________ is/are caused by non-metallic inclusion such as sulphides and oxides.

Explanation:

Types of welding defects:

• Porosity
• Slag inclusions
• Incomplete penetration
• Underfilling
• Undercutting
• Inclusions
• Cracks
• Lamellar tears

Cracks:

• Cracks may occur near or inside the weld.
• They are categorized as micro or macro cracks depending on their visibility with the naked eye.
• Cracks that occur at low temp. (<200 C) are known as cold cracks whereas cracks occur at a high temp. are known as hot cracks.

Undercutting:

• The undercut is a groove formed adjacent to the toe of the weld.
• It is caused by excessive overheating, and improper position of the electrode.
• It reduces the fatigue strength of the joint.

Underfilling:

• It happens when the proper amount of molten metal is not fed to the gap.

Lamellar tears:

• Lamellar tears are caused by nonmetallic inclusions such as sulfides and oxides.
• These inclusions are elongated by the rolling process.
• This generally happens in plates with low ductility in the thickness direction.
• They are more dominant in T and corner joints where the fusion boundary is parallel to the rolling plane.