1. Core Manufacturing Process

1. Raw Material Preparation: High-purity low-carbon steel scrap + alloy additions (Cr, Mo, Mn) – sourced to meet GB/T 24186 chemical composition limits (e.g., P≤0.025%, S≤0.015%).
2. Smelting: Electric Arc Furnace (EAF) or Basic Oxygen Furnace (BOF) melting + vacuum degassing to remove impurities (O₂, H₂) and ensure chemical uniformity.
3. Continuous Casting: Molten steel cast into slabs (thickness 150–300mm); homogenization annealing (850–900°C for 4–6 hours) to eliminate segregation.
4. Hot Rolling: Slabs heated to 1150–1250°C; hot-rolled to target thickness (6–100mm) with controlled rolling to refine grain structure.
5. Quenching: Rapid cooling (water spray or air blast) from 900–950°C to form martensitic microstructure – critical for high hardness.
6. Tempering: Reheated to 500–600°C (varies by grade) to reduce residual stress and improve ductility; avoids brittleness while retaining wear resistance.
7. Surface Treatment: Shot blasting (Sa 2.5 standard) to remove oxide scale; optional anti-rust coating for storage/transport.

2. Strict Quality Control (GB/T 24186-2022 Mandatory Requirements)

• Chemical Testing: Spectrometric analysis (GB/T 4336) for each production batch to verify alloy content; carbon equivalent (CEV) calculation to ensure weldability.
• Mechanical Testing:
  • Tensile, bend, and elongation tests (GB/T 228.1) for strength/ductility verification.
  • Brinell hardness testing (GB/T 231.1) – 3 points per plate, with hardness variation ≤30 HB.
  • Impact testing (GB/T 229) – Charpy V-notch at 20°C (minimum 16J for NM600).
• Non-Destructive Testing (NDT):
  • Ultrasonic Testing (UT): 100% thickness inspection and internal flaw detection (GB/T 6402) – Class B or higher.
  • Magnetic Particle Testing (MT): Surface flaw detection on edges and cut surfaces (GB/T 9444) for plates >20mm.
• Dimensional Inspection: Laser measurement for thickness (tolerance ±0.5mm), flatness, and straightness (GB/T 709).
• Material Test Report (MTR): GB/T 247 equivalent to EN 10204 3.1 certification – mandatory for industrial supply.

3. Supply Chain & 2025 Pricing Analysis

• Minimum Order Quantity (MOQ):
  • Standard thicknesses (10–30mm): 10 tons per grade.
  • Thick plates (>50mm) or NM550/NM600: 20 tons per grade.
• Delivery Lead Time:
  • Stock grades (NM400/NM500): 15–20 days (ex-works China).
  • Custom thicknesses or premium grades (NM550/NM600): 30–45 days.
  • Export (FOB Shanghai/Tianjin): +7–10 days for logistics.
• Packaging: Seaworthy export packaging – steel bundles + wooden skids + moisture-proof film; plates >50mm with anti-deformation supports.
• 2025 Q4 Pricing (USD/ton):

• Pricing Drivers:
  • Alloy Content: NM600 costs 40–60% more than NM400 due to higher Cr/Mo additions.
  • Thickness: Plates >50mm cost 25–30% more than 10mm plates (rolling complexity).
  • Certification: 3.2 MTR adds 10–15% vs. 3.1 certification.
  • Order Volume: Bulk orders (≥50 tons) unlock 10–15% discounts.

4. Value-Added Services

• Precision cutting (plasma, laser, waterjet) to custom dimensions (tolerance ±1mm).
• Welding support: Pre-heat guidelines (200–250°C for NM550/NM600) and matching welding consumables.
• Heat treatment optimization: Custom tempering for specific wear/impact requirements.
• Third-party testing (SGS/BV/TÜV) for international projects.

5. Global Supply Hubs