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

1. Q390B Steel Plate

• Quality Grade: Grade B (requirement for impact toughness at room temperature)
• 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, impact energy at room temperature ≥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)

2. Q390NB Steel Plate

• Quality Grade: Grade D (requirement for low-temperature impact toughness)
• Production Process: Must be normalized or normalized rolled (designation "N")
• Core Characteristics:
  • Low-Temperature Toughness: Impact energy at -20°C ≥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

3. Q390MC Steel Plate

• Quality Grade: Grade C (requirement for impact toughness at 0°C)
• 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