NM400 / NM400D / NM400E Abrasion Resistant Steel Plate

⚙️ Chinese high strength wear-resistant steel for construction machinery — GB/T 24186-2022
🔥 Delivery: Quenched | Quenched+Tempered | TMCP+Tempered | Tempered | Hot rolled

📌 Designation method (GB/T 24186-2022)

The designation consists of the pinyin initial letters "NM" for "wear-resistant" and the specified surface Brinell hardness value. For steel requiring low-temperature toughness, the designation includes the quality class symbol (D, E).

Example 1: NM400 — NM: wear-resistant; 400: nominal surface Brinell hardness (HBW).

Example 2: NM400D — D grade: impact test temperature -20°C.

Example 3: NM400E — E grade: impact test temperature -40°C.

📏 Thickness Range

NM400 / NM400D / NM400E: Thickness ≤120 mm (per GB/T 24186-2022 Table 1)

🧪 Chemical Composition (mass fraction / %) — Standard Grade (Table 2)

Grade C ≤ Si ≤ Mn ≤ P ≤ S ≤ Cr ≤ Ni ≤ Mo ≤ Ti ≤ B Als ≥
NM400 0.30 0.70 1.60 0.025 0.010 1.20 0.70 0.50 0.05 0.0005~0.006 0.010

🧪 Chemical Composition — Low-Temperature Toughness Grades D/E (Table 3)

Grade C ≤ Si ≤ Mn ≤ P ≤ S ≤ Cr ≤ Ni ≤ Mo ≤ Ti ≤ B Als ≥ CEV ≤ (≤50mm) CEV ≤ (>50mm)
NM400D / NM400E 0.25 0.70 1.60 0.020 0.005 1.20 0.70 0.60 0.05 0.0005~0.006 0.015 0.57 0.67
ⓘ CEV formula: CEV = C + Mn/6 + (Cr+Mo+V)/5 + (Cu+Ni)/15. D/E grades have stricter P, S limits and higher Mo for low-temperature toughness.

📊 Brinell Hardness (GB/T 24186-2022 Table 4)

Grade Thickness (mm) Surface Brinell Hardness (HBW) Center Section Hardness (HBW)
NM400 / NM400D / NM400E ≤80 370~430 330~430
NM400 / NM400D / NM400E >80~120 360~440 —

📊 Impact & Tensile Properties

Grade Thickness (mm) Longitudinal Impact Energy KV2 (J) ≥ Tensile Rm (MPa) ≥
(optional, transverse)		 Elongation A (%) ≥
(optional, transverse)
NM400 ≤80 — (not required) 1200 10
NM400D ≤80 ≥24 (test temperature -20°C) 1200 10
NM400E ≤80 ≥24 (test temperature -40°C) 1200 10
NM400D/E >80~120 ≥21 (per Table 5) ≥1100 ≥9
📌 Note: Tensile and elongation are optional requirements — only when specified in the contract per GB/T 24186-2022 Table 6. Impact testing applies only to D/E grades. Brinell hardness (370~430 HBW) is the guaranteed property for standard NM400.
🔬 Impact specimen size (per 7.4.2.4): Standard specimen 10mm × 10mm × 55mm. When insufficient to prepare standard specimen, 7.5mm × 10mm × 55mm or 5mm × 10mm × 55mm specimens shall be used.
⚙️ Delivery condition: quenched; quenched+tempered; TMCP+tempered; tempered or hot rolled (as agreed).

⚙️ Technical requirements (GB/T 24186-2022)

7.1.2 On the premise of ensuring the steel properties, the alloying elements Cr, Ni, Mo specified in Table 2 and Table 3 may be added individually or in combination. Other alloying elements not specified in Table 2 and Table 3 may also be added. Their alloying elements and contents shall be indicated in the quality certificate.

7.1.3 When Cu is present as a residual element in the steel, its content shall not be greater than 0.30%; the As content shall not be greater than 0.08%. If the supplier can guarantee it, analysis is not required.

7.1.4 The carbon equivalent of steel requiring low-temperature toughness shall comply with the requirements of Table 3. The carbon equivalent is calculated according to formula (1):
CEV = C + Mn/6 + (Cr+Mo+V)/5 + (Cu+Ni)/15

7.1.5 When using total aluminum (Alt) content calculation, the Alt content shall not be less than 0.015%, and for steel requiring low-temperature toughness (D/E grades), the Alt content shall not be less than 0.020%.

7.1.6 After negotiation between the supplier and the buyer and specified in the contract, the chemical composition of TiC-reinforced steel shall comply with Appendix A.

7.1.7 When the buyer requires finished product chemical composition analysis, the allowable deviation of the finished product chemical composition shall comply with the provisions of GB/T 222.

7.2 Smelting method
The steel shall be smelted in a converter or electric furnace and subjected to ladle refining.

7.3 Delivery condition
The steel shall be delivered in the quenched, quenched + tempered, TMCP + tempered condition, or in the hot-rolled condition (hot-rolled steel before heat treatment).

🔧 Bend Test (Optional, per GB/T 24186-2022 Table 7)

When specified in the contract, 90° bend test using transverse specimen, D=6a (D: bending pin diameter, a: specimen thickness). Applicable for thickness >4mm. Not applicable to NM550, NM600 and above.

⚖️ NM400 vs AR400 / Hardox 400 — Global Grade Comparison

Parameter NM400 (China GB/T 24186) AR400 / Hardox 400 Comparison
Surface Hardness (HBW) 370~430 (≤80mm)
360~440 (>80~120mm)		 360~440 Equivalent range
Tensile Strength (MPa) ≥1200 (optional) ≥1200 Equivalent
Elongation (%) ≥10 (optional) ≥10 Equivalent
Impact Toughness (D/E grade) ≥24J (-20°C / -40°C) ≥20J (-40°C typical) Comparable or better
Carbon Equivalent (CEV) 0.57~0.67 (D/E grade) 0.55~0.65 Similar weldability
Typical Applications Mining, construction, heavy machinery, wear liners Same applications globally Fully interchangeable
⏱️
Service Life Extension
Field data indicates NM400 extends service life by 500%~700% in severe sliding abrasion applications compared to structural steel, directly reducing maintenance frequency and component replacement intervals.
💰
Total Cost of Ownership
Despite higher procurement cost, the total cost of ownership is 50%~70% lower for NM400 in high-wear environments due to extended operational life and reduced downtime.
🏗️
Design Consideration
Select NM400 standard for extreme wear, or NM400D/E when low-temperature impact is required. For heavy section >80mm, hardness range is 360~440 HBW.

📋 Standards and Inspection — GB/T 24186-2022

📄
Applicable Standard
GB/T 24186-2022
Engineering machinery high strength abrasion resistant steel plate and strip
🔍
Inspection Items (per Table 8)
  • Chemical composition (1 sample per heat)
  • Surface Brinell hardness (1 sample per batch) — 370~430 HBW (≤80mm) / 360~440 HBW (>80~120mm)
  • Impact test for D/E grades (3 samples per batch) — ≥24J (test temperature -20°C for D / -40°C for E)
  • Flatness — Class H per GB/T 709-2019 (or L / PF.A by agreement)
🎯
Sampling & NDT
Sampling: One sample per 60 tons max. per batch.
NDT: Available upon agreement — standard and acceptance level to be specified in contract.

🔥 Welding & Processing Notes — Practical Guidelines

✅ Weldability
Acceptable with low-hydrogen process (SMAW, GMAW, FCAW).
Consumables: ISO 18275 E69X X X / AWS A5.5 E11018M.
HAZ hardness limit: ≤400 HBW for field welding.
🌡️ Preheat Requirement
Required for thickness ≥20mm.
Minimum preheat: 150°C~200°C (CEV ~0.57 max)
Interpass temperature: ≤250°C
For restrained joints: up to 200°C.
✂️ Cutting Methods
• Plasma cutting (recommended ≤50mm)
• Laser cutting (≤20mm)
• Abrasive waterjet — minimal HAZ
• Oxy-fuel — acceptable with preheat, hardened edge up to 3mm
🛠️ Post-cut treatment: HAZ removal by grinding is recommended if subsequent bending or forming is required. Stress relief at 550°C~600°C for 2 hours if dimensional stability is critical.
📘 NM400 / NM400D / NM400E Approximate Grade Lookup Table →
📄 NM400 / NM400D / NM400E technical data sheet — CEHE Steel — Compiled from GB/T 24186-2022
Mill test certificates available upon request. Third-party inspection accepted.