FCAW NC II flashcards

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

FCAW polarity gas-shielded

Gas-shielded flux-cored wires are normally connected DCEP (electrode positive). Self-shielded wires are normally DCEN. Always confirm on the wire manufacturer's data sheet before welding.

Heat input formula

Heat input in kJ/mm equals voltage times current times 60, divided by travel speed in mm per minute times 1000. Keep it within the WPS range to control toughness and distortion.

Contact tip bore size

The contact tip bore should be about 0.1 to 0.2 mm larger than the wire diameter. An oval or spatter-blocked bore causes erratic arc, burnback, and poor feed.

Duty cycle meaning

Duty cycle is the percentage of a 10-minute period a machine can operate at a rated current. A 60% rating at 250 A allows 6 minutes welding and 4 minutes cooling.

Arrow side convention

On a welding symbol, the arrow side is the side the arrow points to and its weld is placed below the reference line. The other side weld goes above the line.

All-around weld symbol

A circle at the junction of the arrow line and reference line means the weld continues all around the joint. It is not the same as a field weld flag.

Field weld symbol

A flag at the junction of the arrow line and reference line indicates a field weld, meaning the weld is made at the installation site rather than in the fabrication shop.

Fillet weld size notation

On a fillet symbol the leg size sits left of the triangle and the length sits right of it. A length followed by a dash and pitch indicates an intermittent weld.

Carbon equivalent preheat rule

CE equals C plus Mn/6 plus (Cr+Mo+V)/5 plus (Ni+Cu)/15. Values above about 0.40 raise cold-cracking risk, so preheat and interpass control per the WPS become critical.

Typical V-groove dimensions

A common single-V butt joint uses 30 degrees bevel per side, a 1.5 to 2.5 mm root face, and a 2 to 3 mm root gap. Deviations change penetration and burn-through risk.

Surface cleaning width

Remove mill scale, rust, oil, paint, and moisture at least 25 mm on each side of the joint. Contamination causes porosity and hydrogen-assisted cracking in high-strength steels.

Shielding gas flow range

For 1.2 mm gas-shielded flux-cored wire, typical flow is 15 to 20 L/min. Too low causes porosity from air ingress; too high causes turbulence and also porosity.

Burnback causes

Burnback, where the arc melts wire back to the tip, usually means wire-feed speed is too low or voltage is too high. Correct the balance before replacing the tip.

Stubbing causes

Stubbing, where the wire drives into the workpiece and stops, usually means wire-feed speed is too high or voltage is too low. Check the liner and drive rolls too.

Birdnesting wire feed

Birdnesting is wire tangling at the drive rolls. Causes include excessive drive roll pressure, a kinked or clogged liner, or the wrong drive roll groove size.

Electrode stick-out FCAW

Stick-out for FCAW is typically 10 to 25 mm. Longer stick-out raises deposition rate but reduces penetration and can cause lack of fusion if excessive.

FCAW travel angle

Gas-shielded FCAW usually uses a push angle of 5 to 15 degrees. Some self-shielded wires use a drag angle. Fillet work angle is about 45 degrees.

Weave width limit

For FCAW, weave width should not exceed about three times the electrode diameter. Wider weaves increase slag entrapment and lack-of-fusion risk.

Crater filling practice

Fill the crater by pausing or back-stepping before breaking the arc. An unfilled crater is a common crack initiation site in finished welds.

Wind effect on shielding

Gas-shielded FCAW loses shielding above about 2 m/s draft, roughly 7 km/h. Use windbreaks or switch to a self-shielded wire for outdoor work.

Undercut acceptance limit

Undercut is typically limited to about 0.5 mm deep or 10 percent of thickness, whichever is less, depending on quality level. Always check the applicable code criteria.

Planar defect detection

Lack of fusion and lack of penetration are planar defects. Visual inspection cannot find them; ultrasonic testing or radiography is required for detection.

Slag inclusion appearance

On a radiograph, slag inclusion appears as elongated dark lines. It usually results from poor interpass cleaning or an incorrect travel angle during welding.

Magnetic particle testing use

Magnetic particle testing finds surface and near-surface defects in ferromagnetic steel. It cannot be used on austenitic stainless steel, where dye penetrant testing is used instead.

Defect versus discontinuity

A discontinuity is any interruption in the weld. It becomes a defect only when it exceeds the acceptance criteria of the applicable standard or specification.

Post-weld heat treatment

PWHT relieves residual stress and lowers hardness. For carbon steel, stress relief is typically 550 to 650 degrees C with controlled heating and cooling rates per the WPS.

Stainless steel brush rule

Use a dedicated stainless steel wire brush for stainless work. Carbon steel brushes leave iron particles that cause rust staining and contamination on the stainless surface.

Weld traceability records

Record the welder ID, WPS number, consumable lot, and date for each weld. This lets the weld be traced to its procedure and operator during audits.

PDCA in welding quality

Plan defines WPS and quality requirements, Do executes them, Check inspects and tests, Act corrects and standardizes. Use it to address recurring defect trends.

Six M cause categories

Ishikawa analysis groups causes into man, machine, material, method, measurement, and environment. Use it with 5 Whys to find the root cause of weld defects.

Local exhaust ventilation

LEV captures fume at the arc before it reaches the breathing zone. It is the first control in the hierarchy, ahead of administrative controls and respiratory protection.

Hot work fire watch

Remove or protect combustibles within 10 to 11 m, assign a fire watch during welding and for at least 30 minutes after, and keep a suitable extinguisher at the station.