Residual stresses in thermite welded rails: significance of additional forging

Abstract

The aluminothermic welding (ATW) process is the most commonly used welding process for welding rails (track) in the field. The large amount of weld metal added in the ATW process may result in a wide uneven surface zone on the rail head, which may, in rare cases, lead to irregularities in wear and plastic deformation due to high dynamic wheel-rail forces as wheels pass. The present paper studies the introduction of additional forging to the ATW process, intended to reduce the width of the zone affected by the heat input, while not creating a more detrimental residual stress field. Simulations using a novel thermo-mechanical FE model of the ATW process show that addition of a forging pressure leads to a somewhat smaller width of the zone affected by heat. This is also found in a metallurgical examination, showing that this zone (weld metal and heat-affected zone) is fully pearlitic. Only marginal differences are found in the residual stress field when additional forging is applied. In both cases, large tensile residual stresses are found in the rail web at the weld. Additional forging may increase the risk of hot cracking due to an increase in plastic strains within the welded area.

Rail degradation due to thermite weld discontinuities: Field experience

“…Indeed, 'ALFONS' welding technology is an automated thermite welding process applying an additional forging load at the end of the process in a forging step. Josefson et al studied numerically this process [31]. The FE-simulations showed that the addition of forging load induces an increase in plastic strains within the welded area.…”

Thermal Analysis and Pyrolytic Behavior of Bimetal and Double Oxidant Thermite Al/Mg/MoO3/CuO

“…Unlike other energetic materials, thermite has the characteristics of high adiabatic temperature, high combustion efficiency, high enthalpy of reaction, good safety, flexible formula and so on, so it has an extensive application prospect. In the civil field, thermite is generally used in welding [5], thermal batteries [6] and metallurgy [7]. In the military area, thermite is widely used as an additive in ammunition destruction [8], infrared bait [9], solid rocket propellant and high-energy charge [10][11].…”

Enhancement of thermal properties of Al/MoO3 thermite by electrostatic spraying

“…The thermite stands out due to its excellent combustion efficiency, high energy‐releasing rate, and high reaction exothermic enthalpy, which catches the attention of researchers. Thermite has been widely used in gas generator, 3 welding, 4 ammunition destruction 5 and high‐energy additives in propellants 6,7 …”

“…The thermite stands out due to its excellent combustion efficiency, high energy-releasing rate, and high reaction exothermic enthalpy, which catches the attention of researchers. Thermite has been widely used in gas generator, 3 welding, 4 ammunition destruction 5 and high-energy additives in propellants. 6,7 The thermite composed of metal oxide and metal powder possesses unique chemical properties, which mainly is ascribed to the nature of its components.…”