Knitweld, thermit welding, is a welding that employs molten metal to permanently join the conductors. The process employs an exothermic reaction of a thermite composition to heat the metal and requires no external source of heat or current. The chemical reaction that produces the heat is an aluminothermic reaction between aluminium powder and a metal oxide. It is the reaction occurring between copper oxide and aluminium powder (weld metal) creating molten superheated copper and aluminium oxide slag. When a spark first reaches the Knitweld metal causes the reaction within the weld metal, melting and separating the metals. The aluminium rises to the top of the connection creating slag leaving the copper to flow around the joint creating the actual weld.
The Knitweld is a permanent, maintenance-free connection that will not loosen over time or deteriorate with age. The connection’s current carrying capability is equal to or greater than that of the conductors being joined. In other words, there is no increase in resistance in an exothermically welded connection as there is in most pressure connections. Knitwelding has been shown to be the best choice where safety, reliability, current carrying capacity and longevity are critical.