In this article, we will explore the causes of porosity in welding and provide seven tips for prevention.
We will discuss the importance of proper welding technique, the use of high-quality materials, and the importance of following welding codes and standards.
By following these tips, welders can ensure a strong and reliable weld joint with minimal porosity.
What causes porosity in welding?
Porosity in welding is caused by a number of factors, including inadequate cleaning of the base material, poor welding technique, incorrect welding parameters, incorrect welding rod selection, and contamination of the welding area.
Poor technique can include insufficient penetration or inadequate shielding gas coverage, which can cause trapped air or other gases to become entrapped in the weld and form voids.
Incorrect parameters can lead to improper heat input, inadequate shielding gas coverage, or improper welding rod selection.
Contamination from dirt, oil, or grease can also cause porosity in welding.
What is porosity in welding?
Porosity in welding is a type of imperfection in a welded joint caused by the entrapment of gas or air in the molten weld metal.
It is typically caused by incorrect welding techniques or insufficient shielding from the atmosphere.
Porosity can weaken a welded joint, reducing its strength and making it more prone to corrosion.
How much porosity is acceptable in a weld?
The acceptable porosity in a weld depends on the welding process and the material being welded. Generally, welds with porosity levels below 3% are considered acceptable.
However, some welding processes may have lower acceptable levels of porosity, such as 1%.
It is important to consult the relevant welding standards for the specific welding process and materials to determine the acceptable level of porosity.
7 Tips Tips to Prevent Porosity
- Clean the Welding Area – Porosity can be caused by dirt and debris that contaminates the weld. Before beginning a weld, make sure the area is free from dust, oil, grease, and other contaminants.
- Use Clean Welding Equipment – Porosity can also be caused by using dirty welding equipment. Regularly maintain and clean your welding machine and cables to ensure a clean and efficient weld.
- Choose the Right Filler Metal – The wrong filler metal can lead to porosity in the weld. Make sure to choose the appropriate filler metal for the job, and double-check its compatibility with the base metal.
- Use the Right Amperage – Porosity can be caused by using too much or too little amperage. Make sure to use the appropriate amount of amperage for the job and double-check the settings before beginning the weld.
- Maintain the Right Travel Speed – Porosity can be caused by traveling too quickly or too slowly. Make sure to maintain a consistent travel speed while welding to ensure a quality weld.
- Use Proper Shielding Gas – Porosity can be caused by an inadequate or incorrect shielding gas. Make sure to use the right shielding gas for the job and double-check the settings before beginning the weld.
- Use Preheating and Post-Welding Heat Treatment – Porosity can also be caused by not preheating or post-welding heat treating the material. Make sure to preheat and post-weld heat treat the material to ensure a quality weld.
Types of Porosity in Welding
Porosity in welding is a common occurrence, and there are four main types: distributed, surface breaking pores, wormholes, and crater pipes.
Distributed porosity is characterized by small, evenly distributed gas pockets that are not necessarily visible to the eye.
Surface breaking pores are larger, more visible gas pockets, often appearing as small, round, black holes that are typically spread throughout the weld.
Wormholes usually appear as elongated, cylindrical-shaped porosity and can be difficult to detect.
Crater pipes are formed when the weld pool is not completely filled, leaving behind a hollow pipe-like feature. They are often visible to the naked eye.
Porosity susceptibility of materials
The porosity susceptibility of materials in welding can vary widely based on the material composition and welding parameters used.
Generally, materials with higher carbon content and higher melting points are more prone to porosity formation.
For example, materials such as steel and cast iron have higher porosity susceptibility than materials such as aluminum and stainless steel.
Additionally, the use of higher welding currents and higher welding speeds can further increase the occurrence of porosity in materials.
To reduce the porosity susceptibility of materials in welding, it is important to use the proper welding technique and parameters.
Preheating and post-heating can reduce the formation of porosity in materials with higher melting points, while using a lower welding current, higher travel speed, and a lower heat input can reduce the occurrence of porosity in all materials
Detection and Fixes for Porosity in Welding
To detect porosity, visual and radiographic (x-ray) inspection methods are used to identify any porosity present in the weld.
Once detected, the appropriate remedial action should be taken in order to repair the porosity.
This can involve grinding out the porosity, cleaning the weld and then re-welding, or using a different welding technique such as gas tungsten arc welding (GTAW) or shielded metal arc welding (SMAW).
How To Fix Porosity In Welding:
To fix porosity in welding, the following steps should be followed:
- Clean the weld area by grinding to remove any scale, rust, or other contaminants.
- Make sure the metal is clean and free of dirt, oil, or grease.
- Use a lower welding current to reduce heat input and limit the amount of gas trapped in the joint.
- Increase the travel speed of the welding torch to reduce the time the molten metal is exposed to the atmosphere.
- Use a shielding gas to reduce the amount of oxygen and other contaminants in the welding area.
- Adjust the welding technique to ensure the correct arc length and angle are being used.
- Use a filler material with a lower melting point to minimize the amount of gas released during welding.
- Use a back purge with inert gas to push out any air or gas trapped in the weld area.
- Inspect the weld area after welding to ensure that porosity has been eliminated.
What causes porosity in MIG welding
Porosity in MIG welding can be caused by a variety of factors, such as improper welding speed, incorrect welding technique, or inadequate shielding gas. Additionally, inadequate or irregular cleaning of the weld area, or using contaminated filler metals, can also contribute to porosity.
What causes porosity in stick welding
Porosity in stick welding is typically caused by contamination of the weld area, incorrect electrode angle, improper cleaning of the base metal, or incorrect current setting.
Frequently Asked Questions (FAQs:)
What are 3 main causes of porosity?
- Improper surface preparation: When the surface is not properly prepared prior to coating, porosity can occur.
- Improper application technique: Applying too much or too little of the coating can create spaces and voids in the coating, leading to porosity.
- Contamination: Contaminants such as dust, dirt, oils, or other materials can create porosity when they become trapped in the coating during application.
Can you weld over porosity
Yes, you can weld over porosity. Porosity is a common problem in welding, and can be addressed by increasing the heat input and controlling the welding time and speed. Additionally, increasing the gas flow and using a lower current can help to reduce porosity.
How to avoid porosity in stick welding
- Ensure that the correct stick electrodes are used for the welding job, as different electrodes are designed for different applications.
- Clean the weld joint area to remove any dirt, rust, paint, or other contaminants before welding.
- Set the welding machine to the correct voltage and amperage for the job.
- Use a correct welding technique, such as reducing the travel speed of the electrode, to ensure proper fusion.
- Use a properly sized welding tip to ensure that the weld puddle is not too large, which can cause porosity.
- Monitor the arc length and adjust it as needed to maintain a consistent arc.
- Use a shielding gas to protect the weld area from atmospheric contamination.
- Perform regular maintenance on the welding machine to ensure it is functioning correctly.
What causes porosity in aluminum welding
Porosity in aluminum welding is caused by a variety of factors, including inadequate shielding gas coverage, improper welding technique, and inadequate pre-cleaning of the base material.
Inadequate shielding gas coverage can be caused by improper flow rate, incorrect nozzle angle, or incorrect distance between the nozzle and the welding arc.
Improper welding technique can include improper travel speed, incorrect angle of the electrode, or improper heat input.
Inadequate pre-cleaning of the base material can be caused by oil, grease, or other contaminants that are present on the base material.
What causes porosity in TIG welding
Porosity in TIG welding is caused by several factors, including: inadequate gas coverage, improper shielding gas, inadequate cleaning of the material, excessive heat input, improper torch angle, and excessive travel speed.
What is the cause of porosity in arc welding
The cause of porosity in arc welding is typically due to the presence of contaminants in the weld zone, such as water vapor, oil, dirt, or rust. Other causes of porosity include poor weld preparation, poor welding technique, welding too quickly, and inadequate joint fit-up.
Takeaways:
- Porosity in welding can be caused by a number of factors, including inadequate cleaning of the base material, incorrect welding parameters, and contamination of the welding area.
- To reduce porosity in welding, it is important to use the right welding technique and parameters, and to use high-quality materials.
- Preheating and post-welding heat treatment can reduce the formation of porosity in materials with higher melting points.
- The types of porosity in welding include distributed porosity, surface breaking pores, wormholes, and crater pipes.
- Porosity can be detected using visual and radiographic (x-ray) inspection methods.
- To fix porosity in welding, the area should be cleaned and then re-welded using a different welding technique or parameters.
- To avoid porosity in stick welding, it is important to use the correct stick electrodes, clean the weld joint area, set the welding machine to the correct voltage and amperage, and use a properly sized welding tip.
