Advanced Diagnostics & Troubleshooting Flashcards

A SAW weld on carbon steel passes RT but fails UT due to planar indications mid-thickness that are not visible on X-ray. These are most likely:

Answer: Lack of fusion or delamination-type defects oriented parallel to the beam

Planar defects such as lack of fusion oriented parallel to the X-ray beam present little radiographic contrast but reflect ultrasound strongly, explaining UT detection without RT indication.

A SAW machine running on AC power shows arc extinction and re-ignition difficulty at current reversals. Which adjustment should be tried first?

Answer: Increase open-circuit voltage or switch to a power source with better arc re-ignition capability

AC arc extinction at current zero-crossings requires sufficient open-circuit voltage and flux ionization potential to re-ignite; a higher OCV or arc-stabilized power source resolves this.

A flux-cored wire is accidentally substituted for solid SAW wire in a procedure. The most immediate observable consequence during welding would be:

Answer: Excessive internal porosity and a highly irregular bead due to core ingredient incompatibility with the SAW flux blanket

FCAW wires are designed for open-arc or gas-shielded environments; under SAW flux, core ingredients react unpredictably, causing severe porosity and erratic bead formation.

After a SAW procedure qualification, the weld metal carbon equivalent (CE) is higher than anticipated. Which wire characteristic should be reviewed?

Answer: Wire heat number chemistry, specifically carbon and manganese content

Carbon equivalent is calculated from actual wire chemistry; a heat with elevated carbon or manganese content directly raises CE beyond expected values.

During SAW strip cladding of a pressure vessel, dilution of the base metal into the overlay is measured above the 10% maximum allowed. Which parameter change most directly reduces dilution?

Answer: Reduce welding current while maintaining voltage

Reducing current decreases arc penetration force, which is the primary driver of base metal dilution in strip cladding applications.

A SAW weld made in the 1G (flat) position on a grooved joint shows consistent lack of sidewall fusion on the left groove face only. What is the most probable cause?

Answer: The electrode is angled (work angle) toward the right side of the joint, focusing arc pressure away from the left wall

An off-center or angled electrode directs arc force and heat preferentially to one side, leaving the opposite groove wall insufficiently fused.

A SAW weld repair on a casting is rejected due to hydrogen-induced cracking found 48 hours after welding. Which preventive measure would have been most effective?

Answer: Maintaining the preheat temperature for a post-weld hydrogen bake-out period before allowing the weld to cool

A controlled post-weld dehydrogenation heat treatment (bake-out) allows hydrogen to diffuse out before the weld cools to temperatures where cracking initiates.