Inherent Discontinuities - Blowholes

Question 1

Inherent discontinuities occur during …

Answer 1

initial melting, refining processes (ingots), and during solidification from molten metal (castings)

Question 2

Pouring of liquid “metal” into a shape

Answer 2

ingot - discontinuities are blowholes and porosity

Question 3

Solidification of molten metal

Answer 3

casting - discontinuities are cold shuts, hot tears, shrinkage

Question 4

Characteristics of blowholes and porosity:

Answer 4

spherical voids or bubbles. They will appears as seams after rolling, forging, or extrusions

Question 5

Metallurgical analysis of blowholes and porosity:

Answer 5

accumulation of gases that rise through the liquid phase of the metal; they may or may not migrate to the surface and become trapped

Question 6

Surface blowholes can be caused when molten metal comes into contact with sand molds and the water in the sand is released as _____

Answer 6

steam

Question 7

__________ may be employed to determine if there is a detrimental amount of porosity present

Answer 7

radiography

Question 8

Which penetrant method will produce the best results for blowholes open to the surface?

Answer 8

Fluorescent - post emulsified