The heavy metal industries many times make use of the variant welding methodologies in the manufacturing of different components. Starting from the automotive industry, it expands up to aerospace, manufacturing, railroads, shipping and aerospace. Depending on many parameters the type of welding may change in different applications. The basic form of forge welding was the only method till 19th century, and later as the technology developed, many innovative, cost-effective and dependable welding processes came into action. One of the most prominent welding methods is flash butt welding.
Basics
Flash butt welding is basically a resistance welding process in which coalescence is produced by the heat obtained from the resistance of a metal. The application of required pressure where the weld joint has to be made is another important factor to consider. In an electric circuit, the metals to be joined are placed as the resistive elements and electricity will be passed through the circuit. The current is of sufficient magnitude to produce flashing actions between the adjacent pieces of metal. The metal is thereby heated to the fusion point and the weld is consummated by the application of sufficient upset force.
Flash butt welding in railways
While making the railway line joints, flash butt welding is mainly used. The shape of the rail is found to be very irregular at the joints in terms of material distribution. During the welding process flashing occurs and the metals get melted but the cooling process will be uneven across the cross-section. As the material concentration is high on the railheads, cooling may occur very slowly in this portion. But the other parts like foot and base cool down immediately. As a result depression of the rail may appear on the welded area. To avoid this raised end welding method is used so that after the whole process the level will be accurate.
Parameters to be considered
- Welding current
The proper application of current only will give apt results. For flash welding and all, above 12 KA current is used.
- Upset force pressure
The pressure which is applied before the welding process and maintained throughout the operation is the upset pressure. Special equipment is used to provide this pressure.
- Welding time
The flash time and upset time can decide the quality of the welds. The flash time is the duration of the arc and the upset time is the time for which the two pieces have to be pressed together.Normally the upset time should be greater than the flash time. The flash time should be accurate, since too low or high times may affect the quality.
Advantages over other welds
- Provides strength almost equal to parental metal.
- Very lightly affected by corrosion
- Fewer failure rates
- Defect-free welds with supreme quality.( porosity, inclusions, lack of fusion etc are eliminated)
Conclusion
The welding process is used widely for the joining of two or more metals and the railways have used it to the core. The Flash welding promises the high yield joints without any filler material and that makes it privileged one.
