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Resistance welding uses heat and pressure to bond materials, including metals and plastics. Copper electrodes inject heat, which can be controlled by the operator. Pressure is also necessary for cohesion. Spot and seam welding are examples of this process, with different electrode shapes used for each. Different types of resistance welding include fusion bonding and solid state bonding.
Resistance welding refers to processes that use electrically generated heat and pressure to create bonds between materials. Such processes usually involve joining metals, but the term resistance welding can also be used in bonding plastics. This type of welding is considered quick and efficient when done correctly. Errors during this process can cause problems such as cracks, warped surface appearance and cavities.
Machines normally used for resistance welding use copper electrodes. These are used to inject materials with electrically generated heat. The machine operator can control the amount of heat and the heating period. After enough heat has been injected, the materials can be cooled on the outside while the inside melts are allowed to cool more gradually. When this stage is complete, bonds should be formed.
Generally, the higher the melting point of the metal, the less heat is needed. A metal that conducts heat well, such as aluminum, requires more heat for resistance welding. This is because the heat tends to spread through the material instead of being trapped at the melting point.
Resistance welding also requires strength. Pressure is used to hold the layers of metal together as they cool. If this is not done, cohesion may never occur. The necessary pressure is usually applied by the machine that supplies the electric current. The machine operator can also usually control the amount of pressure.
Spot welding is an example of a resistance welding process. It can be used to connect multiple layers of metal without filler materials. Because copper is an excellent conductor of heat, pointed copper electrodes are used to pin the metal together and send electric currents through them.
Many metals do not conduct heat well. The heat created within the layers of the project is then trapped and results in melting. The pressure of the electrodes then causes the layers to connect.
Seam welding is similar to spot welding. Instead of making ties at various points, however, this process allows for the creation of long, continuous ties. Round electrodes are used in this process to roll over the outer parts of materials, energizing them with an electric current and applying pressure.
There are several types of resistance welding. Fusion bonding involves materials bonding because their melting points are reached, allowing the molten materials to mix together. A solid state bond, in contrast, is one that results in minimal melting.
