IIW IWI-S cheat sheet

SMAW: electrode coating generates shielding gas and slag; rutile electrodes give smooth arc and easy restrike, basic (low-hydrogen) coatings require baking at 300-350 °C and holding at 100-150 °C.

GMAW transfer modes: short-circuiting (low current, thin plate), globular (high current, spatter-prone), spray (above transition current, argon-rich gas, deep penetration), pulsed (spray at low mean current).

GTAW uses a non-consumable tungsten electrode; DCEN gives deeper penetration for steels, AC is used for aluminium to break the oxide; argon or helium shielding, helium for higher heat input.

SAW uses granular flux; typical current 400-1200 A, high deposition rate, only flat or horizontal positions; flux must be baked to avoid hydrogen pickup.

FCAW: self-shielded wires rely on the core for gas and are wind-tolerant; gas-shielded wires need CO2 or Ar/CO2 and give better toughness.

Heat input formula: Q (kJ/mm) = k × U × I × 60 / (1000 × v), where v is travel speed in mm/min and k is efficiency (0.8 for SMAW/GMAW, ~1.0 for SAW).

Duty cycle: at 60 % duty cycle a 300 A machine can run 300 A for 6 minutes per 10-minute period; higher currents reduce permissible duty cycle.

Electroslag and electrogas welding are high-deposition vertical processes using a molten slag bath or gas shield with water-cooled shoes; coarse grain and high heat input result.

Carbon equivalent (IIW): CE = C + Mn/6 + (Cr+Mo+V)/5 + (Cu+Ni)/15; CE > 0.40 % indicates increased hardenability and need for preheat or low-hydrogen practice.

Hydrogen cracking occurs in the HAZ when hydrogen, susceptible microstructure, restraint and stress combine; remedies are preheat, low-hydrogen consumables, post-heat and limiting heat input.

Austenitic stainless steels solidify as ferrite-austenite (FA) or austenite-ferrite (AF) modes; 5-10 % delta ferrite resists solidification cracking, but ferrite can transform to sigma phase above ~550 °C.

Sensitisation of austenitic stainless steel: chromium carbides precipitate at grain boundaries in the 450-850 °C range, depleting Cr and reducing corrosion resistance; low-carbon (L) grades or stabilised grades (Ti, Nb) prevent it.

Aluminium: oxide melts at ~2050 °C, well above the 660 °C melting point of the metal; AC GTAW or reverse-polarity cleaning breaks the oxide; thermal conductivity is high, so preheat and higher currents are needed.

Steel HAZ hardness depends on cooling rate: faster cooling (thicker plate, lower heat input) gives harder martensite; t8/5 cooling time is a common measure of the thermal cycle.

Solidification cracking is favoured by high sulphur and phosphorus, deep narrow weld pools and high restraint; Mn/S ratio above ~20 reduces the risk in carbon steels.

Duplex stainless steels need a balanced ferrite-austenite microstructure; excessive heat input or slow cooling promotes sigma and nitride formation, reducing toughness and corrosion resistance.

Weld joint types: butt, T-joint, corner, lap and edge; butt welds are preferred for fatigue-loaded joints because load is transferred without eccentricity.

Weld symbol per ISO 2553: arrow line points to the joint, reference line carries the symbol; the symbol above the reference line denotes the arrow side, below denotes the other side.

Fatigue design: butt welds with full penetration and smooth profile give the highest fatigue class; fillet welds and transverse attachments reduce fatigue strength due to stress concentration.

Throat thickness of a fillet weld: a = 0.707 × leg length for a 90° joint with equal legs; design throat is used for strength calculation.

Weld size and length are specified on drawings; intermittent fillet welds are defined by length and pitch, and must not be used in corrosive or fatigue-critical applications.

Shrinkage and distortion: longitudinal shrinkage shortens the member, transverse shrinkage causes angular distortion; balanced welding sequences and back-step welding reduce distortion.

Restraint increases residual stress and cracking risk; preheating and stress-relief heat treatment (typically 550-650 °C for carbon steels) reduce residual stress.

Design for inspection: joint access must allow visual and NDT coverage; single-sided butt welds without backing require root inspection and may need a backing bar or ceramic backing.

WPS (welding procedure specification) is supported by a PQR (procedure qualification record); the WPS must be requalified when essential variables (e.g. material group, filler classification, thickness range, preheat) change beyond limits.

Preheat temperature is measured at least 100 mm from the joint on the thicker part, before welding; interpass temperature must not exceed the maximum specified for the material.

Joint preparation: bevel angles typically 30-37.5° per side for V-groove; root gap and root face control penetration and burn-through.

Tack welds are part of the finished weld and must be made with qualified procedures and consumables, and be inspected; they must be free of cracks and slag.

Distortion control methods: back-step welding, balanced sequence, pre-setting, jigs and fixtures, and controlled heat input; flame straightening is used after welding.

Consumable control: electrodes must be stored dry, low-hydrogen electrodes in heated quivers; re-drying cycles and holding times must be recorded.

Orbital and mechanised welding require parameter monitoring (current, voltage, travel speed, wire feed); deviations from the WPS must be recorded and assessed.

Cladding and hardfacing: dilution must be controlled; buffer layers reduce cracking between dissimilar materials, and preheat/post-heat follow the base material requirement.

Visual testing (VT) is the first NDT method; it detects surface discontinuities, undercut, overlap, spatter and dimensional deviations; requires adequate illumination (typically ≥ 500 lux) and access.

Penetrant testing (PT) detects surface-breaking defects in non-porous materials; excess penetrant is removed, developer draws penetrant out; dwell and development times follow the standard.

Magnetic particle testing (MT) detects surface and near-surface defects in ferromagnetic materials; AC gives surface sensitivity, DC gives subsurface detection; demagnetisation is required after testing.

Ultrasonic testing (UT) detects internal planar defects; probe frequency, angle and calibration blocks (e.g. V1, V2) are used; lack of fusion and cracks are better detected than porosity.

Radiographic testing (RT) detects volumetric defects; image quality is assessed with IQIs (wire or step-hole); planar defects oriented parallel to the beam may be missed.

Destructive tests: tensile, bend, impact (Charpy), hardness and macro/micro examination; bend tests assess ductility and root fusion; impact tests are performed at specified temperatures.

Acceptance criteria are defined by the applicable standard (e.g. ISO 5817 quality levels B, C, D); level B is the most stringent and applies to fatigue or critical joints.

NDT personnel qualification: ISO 9712 levels 1, 2 and 3; level 2 can set up and interpret tests per procedure, level 3 can develop procedures and approve techniques.

Quality assurance (QA) is process-oriented and preventive; quality control (QC) is product-oriented and detects nonconformities after the fact.

ISO 9001 is the generic quality management system standard; ISO 3834 specifies quality requirements for fusion welding of metallic materials, with parts 2-4 covering different levels.

Welding coordination per ISO 14731: the manufacturer must appoint a responsible welding coordinator (RWC) with adequate technical knowledge; the level of responsibility depends on the product.

Essential variables in a WPS: base material group, thickness range, filler metal, welding process, position, preheat and post-weld heat treatment; changes beyond qualification limits require requalification.

Nonconformance reports (NCR) record the deviation, disposition (rework, repair, concession, scrap) and corrective action; traceability of repairs must be maintained.

Documentation package: WPS, PQR, welder qualification certificates, material certificates (EN 10204 3.1), NDT reports, heat treatment records and dimensional reports.

Calibration of measuring and testing equipment must be traceable to national standards; certificates must be valid at the time of inspection.

Audit types: internal (first party), customer (second party) and certification body (third party); findings are classified as major or minor nonconformities with defined close-out times.

Welding fume contains metal oxides and gases; manganese and hexavalent chromium (from stainless steel) are health hazards; local exhaust ventilation (LEV) must be used at the arc.

Arc eye (photokeratitis) is caused by UV radiation; welding helmets with appropriate shade (e.g. shade 10-13 for high-current arc welding) and protective filters are required.

Electric shock risk: open-circuit voltage limits (e.g. ≤ 48 V AC in wet or confined conditions), earth clamps, dry gloves and insulated electrode holders; never work alone in confined spaces.

Fire and explosion: hot work permits, fire watch, removal of combustibles within 10 m, and gas cylinder segregation (oxygen and fuel gas separated, cylinders secured upright).

Compressed gas cylinders: acetylene must never be used above 1.5 bar gauge; flashback arrestors are required on both torch and regulator sides.

Confined space entry requires gas testing (oxygen 19.5-23.5 %), ventilation, a standby person and rescue plan; welding in confined spaces increases fume and shock risk.

Noise, radiation and heat: arc welding produces UV and IR radiation; nearby workers need screens; noise from grinding and plasma cutting requires hearing protection.

Environmental: fume extraction and filtration, correct disposal of spent flux, slag, coated electrodes and contaminated consumables; compliance with local emission limits.

Inspection plan: define scope, standards, acceptance criteria, NDT methods, extent and stage (before, during, after welding); hold points require inspector sign-off before work continues.

Before welding: verify WPS, welder qualification, material certificates, consumable condition, joint preparation and fit-up dimensions.

During welding: monitor preheat/interpass temperature, current, voltage, travel speed, root condition, cleaning between passes and distortion.

After welding: visual inspection, dimensional check, NDT per plan, post-weld heat treatment records and final documentation review.

Inspection report contents: project and component identification, drawing and WPS references, inspection date, method and standard, findings, acceptance status, inspector name and signature.

Discontinuity vs defect: a discontinuity is any interruption in the weld; it becomes a defect only when it exceeds the acceptance criteria of the applicable standard.

Typical weld discontinuities: porosity, slag inclusion, lack of fusion, lack of penetration, undercut, overlap, cracks (longitudinal, transverse, crater, HAZ), spatter and arc strikes.

Traceability: weld identification numbers on drawings and on the component, repair records linked to original weld numbers, and retention times for records per contract or standard.