Lack of Preheating: Due to inadequate preheating, microstructural changes may take place. These hydrogen atoms may be induced in the weld metal from the surrounding, electrode, base metal, or any contamination present on the root face.Ģ. Diffusion of Hydrogen atoms: Hydrogen atoms cause cold cracking. It is often associated with non-metallic inclusion.ġ. Most of the time it develops in the HAZ but may occur on the weld metal too. Preheating and post-heating to avoid rapid coolingĬold cracks occur after the solidification of weld metal it can even develop several days after completion of welding. When a hot crack occurs on the weld metal, then it is termed as Solidification Crack and if it occurs in the HAZ then called Liquation crack.ġ. Hot cracks mostly occur in the weld metal but it may occur at the Heat Affected Zone (HAZ) region too. Hot cracks occur during welding or soon after the completion of welding, It is most likely to occur during the solidification of the molten weld pool. The crack occurs when localized stress exceeds the ultimate Tensile Stress (UTS) of the material. on the surface, subsurface, at any depth, or at the root. Cracks may be of any size or shape it can be either microscopic or macroscopic. Please see the following table Different types of welding defects along with their causes and remedies are explained below 1. We can say that defects that are not present on the surface are internal defects. Internal defects are those which exist in the material at some depth.
External defects are those which are found on the surface itself. Incorrect job preparations Classification of Defects:ĭefects can be classified as external defect (also known as visual defect or surface defect) or internal defect (also known as hidden defect or subsurface defect). Inappropriate selection of filler metal and parent metalĦ. (Note: Discontinuity is also termed as “ reflector” in some codes and texts) Defects may occur due to the following reasons Ĥ. A defect can be macroscopic or microscopic.
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Please note that a discontinuity can be called as a defect only when if it exceeds the specified code limit, hence we can say that every defect present in the weld metal is a discontinuity but every discontinuity present in the weld metal may not necessarily be a defect.
Any discontinuity (or irregularity) in the weld metal, which exceeds the applicable code limit, is termed as a WELD DEFECT (or Welding Defect).
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