GB/T 5216 standard Specifies standard specifies the ordering, classification and code, size, shape, weight and allowable deviation, technical requirements, test methods, inspection rules, packaging, marking and quality certificates of the hardened structural steel bars.GB/T 5216 standard applies to the manufacture of machinery to ensure the hardenability of the hot-rolled and hot forging steel bar (hereinafter referred to as steel). Determination of hardenability of steel by end quenching method or by formula.GB/T 5216 standard main steel grade:20CrMnTiH,20CrMoH and so on.