IIW IWT flashcards

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

Heat input formula

Heat input Q equals k times voltage times current divided by travel speed, with k the process thermal efficiency. It is expressed in kJ/mm and controls cooling rate, HAZ hardness and toughness.

Spray transfer transition current

Above a threshold current, metal transfers as fine droplets in an argon-rich gas. The threshold rises with wire diameter and falls with higher argon content and longer arc.

Constant-voltage characteristic

A flat or slightly drooping power source output used for GMAW and SAW. Wire burn-off self-regulates arc length, so small voltage changes cause large current changes.

Carbon equivalent

CE equals C plus Mn/6 plus (Cr+Mo+V)/5 plus (Ni+Cu)/15. Higher values mean greater hardenability and cold-cracking risk, requiring preheat or low-hydrogen consumables.

Sensitisation of austenitic stainless

Chromium carbide precipitation at grain boundaries in the 450-850 C range depletes chromium locally and reduces corrosion resistance. Low-carbon or stabilised grades resist this effect.

Hydrogen cold cracking

Delayed cracking in ferritic steels caused by hydrogen, a hard microstructure and tensile stress. Prevention uses preheat, low-hydrogen consumables, dry electrodes and controlled cooling.

Fillet weld throat

For an equal-leg fillet, throat thickness equals 0.7 times the leg length. Design resistance is calculated on the throat area using the directional or simplified method.

Fatigue detail category

A FAT class in IIW recommendations or Eurocode 3 giving the stress range for a given number of cycles. Weld toe geometry and detail type govern it, not static steel strength.

Lamellar tearing

Step-like cracking in thick plate under through-thickness strain, linked to non-metallic inclusions. Z-quality plate, joint redesign and buttering reduce the risk.

WPS and WPQR relationship

The WPS instructs the welder; the WPQR records the test results that qualified it. Exceeding essential variable limits requires requalification before the WPS can be revised.

ISO 3834 levels

Quality requirements for fusion welding in three levels: comprehensive (part 2), standard (part 3) and elementary (part 4). The level depends on product risk and contract requirements.

Arc time ratio

Arc-on time divided by total working time. Manual welding typically reaches 20-40 percent, mechanised welding 60-80 percent, so reducing non-arc time cuts unit cost.

Cooling time t8/5

Time taken to cool from 800 to 500 C after welding. It controls ferrite, bainite and martensite formation and therefore HAZ hardness and toughness in C-Mn steels.

Post-weld heat treatment

Holding the component at about 550-650 C for a time based on thickness, with controlled heating and cooling. It relieves residual stress and tempers hard HAZ microstructures.

Delta ferrite in austenitic welds

A small ferrite fraction, typically 5-10 FN, in austenitic weld metal. It reduces solidification cracking and is predicted from chromium and nickel equivalents.

Schaeffler diagram

A constitution diagram predicting ferrite, martensite and austenite in stainless steel weld metal from chromium and nickel equivalents. It guides filler selection for dissimilar joints.

Radiographic image quality indicator

A wire or step-hole device placed on the test piece to verify sensitivity. It confirms that the technique can reveal a defect of the specified size.

Ultrasonic testing of planar defects

UT detects cracks and lack of fusion, which are planar and orientation-dependent. Detection needs the beam roughly perpendicular to the defect plane.

ISO 5817 quality levels

Acceptance levels B, C and D for steel welds, where B is the most stringent. ISO 10042 provides equivalent levels for aluminium welds.

Magnetic particle testing limits

MT applies only to ferromagnetic materials and detects surface and near-surface defects. The magnetic field must be roughly perpendicular to the defect direction.

Arc eye

Photokeratitis caused by ultraviolet radiation from the arc. It produces painful inflammation of the cornea and is prevented by a suitable welding helmet shade.

Flashback arrestor

A device fitted to the torch and regulator that stops a flame from travelling back into the gas supply. It is required on both fuel gas and oxygen lines.

Welding fume extraction

Local exhaust ventilation captures fume at the arc before it reaches the breathing zone. It is essential for stainless and confined-space welding and for chromium and nickel exposure.

Deposition rate

Mass of filler deposited per unit time, calculated from wire cross-section, wire feed speed and density. It sets productivity and is reduced by spatter and stub losses.

Consumable cost per metre

Deposition per metre times price per kg divided by deposition efficiency. Efficiency falls with stub loss and spatter, so basic electrodes cost more per deposited kg.

Takt time

Available production time divided by customer demand. It sets the required output rate and identifies welding as a bottleneck when the weld time exceeds it.

SMAW electrode drag angle

For downhand welding, the electrode is tilted about 10-15 degrees in the direction of travel (backhand). The work angle is about 45 degrees to the joint faces.

Interpass temperature

The temperature of the weld and adjacent metal before the next pass. It must be measured and kept below the maximum to preserve toughness and corrosion resistance.

Weave width limit

For manual metal arc welding, the weave should not exceed about three times the electrode diameter. Wider weaving reduces penetration and can trap slag.

Friction stir welding

A solid-state process using a rotating tool to stir and join metal below the melting point. It suits aluminium and avoids fusion defects but leaves an exit hole.

Narrow-gap welding

Welding a narrow, deep groove in thick sections with a weaving or rotating arc. It lowers heat input and distortion but demands precise joint tracking and gap control.

Wire arc additive manufacturing

Layer-by-layer deposition using an arc process such as GMAW or TIG. Residual stress and anisotropic properties are key issues, and post-build heat treatment is common.