Question

Which of the following causes excessive splatter, fiery arc, spalling of flux coating and porosity in weld metal?

• A. Low voltage
• B. Loose electrical connection
• C. Defective welding machine
• D. Moisture absorption by the electrode

Hint:

Moisture is the enemy of high-quality welds, especially in Shielded Metal Arc Welding (SMAW). It's the source of hydrogen, which leads to porosity and cold cracking. Always store electrodes, particularly low-hydrogen types, in a dry oven as per the manufacturer's recommendations.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
The question describes a collection of welding problems that often occur together: an unstable arc, spatter, flux breaking off, and porosity. This points to a common root cause related to the welding consumable, specifically the electrode's flux coating.

Step 2: Detailed Explanation:
The presence of moisture (H\(_2\)O) in the flux coating of a welding electrode (especially low-hydrogen electrodes) has severe negative consequences:

• Fiery Arc and Spatter: The intense heat of the arc (\(\gt \) 5000\(^\circ\)C) dissociates the water molecules into hydrogen (H) and oxygen (O) gases. These gases expand rapidly and violently, disrupting the smooth transfer of metal droplets across the arc. This creates a "fiery," unstable arc and causes excessive spatter.

• Spalling of Flux Coating: The rapid conversion of trapped water into steam within the flux coating can create enough pressure to cause the coating to crack and flake off, or "spall."

• Porosity: The hydrogen gas generated is highly soluble in molten steel but its solubility drops sharply as the metal solidifies. If the hydrogen doesn't have time to escape before the weld pool freezes, it gets trapped and forms gas pockets, known as porosity.
The other options cause different problems:

• (A) Low voltage typically results in a stubby arc that is hard to maintain and can lead to poor fusion.

• (B) A loose connection causes an erratic, intermittent arc.

• (C) A defective machine can cause a wide range of issues, but the specific combination listed is the classic signature of moisture.

Step 3: Final Answer:
Moisture absorption by the electrode flux is the primary cause for the combination of defects listed, as the water decomposes in the arc, leading to gas expansion (spatter, arc instability) and hydrogen entrapment (porosity).