What Is Porosity in Welding?

Porosity is a costly and dangerous issue for welders. Porosity in welding refers to cavity formation in welds, which can vary in shape and size. Poor joint preparation, improper shielding gas usage and excessive welding speed are some of the causes of porosity in welding.

Welding porosity can lead to reduced strength, heat loss, increased costs and poor corrosion resistance. Pre-weld treatment, proper shielding gas usage, reduced arc time and staying updated on industry welding techniques can help prevent porosity in welding.

Attending a technical trade program like Universal Technical Institute's (UTI’s) Welding Technology program can help aspiring welders learn how to prevent porosity as well as the skills necessary for a career in the welding industry.¹

Students of this program can learn four essential welding processes, which will prepare them to pursue an entry-level role in the welding industry after graduation.

Learning these fundamental welding techniques can help technicians avoid welding porosity! Continue reading to learn more. We'll look at what causes welding porosity, how it affects the welding process and how to prevent it.

What Is Porosity in Welding?

Porosity in welding refers to cavity formation in welds. These cavities can vary in shape and size, ranging from discrete, tiny gas bubbles to larger craters on the material’s surface. There are several different types of welding porosity, including:

• Surface porosity: This looks like open gaps on the welded area’s surface.
• Subsurface porosity: This can be difficult to detect with the naked human eye due to its location beneath the surface.
• Cratering porosity: It appears as uneven and distinct crater shapes in the welded area and is most commonly caused by an insufficient amount of molten filler material that would otherwise fill the cavity.
• Wormholing porosity: It produces defects that look like "wormholes," named after their resemblance to a worm burrowing its way through the material.

Read more: The Differences Between Welding, Brazing and Soldering

What Causes Porosity in Welding?

Welding porosity happens when gas pockets form between two molten pieces during the welding process. There are several possible causes for these gas pockets, which can prevent a weld from being sturdy and structurally sound.

Poor joint preparation

Welded materials may not join properly if the edges are not sufficiently cleaned and beveled beforehand. Impurities such as dirt, paint and oil may block access to the pure material.

These obstructions can cause gaps between the welded materials, which prevent a clean weld. Welders may also apply excessive heat, causing metals to harden too quickly, leaving gaps where there should be molten material.

Improper shielding gas usage

A shielding gas of the incorrect type or quantity will not provide adequate protection against porosity. It may also allow too much nitrogen from the air into the weld area, where it can become trapped in the materials as they cool, causing porosity.

Excessive welding speed

Excessive welding speeds can cause the root gap to be too small or too large. Gases can enter these gaps and become trapped as the molten materials cool.

Read more: Polarity in Welding: The Beginner’s Guide

What Are the Harms of Welding Porosity?

Welding porosity affects the final product’s durability and the overall success of the project. Let’s review some reasons why:

• Reduced strength: Porosity weakens the welded joint and increases the risk of breakage or cracking. The joint becomes weaker as a result, threatening its structural integrity.
• Heat loss: Welding porosity defects allow heat to escape, causing the welded metal to cool too quickly. Future welding attempts will then be less effective and more difficult to perform.
• Increased costs: Porosity can increase the time and materials required for repair or replacement parts, resulting in higher overall labor, material and utility costs.
• Poor corrosion resistance: Weld porosity can reduce corrosion resistance, which increases the risk of rust damage. This is especially true in stainless steel welding, where porosity makes the material especially susceptible to acid, rust and other corrosive elements.

Read more: What is Fabrication in Welding?

4 Tips To Prevent Porosity in Welding

How to prevent porosity in welding? The most viable method of repairing welding porosity is to completely remove the porous section. Attempting to weld over porosity rarely solves the underlying problem. The most effective way to deal with welding porosity is to prevent it entirely, which is very possible with proper welding and workspace preparation techniques.

1. Pre-weld treatment

Proper pre-weld treatment can help remove surface contaminants from the metal and create a more uniform surface for unobstructed welding. This can involve surface cleaning and beveling to ensure a smooth weld. Anti-corrosive solutions can also aid in preventing acid and rust contamination, which can degrade the quality of the weld.

2. Proper shielding gas usage

Welders should use gases specifically designed for their welding applications and follow the manufacturer's recommended gas flow rate and pressure. Excess oxygen is less likely to enter the weld and become trapped with the right type of shielding gas at the correct gas flow rate and pressure.

3. Reduced arc time

Excessive arc time during welding can increase the likelihood of oxygen entering the molten pool and forming gas pockets within the weld area. Welders should keep each weld bead small and break up long beads with short pauses to reduce weld porosity caused by long arc times.

4. Keeping up with industry welding techniques

Staying updated on the latest welding industry standards requires initiative and curiosity and is an important part of a welder’s duties. Doing so will allow welders to identify and complete high-quality welds. This way, they can complete high-stakes welding projects while avoiding costly mistakes.

This can be made much easier with formal welding training. Some employers may also prefer formally trained welders for their technical experience, as they may require less on-the-job training for entry-level welding roles than those without technical training.

Students in our 36-week Welding Technology training program are taught four different types of arc welding methods! Completing our welding courses will prepare graduates to pursue careers in the industry since they may be more familiar with critical welding safety procedures and capable of producing successful welds – and therefore avoid welding porosity.

Read more: What is Welding Burnback?

Learn To Avoid Porosity in Welding With Industry Training!

Welding porosity can jeopardize a critical project, reducing the quality of the welded product and delaying workplace productivity. So, if you need to brush up on porosity in welding to maintain a high-quality weld, come back to this guide to refresh your memory!

Are you an aspiring welder ready to take the next step? Look no further than Universal Technical Institute's Welding Technology program! UTI's 36-week welding program provides hands-on training from experienced instructors who can help students develop the skills and knowledge needed to pursue a career as a welder.

Request information to learn more. Fill out our welding school application when you’re ready to train!