Arc welding is an autogenous welding, so the assembly of similar parts by fusion, with a filler metal, here constituted by the electrode. The heat required for melting is provided by an electric arc produced between the parts and the electrode, and giving a temperature of 4000 to 4500°. The high intensity of electrical power required is provided by the welding machine: generator of current, it transforms that of a normal network, with voltage of 220V and intensity of 15 A, in current of weak tension (45 V) and strong intensity (75 A). Before buying an electrical soldering station, make sure that your installation (meter and circuit breaker) can withstand the intensity demand of the unit.
- Welding machine
- Mass clamp
- Protective gloves
- Hammer to prick
- Wire brush
- Preparation of equipment and welding
- Operations after welding
- Complete flat welding
Preparation of equipment and welding
1. The electric soldering station, connected to the mains, has several essential "accessories": a ground clamp, an electrode holder (these two elements being integral with the apparatus), a hammer to stitch welds, a mask protection (with special tinted glass to watch the arc safely, and white glass to protect the first, very expensive), electrodes of different diameters.
2. Insert the bare end of the electrode (metal rod with melting film) into the electrode holder head.
3. After having set the voltage selector switch on the device to the 220 V mark (this item being delivered with two possible voltages: 220V and 380V), select the intensity corresponding to the work to be performed and the electrode used. Carefully adjust this setting
4. Place on the worktop a "marble", cast iron plate of good dimensions. Put on the two bars to assemble. Attach the ground clamp to the marble in a clean location with no rust or paint to act as insulation. After putting on the protective gloves, hold the mask in front of your face with one hand. Before performing the welding itself, it is necessary to make pointing to immobilize the parts, as for the welding torch. Lightly rub the end of the electrode, 1 to 2 cm, on the workpiece: the sparks that appear indicate the beginning of the arc. At this point, move the electrode slightly away from the workpiece (2 to 5 mm): the arc is formed. You can also strongly hit the end of the electrode on the metal, and let it bounce to provide the interval necessary for the formation of the arc. But this technique is a little more delicate. To achieve the weld bead, you have to work with regularity. Place the electrode perpendicular to the metal, a little inclined in the direction of progression.
Operations after welding
5. After allowing the weld bead time to cool slowly, remove the film of dirt, which is called slag, covering the surface. Use a prick hammer.
6. After clearing the weld, clean it by rubbing it with a wire brush until it is shiny. The surface of a correctly performed weld (progression at normal rhythm and arc and of constant length) is regular: uniform wrinkles, equal width of joint.
Complete flat welding
7. Flat welding is the easiest to perform. Place the plates to be assembled on the marble. The space between them varies according to the thickness of the parts to be welded. Space them 1 to 3 mm if they are 1.5 to 4 mm thick; place them edge to edge if their thickness is less than 2 mm.
Caution: too wide a gap may give a hollow joint.
8. Attach the ground clamp to one of the plates: make sure that the metal is clean, free of rust and paint, so as to prevent the flow of current.
9. Practice fastening welds, small cords 6 to 9 mm long, to secure the plates together. It is possible to make the cord in narrow or wide passes. The first method is to perform the welding by moving the electrode along the joint, without lateral movement. To execute a wide pass, it is necessary to carry out a lateral scan in zigzag at the same time as the advance electrode. This "scan" must have a maximum amplitude three times the diameter of the electrode. There must be a pause at each end of the movement to avoid the formation of gutters, that is to say, furrows dug along the banks of the weld seam.
10. Form the cord with the greatest regularity possible. Maintain a constant arc length by lowering the electrode holder as the electrode melts; move smoothly. A too slow progression associated with a too high intensity produces a too curved cord, presenting risks of cracks. Too slow a speed and too large a gap give a collapsed cord, not welding properly parts. On the other hand, the high heat generated by the arc submits the metal parts to a heating that makes them expand. On cooling, they shrink and some deformations can occur. Before soldering, spread the plates a little more at one end than the other: this preliminary correction avoids the clamping effect, the most common deformation.
11. Carefully remove the slag with the prick hammer after allowing the weld bead to cool.
12. Rub the weld with a wire brush to clean it thoroughly. Cleared of all slag, it must have a shiny appearance.
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