Gas Metal Arc Welding (GMAW)

GMAW Advantages

There are many advantages to choosing the Gas Metal Arc Welding method. It has the ability to produce great quality welds, at a reasonable price. Generally, the cost per weld metal length is lower than other open arc weld processes. Additionally, it’s applicable to a range of both non-ferrous and ferrous alloys of varying thickness.

Costs

GMAW produces high-quality welds at high-speeds. Although there are both positives and negatives to bare wire GMAW, the initial outlay for solid welding wire is relatively low compared to FCAW or MCAW wires. The variety of welding gas mixes suitable for use with GMAW provides flexibility across areas where, for example, certain gases like argon are expensive. In a busy shop-floor with multiple welders and high output, these costs can add up very quickly!

Welders can weld as fast as they desire, as there is no stopping and starting due to the continuous feed of electrodes. The ability to easily mechanize the process also minimises operator fatigue and increases arc on time which can have a positive effect on profit.
There is no job too big or too small for GMAW and it can replace other joining methods such as riveting, brazing, silver-soldering, or resistance welding.

Efficiency

The operating system for GMAW is much more efficient for the welder than other methods.
Equipment is simple to set up and control; the Gas Metal Arc Welding equipment has been designed with controllability in mind. The welder must only watch the angle of the torch on the material, electrode stick out, control the travel speed, and weld pool shape.

Accuracy

A lesser amount of distortion is one of the main benefits for the welder. There is minimal weld slag and spatter when solid wire or metal-cored wires are used, making for quick and easy cleanup. The lack of slag and spatter generally just makes for a smoother weld surface.

These characteristics provide substantial cost savings since metal finishing is an expensive production exercise. Another safety point is that it creates less fumes and produces a lower heat input in comparison to other forms of welding.

Flexibility

The weld is not restricted to position or by material. It can be facilitated through any position on light or heavy gauge materials. For a heavier material, a narrower groove angle with a thicker root face can be used. A narrow groove reduces the amount of filler metal deposit required and therefore cuts preparation time and welding time.

Current density is the amperage per square inch of the cross-sectional area of the electrode. With GMAW, the current concentration is higher than it is for stick electrode welding. This allows for higher deposition rates than there would be in manual welding. High current density concentrates more energy at one point than one with low density.

Adjustment is based on the type of material being welded, the thickness, position of the weld, deposition rate, and final weld specifications. Similarly, welding current and travel speed also have an effect on bead height and width. Variables increase or decrease both bead height and width at the same time. Any change to these variables ultimately affects the amount of filler metal being deposited per given joint length.

If the travel speed and welding current are not providing adequate weld metal to fill in a particular joint, they must be adjusted accordingly. Arc voltage is very important to create a good weld. Ultimately, arc voltage controls the surface heating, bead contour and some defects such as undercutting, porosity, and discontinuities.

To complete the weld bead, the arc needs to be manipulated to prevent what is called a ‘weld crater.’ This is achieved by welding to the end of the required weld length, and then reversing the direction of travel for approximately an inch before releasing the gun trigger or terminating the arc.