In recent years, as steel structures have become larger and more complicated, welded joints with strict restrictions in terms of structure, function or appearance have been employed in various fields, and there is an increasing number of cases in which greater tensile stress is applied in the throughthickness -direction..
(1) What is Lamellar Tear?
Lamellar tear is a phenomenon in which cracking parallel to the surface of the steel plate occurs in a cross joint, T-joint, corner joint or other welded joint that is subject to tensile stress in the through-thickness direction of the plate. Causes include those that originate simply in non-metallic inclusions (mainly MnS), as well as those that originate in root cracking. To check for lamellar tear-resistance, there are direct methods such as the Z window restraint cracking test. A commonly used simple method is to make the evaluation by combining the reduction of area value in
through-thickness tension testing and the amount of sulfur in the steel. The WES3008 Standard of the Japan Welding Engineering Society and JIS G3199 stipulate lamellar tear-resistant steel in which the reduction of area value is guaranteed, and the nonmetallic inclusions in the steel and the compositional segregation are also reduced.
Diagram of occurrence of lamellar tear
The relationship between the reduction of area of the throughthickness direction φz and the quantity of S (from WES3008-1999)
The reduction of area of the through-thickness direction of the anti-lamellar tear steel according to JISG3199
Source: www.nssmc.com
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