The generation and characteristic of plasma arc of plasma surfacing welding equipment

       

The generation and characteristic of plasma arc of plasma surfacing welding equipment

The plasma arc of the plasma surfacing machine uses a special welding gun to ionize the gas between the cathode and the cold nozzle or between the cathode and the workpiece (also known as the compression arc). When the arc passes through the orifice of the water-cooled nozzle, it is cooled by the cold airflow and the wall of the water-cooled nozzle hole, and the arc will produce a compression effect.

 

1: Thermal compression effect

 

    The copper nozzle has good electrical and thermal conductivity. Due to the water cooling, the temperature of the nozzle hole wall is very low. Therefore, the closer the gas with a certain pressure into the gas chamber of the spray gun is to the hole wall, the lower its ionization degree. The cold air layer close to the hole wall is basically not ionized, but a neutral gas, so that the arc and the hole wall are formed In a circle of neutral gas flow layer that is both insulating and heat-insulating, the arc current is forced to concentrate to the center of the gas with a high degree of ionization. The contraction of the arc current cross section increases the current density, and the entire process is an effective reaction of thermal compression.

 

2: Mechanical compression effect

 

    The cold air layer around the plasma arc column is attached to the wall of the nozzle tunnel. Therefore, the nozzle aperture basically determines the diameter of the annular cold air layer and also determines the thickness of the plasma arc. Obviously, the nozzle aperture and its geometric size not only achieve different degrees of compression of the arc through the thermal compression effect, but also play a role in mechanical compression of the arc.

 

3: Self-magnetic compression

 

    The arc current flows in a certain direction, and the arc column is equivalent to a bunch of parallel conductors with the same current direction. Each energized conductor generates a magnetic field around it, and under the action of electromagnetic force, the arc column is subjected to a compression force directed to the center of the arc column, and the arc column is compressed.

 

These three compression effects reduce the cross-sectional area of the arc column, increase the density of charged particles, and increase the intensity of the electric field. This compressed arc is called a plasma arc.