IIW IWI-B cheat sheet

SMAW: electrode coating generates shielding gas and slag; current type and polarity are set by the electrode classification, and cellulosic electrodes are used for vertical-down root passes on pipe.

GMAW transfer modes: short-circuit (low current, thin plate), globular (intermediate), spray (above transition current, argon-rich gas), and pulsed spray for positional work.

GTAW uses a non-consumable tungsten electrode; DCEN concentrates heat at the workpiece for steel, DCEP is rarely used because it ballasts the tungsten, and AC is used for aluminium to break the oxide.

SAW achieves high deposition with granular flux and no visible arc; it is limited to flat and horizontal positions and to mechanised or automatic operation.

Heat input formula: HI (kJ/mm) = (V x I x 60) / (1000 x v), where V is arc voltage in volts, I is current in amps, and v is travel speed in mm/min.

FCAW with rutile flux gives smooth positional welding, while basic (fluoride) flux gives better toughness and hydrogen control but poorer positional tolerance.

Process efficiency for heat input: SAW approximately 1.0, GMAW approximately 0.8, SMAW approximately 0.8, GTAW approximately 0.6; multiply arc heat input by the process factor.

Resistance spot welding current path is controlled by electrode force and tip geometry; expulsion indicates excessive current or insufficient force.

Carbon equivalent (IIW formula): CE = C + Mn/6 + (Cr+Mo+V)/5 + (Cu+Ni)/15; values above about 0.40 % raise cold-cracking risk and require preheat or hydrogen control.

Hydrogen cracking requires three simultaneous conditions: susceptible microstructure, diffusible hydrogen, and tensile restraint stress; remove any one and cracking is prevented.

Carbon steel HAZ hardens with increasing cooling rate; t8/5 cooling time decreases with higher heat input and higher preheat, softening the transformation product.

Austenitic stainless steel solidifies as either ferrite-austenite (A mode) or austenite-ferrite (F mode) depending on Cr/Ni equivalent; a ferrite number of 3-10 resists solidification cracking.

Sensitisation of austenitic stainless steel occurs by chromium carbide precipitation at grain boundaries in the 450-850 C range, reducing corrosion resistance; low-carbon grades or stabilised grades avoid it.

Aluminium alloy 6082 is heat-treatable and loses strength in the HAZ; 5083 is non-heat-treatable and work-hardens, so softens in the annealed zone.

Hydrogen solubility in steel drops sharply on solidification from austenite to ferrite, so residual hydrogen concentrates in the remaining liquid and promotes porosity and cracking.

Copper and nickel alloys have high thermal conductivity, requiring high heat input and preheat to achieve fusion.

Weld joint types: butt, T-joint, lap, corner, and edge; weld types are groove, fillet, plug, and spot, and the two classifications are independent.

Fillet weld throat thickness a = 0.7 x leg length for equal-leg 90 degree fillets; design throat is used for strength calculation, not the leg.

Butt weld effective throat equals the plate thickness for full penetration; partial penetration grooves use the specified groove depth less any root gap allowance.

Fatigue design: weld toes and roots are stress concentrations; toe grinding, TIG dressing, and peening improve fatigue life by removing intrusions and reducing stress concentration.

Weld symbols: a reference line with arrow, a symbol above for the arrow side and below for the other side; a tail carries process or specification references.

Structural steel design uses partial safety factors on resistance; weld design strength is reduced by a correlation factor for fillet welds in some codes.

Distortion control: balanced welding about the neutral axis, back-step sequence, presetting, and minimising heat input reduce angular and longitudinal shrinkage.

Restraint intensifies residual stress; design should allow shrinkage movement where possible and avoid abrupt section changes at weld locations.

Visual inspection before welding checks joint preparation, fit-up, gap, bevel angle, cleanliness, and consumable condition; during welding it checks preheat, interpass temperature, and technique.

Undercut reduces throat thickness; acceptance limits are usually expressed as a maximum depth (often 0.5 mm) and a maximum length relative to weld length.

Porosity acceptance is normally by size and distribution; clustered or linear porosity indicates contamination or gas entrapment rather than isolated random gas.

Surface-breaking cracks are detected by magnetic particle (ferromagnetic only) or penetrant testing (non-porous surfaces); neither detects internal defects.

Ultrasonic testing detects planar internal defects such as lack of fusion and cracks; radiography is better for volumetric defects such as porosity and slag.

Weld measurement: fillet leg and throat gauges, undercut gauges, and hi-lo gauges for misalignment; misalignment limits are typically 10 percent of thickness or 3 mm, whichever is smaller.

WPS qualification follows a pWPS, then a WPQR by testing, then a WPS; welder qualification is separate and tests the operator, not the procedure.

Essential variables in a WPS include process, base metal group, thickness range, filler classification, preheat, interpass temperature, and heat input range.

ISO 3834 defines quality requirements for fusion welding: Part 2 comprehensive, Part 3 standard, Part 4 elementary; selection depends on product criticality and contractual requirement.

Welding coordination personnel are required by ISO 14731; the IWI/IWE/IWT hierarchy defines task ranges and responsibility levels.

ISO 9606 covers welder qualification by test; ISO 15614 covers procedure qualification by test; both define essential variables and validity ranges.

Non-destructive testing personnel are certified to ISO 9712 levels 1, 2, and 3; level 2 may perform and interpret, level 3 may approve procedures.

Traceability requires documented linkage of base metal certificate, filler batch, WPS, welder ID, and NDT report to each weld.

EN 1090-2 governs execution of steel structures and defines execution classes EXC1 to EXC4 with increasing inspection and documentation demands.

Calibration of measuring and testing equipment must be traceable to national or international standards, with records retained.

Nonconformity handling: identify, segregate, record, disposition (repair, rework, concession, or scrap), and verify after repair.

Arc eye (photokeratitis) is caused by ultraviolet radiation; protection requires a filter shade matched to process and current, plus side shields.

Fume extraction at source is the primary control; welding fume is classified as carcinogenic to humans (Group 1) and manganese exposure affects the nervous system.

Ozone forms in GTAW and plasma welding from UV action on air; argon shielding does not remove it, so ventilation is required.

Shielding gas asphyxiation risk in confined spaces: argon and CO2 displace oxygen; entry requires gas testing and continuous monitoring.

Fire watch: hot work permits, removal of combustibles within 10 m, and a fire watch maintained for at least 30 minutes after completion (longer where specified).

Electric shock risk rises with wet conditions and high open-circuit voltage; SMAW and GTAW have high OCV, so no-load voltage reduction devices are used.

Noise from plasma cutting and grinding exceeds 85 dB(A); hearing protection and noise assessment are required.

Fume from stainless steel contains hexavalent chromium; separate extraction and respiratory protection are needed for high-alloy consumables.

Lighting for visual inspection should be at least 500 lux at the surface, with 1000 lux recommended for close inspection of critical welds.

Inspection aids: weld gauges, magnifier (typically 2x to 5x), borescope, mirror, and torch; record the aid used in the report.

Report content: project and drawing reference, WPS and welder ID, material and thickness, joint and weld type, inspection stage, findings with location, acceptance criteria, and disposition.

Defect description must be quantitative: type, location along the weld, length, depth or height, and whether surface or subsurface.

Acceptance criteria must cite the applicable standard and clause, not a general statement such as acceptable quality.

Dimensional checks include weld length, leg size, throat, cap height, undercut depth, misalignment (hi-lo), and angular distortion.

Visual inspection is performed before, during, and after welding; final visual inspection precedes and often governs NDT requests.

Records must be signed and dated by the inspector with their qualification level and certificate reference stated.