GB/T 14976 – Seamless Steel Tubes for Fluid Transportation

1. Scope  

- Applies to seamless steel tubes used for conveying fluids (e.g., water, oil, gas).  

- Covers hot-rolled (extruded) and cold-drawn (cold-rolled) tubes.  

2. Normative References  

- References other GB standards for testing, dimensions, and material properties (e.g., GB/T 222, GB/T 223, GB/T 241).  

3. Ordering Information  

Buyers must specify:  

- Steel grade (e.g., 10, 20, 16Mn, 304, 316L).  

- Dimensions (outer diameter, wall thickness, length).  

- Manufacturing process (hot-rolled/cold-drawn).  

- Special requirements (e.g., heat treatment, non-destructive testing).  

4. Steel Grades and Chemical Composition  

- Common grades include carbon steel (10, 20), low-alloy steel (16Mn), and stainless steel (304, 316L).  

- Chemical composition must comply with specified limits (e.g., C, Si, Mn, P, S, Cr, Ni for stainless steels).  

5. Manufacturing Process  

- Tubes are produced via hot rolling, cold drawing, or cold rolling.  

- Heat treatment (annealing, normalizing, or quenching/tempering) is required for certain grades.  

6. Technical Requirements  

- Dimensions & Tolerances: Must meet GB/T 17395 standards.  

- Mechanical Properties: Tensile strength, yield strength, elongation per grade.  

- Hydrostatic Test: Mandatory (test pressure calculated per formula).  

- Surface Quality: Free from cracks, folds, and severe scratches.  

- Non-Destructive Testing (NDT): Ultrasonic or eddy current testing if specified.  

7. Inspection and Testing  

- Chemical analysis (per GB/T 222/223).  

- Mechanical tests (tensile, hardness, flattening, flaring, etc.).  

- Hydrostatic/NDT tests.  

- Sampling frequency: Batch-wise (e.g., 10% for mechanical tests).  

8. Marking and Packaging  

- Tubes are marked with steel grade, size, standard number, and manufacturer’s name.  

- Packaging: Bundled or crated with rust-proof measures for transport.  

9. Certification  

- Manufacturer provides a quality certificate including test results and compliance statement.  

Key Notes  

- Latest Version: Confirm if GB/T 14976-XXXX (replace XXXX with the current year) supersedes older editions.  

- Stainless Steel Grades: Added in recent updates (e.g., 304, 316L).  

- NDT Emphasis: Enhanced inspection requirements in newer versions.  

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