This standard specifies the technical delivery requirements for bars of structural steels subject to hardenability requirements in terms of order information,classification and designation,dimensions,shape,mass and tolerances,technical requirements,test methods,inspection rules,package,marking,and certificate of quality. This standard is applicable to hot-rolled and/or hot-forged structural steel bars with specified hardenability bands for the manufacture of machinery components.Hardenability can be either measured by the end-quench method or calculated by formula.