GB/T11251 1345 Alloy Structural Steel Plate

GB/T11251 1345 Alloy Structural Steel Plate Material Overview & Core Advantages‌ GB/T 11251 1345 alloy steel plates deliver ‌650 MPa+ yield strength‌ for mining equipment and rail vehicle components, combining ‌boron-enhanced hardenability‌ with ‌water-cooling stable toughness‌. These hot-rolled plates achieve HRC 28–32 surface hardness while maintaining 16% elongation (50B grade). ‌Key Differentiators‌: ‌Wear Resistance‌: 3x higher than AISI 1045 under abrasive conditions. ‌Global Equivalency‌: ASTM A534 (45Mn2), DIN 17200 46Mn7 (27SiMn). ‌Processing Flexibility‌: 85% cold-forming capability without edge cracking.

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‌GB/T11251 1345 Alloy Structural Steel Plate Material Overview & Core Advantages‌

GB/T 11251 1345 alloy steel plates deliver ‌650 MPa+ yield strength‌ for mining equipment and rail vehicle components, combining ‌boron-enhanced hardenability‌ with ‌water-cooling stable toughness‌. These hot-rolled plates achieve HRC 28–32 surface hardness while maintaining 16% elongation (50B grade).

‌Key Differentiators‌:

  • ‌Wear Resistance‌: 3x higher than AISI 1045 under abrasive conditions.
  • ‌Global Equivalency‌: ASTM A534 (45Mn2), DIN 17200 46Mn7 (27SiMn).
  • ‌Processing Flexibility‌: 85% cold-forming capability without edge cracking.

‌Technical Specifications‌

‌1. Chemical Composition (GB/T 11251-2023 Revision)‌

Grade C Range Mn Range B Range CEV*
45Mn2 0.42–0.49% 1.40–1.80% 0.68
40B 0.37–0.44% 0.60–0.90% 0.0005–0.0035% 0.54
50B 0.47–0.55% 0.60–0.90% 0.0005–0.0035% 0.72

*CEV = C + Mn/6 + (Cr + Mo + V)/5

‌2. Mechanical Performance‌

Grade Yield (MPa) Tensile (MPa) Elongation (%) Impact (-20°C)
45Mn2 ≥600 850–1000 13 45 J
40B ≥500 700–850 20 55 J
50B ≥550 900–1100 16 35 J

‌Physical Properties‌:

  • Thermal Conductivity: 45.6 W/m·K (20–300°C)
  • Linear Expansion: 12.8 µm/m°C (25–200°C)

‌Manufacturing & Processing‌

‌1. Heat Treatment‌

  • ‌Quenching‌: 830–860°C water cooling (45Mn2/50B).
  • ‌Tempering‌: 550–600°C × 2h (prevents white spot defects).

‌2. Machinability‌

Process Parameter Surface Finish (Ra)
Turning 180–220 m/min 3.2–6.3 µm
Grinding 35 m/s wheel speed 0.8–1.6 µm

‌Industrial Applications‌

‌1. Heavy Machinery‌

  • ‌Crusher Hammers‌: 50B grade (hardness HRC 32–35).
  • ‌Excavator Pins‌: 45Mn2 with 50–55 HRC surface.

‌2. Transportation Equipment‌

Component Material Grade Service Life
Rail Axles 27SiMn 1.2M km
Gear Blanks 40B 80,000h

‌3. Energy Sector‌

  • ‌Wind Turbine Shafts‌: 50B (IEC 61400-6 certified).
  • ‌Hydraulic Cylinders‌: 40B (ISO 6020/2 compliant).

‌Quality Compliance‌

  1. ‌Testing Protocols‌:
    • Ultrasonic inspection: GB/T 2970 Class II.
    • Hydrogen content: <2ppm (prevent white spots).
  2. ‌Certifications‌:
    • China Compulsory Certification (CCC).
    • ISO 630:2019 structural steel compliance.

‌Delivery & Storage‌

  • ‌Dimensions‌:
    • Width: 1,500–3,200mm (max length: 18m).
    • Thickness Tolerance: ±0.2mm (ground edges).
  • ‌Packaging‌: Rust-inhibitive oil + PE wrapping.

‌Welding Guidance‌: Use GB/T 5117 E6013 electrodes with 150–180°C preheat*


Technical Footnotes‌:

  1. 40B achieves 0.2% proof strength of 420 MPa @ 150°C.
  2. Maximum service temperature: 350°C (prolonged exposure).

‌Why Choose GB/T 11251 1345?
Compared to SAE 4340, 50B grade provides 15% higher surface hardness while maintaining equivalent impact toughness. The boron microalloying (0.0035% max) enhances hardenability depth by 40% in oil-quenched components.


‌Environmental Note‌: 88% recycled content with 6.8kg CO₂/t production footprint (GB 17167-2012).


‌Global Material Equivalents‌:

GB/T 11251 ASTM DIN JIS Application Focus
45Mn2 1345 46Mn7 SCMn3 Mining Equipment
27SiMn 27MnSi5 High-Stress Fasteners
50B 50B46H 50B2 SB49 Gear Shafts

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