Weld Quality and Acceptance of the Test Weldment
Visual acceptance comes first
Before a coupon is cut or bent, the finished weldment is examined visually: bead profile and uniformity, reinforcement height, undercut at the toes, overlap, surface porosity, spatter, arc strikes, crater condition and distortion. Cracks anywhere in the weld or heat-affected zone are rejectable at any size, and no code grants an allowance for them.
Destructive tests
Accepted welds are then sectioned. Typical tests are root and face bends (revealing lack of fusion, incomplete penetration and slag), a tensile or reduced-section tensile test, nick-break, and a macro etch to show the fusion line and root penetration. Criteria are numeric: bends must show no defect beyond the code limit, tensile specimens must reach a specified strength, and macro sections must show fusion to the root.
Rule of thumb
Defects that reduce effective throat, such as undercut, are judged against wall thickness; a common structural limit is 1/32 in (0.8 mm) on thinner material with larger allowances on thick sections, but always read the number in your code. Reinforcement is not penetration: a tall crown can hide incomplete fusion.
Worked example
A face bend opens a 3/16 in slag line on the tension surface. If the code permits no single indication over 1/8 in, the specimen fails. A retest on a new coupon is a code privilege, not a right.
Traps
Treating a good visual as a pass on the whole test, confusing undercut with overlap, believing a small crater crack is acceptable, and preparing specimens incorrectly so the wrong face is tested.