We knew what is electric resistance welding (ERW) previously, next, Prime Steel Pipe will continue to share the types of Electric Resistance Welding. We will discuss high-frequency ERW (contact and induction) and rotary wheel contact welding (AC, DC, and square wave). And we will share the differences among the processes, as well as the power supplies and weld rolls.
All ERW processes have one thing in common–all of them produce a forged weld, although each process has different characteristics. Several electric resistance welding (ERW) processes are available for ERW steel pipe production. The two main types of ERW are high-frequency (HF) and rotary contact wheel.
High-frequency (HF) Welding
The two main aspects of HF welding are processes and power supplies. The two HF welding processes are HF contact and HF induction. In both processes, the equipment that provides the electrical current is independent from the equipment that supplies the forge pressure. Also, both HF methods can employ impeders, which are soft magnetic components located inside the tube that help to focus the weld current in the strip edges. In the case of HF induction welding, the weld current is transmitted to the material through a work coil in front of the weld point. The work coil does not contact the tube–the electrical current is induced into the material through magnetic fields that surround the tube. HF induction welding eliminates contact marks and reduces the setup required when changing tube size. It also requires less maintenance than contact welding. HF contact welding transfers weld current to the material through contacts that ride on the strip. The weld power is applied directly to the tube, which makes this process more electrically efficient than HF induction welding. Because it is more efficient, it is well-suited to heavy-wall and large-diameter tube production. HF welding machines also are classified by how they generate power. The two types are vacuum tube and solid-state. The vacuum tube type is the traditional power supply.
Rotary Contact Wheel Welding
In rotary contact wheel welding, the electrical current is transmitted through a contact wheel at the weld point. The contact wheel also applies some of the forge pressure necessary for the welding process. The three main types of rotary contact wheel welders are AC, DC, and square wave. In all three power supplies, electrical current is transferred by brush assemblies that engage slip rings attached to a rotating shaft that supports the contact wheels. These contact wheels transfer the current to the strip edges.