Metal Fabrication Resources by Blackstone Advanced Technologies

Blackstone Advanced Technologies Blog
Sep 20, 2019 6:41:37 AM

How Much Porosity in Welding Is Acceptable?

Sometimes welding is the only way to affix two objects to each other. In these cases, glue, string, bolts, and screws just won't do the job. However, welding does have its issues as defects can occur and the weld becomes porous. While some porosity is acceptable in a weld, there are some ways to fix these issues.


How Much Porosity Is Acceptable In A Weld


When it comes to porosity, the American Welding Society dictates that the sum of the diameters of visible porosity should not exceed 3/8 inches, or 9.5 mm, in any linear inch of the weld, or exceed 3.4 inches or 19 mm, in any 12-inch length of a weld.


How To Prevent Porosity In Welding


There are at least four ways to prevent porosity in welding. Strong air flows and currents could affect the weld puddle, same with the voltage and arc length. Make sure you check for leaks before and after each use, as well as the wiring. Making sure there is no surface contamination and that you have the right gas flow will greatly reduce the chances of porosity.


What Causes Porosity in Welds?


There are many causes when it comes to porosity in welds. Some of which are:

  • The weld nozzle is too far away
  • The gas hose has been contaminated
  • The welding gas is contaminated
  • The gas flow is too high.

In MIG welding, one possible cause of porosity that there is insufficient heat input.


How To Fix Porosity In Welds


Other than turning up the amperage and welding over the bad weld, which can cause other problems, the best solution is to prevent porosity in the future. These include watching your travel angle, avoid drafts, and make sure the gas flow rate isn't too high, as well as checking for gas leaks.


Types Of Welding Defects


There are many types of welding defects, such as:

  • Incomplete penetration
  • Undercutting
  • Slag Inclusions
  • Incomplete Fusion

In MIG welding:

  • Craters
  • Lack of Fusion
  • Burn Through

In TIG welding:

  • Sugaring on stainless steel
  • Too much amperage on aluminum
  • Poor color on stainless steel


At Blackstone Advanced Technologies, we care about weld quality, even if we aren't the ones doing the job. Awareness of your surroundings as well as inspecting your equipment and materials before starting on the projects are two of the best ways to prevent porosity while welding.


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