Welding is an essential part of modern manufacturing, from high-end production of aerospace parts to small-scale craftwork and repair projects. Porosity is an unavoidable and detrimental side effect of the welding process.
The porosity rate of a weld can drastically affect the strength and durability of a weld and is estimated to account for up to 17 percent of weld rejects in the aerospace industry and 13 percent in the automotive industry. With such serious implications, it is important to understand what porosity is in welding and how to work towards reducing its occurrence.
What is Porosity in Welding?Porosity in welding is a common defect caused when air or other gases are entrapped inside the weld area while welding. Porosity significantly weakens welded parts and increases the likelihood of failure.
It can occur due to a variety of factors, ranging from bad techniques to impurities in the steel used.
Types Of PorosityThere are many types of porosity that can be seen in welding, including:
- Macroporosity, which is characterized by large cavities that form in the weld.
- Microporosity, which consists of very small cavities that are often not visible to the naked eye, but which can weaken the weld.
- Inert gas porosity, which is caused by entrapped gas bubbles.
- Arc strikes, which are caused by a spark from the arc that embeds itself into the weld.
Causes Of PorosityPorosity can be caused by a number of factors, including:
- Improper welding technique, such as not cleaning or preheating the joint before welding or not keeping the welding arc steady enough.
- Impurities in the steel, such as oxygen, sulfur, or other elements that can cause gaps in the weld.
- Using an inadequate welding rod.
- Using flux that is not completely removed from the weld.
Preventing PorosityPorosity can be prevented by following the proper welding technique and using the right welding rod.
Other steps that can be taken to minimize or eliminate porosity include:
- Cleaning the joint thoroughly and preheating it to the temperature recommended by the manufacturer.
- Making sure that the rod is of the correct size and type.
- Using flux that is free of impurities.
- Maintaining the correct arc length and welding speed.
- Checking the weld area periodically for signs of porosity.