308A Welding and Soldering for Sheet Metal

Question 1

What type of welding process is most commonly used for joining sheet metal in HVAC fabrication?

Accepted Answer

Gas Metal Arc Welding (GMAW/MIG)

Answer

Shielded Metal Arc Welding (SMAW/Stick)

Answer

Submerged Arc Welding (SAW)

Answer

Electroslag Welding (ESW)

Question 2

What is the primary difference between soldering and brazing?

Accepted Answer

Soldering uses filler metals that melt below 840°F (450°C), while brazing uses filler metals that melt above 840°F (450°C)

Answer

There is no difference

Answer

Brazing is only for copper

Answer

Soldering requires more heat than brazing

Question 3

What flux is commonly used when soldering galvanized sheet metal?

Accepted Answer

Zinc chloride (killed acid) flux or muriatic acid-based flux

Answer

No flux is needed

Answer

Borax flux

Answer

Silver brazing flux

Question 4

What is the correct soldering technique for a flat lock seam?

Accepted Answer

Heat the seam evenly, apply flux, and draw the solder through the entire seam by capillary action

Answer

Apply solder only to the outside surface

Answer

Use a torch to melt the base metal

Answer

Apply cold solder and heat it afterwards

Question 5

What safety hazard is specifically associated with soldering galvanized steel?

Accepted Answer

Zinc oxide fumes that can cause metal fume fever

Answer

Electric shock

Answer

Hydrogen gas explosion

Answer

Cyanide gas release

Question 6

What is the correct shielding gas for MIG welding mild steel sheet metal?

Accepted Answer

75% argon/25% CO2 (C25) or pure CO2

Answer

Pure oxygen

Answer

Pure nitrogen

Answer

Acetylene