Welding porosity is a common defect in the welding process, referring to gas holes formed in the weld metal. These porosity not only reduce the strength and quality of the weld but may even lead to leakage or fracture of the welded structure. Therefore, in-depth understanding of the causes, effects, and solutions to welding porosity is crucial for improving welding techniques and ensuring welding quality.

Weld metal surface porosity in a dispersed form and weld metal internal porosity in a dense form.

This article provides a detailed analysis of all aspects of welding porosity to help welding engineers and technicians better understand and address this issue.

In welding production, porosity often occurs in welds, requiring extensive repairs. Generally, the areas with porosity are removed by gouging or grinding, and then welding repairs are carried out, followed by inspection using non-destructive testing (NDT) methods.

Porosity is defined as a cavity-type discontinuity defect caused by gases precipitated due to a decrease in solubility during the solidification of weld metal. These gases fail to escape before solidification ends, resulting in residual gases on the surface or inside the weld metal.

For dispersed porosity on the surface of weld metal and dense porosity inside the weld metal, mwelding technology welding engineers provide the causes of porosity and corresponding solutions.

Causes and Countermeasures of Porosity in Welds:

1、High hydrogen, nitrogen, and oxygen content in shielding gas?

Countermeasure: Use low-hydrogen welding processes; increase deoxidizers in the filler metal; increase shielding gas flow rate.

2、Too fast solidification speed?

Countermeasure: Preheat before welding or increase heat input.

3、Contaminated base material?

Countermeasure: Clean the joint surface and adjacent areas.

4、Contaminated welding wire?

Countermeasure: Use specially packaged filler welding wire and store it in a clean area.

5、Incorrect arc length, welding current, or operation?

Countermeasure: Improve welding specifications or techniques.

6、Zinc volatilization from brass products?

Countermeasure: Use copper-silicon filler metal; reduce heat input.

7、Galvanized steel?

Countermeasure: Remove the zinc coating before welding or preheat to facilitate zinc volatilization during welding.

8、Moisture on the joint surface or electrode flux?

Countermeasure: Bake and store electrodes according to proper procedures and preheat the base material.

9、High sulfur content in the base material?

Countermeasure: Use basic welding materials.

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(Figure 4) Causes, Effects, and Solutions to Welding Porosity

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