ASTM A515 Grade 65 is a carbon steel plate specified for pressure vessels, boilers, and related equipment intended for intermediate and higher temperature service. The plates are normally supplied in the normalized condition to refine the grain structure and provide consistent elevated-temperature strength. Grade 65 is the middle strength level of the A515 series, which also includes Grade 60 and Grade 70. This article describes the composition, mechanical properties, applications, and welding practice for A515 Grade 65.
Grade Overview and Intended Service
A515 is a specification for carbon steel plates for pressure vessels in intermediate and higher temperature service. Compared with A516, which is optimized for moderate and lower temperature service, A515 has a higher carbon content and is intended for applications where elevated temperature strength is important, such as boiler drums and steam piping components. Grade 65 provides a balance of strength, weldability, and cost for vessels designed under ASME Boiler and Pressure Vessel Code Section VIII.
Chemical Composition
For A515 Grade 65, carbon is specified in the range of 0.28% to 0.33% by both heat and product analysis. Manganese is limited to 0.90% by heat analysis and 0.98% by product analysis. Phosphorus and sulfur are each limited to 0.035% maximum. Silicon is specified at 0.15% to 0.40% by heat analysis and 0.13% to 0.45% by product analysis. The controlled carbon and manganese levels provide the strength required for elevated-temperature service while maintaining weldability.
Mechanical Properties
The minimum yield strength of A515 Grade 65 is 240 MPa and the tensile strength is 450 to 585 MPa. The minimum elongation is 23% in a 50 mm gauge length and 19% in a 200 mm gauge length. Plates are commonly produced in thicknesses up to about 200 mm; for very thick sections, the purchaser may specify additional heat treatment to ensure uniform properties through the thickness. The material retains useful strength at elevated temperature, and per code allowable stress data it is typically applied at temperatures up to about 900 F (482 C).
Typical Applications
A515 Grade 65 is used in boiler manufacturing for components such as steam drums in power plants and industrial heating systems, where it must withstand long-term exposure to high-temperature steam and pressure. In the petrochemical industry it is used for medium-pressure hydrogenation reactors, catalytic cracking regenerators, and shells of shell-and-tube heat exchangers, typically in service conditions of about 300 to 380 C at pressures of 4 to 8 MPa. It is also applied to separators, spherical tanks, and gas storage tanks in chemical and metallurgical plants, and to welded pipe for steam pipelines carrying medium-pressure steam at about 250 to 350 C and 3 to 5 MPa.
Welding and Fabrication
A515 Grade 65 is weldable by the common arc processes, including shielded metal arc welding (SMAW), gas metal arc welding (GMAW), flux-cored arc welding (FCAW), and submerged arc welding (SAW). Thin plates can often be welded without preheat, but preheating is recommended for thicker sections and highly restrained joints to prevent hydrogen-induced cracking. Post-weld heat treatment is applied when required by the governing pressure vessel code to reduce residual stress and improve heat-affected zone toughness. Forming is performed cold or warm; if the plate is heated above the normalizing range, re-normalization is required to restore the specified properties.
Frequently Asked Questions
What is A515 Grade 65 used for?
A515 Grade 65 is used for boilers, pressure vessels, heat exchangers, separators, and steam pipelines operating at intermediate and higher temperatures, typically up to about 900 F (482 C).
What are the key mechanical properties of A515 Grade 65?
The minimum yield strength is 240 MPa, the tensile strength is 450 to 585 MPa, and the minimum elongation is 23% in a 50 mm gauge length and 19% in a 200 mm gauge length.
What is the maximum service temperature of A515 Grade 65?
Per code allowable stress data, the grade is typically used at temperatures up to about 900 F (482 C). Above this range, chromium-molybdenum alloy steels are normally required to resist creep and oxidation.
How does A515 Grade 65 differ from A516 Grade 70?
A515 has a higher carbon content and is optimized for elevated temperature strength, while A516 Grade 70 has better low-temperature toughness and is preferred for colder service conditions.
Which welding processes are suitable for A515 Grade 65?
SMAW, GMAW, FCAW, and SAW are all suitable. Preheat is recommended for thick sections and restrained joints, and post-weld heat treatment is applied as required by the code.
What is the maximum thickness available?
Plates are commonly produced up to about 200 mm thick. Thicker sections may require additional heat treatment to ensure uniform mechanical properties.