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7
5.5 Torch installation
MMA cable connections
Connect electrode lead to positive terminal
TIG welding cable connection
Connect the TIG torch to the - terminal
5.6 Work return lead connection
MMA cable connections
Connect work lead to negative terminal
TIG welding
Connect the work return lead to the + terminal
6.0 Operation
WARNING
When using an open arc process, it is necessary to use correct
eye, head, and body protection.
6.1 MMA Welding Guide
Effects of MMA welding various materials
High tensile and alloy steels
The two most prominent effects of welding these steels are the
formation of a hardened zone in the weld area, and, if suitable
precautions are not taken, the occurrence in this zone of under-bead
cracks. Hardened zone and under-bead cracks in the weld area may
be reduced by using the correct electrodes, preheating, using higher
current settings, using larger electrodes sizes, short runs for larger
electrode deposits or tempering in a furnace.
Manganese steels
The effect on manganese steel of slow cooling from high
temperatures is enbrittlement. For this reason it is absolutely
essential to keep manganese steel cool during welding by quenching
after each weld or skip welding to distribute the heat.
Cast iron
Most types of cast iron, except white iron, are weldable. White iron,
because of its extreme brittleness, generally cracks when attempts
are made to weld it. Trouble may also be experienced when welding
white-heart malleable, due to the porosity caused by gas held in this
type of iron.
Copper and alloys
The most important factor is the high rate of heat conductivity of
copper, making preheating of heavy sections necessary to give
proper fusion of weld and base metal.
Types of electrodes
Arc welding electrodes are classified into a number of groups
depending on their applications. There are a great number of
electrodes used for specialized industrial purposes which are not of
particular interest for everyday general work. These include some
low hydrogen types for high tensile steel, cellulose types for welding
large diameter pipes, etc. The range of electrodes dealt with in this
publication will cover the vast majority of applications likely to be
encountered; all are easy to use and will all work on even the most
basic of welding machines.
Metals being joined & electrode comments
Mild steel
6013 ideal electrodes for all general purpose work. Features include
outstanding operator appeal, easy arc starting and low spatter.
Cast iron
99% nickel suitable for joining all cast irons except white cast iron
Stainless steel
316l-16 high corrosion resistance. Ideal for dairy work, etc. On
stainless steels.
6.2 Basic TIG Welding guide
Tig welding cable connection
Connect the TIG torch to the - terminal and the work return lead
to the + terminal for direct current straight polarity. Direct current
straight polarity is the most widely used polarity for DC TIG welding.
It allows limited wear of the electrode since 70% of the heat is
concentrated at the work piece. Connect the gas hose on the TIG
torch to the gas outlet on the gas regulator. Move the selector switch
on the front panel of the machine to the LIFT-TIG position.
Torch starting in LIFT-TIG mode
Ensure the gas supply is switched on and gas is flowing from the
front of the torch nozzle. Briefly contact the tip of the tungsten
electrode down onto the work piece with the torch at around 70
0
from
vertical, lift the torch up from the work piece to draw out an arc. To
prevent melting of the end of the tungsten, do so in a smooth rapid
movement.
OPERA
TION
