Welding Qualification

Weld Procedure Qualification (manufacturing-quality/special-processes/welding-qualification)

Use when the task is building and checking the engineering content of an aerospace weld procedure qualification record (WPS/PQR): computing the weld heat input in kJ per mm from the voltage, current, travel speed and process efficiency, verifying that the heat input, preheat and interpass temperature sit inside the qualified procedure values, confirming that the production weld thickness and joint configuration are covered by the qualified ranges, and listing the qualification test coupons required for the process and joint type. This leaf implements the checks in pure Python, stdlib only. It pairs with manufacturing-quality/special-processes/special-process-qualification, the change-driven neighbor that decides when a process change requires requalification. Welder personnel qualification and weld NDT interpretation are out of scope here.

Domain quick reference

• Heat input: HI = V * I * eta / (v * 1000), with V in volts, I in amperes, v in mm/s and eta the arc efficiency, giving kJ per mm. Heat input drives the weld cooling rate, bead geometry and heat affected zone, so the PQR records a qualified heat input window for the production run.
• Arc efficiency (typical practice values, confirm against the governing code): gtaw 1.0, gmaw 0.8, gma-pulse 0.85. GTAW is effectively direct energy delivery; the short circuit and pulsed modes lose part of the electrical power to radiation and spatter.
• Preheat: measured preheat must be at least the required minimum; margin = measured minus required. Interpass: measured interpass temperature must stay at or below the qualified maximum.
• Thickness coverage: a production weld thickness is covered when it falls inside the typical fraction window 0.75x to 2.0x of the qualified coupon thickness (typical practice, confirm against the governing code).
• Coupon matrix (documented typical aerospace practice set, confirm against the governing code, which for aerospace welding is commonly AWS D17.1): butt joints qualify with tensile x2, guided bend x4 and a volumetric acceptance (radiography at 100 percent; macro etch is the code-permitted substitute where radiography is impractical); fillet joints with macro etch x2 and fillet break x2; pipe joints with tensile x2, guided bend x4 and macro etch.
• AS9100 frames special process control within production control (clause context, referenced not reproduced); the module constants above are typical engineering practice, not standard text.
• Units: V, A, mm/s, kJ/mm, degC, mm.

Workflow

1. Identify the process (gtaw, gmaw, gma-pulse) and joint type (butt, fillet, pipe), and gather the electricals, travel speed, thicknesses and temperatures from the WPS/PQR and the production record.
2. Compute the heat input with heat_input_kj_mm using the process efficiency (default 1.0 gtaw, 0.8 gmaw, 0.85 gma-pulse).
3. Compare current, voltage and heat input against their qualified ranges with coverage_verdict; a None range means no window was stated and the check passes.
4. Verify the thermal requirements: preheat_margin_degC (non-negative margin means the minimum was met) and interpass_ok against the qualified maximum.
5. Confirm the production thickness sits inside the qualified coverage window with thickness_coverage on the coupon thickness.
6. Read the required test coupons for the process and joint from TYPICAL_COUPON_MATRIX.
7. Run qualification_summary for the combined verdict: all_ok and the findings list name each failed check (thickness-coverage, heat-input, current-range, voltage-range, interpass).
8. Validate inputs first: unknown process or joint, non-positive voltage, current, travel speed or thickness, a reversed qualified range, a required minimum preheat below absolute zero, or a non-positive interpass maximum raise ValueError instead of returning a silent verdict.

Worked example

GTAW butt weld, V = 11.5 V, I = 190 A, travel 1.8 mm/s, efficiency 1.0.

• Heat input: 11.5 * 190 * 1.0 / (1.8 * 1000) = 2185 / 1800 = 1.2139 kJ/mm.
• Qualified coupon thickness 6.35 mm, production 8.0 mm: covered when 4.7625 <= 8.0 <= 12.7, True. Production 4.0 mm is not covered (below 4.7625).
• Required minimum preheat 15 degC, measured 22 degC: margin +7 degC. Max interpass 150 degC, measured 96 degC: interpass_ok True.
• Qualified heat input range (0.8, 2.0): 1.2139 in-range. Current range (160, 220) A: 190 in-range. Voltage range (10.5, 13.0) V: 11.5 in-range.
• Coupon matrix gtaw/butt: ["tensile-x2", "guided-bend-x4", "radiography-100pct"].
• Summary: all_ok True, findings [].
• Fail case (production 4.0 mm, measured interpass 160 degC): all_ok False, findings ["thickness-coverage", "interpass"].
• GMA-pulse with the same electricals uses the 0.85 default: 11.5 * 190
  • 0.85 / 1800 = 1.0318 kJ/mm.

Verification

• Confirm heat_input_kj_mm(11.5, 190, 1.8, 1.0) returns 1.2139 kJ/mm within 1e-4, and the gma-pulse default case returns 1.0318.
• Confirm thickness_coverage(6.35, 8.0) gives lo_mm 4.7625, hi_mm 12.7, covered True, and thickness_coverage(6.35, 4.0) gives covered False.
• Confirm preheat_margin_degC(22, 15) returns 7 and interpass_ok(96,
  150. is True; interpass_ok(160, 150) is False.
• Confirm the gtaw/butt coupon list equals ["tensile-x2", "guided-bend-x4", "radiography-100pct"].
• Confirm the passing worked example gives all_ok True with findings [] and the fail case gives all_ok False with findings ["thickness-coverage", "interpass"].
• Confirm ValueError rejection of non-physical inputs: voltage 0, current -1, travel speed 0, process "smaw", joint "lap", production or qualified thickness 0, reversed qualified ranges, efficiency outside (0, 1], interpass maximum 0, and a required preheat below absolute zero.
• Run the contract test offline: python3 scripts/test_welding_qualification.py (33 tests, deterministic).

Related leaves

• manufacturing-quality/special-processes/special-process-qualification: the change-driven neighbor; it owns the requalification decision when a parameter, equipment or personnel change moves a welding process outside its qualified envelope. This leaf builds and checks the weld procedure qualification record content; that leaf decides whether a change re-triggers control.

Pitfalls

• Using the wrong arc efficiency: gtaw defaults to 1.0 while gmaw (0.8) and gma-pulse (0.85) lose part of the electrical power to radiation and spatter - the same electricals give 1.2139 kJ/mm on GTAW and 1.0318 kJ/mm on GMA-pulse, so an efficiency mismatch mis-qualifies the heat input window.
• Judging preheat and interpass as one rule: preheat needs the measured value at least at the required minimum (margin >= 0), while interpass must stay at or below the qualified maximum - the two bounds fail in opposite directions and both appear in the findings.
• Releasing a production weld outside the thickness window: coverage is 0.75x to 2.0x of the qualified coupon thickness, so an 8.0 mm weld qualifies off a 6.35 mm coupon but a 4.0 mm weld does not.
• Reading an unstated range as a failure: a None range means no window was declared and the coverage check passes - only a stated, reversed or exceeded range fails.
• Treating the coupon matrix as code text: the tensile x2, guided bend x4, radiography and macro etch set is documented typical aerospace practice commonly governed by AWS D17.1 - confirm the matrix against the governing code, and note macro etch only substitutes where radiography is impractical.
• Confusing this leaf with the requalification decision: it builds and checks the WPS/PQR engineering content; whether a process, equipment or personnel change re-triggers control belongs to special-process-qualification, and welder personnel qualification and weld NDT interpretation are out of scope here.

Behavior contract (gate 3)

Run the deterministic contract test (stdlib unittest, offline):

python3 scripts/test_welding_qualification.py

The test covers the worked example anchors (gtaw heat input 1.2139 kJ/mm, gma-pulse 1.0318 kJ/mm at the 0.85 efficiency default), the efficiency defaults per process, coverage verdict branches including the inclusive boundaries and the None range, thickness coverage bounds 4.7625 and 12.7 mm with the 4.0 mm failure case, the preheat margin +7 and interpass checks, the coupon matrix contents per process and joint, the qualification_summary passing and failing cases with their findings, and ValueError rejection of every non-physical input class.

Compliance

• AS9100 is referenced for special process control context only, not reproduced; standards-map.yaml governs the citation form.
• The coupon matrix, arc efficiencies and thickness fractions are documented typical aerospace engineering practices, paraphrased from common industry practice; they are not reproductions of AWS D17.1 or AS9100 text. Confirm each against the governing code for the program before releasing a procedure.
• compliance: STANDARDS-REF, gated: false.