ASTM A516 Grade 65 is a carbon steel grade specified for pressure vessel applications, particularly in moderate to lower temperature service where good toughness and weldability are required. It is part of the ASTM A516 series, which covers several grades of carbon steel plates for pressure vessels. The designation 65 refers to the minimum tensile strength of 65 ksi, about 450 MPa, and the grade is commonly used for boilers, storage tanks, and heat exchangers.
Material Properties
ASTM A516 Grade 65 has a minimum yield strength of 35 ksi, about 240 MPa, and a tensile strength of 65 to 85 ksi, about 450 to 585 MPa. Minimum elongation is 23 percent in 50 mm gauge length and 19 percent in 200 mm gauge length. The composition and heat treatment are controlled to ensure reliable performance under pressure and varying thermal conditions, and the steel offers a good balance of strength, ductility, and resistance to brittle fracture at reduced temperatures.
Chemical Composition
The chemical composition of A516 Grade 65 includes carbon up to 0.24 percent, manganese of 0.85 to 1.20 percent, silicon of 0.15 to 0.40 percent, and phosphorus and sulfur limited to 0.020 and 0.010 percent respectively. The steel is made as killed, fine-grain material, and a typical carbon equivalent of about 0.44 percent is controlled to support weldability. The low impurity limits contribute to the toughness of the plate at lower service temperatures.
What the Designation Means
The 65 in A516 Grade 65 refers to the minimum tensile strength of 65 ksi, and it is not a yield strength value. This distinction matters when comparing grades: the yield strength of Grade 65 is 35 ksi, while the higher tensile range gives the plate additional margin for pressure service. The grade is selected for pressure vessel designs that need more strength than Grade 60 but do not require the full capacity of Grade 70.
How Pressure-Temperature Ratings Are Established
Pressure-temperature ratings are not printed in the material specification itself; they are derived from the design rules of the governing code, most commonly the ASME Boiler and Pressure Vessel Code Section VIII Division 1. The code provides allowable stress values as a function of temperature, and the maximum allowable working pressure of a vessel is calculated from the allowable stress, the wall thickness, and the vessel geometry. A516 Grade 65 is suited to moderate and lower temperature service, and for any elevated-temperature design the allowable stress at the design temperature governs the rating.
Typical Applications
Boilers, pressure vessels, and storage tanks in oil refineries and gas processing plants
Heat exchangers, condensers, and boiler drums in power generation
Reaction vessels and process equipment in the chemical industry
Equipment that handles crude oil, refined products, and liquefied gases
Components requiring resistance to brittle fracture under fluctuating pressure and temperature
Frequently Asked Questions
What does 65 mean in A516 Grade 65? It refers to the minimum tensile strength of 65 ksi, about 450 MPa, not the yield strength.
What is the yield strength of A516 Grade 65? The minimum yield strength is 35 ksi, about 240 MPa, and the tensile strength is 65 to 85 ksi.
Where are pressure-temperature ratings defined? They are derived from the allowable stress tables and design rules of the governing code, such as ASME BPVC Section VIII Division 1.
Is A516 Grade 65 suitable for low-temperature service? Yes, it offers good toughness at moderate and lower temperatures, with resistance to brittle fracture.
Can A516 Grade 65 be cold-formed? Yes, its moderate strength and good ductility allow bending, rolling, and press forming with standard techniques.
What is the carbon equivalent of A516 Grade 65? typical carbon equivalent is about 0.44 percent, which supports good weldability.