The Thermite welding process produces coalescence of metal by heat and super-heated a liquid metal temperature from chemical reaction between aluminum and iron oxide with or without pressure.
The thermite welding process is having wax pattern it placed on around the work piece ends. The steel box (or) molding box placed around the wax pattern. The gap between molding box and wax pattern is filled the sand and rammed to gather.
The pouring of basin, riser, runner, gates and plug to drain wax are cut with the molding sand. The flame is connected through drain plug. The wax pattern are melt and drain out, also the weld part is connected through drain plug. The wax pattern are melt and drain out, also the weld part is preheated. The drain plug is plugged on sand.
Aluminum and iron oxide are mixture of Thermite and it combination of one part of aluminum and three parts of iron oxide. The mixture is ignited and it exothermic reaction. During exothermic reaction the filler metal obtained between aluminum and oxide. It generates more heat during the process.
Thermite reaction during process:
8AL + 3Fe3O4 → 9Fe + 4AL2O3 + Heat [719.3k, 3088⁰c]
The parts are clean and lined with gap (1 to 4mm) between the ends. The mixture is stored in crucible and ignited. If effective ignition needed, the mixtures are composed with highly inflammable barium peroxide powder and ignited using magnesium ribbon. It is Thermite reaction and generates heat temperature range of 3088⁰c.
During the reaction process aluminum has affinity to oxidation. The iron oxide leave from oxygen and combine to the aluminum, provide from of aluminum oxide. When the aluminum become the form of slag and floats. For pure iron is super-heated caused as Thermite steel. It is used to welding of steel.
The super-heated steel is contain with crucible is placed above the weld joint. It runs in to mold which is built around the part to be weld together.