Page 1 - My Report

A Brief understanding of

The manufacturing of Thermit Portions

- A.Karthik Roy (JE/Track)

On Indian Railways, Alumino –Thermic welding with short pre-heating process by using
high silica sand mould (CO2 dried) is being followed at present, for welding of rails of different
chemistry and sections.

 IRS-T-12-2009 laid down the specifications of Flat bottom Rails (viz. Quality of steel,
Manufacturing process, Chemical compositions , tests etc).
 IRS-T-19-2012 laid down the specifications for Fusion welding of Rails by Alumino-
Thermic Process (viz. Technical requirements of Thermit Portions, Approval of portion
manufacturers, Training of welders and supervisors etc).
 “Manual for Fusion welding of Rails by Alumino-Thermic Process” outlines the
method of welding , precautions and steps to be taken for achieving satisfactory weld.

(SKV is the short form of German Phrase “Schweiss- verfahran mit Kurz Vor wa fmung”
when translated into English reads as “Short Pre-Heating process”).

The quantity of mixture required for welding one rail joint shall be called a “Portion”.

Alumino-Thermic reaction

Fe2 O3 + 2Al ---> 2 Fe + Al2O3 (Slag) + 181.5 K.Cal

As per IRS-T-12-2009 specifications, chemical composition of rail steel not only consists
of Fe (Metallic Iron) but also contains traces of other elements like Carbon (C), Manganese (Mn),
Silicon (Si), Sulphur (S), Phosphorous (P), Vanadium (V), Molybdenum (Mo), Aluminium (Al),
Chromium (Cr), Copper (Cu), Nickel (Ni) etc. Hence the weld metal prepared from the portion
should also consist of these elements as per specified limits.

 The main ingredients of the portion are
1) Mill Scale ( By-product of the manufacturing of rails)
2) Aluminium powder
3) Steel Chips
4) Calcium Flouride (also known as Flourspar)
5) Ferro Manganese

6) Ferro Vanadium (can be replaced by Ferro Molybdenum as per IRS-T-19-2012 para 4.1)
7) Silicon Carbide

Standard specifications (like composition, particle size, quality/Acceptance tests etc) of
each of these ingredients for use in manufacturing of Alumino –Thermic Portions are developed
by Thermit Portion Plant/LKO and approved by RDSO. (enclosed as annexure-I)