Specifications

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314 AU : 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) WeldingFundamentals of Manual Metal Arc (MMA) Welding
Manual metal arc welding, like other welding processes, has welding
procedure problems that may develop and which can cause
defects in the weld. Some defects are caused by problems with the
materials. Other welding problems may not be foreseeable and may
require immediate corrective action. A poor welding technique and
improper choice of welding parameters can cause weld defects.
Defects that can occur when using the shielded metal arc welding
process are slag inclusions, wagon tracks, porosity, wormhole
porosity, undercutting, lack of fusion, overlapping, burn through,
arc strikes, craters and excessive weld spatter. Many of these
welding technique problems weaken the weld and can cause
cracking. Other problems that can occur and which can reduce
the quality of the weld are arc blow, finger nailing and improper
electrode coating moisture contents.
Defects Caused by Welding Technique
Slag Inclusions
Slag inclusions occur when slag particles are trapped inside the weld
metal, which produces a weaker weld. These can be caused by:
erratic travel speed
too wide a weaving motion
slag left on the previous weld pass
too large an electrode being used
letting slag run ahead of the arc.
This defect can be prevented by:
a uniform travel speed
a tighter weaving motion
complete slag removal before welding
using a smaller electrode
keeping the slag behind the arc, which is done by shortening the
arc, increasing the travel speed or changing the electrode angle.
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Wagon Tracks
Top View Thru Transparent Bead
Wagon tracks are linear slag inclusions that run the longitudinal axis
of the weld. They result from allowing the slag to run ahead of the
weld puddle and by slag left on the previous weld pass. These occur
at the toe lines of the previous weld bead.
Porosity
Porosity is gas pockets in the weld metal that may be scattered
in small clusters or along the entire length of the weld. Porosity
weakens the weld in approximately the same way that slag
inclusions do.
Porosity may be caused by:
excessive welding current
rust, grease, oil or dirt on the surface of the base metal
excessive moisture in the electrode coatings
impurities in the base metal
too short an arc length, except when using low-hydrogen or
stainless steel electrodes
travel speed too high, which causes freezing of the weld puddle
before gases can escape.
This problem can be prevented by:
lowering the welding current
cleaning the surface of the base metal
redrying electrodes
changing to a different base metal with a different composition
using a slightly longer arc length
lowering the travel speed to let the gases escape
preheating the base metal, using a different type of electrode,
or both.
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Welding Defects and Problems