, and they are the standard choice for liners, buckets, blades and wear strips in mining, quarrying and bulk handling.
Grade-by-Grade Comparison
NM360: typical hardness 330-380 HBW with the best toughness and formability of the family; used where bending and welding dominate
NM400: typical hardness 370-430 HBW, the most widely specified grade, balancing wear life with impact resistance
NM450: typical hardness 420-480 HBW for more severe sliding abrasion
NM500: typical hardness 470-530 HBW for heavy sliding and scouring in the most abrasive materials
Wear Resistance versus Toughness
Within the NM family, hardness rises with the grade number and so does resistance to scratching and gouging. At the same time, Charpy toughness and cold formability fall. A 400 HBW plate that bends around a bucket corner would crack at 500 HBW, so the grade is chosen from the actual loading, not from the highest number available.
Fabrication Practice
Plasma and laser cutting are standard, with waterjet available where heat-affected edges must be avoided. Drilling uses carbide tooling. Bending follows the minimum radius for the grade and thickness. Welding uses low-hydrogen consumables with preheat and interpass control, and the procedure is qualified for the hardness level.
Typical Applications
Excavator and loader bucket liners
Chutes, hoppers and silo liners in bulk handling
Dump truck bodies and wear strips
Crusher feed plates and screen decks
Conveyor transfer points and deflectors
Quality Verification
Each delivery is checked against the mill certificate for chemistry and mechanical properties, with Brinell hardness measured on the supplied plates. Dimensional checks cover thickness, flatness and cut tolerances, and ultrasonic testing is available where internal soundness must be demonstrated.
Frequently Asked Questions
Q: Which NM grade is the most popular?
NM400 is the most widely specified grade because it gives a good balance of wear resistance, toughness and fabricability for typical bucket and liner service.
Q: Can I weld NM wear plate to ordinary structural steel?
Yes. Wear liners are often fillet-welded onto Q235 or Q355 structures, using low-hydrogen consumables and controlled preheat for the hardened plate.
Q: How do I decide between NM450 and NM500?
If the wear is mainly sliding with fine abrasive, NM500 lasts longer. If impact is involved or the plate must be bent, NM450 is the safer choice.
Q: What hardness does NM400 actually have?
NM400 is typically supplied at 370-430 HBW, with the measured value reported on the hardness test certificate.
Q: Is wear plate supplied with mill certificates?
Yes. Every delivery includes mill test certificates with chemical composition, mechanical properties and, for wear grades, Brinell hardness results.
Q: Can wear plates be cut to custom shapes?
Yes. Plates are cut to the required blanks and profiles by plasma, laser or waterjet, including bevels and drilled holes, ready for assembly.