Steel 28Х3СНМВФА (СП28; ЭП326А)

Fe is the basis.
According to TU 14-1-871-74, the chemical composition is given for steel grade 28Х3СНМВФА-ВД (СП28-ВД).
According to TU 14-1-991-74 the chemical composition is given for steel grade 28Х3СНМВФА-ВД (СП28-ВД; ЭП326А-ВД). It is allowed to increase the content of sulfur and phosphorus by about 0010% with a total content of sulfur and phosphorus not more than 0.020%. Deviations in chemical composition are allowed: carbon ± 0.010%, manganese + 0.050 / -0.20%, silicon, chromium, nickel and tungsten ± 0.050% each, molybdenum ± 0.030%, vanadium +0.020%. Partial or complete replacement of tungsten with molybdenum is allowed, based on: 2.2 parts by weight of tungsten are replaced by one part by weight of molybdenum. When the tungsten is completely replaced, the molybdenum content should be in the range 0.75-0.95%.
According to TU 14-1-4461-88, the chemical composition of the steel should comply with the standards specified in Table 2 (Appendix 1), sent on request by the Central Research Institute of Chemical Technology named after Bardin. The sulfur content of sulfur is not more than 0.011%, phosphorus is not more than 0.015%, while the total content of sulfur and phosphorus should not be more than 0.022%. The residual copper content should not be more than 0.15%. With the consent of the consumer, it is allowed - up to 0.20%. In the finished sheets the following deviations in chemical composition from the norms indicated in Table 2 are allowed: carbon + 0.02 / -0.010%; tungsten ± 0.10%; manganese, silicon, chromium and nickel ± 0.050%; molybdenum ± 0.030%; vanadium +0.020%. Partial or complete replacement of tungsten by molybdenum from the calculation of 2.5 mass fraction of tungsten is allowed with one mass fraction of molybdenum.
According to TU 14-1-1447-75 the chemical composition is given for steel grade 28Х3СНМВФА (СП28). The sum of sulfur and phosphorus should not exceed 0.022%. It is allowed to increase the content of sulfur or phosphorus by 0.0010% with a total content of no more than 0.022%. Deviations in the established norms for the chemical composition are allowed: carbon ± 0.010%, chromium, nickel, silicon, manganese, tungsten ± 0.050%, molybdenum ± 0.030%, vanadium + 0.020%. Full or partial replacement of tungsten with molybdenum is allowed at the rate of 2.5 parts by weight of tungsten is replaced by one part by weight of molybdenum. When molybdenum is completely replaced by tungsten, the molybdenum content should be 0.75-0.95%. In the case of partial replacement of tungsten with molybdenum, the actual content of tungsten is recalculated to molybdenum in a ratio of 2.5: 1 and the conditional total molybdenum and tungsten content in terms of molybdenum should correspond to the specified molybdenum content when the tungsten is completely replaced. In steel without the replacement of tungsten by molybdenum, the residual molybdenum content of 0.10% is allowed. With the complete replacement of tungsten by molybdenum, the residual content of tungsten is allowed up to 0.15%.