10
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 (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 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.
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-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.