Plasma Gas Sheath Flow
The plasma gas sheath flow is a laminar, ionized gas flow around the arc in plasma welding. It thermally constricts and increases energy density.
Physicochemical Mechanism of Action
The plasma gas sheath flow is a continuous, uniform gas flow around the arc in a plasma welding process. The ionized working gas (such as helium or argon) is accelerated by electric fields and forms a sheath around the burning arc. This process thermally constricts the arc surroundings, raises the temperature, and leads to high energy density in the weld area.
Metallurgical Relevance & Welding Risks
The plasma gas sheath flow is crucial for the quality of the plasma weld. An uneven or too strong flow can lead to irregular heat distribution, which in turn can cause stress and possible cracks in the weld material. A missing sheath can impair the effectiveness of the arc and lead to poor weld results.
Workshop Practice & Instructions
To ensure an optimal plasma gas sheath flow, it is important that the gas flow is precisely regulated. This is done by adjusting the gas flow switch on the welding machine. A typical value for the gas flow is about 15-20 l/min with an arc of 30 mm diameter. It is also important that the working gas is clean and free of moisture and dust to ensure a homogeneous flow.