Usually, most of the defects in welding are caused by incorrect welding procedures. Fortunately, welding defects are easy to fix once the cause is discovered.

In sheet metal fabrication, porosity, overlap, distortion, and lack of fusion are the most common welding defects. These defects are easily detected and can be prevented in future applications.

Let\’s look at each defect closely and how can you prevent them:

1. Porosity
   Put merely, porosity changes to gas bubbles in the welded surface. This happens when shielding gas gets trapped within the weld and releases after the weld hardens. This gas leaves tiny holes in the weld that are incredibly destructive in Metal Inert Gas (MIG) or stick welds.

Weld porosity can lead to internal and external cracks, as well as weakened weld joints. To prevent this defect:

● Specify similar metal types if using multiple forms
● Use x-rays and ultrasound technology to check the welded metal for holes

1. Overlap
   The overlap is characterised as an excess of weld metal beyond the weld root. This happens when molten metal runs over the surface of the base material and cools without fusing. Weld overlap is common in fillet or butt welds, frequent weld types in sheet metal fabrication.

It is caused by insufficient heat during the welding, negligible fusion of the metal, or concentrated stress under load. To prevent these defects:

● Use a metal type and grade that is more agreeable with high-heat conditions
● Choose skilled and experienced welders

1. Distortion
   In welding, distortion is due to excessive heat warping the base metal. This usually takes place in thinner gauge sheet metals because they lack the surface area to diffuse heat. It can also occur while creating longer welds, as metal is exposed to heat for a long time.

The warped metal due to distortion disrupts the aesthetics of the metal and is not structurally sound.

To prevent weld distortion:

● Avoid stainless steel as it shifts position during a weld
● Use a more weldable metal type and grade to reduce the number of passes

1. Lack of Fusion:

When the base metal and the weld metal do not entirely adhere together, there is a lack of fusion. This is commonly caused by improper welding angle, excessive speed, or insufficient arc length.
Lack of fusion is consequential as the weld connection will not be strong or durable. To prevent this defect:

● Use a thinner piece of metal

KP Fabrication and Welding are in the welding business for years. We have highly skilled and experienced experts that are well aware of these effects and know how to work around them, without compromising on your final product.

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