Page 227 - CITS - Welder - Trade Practical

WELDER - CITS

Skill Sequence

Demonstrate fabrication of corner joints on M.S. plate (sheet 6 mm
thick plate) in vertical downward progression by GMAW

Objectives: At the end of this exercise you shall be able to
• demonstrate fabrication of corner joints 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 filet heed gas of sheets to square.
- Deburr and clean the surface of the plates by carbon steel wire brush and filling.
- Set the plate in the form of corner as per drawing.
- Wear protective clothes.

- Connect the torch to the positive terminal of the machine.
- Set 90-100 A current/corresponding wire feed rate, 19 to 20 arc voltage and deposit the run using Dips transfer
mode.
- Tack weld (min. 10mm length) on both ends of the corner joint as showing Fig1.

- Keep the tack welded job in vertical position on a weld positioner.
- Strike an arc and move the torch steady straight from the tor if the joint down wards.
- Weld the corner 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.
- Avoid under cut

- Ensure the edges of the plate is not melted off due to excessive weaving.
- Ensure the region under cut at the toe of the 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
Noe: Avoid side-to-side movement of the electrode.

Deslag and clean the root bead thoroughly.
Deposit the final covering run with a 4mmø medium coated MS electrode and 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.

Inspect the lap fillet weld and ensure.
- It has equal leg length with slight convexity
- The upper edge of the plate has not melted off
- It is free from surface defects.

210

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