AWS Submerged Arc Welding (SAW) 2 — Questions and Answers
Question 1: What does the term 'flux basicity index' measure in Submerged Arc Welding?
- The moisture content of the flux
- The ratio of basic to acidic oxide components in the flux (Correct answer)
- The melting point of the flux
- The particle size distribution of the flux granules
Correct answer: The ratio of basic to acidic oxide components in the flux
The basicity index (BI) is calculated from the ratio of basic to acidic oxide constituents in the flux and indicates the flux's ability to refine the weld metal and control impurities.
Question 2: In SAW, increasing amperage (wire feed speed) primarily affects which weld characteristic?
- Bead width
- Depth of penetration (Correct answer)
- Arc voltage
- Flux consumption rate
Correct answer: Depth of penetration
Increasing amperage increases the heat input and current density at the wire tip, which primarily drives deeper penetration into the base metal.
Question 3: Which of the following base metals is NOT commonly welded using the SAW process?
- Low-carbon structural steel
- Stainless steel
- Aluminum alloys (Correct answer)
- Nickel alloys
Correct answer: Aluminum alloys
Aluminum alloys are not suited for SAW because appropriate flux systems for aluminum SAW are not commercially practical, and the process is not specified in standard AWS aluminum welding codes.
Question 4: Flux for Submerged Arc Welding must be properly dried before use primarily to prevent:
- Excessive slag adhesion
- Porosity and hydrogen-induced cracking (Correct answer)
- Burn-through on thin materials
- Spattering of weld metal
Correct answer: Porosity and hydrogen-induced cracking
Moisture in SAW flux decomposes at the arc to produce hydrogen, which can cause porosity and hydrogen-induced (cold) cracking, particularly in higher-strength steels.
Question 5: What is the purpose of using a copper backing bar in SAW root pass welding?
- To preheat the joint
- To prevent burn-through and support the weld pool on single-sided welds (Correct answer)
- To act as a flux retainer
- To reduce distortion by clamping the plates
Correct answer: To prevent burn-through and support the weld pool on single-sided welds
A copper backing bar supports the molten weld pool on single-sided groove welds, prevents burn-through, and helps form a smooth root bead without requiring back-gouging.
Question 6: In tandem SAW, two wire electrodes are used in a single weld puddle. What is the primary benefit?
- Improved weld metal toughness
- Significantly increased deposition rates and travel speeds (Correct answer)
- Better penetration control on thin plate
- Reduced distortion compared to single wire SAW
Correct answer: Significantly increased deposition rates and travel speeds
Tandem SAW uses two electrodes in the same weld pool to roughly double the deposition rate and travel speed compared to single-wire SAW, increasing productivity on heavy fabrications.
Question 7: According to AWS A5.17, the flux classification designation 'F7A2' indicates:
- Minimum 70 ksi tensile strength, as-welded condition, Charpy V-notch impact at -20°F (Correct answer)
- 70,000 psi yield strength flux, Type A, second revision
- Flux heat input of 70 kJ/in, annealed, second pass
- F-number 7, acidic flux, Grade 2 porosity resistance
Correct answer: Minimum 70 ksi tensile strength, as-welded condition, Charpy V-notch impact at -20°F
In AWS A5.17, 'F7' indicates the weld metal tensile strength (70 ksi min), 'A' indicates as-welded condition, and '2' indicates minimum Charpy V-notch impact value at -20°F.
AWS Submerged Arc Welding (SAW) 2
What does the term 'flux basicity index' measure in Submerged Arc Welding?