Unclean welding surface. Wrong electrode selection. Lack or absence of shielding gas. Mishandled or damaged shielding gas cylinder.
Among the commonly known welding defects, incomplete penetration and fusion, porosity and slag inclusions are the most common to affect welding strength.
Many different factors can cause weld quality issues: Low Weld Current - if sufficient temperatures aren't reached, the two metals may not be fused and the weld may fail. Poor Electrical Connection - loose cables or connections, contaminants, or oxidization can impede current flow, causing the weld to fail.
Any imperfections in the metals being joined together can result in joint failure. For instance, parts that were exposed to high heat might have distortions that make it harder for welders to achieve proper alignment.
Cracks can develop over time after the weld has been subjected to loads while in service. Tensile and fatigue loads; bending, twisting, or flexing; as well as hot and cold expansion and contraction all can occur long after welding, be it two days, two months, or even two years.
Electric shock is one of the most serious and immediate risks facing a welder. Electric shock can lead to severe injury or death, either from the shock itself or from a fall caused by the reaction to a shock.
Electric shock is the most serious hazard posed by welding and can result in serious injuries and fatalities, either through a direct shock or from a fall from height after a shock.
A good weld should be visually appealing, with a smooth and uniform weld bead that shows proper fusion and penetration. Bad welds, on the other hand, may contain defects like porosity, pinholes, or slag on the weld surface, which can compromise the strength and reliability of the weld.
Non-Destructive Weld Quality Testing
Ultrasonic inspection is used regularly to ensure weld integrity. This test is performed per customer specifications. Non-destructive testing also involves inspection of welded components by subjecting them to the required service conditions to determine suitability.
TIG welding is the hardest form of welding to learn for a variety of reasons. The process of TIG welding is slow and takes time to get used to as a beginner. A TIG welder requires a foot pedal to feed the electrode and control the variable amperage while maintaining a steady hand at the welding torch.
Wrong technique. "Push vs. pull, gun/electrode angle, travel speed, and arc length can all lead to problems," Leisner says. For example, if the rate of travel is too slow, the pool of weld metal will deposit an excess of weld metal.
If fatigue failure occurs in the throat of a fillet weld, simply increasing the weld size or changing to a full penetration weld will give an improvement.
Materials such as mild, low carbon and carbon-manganese steels, are considered to be very tolerant to heat input and may accept at least two or more re-weld operations. In the case of low alloy steels, re-welds will be governed by the heat-treated condition in which they were supplied.
Burns are the most common welding injury. They are caused by a lack of, or improper, personal protective equipment (PPE). Eye damage from exposure to arc rays is another common hazard.