If the welding portion (Thermit) is activated by an inflammable bar to produce the conversion, the oxygen is drawn away from the iron oxide by the aluminium. Thus, it will be converted into aluminium oxide and releases the required iron.
Metal oxide + aluminium oxide -> metal + aluminium oxide + heat = Thermit
The raw materials are each mixed separately, carefully and stored in silos. The various components are removed from these silos, via automatic weighing scales, according to recipes mechanically mixed with one another and filled into portion bags.
The ignition sticks:
The ignition sticks activate the conversion of the Thermit portions into iron. The sticks should not be stored with the Thermit portions. The ignition sticks could self-ignite at a temperature of 200°C, and that is why storing the sticks in the clothing of the welder is prohibited (risk to life).
You can find suitable specialist literature to the topic here:
The Basic Principles of Mechanised Track Maintenance
This book is dedicated to the many people involved in the day to day planning and performance of track maintenance activities. Providing a practical approach to everyday challenges in mechanised track maintenance, it is not just intended as a theoretical approach to the track system.
Railways aim at transporting people and freight safely, rapidly, regularly, comfortably and on time from one place to another. This book is directed to track infrastructure departments contributing to the above objective by ensuring the track infrastructure’s reliability, availability, maintainability and safety – denoted by the acronym RAMS. Regular, effective and affordable track maintenance enable RAMS to be achieved.