AWS AWS Joint Design & Preparation 4 — Questions and Answers
Question 1: What is the purpose of a backing bar in a groove weld joint?
- To support the molten weld pool and ensure complete joint penetration (Correct answer)
- To increase the travel speed of the welding process
- To reduce the preheat temperature requirement
- To act as a flux carrier in submerged arc welding only
Correct answer: To support the molten weld pool and ensure complete joint penetration
A backing bar supports the molten weld pool during root pass welding, ensuring complete joint penetration without burn-through.
Question 2: When a T-joint is designed with a fillet weld on both sides, what is the primary benefit compared to a single-sided fillet weld?
- It reduces angular distortion and increases load-carrying capacity (Correct answer)
- It eliminates the need for preheat
- It allows the use of lower-strength filler metal
- It removes the requirement for a root opening
Correct answer: It reduces angular distortion and increases load-carrying capacity
Double-sided fillet welds balance thermal stresses, reducing angular distortion while doubling the effective throat area for higher load capacity.
Question 3: According to AWS standards, what does the term 'effective throat' refer to in a fillet weld?
- The theoretical distance from the root to the hypotenuse of the largest right triangle inscribed in the fillet cross-section (Correct answer)
- The actual measured depth of fusion into the base metal
- The distance from the weld face to the root of the joint
- The total leg length of the fillet weld
Correct answer: The theoretical distance from the root to the hypotenuse of the largest right triangle inscribed in the fillet cross-section
Effective throat is the theoretical distance from the root to the weld face hypotenuse, used to calculate the load-bearing capacity of fillet welds.
Question 4: Which joint design is most susceptible to lamellar tearing?
- T-joints and corner joints with through-thickness loading on thick plates (Correct answer)
- Butt joints with complete joint penetration
- Lap joints with equal plate thicknesses
- Edge joints with thin sheet metal
Correct answer: T-joints and corner joints with through-thickness loading on thick plates
T-joints and corner joints subject thick base metal to through-thickness stress, which can cause lamellar tearing along sulfide inclusions in the steel.
Question 5: What is the function of a weld access hole (also called a rat hole or cope hole) in structural steel connections?
- To allow the welder access to make a continuous weld past a flange-web intersection (Correct answer)
- To reduce the weight of the steel member
- To provide ventilation for shielding gas during GMAW
- To serve as a drain hole to prevent moisture accumulation
Correct answer: To allow the welder access to make a continuous weld past a flange-web intersection
Weld access holes are cut into the web at beam-to-column connections to allow full-length continuous welds on flanges without interruption at the web.
Question 6: In AWS D1.1, what is the minimum preheat temperature requirement for ASTM A36 steel with a thickness greater than 1-1/2 inches when using SMAW?
- 150°F (65°C) (Correct answer)
- 50°F (10°C)
- 300°F (150°C)
- No preheat is required for A36 steel
Correct answer: 150°F (65°C)
AWS D1.1 Table 3.2 requires a minimum preheat of 150°F for A36 steel over 1-1/2 inch thick to prevent hydrogen-induced cracking.
Question 7: Which groove weld preparation is typically preferred for joining thick plates (over 3/4 inch) from one side only when back gouging is not possible?
- Single-V groove with a backing strip (Correct answer)
- Square groove weld
- Single-bevel groove without backing
- J-groove from one side only
Correct answer: Single-V groove with a backing strip
A single-V groove with a backing strip ensures complete joint penetration from one side when back gouging or access to the backside is not feasible.
AWS AWS Joint Design & Preparation 4
What is the purpose of a backing bar in a groove weld joint?