MMA (STICK) WELDING FUNDAMENTALS
ELECTRODE SELECTION
As a general rule, the selection of an electrode is straight forward,in that it is only a matter of selecting an electrode of similar composition to the parent
metal. However, for some metals there is a choice of several electrodes, each of which has particular properties to suit specific classes of work. It is
recommend to consult your welding supplier for the correct selection of electrode.
ARC LENGTH
To strike the arc, the electrode should be gently scraped on the work until the arc is established. There is a simple rule for the proper arc length; it should
be the shortest arc that gives a good surface to the weld. An arc too long reduces penetration, produces spatter and gives a rough surface finish to the
weld. An excessively short arc will cause sticking of the electrode and result in poor quality welds. General rule of thumb for down hand welding is to have
an arc length no greater than the diameter of the core wire.
ELECTRODE ANGLE
The angle that the electrode makes with the work is important to ensure a smooth, even transfer of metal. When welding in down hand, fillet, horizontal
or overhead the angle of the electrode is generally between 5 and 15 degrees towards the direction of travel. When vertical up welding the angle of the
electrode should be between 80 and 90 degrees to the work piece.
TRAVEL SPEED
The electrode should be moved along in the direction of the joint being welded at a speed that will give the size of run required. At the same time, the
electrode is fed downwards to keep the correct arc length at all times. Excessive travel speeds lead to poor fusion, lack of penetration etc, while too slow
a rate of travel will frequently lead to arc instability,slag inclusions and poor mechanical properties.
MATERIAL AND JOINT PREPARATION
The material to be welded should be clean and free of any moisture, paint, oil, grease, mill scale, rust or any other material that will hinder the arc and
contaminate the weld material. Joint preparation will depend on the method used include sawing, punching, shearing, machining, flame cutting and
others. In all cases edges should be clean and free of any contaminates. The type of joint will be determined by the chosen application.
The size of the electrode generally depends on the thickness of the section
being welded, and the thicker the section the larger the electrode required.
The table gives the maximum size of electrodes that maybe used for
various thicknesses of section based on using a general purpose type
6013 electrode.
Correct current selection for a particular job is an important factor in
arc welding. With the current set too low, difficulty is experienced in
striking and maintaining a stable arc. The electrode tends to MMA to
the work, penetration is poor and beads with a distinct rounded profile
will be deposited. Too high current is accompanied by overheating of the
electrode resulting undercut and burning through of the base metal and
producing excessive spatter. Normal current for a particular job may be
considered as the maximum, which can be used without burning through
the work, over-heating the electrode or producing a rough spattered
surface. The table shows current ranges generally recommended for a
general purpose type 6013 electrode.
Average Thickness of Material
Maximum Recommended
Electrode Diameter
1.0 - 2.0mm
2.5mm
2.0 - 5.0mm
3.2mm
5.0 - 8.0mm
4.0mm
8.0 - > mm
5.0mm
Electrode Size (ø mm)
Current Range (Amps)
2.5mm
60 - 100
3.2mm
100 - 130
4.0mm
130 - 165
5.0mm
165 - 260
36
| RAZOR MIG 250 Manual
MMA (STICK) WELDING GUIDE
