Q390B, Q390NB, and Q390MC are all high-strength low-alloy structural steels (GB/T 1591-2018 standard). Their main differences lie in quality grade, production process, performance characteristics, and application scenarios. A detailed comparison is as follows:

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1. Q390B Steel Plate

• Quality Grade: Grade B (room temperature impact toughness requirement)
• Production Process: Can be produced by hot rolling, normalizing, or thermomechanical controlled processing (TMCP)
• Core Characteristics:
  • Mechanical Properties: Yield strength ≥390MPa, tensile strength 490–650MPa, room temperature impact energy ≥34J
  • Composition Features: Contains microalloying elements (niobium, vanadium, titanium), carbon equivalent ≤0.45%, good weldability
• Typical Applications:
  • Building steel structures, engineering machinery (crane booms, excavator chassis)
  • Heavy-duty structural components for conventional temperature environments (above -20°C)

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2. Q390NB Steel Plate

• Quality Grade: Grade D (low-temperature impact toughness requirement)
• Production Process: Must be normalized or normalized rolled (designation "N")
• Core Characteristics:
  • Low-Temperature Toughness: -20°C impact energy ≥34J, suitable for cold regions
  • Composition Optimization: Addition of niobium (Nb: 0.01–0.05%) and vanadium (V) to refine grains and improve strength-toughness balance
• Typical Applications:
  • Bridges in cold regions, wind power tower sections, low-temperature pressure vessels
  • Heavy equipment requiring high low-temperature crack resistance

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3. Q390MC Steel Plate

• Quality Grade: Grade C (0°C impact toughness requirement)
• Production Process: Thermomechanical controlled processing (TMCP) (designation "M")
• Core Characteristics:
  • Balanced Strength and Toughness: Finer grains, simultaneous improvement in strength and toughness, yield strength ≥390MPa
  • Welding Advantages: Low carbon equivalent (≤0.40%), low cold cracking susceptibility
  • Environmental and Energy Efficiency: TMCP process eliminates the need for normalizing heat treatment, reducing energy consumption
• Typical Applications:
  • Shipbuilding, offshore platforms, high-pressure pipelines
  • Lightweight structures requiring high-precision forming

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Summary of Key Differences Among the Three

Characteristic	Q390B	Q390NB	Q390MC
Quality Grade	Grade B (room temperature toughness)	Grade D (-20°C toughness)	Grade C (0°C toughness)
Process Requirement	Hot rolling/Normalizing/TMCP	Normalizing or normalized rolling	Thermomechanical controlled processing (TMCP)
Impact Temperature	≥Room temperature	≥-20°C	≥0°C
Core Advantage	High cost-effectiveness, strong versatility	Excellent low-temperature crack resistance	Good strength-toughness balance, easy welding
Applicable Scenarios	Conventional construction machinery	Engineering in cold regions	Marine/high-pressure vessels

Additional Notes

• Composition Differences: Q390NB/Q390MC have stricter control of phosphorus and sulfur impurities (P≤0.030%, S≤0.025%), resulting in higher purity.
• Process Impact: TMCP (Q390MC) achieves fine-grained structure directly through controlled rolling and cooling, while normalizing (Q390NB) requires additional heat treatment.

In summary, Q390B is suitable for room temperature heavy-duty structures, Q390NB focuses on low-temperature toughness, and Q390MC achieves high performance and lightweight design through TMCP process

High-strength coil	11.5	Q390NB		1500	1	28.49
High-strength coil	7.5	Q390NB		1600	1	28.76
High-strength coil	11.5	Q390NB		1500	1	28.75
High-strength coil	11.5	Q390NB		1500	1	28.25
High-strength coil	11.5	Q390NB		1500	1	28.9
High-strength coil	11.5	Q390NB		1500	1	28.85
High-strength coil	11.5	Q390NB		1500	1	28.9
High-strength coil	4.5mm	Q390NB		1500	1	28.93
High-strength coil	4.5mm	Q390NB		1500	1	29