MIG Issues And How To Correct Them


Over the years, MIG welding processes have been improved with better welding equipment. With the more advanced equipment available today, it is possible for many operators to forget essential steps when performing the weld. Here are some common welding problems and some simple solutions.


In MIG welding a common unwanted side effect is spatter. These are droplets of molten material that are produced in the welding arc. Spatter happens when welding currents or voltages are set too high or if there isn’t enough gas shielding. In order to avoid spatter, reducing the welding current and arc length (voltage) can minimize spatter. Checking the shielding gas type and flow rate is always a good idea if spatter is present as well as cleaning the gas nozzle. Increasing the tip-to-plate angle will also help to reduce spatter.


Porosity is caused when gas bubbles are trapped in the molten weld puddle as it solidifies. Foreign materials on the surface can be a large contributor to porosity formation, these include moisture, oils, paint, heavy mill scale or rust on the material surface to be welded, lack of proper gas shielding, or when small gaps are present between two surfaces that can trap atmospheric air. To avoid porosity in a weld, the welder should make sure the welding area is clean of foreign materials and wiped clean. It would also be a good idea to check the shielding gas type and flow rates and to clean the gas nozzle of the welding gun. Making sure two pieces of material to be welded together are fitted tightly can help prevent porosity as well.


Undercuts occur when the arc voltage is too high or when the arc is too long which cause the parent material to be melted away and not filled. It can also happen if there is incorrect weld wire selection or the tip-to-plate angle used for welding is wrong. It is also important to check for proper technique concerning the manipulation of the weld wire used. It is very important when using the weave because a weave that is too large may not allow the molten puddle to fill in correctly. In this instance slowing down the travel speed can help solve the issue.

Heat Deformation:

Heat Deformation happens during the cooling process of the welded parts. If the welding sequence is not correct for the intended parts, if there are too many weld beads, or poor fit-up of the parts before and during welding, the part may be deformed from heat. Solutions to avoid deformation are welding from the center out on the parts, to weld from both sides of the joint or to sequence the welds in a manner that allows proper heating and cooling of the parts.


In any type of welding, a crack is always considered a defect. It can be dangerous because small cracks have the potential to grow over time and cause a weld failure. It is necessary to spend time grinding, cleaning, filing or deburring the edges of the plates so they easily fit together to help to avoid cracks. It’s a good idea to preheat and sometimes post heat treat thicker materials to help reduce the possibility of cracks developing by allowing the material to heat and cool more evenly.

Fusion and Penetration:

Incomplete fusion occurs when the weld fails to melt together on one side of the weld to the parent material. Incomplete penetration occurs when both sides root region of the joint are unfused. These issues are more common in processes such as MIG, FCAW and SAW where the weld metal is deposited as the arc consumes the weld wire (electrode). Solving this issue includes the use of a wider root gap and a weld wire diameter size that is approximately the gap width of the root. Lowering travel speed and weaving between the plate edges can help to solve these issues as well.

Proper techniques as well as correctly preparing materials to be welded can head off most of these issues. Always research the material to be welded and gain as much knowledge as possible prior to starting a project. By becoming more diligent upfront, most problems associated with welding can be eliminated prior to striking the first arc.

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