“Exothermic” is a chemical term used to describe a reaction that produces heat.
Exothermic welding, also known as “thermit welding” or “aluminothermic welding” is a welding process for permanently joining materials (usually copper conductors) that employs an exothermic reaction. The exothermic reaction requires no external heat or a power source. All that is required is a spark to initiate the reaction.
The KingsWeld Process
The KingsWeld exothermic process is a simple, self-contained, efficient way of welding copper-to-copper or copper-to-steel.
Each connection uses a KingsWeld weld metal which, when ignited, creates an exothermic reaction between copper oxide and aluminium powder.
The connections are produced inside a graphite mould, specifically designed to suit the size of conductors to be welded as well as the specific joint configuration.
Each connection requires a specific mould designed to suit the joint configuration and conductors being used. Each mould type requires a specific weld metal size. This can be found in our weld metal selection table HERE.
Once the correct mould and weld metal have been selected, the process is simple and straightforward.
The conductors are positioned in the graphite mould. A steel retaining disc is then inserted into the mould before any weld metal is added. Only after the disc is in place and properly seated can the main weld metal (under the green cap) be poured into the reaction crucible. The ignition temperature of the main weld metal is approximately 1000°C. This is difficult to achieve and so we use a starter powder to start the exothermic reaction, this is contained under the red cap. The starter powder is similar to the main weld metal, but finer, allowing ignition at around 450°C (through using the spark from a flint ignitor).
The resultant exothermic reaction produces high temperature molten copper (in excess of 2000°C) and aluminium slag.
The molten copper melts the steel retaining disc and flows down the tap hole into the joint cavity. In doing so, the molten copper melts and welds the conductors into a solid homogenous joint.
The whole process takes no more than a few seconds. The aluminium oxide produced stays on top of the joint and is easily removed.