Cert III Welding cheat sheet

Hierarchy of control, highest to lowest: eliminate the hazard, substitute, engineer controls (isolation, ventilation, guarding), administrative controls (procedures, signage, training), then PPE as the last line of defence.

Welding fume is controlled by extraction at the arc (capture velocity roughly 0.5-1.0 m/s at the source); general dilution ventilation alone is inadequate for confined or high-fume processes such as flux-cored and MMAW.

Hot work permit rule: combustible material within 10-11 m of the arc must be removed, shielded with fire blankets, or wetted; a fire watch is maintained during work and for at least 30-60 minutes after completion.

Arc flash (UV/visible radiation) is blocked by filter shade numbers: shade 10-11 for MMAW at 100-200 A, shade 9-10 for MIG/MAG at 100-200 A, shade 5-6 for oxy-fuel gas welding; higher amperage requires a higher shade.

Electric shock risk rises with welding current above about 30 mA through the body; open-circuit voltages for MMAW typically 50-90 V, so dry gloves, insulated electrode holders and an earth-leakage device are mandatory.

Oxygen and fuel gas cylinders are stored separately (oxygen and acetylene at least 3 m apart or separated by a fire-resistant barrier), secured upright, and kept away from ignition sources and grease/oil for oxygen fittings.

Confined space entry requires an atmosphere test (oxygen 19.5-23.5%, flammable gas below 5% LEL, contaminants below exposure standard), a standby person, continuous ventilation and a rescue plan before entry.

Manual handling rule: keep the load close to the body, avoid twisting, and use two-person lifts or mechanical aids for cylinders and plate over about 20-25 kg; report musculoskeletal symptoms early.

Hazard reporting and consultation: workers must be consulted on WHS matters, hazards reported and recorded, incidents notified to the regulator where serious injury or dangerous occurrence occurs, and PPE maintained and replaced when damaged.

First-angle projection places the view on the far side of the object (view from the front is drawn behind the front view); third-angle projection places the view on the near side (top view above the front view). The projection symbol on the drawing confirms which system is used.

Scale is read as drawing:real; a 1:10 detail means 1 mm on the paper equals 10 mm on the part, so a 35 mm scaled dimension equals 350 mm actual.

Weld symbols follow AS/NZS 1100 / ISO 2553 conventions: the arrow line points to the joint, the reference line carries the symbol, the tail carries the process or specification, the size is placed left of the symbol and the length/pitch right of it.

A fillet weld symbol with a dimension left of the symbol gives the leg length; a dimension right of the symbol gives weld length, and a figure after a dash gives the pitch of intermittent welds (e.g. 6-100 means 6 mm leg, 100 mm pitch).

A circle at the junction of the arrow and reference line means weld all around; a flag means weld on site; a tail with no note means no specification is required; a double reference line means weld on both sides.

A V-groove symbol with the V opening toward the arrow side means the preparation is on the arrow side; a V on the other side of the reference line means preparation on the other side; a K symbol indicates a double-bevel or double-V preparation.

Surface finish and inspection symbols: a number above the reference line (e.g. 1 or 2) may indicate inspection level or finish; a U beside the symbol means weld profile flush, a convex or concave arc indicates finish contour, and a letter in the tail names the applicable standard.

Dimension tolerances are read from the title block and general notes; unspecified tolerances apply to all dimensions, and welding symbols take precedence over general notes where they conflict. Always check revision status before fabrication.

MMAW (stick): constant-current power source, electrode negative or positive depending on electrode type, typical current 80-200 A for 2.5-4.0 mm electrodes; deposition rate is lower than wire processes but it suits outdoor and positional work.

GMAW (MIG/MAG): constant-voltage (constant-potential) source; wire feed speed sets current and voltage sets arc length. Short-circuit transfer suits thin sheet, spray transfer suits thicker plate in flat position, and pulsed transfer gives spray-like transfer at lower average current.

GTAW (TIG): constant-current source with high-frequency or lift-arc start; AC is used for aluminium to break the oxide film, DCEN for steel; filler is added separately and the arc is shielded by argon or helium.

FCAW: tubular wire with flux core; self-shielded wire needs no external gas and tolerates wind, gas-shielded wire gives better toughness; typical current 150-350 A and deposition rates are higher than MMAW.

SAW (submerged arc): arc is buried under granular flux, giving very high deposition and no visible arc; it is limited to flat and horizontal positions and requires flux handling and recovery equipment.

Oxy-acetylene welding: neutral flame has a ratio of about 1:1 oxygen to acetylene; a carburising flame (excess acetylene) is used for some hardfacing and aluminium, an oxidising flame for brass; maximum safe working pressure for acetylene is about 100-150 kPa (1-1.5 bar).

Power source duty cycle: a 60% duty cycle at 250 A means the machine can run 6 minutes in every 10 at 250 A; exceeding duty cycle causes thermal overload trips. Cable size and earth return must match the current to avoid voltage drop and overheating.

Equipment checks before use: inspect leads for cuts and exposed conductors, check the earth clamp and work return, confirm gas hoses and flashback arrestors are fitted, and set polarity per the electrode or wire specification.

Carbon steel classification: low-carbon (mild) steel has roughly 0.05-0.25% C and welds readily; medium-carbon 0.25-0.60% C needs preheat and low-hydrogen consumables; high-carbon above 0.60% C requires careful preheat and is prone to cracking.

Carbon equivalent (CE) formula: CE = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15. CE above about 0.40-0.45% indicates a need for preheat; higher CE means higher preheat and interpass control.

Stainless steel 304 (18% Cr, 8% Ni) is welded with 308L filler; 316 with 316L; low-carbon 'L' grades limit carbide precipitation and sensitisation in the heat-affected zone. Duplex stainless needs controlled heat input and nitrogen-bearing filler.

Aluminium: oxide layer melts near 2050 C versus aluminium near 660 C, so the oxide must be removed mechanically or by AC cleaning action; use 5356 filler for 5xxx/6xxx alloys and 4043 for general purpose and castings; preheat is not usually required.

Consumable storage: low-hydrogen electrodes (E7018 class) must be stored in a heated holding oven at about 100-150 C and baked per manufacturer instructions; cellulose electrodes (E6010/E6011) tolerate moisture but should be kept dry.

Shielding gas selection: argon for GTAW and thin GMAW, argon/CO2 mixes (e.g. 75/25 or 92/8) for carbon steel GMAW, argon/helium for aluminium and thick sections, and CO2 for deep penetration at lower cost but with more spatter.

Joint preparation: bevel angle, root gap and root face control penetration. A typical single-V butt joint uses a 60-75 degree included angle with a 1.5-3 mm root gap and a 1.5-2 mm root face; excessive root gap causes burn-through, insufficient gap causes lack of penetration.

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

Travel angle: for MMAW and GMAW, a drag (backhand) angle of 5-15 degrees is used for most flat and horizontal work; a push (forehand) angle improves visibility and bead appearance on thin sheet but reduces penetration.

Work angle: the electrode is held at about 45 degrees to both plates for a fillet weld in a T-joint; for a butt weld the electrode bisects the joint, with the angle adjusted for vertical and overhead positions.

Arc length: keep arc length roughly equal to electrode diameter for MMAW. Too long an arc causes spatter, porosity and undercut; too short causes sticking and poor fusion.

Current setting: too low gives lack of fusion, high crown and slag inclusions; too high gives undercut, spatter, burn-through and wider HAZ. Current is adjusted for position, thickness and joint type, with lower current for vertical and overhead work.

Stringer versus weave: a weave bead is limited to about 2-3 times the electrode diameter; wide weaving in vertical-up work increases heat input and the risk of slag entrapment and distortion. Stringer beads give better toughness in high-heat-input-restricted work.

Distortion control: use balanced (backstep) welding, alternate sides, clamp or fixture the work, presetting, and keep heat input low. Backstep welding starts each bead behind the previous one and progresses toward the free end.

Tack welds: tacks should be at least as thick as the root pass and long enough (about 10-15 mm for thin plate) to hold alignment; tacks must be inspected for cracks and fully fused into the final weld, otherwise they become a crack initiation site.

Vertical-up versus vertical-down: vertical-up gives deeper penetration and better fusion and is used for structural work; vertical-down is faster and suits thin sheet but gives shallow penetration and is not permitted on many structural joints.

Slag removal and interpass cleaning: remove slag and spatter between passes with a chipping hammer and wire brush; incomplete cleaning causes slag inclusions, and interpass temperature must be checked with a contact thermometer or temperature crayon.

Visual inspection (VT) is the first and most common test: check bead profile, leg length and throat, undercut, overlap, spatter, porosity, cracks and dimensional accuracy against the drawing and acceptance standard.

Fillet weld sizing: leg length is measured with a weld gauge; throat thickness equals leg length times 0.707 for a 90-degree fillet. Undercut limits are typically 0.5-1.0 mm depending on the standard and joint class.

Non-destructive testing methods: dye penetrant (PT) finds surface-breaking defects in non-porous materials; magnetic particle (MT) finds surface and near-surface defects in ferromagnetic steel; ultrasonic (UT) finds internal planar defects; radiography (RT) finds internal volumetric defects and needs radiation controls.

Destructive tests: bend tests (face, root, side) reveal fusion and ductility; nick-break tests expose internal defects; macro and micro examination show penetration and HAZ structure; tensile and impact tests verify mechanical properties.

Weld defect causes: porosity from moisture, oil or gas flow problems; slag inclusion from poor interpass cleaning or low current; lack of fusion from low heat input or wrong angle; undercut from excessive current or travel speed; cracking from hydrogen, restraint or high CE.

Hydrogen-assisted (cold) cracking occurs hours to days after welding; prevention is low-hydrogen consumables, preheat, controlled interpass temperature, and avoiding rapid cooling. It is most common in thick sections and high-strength steels.

Pressure and leak testing: hydrostatic testing is performed above design pressure with a safety factor; pneumatic testing is more dangerous because of stored energy and requires extra exclusion zones. Leak testing may use soap solution or tracer gas.

Welding procedure qualification: a WPS is supported by a PQR (procedure qualification record) from destructive testing; welders are qualified to a standard such as AS/NZS 2980 or ISO 9606, and qualification covers position, process, thickness and joint type.

Wire feed problems: check drive rolls for correct groove size and tension, liner for kinks or blockage, contact tip for wear and spatter build-up, and spool for free rotation. Bird-nesting indicates excessive tension or a blocked liner.

Porosity troubleshooting: check gas flow rate (typically 10-15 L/min for GMAW), gas leaks and hoses, regulator and solenoid operation, draughts, and moisture or oil on the work. Too high a flow causes turbulence and draws in air.

Arc instability: check earth return connection and clamp condition, cable and connector tightness, electrode condition and polarity, and power source settings. A poor work return causes erratic arc, overheating and voltage drop.

Duty cycle and thermal overload: if the machine trips on overload, allow it to cool; repeated trips indicate the duty cycle or ventilation is inadequate. Clean cooling fans and vents and keep the machine clear of dust.

Cylinder and regulator maintenance: check regulators for leaks with soap solution, never use oil on oxygen fittings, fit flashback arrestors at the regulator and torch, and replace damaged hoses rather than taping them.

Housekeeping: keep walkways clear, store leads off the floor and out of traffic, remove slag and spatter from the work area, and keep combustible material out of the hot work zone. Spent electrode stubs go in metal bins, not general waste.

Preventive maintenance schedule: inspect leads and holders daily, check gas hoses and regulators weekly, service the wire feeder and clean the liner periodically, and record maintenance. Tag out and remove defective equipment from service.

Environmental controls: segregate waste streams (metal offcuts, spent flux, used oil, batteries), manage fume extraction filters, control noise and use correct disposal for chemical and coolant waste per site procedures.

Work instructions and job documentation: read the job card, drawing revision, WPS and inspection requirements before starting; confirm any unclear dimension or symbol with the supervisor rather than assuming.

Handover and shift communication: record work completed, defects found, consumable and gas levels, and equipment issues in the shift log; verbal handover should be confirmed back to ensure understanding.

Team roles on a welding job: the welder, TA (trade assistant), supervisor, inspector and safety officer each have defined responsibilities; the welder is responsible for the quality of their own work and for reporting non-conforming product.

Non-conformance reporting: tag or segregate defective work, record the defect and its location, and follow the site's NCR process. Never cover up or rework a defect without authorisation and re-inspection.

Industry standards and codes: AS/NZS 1554 covers structural steel welding, AS/NZS 3992 covers pressure equipment welding, AS 2980 covers welder qualification; the applicable standard is nominated in the specification and governs acceptance criteria.

Environmental and sustainability practice: minimise waste by nesting and offcut use, recycle metals and consumable packaging, and control fume, noise and light spill to protect the community and environment.

Records and traceability: keep test records, welder qualification certificates, consumable batch records and inspection reports; traceability allows a defect to be linked to a batch of consumables or a welder.

Continuous improvement and consultation: report recurring problems, suggest improvements to jigs and procedures, and participate in toolbox talks and risk assessments. Workers must be consulted on changes affecting their health and safety.

Hierarchy of control: eliminate, substitute, engineer, administrate, then PPE last.

Fume extraction capture velocity at the arc is roughly 0.5-1.0 m/s.

Hot work: remove combustibles within 10-11 m; fire watch during and 30-60 minutes after.

Filter shade rises with current: about 9-11 for arc welding at 100-200 A, 5-6 for gas welding.

Cylinders: oxygen and acetylene at least 3 m apart or separated by a fire-resistant barrier.

Confined space: oxygen 19.5-23.5%, flammable gas below 5% LEL, standby person and rescue plan.

Report hazards and incidents; serious incidents are notified to the regulator.

First-angle: view placed on the far side; third-angle: view placed on the near side.

Scale 1:10 means 1 mm on paper equals 10 mm actual.

Weld size is left of the symbol; length and pitch are right of it.

Circle at the junction means weld all around; flag means weld on site.

Double reference line means weld both sides of the joint.

Tail carries the process or specification; empty tail means no specification.

Symbols take precedence over general notes; check the revision before fabrication.

MMAW: constant-current source; typical 80-200 A for 2.5-4.0 mm electrodes.

GMAW: constant-voltage source; wire feed speed sets current, voltage sets arc length.

GTAW: constant-current; AC for aluminium, DCEN for steel; argon or helium shielding.

FCAW: self-shielded wire tolerates wind; gas-shielded wire gives better toughness.

SAW: arc buried in flux; flat and horizontal only; very high deposition.

Neutral oxy-acetylene flame is about 1:1; acetylene working pressure is limited to about 100-150 kPa.

Duty cycle 60% at 250 A means 6 minutes welding in every 10 minutes.

CE = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15; above about 0.40-0.45% indicates preheat is needed.

Mild steel is about 0.05-0.25% C and welds readily; above 0.60% C needs careful preheat.

304 stainless uses 308L filler; 316 uses 316L filler.

Aluminium oxide melts near 2050 C versus aluminium near 660 C; remove oxide mechanically or with AC cleaning.

5356 filler for 5xxx/6xxx alloys; 4043 for general purpose and castings.

Low-hydrogen electrodes are held at about 100-150 C in a heated oven.

Single-V butt joint: 60-75 degree included angle, 1.5-3 mm root gap, 1.5-2 mm root face.

Drag angle 5-15 degrees for most flat and horizontal work; push angle reduces penetration.

Fillet T-joint work angle is about 45 degrees to both plates.

Arc length roughly equals electrode diameter for MMAW.

Too low current gives lack of fusion and high crown; too high gives undercut and burn-through.

Weave width is limited to about 2-3 times the electrode diameter.

Backstep welding starts each bead behind the previous one and moves toward the free end.

Vertical-up gives deeper penetration than vertical-down and is used for structural work.

Fillet throat thickness equals leg length times 0.707.

PT finds surface-breaking defects; MT finds surface and near-surface defects in ferromagnetic steel.

UT finds internal planar defects; RT finds internal volumetric defects.

Bend, nick-break, macro and tensile tests are destructive tests.

Porosity comes from moisture, oil or gas problems; slag inclusion from poor cleaning or low current.

Hydrogen-assisted cold cracking appears hours to days after welding; prevent with low-hydrogen consumables and preheat.

A WPS is supported by a PQR; welders are qualified to AS/NZS 2980 or ISO 9606.

Bird-nesting indicates excessive drive roll tension or a blocked liner.

GMAW gas flow is typically 10-15 L/min; too high causes turbulence and porosity.

Erratic arc often means a poor earth return or loose cable connection.

Repeated thermal overload trips indicate duty cycle or ventilation problems.

Check regulators for leaks with soap solution; never use oil on oxygen fittings.

Spent electrode stubs go in metal bins, not general waste.

Tag out and remove defective equipment from service; record maintenance.

Read the job card, drawing revision, WPS and inspection requirements before starting.

Record completed work, defects, consumable levels and equipment issues in the shift log.

Tag or segregate non-conforming work and follow the NCR process.

AS/NZS 1554 covers structural steel; AS/NZS 3992 covers pressure equipment; AS 2980 covers welder qualification.

Keep welder qualification, consumable batch and inspection records for traceability.

Recycle metals and packaging; control fume, noise and light spill.

Workers must be consulted on changes affecting health and safety.