GB/T 46219-2025 Corrosion-resistant alloy U-bent tubes English, Anglais, Englisch, Inglés, えいご
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ICS 77.140.01
CCS H 57
National Standard of the People's Republic of China
GB/T 46219-2025
Corrosion-resistant alloy U-bent tubes
Issue date: 2025-08-29 Implementation date: 2026-03-01
Issued by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China
the Standardization Administration of the People's Republic of China
Contents
Foreword
1 Scope
2 Normative References
3 Terms and Definitions
4 Classification and Codes
5 Order Content
6 Manufacturing Process
7. Technical Requirements
References
Corrosion-resistant alloy U-bent tubes
1 Scope
This document specifies the classification and codes for corrosion-resistant alloy U-bend tubes, covering order content, manufacturing processes, technical requirements, inspection rules, packaging, marking, and quality certificates, and describes the corresponding test methods.
This document applies to U-bend tubes (hereinafter referred to as U-bend tubes) made of nickel-based, iron-nickel-based, and other corrosion-resistant alloys with a nominal outer diameter not exceeding 38 mm, a wall thickness not exceeding 3.0 mm, and a bending radius not exceeding 2,000 mm.
2 Normative References
The following documents contain provisions that, through reference in this text, constitute essential clauses of this document. For dated references, only the edition cited applies; for undated references, the latest version (including all amendments) applies.
GB/T 222 Permissible deviations in the chemical composition of steel and alloy
GB/T 223 (all parts) Chemical analysis methods for iron and steel
GB/T 228.1 Metallic materials – Tensile testing – Part 1: Method of test at room temperature
GB/T 228.2 Metallic materials – Tensile testing – Part 2: Method of test at elevated temperature
GB/T 241 Metallic tubes – Hydrostatic test method
GB/T 242 Metallic tubes – Flaring test method
GB/T 246 Metallic materials – Tubes – Flattening test method
GB/T 2102 Steel tubes – Acceptance, packaging, marking, and quality certificate
GB/T 2975 Steel and steel products – Location and preparation of test pieces for mechanical testing
GB/T 5777-2019 Automatic ultrasonic testing for full-circumferential defects in seamless and welded (except submerged arc welded) steel tubes
GB/T 6394 Methods for determining the average grain size of metals
GB/T 7735-2016 Automatic eddy current testing for defects in seamless and welded (except submerged arc welded) steel tubes
GB/T 10561-2023 Steel – Determination of non-metallic inclusion content – Standard chart rating method for microscopic examination
GB/T 10610 Geometrical product specifications (GPS) – Surface texture – Profile method – Rules and methods for assessing surface texture
GB/T 15250 Intergranular corrosion test method for nickel-based alloys
GB/T 20066 Steel and iron – Sampling and sample preparation for chemical analysis
GB/T 20123 Steel and iron – Determination of total carbon and sulfur content – Infrared absorption method after combustion in a high-frequency induction furnace (routine method)
GB/T 30062 Steel tube terminology
GB/T 38939 Nickel-based alloys – Determination of multi-element content – Spark discharge atomic emission spectrometry (routine method)
NB/T 47013.5-2015 Non-destructive testing of pressure equipment – Part 5: Penetrant testing
3 Terms and Definitions
The terms and definitions defined in GB/T 30062 apply to this document.
4 Classification and Codes
4.1 Classification by Delivery Condition
U-bend tubes are classified into the following two categories based on delivery condition:
Heat-treated U-bend tubes (U-H)
Cold-rolled (or cold-drawn) U-bend tubes (U-C)
4.2 Symbols and Explanations
The symbols and corresponding explanations used in this document are listed in Table 1.
5 Order Content
When ordering under this document, the contract or order shall include at least the following:
a) This document number;
b) Product name;
c) Grade or unified digital code;
d) Melting method;
e) Delivery condition;
f) Dimensions (outer diameter × wall thickness, in millimeters);
g) Product drawing (including bending radius and straight pipe length);
h) Order quantity (total length, total number of pieces, or total weight);
i) Hydrostatic test pressure;
j) Special requirements (e.g., penetrant testing).
6 Manufacturing Process
6.1 Melting Method
The alloy shall be refined by secondary refining (e.g., ladle furnace) or electroslag remelting, or other methods. The melting method shall be indicated in the quality certificate.
6.2 Tube Manufacturing Method
6.2.1 Alloy tube blanks shall be formed by hot rolling or hot forging.
6.2.2 Straight tubes shall be manufactured by cold-rolling (or cold-drawing) seamless method.
6.2.3 U-bend tubes shall be cold-bent into shape.
6.3 Delivery Condition
6.3.1 U-bend tubes are typically delivered as straight tubes after heat treatment in a protective atmosphere and subsequent cold bending. The recommended solution heat treatment system for straight tubes is provided in Table 2.
6.3.2 For U-bend tubes with a bending radius not exceeding 10 times the nominal outer diameter, the bent section and a straight section of at least 150 mm from the tangent point shall be stress-relieved before delivery. The recommended stress-relief heat treatment system is provided in Table 3.
6.3.3 Upon request by the purchaser and specified in the contract, U-bend tubes may also be delivered in the cold-rolled (or cold-drawn) condition after cold bending. The mechanical properties of U-bend tubes delivered in the cold-rolled (or cold-drawn) condition shall be agreed upon by the supplier and purchaser and specified in the contract.
Table 2 Recommended solution heat treatment system for straight tubes
Table 3 Recommended stress-relief heat treatment system
