Welding is a “special process” different to the other processes we use in metal fabrication. That’s because you can’t tell just by looking at a weld how well two pieces of metal are joined. It could look sound but have very little depth of penetration or be full of porosity. Yes, there are ways of inspecting welds, but they tend to be slow and costly. And if you find it’s bad, the job has to be done again, probably delaying delivery. This is why experience is so important in welding, and particularly in the TIG welding services we offer.
The Challenge of Welding
Making a good weld depends on matching all the process variables to the individual job. Every process has variables, but welding has more than most. There’s workpiece geometry, thickness, conductivity and fixturing, as well as electrode shape, orientation, distance from the workpiece, shielding gas and movement speed. Our skilled welders would probably add others to this list like AC or DC current, polarity, and whether or not to use pulsed welding.
It’s this complexity that makes welding difficult, and while the basic techniques can be learned in schools and Community Colleges they can’t prepare welders for the variety of jobs they’ll encounter in the workplace. There’s just no substitute for experience.
MIG and TIG
These are the main welding processes in our fabrication shop. Both use an electric arc to melt metal, but have some significant differences. Chief among these is the way filler wire is added. In MIG (Metal Inert Gas) the electrode is consumed as the filler wire while in TIG (Tungsten Inert Gas) the electrode is made from tungsten and filler wire is added separately. (Filler wire fills the gap between the two pieces of metal being joined and creates the fillet you’ll see in right-angle joints.)
MIG and TIG are used in different ways. Generally speaking, MIG is faster, but yields a less good-looking weld. TIG is slower but the weld looks better and needs little to no clean-up. We prefer TIG for welds that will be visible on the finished fabrication and also for difficult-to-weld materials. Aluminum is one that can be tricky, and so too are more exotic materials like Inconel.
Before striking an arc the experienced welder weighs up a job carefully. He’ll consider how heat will flow through the workpiece and how it might distort. He’ll think about where to start and which direction to move, what electrode shape will work best and where to insert the feed wire. TIG in particular has many variables to manage, including current, voltage, and soft starting and finishing, (which is what the foot pedal is used for.)
New welders are always advised to get a feel for how heat will flow and the weld form by practicing on samples of the workpiece metal first. In our shop it’s not uncommon to see even experienced welders make a few test welds. This helps them decide their electrical settings, filler wire thickness, orientation and so on. Yes, preparation like this takes a little time, but it’s an essential part of doing the job right.
When It Has to be Right
Lots of people can weld metal, but far fewer can be relied on to make a good weld every time. Here at Wiley our welders have years of experience and know how to do do the job right. Come to us for TIG welding services, or indeed any welding, and you can be confident of getting a high quality job that won’t let you down.