What is the difference between A537 Class 1 and Class 2?

ASTM A537 is a specification for pressure vessel steel plates, heat-treated, carbon-manganese-silicon steel. It is commonly used in the construction of pressure vessels for moderate and lower-temperature service. The primary difference between A537 Class 1 and Class 2 lies in their respective minimum tensile strength requirements. Here are the key differences:

Minimum Tensile Strength: A537 Class 1 has a minimum tensile strength of 70 ksi (485 MPa), while A537 Class 2 requires a minimum tensile strength of 80 ksi (550 MPa). This difference in tensile strength reflects the intended use of these grades in different applications, with Class 2 offering higher strength.

Chemical Composition: The chemical composition of both Class 1 and Class 2 grades of A537 steel is similar. They typically contain carbon (C), manganese (Mn), phosphorus (P), sulfur (S), silicon (Si), and trace amounts of other elements. The composition ensures good weldability and resistance to brittle fracture.

Heat Treatment: Both Class 1 and Class 2 grades undergo heat treatment after rolling. The steel plates are typically normalized, which involves heating the plates above the austenitic region and then cooling them in still air. This heat treatment refines the grain structure and improves the mechanical properties of the material.

Impact Toughness Requirements: A537 Class 1 and Class 2 have specific impact toughness requirements. The Charpy V-notch impact test is performed at various temperatures to evaluate the material's ability to absorb energy under impact loading. Class 1 requires minimum impact energy values, while Class 2 has slightly higher minimum impact energy requirements.

It's important to note that the specific requirements for ASTM A537 Class 1 and Class 2 can be found in the official standard document. Consulting the latest version of the ASTM A537 specification will provide accurate and up-to-date information on the material's mechanical properties, chemical composition, and other requirements.