SA516 Grade 70, also designated A516 Grade 70 under ASTM, is one of the most widely used pressure vessel quality carbon steel plates in the world. It is designed for moderate to low-temperature service and is known for its excellent notch toughness, which makes it ideal for welded tanks and boilers that contain liquids or gases under pressure. The steel has a tensile strength range of 70 to 90 ksi, about 485 to 620 MPa, and a minimum yield strength of 38 ksi, about 260 MPa, with a controlled composition of carbon, manganese, and silicon. It is used for pressure vessels, boiler components, storage tanks, cryogenic equipment, and industrial structures across the petrochemical and power industries.
What Is SA516 Grade 70?
SA516 Grade 70 is a pressure vessel quality carbon steel plate specified in ASTM A516 and its ASME adoption SA516. The grade 70 refers to the minimum tensile strength in ksi, and the specification covers plates for moderate and lower temperature service in welded pressure vessels. The steel is characterized by excellent notch toughness, which means it resists brittle fracture even at lower temperatures, and by good weldability. It is supplied in the normalized condition when required by the design code, which refines the grain and improves toughness further. The material is one of the most common choices for vessels that store liquefied gases and chemicals.
Chemical Composition
The composition of SA516 Grade 70 is controlled for strength and toughness. Maximum carbon is 0.25 percent, manganese is 0.85 to 1.20 percent, and silicon is limited to 0.40 percent. Phosphorus is limited to 0.020 percent and sulfur to 0.010 percent, which are tight limits that reduce embrittlement and improve weldability. The manganese content provides strength while the low impurity levels preserve notch toughness. This controlled chemistry is what allows the steel to meet the Charpy impact requirements that are often specified for pressure vessel service.
Mechanical Properties
The minimum yield strength of SA516 Grade 70 is 38 ksi, about 260 MPa, and the tensile strength range is 70 to 90 ksi, about 485 to 620 MPa. Minimum elongation is 21 percent measured over a 2 inch gauge length and 17 percent over an 8 inch gauge length. The strength and ductility values are verified by testing each plate, and impact testing is performed when required by the application. This combination of moderate strength and high toughness is the reason the grade performs reliably in welded vessels under pressure and temperature cycling.
Key Applications
SA516 Grade 70 is used for pressure vessels in refineries, chemical plants, and offshore platforms, where vessels must withstand internal pressure, temperature cycling, and corrosive environments. It is used for boiler drums, headers, and heat exchanger tubesheets in power plants, and for large storage tanks meeting API 650 or API 620 for crude oil, refined products, and chemicals. Its toughness at low temperature makes it suitable for cryogenic equipment such as LNG storage and processing facilities. The steel also appears in compressors, pipelines, and structural components such as bridge girders and building frames where strength and economy are both important.
Comparison with Other Grades
Compared with SA 285 Grade C, a lower-strength carbon steel for moderate service, SA516 Grade 70 offers higher strength and significantly better low-temperature toughness, which makes it the preferred choice for demanding pressure vessel applications. The grade is frequently compared with the chromium-molybdenum grades such as SA 387, but SA516 is a plain carbon steel with moderate corrosion resistance and is normally selected where the service temperature is moderate to low rather than very high. For aggressive corrosive service, coatings, linings, or higher-alloy materials are recommended.
Frequently Asked Questions
What is A516 Grade 70 equivalent to? Common equivalents include ASME SA516 Grade 70, EN 10028 P355GH, and BS1501 224-490 Grades A and B, all suitable for similar pressure vessel applications.
What is the tensile strength of A516 Grade 70? The tensile strength range is 70 to 90 ksi, about 485 to 620 MPa, with a minimum yield strength of 38 ksi, about 260 MPa.
How does A516 Grade 70 compare with SA 285 Gr C? 516 Grade 70 has higher strength and significantly better low-temperature toughness than SA 285 Gr C, making it suitable for more demanding applications.
What is the corrosion resistance of A516 Grade 70? It has moderate corrosion resistance typical of carbon steels and is suitable for non-corrosive or mildly corrosive service; aggressive environments need coatings or higher-alloy materials.
When should A516 Grade 70 be chosen? Choose it when a pressure vessel steel with good strength, excellent low-temperature toughness, and reliable weldability is required, such as tanks and vessels handling liquefied gases or chemicals.
Is A516 Grade 70 suitable for cryogenic service? Yes, its ability to retain impact strength at subzero temperatures makes it suitable for LNG-type low-temperature tanks and processing equipment.