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Whether you are a professional or novice, you must have heard about “porosity” in welding. Porosity in welding refers to those defects in welding that welders are looking for easy ways to avoid to make their weld good.
This post will discuss the meaning of porosity, types, causes, and ways to prevent porosity.
Let’s dive in.
Porosity In Welding Explained
Porosity is the word welders refer to when there are gas pores found in the weld bead after the solidification process causing a weld defect.
When a weld is completed, there will be different sizes of pores randomly seen in it. Porosity can be found in the center of the weld, with the pores occurring on the surface or under the weld.
Types Of Weld Porosity
They are often linked with the porosity that forms when the weld pool has been solidified because of the trapped gas.
Crater pipes happen when the weld pool has shrieked when solidifying. Thereby making the liquid to solid volume change, which causes crater pipes.
However, when the welding arc has been extinguished, it causes the weld puddle to solidify speedily. In some cases, preventing the welding cable from getting into the weld pool before extinguishing the arc can promote the formation of crater pipes.
Surface Breaking Pores And Distributed Porosity
The term “surface breaking pores” describes the levels that distributed porosity has reached on the surface.
Porosity is caused when the gases particles are absorbed into the weld pool while melting and when the weld puddle is solidifying.
This can be a result of the poor state of the shielding gas.
When air is trapped in the shielding gas, porosity can occur no matter the amount of air.
Surface-breaking pores can even occur when at least 1.5% of the shielding gas is mixed with air.
Other causes include draughts, gas flowing at a high rate, and a gas line leak.
Wormholes are stretched pores that occur on the radiograph with a zig-zag pattern.
The stretched form of wormholes shows that a considerable amount of gas was trapped in the weld metal during solidification.
If there are any crevices, such as T joints, where the gas can get trapped by heavy primer coats and thick paint, the gas can also build up.
This means as you weld T-joints, the coating thickness must meet the requirements not to cause wormhole porosity.
Causes Of Porosity
When there is the presence of grease, oil, or moisture on the metal or electrodes, it can contribute to gas formation due to the high welding temperatures. This can cause porosity when the weld pool starts to solidify.
Gas Flow Rate
When the gas flow rate is high, it can result in turbulence in the weld pool. This can trap air in the weld metal, and the result will be porosity.
A Wet Electrode
Porosity can occur if the electrodes are wet, which will cause the wet content of the weld metal to rise. And when the heat from the MIG welding process drives the steam out, it would cause tiny cavities in the weld metal resulting in a significant welding defect.
Also, keeping the stainless steel electrodes and low-hydrogen electrodes in wet conditions can cause porosity to occur.
However, understand that some level of wetness is needed for low-hydrogen electrodes to perform better. But if the level of moisture is too high, the weld metal will be vulnerable to porosity.
Inconsistent Gas Shield
Inconsistent gas shields can cause porosity. In order to prevent any problem from arising, there must be a connection between the gas hose and the equipment to avoid the air from mixing with the shielding gas.
Also, you need to know as a welder that draught and airflow within the environment can cause the restriction of gas flow.
Inadequate Electrodes Deoxidant
When solidification is taking place, there is usually excess oxygen coming out of the weld. This happens as a result of reduced solubility reacting with other gases in the air.
This forms carbon monoxide and can cause porosity as well. As a result, deoxidants are added to the filler metals and electrodes to remove the oxygen content.
However, understand that if there are inadequate deoxidants, it can lead to distributed porosity because of the excess oxygen which has formed carbon monoxide.
You have to handle flux carefully because of its capacity to absorb moisture. This means it must be supplied dry. Moreover, high activity flux is recommended to avoid surface porosity from occurring.
When a surface has been affected by open-air and atmospheric conditions, it is prone to porosity due to contamination. This means that air in the weld paddle can cause porosity when solidification starts.
Painting can cause specific gas to be released, which can result in porosity. Galvanizing and zinc coating produces unwanted particles and gases, which can cause defects in your weld.
How To Prevent Porosity
The workspace needs to be void of breeze, too much moisture, and particles to protect your weld from porosity.
Check Your Gas Flow
Keep the gas flow at a level recommended for the application you are working on; doing so will help you get your weld with little porosity.
The welding materials such as metals, equipment, and any workspace surface need to be clean from moisture or grease to reduce the high porosity rate.
Check Your Equipment
Always check your equipment like the hoses to be sure they are not leaking, check the pipes to know they are not in any way exposed, check every connection before welding starts.
This article looked at the meaning of porosity, the types of porosity, what causes these different types of porosity, and ways to prevent porosity.
We have seen that pores are of different sizes and are seen randomly in a finished weld.
Sometimes, this porosity can only be found in the center of the weld, with the pores occurring on the surface or under the weld.
However, eliminating porosity in the weld is impossible, but you can take advantage of the preventive ways discussed in this post to reduce porosity.
Which of the causes of porosity will you want to prevent for you to get a good weld?
The comment section is below for you to drop your thoughts on this post.
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