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Cracking Many situations can cause cracking in welds from materials to consumables to welder technique etc. etc. Each incident needs to be investigated and the probable cause identified. Lack of Fusion This fault can apply to any process but is a particular problem with the MIG/MAG process. It can be lack of side wall fusion, interrun fusion or root fusion. The cause can be several things but it is usually either that the plant is not set correctly or the welder is employing a poor technique. Lack of Penetration On butt welds this can have several causes. Probably the most common is having insufficient gap between the parts to be jointed. Other causes could be root face too big, current too low and lack of welders skill. Very often a combination of these is the cause of the problem. Overlap Occurs when weld metal runs onto the surface of the material being welded but does not fuse to it. Caused mainly by poor welder technique. Over Penetration Can be caused by current too high, gap too large or root face too small but very often it is lack of skill. Porosity Often welds will fail because of porosity which means that the weld has holes in it, so it appears very much like an ‘Aero’ chocolate bar. There are several causes of this fault and the reasons for it may depend on cleanliness, environment, equipment, welder technique or a combination of these. Spatter Can be caused by incorrect setting of welding plant and also by ‘arc blow’ when using Direct Current. Undercut A very common problem particularly on the vertical leg of a fillet weld or on vertical upward or overhead welding. Generally caused by poor welder technique or current too high. Wormholes Caused by trapped gas trying to escape from the molten metal. Causes as for porosity.
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