Q420DR Low Temperature Pressure Vessel Steel Plate

Product Definition and Standard

This is a high-strength low-alloy steel plate grade for low-temperature pressure vessels under Chinese national standards, with specified minimum yield strength of 420 MPa.

In practical engineering applications, Q420DR is commonly used for large low-temperature pressure vessels, LNG storage tanks, ammonia storage tanks, petrochemical reactors, energy storage systems, and other critical pressure components operating at low temperatures. It offers a superior combination of high strength and reliable low-temperature toughness for demanding cryogenic service conditions.

Manufacturing standards: GB/T 713.3-2023

Ultrasonic testing standards: NB/T 47013.3-2023

Q420DR Low Temperature Pressure Vessel Steel Plate Equivalent Standards

GB/T: Q420DR

EN 10028-3: P420NL1 / P420NL2 (approximate equivalence)

ASTM / ASME: SA537 Class 1/2 (for reference, not identical)

Mechanical Properties and Weldability

Q420DR offers an excellent combination of high strength (minimum yield strength 420 MPa) and outstanding low-temperature impact toughness, ensuring reliable performance under cold service conditions and effectively reducing the risk of brittle fracture. Its refined chemical composition and controlled carbon equivalent provide good weldability and low crack sensitivity, allowing it to be processed using standard welding procedures commonly applied in high-strength pressure vessel fabrication. With a stable balance of strength, ductility and toughness, Q420DR ensures dependable mechanical performance for long-term service under high pressure and low temperature conditions.

Key Advantages of Q420DR Steel Plate

✅ High Strength

Minimum yield strength of 420 MPa allows for reduced wall thickness and lighter weight in pressure vessel design.

✅ Excellent Low-Temperature Impact Toughness

Maintains stable impact performance at -40°C, with mandatory side expansion value measurement (≥0.53 mm) to ensure sufficient toughness.

✅ Good Weldability

Controlled chemical composition and microalloying (V, Nb) ensure good weldability and low crack sensitivity.

✅ Stable Mechanical Properties

Balanced strength, ductility and toughness for long-term pressure service.

Applicable Standard

GB/T 713.3 – Steel Plates for Low Temperature Pressure Vessels

Mill Test Certificate: EN 10204 3.1

Third-party inspection available (SGS, BV, TUV)

Typical Applications

Delivery Condition

Normalizing or Normalizing + Tempering

For thickness >36 mm, normalizing (with accelerated cooling allowed) + tempering is available upon agreement.

Available Dimensions Of Q420DR Steel Plate

Thickness: 6 – 120 mm (per GB/T 713.3-2023)

Width: up to 5200 mm

Length: up to 12000 mm

Quality Control & Testing

• Chemical composition analysis
• Mechanical property testing
• -40°C Charpy V-notch impact test (with side expansion value measurement)
• Ultrasonic testing (UT) – 100% for thickness ≥6 mm

🔬 Role of Each Element in Steel Plate

• Carbon (C) : ≤0.20% — Increases strength but reduces plasticity and weldability. Controlled below 0.20% to ensure good weldability and low-temperature toughness.
• Silicon (Si) : 0.15~0.50% — Deoxidizer, strengthens ferrite. Excessive content may reduce low-temperature toughness and weldability.
• Manganese (Mn) : 1.30~1.70% — Solid-solution strengthening, improves strength and toughness, refines pearlite, enhances low-temperature impact properties.
• Nickel (Ni) : 0.30~0.80% — Significantly improves low-temperature toughness, lowers ductile-to-brittle transition temperature; an important alloying element for cryogenic steels.
• Molybdenum (Mo) : ≤0.08% — Increases hardenability, improves high-temperature strength; microalloying contributes to grain refinement.
• Vanadium (V) : 0.05~0.15% — Microalloying element for precipitation strengthening and grain refinement, enhances strength and toughness.
• Niobium (Nb) : 0.015~0.050% — Grain refiner, improves strength and toughness through precipitation strengthening.
• Nitrogen (N) : ≤0.020% — Forms nitrides with aluminum to refine grains, but free nitrogen deteriorates low-temperature toughness; strictly controlled.
• Phosphorus (P) / Sulfur (S) : ≤0.018% / ≤0.008% — Tightly controlled impurities. Phosphorus causes cold brittleness, sulfur leads to hot shortness, both reduce low-temperature impact toughness and weldability.

💡 Summary: Q420DR achieves high strength and excellent -40°C low-temperature impact toughness through microalloying with V, Nb and Ni, combined with strict control of C, P, S and N.

Reasons for recommending our company's Q420DR steel plate

• Professional experience in high-strength pressure vessel steel supply
• Stable sourcing from qualified mills with full traceability
• Export-oriented service and fast response
• Technical support for material selection and substitution

1. What is the minimum service temperature of Q420DR?

According to GB/T 713.3-2023, Q420DR is impact tested at -40°C and suitable for pressure vessels with a minimum design temperature of -40°C.

2. What is the side expansion value requirement for Q420DR?

Per 7.4.3 of GB/T 713.3-2023, Q420DR impact specimens shall have a side expansion value of not less than 0.53 mm.

3. What European standard grade is equivalent to Q420DR?

Q420DR approximately corresponds to P420NL1 / P420NL2 in EN 10028-3, with similar strength level and low-temperature impact requirements.

4. Does Q420DR require ultrasonic testing?

Yes. According to 7.6.1, Q420DR plates of thickness ≥6 mm shall be 100% ultrasonically tested per NB/T 47013.3, with acceptance level not less than Level I.

5. Can Q420DR replace 16MnDR?

Q420DR has higher yield strength (420 MPa vs 315 MPa for 16MnDR) and higher impact energy requirement (60J vs 47J at -40°C). It can replace 16MnDR in applications requiring higher strength, but design and welding procedures should be re-evaluated accordingly.

6. What welding consumables are recommended for Q420DR?

Low-hydrogen welding consumables with -40°C impact toughness qualification are required. E5018 (SMAW) or equivalent Ni-alloyed wires are recommended to match the strength and toughness of Q420DR.

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