AWS Submerged Arc Welding (SAW) 5 — Questions and Answers
Question 1: In SAW, what is a 'fused flux' and how does it differ from an 'agglomerated flux'?
- Fused flux is melted and solidified into glassy granules; agglomerated flux is bonded with chemicals at low temperature (Correct answer)
- Fused flux contains alloying elements; agglomerated flux does not
- Fused flux is used only for stainless steel; agglomerated flux for carbon steel
- Fused flux requires higher voltage; agglomerated flux requires lower voltage
Correct answer: Fused flux is melted and solidified into glassy granules; agglomerated flux is bonded with chemicals at low temperature
Fused fluxes are manufactured by melting raw materials and crushing the solidified glass, while agglomerated fluxes bond ingredients with binders at low temperature allowing alloy additions.
Question 2: What is the purpose of 'run-on' and 'run-off' tabs in SAW?
- To preheat the joint before welding begins
- To provide a location for arc starting and stopping outside the joint to avoid defects at weld ends (Correct answer)
- To support the flux during welding of curved joints
- To allow for thermal expansion of the base metal
Correct answer: To provide a location for arc starting and stopping outside the joint to avoid defects at weld ends
Run-on and run-off tabs extend the weld start and stop beyond the actual joint, ensuring full fusion and avoiding crater cracks or lack of fusion at the ends.
Question 3: What does 'basicity index' indicate about a SAW flux?
- The flux's ability to remove phosphorus from the weld pool
- A measure of the flux's acid-base chemistry affecting notch toughness and oxygen content of the weld (Correct answer)
- The percentage of iron oxide in the flux
- The flux's resistance to moisture absorption
Correct answer: A measure of the flux's acid-base chemistry affecting notch toughness and oxygen content of the weld
Basicity index (BI) measures the ratio of basic to acidic oxides in the flux; higher BI generally produces lower weld oxygen content and better notch toughness.
Question 4: Which welding position is SAW best suited for and why?
- Vertical (3G) because the flux provides extra support
- Flat (1G/1F) because gravity keeps the molten flux and weld pool in place (Correct answer)
- Overhead (4G) because the flux provides complete shielding
- Horizontal (2G) because travel speed is maximized
Correct answer: Flat (1G/1F) because gravity keeps the molten flux and weld pool in place
SAW is primarily used in the flat position because the molten flux and large weld pool must be supported by gravity to prevent spillage and ensure proper coverage.
Question 5: What is 'melt-off rate' in SAW and what primarily controls it?
- The rate at which flux melts, controlled by arc voltage
- The rate at which electrode wire is consumed, primarily controlled by welding current (Correct answer)
- The rate at which base metal melts, controlled by travel speed
- The rate of slag formation, controlled by flux type
Correct answer: The rate at which electrode wire is consumed, primarily controlled by welding current
Melt-off rate is the weight of electrode consumed per unit time, and it is primarily controlled by welding current (amperage).
Question 6: When using AWS A5.17 classification, what does the 'F' prefix in a flux designation (e.g., F7A2) indicate?
- The flux is fused type
- The flux classification, with the number indicating minimum tensile strength of weld metal in 10 ksi increments (Correct answer)
- The flux is suitable for flat position only
- The flux contains fluoride compounds
Correct answer: The flux classification, with the number indicating minimum tensile strength of weld metal in 10 ksi increments
In AWS A5.17, 'F' stands for flux, and the following number (e.g., 7) indicates the minimum tensile strength of the weld metal (70 ksi) when used with the classified electrode.
Question 7: What is 'arc blow' in SAW and which condition most commonly causes it?
- Excessive spatter caused by high voltage
- Magnetic deflection of the arc due to DC welding near the end of a joint or at geometric changes (Correct answer)
- Arc instability caused by wet flux
- Porosity caused by insufficient flux coverage
Correct answer: Magnetic deflection of the arc due to DC welding near the end of a joint or at geometric changes
Arc blow occurs when stray magnetic fields deflect the DC welding arc, most commonly near the ends of a joint or at changes in joint geometry.
AWS Submerged Arc Welding (SAW) 5
In SAW, what is a 'fused flux' and how does it differ from an 'agglomerated flux'?