ASTM A694 flanges are available in various grades such as F42, F52, F60, F65, and F70. The difference lies in the chemical composition. ASME SA694 high yield CS F52 slip-on flanges are made of carbon, silicon, manganese, phosphorus, sulfur, molybdenum, nickel, chromium, copper, vanadium, and niobium. There are different types of flanges and Shasan Piping Solution is a leading supplier... https://www.shasanpiping.com/carbon-steel-a-694-flanges-manufacturers-exporters-suppliers-stockists.html