Porosity in Laser Welding
Laser welding is a beacon of precision and efficiency in modern manufacturing, offering multiple benefits. However, even in application of this advanced technology, there are some challenges, and one such challenge is porosity. In this article, we delve into what porosity is, its adverse effects, causes, preventive measures, and why addressing this issue is crucial for anyone who is going for Laser Welding.
What is Porosity?
During Laser welding, if there are any air gaps, or zero gap condition is not maintained, or proper precautions are not taken during the operation, it is possible that some gas packets or voids can be left in the weld metal. These manifest as spherical or elongated bubbles.
This is considered as a defect in Laser Welding, because not only it causes defects, but fails to fulfill the basic condition that a perfect Laser Welded work piece should be continuous, smooth and pore free.
Adverse Effects of Porosity:
Porosity is a defect and affects the quality of the weld.:
Reduced Strength: Porosity weakens the weld, lowering its overall strength and load-bearing capacity.
Corrosion: The air gaps left behind may provide entrance to corrosive elements and contaminants, which make the weld more susceptible to corrosion.
Leakage: In certain applications, for instance, in the oil and gas industry, it must be leakage proof. But, the air gaps left behind may cause leakage.
Aesthetic Impact: In industries where aesthetics matter, such as automotive or architectural welding, porosity can be visually unappealing, affecting the product’s overall quality.
Causes of Porosity:
Gas Entrapment: If there are any entrapped gasses in the molten pools, they try to escape the pool and this leads to spatters, however, some of the gas remain entrapped inside even after the weld pool solidifies and this may lead to formation of gas bubbles in the weld, leading to porosity.
High Heat Input: When the heat input is higher than required, the material may get vaporized and generate more gasses which may remain entrapped even after the weld solidifies and give rise to porosity.
Contaminants: Presence of contaminants like oil, dust, etc. on the workpiece or filler material during welding can lead to porosity.
Inadequate shielding: If proper shielding gas is not used during the process, contaminants can enter the weld pool causing porosity.
Improper Fixturing: Basic requirement or pre requisite for Laser Welding is that there must be zero gap between the edges to be welded. If fixturing is not proper, and some gap is left, it can cause porosity.
Coating: In many automotive applications, the parts are given a Zinc coating or another such coating to prevent rusting. If the melting point of coating material is lower than the base metal, it vaporizes and may cause gas entrapment after the welding pool solidifies. This may lead to porosity.
Preventive Measures:
Some Preventive measures need to be taken while performing Laser Welding to ensure proper welding and avoid porosity :
Shielding Gas: Typically, inert gasses like Argon should be used to shield the weld pool from atmospheric contamination.
Cleanliness: Work pieces should be thoroughly cleaned before operation to remove contaminants or dust particles .
Proper fixturing: Proper fixturing must be used to attain the zero gap condition and avoid porosity.
Controlled process: Process parameters should be set properly. Heat input must be controlled, excess heat input should be avoided, travel speed should be maintained properly.
Conclusion:
Porosity is a serious issue in Laser Welding, but with proper understanding of its root causes and accordingly carrying out preventive measures, it can be avoided.
Striving for porosity-free welds is essential, not only for structural integrity but also for ensuring the visual appeal and longevity of welded components. As laser welding technology continues to advance, addressing porosity remains a critical step toward achieving flawless and reliable welds in various industries. It is always advisable to consult experts for proper application and process to avoid defects and ensure a smooth, high quality weld.
We, at Laser Automation Pvt. Ltd. Have our own application lab where experts carry out trials on customer’s components and provide proper solutions . For any queries related to Laser Welding, feel free to contact us.