Welding is a great way to join two pieces of metal, allowing you to build or repair anything from an automobile body to everyday household items. Most welders strive for perfection in their work, but even the best of us can run into issues with welding porosity-tiny openings that appear along the seam base metal together after welding weld metal.
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This defect can weaken your metal joint and cause corrosion over time if left untreated. In this blog post, we'll discuss what exactly porosity is, the common causes of porosity and its formation groove weld side, and how to prevent it at all costs. With this knowledge firmly under your belt, you can make stronger welds than ever before and create perfect industry-standard results.
What Is Welding Porosity?
Welding porosity is the presence of tiny openings along a welded seam due to gas entrapment during the welding process. Porosity defects can range in size from very small pinholes to large pockets, and their presence can weaken the metal joint and cause corrosion over time.
The severity of porosity depends greatly on its size, shape, and location. Smaller porosity defects are not as common or severe as larger ones, but any defect of this type can lead to structural failure.
Several Forms of Porosity
Welding porosity can take several forms, including pinhole surface pores (small round openings), channels (long thin lines of porosity along the whole weld area), and craters (larger round or oval-shaped holes).
Each defect weakens the metal joint somehow, so it’s important to be aware of its presence.
Pinholes and channels are more common than craters, but several factors can cause all three forms. The key to eliminating these flaws is understanding what causes them in the first place so that you can take preventive measures to ensure your welds are strong and defects-free.
Distributed
Distributed porosity is a welding porosity typically appearing as a series of small pinholes along the weld. It occurs when air, moisture, oil, or gas pockets become trapped in the welding process, resulting in weak spots throughout the joint.
Surface-breaking
Surface-breaking weld porosity is a form of welding porosity that appears as small openings along the surface of the weld. This defect occurs when gas pockets become trapped in molten metal during welding, creating depressions in the metal.
However, as with distributed surface porosity, this surface-breaking porosity occurring in pores can weaken the metal joint and cause corrosion over time if left untreated. Surface-breaking porosity is more serious than distributed porosity as it is visible to the naked eye and can indicate deeper structural issues.
Wormholing
Wormhole is a type of welding porosity that appears as long, thin channels along the surface contamination a weld. This defect occurs when gas pockets become trapped inside or in the weld and form tunnels beneath the surface of the metal.
These narrow passageways weaken structural integrity of the steel and metal joint and can lead to corrosion over time. If left untreated, wormholes can cause terrible structural failures and may be visible.
Cratering
Cratering is a type of welding porosity that appears as large, round, or oval-shaped openings along the outside air of a whole welded joint. This defect occurs when gas pockets become trapped in the metal during welding, resulting in large hollows that can weaken the joint significantly.
What Causes Porosity in Welding?
Various factors, including improper welding technique, over-welding industry, poor joint preparation, inadequate cleaning and inspection procedures, incorrect shielding gas mixes or flow rates, etc., can cause welding porosity.
Improper Shielding Gas Usage
Using the right shielding gas or having an adequate gas flow rate can lead to porosity in your welds. Shielding gases are used during welding to protect the weld joint from other atmospheric gases and contamination, and a lack of proper protection can allow air or moisture into the joint and cause porosity defects.
Poor Joint Preparation
Proper joint preparation is key to the welding machines achieving strong, defect-free welds. If the base material for the joint surface is not adequately prepared before welding, it can lead to porosity due to trapped gases or airborne contaminants.
Excessive Welding Speed
Welding too quickly can result in porosity due to insufficient heat input. This often happens when inexperienced welders attempt to rush through their work, resulting in a weak joint and an overall poor-quality weld.
How to prevent porosity?
Fortunately, porosity can be prevented with the right techniques and procedures.
Pre-Weld Treatment
Before welding, it is important to properly clean the joint surface of the weld metal of any contaminants and inspect it for any defects. This ensures the entire weld-on area is free from foreign particles cutting fluids that could cause porosity.
Properly Storing Stick Electrodes
Stick electrodes should be stored in a cool, dry place and inspected before use. If they have been exposed to extreme temperatures or moisture, this can cause porosity due to trapped gases within the steel core of the electrode.
How Do You Fix Porosity?
Porosity can be difficult to repair as it requires access to the inside of the weld. Cutting out and re-welding the area repair porosity may be necessary to correct the weld defect. However, there is no guarantee that porosity won’t reoccur.
The best way to fix porosity is to prevent it from occurring in the first place by using all your welding equipment and processes and following proper welding techniques and procedures.
By understanding what porosity is, its causes, and how to prevent it, you can make stronger welds with consistent quality. With this knowledge, you should be fine achieving perfect industry-standard results every time.
FAQs
What causes welding porosity?
Welding porosity is caused by gas entrapment during the welding process. Factors that can lead to weld porosity include improper welding technique, over-welding engineer poor joint preparation, inadequate cleaning and inspection of welding procedures, incorrect shielding gas mixes or flow rates, and more.
How can I prevent welding porosity?
In order to prevent porosity, it is essential to have a comprehensive understanding of the welding processes and their proper execution. This involves using the appropriate shielding gas mix and controlling gas flow and rate, adhering to the correct welding procedure, preparing the joint adequately, and employing effective cleaning techniques prior to welding. These measures are crucial for minimizing welding defects and ensuring a sound weld bead. Whether you're engaged in TIG welding or MIG welding, paying attention to these factors is vital in mitigating porosity and achieving successful welds.
How can I identify surface porosity?
Surface porosity can be identified by inspecting the welded area. It appears as small bubbles or voids on the surface of the metal and may have a matte finish compared to the rest of the material.
Additionally, you may hear trapped air escaping during welding as it reaches the molten weld pool. Surface contamination can also cause porosity, so it is important to properly clean the surface before welding. Subsurface porosity may not be visible and requires further testing, such as radiography.
Preventative measures, such as keeping the weld area free of contaminants, can help minimize surface porosity. Additionally, avoiding excessive speeds and using the appropriate welding technique will reduce the risk of creating surface pores.
How can I avoid welding porosity?
Porosity in a weld can be avoided by using the correct welding technique and ensuring adequate shielding gas coverage over the weld. Additionally, cooling the weld with an argon purge or water jacket will help minimize any potential pores from forming. Lastly, regularly replacing consumable parts such as tig gas lenses can help minimize porosity. Taking these preventative measures will reduce the risk of creating surface pores.