This standard specifies the rules for the designation of iron and steel. This standard is applicable to design iron and steel grades for pig irons, carbon structural steels, low-alloy structural steels, quality carbon structural steels, free-cutting steels, alloy structural steels, spring steels, tool steels, bearing steels, stainless steels, heat-resisting steels, steels for welding, cold-rolled electrical steels, electro-magnetic pure irons, pure irons as raw material, high resistance alloys for electrical heating and related special-purpose steels. The rules for the designation of iron and steel not specified in this standard shall also be in accordance with the principles of this standard.