GB/T 5216-2014Structural steels with specified hardenability bands (English PDF)

Foreword

SAC/TC 183 is in charge of this English translation. In case of any doubt about the contents of the English translation, the Chinese original shall be considered authoritative.

This standard is drafted in accordance with the rules given in GB/T 1.1-2009 Directives for standardization - Part 1: Structure and drafting of standards.

This standard replaces GB/T 5216-2004 Structural steels subject to end-quench hardenability requirements in whole.

In addition to a number of editorial changes, the following technical deviations have been made with respect to GB/T 5216-2004: the requirement for the dimension "diameter or thickness not less than 30 mm" has been deleted from the scope; the classification of steels into quality steels and advanced quality steels has been deleted from classification and designation; the number of steel grades has been increased from 24 to 32 (sulfur containing grades are not counted), namely 25CrH, 28CrH, 35CrMoH, 17Cr2Ni2H, 22CrNiMoH, 27CrNiMoH, 40CrNi2MoH and 18Cr2Ni2MoH, together with their related technical requirements.

The upper and lower limits of some steel grades listed in Table 1 have been adjusted: the lower limit of boron in boron-containing grades was adjusted to 0.0008 % and the upper limit to 0.003 5 %; the upper limit of manganese for 17CrMnBH was adjusted from 1.30 % to 1.40 %; the upper limits of manganese and chromium for 20CrMnTiH were adjusted from 1.15 % to 1.20 % and from 1.35 % to 1.45 % respectively; the lower limit of sulfur for the sulfur containing grade was adjusted from 0.020 % to 0.015 %; the carbon content of 15CrMoH was adjusted to 0.12 % to 0.18 %.

The content requirements for the impurity elements sulfur and phosphorous and for the residual elements copper, chromium and nickel have been unified; a requirement of oxygen content not more than 0.002 0 % has been added; hardness requirements for 16CrMnH and 20CrMnH after annealing or high temperature tempering have been added; and a provision has been added in 6.5.1 that sampling can be done on the intermediate billet for steel bars with a nominal diameter or thickness of less than 30 mm.

1 Scope

China's national standard for structural steel bars sold against a guaranteed hardenability band. Hardenability is not the hardness of a steel but its willingness to harden through its section when quenched, and it is the property that decides whether a gear tooth or a shaft comes out of heat treatment hard where it must be and tough underneath. Two casts that meet the same chemical specification can still harden differently, and a gearmaker who discovers that only after machining and quenching has scrapped a finished part. The answer the industry settled on is to buy the property rather than the composition: the steel is supplied with its end-quench curve guaranteed to fall inside a named band, so the heat treatment can be fixed in advance and holds from batch to batch. This standard sets the technical delivery requirements for such bars - order information, classification and designation, dimensions, shape, mass and tolerances, technical requirements, test methods, inspection rules, packaging, marking and the certificate of quality - and applies to hot-rolled and hot-forged structural steel bars with specified hardenability bands used to make machinery components, with hardenability either measured by the end-quench method or calculated by formula. The 2014 edition raised the number of grades from 24 to 32 and dropped the old restriction to bars of 30 mm and over.

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.

2 Normative references

The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

GB/T 222 Permissible tolerances for chemical composition of steel products.

GB/T 223.3, GB/T 223.5, GB/T 223.11, GB/T 223.13, GB/T 223.14, GB/T 223.16, GB/T 223.17, GB/T 223.18, GB/T 223.19, GB/T 223.23, GB/T 223.25, GB/T 223.26, GB/T 223.53, GB/T 223.54, GB/T 223.58, GB/T 223.59, GB/T 223.60, GB/T 223.61, GB/T 223.62, GB/T 223.63, GB/T 223.64, GB/T 223.67, GB/T 223.68, GB/T 223.69, GB/T 223.71, GB/T 223.72, GB/T 223.75, GB/T 223.76, GB/T 223.78, GB/T 223.79, GB/T 223.81, GB/T 223.84, GB/T 223.85 and GB/T 223.86 Methods for chemical analysis of iron, steel and alloy.

GB/T 225 Steel - Hardenability test by end quenching (Jominy test).

GB/T 226 Etch test for macrostructure and defect of steels; GB/T 1979 Standard diagrams for macrostructure and defect of structural steels; GB/T 15711 Steel products - Method for etch test of tower sample.

GB/T 228.1 Metallic materials - Tensile testing - Part 1: Method of test at room temperature; GB/T 229 Metallic materials - Charpy pendulum impact test method; GB/T 231.1 Metallic materials - Brinell hardness test - Part 1: Test method.

GB/T 702 Hot-rolled steel bars - Dimensions, shape, weight and tolerances; GB/T 908 Forged steel bars - Dimensions, shape, weight and tolerances.

GB/T 2101 General requirement of acceptance, packaging, marking, and certification for section steel; GB/T 2975 Steel and steel products - Location and preparation of test pieces for mechanical testing.

GB/T 4336 Standard test method for spark discharge atomic emission spectrometric analysis of carbon and low-alloy steel (routine method); GB/T 20123, GB/T 20125, GB/T 21834 and GB/T 22368 for the determination of multi-element and carbon and sulfur contents.

GB/T 6394 Metal - Methods for estimating the average grain size; GB/T 7736 Ultrasonic inspecting method for macro-structure and imperfection of steel; GB/T 10561 Steel - Determination of content of nonmetallic inclusions - Micrographic method using standards diagrams.

GB/T 11261 Steel and iron - Determination of oxygen content - The pulse heating inert gas fusion-infra-red absorption method; YB/T 4305 and YB/T 4307 for the determination of oxygen, nitrogen and hydrogen contents.

GB/T 13298 Inspection method of microstructure for metals; GB/T 13299 Steel - Determination of microstructure.

GB/T 17505 Steel and steel products - General technical delivery requirements; GB/T 17616 Unified numbering system for designation of iron, steel and alloy; GB/T 20066 Steel and iron - Sampling and preparation of samples for the determination of chemical composition; YB/T 5293 Metallic materials - Forging test.

3 Information to be supplied by the purchaser

The following information shall be supplied by the purchaser in the order or contract according to this standard: a) number of this standard; b) product name; c) grade and uni-code; d) mass or quantity to be delivered; e) dimensions and shape; f) working method for use (see 4.2); g) delivery condition (if required, see 6.3); h) hardenability (see 6.5); i) class of macrostructure (see 6.7); j) class of non-metallic inclusions (see 6.8.2); k) other special requirements (if required, see 6.10).

4 Classification and designation

4.1 The steels in this standard include non-alloy structural steel and alloy structural steels.

4.2 According to the subsequent working method, the steel grades are classified into steels used for pressure work (UP) and steels used for cut work (UC). The working method shall be given in the order or contract.

4.3 The steels with specified hardenability band shall be identified by the suffix letter "H" (base hardenability band), "HH" (higher two thirds of hardenability band) or "HL" (lower two thirds of hardenability band), for example 40CrH, 40CrHH and 40CrHL.

4.4 For S-containing steels, "S" shall be added before "H", for example 16CrMnSH, 16CrMnSHH and 16CrMnSHL.

4.5 Uni-code of the steels is designated according to GB/T 17616.

5 Dimensions, shape, mass and tolerances

5.1 Dimensions, shape, mass and tolerances of hot-rolled round and square bars shall comply with the specification of GB/T 702.

5.2 Dimensions, shape, mass and tolerances of hot-forged round and square bars shall comply with the specification of GB/T 908.

5.3 Dimensions, shape, mass and tolerances of other bars shall comply with the agreement between the purchaser and the supplier, detailed requirements of which shall be specified in the contract or order.