Page 116 - CITS - Welder - Trade Practical

WELDER - CITS

5 Select the nozzle No.10 and 0.15kg/cm2 pressure for both the gases.
6 Select a 3.15 mm copper silver alloy filler rod.

7 Select copper/silver alloy flux.
8 Follow necessary safety precautions.
9 Set the job with a proper root gap or with diverging allowance.
Note : Do not tack weld.

10 Apply the flux in the form of paste on both sides of the plate and on the filler rod.
11 Preheat the base metal.
12 Deposit the weld metal in the groove in one run.
13 Post-heat the weldment and cool the joint slowly.

14 Clean the flux residue on the weldment and the penetrated portion.
15 Inspect the weld for defects.
Skill Sequence

Clean the surface of the workpiece by using emery sheet or a wire brush to remove the oxides thoroughly and
other impurities.

File the edges to the required form. (Fig 1)
Select nozzle No.5-7.
Note : A nozzle one size larger should be used as compared with the M.S. sheet welding because of
high conductivity and quick dissipation of heat.

Select a 2.00 mm ø copper-silver alloy filler rod.
Select copper-silver alloy flux.
Set the job with a proper root gap or with a diverging allowance. (Fig 2) Do not tack weld.

Fig 1

Note : Copper has a high coefficient of expansion and it is necessary to set the plates diverging at
the rate of 3-4 mm per 300 mm. run, because they come together and the root gap gets closed so
much on being welded.
Set a strictly neutral flame.

Preheat the base metal up to ‘peacock neck’ colour (3500C) and commence welding.
Apply the flux as paste on the filler rod and at the joints.
Deposit the metal in the groove in one run with sufficient reinforcement on the joint using the leftward technique.
The blow pipe angle should be 600 - 800 and the filler rod angle 250 - 300 to the line of weld. Fig 3.
Always keep the molten pool and the tip of the filler rod under the shadow of the outer envelope.
Maintain the temperature of the job throughout the welding operation.

It is always better to keep a helper to continuously heat the job using another blow pipe as you are welding a
copper joint. Otherwise, the joint will begin to crack from the starting point as you proceed to weld further.

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CITS : C G & M - Welder - Exercise 22