Believe it or not, there are more than 30 different types of welding!
All welding processes are fundamentally methods for applying heat to metals with the aim of joining two pieces together in a controlled manner. Techniques range from simple oxy-fuel to high-tech processes such as laser beam welding. Of these, MIG and TIG arc welding are the most commonly used, so today we’re going to share just a little about these two methods.
The first thing to say is that it’s absolutely vital to use the right welding method for your project, to ensure optimal performance for the environment and potential stresses the welds may be subjected to.
MIG (Metal Inert Gas) welding is quick and easy to use and works well on a wide variety of metals and thicknesses.
MIG welding fuses two pieces of metal very quickly. The process involves a wire being fed constantly through a welding gun at steady pace. Once the wire leaves the gun, it comes into contact with the electric tip, which causes it to melt and makes the desired weld. Because it is continuously fed, the wire acts as both a filler and an electrode, which helps join the two metal objects together and enables us to fuse thicker pieces without the need to heat the metal all the way through.
The key to successful MIG Welding is the proper selection of:
- Electrode – composition, diameter and packaging
- Shielding Gas – type (composition), purity and flow rate
- Process Variables – current, voltage, mode of metal transfer and travel speed
- Equipment – power source, welding gun and wire feeder
So, what are the benefits of MIG welding?
- Skilled operators can achieve deep weld penetration, which permits the use of small weld sizes for equivalent weld strengths in certain applications
- It’s ideal for multi-pass welding (with proper filler metal selection)
- It enables us to produce X-ray quality welds
And the limitations for an inexperienced operator?
- Base metal contamination poses problems: the base metal must be clean and rust free.
- Burn through can be an issue when welding extremely thin materials (<1.5mm).
- The correct process parameter settings are critical for success: the wrong ones can result in defects, especially when welding base metals thicker than 6mm.
MIG welding is often described as an easy process – we’ve even heard claims that it’s no harder to use than a glue gun! But it’s not quite that simple. Whilst undoubtedly not the most difficult welding technique, it still needs the right skills and application to create a weld you can rely on.
TIG (Tungsten Inert Gas) welding, also known as Gas Tungsten Arc Welding (GTAW), is an extremely versatile process, but requires more skill than MIG welding. It can be used to weld most metals, giving superior, typically defect-free, weld quality.
The TIG welding process can be used with or without a filler metal, but always requires two other elements: heat and shielding. The heat is produced by electricity passing through a non-combustible tungsten electrode, creating an arc to the metal; the shielding is created using compressed gas, which bathes the weld area to protect it from air and contaminants. Once the arc and weld pool are established, the torch is moved along the joint, and the arc progressively melts the surfaces to be joined. If used, filler metal is provided by the use of a welding rod, manually dipped into the arc, which adds molten metal to the leading edge of the weld pool to fill the joint. This is a two-handed job – one feeds the rod whilst the other holds the TIG torch – requiring great precision.
For a good TIG weld, the following variables need to be managed closely:
Arc voltage (length) & welding current… the amount of energy the arc produces is proportional to the current and the voltage.
Travel speed… the energy transferred per unit length of weld is inversely proportional to the travel speed.
Shielding gas composition… shielding gases are typically inert to protect the electrode from contamination; the choice of gas is important, for example: helium shielding provides more penetration than argon.
In addition, the tungsten electrode can be alloyed with small amounts of active elements to increase emissivity of the electrode; this provides quicker arc starting, greater arc stability, and longer electrode life.
So, what are the benefits of TIG welding?
- It’s a clean process, typically free from spatter which can occur with other arc welding methods
- It welds more metals and alloys than other processes: steel, stainless steel, chromoly steel, aluminium, nickel alloys, magnesium, copper, brass, bronze, even gold!
- It provides control of heat input and filler metal additions, allowing for precise adjustments to optimise weld quality
And what makes it a specialist process?
- A high degree of operator skill is required to produce quality welds: operators must simultaneously modulate the welding current, hold the torch at the right angle, maintain the right gap between the electrode and the work, move the torch in a consistent manner, add filler rod at just the right time, and “dab” the rod in the right place.
- It’s a very precise technique: the best TIG equipment gives operators the ability to make continuous adjustments throughout the weld.
- Hence it’s a process which cannot be automated easily!
TIG welding is most commonly used on thinner gauge materials (its effectiveness is limited on thicker tasks, unlike MIG welding) and for projects which require precision and control to achieve a fine, even delicate, finish.
So, to conclude… when comparing these two welding methods, the obvious main difference is technique. With MIG welding, a wire electrode is continuously fed through a gun to create the weld. In TIG welding, the operator feeds the filler material onto the weld with one hand whilst operating the torch with the other. Which does mean that, typically, TIG is the slower of the two processes.
However, what really matters is making sure you have the right weld for your project, so you can be sure it will perform exactly how you need it to… and that’s where our experts can help.
At Basing Engineering, we work with you to find the right solution for your project, each and every time. We’re proud to have the latest, state-of-the-art welding equipment; we work with the highest quality products; and our team of specialist welders are all highly-trained, highly-skilled individuals.
So… how can we help you with your next project? Let’s get together and explore your options!