IIW IWP flashcards

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

SMAW electrode polarity

DCEP (electrode positive) concentrates heat at the work for deeper penetration; DCEN concentrates heat at the electrode for higher deposition and shallower penetration; AC alternates and suits some basic electrodes.

GMAW spray transfer

Occurs above a transition current in argon-rich shielding gas; produces fine droplets, deep penetration, and low spatter; limited to flat and horizontal positions because the large weld pool is difficult to control.

Duty cycle formula

For a power source rated at 60% duty cycle, the allowable current at 100% duty is the rated current multiplied by the square root of 0.6, approximately 0.775 times the rated current.

Carbon equivalent IIW

CE = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15; values above about 0.45 indicate increased hardenability and cold-cracking risk, requiring preheat and low-hydrogen consumables.

Heat input formula

H = k × V × I × 60 / (1000 × v) in kJ/mm, where V is volts, I is amps, v is travel speed in mm/min, and k is thermal efficiency (SMAW 0.8, SAW 1.0, GTAW 0.6).

Sensitisation of stainless steel

Chromium carbide precipitation at grain boundaries when austenitic stainless steel is held at 450–850 °C, depleting chromium and reducing corrosion resistance; use L or stabilised grades.

Hydrogen-assisted cold cracking

Requires susceptible martensitic microstructure, diffusible hydrogen, and tensile stress; prevented by preheat, low-hydrogen consumables, and post-weld heat treatment or tempering.

Fillet weld throat

For an equal-leg 45° fillet weld, the design throat thickness equals 0.707 times the leg length; the throat governs shear capacity in structural design.

Weld symbol arrow side

On a drawing, a weld symbol placed above the reference line indicates the weld is on the arrow side of the joint; below the line indicates the other side.

Fatigue detail category

A classification of welded details by stress range versus cycles to failure; the weld toe is the critical location, and improvement techniques such as grinding or TIG dressing raise the category.

Weldability definition

The capacity of a material to be welded under fabrication conditions into a specific, suitably designed structure that performs satisfactorily in service.

Duplex stainless heat input

Typically controlled between 0.5 and 2.5 kJ/mm with interpass temperature at or below 150 °C to maintain the ferrite-austenite balance and avoid sigma phase formation.

Aluminium oxide melting point

Aluminium oxide (Al2O3) melts at about 2072 °C, far above aluminium at about 660 °C; AC GTAW or GMAW with argon provides cathodic cleaning to break up the oxide film.

Magnetic particle testing limitation

MT detects surface and near-surface discontinuities only in ferromagnetic materials; it is not applicable to austenitic stainless steel, aluminium, or copper alloys.

Radiographic image quality indicator

An IQI, such as a wire or step-hole type, placed on the test object verifies the sensitivity of a radiograph; the required IQI value depends on technique and material thickness.

ISO 5817 quality levels

Defines three quality levels for steel welds: B (stringent), C (intermediate), and D (moderate); acceptance depends on defect type, size, and location.

Welder qualification standard

ISO 9606 series covers welder performance qualification; the test piece and ranges (material group, thickness, position, process) define the scope of the certificate.

Welding fume control

Local exhaust ventilation at the arc, general ventilation, and respiratory protection where exposure limits are exceeded; fume contains metal oxides, ozone, nitrogen oxides, and carbon monoxide.

Acetylene cylinder pressure limit

Acetylene cylinders must be used upright and never above 1.5 bar gauge; flashback arrestors are fitted on torches and regulators, and oil or grease must be kept away from oxygen fittings.

Arc eye cause

Photokeratitis caused by ultraviolet radiation from the arc; prevented by a welding helmet with the correct shade number for the process and current, and by protecting bystanders with screens.

SMAW drag angle

For flat butt welding, a drag angle of about 5–15° is typical; incorrect travel or work angles can cause lack of fusion, uneven legs, or undercut.

Weave width limit

For SMAW, weave width should not exceed about three times the electrode diameter to avoid slag entrapment and wide, shallow beads; stringer beads are preferred for vertical-up.

SMAW restart technique

Strike the arc ahead of the crater and back into it to avoid porosity and slag inclusions at the restart point; this fuses the crater properly.

Back purge for pipe root

Argon purge on the inside of the pipe prevents oxidation of the root pass in stainless and reactive metals; maintain consistent root gap and land for a sound keyhole.

ISO 14731 welding coordination

Defines welding coordination tasks such as review of requirements, procedure selection, qualification, and inspection planning, and competence levels: basic, specific, and comprehensive.

Electrode storage and baking

Low-hydrogen electrodes must be stored dry and baked or held at manufacturer-specified temperatures; issue only what is needed and record batch numbers for traceability.

WPS and PQR

The welding procedure specification (WPS) is the qualified instruction; the procedure qualification record (PQR) documents the test results that support the WPS.

Distortion control by balancing

Balance welding about the neutral axis, use back-step or skip sequence, preset parts against shrinkage, and use minimum necessary heat input to reduce distortion.

SAW flux handling

Submerged-arc flux must be dry and baked to avoid hydrogen pickup; it is buried over the arc, giving high deposition and deep penetration, typically in flat or horizontal positions.

FCAW self-shielded vs gas-shielded

Self-shielded FCAW (136) needs no external gas and suits field work; gas-shielded FCAW (138) uses CO2 or mixed gas and gives better toughness and appearance.

Penetrant testing suitability

PT detects surface-breaking discontinuities in non-porous materials; it is not suitable for porous or rough surfaces, and requires cleaning, penetrant, developer, and adequate inspection light.

Preheat purpose

Preheat slows cooling to avoid martensite formation and allows hydrogen to escape, reducing cold-cracking risk; it also helps on high-conductivity materials such as aluminium.