Page 171 - CITS - Fitter Trade Pactical - Volume - 2

FITTER - CITS

• Hold a correct arc for a short distance and break by quickly withdrawing the electrode up.
The correct arc burning will give steady, sharp, crackling sound.

Repeat this exercise until the arc can be struck every time without the electrode freezing.
If the electrode freezes (sticks) to the plate, it should be freed immediately by a quick twist of the
wrist motion to avoid overheating or spoiling.

TASK 2 : Laying straight line beads by arc welding

• Check the size of the raw material.
• Mark and file to size.
• Mark the bead position as per drawing.

• Set the work piece on the welding Table in a flat position
• Set the arc-welding plant and connect the welding cables.
• Select and fix M.S. Electrode Æ4mm in the holder.
Ensure that the electrode-holder JAWS are clean.
• Set a welding current 140-150 amps on a AC or DC machine.

If the power source is D.C. connect the electrode with the negative straight polarity.
• Wear the complete safety apparel and check the filter lens of the welding screen.
• Strike the arc on a scrap piece for trial and observe the current setting.
Ensure that the burning of the electrode is normal.

• Strike the arc on the job-piece at one edge and maintain a uniform normal short arc.
• Move the electrode in a straight line and complete the bead at the other edge of the plate.
• During welding maintain a correct angle of the electrode at 70o - 80o.
• Arc length producing a steady sharp crackling sound.
• Travel speed approx. at the rate of 150mm per minute.
• Remove the slag from the weld bead and inspect for:

- Uniform width and height - slag inclusion.
- Normal depth of fusion.
- Straightness.
• Repeat the exercise till you achieve good results.

156

CITS : C G & M - Fitter - Exercise 49