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Welding Defects Is So Common, But Why?

welding defects:



        The improper welding parameters, the base metal and the selection of method introduce defects in the weld metal. So the. defective weld causes failure in service conditions and damages to the properties the defects in weld depending on thickness, load, environment and size of the weld. The major defects which are 
causing in the weld are: 

        1. In complete fusion 

        2. Cracks 

        3. Porosity 

        4. Undercut 

        5. Distortion 

        6. Slag inclusion 

        7. Lamellar teaming 

         8. Overlapping. 

1. Incompletefusion:

This is due to improper. penetration of the joint. The parameter mainly affects the welding current. If the current is very low, it is not 
sufficient to heat the metal all over the place. The wrong design of the weld also causes defects. 



weld efet






2. Cracks: 

The cracks are mainly classified into two types 

               1. Hot cracking, and 

                2. Cold cracking 

Hot cracking occurs at high temperamre and cold cracking occurs at room temperature. The main causes of crack formation are: 

                       1. Arc speed 

                        2.Ducti1ity 

                         3. Soliditication rate 

                        4. T emperature. 







3. Porosity: 
            

              It is due to the presence of gases in the solidifying metal which are producing porosity. The gases are: oxygen, nitrogen, and hydrogen. The parameters which are causing porosity are: 

         l. Arc Speed 

         2. Coating of the electrode 

          3. Base metal composition. 

          4. Incorrect welding technique 

The sources of hydrogen formed on the weld pool are electrode coatings. Then the oxygen becomes as oxide form in the pool. 

Nitrogen enters in the form of atmospheric nitrogen. 







4. Undercut:

     A groove gets formed in the parent metal along the sides of the weld. The main causes of the undercut are:

       1. High current 
    
       2.Arc length 

       3.Electrode diameter 

       4. Inclination of electrode. 



5. Distortion:

It is defined as the change in shape and difference between positions of two plates during the welding. The base metal under the arc melts and already welded base metal starts cooling. This will create a temperature difference in the weld and will cause distortion. The factors which are causing distortion are:

          l. Arc speed 

         2. Number of passes 

         3. Stresses in plates 

         4. Joint type

         5. Order of welding. 






6. Slag inclusions: 

During the solidification of weld, any foreign materials present in the molten metal will not float. It will be entrapped inside the metal. 
So, this will lower the strength of the joint. 







7. Lamellar Tearing: 

This is due to the presence of non-metallic inclusions. It is formed during the non-metallic inclusions running parallel to the plate. It is seen in large structures. T type and corner joints are getting in this type 0f cracks. 







8. Over lapping: 

It occurs when the molten metal flows over the parent metal and remains without fusing. The parameters which are causing over lap are:

          l. Arclength 

         2. Arc speed 

         3. Joint type. 

         4. Current 





Some of welding defects may occur during welding of metals. 

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