__________ is a group of fine holes on the surface of the weld caused by gas entrapment.

Explanation

Explanation:- Porosity is defined as cavity-type discontinuities formed by gas entrapment during solidification. Porosity is caused by gases that are present in the molten weld. These gases may be trapped and form bobbles or gas pockets as the weld solidify cause porosity are dirty base material, moisture. Causes of porosity: The presence of moisture. Improper gas shield. Incorrect surface treatment. Use of too high gas flow. Contaminated surface. Presence of rust, paint, grease or oil. Important Points When the porosity is seen in the weld face, it is also referred to as "pit". When the porosity is detected, by fracture or radiograph tests, as a sub- surfaced pore that does not extend to the weld face, it is also referred to as "blowhole." Weld Crack - The most serious type of welding defect is a weld crack and it’s not accepted almost by all standards in the industry. It can appear on the surface, in the weld metal or the area affected by the intense heat.