Welding Techniques & Process Control Flashcards

Which technique ensures uniform weld bead formation in SAW?

Answer: Constant travel speed with proper alignment

To ensure uniform weld bead formation in SAW, it is crucial to maintain a constant travel speed and proper alignment of the electrode with the joint. Consistent speed ensures a steady heat input and deposition rate, while correct alignment ensures the weld metal is deposited evenly within the joint. This leads to a smooth, uniform bead with consistent penetration and profile.

What effect does excessive arc voltage have on SAW welds?

Answer: Results in undercut and excessive spatter

Excessive arc voltage in SAW creates a longer, wider arc, which can lead to several weld defects. It often results in undercut, where the base metal along the toe of the weld is melted away without being filled by weld metal, and excessive spatter, which is molten metal expelled from the weld pool. It can also cause a wider, flatter bead with reduced penetration.

Why is it important to control heat input in SAW?

Answer: To manage weld quality and prevent defects

Controlling heat input in SAW is critical because it directly influences the metallurgical properties and overall quality of the weld. Excessive heat input can lead to grain coarsening in the heat-affected zone (HAZ), increased distortion, and reduced mechanical properties, while insufficient heat input can cause lack of fusion and inadequate penetration. Proper heat input management prevents these defects and ensures the weld meets specified strength and toughness requirements.

Which defect is caused by poor flux coverage during SAW?

Answer: Porosity

Poor flux coverage in SAW means the molten weld pool is inadequately shielded from the surrounding atmosphere. This allows atmospheric gases like oxygen and nitrogen to dissolve into the molten metal, and as the weld solidifies, these trapped gases form small voids or bubbles. This results in porosity, a common weld defect that weakens the joint.

What adjustment improves fusion when welding thicker materials?

Answer: Increase amperage

When welding thicker materials, more heat is required to achieve proper fusion and penetration into the base metal. Increasing the amperage (welding current) directly increases the heat input at the arc, leading to deeper melting and better fusion with the thicker material. This ensures a strong and sound weld that fully penetrates the joint.

What is the result of incorrect travel angle during SAW?

Answer: Uneven bead and lack of fusion

The travel angle, or electrode angle, in SAW significantly affects the distribution of heat and the flow of molten metal. An incorrect travel angle can lead to an uneven weld bead profile, where one side might have insufficient fusion or an irregular shape. It can also cause lack of fusion, especially on the leading or trailing edge, compromising the weld's integrity and strength.

What should be done to prevent slag inclusions in SAW welds?

Answer: Ensure flux coverage and interpass cleaning

Slag inclusions occur when non-metallic slag material becomes trapped within the solidified weld metal. To prevent this, it's crucial to ensure adequate flux coverage during welding, which helps float the slag to the surface. Additionally, thorough interpass cleaning, which involves removing all slag from previous weld passes before depositing the next, is essential to prevent it from being entrapped.

Why is consistent wire feed rate critical in SAW?

Answer: Stabilizes arc and bead formation

A consistent wire feed rate is critical in SAW because it directly controls the welding current and, consequently, the heat input and arc length when using a constant voltage power source. Any fluctuation in wire feed rate can destabilize the arc, leading to inconsistent heat input. This results in an uneven weld bead, variable penetration, and potential defects.

What does excessive travel speed in SAW typically cause?

Answer: Lack of fusion and narrow beads

Excessive travel speed in SAW reduces the heat input per unit length of the weld, meaning the molten metal has less time to properly fuse with the base material. This often results in lack of fusion, where the weld metal doesn't fully bond with the base metal, and narrow, often convex, weld beads with insufficient penetration, compromising weld strength.