The melting of the applied metal intended for the assembly of elements is carried out only due to the heat generated by the electric arc that occurs and is maintained between the electrode rod and the workpiece.
For protection, an inert gas is used, which does not participate in the melting of the metal.
The deposited metal and the base metal are different. It's heterogeneous (heterogeneous) a compound in which the deposited metal resulting from the melting of the electrode adheres by a wetting effect to a surface that does not undergo melting. In this case, neither mutual dissolution of the two metals nor metallurgical transformations occur.
As an electrode, copper wire, copper-aluminum, copper-lead or copper-silicon wire with a diameter of 0.8, 1.0 and 1.2 mm is used.
Contact welding. The principle of contact welding is to obtain a melting point of a certain diameter, which depends on the thickness of the sheets to be welded
Electric resistance welding uses the heat input resulting from the passage of a high voltage current and requires the application of pressure to the parts to be welded.
Welding on one surface only (called welding-core) does not provide a reliable connection of parts, and its use in body repair is prohibited.
To avoid power surges causing abnormal welding conditions, do not overload lines, do not work with wires of insufficient diameter, and do not place electrical power sockets too far from the contactor.
A welding machine operating at insufficient supply voltage cannot provide high quality welding.
In order to ensure the correct power supply of welding installations, it is imperative to have a power supply circuit with wires with a cross section of 6 mm2 or 10 mm2, if the chain length exceeds 50 m.
The diameter of the electrode tip must be selected depending on the thickness of the sheets to be welded (diameter = thickness x 2+3 mm).
It is necessary to choose electrode holders so that the pliers pass freely through them, which at the same time have the shortest length.
Poor adjustment can cause warping or burn through of welded sheets and result in poor weld point strength.
The electrodes must be even, correctly pointed and not have tint colors.
Attention! Burnt electrodes must not be used, as they are very poor conductors of current and therefore do not provide the correct welding point.
Before welding, check on pieces of sheets of the same thickness and in the same order in which they are to be welded.
Check the strength of the weld points before determining the amperage and pressure required to obtain a high quality weld (too low amperage or pressure will cause parts to stick rather than weld).
When separating welding by tearing (with clamp) the resulting weld point will remain on one of the sheets (thicker), and on the other sheet there will be a through hole.
Welding is of poor quality if there is no welding point when the sheets are separated (in this case, sticking occurs, not welding) or the weld point diameter is less than the minimum required value.
Separation points (nuclei) shall have a diameter of 4 mm for a reference sheet with a thickness less than 1.5 mm and a diameter of 6 mm for a reference sheet with a thickness greater than 1.5 mm.
The following are the conditions that determine the quality of contact welding:
- cleanliness of parts;
- pressing time, which should be large enough;
- current value;
- current passage time;
- sheet compression force;
- forging (compressed cooling time);
- electrode tip diameter;
- sheet clamping perpendicularity;
- interval between welding cycles (plant cooling).
Visual control of the welding point consists in checking that the points do not have burns, through holes and frozen spatters of metal, have a slight bulge (trace depth from 0.2 to 0.4 mm) on the surfaces of both sheets for standard points and do not cause sheet deformation
To avoid any problems in the future, after repairing or replacing one of the body sheet elements, restore high-quality protection on all surfaces. This method makes it possible to obtain element characteristics identical to those of a new element, and ensures the quality and preservation of the corrosion guarantee for the repair carried out.
Use a special certified post-weld compound between panels to be joined.
Attention! Comply with safety and fire safety requirements. When welding galvanized parts, work in a ventilated area.