What are the factors that affect laminar tearing?

1、The quantity, type and distribution of non-metallic inclusions are the essential causes of laminar tearing and the origin of the opposite sex and mechanical properties of steel.

2、Z-direction restraint stress: thick wall welded structure bears different Z-direction restraint stress, residual stress and post weld load,which is the mechanical condition causing laminar tear.

3、Influence of hydrogen: generally, near the heat affected zone, the layer tearing induced by cold crack, and hydrogen is an important influencing factor.

Due to the great influence and serious harm of layered tearing, it is necessary to judge the sensitivity of steel layer tearing before construction.

The evaluation:Z-direction tensile section shrinkage method and Z-direction critical stress method. The area shrinkage rate shall not be less than 15%. Generally, it is expected that 15 ~20% is appropriate to prevent laminar tearing. When it is 25%, it is considered to have excellent laminar tear resistance.

From the tear, the construction process and design are mainly to avoid stress concentration and Z-direction stress. See the following example for specific measures:

1. The use of double-sided weld can alleviate the stress state in the root area of the weld, and single-sided weld shall be avoided as far as possible to prevent stress concentration

2. .Using symmetrical fillet weld with less welding quantity instead off all penetration weld with large welding quantity can effectively avoid excessive stress.

3. The groove shall be made on the side bearing Z-direction stress.

4. For T-joints, a layer of low-strength welding material can be deposited on the transverse plate in advance to prevent cracks at the root of the weld and alleviate the welding strain.

5. Some measures to prevent cold cracking shall be taken as far as possible to prevent layer tearing caused by cold cracking, as appropriately increasing preheating etc.