What are the factors influencing the lamellar tearing of Z-direction steel

What are the factors that affect the lamellar tearing of Z-direction steel?

1. The type, quantity and distribution of non-metallic inclusions are the basic causes of lamellar tearing in Z-direction steel, and the internal factors of anisotropy and mechanical properties difference. Inclusions in steel are usually sulfide, silicate and aluminate.

2. Z-direction restraint stress, the thick wall structure bears different Z-direction restraint stress in the welding process, as well as the residual stress and load after welding, which are the mechanical conditions for the lamellar tearing of Z-direction steel.

3. Hydrogen is an important factor in the lamellar tearing of Z-direction steel induced by cold cracking near the HAZ.

In fact, the lamellar tearing of Z-direction steel is not related much to the strength of steel, but mainly related to the amount and distribution of inclusions. There are sulfide, oxide, silicate and other low melting point non-metallic inclusions in the rolled steel plate, especially sulfide. During rolling, they are spread into flakes and distributed in the layers parallel to the surface. Under the action of welding stress perpendicular to the thickness direction, the inclusions first crack and expand. After that, this kind of cracking occurred between the layers, and became a whole, resulting in the stepped tearing of Z-direction steel.