Avoiding common welding defects
We all know that any weld is only as good as the material preparation, welding technique, equipment and materials that go into it. So what are the main welding defects that can undermine the integrity of your welds, cause costly rework and put lives at risk?
Last time we looked at material prep and its importance for avoiding welding defects. From correct welding technique and choice of metal, to thorough cleaning and even which filler wire you use, many variables determine the quality of your final weld. But what can go wrong and cause those frustrating problems?
Talk to experienced welders such as R-Tech’s Mike Gadsby and you’ll discover that the most notorious welding defects include porosity, poor weld penetration, cold lapping, hydrogen embrittlement (from moisture or hydrogen-containing contaminants on the metal), cracking and metal distortion.
We urge you to learn more about these, their causes and how to avoid problems. It’s the essential complement to good welding training, experience and practice.
Weld defects and different processes
Whether it’s MMA, TIG or MIG welding, every process has strengths and limitations. Alongside other contributory factors, poor awareness of these can contribute to welding defects. On the other hand, being able to match the correct process to your project gives you an important head start in the battle against defective welds.
For example, consider MIG welding’s use of gas. As we’ve shown elsewhere, MIG is a wonderfully versatile process for many amateur and professional welders. However, its inherent reliance on gas means the MIG process is often unsuitable for outdoor use where wind can play havoc with welding. Okay, so using gasless MIG wire might be an alternative, but often not…
At risk of stating the obvious, you need knowledge and experience to make the right process choices. That’s why agricultural welders traditionally find MMA welding so versatile for quick farm repairs. And why high-end motorsports fabricators swear by TIG. Even a process as straightforward as MMA comes with potential for welding defects. For instance, if you ever rework a MMA weld, make sure to remove all residual slag first.
Machine knowledge and correct maintenance
The technical characteristics of particular process equipment also play their part. Reverting to MIG welding, lack of gas and contamination of welds by water or oil are potential weld killers. So’s a blocked shroud or damaged O-ring on your MIG torch. Alongside solid welding skills, correct machine knowledge, equipment care and regular maintenance is vital if you want to avoid welding defects.
And different metals…
Not surprisingly, different metals also bring the challenge of defects. Certain materials, such as aluminium and steel, simply can’t be welded together. Any attempt to do so will be doomed to failure. We’ll be looking at the challenge of welding dissimilar materials in a future article. As ever, if in doubt, seek advice before committing to a particular process-material combo. Wherever possible, make a test weld too.
Meanwhile, trust us when we say that thorough understanding of different metal characteristics will serve you well in your welding career. For instance, castings are known for being problematic. So too is aluminium; its thermal conductivity makes burn through an ever-present risk. As for the challenge of welding copper or titanium? We’ll leave that for another article…
Material cleanliness is key
As discussed last week, material cleanliness is vital to avoid welding defects. Regardless of the welding process and metal, we can’t over-emphasise the importance of thorough cleaning.
Sometimes, as Mike Gadsby explains, special procedures are needed to achieve what initially looks like a simple cleaning task:
‘Some years ago, I was welding hydraulic cylinders from earth-moving equipment. Part of the work involved removing and refurbishing large machined bungs where hydraulic lines joined the cylinders. Due to prolonged exposure to pressurised oil, normal cleaning, including hot solvent-washing, wouldn’t remove all the hydraulic oil that had permeated the metal. To make welding possible – and ensure our welds’ integrity – we had to thoroughly pre-heat the steel to drive the residual oil out.’
For many projects, simple cleaning, correct metal choices, good welding technique and understanding characteristics such as thermal conductivity help prevent defective welds. However, as seasoned professionals know – often from bitter experience – new challenges to weld quality always await you.
Knowledge, skills and practice
If you take away only one thing, it’s that avoiding welding defects relies on combining process knowledge, good welding skills and material understanding.
Even if you’ve welded for decades, you’ll know there’s always something new to learn. As a novice welder, there’s no substitute for training, knowledge, experience, practice and learning from those who have gone before you.
As ever, do your research, speak with colleagues and watch welding videos for information. It’s also easy to speak with welding professionals such as R-Tech’s Mike Gadsby and his colleagues. There’s not much they haven’t seen and their advice could help you avoid a potentially disastrous welding defect.
Send us an email or call us sometime!