What is ASTM A516 Gr.70?
ASTM A516 Grade 70 is a carbon steel plate standard designed for moderate to low-temperature pressure vessel applications. It is published by ASTM International, with the corresponding ASME standard being SA516 Gr.70.
The "70" represents its minimum tensile strength: 70 ksi (approximately 482 MPa).
It belongs to the "Carbon-Silicon-Manganese" steel family. Its core purpose is to solve a critical engineering problem: ensuring that the steel plate maintains excellent impact toughness at low temperatures after welding, preventing brittle fracture. Simply put, this steel was born for safety.
| Element | Content (%) | Function |
|---|---|---|
| Carbon (C) | ≤ 0.30 | Ensures strength/hardness, but limited for weldability |
| Manganese (Mn) | 0.79 – 1.30 | Increases strength and toughness; deoxidizer |
| Silicon (Si) | 0.13 – 0.45 | Deoxidizing agent during steelmaking |
| Phosphorus (P) | ≤ 0.035 | Harmful impurity; strictly controlled for toughness |
| Sulfur (S) | ≤ 0.035 | Harmful impurity; controlled to prevent hot shortness |
| Property | Value | Interpretation |
|---|---|---|
| Tensile Strength | 485 – 620 MPa | High safety margin for high-pressure vessels |
| Yield Strength | ≥ 260 MPa | Point where permanent deformation begins |
| Elongation (2 inches) | ≥ 21% | Good plasticity; provides warning before fracture |
| Impact Toughness | Good (customizable down to -46°C) | Core advantage – remains tough in cold climates |
Why Choose A516 Gr.70? Key Advantages
Among many pressure vessel steels, A516 Gr.70 stands out due to four major advantages
Excellent Weldability
Pressure vessel fabrication relies on welding. A516 Gr.70's low Carbon Equivalent (CE) design provides excellent crack resistance. Even without complex preheating, common welding processes (SMAW, GTAW, SAW) produce high-quality welds, significantly reducing fabrication costs and difficulty.
Superior Low-Temperature Toughness
This is the key difference between A516 Gr.70 and ordinary carbon steels (e.g., Q235B). Many pressure vessels operate in sub-zero environments (e.g., LNG storage). A516 Gr.70 maintains high impact energy absorption at low temperatures, preventing brittle, "glass-like" fracture.
Global Certifications & Traceability
A516 Gr.70 meets internationally recognized ASME codes and is a specified material for global engineering firms (Shell, ExxonMobil, Fluor, etc.). Reputable suppliers provide complete EN 10204 Type 3.2 mill certificates, ensuring full traceability from melting to delivery.
Good Workability
Whether rolling, dishing heads, or machining, A516 Gr.70 performs consistently. Its moderate hardness does not excessively wear out cutting tools.
Common Applications
If your industry involves the following equipment, A516 Gr.70 will likely be specified in the technical datasheet
Petrochemical
Refinery towers, reactors, heat exchanger shells, separators.
Power Generation
Utility boiler drums, steam generation equipment.
Industrial Gases And Process Industry
Large oxygen, nitrogen, and argon cryogenic storage tanks
Spherical tanks for propylene, LPG (liquefied petroleum gas), and other media.
Comparison: A516 Gr.70 vs. Alternatives
| Feature | ASTM A516 Gr.70 | GB/T 713 Q345R (Common Alternative) |
|---|---|---|
| Standard | International (ASME) | Chinese National Standard |
| Yield Strength | ≥ 260 MPa | ≥ 345 MPa (Stronger) |
| Low-Temp Impact | Excellent down to -46°C | Typically 0°C or -20°C (by agreement) |
| Weldability | Superior (Low CE) | Good (Higher CE due to higher strength) |
| Global Acceptance | Very High | Mostly used for domestic Chinese projects |
| Verdict | Preferred for safety & cold environments | Consider for ambient temperature, high-strength needs |
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Frequently Asked Questions (FAQs) About A516Gr70
01.What is the difference between A516 Gr.70 and A516 Gr.70N?
A516 Gr.70 (As-Rolled): The plate is supplied in its "as-manufactured" state without additional heat treatment. It is typically used for thinner plates (under 40mm) where low-temperature impact testing is not required.
A516 Gr.70N (Normalized): The plate undergoes a normalizing heat treatment (heating and cooling in air). This refines the grain structure, significantly improving low-temperature toughness and uniformity.
Industry Best Practice: Even if the standard doesn't strictly require it, most critical pressure vessel applications (especially those involving freezing temperatures or welding) specify Gr.70N for guaranteed safety and compliance with ASME codes.
02.Can A516 Gr.70 be used for cryogenic (very low temperature) service?
Yes, but with limitations. A516 Gr.70 is considered a low-temperature carbon steel, not a true cryogenic steel (like 304 Stainless or 9% Nickel steel).
Typical Impact Test Temperature: As low as -46°C (-50°F) , provided it is in the Normalized condition and passes the required Charpy V-Notch (CVN) impact tests.
Limitation: Below -46°C, carbon steel becomes too brittle. For liquid nitrogen (-196°C) or LNG (-162°C) primary containment, you would need austenitic stainless steel or specialized nickel alloys.
Recommendation: Always specify the required design temperature (MDMT) on your purchase order.
03.Is A516 Gr.70 the same as Q345R? Can they be used interchangeably?
No, they are not identical. While both are used for pressure vessels, there are critical differences:
| Feature | A516Gr70 (ASME) | Q345R (GB/T 713) |
|---|---|---|
| Yield Strength | 260 MPa (Lower) | 345 MPa (Higher) |
| Low-Temp Toughness | Superior (tested down to -46°C) | Standard at 0°C or -20°C |
| Global Acceptance | High (accepted worldwide) | Low (mainly China) |
Verdict for Sourcing: You cannot automatically substitute Q345R for A516 Gr.70 on an international project. Most engineering firms strictly require ASME materials like A516 Gr.70 to meet insurance and regulatory codes (e.g., ASME BPVC Section VIII).
04.What welding procedures are recommended for A516 Gr.70?
A516 Gr.70 is known for its excellent weldability due to its low carbon content. Common welding processes include:
SMAW (Stick): Using electrodes like E7018 (low hydrogen)
GTAW (TIG): For thinner sections and root passes
SAW (Submerged Arc): For long, straight seam welds on heavy plates
Key Recommendations:
Preheating: Typically not required for plates under 25mm at room temperature, but a minimum preheat of 95-120°C (200-250°F) is recommended for thicker sections or high restraint joints.
Low Hydrogen: Always use low-hydrogen welding consumables to prevent cold cracking.
Post-Weld Heat Treatment (PWHT): Required by ASME code for thicknesses above approximately 38mm (1.5 inches) to relieve residual stresses.
Need a recommended WPS (Welding Procedure Specification) for your project? Contact our technical team.
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