SA516 Grade 65 is a carbon steel plate grade specified in ASTM A516/A516M and ASME SA-516/SA-516M, intended for fusion-welded pressure vessels and boilers that operate at moderate and lower temperatures. The grade is available in a normalized condition for thicker sections, providing a balance of strength, weldability, and notch toughness for pressure-retaining components in oil refining, petrochemical processing, power generation, and storage applications.
Chemical Composition Requirements
The carbon content of SA516 Grade 65 is controlled according to plate thickness to maintain weldability while achieving the required strength. Maximum carbon ranges from 0.24% for plates 12.5 mm and under to 0.29% for plates over 100 mm. Manganese is specified at 0.85-1.20% by heat analysis, with phosphorus and sulfur each limited to 0.025% maximum. Silicon is controlled at 0.15-0.40% by heat analysis, and product analysis limits follow the sampling rules of the governing specification.
For weldability assessment, the carbon equivalent (CE) is commonly kept at or below about 0.43%, which supports preheat planning and hydrogen-induced cracking control during shop fabrication.
Mechanical Properties
The specified tensile strength of SA516 Grade 65 is 65-85 ksi (450-585 MPa), with a minimum yield strength of 35 ksi (240 MPa). Minimum elongation is 23% in a 2 in. (50 mm) gauge length and 19% in an 8 in. (200 mm) gauge length. Charpy V-notch impact testing is applied when required by the purchasing specification or the applicable code, with acceptance values typically set at 27 J (20 ft-lbf) at the designated test temperature, which depends on thickness and design temperature.
Heat Treatment and Plate Supply Conditions
Plates over 40 mm (1.5 in.) in thickness are normally supplied in the normalized condition to refine the grain structure and improve notch toughness. Thinner plates may be supplied as-rolled unless normalization is specified by the purchaser or required by the applicable pressure vessel code. Normalizing involves heating the plate uniformly above the upper critical temperature and cooling in air. Plates are commonly available in thicknesses from about 5 mm up to 200 mm.
Welding and Fabrication Considerations
SA516 Grade 65 is readily weldable by shielded metal arc welding (SMAW), gas metal arc welding (GMAW), flux-cored arc welding (FCAW), and submerged arc welding (SAW). Low-hydrogen consumables and appropriate preheat are recommended, particularly for thicker sections and restrained joints. Post-weld heat treatment may be applied when required by code or design to relieve residual stresses and restore toughness in the heat-affected zone.
Typical Applications and Service Conditions
The grade is used for welded pressure vessels, boiler components, heat exchangers, and storage tanks, including LPG storage where low-temperature toughness is important. In petrochemical service, components such as high-pressure reactors, separators, and gas storage tanks operate within the allowable stress limits of the governing code, with typical vessel working pressures not exceeding about 6.4 MPa. The lower design temperature limit is typically about -45 C for impact-tested material, while the upper service temperature is generally limited to about 450 C due to graphitization concerns; under ASME Section VIII Division 1, the maximum service temperature for this material class is recognized up to approximately 538 C (1000 F), subject to allowable stress data.
Because SA516 Grade 65 is a carbon steel, its corrosion resistance is limited. Protective coatings, cladding, or cathodic protection may be required in humid, acidic, or seawater environments, and compatibility with the process medium should be evaluated during design.
Frequently Asked Questions
What is the minimum yield strength of SA516 Grade 65?
The minimum yield strength is 35 ksi (240 MPa), per ASTM A516/A516M and ASME SA-516/SA-516M.
What is the minimum tensile strength of SA516 Grade 65?
The tensile strength range is 65-85 ksi (450-585 MPa), with 65 ksi as the minimum.
When must SA516 Grade 65 plates be normalized?
Plates over 40 mm (1.5 in.) in thickness are normally normalized. Thinner plates may be supplied as-rolled unless the order or code requires normalization.
Which welding processes can be used?
SMAW, GMAW, FCAW, and SAW are all suitable with low-hydrogen practice and proper preheat for thicker sections.
What is the maximum service temperature of SA516 Grade 65?
The material is intended for moderate and lower temperature service. Upper limits are governed by the applicable code; typical design guidance limits the temperature to about 450 C due to graphitization, and ASME Section VIII Division 1 recognizes service up to approximately 538 C (1000 F) subject to allowable stresses.
Is SA516 Grade 65 suitable for LPG storage tanks?
Yes. Its notch toughness and weldability make it a common choice for LPG and other low-temperature storage applications, provided the design temperature is within the Charpy impact test limits specified for the material.