How is the welding quality of structural components inspected?

How to inspect the welding quality of structural components: ① Appearance—Visual Testing (VT) for cracks, undercut, weld reinforcement, and dimensions (Eurolab/AWS D1.1); ② Internal—Ultrasonic Testing (UT), Phased Array (PAUT), or TOFD for lack of fusion, lack of penetration, porosity, and cracks (for wall thickness >8mm); ③ Surface—Magnetic Particle Testing (MT) for ferromagnetic materials or Liquid Penetrant Testing (PT) for surface cracks (GB50766); ④ Process—Visual inspection must pass before Non-Destructive Testing (NDT); re-inspection for questionable results (GB50567/GB50766); ⑤ Standards—GB50661/GB50567, ASME, ISO 17640, AWS D1.1. In summary: Inspect structural component welding quality via visual inspection (VT) for appearance (cracks/undercut/reinforcement);
internal inspection via UT/PAUT/TOFD or Radiographic Testing (RT) for internal defects (lack of fusion/penetration, porosity, cracks; wall thickness >8mm); and surface inspection via MT/PT; ensure visual inspection passes before NDT and re-inspect questionable areas; conduct inspections according to GB50661/GB50567, ASME, ISO 17640, and AWS D1.1.

I. Visual and Surface Inspection (2026 Standard)

Visual and surface inspection of structural weldments (consolidated from Eurolab, GB50766, and industry practices):

• Visual Testing (VT): Initial check for cracks, undercut, weld reinforcement, and dimensions—visual inspection;
• Magnetic Particle Testing (MT): Detection of surface and near-surface cracks in ferromagnetic materials—magnetic particle method;
• Liquid Penetrant Testing (PT): Detection of surface cracks; applicable to non-ferromagnetic materials—penetrant method;
• Appearance: Visual inspection/5x magnification;
  MT or PT used if necessary—appearance check;
• Conclusion: Visual acceptance precedes non-destructive testing (NDT)—conclusion.

II. Internal Non-Destructive Testing (2026 Standard)

Internal non-destructive testing of structural weldments (consolidated from zxweldingrobot, weldfabworld, GB50567, and industry practices):

• Ultrasonic Testing (UT): Detection of internal lack of fusion, incomplete penetration, porosity, and cracks; for wall thickness >8mm—ultrasonic method;
• Phased Array: PAUT (Phased Array UT) and TOFD (Time-of-Flight Diffraction) for shop welds—phased array methods;
• Radiographic Testing (RT): Detection of internal defects when necessary—radiographic method;
• Standards: ASME V/ISO 17640, GB50661—standards;
• Conclusion: UT is the most common method; RT is used to verify thick plates—conclusion.

III. Overseas B-Side Procurement and Implementation (2026 Standards)

Overseas B-side acceptance process for structural component weld quality (based on industry best practices and case studies):

• Define requirements: Welding inspection standards (GB/AWS/ISO) and weld classifications;
• Initial visual inspection (VT): Check for cracks, undercut, and weld reinforcement; magnetic particle/dye penetrant testing;
• Internal inspection: Ultrasonic testing (UT)/phased array, radiographic testing (RT) for thick plates, and inspection reports;
• Verify qualifications: Welder certifications, NDT technician certifications, and inspection reports;
• Risk assessment: Check for lack of fusion and incomplete penetration; verify inspection ratios and certificate validity.

Conclusion

How is the welding quality of structural components inspected? In short: Surface appearance (visual inspection/VT for cracks, undercut, reinforcement height, and dimensions is the first step to detect visible defects; weld appearance should be checked visually or with 5x magnification, using magnetic particle or penetrant testing if necessary; internal inspection should use ultrasonic testing, with radiographic testing as needed—per T/CUPC Code for Quality Inspection and Evaluation of Welding of Building Steel Structures; surface quality inspection uses magnetic particle testing (MT) or penetrant testing (PT)—MT is preferred for ferromagnetic materials, and a secondary method is used to verify questionable results—per GB50766); Internal non-destructive testing (ultrasonic testing (UT), phased array (PAUT), and time-of-flight diffraction (TOFD); common internal defects in shop welds include lack of fusion, incomplete penetration, porosity, and cracks, especially in wall thicknesses >8mm; UT angle probes detect cracks, lack of fusion, porosity, laminations, and inclusions in various directions—standards ASME V/ISO 17640; MT detects surface and near-surface defects via magnetic flux leakage); NDT procedures (NDT follows a satisfactory visual inspection; internal inspection of full-penetration and partial-penetration welds uses UT or RT; UT follows JB/T 4730.3—per GB50567; UT uses high-frequency sound waves reflecting within the weld to detect internal defects, suitable for thick welds); Standards (five AWS methods: RT-radiographic, UT-ultrasonic, MT-magnetic particle, PT-penetrant, VT-visual; AWS D1.1 §6); 2026 welding inspection trends (phased array/TOFD/AI-based visual inspection).
Overseas B2B procurement strategy for structural weld quality: Define requirements (welding inspection standards such as GB/AWS/ISO, weld classes); verify surface quality (visual inspection [VT] for cracks, undercut, and reinforcement height; magnetic particle or penetrant testing); verify internal quality (ultrasonic testing [UT]—phased array/PAUT; radiographic testing [RT] for thick plates; review reports); verify qualifications (welder certificates, NDT technician certificates, inspection reports);
and mitigate risks (check for lack of fusion/penetration, inspection ratios, and certificate validity). Sources for data and case studies: Surface inspection (Eurolab: Visual inspection [VT] for cracks and lack of fusion is the first step; UT detects deep-seated defects; T/CUPC Code for Quality Inspection and Assessment of Welding for Steel Structures: Visual inspection or 5x magnification for appearance, with magnetic particle or penetrant testing as needed; UT for internal inspection, with RT as needed; GB50766: Surface quality via magnetic particle [MT] or penetrant testing [PT]; MT preferred for ferromagnetic materials, with the other method used for verification in case of doubt); Internal NDT (zxweldingrobot: UT—Phased Array [PAUT] and Time-of-Flight Diffraction [TOFD]; common internal defects in shop welds include lack of fusion, lack of penetration, porosity, and cracks, especially in wall thicknesses >8mm; weldfabworld: UT angle probes detect cracks, lack of fusion, porosity, laminations, and inclusions in various directions; standards ASME V/ISO 17640; MT detects surface/near-surface defects via magnetic flux leakage; GB50567: NDT follows successful visual inspection; UT or RT for internal inspection of full- and partial-penetration welds; UT per JB/T 4730.3; vsg: High-frequency UT sound waves reflect off internal defects in thick welds); Standards (zxweldingrobot: Five AWS methods—RT, UT, MT, PT, VT; AWS D1.1 §6); and 2026 trends in welding inspection (Phased Array/TOFD/AI-based visual inspection).
Sources: Eurolab, T/CUPC, GB50766, zxweldingrobot, weldfabworld, GB50567, vsg.