SA516 Grade 70, also designated ASTM A516 Grade 70, is an American standard carbon steel plate for pressure vessels. It is widely used in the manufacture of boilers and pressure vessels for the petroleum, chemical, power, and boiler industries, where the plate must withstand internal pressure and moderate service temperatures. The grade combines high strength with good low-temperature toughness and excellent welding performance, which makes it one of the most specified pressure vessel steels in the world.
Typical Chemical Composition
SA516 Grade 70 is a killed, fine-grain carbon steel. A typical mill analysis shows carbon of about 0.18 percent, silicon of about 0.40 percent, manganese of 0.95 to 1.50 percent, phosphorus and sulfur below 0.015 and 0.008 percent respectively, and a minimum aluminum content of about 0.02 percent for grain refinement. Residual elements are limited, including chromium, copper, and nickel up to about 0.30 percent each and molybdenum up to about 0.08 percent. These typical values are tighter than the maximum limits of the ASTM A516 specification, and the guaranteed values are defined by the standard.
Mechanical Properties
SA516 Grade 70 requires a tensile strength of 485 to 620 MPa, 70 to 90 ksi, and a minimum yield strength of 260 MPa, 38 ksi. Minimum elongation is 17 percent in 200 mm gauge length and 21 percent in 50 mm gauge length. The combination of strength and ductility allows the plate to be formed into shells and heads and to carry the design pressure safely.
Delivery Condition and Low-Temperature Toughness
The plate is supplied in the hot-rolled condition for thickness up to about 40 mm, and in the normalized condition for thicker plates, which refines the grain structure and guarantees the specified toughness. The steel is killed and fine-grain treated so that it shows good toughness at lower temperatures and resists brittle fracture. Charpy impact testing at -46 deg C is available as a supplementary requirement when low-temperature service is specified.
Welding and Fabrication
SA516 Grade 70 has excellent weldability and can be joined by all common welding processes, including SMAW, SAW, GMAW, and FCAW. Low-hydrogen consumables such as E7018 electrodes are recommended, and for plates above about 25 mm a preheat of at least 100 deg C is commonly applied. Post-weld heat treatment is performed when required by the governing pressure vessel code, typically for thicker welds or certain service conditions.
Typical Applications
Pressure vessels and reactor shells in petroleum and chemical plants
Boiler drums and steam separators in power stations
Storage tanks and spheres for oil and gas
Heat exchangers and process equipment
Low-temperature components where supplementary impact testing is specified
Frequently Asked Questions
What is SA516 Grade 70? It is an American standard carbon steel plate for pressure vessels, widely used in boilers and pressure vessel manufacturing.
What is the yield strength of SA516 Grade 70? The minimum yield strength is 260 MPa and the tensile strength is 485 to 620 MPa.
Is SA516 Grade 70 good for low-temperature service? Yes, the killed fine-grain steel has good low-temperature toughness, and Charpy testing at -46 deg C is available as a supplementary requirement.
Is SA516 Grade 70 weldable? Yes, it has excellent weldability with all common processes, using low-hydrogen consumables and preheat for thicker plates.
When is normalization required for SA516 Grade 70? Plates thicker than about 40 mm are supplied in the normalized condition to guarantee the mechanical properties.
What standard covers SA516 Grade 70? It is specified in ASTM A516 and ASME SA516, the American standards for carbon steel plates for pressure vessels.