Page 285 - CITS - Welder - Trade Practical

WELDER - CITS

Job Sequence
- Prepare the job to size as per drawing.
- Clean the job surface with stainless steel wire brush.
- Mark parallel lines on the job surface as per drawing and punch the lines.
- Set the workpiece (job) on the work table in flat position.
- Fix the 0.8mm diameter S.S. wire spool in position, lock it up and pull the wire through the guide tube, rollers,
spiral and contact tip of the torch.
- Start the welding machine. Connect the torch to the positive (DC +ve) terminal (DCRP) of the machine.
- Open the argon gas flow before striking the arc.
- Set the arc voltage at 19-21 volt as required for dip transfer mode.
- Set the Gas Flow Rate at 8-10 LPM (Liters Per Minute)
- Set the wire feed rate so as to get 90-100 Amp by striking the arc on a scrap plate.
- Use DIN 11 or 12 black/green filter glass on Hand Shield/Helmet for above current setting.
- Wear the protective clothing as required
Note: Wear protective clothing.

Skill Sequence

Corner 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
• Corner joint on S.S sheet 1.6 mm thick in flat position by GTAW.

Setting and tacking the lap joint
Set the corner joint with an overlap of 25mm.
The 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. current for tacking.
Set the joint in a flat position using angle iron.
Welding the lap fillet joint in flat position
Deposit root run with 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 120 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 corner 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.

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CITS : C G & M - Welder - Exercise 71