Weld Testing

Destructive tests evaluate welds by loading samples to failure:

Tensile Testing:
Tests ultimate strength and ductility:
- Machine pulls sample until fracture
- Measures maximum load (tensile strength)
- Elongation indicates ductility
- Reduction of area measures necking
- Weld must meet base metal minimum strength

Guided Bend Tests:
Evaluate ductility and fusion:
- Sample bent around specified radius
- Root bend: root in tension
- Face bend: face in tension
- Side bend: cross-section in tension
- Examine for cracks, lack of fusion

Nick-Break Tests:
Quick assessment of internal quality:
- Notches machined at weld edges
- Sample broken by impact
- Fracture surface examined
- Reveals porosity, inclusions, fusion issues

Macro Examination:
Cross-section visual analysis:
- Section cut through weld
- Polish and etch to reveal structure
- Examine penetration, fusion, passes
- Measure dimensions against requirements

Charpy Impact Testing:
Evaluate toughness at temperature:
- Notched sample broken by pendulum
- Energy absorption measured
- Test at various temperatures
- Critical for low-temperature service

Hardness Testing:
Assess heat-affected zone properties:
- Rockwell, Brinell, or Vickers methods
- Traverse across weld zones
- Maximum hardness often specified
- Relates to cracking susceptibility

Fillet Weld Break Test:
Production test for fillet welds:
- Hammer or press breaks joint
- Examine fracture surface
- Verify fusion and penetration
- Quick in-process verification

Testing qualifies both procedures and welders:

Welding Procedure Specification (WPS):
Document specifying how to weld:
- Joint design and tolerances
- Base materials and thicknesses
- Filler metals and fluxes
- Electrical parameters
- Positions qualified
- Preheat and interpass temperatures
- Post-weld heat treatment

Procedure Qualification Record (PQR):
Documentation that WPS produces acceptable welds:
- Test coupon welded per WPS
- Record actual parameters used
- Destructive test results documented
- Qualifies WPS within essential variable ranges

Essential Variables:
Changes requiring requalification:
- Base metal group/thickness changes
- Filler metal changes
- Process changes
- Position changes
- Heat treatment changes
- Joint design changes beyond limits

Welder Performance Qualification (WPQ):
Tests individual welder skill:
- Weld test coupon per WPS
- Visual examination
- Bend tests or radiography
- Qualifies welder for specific ranges
- Requalification if not welding for extended period

Qualification Ranges:
Each test qualifies a range:
- Thickness: test plate qualifies a range (e.g., 1/8" to 2t)
- Position: higher positions may qualify lower
- Process: each process qualified separately
- Materials: groups allow qualification across similar materials

Documentation Requirements:
- Maintain qualification records
- Track welder continuity
- Audit supporting documentation
- Ensure current qualifications for production

Proper specimen preparation and testing technique are critical:

Specimen Preparation:

Cutting:
- Saw, torch, or plasma cut
- Remove heat-affected material if torch cut
- Label specimens for traceability

Machining:
- Tensile specimens to exact dimensions
- Bend specimens with specified radius edges
- Maintain dimensional tolerances
- Remove any notches or damage

Finishing:
- Surface finish per specification
- Consistent preparation across samples
- Remove burrs and sharp edges

Testing Machines:

Universal Testing Machine:
- Hydraulic or electromechanical
- Controlled loading rate
- Load cell measures force
- Extensometer measures elongation
- Data acquisition for records

Bend Test Fixtures:
- Guided bend jig with proper radius
- Adequate capacity for sample size
- Consistent loading rate
- Visual access during bending

Impact Test Machines:
- Calibrated pendulum
- Temperature control capability
- Energy measurement accuracy
- Proper sample positioning

Data Recording:
- Load vs. displacement curves
- Maximum load achieved
- Failure location
- Fracture surface photos
- Environmental conditions

Acceptance Criteria:
- Tensile: meet minimum specified strength
- Bend: no open defects > 1/8" in any direction
- Impact: energy above minimum at test temperature
- Hardness: below maximum specified
- Macro: no unacceptable discontinuities

Weld testing expertise supports multiple career directions:

Laboratory Positions:

Test Technician:
- Prepare specimens
- Operate testing equipment
- Record and report results
- $40,000-$55,000

Laboratory Supervisor:
- Manage testing operations
- Ensure quality of results
- Equipment calibration
- $55,000-$75,000

Metallurgist:
- Analyze test results
- Failure investigation
- Materials selection
- $70,000-$100,000

Field Positions:

Welding Inspector:
- Witness testing
- Review documentation
- Verify compliance
- $55,000-$85,000

QA/QC Engineer:
- Develop test requirements
- Interpret results
- Qualify procedures
- $65,000-$95,000

Welding Engineer:
- Specify testing requirements
- Solve production issues
- Procedure development
- $75,000-$110,000

Certifications:
- AWS CWI (welding inspection)
- ASNT NDT certifications (Level II, III)
- ASQ quality certifications
- PE (Professional Engineer) for some roles

Skills Development:
- Understanding of metallurgy
- Testing standards knowledge
- Statistical analysis
- Report writing
- Root cause analysis

Industries:
- Fabrication shops
- Construction companies
- Independent test labs
- Equipment manufacturers
- Engineering firms
- Government agencies

Education Paths:
- Welding technology degrees
- Materials engineering
- Metallurgical engineering
- Quality management

The combination of hands-on testing experience with theoretical understanding creates strong career foundation.