I-CAR SWQT flashcards

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

Open-circuit voltage

Voltage present at the GMAW gun when not welding. Typically 15-35 V DC; higher values increase shock severity, especially with wet gloves or damp floors.

Fume extraction placement

Extraction hood must be within about 12 inches of the arc. Ceiling ventilation alone leaves zinc oxide and manganese fume in the welder's breathing zone.

Battery disconnect before welding

Disconnect the negative cable and wait the OEM-specified capacitor discharge time, often 1-10 minutes, before welding on a vehicle with sensitive electronics.

Acetylene cylinder storage

Acetylene cylinders must be stored and used upright, never laid on their side, and separated from oxygen by 20 feet or a 5-foot fire-rated barrier.

Fillet weld symbol size

Size is written to the left of the fillet triangle on the reference line. Length and pitch go to the right for intermittent welds.

Arrow side versus other side

Weld symbol above the reference line means weld on the arrow side. Below the line means the other side. Both means both sides.

Plug weld symbol

A rectangle on the reference line. Hole diameter is written to the left; number of holes appears above or below the symbol.

All-around and field weld

A circle at the arrow-reference junction means weld all around. A flag at the same junction means field weld, performed at the installation site.

Short-circuit transfer

Transfer mode where the wire contacts the puddle and extinguishes the arc repeatedly. Uses 75% argon/25% CO2 at low voltage for thin auto sheet.

C25 shielding gas

A mix of 75% argon and 25% CO2, the standard gas for auto-body GMAW on mild and high-strength steel sheet.

Wire feed speed versus voltage

Wire feed speed sets welding current. Voltage sets arc length. Mismatch causes stubbing (too little voltage) or spatter and poor fusion (too much).

Contact tip to work distance

Distance from contact tip to workpiece, normally 3/8 to 1/2 inch. Excessive stick-out reduces current and causes cold lap and lack of fusion.

STRSW heat formula

Heat generated equals current squared times resistance times time (H = I squared R t). Current and time dominate nugget size in spot welding.

STRSW weld sequence

Squeeze, weld, hold, off. Electrode force is applied before current and held after current so the nugget solidifies under pressure.

Shunt current in spot welding

Current that bypasses the intended faying surface through an adjacent nugget. Keep weld spacing at least four nugget diameters or per OEM.

Spot weld nugget target

Common automotive target is four times the square root of the thinner sheet thickness in millimeters, with a practical minimum near 3.5 mm.

Dual-phase steel

AHSS with ferrite and martensite microstructure, graded DP600 to DP980. Excess heat input softens the martensite and reduces heat-affected-zone strength.

Press-hardened steel

Boron-alloyed martensitic steel formed hot and quenched to about 1,500 MPa. Most OEMs prohibit GMAW, heating, and sectioning on these parts.

Heat input calculation

Heat input in kilojoules per inch equals voltage times current times 60, divided by travel speed in inches per minute.

MIG brazing

Joining with copper-silicon filler at about 1,800-2,000 degrees F, below steel melting. Preserves galvanized coating and strength on outer high-strength panels.

Bake-hardening steel

Mild steel that gains strength during paint bake cycles. Sensitive to preheat and interpass temperature, which OEM procedures usually cap or prohibit.

Untempered martensite HAZ

Brittle zone formed when press-hardened or martensitic steel is welded without OEM procedure. Prone to delayed cracking and rejected by OEM repair standards.

Preheat on AHSS

Generally prohibited because it widens the heat-affected zone and tempers base metal. Used only on thick mild steel or when the OEM specifies.

Heat straightening limit

Heating AHSS or UHSS above roughly 1,200 degrees F destroys strength. Most OEMs prohibit heat straightening on these parts entirely.

Lack of fusion

A smooth unfused interface seen on peel or chisel tests. Caused by low current, fast travel, wrong gun angle, or poor fit-up between sheets.

Undercut rejection limit

A groove melted into base metal at the weld toe and not refilled. Typically rejected when deeper than 0.5 mm or 10 percent of thickness.

Spot weld peel test

Bend or chisel the coupon to failure. A button pull-out with nugget remaining passes; an interfacial plug failure indicates a cold weld.

Crater crack

A crack at the end of a bead where the crater solidifies. Prevented by backstepping or filling the crater before breaking the arc.

Sectioning location rule

Cut only at OEM-designated locations, typically 3-6 inches from a body feature. Stagger inner and outer seams and never section press-hardened parts.

Spot weld replacement rule

Replace one factory spot weld with one plug weld or one squeeze-type resistance spot weld. Do not substitute a continuous seam unless the OEM specifies.

Weld-bonding

Structural adhesive combined with spot welds. Adhesive must be OEM-approved, applied at specified bead width, and welds placed before the adhesive cures.

High-voltage disable

On battery electric vehicles, disable the high-voltage system per OEM procedure, wait the discharge time, verify zero voltage, then weld away from HV cables.