Operating instructions

17BOC Smootharc Advance II MIG 250C Operating manual
Generally Recommended Current Range for BOC Smootharc 13
Size of Electrode (mm) Current Range (Amp)
2.5 60–95
3.2 110–130
4.0 140–165
5.0 170–260
Arc Length
To start 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
nish to the weld. An excessively short arc will cause sticking of the
electrode and rough deposits that are associated with slag inclusions.
For downhand welding, it will be found that an arc length not greater
than the diameter of the core wire will be most satisfactory. Overhead
welding requires a very short arc, so that a minimum of metal will be
lost. Certain BOC electrodes have been specially designed for ‘touch’
welding. These electrodes may be dragged along the work and a
perfectly sound weld is produced.
Electrode Angle
The angle which the electrode makes with the work is important to
ensure a smooth, even transfer of metal. The recommended angles
for use in the various welding positions are covered later.
Correct 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. As a guide for general applications the table below gives
recommended run lengths for the downhand position.
Correct travel speed for normal welding applications varies between
approximately 125–375 mm per minute, depending on electrode size,
size of run required and the amperage used.
Excessive travel speeds lead to poor fusion, lack of penetration, etc.
Whilst too slow a rate of travel will frequently lead to arc instability, slag
inclusions and poor mechanical properties.
Run Length per Electrode – BOC Smootharc 13
Electrode
Size(mm)
Electrode
Length(mm)
Run Length (mm)
Minimum Maximum
4.0 350 175 300
3.2 350 125 225
2.5 350 100 225
Correct Work Preparation
The method of preparation of components to be welded will depend on
equipment available and relative costs. Methods may include sawing,
punching, shearing, lathe cut-o󹟽s, ame cutting and others. In all
cases edges should be prepared for the joints that suit the application.
The following section describes the various joint types and areas of
application.