ARC Welding & MMA Welding Process

OVERVIEW

• Arc welding is the most flexible and one of the most widely used arc welding processes
• The process uses an electric arc welding to fuse joint areas
• The consumable electrode consists of a metal core wire covered in a concentric clay-like mixture
• The process may be operated with an AC or DC power source
• This process requires highly skilled arc welders to produce good-quality welds
• The process does not require a separate shielding gas

Engine-driven generators can be used in the field as well as in the workshop, and in remote areas where mains power is not available, thereby extending MMA welding’s versatility.

With arc welding, only a limited amount of weld metal can be deposited from one electrode. This means electrodes have to be replaced frequently, making it a less productive process than other welding methods.

The power source on an arc welder is designed is to feed the electric arc, which is present between the base material and the electrode, through the output of a current sufficient in quantity to keep the arc struck Electrode welding is based on the constant current principle i.e. the current delivered by the power source should not vary when the operator moves the electrode towards the piece.

The main construction property of the source is therefore to keep the current unchanged in the presence of variations in arc length as the electrode moves closer to or away from the piece: the more constant the current, the more stable results the arc and the simpler the operator's work. Inside the power source, there is usually a welding current adjustment device, of a mechanical or electronic type. The polarity of the power source output current distinguishes two further categories: