PLASMA GOUGING

    Welding process and welding engineering came into its own in early 19’s. It was at the time of World War II that welding processes got a new face. Today welding has turned to vital field where lots of career opportunities in it. Welding process or technology had gone through different phases and evolved from a trade to science. Traditional methods got modified during this period of time. In the last 10-15 years plasma gouging became a viable solution. In 1940s the gouging was done using carbon arc with help of welding machine and a carbon electrode to melt metal. The metal part of surface is melted or removed and a gouge or groove is fumed on it. Many types of gouging like oxyfuel gouging, air carbon arc gouging mechanical gouging exist in this field.

    In plasma air gouging smooth and clean grove is obtained. The main advantage that this method provides is that, it is smoke free and also quiet operation. A correct knowledge about the working of this technology and scope of being merged with application based solution is necessary for growth of implementation of the technology.

    Defining the gouge is basic of plasma gouging. For each operation gouge varies according to the application. A gouge which is ideal for one operation may not be ideal for another application. Quality of gouge is another parameter in plasma gouge. Factors that makes a gouge perfect is, whether the operation the operator removed correct amount of material from the surface and also it should be in correct controlled manner. Shape in some case plays vital role in other case may not be crucial.

    The removal of part can be categorized into two ways, positive feature removal and negative feature removal. The positive feature removal refers to the removal of those part above the surface i.e. it will be in space and will not be covered by other material. The negative feature removal refers to removal of part surrounded by other material. Seized bolt removal which is also called nut removal, casting sprue removal, protruding surface features removal such as fillet weld comes under the positive surface feature removal. The excavation of weld defect, spot weld removal and back gouging comes under negative feature removal.

    

    In negative feature removal, the gouge profile is more important. It is crucial than the rate at which one can remove material. Few assumptions are done regarding gouge profile like relation between width and depth of gouge i.e. width of gouge should be greater than its depth and profile should be maximum symmetrical.

The ionized gas which are electricity conductive is super-heated to obtain plasma. The velocity and energy density is increased by constricting its cross section area. Supersonic speeds are achieved. These parameters are varied to obtain different bore design. When the area become more constricted velocity increases and its cutting capabilities are also increased. These factors are combined to produce partial melting and effective subsequent clearing of slag.

    The system amperage and angle of torch are other features that influence plasma gouging. The gouge depth is proportional with amperage. The depth of gouge is increased as amperage increases. The angle of torch influence the gouge shape. A primary angle is given to make basic gouge shape then another, a second angle is given to increase the width of gouge. This process is called offset angle gouging. When angle is zero it is straight line gouging. As angle increases gouge get wider. As angle approach 90 profile become asymmetric shape. WQC NDT Institute provides welding inspection courses in Kochi.

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