Difference between A204 Grade C and A285 Grade C

ASTM A204 Grade C and ASTM A285 Grade C are both specifications for steel plates used in the fabrication of welded pressure vessels and boilers. However, they represent fundamentally different classes of steel-one is an alloy steel for higher-strength applications, and the other is a carbon steel for general service where moderate strength is sufficient.

ASTM A204 Grade C is a molybdenum-alloy steel plate designed for higher-strength applications . It is the strongest grade within the A204 specification, with a tensile strength range of 75-95 ksi (515-655 MPa) . The addition of molybdenum as the primary alloying element provides enhanced strength and creep resistance at elevated temperatures. This grade is intended for use in welded boilers and pressure vessels operating at higher pressures or temperatures where greater strength is required . Plates are manufactured using killed steel practices and are available in thicknesses up to 4 inches (100 mm) .

ASTM A285 Grade C is a carbon steel plate of low- and intermediate-tensile strength . It represents the highest strength grade within the A285 specification, with a tensile strength range of 55-75 ksi (380-515 MPa) . This grade has a minimum yield strength of 30 ksi . A285 Grade C may be produced using various steel practices including killed, semi-killed, capped, or rimmed steel at the producer's option . It is limited to a maximum thickness of 2 inches (50 mm) for reasons of internal soundness . This material is commonly used in storage tanks and low-pressure, temperature-controlled vessels.

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