How does exothermic welding contribute to the electrical conductivity of joints?

Exothermic welding significantly contributes to the electrical conductivity of joints due to the high-quality bond it creates between the materials being welded.
Exothermic welding relies on a chemical reaction between a metal powder (usually aluminum) and a metal oxide (often copper oxide) that produces extremely high temperatures—typically around 2500°C (4500°F). This intense heat melts the base metals at the joint, and as they cool, they form a solid bond. The welding process creates a molten metal that is highly pure and free of impurities, which is essential for maximizing electrical conductivity.
Unlike traditional welding methods, where heat is applied externally to the joint, exothermic welding uses a localized reaction at the weld site, which minimizes the heat-affected zone (HAZ). This helps to preserve the conductive properties of the metals being joined, especially in copper and aluminum, which are known for their excellent electrical conductivity. The lack of HAZ means the electrical properties of the materials are not degraded by heat distortion or grain structure changes, ensuring optimal conductivity.
The exothermic reaction burns away any contaminants (such as rust, dirt, or oxidation) at the weld site. This results in a very clean and uniform bond between the metals. The purity of the joint enhances the electrical flow through the connection, as impurities often act as resistors and can cause voltage drops or overheating in electrical applications.
The molten metal that solidifies in exothermic welding creates a crystalline structure with minimal porosity and a strong bond between the two conductors. This structure ensures low electrical resistance at the junction, which is crucial for efficient electrical transmission. In particular, copper-to-copper or aluminum-to-copper joints made using exothermic welding have some of the lowest resistance levels compared to other methods, making them ideal for high-current applications.
Traditional soldering or brazing methods often involve flux materials that can leave residues behind, which may increase electrical resistance or cause corrosion over time. Exothermic welding, on the other hand, does not require any flux or solder, eliminating these potential issues and ensuring a cleaner, more durable, and more conductive joint.
Exothermic welding creates permanent, high-strength connections that are resistant to wear, corrosion, and mechanical stress. In electrical applications, such as railway electrification or power transmission systems, this durability is crucial to maintaining consistent electrical conductivity over long periods of time, even under harsh environmental conditions.
Exothermic welding enhances electrical conductivity by creating high-quality, impurity-free, low-resistance joints with minimal heat distortion, making it an ideal method for electrical connections in industries where efficient power transmission and reliability are essential. The purity of the welded joint ensures that electrical flow is not impeded, allowing for optimal performance in critical applications such as railroads, power lines, and electrical grids.