GB/T 24186 Wear-Resistant Steel Plates: NM400-NM600 Technical Specifications & Performance Comparison

GB/T 24186, China’s national standard for high-strength abrasion-resistant steel plates, defines a family of quenched and tempered (Q&T) alloys—NM400, NM450, NM500, NM550, and NM600—that excel in harsh environments requiring resistance to impact, friction, and wear. These grades are engineered with precise chemical compositions and heat treatment processes to deliver graduated levels of hardness and strength, making them indispensable for construction machinery, thermal power plants, coal yards, mines, and port logistics. This article provides a detailed technical breakdown of each grade, comparing their chemical makeup, mechanical properties, and performance nuances to guide optimal material selection.

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GB/T 24186 Wear-Resistant Steel Plates: NM400-NM600 Technical Specifications & Performance Comparison-566

GB/T 24186 Wear-Resistant Steel Plates: NM400-NM600 Technical Specifications & Performance Comparison-565

GB/T 24186 Wear-Resistant Steel Plates: NM400-NM600 Technical Specifications & Performance Comparison-564

GB/T 24186 Wear-Resistant Steel Plates: NM400-NM600 Technical Specifications & Performance Comparison-563

GB/T 24186 Wear-Resistant Steel Plates: NM400-NM600 Technical Specifications & Performance Comparison-thumbnail-566

GB/T 24186 Wear-Resistant Steel Plates: NM400-NM600 Technical Specifications & Performance Comparison-thumbnail-565

GB/T 24186 Wear-Resistant Steel Plates: NM400-NM600 Technical Specifications & Performance Comparison-thumbnail-564

GB/T 24186 Wear-Resistant Steel Plates: NM400-NM600 Technical Specifications & Performance Comparison-thumbnail-563

Product Details

1. Standard Overview & Grade Nomenclature

Standard Scope: GB/T 24186 specifies requirements for wear-resistant steel plates used in heavy-duty equipment and structural components, covering thicknesses from 6mm to 100mm (common ranges: 10–50mm for industrial use).
Nomenclature Logic:
- “NM”: Abbreviation for “Nai Mo” (Chinese for “wear-resistant”);
- Numeric Suffix (400–600): Indicates minimum Brinell Hardness (HB) – e.g., NM400 ≥400 HB, NM600 ≥600 HB.
Core Advantage: All grades undergo quenching + tempering heat treatment, balancing high hardness with ductility (avoids brittleness in impact-prone applications).

2. Chemical Composition Comparison (GB/T 24186-2022)

The alloy system is optimized with chromium (Cr), molybdenum (Mo), and nickel (Ni) to enhance wear resistance and toughness. Key elements (mass fraction, %):

Element	NM400	NM450	NM500	NM550	NM600	Core Function
Carbon (C)	0.12–0.20	0.14–0.22	0.16–0.24	0.18–0.26	0.20–0.28	Enhances hardness and wear resistance; controlled to maintain ductility
Manganese (Mn)	1.00–1.60	1.20–1.80	1.40–2.00	1.60–2.20	1.80–2.40	Improves hardenability and impact toughness
Silicon (Si)	0.20–0.60	0.20–0.60	0.20–0.60	0.20–0.60	0.20–0.60	Enhances oxidation resistance and strength
Chromium (Cr)	0.80–1.20	1.00–1.40	1.20–1.60	1.40–1.80	1.60–2.00	Forms hard carbides (Cr₇C₃) for wear resistance
Molybdenum (Mo)	0.20–0.40	0.30–0.50	0.40–0.60	0.50–0.70	0.60–0.80	Improves tempering stability and toughness
Nickel (Ni)	≤0.50	≤0.60	≤0.70	≤0.80	≤0.90	Enhances low-temperature impact resistance
Phosphorus (P)	≤0.025	≤0.025	≤0.025	≤0.025	≤0.025	Strictly limited to avoid brittleness
Sulfur (S)	≤0.015	≤0.015	≤0.015	≤0.015	≤0.015	Minimized to prevent hot cracking

3. Mechanical Properties (Quenched & Tempered State)

Performance scales with the numeric grade—higher NM numbers deliver greater hardness and strength, with controlled ductility for practical use:

Performance Indicator	NM400	NM450	NM500	NM550	NM600	Test Standard
Brinell Hardness (HB)	400–460	450–510	500–560	550–610	600–660	GB/T 231.1
Yield Strength (Rp0.2, MPa)	≥1000	≥1100	≥1200	≥1300	≥1400	GB/T 228.1
Tensile Strength (Rm, MPa)	1200–1400	1300–1500	1400–1600	1500–1700	1600–1800	GB/T 228.1
Elongation (A50mm, %)	≥10	≥9	≥8	≥7	≥6	GB/T 228.1
Impact Energy (CVN, J, 20°C)	≥24	≥22	≥20	≥18	≥16	GB/T 229

4. Performance Differences & Selection Guide

NM400: Entry-level wear resistance; ideal for low-to-medium wear scenarios (e.g., dump truck bodies, non-critical conveyor liners). Balances cost and durability for general engineering.
NM450: Mid-range option; used in coal handling equipment (e.g., coal hoppers, chutes) and construction machinery buckets (light-duty excavators).
NM500: Most versatile grade; dominates thermal power plants (coal mill liners, ash handling systems), 矿山 crushers, and port bulk material handlers. Offers optimal wear resistance vs. cost.
NM550: High-hardness grade; for severe wear (e.g., rock crusher jaws, heavy-duty bulldozer blades) where impact and abrasion are extreme.
NM600: Premium grade; specialized for ultra-severe wear (e.g., mineral processing equipment, cement kiln liners). Requires careful fabrication (pre-heat recommended for welding).