Flash butt welding consists of bringing two rail ends together and generating an arc which heats the metal. Using hydraulic pressure the rail ends are then forged together. This entire process is automated with the rail ends handled by a portable weld head. Because it is completed so quickly, the heat affected zone is minimized. Parent metal is fused to parent metal.
In thermite welding, the steel obtained by combining iron oxide with aluminum is cast at over 2000°C in a mold matching the rail profile. The cast material bonds the two rails together.
Each method has its own advantages and will depend on your application and time constraints. A representative from Simmers Crane Design & Services can meet with you at your facility to see which method best suits your needs.