Nick-break

Nick break testing is another simple process that lends itself to learning welding, due to its speed and very low cost. It is also used in production runs, where quality is monitored at intervals throughout production.

The principle behind it is simple, you take a sample piece, partially cut through it, then break the remainder off. This allows you to ‘see inside the weld’.

Various defects can be seen by visual inspection if present in the sample piece. Faults such as lack of fusion, porosity, slag inclusions etc can be readily seen.

This example is for a fillet weld, but the process is quite similar for a butt welded joint. You would cut a narrow strip, and ‘nick’ into it from the top and bottom edges (not faces), then break over two blocks.

Preparing

Firstly a sample piece is selected, size depends upon material being tested. An example of 8mm plate, welded in a 'T', a 50mm wide test piece would be ideal.

Often the same test piece may have a macro etch carried out prior. Once the portion is cut, it then requires a saw kerf, in-line with the length of the weld. This only need be 3mm deep or so. A hacksaw or thin cutting disc is ideal.

Breaking

On a fillet weld, the sample would be pressed or hammered so that the kerf will close up when struck. If the weld is good quality, this may take some force.

Results

Should one part of the test piece come away with little effort, this may well be down to poor welding, possibly lack of penetration or sidewall fusion. Either down to incorrect welding parameters or poor technique.

Once the sample is in two, you will also be able to check for inclusions and porosity within the weld.

Anything other than a clean even straight break should be checked out further.