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How to Check Welds on Steel

All welds are visually inspected to determine whether they have been adequately placed and have the necessary strength to hold steel together. While it is technically possible to perform weld inspection with specialized diagnostic equipment, this is generally not necessary in anything but a welding certification testing situation. Basic welding allows for quick inspections so that work can either progress or be redone in a quick and efficient manner.

Instructions

1

Look at the back of any type of weld after it has cooled, but before the part is cleaned. You should see discoloration on the back of the steel that has been welded that ranges in color from dark blue to nearly brown. If this area is uniformly smooth and colored, the weld penetration, or how deeply the weld penetrated the steel, was successful. If there is a hole in the metal, this is called weld burn-through, and is a weld failure. On the other hand, the appearance of small bumps within the colored region are called weld melt-through. These are acceptable in most welding situations.

2

Inspect the weld fillet in steel welded at angles to each other. This is the actual deposited weld filler that builds up during the welding process. It should be uniform and attractive, with edges smoothed into the surrounding metal rather than clumped up on top of one another. In addition to this, the fillet should not exhibit any signs of cavities in the filler metal. This is indicative of poor weld quality, and the part should be remade.

3

Measure spot welds with a metal ruler to determine their strength. The spot weld should be no greater than 3/8 inch in diameter, and no more than 1/32 inch high. The back of the spot weld should exhibit a round blue coloration and a tiny dimple in the exact center of the weld. Evidence of holes in the steel indicate a poor quality weld.

4

Inspect butt welds to make certain that they exhibit the proper coloration on the back of the welded steel. If they have the right coloration, inspect the weld itself. The weld should not exceed 3/16 inch in width, and should be no higher than 1/16 inch above the steel being welded. In addition, the weld should completely cover any gap between the two pieces of steel being welded. A hole or a gap indicates a poor quality weld, and the part should be remade.

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