Specifications

8
315AU : IPRM 2007 : SECTION 8 : CONSUMABLES
WARNING Welding can give rise to electric shock, excessive noise, eye and skin burns due to the arc rays, and a potential health hazard if you breathe in the emitted fumes and gases.
Read all the manufacturer’s instructions to achieve the correct welding conditions and ask your employer for the Materials Safety Data Sheets. Refer to www.boc.com.au or www.boc.co.nz
Fundamentals of Manual Metal Arc (MMA) Welding
Wormhole Porosity (Piping Porosity)
Wormhole porosity is the name given to elongated gas pockets.
The best method of preventing this is to lower the travel speed to
permit gases to escape before the weld metal freezes.
Undercutting
Undercutting is a groove melted in the base metal next
to the toe or root of a weld that is not filled by the
weld metal. Undercutting causes a weaker joint and
it can cause cracking. This defect is caused by:
excessive welding current
too long an arc length
excessive weaving speed
excessive travel speed.
On vertical and horizontal welds, it can also be caused by too large
an electrode size and incorrect electrode angles. This defect can. be
prevented by:
choosing the proper welding current for the type and size of
electrode and the welding position
holding the arc as short as possible
pausing at each side of the weld bead when a weaving technique
is used
using a travel speed slow enough so that the weld metal can
completely fill all of the melted out areas of the base metal.
■
■
■
■
■
■
■
■
Lack of Fusion
Lack of fusion is when the weld metal is not fused to the base metal.
This can occur between the weld metal and the base metal or
between passes in a multiple pass weld. Causes of this defect can be:
excessive travel speed
electrode size too large
welding current too low
poor joint preparation
letting the weld metal get ahead of the arc.
Lack of fusion can usually be prevented by:
reducing the travel speed
using a smaller diameter electrode
increasing the welding current
better joint preparation
using a proper electrode angle.
Overlapping
Overlapping is the protrusion of the weld metal over the edge or
toe of the weld bead. This defect can cause an area of lack of fusion
and create a notch, which can lead to crack initiation. Overlapping is
often produced by:
too slow a travel speed, which permits the weld puddle to get
ahead of the electrode
an incorrect electrode angle.
■
■
■
■
■
■
■
■
■
■
■
■
Legend to Welding Position Abbreviations
Symbol Abbreviation Description
F Flat
H/V-FILLET Horizontal-Vertical Fillet
H Horizontal
V Vertical
V-DOWN Vertical-Down
OH Overhead