IIW IWS flashcards

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

Duty cycle

The percentage of a ten-minute period a power source can operate at a given current without overheating. A 60% rating at 300 A allows six minutes of welding and four minutes of cooling.

Spray transfer

A GMAW metal transfer mode in which fine droplets detach axially above a transition current, usually with argon-rich shielding. It gives deep penetration, low spatter, and high deposition, but is limited to flat and horizontal positions.

Carbon equivalent

A formula combining alloying elements to express hardenability and cold-cracking risk. The IIW equation is CE = C + Mn/6 + (Cu+Ni)/15 + (Cr+Mo+V)/5; values above about 0.40 usually require preheat.

Hydrogen cracking

Delayed cold cracking that requires diffusible hydrogen, a hard susceptible microstructure, and tensile restraint stress. Removing any one condition, for example by preheat or low-hydrogen consumables, prevents it.

Sensitisation

Chromium carbide precipitation at grain boundaries in austenitic stainless steel held in the 450-850 C range, depleting chromium locally. Low-carbon grades such as 304L and 316L limit this risk.

Fillet weld throat

The shortest distance from the weld root to the face, equal to 0.7 times the leg length for a 90-degree fillet. Weld capacity is calculated from throat thickness and design shear strength.

Weld symbol arrow side

On a drawing, the weld symbol placed below the reference line applies to the arrow side of the joint; the symbol above the line applies to the other side.

Essential variable

A welding parameter whose change invalidates a procedure or welder qualification. Examples include process, base metal group, filler classification, thickness range, position, and heat input range.

Heat input formula

Heat input H = k x U x I / v, where U is arc voltage, I is current, v is travel speed, and k is process efficiency, about 0.8 for SMAW and near 1.0 for SAW.

Ultrasonic testing

A volumetric NDT method using high-frequency sound to detect internal defects. It is particularly effective for planar defects such as lack of fusion, but needs a qualified operator and is harder on coarse-grained austenitic welds.

Magnetic particle testing

An NDT method that magnetises a ferromagnetic component and applies magnetic particles to reveal surface and near-surface defects. It cannot be used on austenitic stainless steel or aluminium.

Local exhaust ventilation

Extraction positioned close to the arc to capture welding fume before it enters the breathing zone. It is the primary engineering control for fume exposure, with respiratory protection as a supplement.

Arc eye

Photokeratitis caused by ultraviolet radiation from the arc, producing painful inflammation of the cornea. It is prevented by correct helmet filter shades and by screening bystanders.

Operating factor

The ratio of actual arc time to total worked time. Manual welding typically has an operating factor of 20-40%, while mechanised processes achieve higher values.

Deposition rate

The mass of filler deposited per unit time, calculated from wire cross-section area, feed speed, and density. It increases with current and wire feed speed for a given wire diameter.

Hold point

A stage in fabrication where work cannot proceed until inspection has been performed and released. It differs from a witness point, which requires notification but not necessarily attendance.

DCEN polarity

Direct current electrode negative, where the electrode is the cathode and the workpiece is the anode. It concentrates heat at the workpiece and is used for TIG welding of steel.

Shielding gas flow rate

The volume of shielding gas delivered to the torch per unit time, typically 10-15 L/min for GMAW and TIG. Too little causes porosity; too much causes turbulence and air entrainment.

Hexavalent chromium fume

A carcinogenic fume component produced when welding stainless steel. It requires enhanced local extraction, exposure monitoring, and health surveillance where exposure is significant.

Hot work permit

A formal authorisation defining the work area, fire precautions, gas test requirements, and fire watch duration. It is closed only after the area is checked for smouldering material.

Lamellar tearing

A step-like fracture in the base metal beneath a weld, caused by through-thickness strain tearing inclusions in thick restrained T-joints. It is mitigated by joint design and material testing.

Defect versus discontinuity

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

Delta ferrite

A phase retained in austenitic stainless steel weld metal, typically 5-10%, which resists solidification cracking. Excessive ferrite reduces toughness and corrosion resistance.

Reheat cracking

Cracking in the coarse-grained heat-affected zone of thick low-alloy steels during post-weld heat treatment. It is linked to residual stress and impurity segregation at grain boundaries.

Joint preparation angle

The included angle of a bevelled butt joint, which determines weld volume and access. Narrower angles reduce filler consumption but must still allow full penetration and slag removal.

Stress concentration factor

A multiplier describing how much local stress rises at a geometric change such as a weld toe. Smoother transitions lower the factor and improve fatigue performance.

Preheat verification

Checking that the joint has reached the specified preheat temperature before welding, using contact thermometers, temperature crayons, or thermocouples. The measurement is recorded.

Document control

A system ensuring only the current revision of a WPS or drawing is available on the shop floor. Superseded documents are removed to prevent use of wrong parameters.

Constant-current power source

A power source whose output current changes little with arc length, giving a drooping characteristic. It suits SMAW and TIG, where the welder controls arc length manually.

Constant-voltage power source

A power source with a nearly flat output characteristic, so current changes strongly with arc length. It gives a self-regulating arc and suits GMAW and FCAW.

Weld repair procedure

A documented method for removing a defect to sound metal, re-preparing the groove, and rewelding under the qualified procedure. Repairs are recorded and inspected to the original standard.

Fitness-for-service assessment

An engineering evaluation of whether a flaw of measured size is acceptable for the intended service, often using fracture mechanics. It can avoid unnecessary repair of acceptable defects.