Welding Processes & Techniques Flashcards

Which shielding gas mixture is most commonly used for MIG welding carbon steel in the US?

Answer: 75% argon / 25% CO2

A 75/25 argon/CO2 mix (C25) provides good arc stability and weld appearance for carbon steel MIG welding.

What is the primary purpose of a backing bar (backing strip) in groove welding?

Answer: To support the root pass and prevent burn-through

A backing bar supports the molten weld pool during the root pass to prevent burn-through and achieve full joint penetration.

In GMAW, what does 'short-circuit transfer' mean?

Answer: The wire contacts the puddle repeatedly, extinguishing and re-igniting the arc

Short-circuit transfer occurs when the wire electrode contacts the weld puddle, short-circuits, and the arc re-ignites repeatedly at high frequency.

Which welding process is best suited for welding thin-gauge aluminum sheet?

Answer: GTAW

GTAW (TIG) offers precise heat control and produces clean, high-quality welds ideal for thin aluminum sheet without contamination.

What causes porosity in a weld bead?

Answer: Contamination or inadequate shielding gas coverage

Porosity results from gas pockets trapped in the weld, commonly caused by moisture, oil, rust, or loss of shielding gas coverage.

When welding in the vertical position (3G), what technique reduces sagging of the weld pool?

Answer: Using a weave or uphill progression with a slight pause at the toes

Uphill progression with a slight pause at the weld toes allows the pool to solidify enough to resist gravity-induced sagging.

What does 'interpass temperature' refer to in multi-pass welding?

Answer: The maximum temperature of the weld joint before depositing the next pass

Interpass temperature is the maximum allowable temperature of the weld joint between passes to control heat input and prevent metallurgical damage.