Here are some of the causes of welding cracks. By knowing the causes, you can do a preventive measure to avoid such weld defects.
1. Rigidity of the joint, i.e., joint members not free to expand or contract when subjected to welding heat and subsequent cooling (localized stresses).
2. Poor ductility of base metal.
3. Hardenability, high S and C percentage of base metal.
4. Concave weld bead.
5. Fast arc travel speed.
6. Electrode with high H2 content.
Lamellar Tearing is the result of very severe restraint on the joint, poor ductility and due to the presence of non metallic inclusions running parallel to the plate surface.
In large highly stressed structures such cracks can be seen in the material of the parent plats and the heat affected zone of a joint, the cracks usually running parallel to the plate surface. Certain types of joints such as T, and corner are more susceptible to lamellar tearing than others.