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Resistance seam welding, the difference between intermittent and continuous

2024-03-26

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Resistance seam welding is a process in which a weld is formed at the interface of two similar metals. Seams can be butt joints or lap joints and are usually an automated process. It differs from flash welding in that flash welding usually welds the entire joint at once, whereas seam welding starts at one end and gradually forms the weld. Like spot welding, seam welding relies on two electrodes, usually made of copper, to apply pressure and current. The electrodes are usually disc-shaped and rotate as material passes between them. This allows the electrodes to remain in constant contact with the material for prolonged continuous welding. The electrodes can also move or assist the movement of the material.

The transformer provides energy to the welded joint in the form of a low voltage, high current AC power source. The joint of the workpiece has high resistance relative to the rest of the circuit and is heated to its melting point by the current. The semi-molten surfaces are pressed together by the welding pressure, resulting in fusion and a uniform welded structure. Due to the heat generated, most seam welders use water cooling through the electrode, transformer and controller components.

Seam welding produces extremely durable seams because the joint is forged due to the heat and pressure applied. A properly welded joint formed by resistance welding is easily stronger than the material from which it was formed.

A common use of seam welding is in the manufacture of round or rectangular steel pipes. Seam welding has been used to make steel beverage cans, but is no longer used here because modern beverage cans are seamless aluminum.

There are two modes of seam welding: intermittent and continuous. In intermittent seam welding, the wheel advances to the desired position and stops for each weld. This process continues until the desired weld length is reached. In continuous seam welding, the wheel continues to roll as each seam is made.