AWS AWS Distortion Control & Residual Stress 1 — Questions and Answers
Question 1: What is the primary cause of welding distortion?
- Excessive shielding gas flow
- Non-uniform heating and cooling creating unequal thermal expansion and contraction (Correct answer)
- Using too large a filler metal diameter
- Welding at high travel speeds only
Correct answer: Non-uniform heating and cooling creating unequal thermal expansion and contraction
Weld distortion occurs because the heated weld metal and HAZ expand and contract unevenly compared to the surrounding base metal.
Question 2: Which technique involves bending a workpiece in the opposite direction before welding to compensate for expected angular distortion?
- Back-step welding
- Peening
- Presetting (preset) (Correct answer)
- Balanced welding
Correct answer: Presetting (preset)
Presetting means intentionally bending the parts in the opposite direction before welding so that distortion brings them back to the desired shape.
Question 3: Which welding sequence technique reduces longitudinal shrinkage and distortion by dividing the weld into segments welded in the opposite direction to travel?
- Stringer bead technique
- Back-step welding (Correct answer)
- Cascade welding
- Block welding
Correct answer: Back-step welding
Back-step welding divides the weld into short segments deposited in the direction opposite to overall progression, balancing shrinkage stresses.
Question 4: What is 'angular distortion' in a butt-welded joint?
- Shrinkage along the length of the weld
- Rotation of the welded plates out of the original plane due to transverse shrinkage (Correct answer)
- Buckling of thin plate from compressive residual stresses
- Lengthwise bowing of the weldment
Correct answer: Rotation of the welded plates out of the original plane due to transverse shrinkage
Angular distortion is the rotation or tilting of the base metal plates out of their original plane, caused by unequal transverse shrinkage through the weld thickness.
Question 5: Which distortion control method involves applying heat to the opposite side of a distorted weld to straighten the part?
- Peening
- Vibratory stress relief
- Flame (heat) straightening (Correct answer)
- Mechanical restraint
Correct answer: Flame (heat) straightening
Flame straightening uses controlled application of heat to the convex side of a distorted part, which contracts on cooling and straightens the piece.
Question 6: Which approach most effectively minimizes distortion in a symmetrical butt joint with a double-V groove?
- Welding all passes on one side first, then the other
- Alternating weld passes on both sides of the joint (balanced welding) (Correct answer)
- Using the highest heat input possible
- Welding in the overhead position only
Correct answer: Alternating weld passes on both sides of the joint (balanced welding)
Balanced welding — alternating passes on both sides of a double-V — keeps shrinkage forces symmetric, canceling angular distortion.
AWS AWS Distortion Control & Residual Stress 1
What is the primary cause of welding distortion?