Weld Defects and Inspection Questions and Answers

Answer: A

Ultrasonic testing is used to find cracks below the surface.

A probe sends high-frequency sound waves into the material. A crack, void or inclusion inside reflects part of the wave back, and the echo's timing shows how deep the flaw lies. It is a non-destructive test, widely used on welds, castings, forgings and rails.

Yield strength and ultimate tensile strength are measured destructively, by pulling a specimen in a tensile test. Hardness is measured by indentation tests such as Brinell, Rockwell or Vickers.

Answer: C

Weld spatter is a welding defect.

Spatter is the droplets of molten metal thrown out of the arc that stick to the surface around the weld. It wastes filler metal and spoils the finish, and is usually caused by too high a current, too long an arc, wrong polarity or damp electrodes.

It is not a flux or an electrode coating, though a poor coating can increase spatter, and it is not a test; it is something inspection looks for.

Answer: B

A guided bend test determines ductility.

A strip cut across the weld is bent round a former of set radius, usually through 180°, with the weld at the bend. The outer surface is stretched heavily; if the weld and the heat-affected zone can bend without cracking or opening up, they have adequate ductility and soundness. Face, root and side bend tests check different surfaces.

Tensile strength and percentage of elongation are measured in a tensile test, and impact value in a Charpy or Izod notched-bar test.

Answer: B

Incomplete fusion is caused by very low current.

With too little current the arc does not supply enough heat to melt the edges of the parent metal properly. The weld metal then lies on the surface or against the side walls without fusing into them, leaving unfused regions that weaken the joint.

Very high current tends to cause undercut, burn-through and spatter rather than lack of fusion. A wide bead is not in itself a cause. Since low current is a recognised cause, 'None of the above' is wrong.