NIPPON STEEL CORPORATION (NSC) has developed stainless steel grade, called 317AP, which provides improved corrosion resistance to polythionic acid corrosion and naphthenic acid corrosion in refinery service. A user has requested that the new is considered for inclusion in A479, A240, A480, and in other related ASTM stainless steel specifications. The supporting data from at least three heats steel has been provided. Additional information is available upon request. This grade is covered by a patent.
The UNS number for this grade has been issued and is S31740. This grade has already been incorporated in ASTM specifications A182.A182M-21, A213/A213M-21a, and in A312/A312M-21. There is also an ASME code case request (under proposal RN 20-1834) for use of the UNS S31740 materials for Section VIII, Division 1 pressure vessel construction and conforming to the requirements of specifications SA-182, SA-213, SA-312, SA-240, SA-403, and SA-479.