Introduction to NM450 Steel Sheet
NM450 is a hot rolled, quenched and tempered wear resistant steel sheet with a guaranteed hardness of 420-480 HBW per GB/T 24186-2009. The designation NM stands for the Chinese wear resistant (nai mo) series and 450 refers to the nominal Brinell hardness level. Unlike abrasion-resistant grades that are simply hard, NM450 is engineered with a tempered martensitic microstructure that preserves impact toughness, so it can be used where wear and impact occur together.
How NM450 Is Made
The plate is produced by hot rolling a low-carbon alloy composition, followed by quenching in water or other media to form martensite and tempering at a controlled temperature to adjust hardness and toughness. This through-hardening treatment gives the plate its wear resistance across the full thickness, unlike cladded or surface-hardened products. Typical yield strength is above 1000 MPa in thin sections, with elongation around 12-15% depending on thickness.
Hardness and Property Comparison
NM400 - 360-440 HBW; general wear service and structural wear liners.
NM450 - 420-480 HBW; the balanced grade for buckets, chutes and crushing plant.
NM500 - 470-540 HBW; severe sliding abrasion with limited impact.
NM550 - 530-580 HBW; extreme abrasion in screens, feeders and classifier components.
NM450 sits at the point where wear resistance is already high but welding and forming remain practical, which is why it dominates mining wear applications.
Applications in Mining Engineering
NM450 sheet is specified across the mining and quarrying chain:
Excavator and loader buckets - floor, side and lip liners subject to loading impact and sliding ore.
Chutes, hoppers and transfer points - liners where material flows and abrades continuously.
Crusher feed and screen decks - wear plates that absorb impact from large rock.
Truck bodies and haul road equipment - floor and side liners for dump trucks.
Conveyor transfer and classifier wear parts - replaceable wear strips and discharge liners.
Fabrication Guidelines
NM450 can be plasma or laser cut, but preheating to 100-150 °C is recommended for sections over 20 mm to prevent edge cracking. Welding requires low-hydrogen consumables such as AWS E7018 or matching wear-resistant filler, with preheat and interpass temperatures controlled between 100-200 °C. Bending should be performed in the transverse direction with a minimum radius of about 4-6 times the plate thickness, increasing with thickness and hardness.
Frequently Asked Questions
Q: What hardness does NM450 guarantee?
NM450 is guaranteed to 420-480 HBW per GB/T 24186-2009, measured on the quenched and tempered plate surface after scale removal.
Q: Can NM450 be welded directly to Q235 or Q355 frames?
Yes, using low-hydrogen filler metal and controlled preheat; the weld itself is designed as a structural joint while the hardened plate carries the wear.
Q: What thickness range is available?
NM450 is commonly supplied from 6 mm to 60 mm, with widths up to 2500 mm and lengths up to 12000 mm.
Q: How does NM450 compare with AR450?
They are equivalent concepts under different standards; NM450 follows GB/T 24186 while AR450 is the common export designation, both around 420-480 HBW.
Q: Is NM450 suitable for impact loading?
Yes, its tempered microstructure provides better impact toughness than the harder NM500 and NM550 grades, which is why it is chosen for bucket and crusher liners.
Q: Do you supply cut-to-size NM450 blanks?
Yes, plates can be plasma cut, laser cut or water-jet cut to drawing, with edges deburred and bundles marked per piece.