ASTM A350 LF3 is a low-alloy steel grade designated as “3.5Ni steel” or “3-1/2Ni steel”. Forgings made of ASTM A350/ ASME SA-350 LF3 may be furnished in Class 1 or Class 2 with minor difference in Charpy V-notch energy requirements. This nickel steel is primarily applied for low-temperature service requiring notch toughness testing. However, it may also applied to services at elevated temperatures.
The product forms of ASTM A350 LF3 cover flanges, fittings, valves, bars, rods, pressure vessel plates, and other tailor-made forgings. They can be applied to a series of ASME Boiler and Pressure Vessel Codes according to ASME BPVC Section II Part D. Its UNS designation number is K32025 with a P-Number of 9B and Group Number of 1.
ASTM A350/ ASME SA-350 LF3 forgings, both Class 1 and Class 2, can be used with the minimum temperature limit of -150°F [-101°C]. According to Table 1A of ASME BPVC Section II Part D, they can be applied to ASME BPVC Section III, Classes 2 and 3; Section VIII, Division 1; and Section XII with maximum temperature limit of 343°C. According to Table 2A, they can be applied to Section III, Division 1, Classes 1 and MC and Section III, Division 3, Classes TC and SC with maximum temperature limit of 371°C; Section VIII, Division 2, Class 1 with maximum temperature limit of 149°C. According to Table 5A, they can be applied to Section VIII, Division 2 with maximum temperature limit of 343°C.