ASTM A350 LF3 Applied to ASME BPVC

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.

A ball valve with extended stem for low-temperature service; the valve body material is ASTM A350 Gr. LF3.

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.

Applicability & Temperature Limits

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.