52 Toe Cracks and Root Cracks

Toe cracks and root cracks have similar causes but different appearances. They are both generally cold cracks and initiate in regions of high residual stress.

Toe cracks are cracks that proceed from the weld toe into the heat-affected zone (HAZ) and base metal. The weld toe is the junction of the weld face and base metal. Toe cracks are typically caused by stresses from thermal shrinkage acting on a brittle HAZ and are located along the toes of the weld.

Root cracks are cracks that proceed into the base metal from the root of a weld. Root cracks are difficult to detect unless they have propagated through to the opposite side of the base metal.

Toe and Root Crack Prevention

Toe and root crack prevention requires welding procedures and techniques that eliminate embrittlement or excessive stresses in the HAZ of the base metal. With hard enable steels, toe and root crack prevention may be achieved by retarding the cooling rate of the base metal and HAZ with high preheat, or by stress relief after welding with post heating.