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GB/T 18248-2021 English PDF (GBT18248-2021)

GB/T 18248-2021 English PDF (GBT18248-2021)

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GB/T 18248-2021: Seamless steel tubes for gas cylinder

This document specifies the order content, size, shape, weight and allowable deviation, technical requirements, test methods, inspection rules, packaging, marking and quality certificate of seamless steel tubes for gas cylinder. This document applies to seamless steel tubes for the manufacture of gas cylinders and accumulator shells.
GB/T 18248-2021
NATIONAL STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
ICS 77.140.75
CCS H 48
Replacing GB/T 18248-2008
Seamless steel tubes for gas cylinder
ISSUED ON: AUGUST 20, 2021
IMPLEMENTED ON: MARCH 01, 2022
Issued by: State Administration for Market Regulation;
Standardization Administration of the PEOPLE Republic of China.
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Normative references ... 5
3 Terms and definitions... 7
4 Symbols ... 7
5 Order content ... 7
6 Size, shape, weight and allowable deviation ... 8
7 Technical requirements ... 11
8 Test methods ... 14
9 Inspection rules ... 15
10 Packaging, marking and quality certificate ... 16
Appendix A (Informative) Other designations and chemical compositions ... 17 Appendix B (Informative) Reference values for mechanical properties option I ... 18 Appendix C (Informative) Reference values for mechanical properties option II ... 20 Seamless steel tubes for gas cylinder
1 Scope
This document specifies the order content, size, shape, weight and allowable deviation, technical requirements, test methods, inspection rules, packaging, marking and quality certificate of seamless steel tubes for gas cylinder.
This document applies to seamless steel tubes for the manufacture of gas cylinders and accumulator shells (hereinafter referred to as steel tubes).
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the version corresponding to that date is applicable to this document; for undated references, the latest version (including all amendments) is applicable to this document. GB/T 222, Permissible tolerances for chemical composition of steel products GB/T 223.5, Steel and iron - Determination of acid-soluble silicon and total silicon content - Reduced molybdosilicate spectrophotometric method
GB/T 223.9, Iron, steel and alloy - Determination of aluminium content - Chrome azurol S photometric method
GB/T 223.11, Iron, steel and alloy - Determination of chromium content - Visual titration or potentiometric titration method
GB/T 223.12, Methods for chemical analysis of iron, steel and alloy - The sodium carbonate separation-diphenyl carbazide photometric method for the determination of chromium content
GB/T 223.14, Methods for chemical analysis of iron, steel and alloy - The N-benzoy- N-phenylhydroxylamine extraction photometric method for the determination of vanadium content
GB/T 223.19, Methods for chemical analysis of iron, steel and alloy - The neocuproine-chloroform extraction photometric method for the determination of copper content
GB/T 223.26, Iron, steel and alloy - Determination of molybdenum content - The thiocyanate spectrophotometric method
GB/T 10561-2005, Steel - Determination of content of nonmetallic inclusions - Micrographic method using standards diagrams
GB/T 12606-2016, Automated full peripheral flux leakage testing of seamless and welded (except submerged arc-welded) ferromagnetic steel tubes for the detection of longitudinal and/or transverse imperfections
GB/T 17395, Dimensions, shapes, masses and tolerances of seamless steel tubes GB/T 20066, Steel and iron - Sampling and preparation of samples for the determination of chemical composition
GB/T 20123, Steel and iron - Determination of total carbon and sulfur content Infrared absorption method after combustion in an induction furnace (routine method)
GB/T 30062, Terminology of steel pipes and tubes
GB/T 40080, Nondestructive testing of steel tubes - Automated electromagnetic testing of seamless and welded (except submerged arc-welded) steel tubes for the verification of hydraulic leak tightness
3 Terms and definitions
Terms and definitions defined in GB/T 222 and GB/T 30062 apply to this document. 4 Symbols
The following symbols apply to this document.
D: Nominal outer diameter.
S: Nominal wall thickness.
Smin: Minimum wall thickness.
5 Order content
A contract or order for ordering steel tubes under this document shall include, but not be limited to, the following:
a) a reference to this document;
b) product name:
c) steel designation;
6.3.1 The curvature per meter of the steel tube shall meet the following requirements: a) When the wall thickness is not greater than 15 mm, it is not greater than 1.5 mm/m; b) When the wall thickness is greater than 15 mm, it is not greater than 2.0 mm/m. 6.3.2 The full-length curvature of the steel tube shall not exceed 0.15% of the length of the steel tube.
6.4 Out-of-roundness and uneven wall thickness
According to the requirements of the buyer, if it is negotiated between the supplier and the buyer, and indicated in the contract, the out-of-roundness and uneven wall thickness of the steel tube shall not exceed 80% of the outer diameter allowance and wall thickness allowance, respectively.
6.5 End shape
The end faces of the steel tube shall be perpendicular to the axis of the steel tube; the burrs of the cut shall be removed.
6.6 Weight
6.6.1 Delivery weight
Steel tubes shall be delivered by actual weight. If it is negotiated between the supplier and buyer, and indicated in the contract, it can also be delivered as per the theoretical weight.
6.6.2 Calculation of theoretical weight
The theoretical weight of the steel tube is calculated according to the provisions of GB/T 17395 (the density of steel shall be 7.85 kg/dm3). For steel tubes delivered as per the nominal outer diameter and minimum wall thickness, the theoretical weight shall be calculated by the average wall thickness. The average wall thickness is the average of the maximum and minimum wall thicknesses calculated according to the wall thickness and its allowable deviation.
6.6.3 Weight allowable deviation
According to the requirements of the buyer, if it is negotiated between the supplier and the buyer, and indicated in the contract, the deviation between the actual weight and the theoretical weight of the delivered steel tubes shall meet the following requirements: a) Single steel tube: ??10%;
b) Each batch of steel tubes with a minimum of 10 t: ??7.5%.
7.2 Manufacturing method
7.2.1 Smelting method of steels
The steel shall be refined outside the furnace with an electric arc furnace and processed by vacuum refining, OR refined outside the furnace with an oxygen converter and processed by vacuum refining.
7.2.2 Manufacturing method of tube blank
The tube blank can be manufactured by continuous casting, die casting or hot rolling (forging).
7.2.3 Manufacturing method of steel tubes
The steel tubes shall be manufactured by hot-rolled (expanded) or cold-rolled (drawn) seamless method.
7.3 Delivery state
Hot-rolled (expanded) steel tubes shall be delivered in hot-rolled (expanded) state, and cold-rolled (drawn) steel tubes shall be delivered in cold-rolled (drawn), normalized or annealed state.
7.4 Mechanical properties
7.4.1 The supplier shall select one option from the following three options of mechanical properties to provide mechanical properties for reference:
a) Mechanical properties option I: The mechanical properties measured from the sample made of heat-treated steel tube blanks, refer to Appendix B for reference values;
b) Mechanical properties option II: The mechanical properties measured from the sample made of heat-treated steel tube blanks, see Appendix C for reference values;
c) Mechanical properties option III: The mechanical properties report method determined by the negotiation between the supplier and the buyer.
7.4.2 Unless otherwise specified in the contract, the supplier shall provide reference values of mechanical properties by means of mechanical properties option I. 7.5 Compactness
7.5.1 General
Steel tubes shall be subjected to a compactness test. The compactness test can be carried out using hydraulic test or electromagnetic test, and the test method shall be selected by the supplier.
7.5.2 Hydraulic test
When the steel tube is subjected to the hydraulic test, the test pressure shall be 5 MPa. Under the test pressure, the voltage stabilization time shall be no less than 5 s; the steel tube should not leak.
7.5.3 Electromagnetic detection
When the steel tube is subjected to eddy current or magnetic flux leakage testing, the acceptance level shall comply with the provisions of GB/T 40080.
7.6 Non-metallic inclusions
Steel tubes shall be subjected to the detection of non-metallic inclusions. The non- metallic inclusions of steel tubes are rated according to method A of GB/T 10561-2005. The fine and coarse grades of Class A, Class B, Class C, and Class D inclusions shall not be greater than 2.0, respectively; the inclusions of Class DS shall not be greater than 2.0.
7.7 Surface quality
7.7.1 There shall be no visible cracks, folds, breaks, delamination and scars on the inner and outer surfaces of the steel tubes. These defects shall be completely removed; the depth of removal shall not exceed 10% of the wall thickness; the actual wall thickness of the cleaned part shall not be less than the minimum allowable wall thickness; the removal part shall have a smooth transition.
7.7.2 The depth of the straight on the inner and outer surfaces of the steel tube shall meet the following requirements:
a) For hot-rolled steel tubes, it shall not exceed 5% of the wall thickness and shall not exceed 0.4 mm;
b) For hot-expanded steel tubes, it shall not exceed 0.5 mm;
c) For cold-rolled (drawn) steel tubes, it shall not exceed 4% of the wall thickness and shall not exceed 0.2 mm.
7.7.3 Other local imperfections where the depth does not exceed the lower deviation of the wall thickness are allowed.
7.8 Non-destructive testing

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