Page 245 - CITS - Welder - Trade Practical

WELDER - CITS

EXERCISE 59(A) : Evaluate single “V” joint on aluminium

plate (thickness 6 mm) by GMAW

Objectives

At the end of this exercise you shall be able to
• prepare the plates with necessary beveling and root face
• preset the plates in alignment in vertical plane with necessary root gap and tack weld
• deposit-the root run with root penetration and uniform melting of both root faces of the joint
• set up the GMAW machine and set welding parameters.

Job Sequence

- Cut the plate by using hacksaw cutting as per drawing
- Clean the joining edges and surface of the plates

- Adjust the power source and wire feeder to obtain 18 to 19 volts and 90 and 100 amperes, gas flow 8-10 LPM.
- Thoroughly clean the pieces to be joined. Pay particular attention to the top of the plate, the sidewalls of the
groove and the underside of the joint. Grind or file a1.5 mm root face on each beveled edge
- Tack the pieces together and position

- Put spacers under the plate so that you don’t weld the plate to your table
- Hold the gun perpendicular to the joint and strike the arc at the tack. Move the torch from left to right end of
the joint i.e use back hand technique. Weave the gun from side to side. When the gun is in the center of the
joint, watch the arc very closely. By concentrating the arc on the leadingedge of the puddle, you can cause the
bead to penetrate through the joint and fuse both root faces.If you bring the arc too far down in the puddle, the
wire will go through the joint and the arc will become very erratic.If you allow the arc to go to of ar upon the
puddle,your penetration will decrease and you will not penetrate the joint.Practice will help you use the arc to
control the flow of the weld puddle
- Complete the joint using the bead sequence. Use a slight weave to help the weld flow and to fuse to the side
walls of the groove and the previous beads

- When you have completed the weld, cool it and examine it. The root should show full penetration along the
entirelength. The rootreinforcement should protrude beyond the joint from 0.5 to 1mm. The face of the weld
should merge smoothly with the base metal. There inforcement should be atleast 1mm above the surface of
the base metal and also should not exceed beyond 1.5.

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