Flash welding

Flash welding is a type of resistance welding that does not use any filler metals. The pieces of metal to be welded are set apart at a predetermined distance based on material thickness, material composition, and desired properties of the finished weld. Current is applied to the metal, and the gap between the two pieces creates resistance and produces the arc required to melt the metal. Once the pieces of metal reach the proper temperature, they are pressed together, effectively forge welding them together.^[1]

According to a study published in Materials and Design, several parameters affect the final product. Flash time is the time that the arc is present. Upset time is the amount of time that the two pieces are pressed together. Flash time needs to be long enough to sufficiently heat the metal before it is pressed together. However, if it is too long, too much of the base metal begins to melt away. The upset time is critical in creating the desired mechanical properties of the finished weld. During the upset, any impurities in the base metal are pressed out creating a perfect weld. If the upset time is too short, some of the impurities may remain in the base metal creating a defective weld. The upset time is also crucial in the strength of the finished weld because it is during the upset that coalescence occurs between the two pieces of metal. If the upset time is too short, the two pieces of metal may not completely bond.^[1]

Very often flash butt welding is controlled by distance rather than time such that the flashing would occur for a pre-determined length, say 5 mm, before the upsetting cycle starts. Upsetting may then also be controlled by distance. A parameter would be set to apply the upsetting force until a certain distance has been upset. It is generally the upsetting distance that is more important than the upsetting time.

At the end of upsetting there is commonly a 'hold time' during which the joint is held still to allow the joint to cool and the two pieces of metal to completely bond.

Los ferrocarriles utilizan la soldadura por chispa para unir secciones de rieles de vía principal y crear rieles soldados largos (LWR) en fábrica o rieles soldados continuos (CWR) en la vía, que son mucho más lisos que los rieles unidos mecánicamente porque no hay espacios entre las secciones de riel. El riel más liso reduce el desgaste de los rieles, lo que reduce la frecuencia de las inspecciones y el mantenimiento. ^{[ 2 ]} El riel soldado continuo se utiliza especialmente en líneas ferroviarias de alta velocidad debido a la suavidad de la cabeza del riel.

La soldadura por chispa también es beneficiosa porque permite unir metales diferentes, incluidos los metales no ferrosos . Esto permite soldar eficazmente desvíos y cruces, que generalmente están compuestos de acero con alto contenido de manganeso , a rieles de acero al carbono mediante un inserto de acero inoxidable , manteniendo intactas las propiedades mecánicas deseadas tanto de los rieles como de los cruces. ^{[ 3 ]} La capacidad de un solo proceso para soldar muchos metales diferentes, con simples ajustes de parámetros, lo hace muy versátil. La soldadura por chispa también se utiliza en la industria de la construcción metálica para aumentar la longitud del ángulo de hierro utilizado para fabricar vigas . ^{[ 1 ]}

La industria del aluminio utiliza la soldadura por chispa para unir aluminio, acero y cobre en diversos conductores portadores de corriente llamados barras colectoras . El acero se utiliza por su resistencia, el cobre por su conductividad y el aluminio por su combinación de costo y conductividad. ^{[ 4 ]}

• longitudes de riel
• soldadura por percusión