Inspect welds to ensure quality and structural integrity. Learn about visual weld inspection, NDT methods, welding codes, and acceptance criteria.
Introduction
Welding inspection ensures that welded joints meet quality and performance requirements. Poor weld quality can lead to structural failure, leakage, or product malfunction. At Fulei Metal, we implement comprehensive welding inspection to ensure the integrity of our welded products.
Importance of Welding Inspection
Structural Integrity
Welds are often critical to product strength and safety. Weld defects can: reduce strength, create stress concentrations, cause fatigue failure, lead to catastrophic failure. Inspection verifies that welds meet strength requirements.
Quality Assurance
Welding inspection provides: objective evidence of weld quality, process feedback for improvement, customer confidence, compliance with codes and standards, documentation for traceability.
Cost Reduction
Early detection of weld defects: reduces rework cost, prevents assembly of defective components, avoids customer returns, identifies process problems quickly.
Visual Weld Inspection
What is Visual Weld Inspection?
Visual inspection is the first and most important weld inspection method. It identifies surface defects and verifies weld appearance, size, and profile. Most weld defects can be detected visually.
Pre-Weld Inspection
Verify: joint preparation is correct, dimensions and fit-up are correct, surfaces are clean, welding parameters are set correctly, welder is qualified, filler metal is correct, shielding gas is correct.
In-Process Inspection
Monitor during welding: weld sequence, travel speed, arc characteristics, interpass temperature, interpass cleaning, distortion.
Post-Weld Visual Inspection
Inspect completed weld for: weld size and length, weld profile and shape, surface defects, weld location, weld cleanup.
Weld Profile Measurement
Weld size: measure leg length and throat thickness for fillet welds. Weld reinforcement: measure height above surface for butt welds. Weld width: measure weld width. Tools: weld gauge, bridge cam gauge.
Surface Defects to Look For
Cracks: longitudinal, transverse, crater. Porosity: surface pores or pits. Undercut: groove at weld toe. Overlap: weld metal flowing onto surface without fusion. Spatter: metal droplets on surface. Arc strikes: marks outside weld area. Incomplete fill: weld not filled to required level. Excessive convexity: weld too convex.
Non-Destructive Testing (NDT)
Dye Penetrant Testing (PT)
Detects surface-breaking defects. Process: clean surface, apply penetrant, remove excess, apply developer, inspect for indications. Detects: cracks, porosity, laps, seams. Suitable for: any non-porous material. Low cost, simple to perform.
Magnetic Particle Testing (MT)
Detects surface and near-surface defects in ferromagnetic materials. Process: magnetize part, apply magnetic particles, inspect for indications. Detects: cracks, inclusions, seams, laps. Suitable for: steel and iron. Faster than penetrant testing. Can detect some sub-surface defects.
Radiographic Testing (RT)
Uses X-rays or gamma rays to detect internal defects. Process: place film or digital detector behind weld, expose to radiation, inspect image. Detects: porosity, inclusions, incomplete penetration, incomplete fusion, cracks. Provides permanent record. Suitable for: most materials. Higher cost, requires safety precautions.
Ultrasonic Testing (UT)
Uses high-frequency sound waves to detect internal defects. Process: apply couplant, scan with probe, analyze echoes. Detects: cracks, inclusions, incomplete fusion, laminations. Suitable for: most materials. High sensitivity. Requires skilled operator. No permanent record (unless phased array).
Phased Array Ultrasonic Testing (PAUT)
Advanced UT with multiple elements. Provides: beam steering, beam focusing, real-time imaging. Higher sensitivity than conventional UT. Permanent record. Suitable for: complex geometries, critical welds.
Eddy Current Testing (ET)
Uses electromagnetic induction to detect surface and near-surface defects. Detects: cracks, corrosion, material variations. Suitable for: conductive materials. Fast, no couplant needed. Common for: tubing, surface inspection.
Destructive Testing
Tensile Testing
Test weld strength by pulling to failure. Determines: tensile strength, yield strength, elongation. Verifies weld metal strength meets requirements. Specimen: machined from welded plate.
Bend Testing
Bend welded specimen to verify ductility and soundness. Types: face bend, root bend, side bend. Reveals: defects in weld metal and heat-affected zone. Simple and inexpensive.
Macro Examination
Cut and polish cross-section of weld. Examine at low magnification (10-50x). Reveals: weld penetration, weld profile, internal defects, fusion zone, heat-affected zone. Used for: procedure qualification, welder qualification.
Hardness Testing
Measure hardness of weld metal, heat-affected zone, and base metal. Identifies: hard brittle zones, soft zones. Verifies heat treatment effectiveness. Methods: Vickers, Rockwell, Brinell.
Impact Testing
Test weld toughness at specified temperature. Charpy V-notch test. Determines: absorbed energy, transition temperature. Critical for: low-temperature applications, dynamic loading.
Welding Codes and Standards
ISO Standards
ISO 5817: quality levels for imperfections in steel welds. ISO 10042: quality levels for aluminum welds. ISO 15614: welding procedure qualification. ISO 9606: welder qualification.
AWS Standards
AWS D1.1: structural welding code for steel. AWS D1.2: structural welding code for aluminum. AWS D1.3: sheet steel welding. AWS D1.6: stainless steel welding.
EN Standards
EN ISO 5817: same as ISO 5817. EN 1090: execution of steel structures. EN ISO 3834: quality requirements for welding.
Acceptance Criteria
Each standard defines: what defects are acceptable, what defect sizes are acceptable, what inspection is required, how inspection is performed. Acceptance levels: typically Level B (stringent), Level C (intermediate), Level D (moderate). Level depends on application and criticality.
Welder Qualification
Why Qualify Welders?
Welder qualification verifies that the welder can produce sound welds. It ensures consistent quality. It is required by most welding codes. It provides documentation of capability.
Qualification Process
Welder performs test weld per procedure. Test weld is inspected: visual inspection, radiographic or ultrasonic testing, destructive testing (bend, macro). If all tests pass, welder is qualified. Qualification is valid for a specified period. Re-qualification required for: expiration, new process, new material, new position.
Qualification Records
Maintain welder qualification records. Include: welder name, process, material, thickness range, position, qualification date, expiry date. Track qualifications to ensure currency.
Welding Procedure Specification (WPS)
What is a WPS?
A WPS documents the welding parameters for a specific joint. It provides: instructions for the welder, assurance of repeatable quality, compliance with code requirements.
WPS Contents
Joint design, base metal, filler metal, welding process, shielding gas, preheat temperature, interpass temperature, welding position, travel speed, current and voltage, heat input. Supporting Procedure Qualification Record (PQR) verifies the WPS produces sound welds.
Inspection Documentation
Inspection Reports
Document all welding inspection results. Include: weld identification, inspection method, acceptance criteria, results, inspector, date. Maintain for traceability.
NDT Reports
Document NDT results. Include: weld identification, NDT method, procedure, acceptance standard, results (pass/fail), indications found, technician, date. NDT technician must be qualified.
Weld Map
Drawing showing all weld locations. Each weld is numbered. Inspection results are recorded for each weld. Provides complete weld traceability.
At Fulei Metal
Our welding inspection program includes: visual inspection of all welds. Welder qualification per ISO 9606. Welding procedure specifications (WPS). Dye penetrant testing for critical welds. Radiographic testing when required. Macro examination for procedure qualification. Weld gauge measurement. Documentation and traceability. We ensure that our welds meet the quality requirements of our global clients.
Conclusion
Welding inspection is essential for ensuring the quality and integrity of welded products. At Fulei Metal, our comprehensive welding inspection program provides confidence that our welded products meet the structural and quality requirements of our international clients.