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Up Topic American Welding Society Services / Technical Standards & Publications / Mixture gas Ar/N2
- - By abikoswara Date 01-23-2018 02:49 Edited 01-23-2018 03:05
My name is Abi, I'm as Tecnical Authority at the Cononophillips Project I've the problem about mixture gases Ar/N2, each My welder performed welding on the Material DSS which used mixture gases Ar/N2 , always occured Porosity on each welded. Does it mix gases can cause the porosity defect ???

Thankssss
Parent - - By jwright650 (*****) Date 01-23-2018 12:05
Porosity can be caused by several factors.
A simple breeze can blow away the shielding gas.
Too little gas flow which does not provide enough shielding of the atmosphere from the molten weld puddle.
Too much gas flow which results in a venturi effect that will actually draw atmosphere in and contaminate the weld pool.
If the base material is not clean, the contaminants will boil out in the weld puddle.
If the filler materials are not clean or have absorbed moisture those can cause porosity.
If the base material is colder than the dew point, moisture can form on the surface.
In correct technique maintaining too long of an arc can let atmosphere be drawn in.
Welding in a corner can cause a ventri effect.
Excessive voltage can sometimes cause porosity.
Removing the Tig torch too quickly from the weld puddle after extinguishing the arc or too short of a post flow setting can cause porosity.

I'm sure others here can chime in with other factors that escapes my mind at the moment that can cause porosity, but without more information about the welding situation, it is difficult to come to any conclusion or offer any advise.
Parent - - By abikoswara Date 01-24-2018 00:54
Thanks with your opinion, but my problem only occured if i used shielding gas by Argon Nitrogen mixture gas, but if used pure Argon, porosity not appear. why about this problem ???? is it due to a mixture gas i used ?

Thanks
Parent - - By jwright650 (*****) Date 01-24-2018 12:01
Maybe check the dew point or purity of the gas mixture? Something could be a problem with the tank of shielding gas, if that is the only variable that changed.
Parent - - By abikoswara Date 01-24-2018 13:44
Ok, Thanks for your advice
Parent - By 803056 (*****) Date 01-25-2018 01:42
Nitrogen is not an inert gas. It, like many gases, has a higher solubility in liquid metal than in metal that is solidifying. As the solubility decreases, the excess nitrogen must come out of solution. Excess nitrogen that gets trapped, i.e., it doesn’t escape, can cause porosity.

Nitrogen can be used as an alloying constituent in specific stainless steels. As an alloying constituent, nitrogen is an interstitial constituent.

Al
Up Topic American Welding Society Services / Technical Standards & Publications / Mixture gas Ar/N2

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