What is lamellar tearing in welding?

Lamellar tearing is a serious defect that occurs under the weld, in the base metal, parallel to the rolled surface.

Cause:

• Through-thickness tensile stresses (Z-direction) combined with elongated non-metallic inclusions in the rolling direction
• Occurs especially in thick plates and T-joints (with fillet weld)
• The through-thickness stress created by weld shrinkage exceeds the metal's strength in that direction

Prevention:

• Material selection: use low-sulphur steels with guaranteed through-thickness ductility (“Z” steels, the Z value being set in the specification)
• Joint design: Avoid simple T-joints. Use stiffeners, K-joints, or double bevel welds
• Preheating: at the temperature the WPS prescribes to reduce residual stresses
• Welding technique: Use low heat input processes (pulsed GMAW), buttering layer with a ductile filler metal

Detection: Lamellar tearing is not visible on the surface. It is detected by ultrasonic testing (UT). This is a critical defect — the part must be rejected or repaired by grinding and rewelding.