Difference between A202 Grade A and A203 Grade A

ASTM A202 Grade A and ASTM A203 Grade A are both specification designations for alloy steel plates used in the fabrication of welded pressure vessels and boilers . Despite this shared application, they are fundamentally different materials, designed for distinct service environments due to their unique alloying elements and mechanical properties.

ASTM A202 Grade A is a chromium-manganese-silicon alloy steel plate . It is characterized by its high strength, with a minimum yield strength of 310 MPa and a tensile strength range of 515-655 MPa . This grade achieves its properties through the addition of chromium (Cr), manganese (Mn), and silicon (Si), which contribute to its strength, hardness, and wear resistance . Its primary applications are in general pressure vessel construction, boilers, and storage tanks where high strength is required but service temperatures are moderate.

ASTM A203 Grade A, in contrast, is a nickel-alloy steel plate . Its defining characteristic is the addition of approximately 2.25% nickel, which significantly improves its low-temperature toughness and fracture resistance . Its yield strength is lower, at a minimum of 255 MPa, with a tensile strength of 450-585 MPa . The primary application for A203 Grade A is in equipment requiring reliable performance at low temperatures, such as cryogenic storage tanks for liquefied gases (e.g., LNG) and reactors in cold environments.

Chemical Composition

Mechanical Property