Welcome to The Welding Knowledge Zone

The Welding Knowledge Zone is a free service designed to help you understand the welding process and improve your results. This information is reviewed regularly and updated where necessary, however The Welders Warehouse Ltd cannot accept liability for inaccuracy of information or any loss incurred as a result of an inaccuracy.

Manual Metal Arc Welding (MMA)

The oldest of the arc welding processes, Arc welding has a filler rod coated with flux. When a welding arc is struck between the rod and the workpiece the filler rod and flux melt. As the flux melts it creates a gas shield around the molten weld pool to prevent oxidisation. Immediately after fusion the flux forms a hard slag over the weld to prevent oxidisation during cooling. When welding is complete this slag is chipped off. Arc welding is a versatile process as it can be performed with basic welding equipment, used in most conditions and for welding most weldable metals with the exception of aluminium, which can be Arc welded but not very satisfactorily.

Types of Arc Welding Electrode:

Rutile Flux Coated - The most common type of welding rod coating, rutile coated Arc Welding electrodes are easy to use, offer good levels of mechanical strength and produce a weld of good visual appearance.

Basic Flux Coated - Basic, or Low Hydrogen, welding rod coatings are used for higher strength joints and are recommended for structural Arc Welding applications and materials thicker than 10mm. Basic coated welding rods are more difficult to use than rutile coated welding rods and do not offer such a good weld appearance, they are therefore best chosen by those with experience of welding.

Cellulosic Flux Coated - Best known for deep weld penetration and rapid burn speed, cellulosic coated welding rods are commonly used for professional root Arc Welding of plate and pipe.

Arc Welding Current is largely determined by the type of welding electrode, the type of job and the material to be welded. Most welding rod manufacturers will recommend a current range for a given welding rod, however as a general guide allow 35 amps of welding current for every millimetre of Arc Welding electrode diameter (plus or minus 15% depending on the job) ie: 2.5mm welding electrode = 88 amps (or a range of 75 - 102 amps).

Types of Arc Welding Equipment

There are three types of Arc Welding power source:

Arc Welding Transformer with moving shunt power adjustment - These Arc Welding machines are the cheapest type and rely on winding two parts of a transformer together to adjust power. These welding machines give an AC current otput. Whilst cheap, the AC welding output means that the welding arc tends to be a little difficult to start and, once started, the welding arc will tend to be quite fierce and spattery.

Arc Welding Transformer with potentiometer power adjustment - These Arc Welding machines usually give a DC welding current output. DC welding output offers easier arc starting and a smoother softer arc. This type of Arc Welding equipment has largely been superceded by modern inverter type Arc Welding power sources.

Arc Welding Inverter - These Arc Welding machines have a potentiometer power adjustment and give a DC welding current output for easy arc striking and smoother softer arc. Arc Welding Inverters often have additional features such as "Anti Stick" to reduce the likelihood of the welding electrode sticking to the job and "Arc Force" to make arc striking even easier. Arc Welding Inverters are also light in weight and will run for longer than transformer based welding machines before they overheat.

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