Canada BWR cheat sheet

SMAW polarity: DCEN (straight) concentrates heat at the work for deep penetration; DCEP (reverse) concentrates heat at the electrode for shallower penetration and better arc stability.

GMAW transfer modes: short-circuit (low current, thin gauge), globular (high current, spatter-prone), spray (above transition current, high deposition, flat/ horizontal only), and pulsed spray (spray-like at lower average current, all positions).

GTAW uses constant-current (drooping) power; electrode negative for DCEN to avoid tungsten contamination; AC for aluminum to break the oxide with the positive half-cycle.

Heat input formula: HI (kJ/mm) = (V × I × 60) / (1000 × travel speed in mm/min); increasing travel speed or decreasing current/voltage lowers heat input.

FCAW gas-shielded uses a tubular electrode with flux core; self-shielded FCAW relies on flux for shielding and is more wind-tolerant; both have higher deposition than SMAW.

Preheat temperature is a variable that must be maintained; it reduces cooling rate and hydrogen cracking risk; interpass temperature must not exceed the WPS maximum to avoid loss of toughness.

SAW uses granular flux and high currents; it is limited to flat and horizontal positions; flux must be dry to prevent hydrogen and porosity.

Root pass in pipe welding often uses a lower heat input and a different process (e.g., GTAW) to control penetration and avoid burn-through.

Arc blow in DC welding is mitigated by using AC, reducing current, changing ground location, or using shorter arcs.

A WPS must be supported by a PQR (procedure qualification record) that documents the essential variables and test results; the PQR is a record, not a procedure.

Essential variables (e.g., process, base metal group, filler classification, preheat, PWHT) cannot be changed without requalification; nonessential variables (e.g., travel speed range, nozzle size) may be changed within limits.

ASME Section IX base metal P-numbers group similar materials; a PQR qualifies the P-number and may qualify other P-numbers per the rules (e.g., P-1 to P-1).

Filler metal F-numbers group electrodes; an F-number qualification covers other F-numbers within the same group, but not higher groups unless specifically permitted.

Procedure qualification test coupons must be tested per the applicable code: tensile, bend, and impact (when required); failure of any specimen requires investigation and possible requalification.

PWHT is an essential variable: adding or changing PWHT requires requalification; the PQR must record the PWHT temperature and time.

For ASME IX, a change from one process to another requires a new PQR; multiple processes may be combined in one WPS with separate PQRs.

The WPS must be available to the welder and inspector; it must specify ranges for current, voltage, travel speed, and number of passes.

Welder performance qualification (WPQ) tests the welder's ability; it is separate from procedure qualification and is specific to the process and position.

Essential variables for WPQ include process, position, backing, and filler metal; a change in process or position may require requalification.

A welder qualified on a test coupon with backing is not qualified for welding without backing unless specifically tested for root pass without backing.

Qualification positions are designated by numbers (e.g., 1G, 2G, 3G, 4G for plate; 5G, 6G for pipe); a higher position may qualify lower positions per code rules.

WPQ tests typically include visual inspection and bend tests (or radiography) per code; failure requires retraining and retesting.

Continuity: welders must maintain qualification by welding with the process within a specified period (e.g., 6 months) or requalify.

A welder qualified for GTAW on pipe may not be qualified for GMAW; each process requires separate qualification.

Test coupons for welder qualification must be prepared and welded under the same essential variables as production, except for position and thickness ranges per code.

Carbon steel filler metal classification: E60XX and E70XX designate minimum tensile strength (60 ksi, 70 ksi); the last two digits indicate position and coating/current type.

Stainless steel filler metals: ER308L for 304/304L base metal; ER316L for 316/316L; low-carbon 'L' grades resist sensitization.

Aluminum filler selection: ER4043 (5% Si) for general purpose and crack resistance; ER5356 (5% Mg) for higher strength and anodizing color match.

Matching base metal strength is not always required; for some applications, undermatching filler (e.g., ER308L on 304) is acceptable to improve ductility.

Hydrogen content in filler metal affects cracking; low-hydrogen electrodes (E7018) require dry storage and are designated by the 'H' number (e.g., H4 = 4 mL/100 g).

Dissimilar metal joints require careful filler selection to avoid brittle phases; nickel-based fillers (e.g., ERNiCr-3) are common for steel-to-stainless.

Filler metal must be stored per manufacturer recommendations; moisture pickup can cause porosity and hydrogen cracking.

Base metal chemistry affects weldability: higher carbon equivalent increases hardenability and cracking risk; preheat and low-hydrogen practice mitigate.

Heat-affected zone (HAZ) experiences thermal cycles that can cause grain growth, hardening, or softening; properties depend on cooling rate and composition.

Hydrogen-induced cracking occurs when hydrogen, susceptible microstructure, and tensile stress combine; control by low-hydrogen consumables, preheat, and post-weld heat treatment.

Carbon equivalent (CE) formulas (e.g., IIW: CE = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15) estimate weldability; CE > 0.4 may require preheat.

Tensile test measures ultimate strength and yield; bend test evaluates ductility and soundness of the weld and HAZ.

Charpy V-notch impact test measures toughness at a specified temperature; absorbed energy and lateral expansion are recorded.

Radiographic testing (RT) detects volumetric defects (porosity, slag, incomplete penetration); ultrasonic testing (UT) detects planar defects (cracks, lack of fusion).

Macroetch examination reveals weld profile, penetration, and HAZ; it is often used for procedure qualification.

Sensitization in austenitic stainless steel occurs when chromium carbides precipitate at grain boundaries (450–850°C), reducing corrosion resistance; low-carbon or stabilized grades resist.

Visual inspection is the most common and first inspection method; it detects surface defects, alignment, and weld size.

Dye penetrant testing (PT) detects surface-breaking defects in nonporous materials; magnetic particle testing (MT) detects surface and near-surface defects in ferromagnetic materials.

Radiographic testing requires safety procedures for radiation; film density and IQI (image quality indicator) ensure sensitivity.

Ultrasonic testing uses high-frequency sound waves; couplant is required to transmit sound; it is effective for thick sections and planar defects.

Welding safety: arc eye (photokeratitis) from UV radiation; use proper filter lens; protect others with screens.

Fumes and gases: ensure ventilation; welding in confined spaces requires gas monitoring and respiratory protection.

Electrical safety: inspect cables and electrode holders; use dry insulation and proper grounding; avoid welding in wet conditions.

Fire prevention: remove combustibles within 11 m (35 ft) of welding; use fire watch and appropriate extinguishers; hot work permit required.

Qualification records (WPS, PQR, WPQ) must be retained and available for inspection; they are part of the quality program.