Advanced Diagnostics & Troubleshooting Flashcards

A SAW joint shows burnthrough on a root pass of a thin plate despite using parameters within the WPS range. Which adjustment is most likely to eliminate this?

Answer: Switch from DCEP to DCEN to reduce penetration

DCEN (electrode negative) reduces penetration compared to DCEP, distributing heat more broadly and preventing burnthrough on thin sections.

After replacing a flux lot mid-production, the operator notices the arc is significantly more erratic despite using the same voltage and wire feed settings. What should be checked on the new flux lot?

Answer: Flux particle size distribution compared to the previous lot

A significantly different mesh size alters flux conductivity and melting behavior, causing arc instability even with identical process parameters.

When diagnosing excessive spatter in a SAW application, the technician finds no spatter at all. Why would this NOT be the expected defect in SAW?

Answer: SAW uses a submerged arc that is fully covered by flux, so spatter cannot be ejected into the open atmosphere

Because the arc is completely submerged under a flux blanket, molten droplets cannot escape into the atmosphere, making visible spatter essentially impossible in SAW.

A SAW weld on a pipe experiences transverse cracking in the heat-affected zone after PWHT. The most likely contributing factor is:

Answer: Strain-age embrittlement from PWHT at incorrect temperature for that alloy

PWHT at temperatures outside the qualified range for a specific alloy can cause strain-age embrittlement or temper embrittlement, leading to transverse HAZ cracking.

A SAW seam weld on a pressure vessel shell is found to have a wavy, irregular bead surface when inspected visually. The most probable cause is:

Answer: Flux contamination with oil or moisture causing gas evolution under the flux blanket

Contaminants in the flux produce gas bubbles under the molten slag that disturb the puddle surface, creating an irregular, pitted, or wavy bead appearance.

During SAW of duplex stainless steel, ferrite content in the weld metal is measured below the minimum specified. Which corrective action is most appropriate?

Answer: Reduce heat input by increasing travel speed and reducing wire feed

Excessive heat input in duplex stainless steels promotes austenite formation at the expense of ferrite; reducing heat input restores the target ferrite balance.

A SAW operator reports that the flux is not fully covering the weld pool, exposing the arc intermittently. The flux hopper is full. What is the most likely cause?

Answer: Flux delivery tube is clogged or the flux gate valve is partially blocked

A clogged flux delivery tube or restricted gate valve reduces flux flow, leaving the arc exposed and unshielded even when the hopper has adequate flux.