IIW IWE cheat sheet

SMAW: arc between covered electrode and workpiece; electrode coating generates shielding gas and slag; deposition efficiency typically 60-70 % of electrode mass; current range set by electrode diameter (approx. 30-40 A per mm core diameter).

GMAW transfer modes: short-circuiting (low current, thin sheet), globular (intermediate), spray (current above transition, argon-rich gas), pulsed (controlled droplet detachment, positional capability). Transition current rises with wire diameter and with CO2 content of shielding gas.

SAW: high deposition (up to 10-20 kg/h), deep penetration, flux must be baked to limit hydrogen; current density high, so dilution and HAZ are large; only flat/horizontal positions; flux-to-wire ratio roughly 1:1 by mass.

TIG/GTAW: non-consumable tungsten electrode, separate filler; DCEN for steels, AC for aluminium to break the oxide; current capacity limited by electrode diameter and type (thoriated/ceriated/lanthanated); helium additions raise penetration and voltage.

FCAW: tubular wire with flux core; self-shielded types need no external gas and suit site work; rutile and basic slag systems differ in toughness and hydrogen; deposition rate exceeds SMAW by roughly 1.5-2 times.

Heat input formula: Q = k x (U x I x 60)/(1000 x v) with v in mm/min and k = 1.0 for SAW, 0.8 for GMAW/FCAW, 0.6 for TIG/SMAW; units kJ/mm. Higher heat input generally coarsens microstructure and lowers toughness.

Resistance spot welding: heat from Joule effect at the faying surface; key variables are current, electrode force, squeeze/weld/hold times; electrode tip diameter grows with number of welds, so current must be stepped up, and shunting reduces effective current.

Power source static characteristics: constant-current (drooping) for SMAW/TIG stabilises arc length change; constant-voltage (flat) for GMAW/FCAW gives self-regulating wire burn-off; duty cycle rated at 60 % or 100 % and must be derated for other duty.

Carbon equivalent (IIW): CE = C + Mn/6 + (Cr+Mo+V)/5 + (Cu+Ni)/15. CE above about 0.40-0.45 % raises cold-cracking risk for structural steels and calls for preheat or hydrogen control.

Steel strengthening and toughness: fine-grain practice (Al/N microalloying, controlled rolling) gives better HAZ toughness; normalised and TMCP grades resist grain coarsening better than as-rolled; coarse prior austenite grain in the HAZ lowers upper-shelf energy.

Austenitic stainless steel solidification modes: A, AF, FA, F; a small ferrite fraction (typically 3-10 FN) in the FA mode resists solidification cracking; fully austenitic (A) compositions are crack-sensitive and need low heat input and low restraint.

Sensitisation of austenitic stainless steel: chromium carbide precipitation at grain boundaries in roughly the 450-850 C range depletes Cr; remedies are low-carbon grades (L), stabilised grades (Ti/Nb), or solution annealing.

Aluminium: thermal conductivity about five times that of steel and oxide melting point above 2000 C; requires AC TIG or GMAW with cleaning action, high heat input, and removal of oxide and hydrogen sources to avoid porosity.

Hydrogen in steel welds: diffusible hydrogen causes cold cracking under restraint and high hardness; control by low-hydrogen consumables (H5/H10), baking of basic electrodes and fluxes, preheat, and adequate interpass temperature.

Solidification cracking susceptibility rises with wide freezing range, high sulphur/phosphorus, deep narrow weld shape (high depth-to-width ratio) and high restraint; remedies are wider bead shape, lower heat input, and manganese addition to fix sulphur.

Copper alloys: high conductivity demands preheat or high power; deoxidised grades (phosphorus, silicon) prevent porosity; brass welding needs fume extraction because of zinc oxide fume and volatility of zinc.

Weld symbol system (ISO 2553): arrow line points to the joint, reference line carries the symbol; symbol above the reference line = weld on arrow side, below = other side; dashed line indicates the other side of the joint; dimension to the left of the symbol is the leg length (a) or throat (z).

Butt weld design: full penetration requires access for backing or back gouging; partial penetration joints must be designed with the effective throat used in stress calculation; square butt limited to thin sections, otherwise edge preparation (V, U, J, K) is chosen for access and volume control.

Fillet weld capacity: design throat = 0.7 x leg length for equal-leg 90 degree fillet; effective length excludes end craters unless run-on/run-off plates are used; minimum leg sizes are set by plate thickness to avoid fast cooling and cracking.

Joint types and static strength: butt welds are preferred for fatigue and impact because of lower stress concentration; fillet welds in transverse loading have higher stress concentration at toe and root; fatigue class depends on detail category, not on weld metal strength.

Fatigue design: S-N curves with slope m = 3 between 10^4 and 10^7 cycles for steel details; fatigue strength depends on detail category, stress range, and thickness; improvement methods (toe grinding, TIG dressing, peening) raise the class but are not a substitute for good detail design.

Structural steel selection: strength grade, toughness class (Charpy at specified temperature), and delivery condition must match service temperature and thickness; thicker sections require higher toughness and preheat because of triaxial restraint and heat loss.

Buckling and distortion: welding sequence, balanced welding about the neutral axis, back-step technique and pre-setting reduce angular distortion; restraint raises residual stress and cracking risk, so design should allow movement where possible.

Pressure equipment: design by formula or by analysis per the applicable code; joint efficiency factor reduces allowable stress for radiographed versus non-radiographed joints; impact test requirements depend on material group, thickness and minimum design temperature.

Welding Procedure Specification (WPS) is supported by a Procedure Qualification Record (PQR) produced from a test weld; essential variables (process, thickness range, position, consumable classification, preheat, heat input) define the qualified envelope, and any change beyond these requires requalification.

Welder qualification: performance test on a test piece covering joint type, position, thickness and process; a qualified welder is qualified for the range and positions defined by the standard; qualification lapses after a defined period of inactivity unless renewed by evidence of continued work.

Distortion control hierarchy: minimise weld volume, use balanced or back-step sequences, preset or pre-bend, use fixturing and strongbacks, and apply post-weld correction (flame or mechanical) only within permitted limits.

Fit-up tolerances: root gap, misalignment (hi-lo) and edge preparation tolerances affect penetration and cracking; excessive misalignment raises eccentricity and reduces fatigue life; check with dedicated gauges before welding.

Consumable control: storage in dry, heated conditions, issue and return records, baking of basic electrodes and fluxes per manufacturer's instructions, and quarantine of damaged or damp consumables; holding ovens at roughly 100-150 C prevent reabsorption.

Production planning: welding position and access determine process choice; mechanised and automated systems require joint tracking, consistent fit-up and higher capital cost but give repeatability and higher duty factor.

Traceability: material certificates (EN 10204 3.1/3.2), heat numbers transferred to the product, consumable batch records and welding records linked to the WPS and welder ID allow reconstruction of any joint's history.

Repair and rework: repairs need an approved repair procedure, removal of defect to sound metal, and re-inspection to the original extent; repeated repair cycles degrade properties and may require heat treatment or replacement.

Weld thermal cycle: heating rate, peak temperature, and cooling time t8/5 govern microstructure; t8/5 from 800 to 500 C is the key parameter for steel HAZ; faster cooling gives harder, more crack-sensitive structures.

Carbon steel HAZ transformations: at fast cooling, martensite forms above a critical hardness; hardness limits (e.g. 350 HV10 for many applications) are met by preheat, heat input control, or lower-carbon steel; hardness testing is a proxy for crack susceptibility.

Stainless steel: 475 C embrittlement in ferritic grades, sigma phase formation in austenitic/duplex grades after prolonged exposure around 600-900 C, and sensitisation around 450-850 C are separate mechanisms; duplex needs balanced ferrite-austenite and controlled heat input.

Nickel alloys: solidification cracking and ductility-dip cracking are key risks; low sulphur and controlled minor elements (Nb, Ti) matter; high heat input and restraint increase cracking; cleanliness of the joint is critical.

Solidification cracking theory: the crack occurs in the terminal stage of solidification when low-melting liquid films cannot accommodate shrinkage strain; susceptibility depends on composition, weld shape, and strain, not on strength alone.

Hydrogen-assisted cold cracking: requires hydrogen, susceptible microstructure, tensile stress, and temperature near ambient; incubation time means inspection should be delayed (e.g. 24-48 h) or the joint held warm to allow hydrogen to escape.

Reheat cracking (stress-relief cracking): occurs in the coarse-grained HAZ of low-alloy steels during post-weld heat treatment; associated with carbides and impurities (P, S, Sb, Sn, As) at grain boundaries; controlled by composition and heat treatment parameters.

Lamellar tearing: occurs in thick, highly restrained T-joints where through-thickness strain acts on non-metallic inclusions; remedies are improved steel cleanliness (Z-quality), joint design to reduce through-thickness stress, and buttering.

Visual testing (VT) is performed first and covers surface discontinuities, profile, undercut, and dimensional checks; it requires adequate illumination (typically at least 500 lux at the surface) and access.

Radiographic testing (RT): detects volumetric defects (porosity, slag, lack of fusion) with film or digital detectors; sensitivity improves with smaller source size, lower energy, and shorter source-to-object distance ratio; planar defects oriented normal to the beam are missed.

Ultrasonic testing (UT): detects planar defects (cracks, lack of fusion) and gives depth information; requires coupling, probe selection (angle beam for welds), and calibration with reference blocks; orientation of the defect relative to the beam is decisive.

Magnetic particle testing (MT) applies to ferromagnetic materials only; detects surface and near-surface defects; requires magnetisation direction roughly perpendicular to the defect; contrast and lighting conditions affect detection.

Penetrant testing (PT) applies to non-porous surfaces of any material; detects surface-breaking defects; requires thorough cleaning and controlled dwell times; it cannot detect subsurface defects.

Acceptance criteria: quality levels define limits for porosity, slag, undercut and crack-like defects; cracks are generally unacceptable; acceptance levels differ for butt and fillet welds and must be stated in the specification.

Destructive testing: transverse tensile, bend, impact (Charpy), hardness, and macrosection tests verify procedure qualification; hardness traverses across the HAZ check the cooling conditions and the need for preheat.

NDE personnel qualification: certification schemes (e.g. ISO 9712) define levels 1, 2, 3 with defined training, experience and examination; level 3 is responsible for technique and procedure approval, not only for performing the test.

Welding fume: particles in the respirable range (below about 5 micrometres) reach the alveoli; exposure limits depend on the substance (manganese, chromium VI, nickel); extraction at the arc (local exhaust ventilation) is more effective than general ventilation.

Chromium VI and nickel in stainless steel fume are carcinogenic and sensitising; stainless welding requires local extraction and, where limits cannot be met, respiratory protection; hexavalent chromium fume increases with higher current and CO2 shielding.

Electric shock: no-load voltage limits for manual processes (commonly 48 V AC or 110 V DC depending on the standard and conditions); equipment earthing, insulation resistance, and dry working conditions are protective measures; the welding circuit should not be earthed at both ends.

Fire and explosion: hot work permits, removal of combustibles within a defined radius, fire watch after completion (smouldering can start after hours), and gas cylinder segregation from oxygen and fuel gases; flashback arrestors on both torch lines.

Radiation: arc radiation includes ultraviolet and infrared; eye protection with appropriate shade number depends on process and current; skin must be covered to avoid arc eye and erythema; screens protect bystanders.

Gases and asphyxiation: argon, helium and CO2 displace oxygen in confined spaces; oxygen deficiency monitoring and ventilation are needed; CO2 also creates a cold, dense hazard in pits and low areas.

Noise and physical hazards: plasma cutting and gouging exceed 85 dB(A), requiring hearing protection; hot spatter and slag demand flame-retardant clothing, gloves, and eye protection; manual handling of cylinders and heavy fabrications is a common injury source.

Environmental protection: fume filtration before discharge, proper disposal of spent flux and slag, containment of pickling and cleaning chemicals, and control of noise and light emission at site boundaries.

ISO 3834 defines quality requirements for fusion welding: part 2 (full), part 3 (standard), part 4 (elementary); it requires a responsible welding coordinator (RWC) whose competence level depends on the part and the extent of welding.

EN ISO 1090-2 for structural steelwork: execution classes EXC1 to EXC4 define the required level of NDT, welder qualification, and documentation; EXC3 and EXC4 demand higher inspection extent and more rigorous procedure qualification.

EN ISO 9606-1 welder qualification and EN ISO 15614-1 procedure qualification are the core standards for steel; qualification ranges for thickness and position are defined in the standards and must be respected in production.

Quality plan: defines the inspection and test plan (ITP) with hold points, witness points and review points; hold points require the client's or inspector's release before work proceeds and must be documented.

Nonconformity control: identify, segregate, record, and disposition (rework, repair, concession, reject); concessions need client and design approval; root-cause analysis and corrective action close the loop under ISO 9001.

Calibration and traceability of measuring and testing equipment: NDT equipment, gauges, and welding power sources need periodic verification; records must be traceable to national standards.

Documentation package: WPS, PQR, welder certificates, material certificates, consumable records, NDT reports, heat treatment charts, dimensional reports and as-built drawings form the manufacturing record book.

Accreditation and certification: ISO/IEC 17025 for testing laboratories, ISO 17020 for inspection bodies, and product certification schemes; certification of a company's welding quality system is separate from qualification of individual welders.

Technical report structure: objective, scope, standards and references, method, results (with tables and figures numbered and cited), discussion, conclusion, and recommendations; conclusions must be traceable to the presented results.

Uncertainty and measurement: report the measurement uncertainty with the result; identify type A (statistical) and type B (instrument, calibration) contributions; use consistent significant figures and units (SI).

Failure investigation: collect background and service history, inspect visually and by NDT, sample without altering the evidence, perform chemical, metallographic and mechanical tests, and correlate the fracture mode with the loading and environment.

Weld cost estimation: cost = labour + consumable + power + equipment + preparation + inspection; deposition rate and duty cycle dominate labour cost; increasing deposition rate reduces hours but may raise heat input and inspection needs.

Project planning: define scope, milestones, and interfaces; welding activities depend on design release, material delivery, procedure qualification and welder availability, so these are critical-path items; use a schedule with hold points.

Root cause analysis: use 5-why or Ishikawa to separate direct cause, contributing factors and root cause; verify the cause by reproducing or testing before implementing corrective action.

Presentation of data: use the correct chart type (trend for time series, histogram for distribution, Pareto for defect frequency, control chart for process stability); label axes with quantity and unit.

Standards hierarchy in a report: cite the exact edition and clause; distinguish normative requirements from informative guidance; where standards conflict, state which governs and why, and record any deviation with justification.