Page 220 - CITS - Welder - Trade Practical

WELDER - CITS

Skill Sequence

Demonstrate fabrication of lap joint on m.s. plate (sheet 6 mm.

thick plate) in vertical downward 0progression by GMAW

Objectives: At the end of this exercise you shall be able to
• demonstrate fabrication of lap joint on m.s. plate (sheet 6 mm. thick plate) in vertical downward progression
by GMAW.

- Cut the sheet by shearing machine as per drawing.
- Grind and file the edges of sheets to square.
- Deburr and clean the surface of the plates by carbon steel wire brush and filling.
- Set the plate A on the plate B in the form of lap as per drawing.

- Wear protective clothes.
- Connect the torch to the positive terminal of the machine
- Set 90-100A current/corresponding wire feed rate, 19 to 20 arc voltage and deposit the run using Dip transfer
mode.
- Tack weld (min. 10mm length) on both ends of the lap joint
- Keep the tack welded job in vertical position on a weld positioner.
- Strike anare and move the torch steady straight from the bottom if the joint upwards.
- Weld the lap joint by using 0.8mm dia. Mild steel filler wire and using stringer bead welding technique.

- Ensure good leg length and even fusion of plates. 13 Avoid under cut.
- Ensure the edges of the plate is not melted off due to excessive weaving.
- Ensure there is no undercut at the other toe of the lap weld on plate.
- Clean the bead by wire brush.
- Inspect the welded joint for undercut, porosity, uneven bead formation, edge of the plate melted off, distortion
and good bead profile
Note: Avoid side-to-side movement of the electrode.

Deslag and clean the root bead thoroughly.
Deposit the final covering run with a 160 amp current.

Give side-to-side movement to the electrode not more than 2.5 times its dia.
Use the same electrode angle as was used for the root bead.
Note: Prevent the upper edge of the plate from melting off by not allowing the arc to concentrate
more on the upper edge.
Remove the slag with a chipping hammer.
Clean the weld with a steel wire brush.

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CITS : C G & M - Welder - Exercise 54(A) CITS : C G & M - Welder - Exercise 54(A)