Porosity in Welding - Causes and Preventions (Part 2)

What are most common causes of porosity in welding and how can be they prevented? You can refer below to find the answers you need.

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Porosity in Welding - Causes and Preventions (Part 1)

6. Excessively long arc length

Weld porosity occurs in case of excessively long arc length (also, high voltage). The shielding magnitude will be reduced, inducing air entrapment if the welding gun is kept away from the joint making longer arc length. Proper arc length is suggested to avert breezes/ draughts.

7. Wrong surface treatments

Weld characteristics can be weakened due to released gases during surface/ painting treatments. Such treatments as galvanizing or zinc coating would create gas and other particles unwelcomed. As a prevention, predict the result of chemical reactions prior to particular surface treatments.

8. Laminated surface

Welding disturbance can also eventuate in case of laminated surface. When welding the laminated work piece, gear up for unlaminated parent metal to ensure the qualified weld procedure.

9. Open surface

Any surface open to the atmospheric air would be prone to contamination. Air introduced from the back side via root opening would be entrapped in the weld puddle. Ensure that your weld joint is safeguarded from such air crevices.

10. Improper welding flux

Welding flux is required to be cautiously treated because of their moisture absorbility. They must be provided in dry conditions. It also should be noted that using low-activity flux induces surface porosity. Then you’re recommended to apply high-activity flux that offers qualified welds without porosity. 

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Porosity in Welding - Causes and Preventions (Part 1)

What are most common causes of porosity in welding and how can they be prevented? You can refer below to find the answers you need.

You may also be interested in:
Porosity in Welding - Causes and Preventions (Part 2)
5 Tips to Avoid Porosity in Welding

Porosity is defined as cavities in a weld as a consequence of gas entrapment. The gas introduction in the weld is associated with certain mistakes that should be eliminated. The in-weld metal porosity is varied by location and shape of occurrence. For example, while some gas cavities are in spherical shape, some, like the worm holes, are in long shape. Then to predict mistakes possibly causing porosity and the related preventions is important before welding. Specified below are details about most common causes of weld porosity along with their solutions.

1. Moist electrodes

As recommended, employ the baked electrodes in the process of stick welding to avoid any moisture content involved in the weld metal. At worst, there may be small cavities created in the weld metal because the steam can be driven out during the welding heat. Porosity occurs when the low hydrogen electrodes or stainless steel electrodes aren’t appropriately kept in the dry condition. Certain moisture is needed within a limit in low hydrogen electrodes though, in some case, the weld metal will be subjected to porosity if moisture surpass the limit. Follow those steps for prevention:

• Parent metal is required to be preheated for moisture removal.

• The electrodes must be kept in the dry condition.

• Before use, apply last backing.

• It is a must that electrodes are not oven baked prior to use, as there requires a humble amount of moisture for enhanced performance and weldability of electrode.

2. Polluted surface

Parent electrodes or metals may be prone to contamination in the atmosphere. Any moisture, oil, grease content on the surface has something to do with the gas formation as being under exposure of welding temperature, and can induce porosity in your weld. To fix it, wipe off the material by particular procedure of surface preparation.

3. Inappropriate gas shield

Porosity can eventuate in case of inappropriate gas shield inducing air entrapment. The welding worker is required to check the attachment of the gas hose with the equipment, and get rid of any hose contamination. Right connection would avert any gas shield loss and no air entrapment as a result. Also, draughts and air flow in the shop can lead to the gas flow restricted. There requires screening to keep away from such restrictions in the gas flow.

4. Insufficient electrode de-oxidant

In time of solidification, lower solubility can make excess oxygen release from the weld metal that then can suffer carbon monoxide formation. The porosity occurs as a result. In this case, certain de-oxidants are often added in the filler metals, electrodes, and even in the parent metals for oxygen content removal (also, de-oxidation). Thus, insufficient de-oxidants can induce bad de-oxidation and are the culprit to weld defect. For prevention, employ electrodes with sufficient de-oxidants.

5. Too high flow rate of gas shield

The flow rate of gas shield is too high, and then air can be pulled into the weld metal, which may lead to turbulence. Optimize your gas flow, offer welds of quality without gas loss. Also, it would save cost.

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5 Tips to Avoid Porosity in Welding

Find out tips to avoid porosity in welding, making sure of your weld look and durability.

You may also be interested in:
Porosity in Welding: Causes and Preventions (Part 1)

There are many welders jobs now in the market and there need more people to fill the seats. Many countries tend to reduce the flow of immigrant workers though, welding industry has wholeheartedly welcomed laborforce with this skill. To this end, job placement agencies often play a good role in helping companies find abroad workers with certain qualities they need. Employers with an eye for productivity often expect your hires to possess those traits: dedication, hard work, ability to create quality welds with minimized defects – weld porosity, for example. Just the same as the cavity in the mouth, weld porosity worsens your weld look and the repair is sometimes frustrating.

Porosity in welding occurs when a gas – often oxygen, nitrogen and/ or hydrogen, or a contaminant gets absorbed into the weld puddle. This fault would cause weak, hole-filled, bubbly welds that don’t meet code and can even make pieces of the project collapse. That's why there is no alternative but to redo such faulty welds. And it will be the best if welders can save that work by knowing how to prevent weld porosity. Below are 5 tips that may help with weld porosity prevention, especially during Mig (Gas Metal Arc Welding).

1. Keep It Clean

The material surface must be dry and clean. Oil, moisture, rust and grease are big enemy to welding. They can find ways to mix with weld puddle when the welding temperature rises, trapping gas which leads to bubbles as the material cools down.

Keep an eye on possible chemical reactions that could also cause porosity if your material gets coated with paint, zinc or other laminates. The trapped gas might be in T joints when you weld on both sides. Specially, before you begin aluminum welding, clean the outside layer of oxide.

For those who may be interested in:

Tig Welding Aluminum Tips That Will Help You Tremendously
How to Mig Weld Aluminum Using Spool Gun

2. Check gas flow

Watch for the flow of shielding gas. You will have trouble if it’s too low or too high. The power of the flow is associated with the air quantity disturbed at the weld site that contaminant can mix with weld puddle.

3. Check equipment

Make sure there is no kink or leak to the hose, which can affect your shielding gas flow. Ensure the hose isn’t contaminated.

Check your gun liner to know whether it is clean and properly sized. Employ the contact tip of right size on your weld gun. Sometimes, the tip of your weld gun can be clogged, then make sure to check.

4. Maintain calm conditions

A breeze seems nice in a workshop that welding temperatures can surpass 2,500°F, but turns out to be bad for welding. Instead, keep calm conditions. Watch for strong currents and air flows, the arc length. If the gun is further away from your weld site, the gas shield can become weaker. This makes gas and air to seep into weld puddle and bubbles often appear.

5. Take it slow and steady

In Mig welding, the wire feed should seamlessly come off the reel. Check to see whether your wire feeding system has an easy-to-adjust brake and set the appropriate tension for the wire not to coast. When welding, take it slow and steady. Any haste can often induce weld porosity as the wire feed malfunctions can decelerate production.

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