Overview
ISO 23300-2:2025 - Railway infrastructure - Rail welding - Part 2: Aluminothermic welding - specifies requirements for aluminothermic (thermite) rail welding used to join rail ends (butt welding). The standard covers the approval process for welding procedures, laboratory testing, qualification of welders and contractors, and acceptance criteria for aluminothermic welds installed in track. It applies to new vignole rails of the same profile and grade in the 43 kg/m to 75 kg/m range. Note: conformity with this standard does not automatically guarantee suitability for every track or traffic condition.
Key topics and technical requirements
The standard defines technical and procedural topics essential for consistent, high-quality aluminothermic welds:
- Approval process: Identification and documentation of welding processes, submission of process manuals, drawings, chemical analysis ranges and tolerances, and procedures for initial approval, extension and re‑approval after changes.
- Laboratory tests: A structured testing scheme that includes visual examination, hardness measurement (running surface and heat‑softened zone), slow‑bending and past‑the‑post fatigue tests, internal examination (ultrasonic testing, sectioning and fracture face assessment), microstructure and chemical analysis.
- Inspectable features and geometry: Requirements for weld alignment, collar matching, straightness and overall geometric acceptance of welded rails in track.
- Weld integrity and NDT: Non‑destructive testing procedures to assess weld soundness and fusion zone dimensions; normative annexes provide procedures for ultrasonic testing, hardness measurement and heat‑softened zone measurement.
- Qualification and oversight: Criteria for recognition and approval of welders, example diplomas/permits, contractor approval, traceability, and audit requirements.
- Documentation and traceability: Mandatory records for approvals, test reports and in‑track acceptance inspections.
Applications and who uses this standard
ISO 23300-2:2025 is intended for organizations and professionals involved in railway track welding and maintenance:
- Railway authorities and infrastructure managers establishing procurement and acceptance criteria
- Welding contractors and service providers seeking process approval and contractor qualification
- Test laboratories performing metallurgical, mechanical and NDT assessments of aluminothermic welds
- Welders, trainers and inspectors responsible for field welding, certification and weld acceptance
- Designers and maintenance planners assessing compatibility of welding methods with track specifications
Benefits include improved weld quality control, enhanced ride comfort and reduced maintenance through standardized aluminothermic welding practices.
Related standards
- ISO 23300-1:2021 - General requirements for rail welding processes (refer to this for requirements common to FBW, GPW, ATW, EAW)
- Other parts of the ISO 23300 series covering alternate welding methods and general rail welding guidance.
