The Research on Thermit Welding Materials

06 Apr.,2023


1. Research on thermit welding portion


Formula for calculation molten steel temperature in thermit portion


Initial temperature of reactant: the temperature of liquid steel increase by 0.6℃ for every 1℃ increase in initial temperature of reactant.

Proportion of additives: When the amount of additives increase by 1%, the temperature of molten steel decrease by 25.7℃.

Influence of FeO proportion :The temperature of molten steel decrease when the proportion of FeO in reactant ferric oxide increase.

Thermit reaction speed control method


2.Defective of sand mould

Research on sand mould



Adjustment of width design of sand mould bottom plate


3. Preheating Process

Adjust size of gap

The welding joint is 20mm and 22mm, the preheating temperature of rail bottom is low, high- temperature thermite hot molten steel cool rapidly at the bottom of the rail. And the aluminum hot molten steel at the bottom of the rail fails to melt the rail base material and solidifies, an unwelded joint is formed.

When the welding joint is 24mm~30mm, the end face of the steel rail to be welded can be heated to dark red by adjusting the preheating time, which can meet the requirements of the welding preheating temperature.

When the welded rail seam is 32~40mm, because there is a lot of thermite molten steel in the weld, during solidification and shrinkage, the alumite molten steel in the center solidifies too late, and the effective feeding of the riser cannot be obtained. In addition, the temperature of the molten steel is high, The amount of solidification shrinkage is large, so microscopic shrinkage is formed in the center of the weld.


Production of Thermit portion

Production of sand mould


The range of thermit welding rail slot is 23~30mm. When the rail slot exceeds 30mm, a 6m or 12m long steel rail must be equipped to weld the two joints.

The aluminothermic welding technology of wide rail slot rail can be welded directly when the rail slot is within a certain range.


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