FCAW NC II cheat sheet

FCAW arc radiation is primarily ultraviolet; UV burns the cornea (arc eye) and skin. Minimum eye protection for the operator is a welding helmet with a filter shade appropriate to current (commonly shade 10-13 for FCAW at 100-300 A); bystanders need shade 2-3 or a screen.

Fume extraction hierarchy: engineering controls first (LEV, local exhaust ventilation at the arc, extraction torch), then administrative controls, then PPE (respirator). A powered air-purifying respirator (PAPR) with P2/P3 filter is used where LEV alone does not keep exposure below the workplace exposure limit.

FCAW with CO2 or Ar/CO2 shielding produces carbon monoxide and ozone; never weld in a confined space without forced ventilation and atmospheric testing (O2 19.5-23.5%, CO and flammable gas within limits).

Gas cylinder rules: store upright, secured, valve cap on when not in use, away from heat and ignition; keep oxygen and fuel gas separated by at least 5 m or a fire-rated barrier; no oil or grease on oxygen fittings.

Hot work precautions: remove or protect combustibles within 10-11 m, use fire blankets, assign a fire watch during and at least 30 minutes after welding, and have a suitable extinguisher at the work station.

Electrical safety: welding return (work) lead must be clamped as close as practicable to the arc; open-circuit voltage for FCAW can exceed 50 V, so dry gloves, insulated electrode holder, and an inspected ground connection are mandatory.

Environmental protection: segregate and label metal swarf, spent wire spools, slag, and used filter cartridges; welding fume contains manganese and hexavalent chromium (when welding stainless), so capture at source rather than dilute with general ventilation.

Noise from grinding and from wire-feed/plasma operations can exceed 85 dB(A); hearing protection is required at or above 85 dB(A) over an 8-hour equivalent, and PPE is mandatory where engineering controls cannot reduce noise.

Angle grinder safety: guard in place, correct disc for RPM rating (disc max RPM must be at least the tool no-load RPM), no cutting disc used for side grinding, and a dead-man switch that stops the disc when released.

Wire feeder maintenance: check drive rolls for the correct groove profile and size for the wire diameter (V-groove for solid, U-groove or knurled for flux-cored), set drive roll pressure just enough to prevent slip, and blow out the liner with dry compressed air.

Contact tip rule: tip bore should be about 0.1-0.2 mm larger than the wire diameter; replace when the bore wears oval or spatter bridges it, because that causes erratic arc and burnbacks.

Liner length and condition: a kinked or clogged liner causes wire stubbing and feed surges; replace when the wire no longer passes freely and check that the liner is trimmed flush with the gun connector.

Power tool inspection before use: check cord and plug for damage, test the RCD/GFCI, verify the tool is switched off before plugging in, and never remove or defeat a guard.

Hand tool rules: use the correct spanner size on regulator and gas fittings, never use a pipe extension to increase torque on a regulator nut, and discard chipped chipping hammers and mushroomed chisels.

Welding machine maintenance: keep cooling vents clear, check coolant level and flow on water-cooled guns, inspect torch cable for cuts, and record the maintenance in the equipment log.

Calibration: ammeters, voltmeters, gas flowmeters, and wire-feed speed indicators should be verified against a reference at defined intervals; a flowmeter reading error of 2-3 L/min changes shielding quality.

On an ISO 2553 / AWS A2.4 symbol, the reference line carries the arrow; the tail holds process and standard references; the arrow side is below the reference line and the other side above it.

A fillet weld symbol shows the leg size to the left of the triangle and the length to the right; a length without a spacing value means continuous weld, while length with a dash and pitch means intermittent (e.g. 50-150).

The all-around symbol (circle at the reference line junction) means the weld continues around the joint; the field weld symbol (flag) means the weld is made at the site, not in the shop.

A groove weld symbol shows the groove preparation (V, U, J, bevel) with the groove depth or root gap, and a number in parentheses after the size indicates the number of weld passes or the effective throat.

Supplementary symbols: a convex contour is shown by a convex arc over the symbol, a flush contour by a straight line, and a concave contour by a concave arc; a letter after the contour indicates the finishing method (G = grinding, M = machining).

Drawing scale and dimension notes: never scale a drawing to obtain a weld size; the dimensioned value governs. Check the general notes and welding procedure specification reference block for preheat, interpass, and consumable requirements.

The welding procedure specification (WPS) governs, not the drawing, when they conflict on parameters; a procedure qualification record (PQR) supports the WPS, and the welder must be qualified to the applicable standard (e.g. ISO 9606 or ASME IX).

Tolerance blocks and title-block data: check the projection method (first vs third angle), units (mm vs inch), and the tolerance class before interpreting dimensions.

Bevel angle and root face: a typical single-V butt joint uses 30 degrees per side (60 degree included) with a 1.5-2.5 mm root face and 2-3 mm root gap; too large a root gap increases burn-through risk, too small causes lack of penetration.

Surface preparation: remove mill scale, rust, oil, paint, and moisture at least 25 mm either side of the joint; contamination causes porosity and hydrogen-assisted cracking in high-strength steels.

Preheat decision rule: follow the WPS; for carbon-equivalent (CE = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15) above about 0.40, preheat and interpass control become critical to avoid cold cracking.

Fit-up checks: use a root gap gauge, a bevel protractor, and a straight edge; tack welds must be made with the qualified procedure and be free of cracks, and they become part of the finished weld unless removed.

Distortion control: use balanced welding sequence, back-step technique, minimum restraint, and preset (pre-bending) for long butt joints; keep heat input uniform across the joint.

Tack weld spacing and length: for plate up to about 6 mm, tacks of 10-15 mm at 150-300 mm spacing are typical; tacks must be full penetration or removed before welding.

Joint types: butt, lap, T, corner, and edge; FCAW is commonly used for fillet welds in T and lap joints and for butt welds with backing or open root with a suitable transfer mode.

Material identification: verify the steel grade against the drawing and check certificates (EN 10204 3.1) before cutting; never mix stainless and carbon steel tools or grinding discs to avoid contamination.

FCAW polarity: gas-shielded flux-cored wires are usually run DCEP (electrode positive); self-shielded wires are usually run DCEN. Check the wire manufacturer's data sheet before connecting.

Parameter relationship: current is set mainly by wire-feed speed; voltage is set by the machine and controls arc length. Increasing WFS raises current and penetration; increasing voltage lengthens the arc, flattens the bead, and widens it.

Typical FCAW range for 1.2 mm wire: 150-280 A, 22-28 V, gas flow 15-20 L/min for CO2 or Ar/CO2; self-shielded wires run higher current density and need no gas.

Shielding gas: CO2 gives deep penetration and is cheap but produces more spatter; Ar/CO2 (e.g. 75/25 or 80/20) gives smoother transfer and less spatter but slightly less penetration. Flow too low causes porosity; too high causes turbulence and porosity.

Wire feed problems: burnback is usually too low WFS or too high voltage; stubbing is too high WFS or too low voltage; birdnesting is excessive drive roll pressure or a kinked liner; porosity is gas flow, wind, or contamination.

Duty cycle: a machine rated 60% at 250 A can run 6 minutes out of 10 at 250 A; exceeding duty cycle causes thermal trips. Check the rating plate against the intended current.

Stick-out (electrode extension) for FCAW is typically 10-25 mm; increasing stick-out raises deposition rate but reduces penetration and can cause lack of fusion if excessive.

Inductance and slope: higher inductance softens the arc and reduces spatter; too low inductance gives a harsh, spattery arc. Set inductance after the voltage and WFS are correct.

Travel angle for FCAW is typically a push (forehand) angle of 5-15 degrees for gas-shielded wire; a drag angle is used for some self-shielded wires. Work angle for a fillet is about 45 degrees, biased slightly into the vertical member.

Heat input formula: HI (kJ/mm) = (voltage x current x 60) / (travel speed in mm/min x 1000). Keep within the WPS range; excessive heat input reduces toughness and increases distortion.

Stringer versus weave: weave width should not exceed about 3 times the electrode diameter for FCAW; wider weaves risk slag entrapment and lack of fusion.

Slag control: FCAW produces a slag covering; clean each pass before the next, and never restart an arc inside the crater without first removing slag. Use a chipping hammer and wire brush.

Crater treatment: fill the crater by pausing or using a back-step before breaking the arc; an unfilled crater is a common crack initiation site.

Multi-pass sequence: for thick sections, balance the passes (alternate sides) to control angular distortion; maintain interpass temperature within the WPS limit (often 250 degrees C maximum for carbon steel).

Wind and draft: gas-shielded FCAW loses shielding above about 2 m/s (approx. 7 km/h) draft; use windbreaks or switch to self-shielded wire outdoors.

Weld procedure compliance: the welder must follow the WPS for current, voltage, travel speed, preheat, and consumable; any deviation requires a new or revised WPS and requalification.

Visual inspection (VT) is performed before, during, and after welding; it detects surface porosity, undercut, overlap, spatter, and crater cracks but cannot detect internal lack of fusion or slag.

Undercut limit: typically not more than 0.5 mm deep or 10% of material thickness, whichever is less, for quality level B/C depending on the standard; check the acceptance criteria in the applicable code.

Porosity acceptance: isolated pores are often acceptable below a size and density limit; clustered or linear porosity indicates a gas or contamination problem and is generally rejectable.

Lack of fusion and lack of penetration are planar defects and are the most common causes of FCAW joint failure; they are detected by ultrasonic testing (UT) or radiography (RT), not by VT.

Slag inclusion appears as elongated dark lines on a radiograph; it usually results from poor interpass cleaning or incorrect travel angle.

Destructive tests: bend test (root and face) reveals fusion defects; macro-section (etch with 2-5% nital) shows penetration, fusion, and heat-affected zone; tensile and Charpy tests verify strength and toughness.

Magnetic particle testing (MT) detects surface and near-surface defects in ferromagnetic steel; dye penetrant testing (PT) detects surface-breaking defects in non-magnetic materials such as austenitic stainless steel.

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

Post-weld heat treatment (PWHT): used to relieve residual stress and reduce hardness; typical stress-relief range for carbon steel is 550-650 degrees C with controlled heating and cooling rates per the WPS.

Cleaning and finishing: remove slag, spatter, and weld splatter with a chipping hammer, wire brush, or grinder; use a dedicated stainless brush for stainless steel to avoid iron contamination and subsequent rusting.

Weld identification and traceability: mark welds with the welder's ID or stamp, and record the WPS number, consumable batch, and date so the weld can be traced to the procedure and the operator.

Consumable control: record wire lot/heat number, and store flux-cored wire in a dry place; opened spools should be protected from moisture, which causes hydrogen-related porosity.

Dimensional check after welding: verify distortion against drawing tolerances; straightening by flame or mechanical means must follow an approved procedure and not crack the weld.

Documentation package typically includes the WPS, PQR, welder qualification certificates, inspection reports (VT, RT, UT, MT, PT), material certificates, and the as-built drawing.

Repair procedure: excavate the defect to sound metal, re-weld per the WPS, and re-inspect the repair; repeated repairs in the same area may require engineering approval.

Final surface protection: apply the specified paint or coating after inspection acceptance; surface preparation grade (e.g. Sa 2.5) affects coating adhesion.

PDCA cycle: Plan (define weld quality requirements and WPS), Do (execute per procedure), Check (inspect and test), Act (correct and standardize). Use it for recurring defect trends.

Root cause analysis tools: 5 Whys and Ishikawa (fishbone) diagrams categorize causes into man, machine, material, method, measurement, and environment (6M).

Key welding quality metrics: weld repair rate, first-pass yield, defect rate by type, and consumable usage per meter of weld; track them per welder and per joint type to find trends.

Welder qualification records must be maintained and renewed per the applicable standard; a lapse in qualification invalidates the welds made after the lapse.

Calibration and traceability: measuring instruments (gauges, ammeters, flowmeters) must be calibrated and traceable; an out-of-calibration instrument invalidates the inspection result.

Document control: only the current revision of a WPS or drawing may be used at the work station; superseded documents must be removed to prevent wrong-revision welding.

Continuous improvement in FCAW often targets wire-feed consistency and gas flow control, since these two variables account for a large share of porosity and fusion defects.

Audit and inspection records should be retained for the period specified by the contract or standard; records support traceability and warranty claims.