Shear Stress Slip

If you put too much stress into the material during welding, the crystal lattices can start to slide over each other. That's called plastic deformation, and if it happens uncontrolled, you get cracks or distortion. Especially with austenitic steels, you have to be careful because they are sensitive to that. So make sure you have a clean, controlled cooling and keep the welding parameters in check. If you feel the weld is under too much stress, let the part cool down slower or clamp it better. That way you avoid the structure breaking away.