Practical Welding Exercise 2
Single & multi-run wet weld deposit ‘lap joint’
Oscillation Technique (normally used for the root pass)
This technique involves a small but continual change to the slope angle, while welding. It’s mainly used to help the electrode burn concentrically, and help produce a wider weld deposit. It reduces non-concentric burning of the electrode by ensuring as much of the electrode as possible comes into contact with the faces of the joint.
Step-back Technique (normally used for the last pass)
This technique involves a continual stalling of the forward travel motion by traveling backwards slightly, into the previous deposited weld. This technique has two particular functions;
it helps improve the final microstructure, by reducing the solidification rate of the weld puddle and increases throat thickness.
- Remove from plate surface any rust or scale by wire brushing
- Tack plates together as shown on picture
- Ensure a firm ground / return lead connection at all times
- Ensuring the electrode remains in the joint, touching both plates at all times
- Prepare the electrode as described in Exercise One
- Firstly, deposit the root run using the ‘Oscillation Technique’. For the second pass use the 'Drag Technique' with the change in slope angle as shown. For the third pass use ‘Step-Back Technique’
- All slag and spatter must be removed from the weld deposits and plate surface
- Ensure a firm ground/return lead connection at all times
- Avoid tangling of welding cables and ensure you are not between the cables
- Maintain an eye level view at approximately the same level as the plate
- Weld across yourself, not towards yourself, i.e. stand at 90° to the plate
Repeat as necessary.
Things to Watch Out for: Keeping your lead angle and travel speed within the specified range, and depositing the weld in the correct place. If you keep your lead angles as required, your travel speed will stay pretty much as necessary. As for depositing the weld in the correct place, keep a very close eye on you slope angles and the previous deposit. Practice makes perfect and remember to experiment with current setting. When welding multipass lap joints, you may find it useful to change your base current settings, depending upon which pass you are currently welding. Generally, the root pass will require the highest current, the second pass should have the current reduced slightly and the third pass should be somewhere in between the two.
NOTE: Only make the welding machine hot when ready to weld. Ask for the current to be made cold immediately after welding.