A516 Grade 70 vs A572 Grade 50 Comparison

A516 Grade 70 is a pressure-vessel carbon steel plate chosen for welded vessels that require good notch toughness; A572 Grade 50 is a high-strength, low-alloy structural plate optimized for weight-sensitive structural builds. For pressure containment, pick A516-70; for structural framing where higher yield is beneficial, pick A572-50.

Below are typical composition windows for design and procurement checks. Exact limits depend on the mill certificate and thickness.

A516 Grade 70 (typical composition ranges)

Carbon (C): ~0.26% (varies)

Manganese (Mn): ~0.85–1.20%

Phosphorus (P): max ~0.03–0.04%

Sulfur (S): max ~0.03–0.05%

Silicon (Si): trace to ~0.35%
Notes: manufacturers optimize chemistry to meet notch toughness requirements.

A572 Grade 50 (typical composition limits)

Carbon (C): max ~0.23%

Manganese (Mn): up to ~1.35%

Phosphorus (P): max ~0.03–0.04%

Sulfur (S): max ~0.03–0.05%

Silicon (Si): 0.15–0.40% typical

Small additions of columbium (niobium) or vanadium sometimes present for strength control.

Important procurement note: request Mill Test Report (MTR / EN 10204 3.1) to verify chemical limits for the batch being shipped.

A516 Grade 70

Typical minimum yield: around 260–300 MPa depending on thickness and heat treatment.

Typical tensile: ~485–620 MPa (ultimate).

Charpy impact: notch toughness requirements commonly specified for pressure-vessel service; mill practice often includes impact testing at specified temperatures.

A572 Grade 50

Minimum yield: 345 MPa (50 ksi).

Tensile strength: typical range 450–620 MPa depending on grade and thickness.

Toughness: good weldability; impact testing requirements depend on project specs but not always as stringent for pressure containment.

Practical implication: when brittle fracture risk is a major design concern for pressure equipment, A516-70 is usually preferred because of its certified notch toughness behavior. When structural members require higher yield to reduce section sizes, A572-50 often wins.

When to choose A516 Grade 70

Pressure vessels, boilers, and liquid storage where vessel codes require PVQ steels.

Environments with cyclic loading where notch toughness matters.

Projects where ASME Section II/Section VIII specifications or equivalent are invoked.

When to choose A572 Grade 50

Building frames, bridges, cranes, heavy machinery rails, and structural elements where higher yield reduces weight.

Projects focusing on structural codes and weldment strength.

Hybrid use cases occur: structural members that interface with pressure parts should be specified carefully to meet both strength and toughness needs.

Fabrication, welding, heat treatment, and toughness considerations

Weld procedures and preheat/postweld heat treatment should be decided from the specification and project code. Short practical notes:

• A516-70 fabrication: preheat and PWHT (post-weld heat treatment) decisions hinge on thickness, carbon equivalent (CE), and design temperature. Pressure vessel codes often require impact testing at design temperature.
• A572-50 fabrication: better out-of-the-box weldability. Preheat may not be required for thinner sections. Avoid aggressive heat input that could reduce local toughness.

Ask your welding engineer to compute carbon equivalent (CE) for any large weldment to determine need for preheat or PWHT.

What is ASTM A516 Grade 70 equivalent to?

ASTM A516 Grade 70 ≈ ASME/SA516 Grade 70 (same spec) and is most commonly treated as approximately equivalent to EN pressure-vessel grades such as P355GH / P355NH (EN 10028). Other regional near-matches frequently cited are BS 1501 224-490 A/B, 16Mo3 (for some high-temp uses) and Chinese Q345R for general pressure-vessel applications - but these are only approximate equivalents.

What is ASTM A572 GR 50 equivalent to?

ASTM A572 Grade 50 ≈ EN S355 (commonly S355JR / S355J2), and is also commonly treated as roughly equivalent to Chinese Q345B, JIS SM490/SS490, DIN St52-3 and other 345-MPa class structural steels.

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