What is this method?
A weld is made when separate pieces of material to be joined to form one single piece when heated to a temperature high enough to cause softening or melting. Filler material is typically added to strengthen the joint. Welding is a dependable, efficient, and economic method for permanently joining metals. The number of different welding processes has grown in recent years. These processes differ greatly in the way heat and pressure (when used) are applied, and in the type of equipment used. There are currently over 50 different types of welding processes. The most popular processes are shielded metal arc welding (SMAW), gas metal arc welding (GMAW) and gas tungsten arc welding (GTAW), Gas or Oxy Acetylene Welding and Cutting.
Why is this method?
This method is used because when there is a lot of defect in the material. This defect is different from discontinuity. It is important to distinguish between a weld defect and a discontinuity. A weld defect has, by its nature, rendered a part or product unable to meeting applicable standards and is a candidate for reject. A discontinuity is an interruption of the structure or the material—mechanical, metallurgical, or physical. A discontinuity is not necessarily a defect if it can be repaired. There, everything starts out as a discontinuity and either stays in this category or is classified as a defect. The most common types of surface discontinuities are: misalignment, undercut, concave/convex weld, overlap, burn through, weld gaps, cracks, and porosity. The most common types of internal discontinuities are: incomplete penetration, incomplete fusion, cracks, inclusions, HAZ irregularities, and impurities.