THERMIT® welding processes

Using the Thermit® welding process, virtually all rails of widely varying profiles and grades can be joined together without gaps. Thermit® is composed of aluminium granules and iron oxide, which has a strong exothermal reaction after initial ignition. The high heat of the reaction makes it possible to produce liquid steel at up to 2,300°C without using external sources of energy, as a result of which the ends of rails can be welded together. We can therefore guarantee the secured connection of the rails in heavy-load and high-speed networks, while at the same time increasing travelling comfort and the lifetime of the track.

We offer the following processes:


Rapid welding process with short preheating time – Elite L25

  • Certified in accordance with DIN EN 14730-1
  • Simplified short preheating duration of two minutes
  • Safe use on higher strength rail classes (up to R400HT inclusive)
  • Optimised fatigue resistance properties
  • Suitable for use on flat bottom rails on operational tracks of all speeds and with high traffic volumes
  • Maximum track availability thanks to simple, quick and seamless use on site
  • High safety and robust design on the track
  • Very good economic efficiency
  • Sand or paste sealing can be selected
  • Suitable for all crucible types
  • Standard gap width 25 mm ± 1 mm
  • Casting moulds for wide gaps allow for welding from 40 mm to 50 mm and from 65 mm to 75 mm gap widths


Quick welding process without collar

  • This process with rising casting system and central gate has a short, profile-dependent preheating time of 3 - 6 minutes, offering extremely high suitability for use in the welding of flat bottom rails.

  • Smaller portion sizes and the use of one size of mould shoes for different profiles makes this a very economical process.

  • The standard gap width is 29 mm ± 1 mm.

  • SoW-5 is certified to EN 14730-1.


Quick welding process for flat-bottom rails

  • HPW is a novel, innovative welding process, and its scope of application is predominantly in the heavy load sector.

  • The special feature of the HPW process is in a special alloying system that makes it possible to create a hard, wear-resistant weld deposit in the head and a soft, ductile weld deposit in the base. This gives the resulting weld optimum mechanical properties.

  • The HPW alloying concept makes this welding process particularly suitable for welding head-hardened rails. However, because HPW can also be used without this alloying concept, soft grades of rail (e.g. R260) can be welded just as easily.

  • Specially marked plugs with an integrated container are currently available for three different levels of hardness (350 HB, 370 HB, 400 HB)

  • HPW allows for unique, simplified and cost-saving logistics.

  • The HPW process is a Thermit® welding process with rising casting system and central gate, for welding flat bottom rails.

  • The standard gap width is 29 mm ± 1 mm and the preheating time is 3.5 minutes.

  • HPW is used only with the single use crucible and with luting sand.

  • Within Europe, HPW is used in mining railways (heavy-load railways in Sweden and Norway), but it is also used in the heavy load sector throughout the world.


  • THR is an aluminothermic process for resurfacing flat bottom rails.

  • THR is a high-quality alternative to the conventional method of electric deposit welding.

  • This welding process can be used to rectify localised faults in the rail.

  • The benefits of THR include cost savings and a reduction in life cycle costs.

  • The geometry of the groove cut into the rail head for the THR process determines the size of the fault that can be repaired. The groove geometry corresponds to a segment of a circle (depth approx. 25 mm, length approx. 75 mm). The size of the groove depends on the profile.

  • THR is used only with the single use crucible.

  • The preheating time is between 1.5 and 3 minutes, depending on the profile and the process parameters selected.

  • The technical development of the process is completed. Approvals and launch onto the market are yet to come.


Quick welding process for grooved rails

  • SRZ is a welding process with falling casting system, central gate and extended preheating time for grooved rails. The expansion gap is cast in its entirety, with the exception of the groove, and the whole cross-section of the rail ends is fused.

  • The SRZ process is largely independent of the user, in contrast to arc welding. This leads to improved reliability of execution in comparison, and hence to improved operational reliability on the track.

  • The standard gap width is 25 mm ± 1 mm.

  • SRZ is used internationally by all large and small municipal transport operations.


Rapid welding process, crane rail

  • SKS is a rapid welding process with rising casting system, central gate and extending preheating times for crane rails and can be used with or without base bead.

  • Rapid execution is possible even at great heights despite restricted space and working conditions.

  • The process can be used on all crane rails including the A150 profile.

  • Compared with arc welding, the welding process is largely independent of the user and has a greater degree of automation.

  • The standard gap widths are 23 mm ± 1 mm and 25 mm ± 1 mm (depending on the profile).

  • The preheating times are dependent on the profile.

  • SKS is executed with sand sealing. Only the single use crucible is used.

  • The SKS process is executed using 3-part moulds as a supported joint.

  • SKS is used nationally and internationally on tracks and systems belonging to industrial companies.


Are you interested in our range of products and services or have questions? Please contact us. We will be glad to help you.