Flash welding is a joining process used to join two parts together. The work acts as the electrode and the entire cross section is welded. The parts are clamped and brought close together and a current is applied. The current creates an arc between the work pieces and heating begins as well as expulsion. Force is applied. The parts come together. The arcing current is removed. The parts joint is upset/forged to the desired amount. The part is cooled and the force is removed. The resultant flash weld has weld flash around the weld area which is usually mechanically removed. The resultant welds are very strong and fluid tight. Wheel rims are manufactured using this process and are very reliable. The rims do not leak air on our cars and trucks.
Flash and butt welding both use the work piece as the electrode. They both use a clamp to hold the parts and apply force. The entire cross section of the work piece is welded. It is in the timing and application of force and current that they differ.
In butt welding the parts are clamped brought together under force and then current is applied. The parts heat due to Joules Law H=I2 rt heating. The joint gets hot upsets and after cooling the force is removed. The result is a strong butt joint.
Flash welding uses similar clamps but the parts are place close to each other before force is applied. Current initiates with the intent of creating an arc which generates large amounts of heat and metal flash. This flashing action both cleans and heats the mating faces of the parts. Then force is applied as the arc current is terminated. The hot parts are upset and joined together. The part cools and force is removed. This flash weld joint is also very strong.
JOULES LAW STATES:
In this equation the current, resistance and time are the variables. The controller or timer can alter both the time and the current. The resistance of the parts being welded is fixed but the resistance can be changed by altering the force/pressure used in the welding process. The question is which will have the largest affect upon the process. The answer is the current (I).
Per the definition of the Resistance Welding Manufacturers Alliance:
RESISTANCE WELDING IS THE JOINING OF METALS BY APPLYING
FOR A LENGTH OF
THROUGH THE METAL AREA WHICH IS TO BE JOINED
Reference: RWMA - Resistance Welding Manual 4th Edition
Group B materials is a designation of the Resistance Welding Manufacturers Alliance (RWMA). It describes a group of Tungsten/Copper materials with high strength and good electrical conductivity. Their main feature is high strength at high temperatures. Their properties make them excellent materials to use in the resistance welding industry as electrodes at high heat and forces.
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