Page 283 - CITS - Welder - Trade Practical

WELDER - CITS

Skill Sequence

Lap joint on S.S sheet 1.6 mm thick in Flat

position by GTAW

Objectives: At the end of this exercise you shall be able to
• lap joint on S.S sheet 1.6 mm thick in flat position by GTAW.

Setting and tacking the lap joint.
Set the lap joint with an overlap of 25mm.
The overlap may vary based on the plate thickness.
Tack-weld on both ends. Ensure the 2 lapping sur-faces are perfectly cleaned and they contact each other properly.
Set the joint in a flat position using angle iron.
Welding the lap fillet joint in flat position
Deposit root run with 100-110 amp current.
Maintain 80° angle to the line of the weld and 45° between the weld faces.
Maintain a short arc to get uniform fusion and root penetration.

Note: Avoid side-to-side movement of the electrode.
Deslag and clean the root bead thoroughly.
Deposit the final covering run with 90 - 110 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.

266

CITS : C G & M - Welder - Exercise 71 CITS : C G & M - Welder - Exercise 71