Parweld XTT 202P Operator'S Manual Download Page 8

Page: 8 / 20

www.parweld.co.uk

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; are all easy to use and all will 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

318l-16 high corrosion resistance. Ideal for dairy work, etc. on
stainless steels.

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

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. 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 to the machine. Briefly contact

the tip of the tungsten electrode down onto the work piece with the
torch at around 70

from vertical. Depress the trigger to start the gas

flow and switch on the power, lift the torch up from the work piece

to draw out an arc. To prevent melting of the end of the tungsten the
machine will increase the output current when it detects the rise in
arc voltage as the tungsten is lifted from the work piece. At the end
of the weld release the torch trigger and the power will slope down
and switch off.

Torch starting in HF mode

Ensure the gas supply is switched on to the machine. Hold the torch
with the tip of the tungsten approx 2-3 mm from the job. Depress the

trigger to start the gas flow and switch on the power. At the end of

the weld release the torch trigger and the power will slope down and
switch off.

TIG welding guide ranges

Electrode diameter

AC current

(amps)

DC current

(amps)

0.040” (1.0mm)

15-30