1. Manual Arc Welding Operation
Mastering the technique of manual arc welding in various positions involves four key movements:
- A) Electrode angle
- B) Transverse swinging action
- C) Arc stabilization action
- D) Selecting different transverse swinging methods based on various welding positions
1. Arc Ignition
The welding process of manual arc welding starts from arc ignition, which can be done in two ways: scratch ignition and touch ignition.
1.1 Scratch ignition involves aligning the electrode tip with the workpiece, then slightly twisting the wrist to scratch the workpiece surface with the electrode, lifting the electrode 2-4mm to generate an arc in the air, and then maintaining the arc length within the allowable range of the electrode diameter.
1.2 Touch ignition involves bending the wrist down and lightly touching the workpiece with the electrode.
2. Electrode Manipulation
After the arc is ignited, quickly lift the electrode by 2-4mm to start welding.
Manual arc welding operation is a combination of three basic actions: moving forward along the welding direction, swinging transversely along the weld, and feeding the electrode towards the molten pool.
There are mainly two electrode manipulation techniques:
2.1 Straight-line manipulation:
During welding, maintain a certain arc length and move forward without swinging, resulting in a stable arc, greater penetration, but a narrower weld.
2.2 Circle-drawing manipulation:
Continuously move the electrode tip in a circular motion while moving forward. There are two types: positive circle and inclined circle.
Positive circle manipulation is suitable for welding thicker workpieces in a flat weld, allowing the molten metal to reach a high enough temperature for gases such as oxygen and nitrogen to be released in the molten pool, and facilitating slag floating.
Inclined circle manipulation is suitable for flat and overhead T-joint and butt welding, helpful in controlling the molten metal to avoid dripping, and conducive to weld formation.
3. Arc Extinguishing
Inappropriate arc extinguishing action can result in an arc pit lower than the base metal at the end of the weld, leading to cracks.
Common arc extinguishing methods include:
3.1 Circle-Drawing Extinguishing:
Suitable for thick plate welding, but there’s a risk of burn-through for thin plates.
3.2 Repeated Arc-Breaking Extinguishing:
When reaching the end point of welding, extinguish and reignite the arc several times until the arc pit is filled. This method is suitable for thin plate welding, but not for alkaline electrodes.
3.3 Back Welding Extinguishing:
When reaching the end of welding, instead of extinguishing the arc, adjust the electrode angle appropriately, move it in the opposite direction, and then break the arc. This method is suitable for alkaline electrodes.
2. Tips for Welding in Various Positions
Here are some operating key points for welding in various positions:
1. Flat Welding
1.1 Initially, increase the inclination angle, and decrease it as the temperature rises.
1.2 Maintain the angle between the welding wire and the torch at about 90 degrees.
1.3 Keep the welding wire immersed in the molten pool, stirring it continuously.
1.4 During thin plate welding, the welding wire can move up and down.
1.5 At the end, slowly lift the torch to reduce the size of the rear molten pool.
1.6 Don’t move the electrode too slowly, otherwise, the slag will be too thick, obscuring the molten pool and making operation difficult.
2. Vertical Welding
2.1 Use a flame with a smaller rate for welding.
2.2 Strictly control the molten pool temperature, the molten pool area should not be too large, and the depth of the molten pool should also be small. The welding current should be 10-15% less than that of flat welding.
2.3 The torch should be tilted upwards at a certain angle in the welding direction, generally maintaining a 60-80 degree angle with the workpiece.
2.4 To control the molten pool temperature, the torch should move up and down at any time, giving the molten pool a chance to cool and ensure the appropriate heating of the molten pool.
2.5 A semi-circular transverse swinging plus arc lifting operation can be used.
3. Horizontal Welding
3.1 Use a smaller flame rate to control the molten pool temperature.
3.2 For thin plate welding, use the left welding method. However, the torch should also be tilted upwards, directing the flame towards the weld, using the pressure of the gas flow to prevent molten metal from flowing out of the molten pool.
3.3 Generally, the torch doesn’t swing transversely during welding, but when welding thicker workpieces, small inclined circle movements can be made.
4. Overhead Welding
4.1 Use a flame with a smaller rate for welding.
4.2 During operation, strictly ensure the fusion of the root on both sides of the groove, strictly control the size and temperature of the molten pool, and keep the molten metal in a viscous state to prevent it from falling.
4.3 The groove angle should be slightly larger than that of flat welding to ensure convenient operation. Pay attention to the operation posture and prevent burns from metal splashes and falling molten metal.
4.4 When welding the first layer of the overhead weld with a groove, the electrode forms a 90-degree angle with the sides of the groove and a 70-80 degree angle with the welding direction.
Use the shortest arc to make push-pull movements, the molten pool should be thin rather than thick, and ensure good fusion with the parent metal.
If the molten pool temperature is too high, the arc can be raised to slightly lower the temperature. When welding the remaining layers, swing the electrode transversely and stabilize the arc on both sides.