Both ASTM A612 and ASTM A516 Gr 70 are carbon steel plates intended for use in boilers and pressure vessels (PVQ). A516 Gr 70 is suitable for general-purpose, thick-walled pressure vessels that require excellent low-temperature notched toughness. A612, on the other hand, is used for vessels requiring higher strength and thinner walls, which can achieve extremely high strength without the need for high-intensity preheating.
Key Specifications
| Feature | ASTM A612 | ASTM A516 Grade 70 |
|---|---|---|
| Primary Application | High-pressure, low-temperature moderate-thickness vessels | Moderate & lower-temp pressure vessels (boilers, tanks) |
| Thickness Limit | Up to 1 inch (25.4 mm) | Up to 8 inches (203.2 mm) |
| Condition | Typically as-rolled or normalized for toughness | Always normalized for plates over 1.5 inches thick |
| Carbon (Max) | 0.29% | 0.28% |
| Manganese | 0.92% - 1.62% | 0.79% - 1.30% |
Core Comparison: ASTM A612 vs. A516 Gr 70
| Characteristic | ASTM A516 Grade 70 | ASTM A612 |
|---|---|---|
| Material Positioning | Carbon steel plate for medium and low temperature service (most standard, universal) | High strength carbon-manganese-silicon killed steel for medium and low temperature service |
| Yield Strength (min) | Approx. 260 MPa (38 ksi) | Approx. 345 MPa (50 ksi) - significantly higher |
| Tensile Strength | 485 - 620 MPa (70 - 90 ksi) | 560 - 700 MPa (81 - 101 ksi) |
| Maximum Thickness Limit | Typically up to 200mm and above | Typically limited to 25mm (1 inch) and below |
| Delivery Condition | Normalizing required for thickness >40mm, as-rolled condition available for smaller thickness | Must be normalized (Normalized) |
| Main Applications | Various boilers, reactors, general storage tanks | LPG tank trucks, liquid ammonia storage tanks, high-pressure thin-walled vessels |
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Why Choose ASTM A612 Steel Plates for Pressure Vessels?
When compared to A516 Gr 70, A612's core competitive advantage lies in its "high strength-to-weight ratio".
Significant Weight Reduction: A612 has a yield strength approximately 30% higher than that of A516 Gr 70. This means that under the same design pressure, A612 allows for the design of thinner walls. For mobile pressure vessels (such as LPG transport tanks), weight reduction directly translates to increased cargo capacity and improved fuel economy.
Superior Compressive Strength: Due to its higher manganese (Mn) content (up to 1.50%) and fine-grain treatment, A612 provides a stronger matrix capable of withstanding higher stresses while maintaining good toughness.
Designed for Thin Sheets: A612 is specifically optimized for thicknesses of 1 inch (25 mm) and below. Within this thickness range, its overall mechanical properties outperform those of A516.
Good Low-Temperature Toughness: Although both grades are suitable for medium- and low-temperature applications, A612-as a killed steel that must be normalized-exhibits very stable low-temperature impact toughness, making it particularly well-suited for environments involving liquefied gases.
Direct Comparison: When to Choose Which?
| Decision Factor | Choose ASTM A612 | Choose A516 Gr.70 |
|---|---|---|
| Design Pressure | High (≥10 MPa) | Medium (2-10 MPa) |
| Service Temperature | -40°C to 300°C | -10°C to 400°C |
| Cost Sensitivity | Low (prioritize performance) | Medium (balance cost & performance) |
| Key Requirement | Low-temperature toughness + high strength | Versatility + weldability |
ASTM A612 is the top choice for high-pressure, low-temperature, safety-critical projects (e.g., LNG, offshore) where strength and toughness are non-negotiable.
A516 Gr.70 is the most cost-effective all-around solution for most pressure vessel applications, offering broad compatibility with global standards and processing requirements.
When to select ASTM A612:
- High design pressure, but wall thickness needs to be controlled (typically within 25 mm).
- Equipment that needs to be moved frequently (such as tank trucks) and is highly sensitive to its own weight.
- High strength guaranteed in the normalized condition.
When to select ASTM A516 Gr 70:
- Wall thickness exceeds 25 mm.
- The project is highly sensitive to material costs (A516 is typically slightly less expensive than A612 and is more readily available in stock).
- Conventional, stationary large storage tanks or reactors.
- A simpler welding procedure qualification is required (A516 is extremely widespread, and most factories have established data available).
Typical Use Cases：ASTM A612 vs A516 Gr 70 Steel Plates
Typical Applications for ASTM A612
- Liquefied Petroleum Gas (LPG)/Liquid Ammonia Transport Tank Trucks
- High-Pressure Gas Cylinders and Portable Containers
- Air Compressor Storage Tanks
Typical Applications for ASTM A516 Gr 70
- Large Petrochemical Reactors
- Power Plant Boiler Drum
- Large Crude Oil/Refined Oil Storage Tanks
Considerations for Welding and Heat Treatment
Welding Performance
Strength Matching: A516 Gr 70 is typically paired with E7018-grade welding consumables; however, due to its higher tensile strength, A612 is recommended to be paired with E8018-series high-strength steel welding consumables to ensure that the weld strength is not lower than that of the base metal.
Cold Cracking Sensitivity: A612 has a higher manganese content, and its Ceq may be slightly higher than that of A516 Gr 70. Therefore, when welding A612, controlling the preheating temperature is critical; it must be strictly carried out in accordance with the Welding Procedure Specification (WPS) to prevent the formation of hardened microstructures due to excessive cooling rates.
Post-Weld Heat Treatment
- A516 Gr 70: When the thickness reaches a certain level (e.g., exceeding 38 mm as specified by ASME), PWHT must be performed to relieve stresses.
- ASTM A612: Since ASTM A612 is commonly used in thinner vessels (≤25 mm), PWHT may sometimes be waived based on design criteria.
Quality Control on ASTM A612 Steel Plates
The ASTM A612 standard requires that steel must pass four key inspections to ensure "zero defects":
Ultrasonic Testing: Conducted in accordance with GB/T 2970 or NB/T 47013.3-2015 to detect internal defects such as cracks, inclusions, and delamination (Acceptance Grade: Grade I);
Chemical Composition Analysis: Verifies whether the steel's composition complies with the standard through spectroscopic analysis or chemical titration (tolerance ≤ 0.01%);
Mechanical Property Testing: Tests indicators such as yield strength, tensile strength, and impact energy using tensile testing machines and impact testing machines (number of test specimens: 3 per batch);
Surface Quality Inspection: Visual inspection or magnetic particle testing to ensure the steel surface is free of defects such as cracks, bubbles, and scale (grinding is permitted, but the depth must be ≤0.5 mm).
Packaging and Shipping
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FAQ:
What is A612 material?
A612 steel plate is the standard specification for pressure vessel plates that are high strength, carbon steel for moderate and lower temperature use.
What is the composition of ASTM A612?
What is the composition of ASTM A612? ASTM A612 steel plate is a high-strength low-alloy (HSLA) steel plate designed for welded pressure vessels. It has a nominal composition of carbon, manganese, phosphorus, sulfur, silicon, nickel, chromium, molybdenum, and copper.
What is ASTM A516 Grade 70 material?
ASTM A516 Gr 70 Rolled Plate is a medium carbon alloy that contains manganese, phosphorus, sulfur, and silicon. These added alloying elements provide increased strength and versatility in highly demanding applications such as pressure vessels requiring moderate to lower temperatures where notch toughness is essential.
What Are the Equivalent Grades of SA612/A612 in Chinese and European Standards? Can They Be Used as Direct Substitutes?
Common approximate equivalent grades include EN P355GH, DIN 1.0473, and GB Q345R. However, they cannot be used as direct equivalents. Their suitability must be confirmed in accordance with design specifications and approval requirements.
Which Is More Suitable for Low-Temperature Applications: SA612 or SA516 Gr.70?
SA612 delivers more stable comprehensive performance in thick plate and high-stress working conditions, whereas SA516 Gr.70 offers better cost-effectiveness in conventional operating conditions.