Method for sealing a casting mould for aluminothermic rail weldings

A method for performing an aluminothermic welding process on components, with two mold halves, one upwardly open, which replicate a component profile in an area of a weld, the method comprising:

• closing slits present between facing surfaces of the components and wall sections of the two mold halves with a fireproof sealing compound that can be expanded thermally or chemically in order to seal a casting space of a casting mold, the sealing compound being an expandable substance comprising an intumescent material, wherein gaps between the wall sections are smaller on interior sides facing the casting space than on exterior sides, thereby resulting in a higher flow resistance toward the interior sides as compared to the exterior sides;
• and
• performing the aluminothermic welding process set up as a rail connection welding or repair welding operation of a railhead by:
• preparing a steel melt in a reaction crucible;
• and
• introducing the steel melt into the casting space.