Flash welders use resistance welding to connect parts, where energy transfer is provided by the resistance heat generated by the parts themselves. The components are placed end to end in the entire joint area. Various cross-sectional sizes and complex shapes can be connected. When applying the flash voltage, clamp the parts to be joined and slowly put them together. The process can be manual, but most flash welders are automatic or semi-automatic. If the contact between the components is small, the current density is high, the material resistance will be heated in the spray of molten particles, melted and blown out from the joints, thus having a unique flashing effect.
This flash evaporation caused by the flash welder will gradually introduce heating and softening areas at the end of the module while eliminating oxides and contaminants at the interface. After the preset length of the base material is "burned", forging force is applied to the part to strengthen the joint. In this way, forged butt welds can be made without any molten metal remaining in the joints.
How a Flash Welder works?
Flash welders use a weld joining process to combine two separate parts. The work acts as an electrode and the entire section is welded. The parts are clamped and brought together and a current is applied. The current creates an arc between the workpieces and heating and ejection begins. The force is applied. The parts come together. The connection of parts is forged to the desired quantity. The part is cooled and the force is removed. The resulting arc weld has a weld spout around the area of the weld that is typically mechanically removed. The resulting welds of flash welders are very strong and impermeable to liquids. Rims are manufactured in this way and are very reliable. Rims do not leak air in our cars and trucks. The term "flash welding" is quite self-describing - the phenomenon of "flashing" occurs during the process.
Heat is generated in the arc welding process through the contact surface resistance, not the contact resistance, as in the butt welding process. While butt welding is a one-step operation, arc welding is a two-step process. The first step is to flash the action. Current to the workpieces cause flickering or arcing at the interface of the two ends of the material touching. The flickering increases until the materials are brought to a plastic state. This flashing operation creates a heat affected zone very similar to a butt weld. When the area plasticizes and reaches the right temperature, the second stage of the operation begins - upsetting or forging. Thereafter, the two ends of the workpieces are joined together by the flash welder with a very high force sufficient to cause swelling of the material. This pushes the plastic metal along with most of the debris out of the joint.
A Comparison of Flash Welders and Butt Welders
The smooth, clean surfaces of the workpieces are not as critical in the flash welding process as for butt welding, as the flashing action burns away irregularities in the weld surfaces. This allows the operator to combine a wide range of materials with a flash welder. Items such as wide, thin sheets of cloth; pipes; forgings; and ferrous and non-ferrous materials can be successfully welded. In other flash welder applications, flash or slag may be ejected for disposal. Upset under the slag is solid metal, similar to a butt weld, and requires cutting, trimming, or deburring operations to remove. The downside to this process is the flash itself. The operator and the surrounding area must be protected and smoke and fumes must be removed. The resulting slag particles accumulate around the surface of the machine and frequent cleaning is necessary.
As with other resistance welding processes, the technology is rapidly changing the use of both butt and flash welds. The continuous development of control systems, AC and DC power supplies, advanced hydraulics, and servo valves has improved both processes. At the same time, this advanced technology has widened the range of applications that can be performed. Due to the variety of products and materials that can be welded by flash and butt welders, each application must be assessed individually. The production requirements, media, cleanliness, and aesthetics of the weld itself play an important role in selecting these two resistance welding processes.
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