CWE cheat sheet

Arc flash and fume control: welding arcs emit UV/IR radiation, so use a filter shade matched to process and current (e.g., higher shade for high-current GMAW/FCAW); local exhaust ventilation is the control for fume, and confined-space entry requires atmospheric testing before and during welding.

Electrical shock risk rises with open-circuit voltage and damp conditions: SMAW OCV commonly 50-80 V, GTAW with high-frequency start is higher; wet gloves, sweat-soaked clothing, and secondary-circuit ground connections to structure are the classic failure paths.

Fire prevention rule: combustibles within 11 m (35 ft) of the work must be moved or protected; if not possible, use guards and a fire watch that continues at least 30 minutes after welding ends.

Tensile test outputs: yield strength at 0.2% offset, ultimate tensile strength, percent elongation, and percent reduction of area; a specimen that fails below the specified minimum UTS or shows ductility below the WPS/PQR requirement fails the test.

Guided bend testing: face and root bends evaluate ductility and fusion at the weld faces; a bend specimen is acceptable when no single defect exceeds the applicable discontinuity size limit (commonly 3 mm / 1/8 in in the open-cut surface) after bending.

Impact (Charpy V-notch) testing measures absorbed energy in joules at a stated test temperature; ferritic steels show a ductile-to-brittle transition, so test temperature must always be reported with the energy value.

Metallurgy basics: the heat-affected zone is unfused base metal altered by welding heat; carbon equivalent (CE = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15) above roughly 0.40 raises hardenability and cold-cracking risk, driving preheat and hydrogen control.

Welding symbol anatomy: reference line, arrow, tail (process/specification reference), plus supplementary symbols; the size is placed left of the fillet or groove symbol, length right, pitch after length, and the other side of the joint is shown below the reference line.

Inspection principles: VT, PT, and MT detect surface and near-surface discontinuities; UT and RT detect internal ones. PT requires a clean, non-porous surface, MT applies only to ferromagnetic materials, and RT is sensitive to density/thickness changes and orientation of planar defects.

WPS/PQR chain: the PQR records the test coupon and results that qualified a procedure; the WPS is written from that qualification and must be available at the point of use; the welder is separately qualified to the WPS (performance qualification), and neither substitutes for the other.

Essential variable rule: a change beyond the qualified range in an essential variable (e.g., process, filler classification, base-metal group, thickness range, preheat/interpass range, PWHT) requires requalification; non-essential changes only need WPS revision.

Preheat and interpass control: measure preheat at least 75 mm (3 in) from the joint on both sides before welding, verify with contact thermometers, temp sticks, or thermocouples, and cap interpass temperature per the WPS to preserve toughness.

Fillet weld inspection tools: use a fillet weld gauge or a leg/ throat gauge to check leg length and theoretical throat (throat = 0.707 x leg for equal-leg 90-degree fillets); use a bridge cam gauge for undercut, and a V-WAC gauge for cap height and pit depth.

Undercut and reinforcement measurement: a pit gauge or the wire/tape method measures depth; acceptance limits are specified per code and joint type, so compare measured values against the WPS or applicable acceptance criteria rather than a general rule.

Fit-up and alignment: check root gap, root face, bevel angle, and mismatch before welding; high-low misalignment concentrates stress and can exceed the code's allowable offset, so correct fit-up rather than compensating with weld metal.

Welding execution sequence: clean to bright metal, set polarity and amperage per WPS, control travel speed to keep bead shape and penetration consistent, and record actual parameters (amps, volts, travel speed) so they can be compared to the WPS range.

Distortion control: use balanced welding sequence, backstep or skip welding, preset, and restrained fixtures; keep heat input within the WPS range because excessive heat input reduces strength and toughness in the HAZ.

Post-weld and documentation: remove slag, verify weld profile and dimensions, perform required NDT before any PWHT or coating, and complete traceability records linking heat numbers, filler lots, WPS/PQR, and welder ID.