Fe is the basis.
According to TU 108-1028-81 and TU 108-1029-81 the chemical composition is given for steel grade 25Х2Н4МФА. In the blanks, deviations in the content of the elements indicated in the table are allowed: carbon ± 0.010%, silicon + 0.030%, sulfur + 0.001%, phosphorus + 0.001%. In the manufacture of blanks with discs with hub heights from 450 to 650 mm, the content of phosphorus and sulfur in steel should not be more than 0.018% of each; For metal VDP and ELP, the deviation of manganese content +0.10% is allowed. In the ESR steel, the sulfur content should not be more than 0.015%. When casting steel without evacuation, for the manufacture of disc blanks with a hub height of more than 300 mm, hydrogen content in the metal must be determined. The results of determination of the hydrogen content are not acceptance-delivery and, at the request of the consumer, are to be entered in the procurement certificate.