Flash Butt Welder

What is the flash butt welder?

The flash butt welder is a type of welding machine that applies flash butt welding to forge two pieces of metal into one. The flash butt welders are the welding machines for automated welding process which are used primarily for welding rails. The flash butt welding technique that a flash butt welder applies is actually a combination of two welding methods: the flash welding and the butt welding.

Butt welds or butt welding refers to the welding method that two pieces of metal are joined in the same plane. The butt welding is a welding process that does not require much preparation and it is best applicable for welding thin metal sheets with a single pass. Because of its ease of preparation, the butt welding is prevalent in automated welding processes. The butt welding is a kind of resistance welding process.

The flash welding is another common type of resistance welding process. During a flash welding process, the flash is produced. The flash welding is a two stage process. The first stage is the flashing action and the second stage is the forging action. Welding with this process, the interface surfaces of the two metal pieces do not have to be smooth and clean because the flashing action burns away irregularities at the surfaces.

Combining these two resistance welding methods, the flash butt welders are considered the most efficient and reliable welding machines for joining rails together because the automated welding process performed by this machine has the lowest failure frequency. To forge the short rails into a longer section, the welding process is carried out directly on the track.


Welding Basics

Welding is a process of joining two pieces of metal together with heat. The joining process is called the fabrication. The principle of fabricating two pieces of metal together is simple: to melt the welding surfaces of the two metal pieces and contact them until they are forged into one and cooled down. To melt the welding surfaces, heat is needed. The heat in the welding process can be provided either electrically or by gas torch.

In addition to the heat, a welding process sometimes involves other components to fulfill the task. For example, two metal pieces are fabricated together by melting the welding surfaces and put them together in some welding processes. Yet, in some other welding processes, a piece of welding material may be needed as the agent in between the two metal pieces so that the task can be done.

In the welding process which a flash butt welder or the flashing welding method is involved, the heat is provided electrically. While the metal welding can be used in structural work, general machine repair work, manufacturing, or other industrial applications, the flash butt welding machines are used primarily in joining rails. There are multiple types of welding processes that can be performed for particular purposes.


Resistance welding

Both flashing welding and butt welding is categorized into resistance welding. The resistance welding refers to fabricating two pieces of metal by applying not only heat but also pressure within the process. The heat is provided mainly by passing electric current for a given period of time through the welding surfaces to be joined. One of the pros that resistance welding has is that no intermediate material is required to bond the two metal pieces together.

In a resistance welding process, the heat for welding is obtained by the resistance to the electric current between the two surfaces to be welded, and hence the name. To obtain the sufficient amount of heat to melt the metal pieces, the metal shall be exposed to the heat as well as the pressure for a controlled amount of time.

To pass the electric current to the welding surfaces, the welding electrodes are needed. Serving as the key component to release the current, the electrodes are typically made from copper based alloys because it has a superior conductive property. Since the intermediate material is not involved in resistance welding, the welding process is rather cost-effective. The flash butt welder for joining rails is a type of resistance welding machine.


Butt welding vs flash welding

Butt welding is one of the earliest forms of resistance welding. Both butt welding and flash welding applies electric current and pressure to weld metal pieces. However, the amount of pressure and current is given differently in these two types of resistance welding. The butt welding is a single stage operation which exerts pressure to put the two pieces of metal together first and then applies the current to heat the contact area to forge the two surfaces together. During this process, the electric current and the pressure to fabricate the metals together are not changed and the clean welding surfaces are required in butt welding.

On the other hand, the flash welding is a two stage operation which includes the flashing action and the forging action. In the flashing action, a flashing or arcing is produced by the current across the interface of the two metal pieces. The heat increases until the two pieces reach a plastic state. Once the area becomes plastic and a proper temperature is reached, the forging action starts. A force is created in the second stage to force the two pieces together. The clean surfaces are not required since the impurities or irregularities at the welding surfaces are burnt away during the flashing action. As the welding technology has advanced, these two types of resistance welding are more commonly applied industrially today.

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