AWS Welding Techniques 1 — Questions and Answers
Question 1: Which welding process uses a continuously fed wire and shielding gas?
- TIG Welding
- Stick Welding
- MIG Welding (Correct answer)
- Oxy-Acetylene Welding
Correct answer: MIG Welding
MIG welding, or Gas Metal Arc Welding (GMAW), uses a continuously fed wire electrode that is consumed during the welding process. A shielding gas (typically argon, CO2, or a mix) is simultaneously fed to protect the molten weld pool from atmospheric contamination, making it efficient and versatile for various metals and applications.
Question 2: Which welding process does not require external shielding gas?
- TIG Welding
- MIG Welding
- Stick Welding (Correct answer)
- Plasma Cutting
Correct answer: Stick Welding
Stick welding, or Shielded Metal Arc Welding (SMAW), uses a consumable electrode coated with flux. When the electrode melts, the flux coating decomposes, creating a gaseous shield around the weld pool and forming a protective slag layer. This internal shielding mechanism means no external shielding gas cylinder is required, making it highly portable.
Question 3: What is the main advantage of TIG welding?
- High deposition rate
- Suitable for thick steel only
- Highly portable
- Produces high-quality precise welds (Correct answer)
Correct answer: Produces high-quality precise welds
TIG welding (Gas Tungsten Arc Welding, GTAW) is renowned for its ability to produce extremely clean, high-quality, and precise welds. It uses a non-consumable tungsten electrode and a separate filler rod, allowing for excellent control over the heat input and weld puddle. This makes it ideal for critical applications and thin materials where aesthetics and integrity are paramount.
Question 4: What does the flux coating on a stick electrode do?
- Increases the electrode temperature
- Acts as a filler metal
- Creates shielding gas and slag (Correct answer)
- Conducts electricity more efficiently
Correct answer: Creates shielding gas and slag
The flux coating on a stick electrode serves multiple crucial functions. As it burns, it produces a shielding gas that protects the molten weld pool from atmospheric oxygen and nitrogen. It also forms a protective slag layer over the cooling weld, which further shields it and helps shape the bead, before being chipped away after solidification.
Question 5: Which welding process is best for welding aluminum?
- Stick Welding
- TIG Welding (Correct answer)
- Flux Core Welding
- Submerged Arc Welding
Correct answer: TIG Welding
TIG welding is generally considered the best process for welding aluminum due to its ability to produce very clean and high-quality welds. The use of AC current in TIG welding helps to break up the tenacious aluminum oxide layer, which is crucial for achieving good penetration and a strong, defect-free weld. This precision is vital for aluminum's properties.
Question 6: Which component is essential for Gas Metal Arc Welding (GMAW)?
- Chipping hammer
- Shielding gas (Correct answer)
- Foot pedal
- Filler rod
Correct answer: Shielding gas
Gas Metal Arc Welding (GMAW), commonly known as MIG welding, relies heavily on shielding gas to protect the molten weld pool from atmospheric contamination. Without shielding gas, oxygen and nitrogen from the air would react with the molten metal, leading to porosity, brittleness, and a weak weld. It is a critical component for weld integrity.
Question 7: What type of current is typically used in Stick Welding (SMAW)?
- AC only
- DC only
- DC or AC (Correct answer)
- Neither AC nor DC
Correct answer: DC or AC
Stick welding (SMAW) can be performed using either Direct Current (DC) or Alternating Current (AC). The choice of current type depends on the specific electrode being used and the material being welded. Many electrodes are designed for either AC or DC, while some are versatile for both, offering flexibility to the welder in various environments.
Question 8: What is porosity in a weld caused by?
- Excess heat
- Poor shielding gas coverage (Correct answer)
- Too much filler rod
- Excessive arc length
Correct answer: Poor shielding gas coverage
Porosity in a weld occurs when gases become trapped within the solidifying weld metal, forming small voids. This often happens due to insufficient or improper shielding gas coverage, which fails to protect the molten weld pool from atmospheric contaminants like oxygen and nitrogen. These absorbed gases are then released as bubbles, leading to these internal cavities.
Question 9: What does the term 'undercut' refer to in welding?
- A type of electrode
- An arc start technique
- Groove that weakens the weld joint (Correct answer)
- Weld cooling method
Correct answer: Groove that weakens the weld joint
Undercut refers to a groove melted into the base metal adjacent to the toe or root of a weld, which is left unfilled by weld metal. This defect reduces the thickness of the base metal, creating a stress concentration point that significantly weakens the weld joint. It can lead to premature failure under load.
