CWB Welding Inspector Level 3 cheat sheet

Heat input (kJ/mm) = (volts × amps × 60) ÷ (travel speed in mm/min × 1000); halving travel speed doubles heat input.

SMAW polarity: DCEN places roughly two-thirds of arc heat in the workpiece (deeper penetration, cooler electrode); DCEP reverses this and improves cleaning. Cellulosic electrodes run on DC only.

GMAW transfer mode is set by current density and gas: short-circuit at low current/voltage (sheet metal, all positions), globular at intermediate, spray above the transition current with argon-rich gas (flat and horizontal only).

GTAW uses a non-consumable tungsten electrode: DCEN for carbon and stainless steel, AC for aluminium to break the oxide film; filler is added separately.

SAW buries the arc under granular flux, permits roughly 300–1500 A, gives the highest deposition rate, but is restricted to flat and horizontal positions; flux must be dry and matched to the wire.

FCAW: self-shielded wires need no external gas and tolerate wind; gas-shielded wires use CO2 or Ar/CO2. Basic (calcium fluoride) fluxes give lower hydrogen and better toughness than rutile types.

Duty cycle is arc time within any 10-minute period: 60% at 300 A means 6 minutes arcing and 4 minutes cooling; exceeding the rated duty cycle overheats the power source.

Arc blow is a DC magnetic effect, worst at high current and near joint ends; controls are AC, shorter arc, lower current, backstep sequence, or relocating the work connection.

IIW carbon equivalent = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15; values above about 0.40–0.45 signal a need for preheat and hydrogen control.

Hydrogen-assisted cracking requires four conditions simultaneously: dissolved hydrogen, a hard martensitic microstructure, tensile stress, and a temperature near ambient. Preheat, low-hydrogen consumables and slow cooling remove them.

E7018 is a basic low-hydrogen electrode with 70 ksi minimum tensile strength, all-position capability; hold it in a heated oven near 120 °C and redry at about 370–430 °C after moisture pickup.

E6010 (cellulosic) gives deep penetration, fast freeze and high hydrogen, and runs on DC only; E7024 (rutile, iron powder) gives high deposition but is limited to flat and horizontal work.

Austenitic 300-series stainless is sensitized between roughly 425 °C and 815 °C, where chromium carbides precipitate and leave chromium-depleted grain boundaries; low-carbon (L) or stabilized grades resist this.

Aluminium: remove the oxide film immediately before welding, generally no preheat on thin sections, 4043 filler for general work and 5356 for higher strength or anodized parts.

Strength matching is the normal rule for steel filler metals; undermatching (for example 309L on a dissimilar joint) is chosen where cracking resistance outweighs joint strength.

Shielding gas: CO2 is reactive, gives deep penetration and a rougher bead; argon is inert and smoother; Ar/CO2 mixes balance both. GMAW flow is typically 12–20 L/min.

CSA W47.1 certifies companies for fusion welding of steel structures, with divisions 1, 2, 2M and 3 based on demonstrated capability; CSA W47.2 is the parallel aluminium standard.

CSA W59 governs welded steel construction and defers to W47.1 for company and personnel qualification; welding symbols follow AWS A2.4.

AWS D1.1: joints detailed in the code with variables inside the prequalified limits require no procedure testing; anything outside those limits requires a qualified WPS.

Essential variables (process, filler classification, position, preheat, among others) require requalification when changed beyond code limits; nonessential variables do not.

ASME IX groups base metals by P-number, ferrous filler metals by F-number, and austenitic/stainless fillers by A-number; qualification on one P-number covers the other metals in its group.

API 1104 governs pipeline girth welds with its own procedure and welder qualification, acceptance criteria and NDE requirements; it is not interchangeable with AWS D1.1.

CSA W178.2 certifies welding inspectors at Levels 1, 2 and 3; the level determines the scope of inspection, supervision and approval authority.

Codes set minimum acceptance limits such as undercut depth, porosity size and reinforcement; a contract may add requirements but cannot relax the code without documented approval.

A WPS is the written instruction; a PQR is the record of the test that proved it. The PQR supports the WPS but is not a work instruction.

Procedure qualification tests normally include reduced-section tensile, guided bend (root and face), and impact testing where toughness is specified; all must pass before the WPS is issued.

ASME IX QW-451 thickness rule: a groove coupon of thickness T qualifies a base-metal range from 1.5 mm (5 mm when T exceeds 10 mm) up to 2T.

Welder performance qualification is specific to process, position, filler or electrode type and thickness range, and must be renewed after the code-defined period or a lapse in welding.

Positions: 1G flat, 2G horizontal, 3G vertical, 4G overhead; 6G is a pipe fixed at 45° without rotation and qualifies the widest range of pipe positions.

Guided bend specimens are bent 180° over a code-specified radius; discontinuities appear as cracks or open defects on the tension surface. Specimen thickness and radius are set by the code.

The WPS must be available at the work station and followed; a deviation beyond the essential variables makes the weld nonconforming regardless of test results.

Qualification records must be signed, dated, traceable to the test coupon and retained as auditable evidence of procedure and welder capability.

Visual inspection occurs before, during and after welding: fit-up, root condition, interpass cleaning, final profile, undercut, weld size and welder identification.

PT detects surface-breaking defects in any material; the surface must be clean and dry, penetrant dwell is typically 5–10 minutes, and the developer draws penetrant back out of the discontinuity.

MT detects surface and near-surface defects in ferromagnetic steel; AC is mainly for surface indications, DC or rectified current reaches slightly deeper, and the part is magnetized in two roughly perpendicular directions.

UT with angle-beam shear waves detects planar internal defects such as lack of fusion, cracks and incomplete penetration; it requires a calibrated reference block and a written technique.

RT reveals volumetric defects (porosity, slag) as density differences; sensitivity is verified with a penetrameter (IQI), and geometric unsharpness is minimized by a small source, large source-to-object distance and film close to the part.

Fillet weld size: for a 45° equal-leg fillet, theoretical throat = 0.707 × leg length; convexity adds surface metal but not throat, and excessive convexity is rejectable under some codes.

Destructive tests: tensile for strength, guided bend for ductility, nick-break for internal defects, macro-etch for fusion and HAZ examination, hardness for cracking risk.

Before any NDE, confirm procedure, personnel certification, equipment calibration and surface condition, then record technique, parameters, results and the unique part or weld identification.

QA is the planned system that prevents defects (procedures, training, audits); QC is the inspection and testing that detects them. QA manages the QC function.

The inspection and test plan (ITP) lists activities, acceptance criteria, responsible parties, and hold or witness points in production sequence.

Hold point: work cannot proceed until the inspector has verified and signed. Witness point: the inspector is notified and may attend, but work may proceed if they do not.

A nonconformity report records the requirement, the actual condition, the disposition (rework, repair, concession or reject) and the corrective action taken.

Corrective action eliminates the root cause so the defect cannot recur; containment stops defective product from progressing. Both are required after a significant nonconformity.

Audits may be internal or external and system, process or product based; findings are graded major or minor, and closure requires objective evidence.

Calibration of NDE and measuring equipment must be current and traceable; results produced by an out-of-calibration instrument are invalid and require re-inspection.

Records under control include WPS and PQR, welder certificates, consumable storage records, NDE reports, calibration certificates, nonconformance and audit reports, retained per code or contract.