456A SMAW (Shielded Metal Arc Welding) 2 — Questions and Answers
Question 1: What is the purpose of the flux coating on a SMAW electrode?
- Provides shielding gas and slag to protect the weld pool, stabilizes the arc, and adds alloying elements (Correct answer)
- Only to improve electrical conductivity
- To increase deposition rate without affecting weld quality
- To prevent the electrode from overheating
Correct answer: Provides shielding gas and slag to protect the weld pool, stabilizes the arc, and adds alloying elements
The flux coating on a SMAW electrode serves multiple functions: it generates shielding gases (CO2, CO) to protect the molten pool from atmospheric contamination, forms slag to protect the solidifying weld, stabilizes the arc, and can introduce alloying elements into the weld metal.
Question 2: When welding with E7018 electrodes, what defect is most likely if the electrodes have absorbed moisture?
- Hydrogen-induced cracking (underbead cracking) (Correct answer)
- Incomplete fusion
- Undercut
- Overlap
Correct answer: Hydrogen-induced cracking (underbead cracking)
Moisture in low-hydrogen electrodes decomposes in the arc and introduces hydrogen into the weld metal. This hydrogen can diffuse to stress concentration points and cause hydrogen-induced cracking (HIC), also known as cold cracking or underbead cracking.
Question 3: What is the correct technique for striking an arc with a SMAW electrode?
- Scratch or tap the electrode on the base metal and quickly establish the correct arc length (Correct answer)
- Hold the electrode stationary against the base metal until the arc establishes itself
- Strike the arc away from the joint and move it back to the start position
- Use a high-frequency arc starter at all times
Correct answer: Scratch or tap the electrode on the base metal and quickly establish the correct arc length
The scratch or tap method is used to initiate the SMAW arc. The electrode is moved across the base metal like striking a match (scratch) or briefly touched and lifted (tap). The arc length should be established quickly to prevent electrode sticking.
Question 4: What does arc blow refer to in SMAW welding?
- Deflection of the arc from its intended path due to magnetic fields (Correct answer)
- Excessive spatter caused by high amperage
- Loss of arc due to contaminated base metal
- Overheating of the electrode
Correct answer: Deflection of the arc from its intended path due to magnetic fields
Arc blow is the deflection of the welding arc caused by magnetic fields in the workpiece. It is most common when welding DC on ferromagnetic materials near the ends of joints or in corners. It can cause poor fusion and uneven bead profiles.
Question 5: Which of the following is a remedy for arc blow during SMAW?
- Switch from DC to AC current (Correct answer)
- Increase the amperage
- Use a shorter electrode
- Decrease preheat temperature
Correct answer: Switch from DC to AC current
Switching from DC to AC eliminates arc blow because AC current alternates direction, preventing the buildup of a sustained magnetic field in the workpiece. Other remedies include repositioning the work lead, angling the electrode, or welding toward the work lead.
Question 6: What is the recommended arc length for most SMAW electrodes?
- Approximately equal to the diameter of the electrode core wire (Correct answer)
- Twice the diameter of the electrode
- As short as possible, nearly touching the base metal
- 10–15 mm to ensure adequate shielding
Correct answer: Approximately equal to the diameter of the electrode core wire
The correct arc length for SMAW is approximately equal to the diameter of the electrode core wire. Too short an arc causes sticking; too long an arc causes excessive spatter, porosity, and loss of penetration.
456A SMAW (Shielded Metal Arc Welding) 2
What is the purpose of the flux coating on a SMAW electrode?