IIW IWI-C flashcards
IIW IWI-C · Build recall with a focused review session.
36 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Heat input formula
- Heat input in kJ/mm equals k times voltage times current times 60 divided by 1000 times travel speed in mm/min. k is 1.0 for DC and lower for AC.
- Spray transfer condition
- Metal transfers as fine droplets in a spray when current exceeds the transition value in argon-rich gas. It gives deep penetration and is used for thicker sections in flat positions.
- GTAW electrode polarity
- Direct current electrode negative concentrates heat at the workpiece and is used for steel. Alternating current is used for aluminium because the positive half-cycle breaks the oxide layer.
- Submerged arc flux handling
- Flux must be dry and baked before use. Moisture in flux introduces hydrogen into the weld and causes porosity and hydrogen cracking in thick sections.
- Constant voltage characteristic
- A flat output characteristic keeps arc length nearly constant as the welder varies stick-out. This self-regulating behaviour suits GMAW and FCAW with wire feed.
- Carbon equivalent IIW
- CE equals C plus Mn/6 plus (Cr+Mo+V)/5 plus (Ni+Cu)/15. Values above about 0.40 to 0.45 percent indicate need for preheat and low-hydrogen consumables.
- Hydrogen cracking triad
- Hydrogen cracking needs susceptible martensitic microstructure, diffusible hydrogen above a critical level, and tensile restraint stress. Removing any one factor prevents cracking.
- Sensitisation of austenitic steel
- Holding austenitic stainless steel in the 450 to 850 Celsius range precipitates chromium carbides at grain boundaries and depletes chromium, causing intergranular corrosion. Low-carbon or stabilised grades resist this.
- Aluminium oxide problem
- Aluminium forms a tenacious oxide melting near 2050 Celsius, far above the metal. AC GTAW or mechanical and chemical cleaning must remove it before welding.
- Duplex sigma phase
- Slow cooling of duplex stainless steel through 600 to 900 Celsius forms brittle sigma phase and reduces toughness and corrosion resistance. Control heat input and interpass temperature.
- Fillet weld throat
- For an equal-leg fillet weld the throat thickness equals 0.707 times the leg length. Design strength is throat area multiplied by allowable stress.
- Fatigue detail category
- The detail category, or FAT class, sets the stress range giving 2 million cycles on the S-N curve. It depends on weld geometry, toe radius, load direction and inspection level.
- Lamellar tearing cause
- Through-thickness stress in thick plate acts on elongated inclusion stringers, causing step-like tearing. Z-quality plate and reduced restraint or changed joint design prevent it.
- ISO 2553 weld symbol sides
- A solid reference line denotes the arrow side and a dashed line the other side. Symbols above the line apply to the side indicated by the line style.
- Planar versus volumetric defects
- Planar defects such as cracks and lack of fusion concentrate stress and are more damaging under fatigue than rounded volumetric defects such as porosity of similar size.
- WPQR purpose
- The welding procedure qualification record documents the tested variables and results that prove a procedure produces sound welds. The WPS is written within its qualified range.
- Essential variable examples
- Changes in base metal group, filler classification, shielding gas composition beyond permitted limits, current type, or heat input range usually require requalification of the procedure.
- Welder qualification scope
- ISO 9606-1 qualification is specific to process, position, joint type and consumable group. It covers defined thickness and pipe diameter ranges and is valid for a limited period.
- Interpass temperature control
- Maximum interpass temperature limits heat build-up between passes. It is critical for duplex and stainless steels and is checked with contact thermometers before each pass.
- Distortion reduction methods
- Balanced welding sequence, back-step technique, pre-setting, minimum number of passes and controlled heat input reduce distortion. Stress relief may follow for thick or restrained joints.
- QA versus QC
- Quality assurance is process-based, covering procedures, audits and documentation. Quality control is product-based, covering inspection and testing of the actual weld.
- Hardness acceptance limit
- A common acceptance criterion for carbon and carbon-manganese steel welds is 350 HV10 maximum in the heat-affected zone. Higher limits apply to some stainless grades.
- Hold and witness points
- In an inspection and test plan, a hold point stops work until the inspector witnesses it. A witness point requires notification but work may proceed without attendance.
- Procedure qualification tests
- Qualification testing typically includes tensile, root and face bend, Charpy impact, hardness survey and macro examination, with results compared against the applicable standard.
- Magnetic particle limitations
- Magnetic particle testing applies only to ferromagnetic materials. It finds surface and near-surface defects best when the defect lies roughly perpendicular to the magnetic field lines.
- Ultrasonic defect sizing
- Planar defects are sized by the 6 dB drop or 20 dB drop technique, or by time-of-flight diffraction. Calibration uses reference blocks and a distance-amplitude curve.
- Radiographic sensitivity check
- An image quality indicator, either wire or step-hole type, is placed on the workpiece. Its visibility on the radiograph confirms the required sensitivity was achieved.
- ISO 5817 quality levels
- ISO 5817 defines weld quality levels B, C and D, where B is the most stringent. Acceptance levels for ultrasonic and radiographic testing are set separately in ISO 11666 and ISO 10675.
- Penetrant testing light requirement
- Fluorescent penetrant inspection requires ultraviolet-A light near 365 nanometres in a darkened area. Colour contrast penetrant needs adequate white light of at least 500 lux.
- Arc eye prevention
- Ultraviolet radiation from the arc causes photokeratitis. Filter shade number must match process and current, for example shade 10 to 13 for manual metal arc at 100 to 300 amperes.
- Confined space gas limits
- Entry requires oxygen between about 19.5 and 23.5 percent, and flammable and toxic gas below permitted limits. A permit, standby person and rescue equipment are required.
- ISO 3834 parts
- ISO 3834 specifies welding quality requirements. Part 2 is full, part 3 standard and part 4 elementary. The level chosen depends on product criticality and contract requirements.
- EN 1090-2 execution classes
- Execution classes EXC1 to EXC4 for steel structures set escalating requirements for welder qualification, procedure qualification, non-destructive testing extent and documentation.
- Material certificate types
- EN 10204 type 3.1 gives inspection results from the manufacturer's own inspection. Type 3.2 gives results from inspection independent of the manufacturer.
- Third-party inspector role
- An independent inspection authority verifies compliance with specification and standards. It does not supervise or instruct the fabricator's workforce and does not transfer responsibility from the contractor.
- Contractor versus client liability
- The contractor is normally responsible for workmanship and specification compliance. The client bears design responsibility unless design has been delegated by contract.