IIW IWE flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Carbon equivalent formula

CE = C + Mn/6 + (Cr+Mo+V)/5 + (Cu+Ni)/15 (IIW). Values above roughly 0.40-0.45 % in structural steels indicate higher hardenability and cold-cracking risk, requiring preheat and hydrogen control.

Heat input calculation

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. Result in kJ/mm; higher values slow cooling and coarsen microstructure.

t8/5 cooling time

Time for the weld to cool from 800 to 500 C. It controls transformation products in the HAZ of steel: short times give hard martensite, long times give softer but coarser structures.

Fillet weld throat

For an equal-leg 90 degree fillet, the design throat is 0.7 times the leg length. Stress calculations use the throat area, and the effective length excludes craters unless run-off plates are used.

Diffusible hydrogen

Hydrogen that can move within the steel at ambient temperature and cause cold cracking. Controlled by low-hydrogen consumables, baking, preheat and interpass temperature, and delayed inspection.

Sensitisation of austenitic steel

Chromium carbide precipitation at grain boundaries in roughly 450-850 C, depleting chromium locally and reducing corrosion resistance. Avoided by low-carbon or stabilised grades and by solution annealing.

Sigma phase

A brittle intermetallic phase forming in austenitic and duplex stainless steels after prolonged exposure around 600-900 C. It reduces toughness and corrosion resistance and must be avoided in service.

Lamellar tearing

Step-like cracking beneath a weld in thick restrained joints, caused by through-thickness strain acting on non-metallic inclusions. Controlled by cleaner steel (Z-quality), better joint design and buttering.

Reheat cracking

Cracking in the coarse-grained HAZ of low-alloy steels during post-weld heat treatment, linked to impurity segregation and carbide precipitation at grain boundaries. Controlled by composition and heat treatment parameters.

Solidification cracking

Cracking during the terminal stage of solidification when low-melting liquid films cannot accommodate shrinkage strain. Influenced by composition, weld depth-to-width ratio and restraint, not by weld strength.

WPS and PQR

The Welding Procedure Specification states the production variables; the Procedure Qualification Record documents the test weld that proved them. Essential variables define the qualified range.

Essential variables

Parameters such as process, thickness range, position, consumable classification, preheat and heat input that define the validity of a qualified procedure. Changes beyond the permitted range require requalification.

Execution classes EXC

EN ISO 1090-2 classes EXC1 to EXC4 for structural steelwork. Higher classes demand more extensive NDT, stricter welder and procedure qualification, and more documentation.

ISO 3834 parts

Quality requirements for fusion welding: part 2 full, part 3 standard, part 4 elementary. Each requires a responsible welding coordinator with competence matched to the part and scope.

Hold point

A stage in the inspection and test plan where work cannot proceed until the designated party has witnessed and released it. It must be recorded in the quality documentation.

Weld symbol arrow side

In ISO 2553, a symbol above the reference line means the weld is on the arrow side; below the line means the other side. A dashed line marks the other side of the joint.

Fatigue detail category

A number giving the stress range at two million cycles for a welded detail. Fatigue life depends on detail geometry, stress range and thickness, not on the static strength of the weld metal.

Radiographic sensitivity

Ability to detect small defects, improved by a small source, low energy and adequate source-to-object distance. Planar defects normal to the beam are poorly detected.

Ultrasonic angle beam testing

Technique using an angled probe to direct sound into the weld at an angle. It detects planar defects such as lack of fusion and cracks and provides depth information.

Magnetic particle testing scope

Applies only to ferromagnetic materials and detects surface and near-surface defects. The magnetising direction should be roughly perpendicular to the expected defect orientation.

Penetrant testing limitation

Detects only surface-breaking defects on non-porous materials. It cannot find subsurface discontinuities and requires thorough cleaning and controlled dwell times.

NDT personnel levels

ISO 9712 defines levels 1, 2 and 3 with specified training, experience and examination. Level 3 approves procedures and techniques and is not limited to performing tests.

GMAW spray transfer

Metal transfer with fine droplets and a stable arc, occurring above a transition current that rises with wire diameter and CO2 content. It gives high deposition but is limited to flat and horizontal positions.

TIG electrode polarity

DCEN concentrates heat at the workpiece and suits steels; AC alternates to break aluminium oxide and provides cleaning action. Electrode current capacity depends on diameter and alloying type.

Self-shielded FCAW

Flux-cored wire that generates its own shielding without external gas, making it suitable for site and windy conditions. Deposition rate is higher than SMAW but toughness depends on the flux system.

Submerged arc flux handling

Flux must be dry and baked to limit hydrogen. The arc is buried under a flux layer, giving high deposition and deep penetration but restricting use to flat and horizontal positions.

Aluminium welding oxide problem

Aluminium oxide melts above 2000 C, far above the metal, so it must be removed mechanically or chemically and broken up by AC TIG cleaning action. Hydrogen porosity is the main defect risk.

Preheat purpose

Slows cooling, lowers HAZ hardness and allows hydrogen to escape, reducing cold-cracking risk in restrained thick joints. It also improves fusion in high-conductivity materials such as copper.

Welding fume extraction

Local exhaust ventilation at the arc captures fume before it enters the breathing zone. It is more effective than general ventilation, especially for stainless steel fume containing chromium VI and nickel.

Confined space oxygen displacement

Argon, helium and CO2 used as shielding gases displace oxygen in confined spaces. Oxygen monitoring and ventilation are required before entry and during welding.

Flashback arrestor

A device on oxy-fuel torch and regulator lines that stops a flame from travelling back into the hose or cylinder. It is a key fire and explosion protection measure.

Technical report conclusion

A statement traceable to the presented results, distinguishing observation from interpretation and stating limitations. Recommendations follow from the conclusion and cite the governing standard clauses.