Striking of Arc
Striking the are is a basic action through out the are welding operation . It will occurr every time the welding is to be started . It is an essential basic skill to learn arc welding .
Setting Welding Current Condition
(1) Select the electrode size as per the thickness of the metal to be welded.
| PLATE THICKNESS (Approx. in mm.) |
SIZE OF ELECTRODE (Core wire dia.) |
CURRENT RANGE (Amps.) |
|---|---|---|
| 1.6 | 1.6 mm | 40 - 60 |
| 2.5 | 2.5 mm | 50 - 80 |
| 4.0 | 3.2 mm | 90 - 130 |
| 6.0 | 4.0 mm | 130 - 180 |
| 8.0 | 5.0 mm | 180 - 270 |
| 25.0 | 6.0 mm | 300 - 400 |
(2) The electrode site should not be more than the thickness of metal to be welded .
(3) Set the welding current on the welding machine as per the electrode size to be used , using a current regulator .
(4) Connect the electrode to negative if the machine is a DC .
Methods of Striking
There are too methods of Striking the arc.
(i) Tapping Method
(ii) Scratching Method
1. Tapping Method
(i) Hold the electrode vertically at a distance of about 12 mm from the job to be welded .
(ii) Protect your eyes with the welding screen .
(iii) Strike the arc by moving the electrode down to touch the job surface lightly .
(iv) Immediately move the electrode vertically up slowly approximately 6 mm for a few seconds and then lover it to approximately 4 mm or according to the diameter of core wire from the surface to maintain a compect arc .
2. Scratching Method
(i) Hold the electrode at a distance of about 30 mm above the job piece at one end at 75 ° angle to the surface line .
(ii) Bring the hand screen in front of your eyes .
(iii) Strike the arc by dragging ( to pull in force ) the electrode quickly and softly across the welding job using wrist movement only , similar to that of striking a match .
(iv) Withdraw the electrode approximately 6 mm from the surface for a few seconds and then lower it to approximately 4mm distance to maintain the arc .
(v) If the arc has been properly struck a burst of light with a steady sharep sound will be produced .
(vi) Break the arc by quickly with drawing the electrode up .
The Tapping Method is mostly recommended as it does not put any pit marks on the job surface .
If the electrode freezes are stick to the plate it should be immediately freed by a quick twist of the wrist to avoid over heating or spoiling .
