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Preparatory Notes for ASNT NDT Level III Examination - Ultrasonic Testing, UT

Preparatory Notes for ASNT NDT Level III Examination - Ultrasonic Testing

Preparatory Notes for ASNT NDT Level III Examination - Ultrasonic Testing

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Micro-shrinkage is usually many small subsurface holes that appear at the<br />

gate of casting / can also occur when molten metal must flow from a thin<br />

section into thicker section of casting.<br />

Blow hole are small hole at the surface of the casting caused by gas which<br />

comes from the mold itself. (wet sand mould <strong>for</strong>ming steam resulting in blowhole)<br />

Porosity is caused by entrapped gas. It is usually subsurface or surface<br />

depending on the mold design.

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