BOC Smootharc Multi 180 - Manual Metal Arc Welding (MMAW); Introduction and Machine Setup

Manual Metal Arc Welding (MMAW)
TIG Welding techniques
Weld Metal
Slag
Core Wire
Flux Covering
Arc
Weld Pool
Workpiece
Introduction
Manual Metal Arc welding is the process of joining metals where an
electric arc is struck between the metal to be welded (parent metal) and
a ux-coated ller wire (the electrode). Theheat of the arc melts the
parent metal and the electrode which mix together to form, on cooling,
acontinuous solid mass.
Before arc welding can be carried out, a suitable power source is
required. Two types of power sources may be used for arc welding, direct
current (DC) or alternating current (AC).
The essential di󹟽erence between these two power sources is that, in the
case of DC, the current remains constant in magnitude and ows in the
same direction. Similarly, the voltage in the circuit remains constant in
magnitude and polarity (i.e. positive or negative).
In the case of AC however, the current ows rst in one direction and
then the other. Similarly, the voltage in the circuit changes from positive
to negative with changes in direction of current ow. This complete
reversal is called a ‘half cycle’ and repeats as long as the current
ows. The rate of change of direction of current ow is known as the
‘frequency’ of the supply and is measured by the number of cycles
completed per second. The standard frequency of the AC supply in
Australia is 50 Hz (Hertz).
Successful welding depends the correct selection of equipment,
electrode type and size, welding current, arc length, application
techniques, electrode angle, travel speed and welding preparation.
Welding machines and accessories
The most important consideration when contemplating the use of arc
welding for the rst time is the purchase of a suitable weldingmachine.
BOC o󹟽ers a popular range of arc welding machines ranging from small
240V portable welders to heavy-duty welders used by the largest
steelfabricators. The choice of welding machine is based mostly on the
following factors:
→ primary voltage, e.g. 240 Volt or 380 Volt
→ output amperage required, e.g. 140 amps
→ output required, e.g. AC or DC +/-
→ duty cycle required, e.g. 35% @ 140 amps
→ method of cooling, e.g. air-cooled or oil-cooled method of output
amperage control, e.g. tapped secondary lugs
→ or innitely variable control.
For example, the Smootharc 175 Multiprocess connects to 240 Volt
supply (15 amps Input), has an output of 175 amps DC @ 35%
dutycycle.
Having decided on a welding machine, appropriate accessories are
required. These are items such as welding cables, clamps, electrode
holder, chipping hammer, helmet, shaded and clear lenses, scull cap,
gloves and other personal protective equipment.
BOC stocks a huge range of personal protective equipment. This
combined with BOC’s extensive network ensures fast reliable service
throughout the South Pacic.
51BOC Smootharc Multi 180/200 Operating manual
Installation for MMA process