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Difference between lamination and lamellar tearing

Difference between lamination and lamellar tearing

Postby jabir » Tue Jul 02, 2013 7:39 am

Can you explain the difference between lamination and lamellar tearing
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Re: Difference between lamination and lamellar tearing

Postby Hollan Petersen » Tue Jul 02, 2013 3:45 pm

Lamination is a base metal discontinuity of plates that starts during the casting process of plate and it forms during the subsequent rolling process. Lamination may happen in case of high concentration of sulphide and oxide inclusions in the steel when they transferred to the center of the casting during the cooling process that occurs from outside to inside. These inclusions remain near to the center line of the plate in the subsequent rolling process and if there are sufficient inclusions then separation can occur. This separation is called lamination and it can be detected with ultrasonic test.

Instead lamellar tearing is a kind of weld-cracking that forms beneath a weld. It happens when a plate material that presents low ductility in the through-thickness direction is welded to a perpendicular element and so thermal contraction strain that acts on the through-thickness direction of the plate may produce such a cracking. Basically lamellar tearing is due to non-metallic inclusions (sulfur, oxide inclusions) that are present in the base metal as well as it depends on joint design, welding process, welding consumable and the deletion of preheating.

In the attached file you could see examples of these two defects.
Attachments
lamination - lamellar tearing.pdf
examples of lamination and lamellar tearing
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