Linde BOC RAPTOR Operating Manual page 40

The limits of this range should not normally be
exceeded.
The following table shows the current ranges
generally recommended for BOC Smootharc 13.
Generally Recommended Current Range
for BOC Smootharc 13
Size of Electrode
2.5 mm
3.2 mm
4.0 mm
5.0 mm
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 finish 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.
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Current Range
60–95 A
110–130 A
140–165 A
170–260 A
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 Electrode
Size Length
4.0 mm 350 mm
3.2 mm 350 mm
2.5 mm 350 mm
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-offs, flame 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.
Run Length
Min. to Max.
175 to 300 mm
125 to 225 mm
100 to 225 mm