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About "Flaw"


Main types of surface flaw and characteristic, difference of detectability by flaw detection method are indicated in following table:

Flaw Name Characteristic and Shape Form of Cross Section Surface property Eddy Current Tester Magnetic Leakage Flex Tester
Rotational Encircling Probe Rotational Scan
Seam Crack Linear shape flaw which occurs in longitudinal direction continuously △~×
Creases Creases shape flaw which occurs on contacting surface △~×
Fold Fold flaw which along the rolling direction △~×
Scab Peel off of surface, wrap shaped flaw 〇~△ 〇~△ 〇~△
Rough Surface The flaw which surface got uneven by getting rough
Dent Dent flaw which occurs locally × × ×
Scab Crack Crack which is originated from scab flaw
  • : Easily detectable
  • 〇: Detectable
  • △: Depend on condition
  • ×: Difficult to detect

: Depend on the direction of scanning

Target material

Eddy current test

It is appropriate for the final inspection of the target material which has smooth surface after the process such as wire drawing or peeling.
Example: metal, nonferrous metal bar (Stainless, aluminum, copper), cold finished steel bar, steel pipe, wire, drawn wire, etc.

Magnetic leakage flux test (MLFT)

It is appropriate for the inspection of the material which has rough surface and is at the initial stage of processing such as after forming process by rolling.
Example: Round bar, Steel pipe, Black steel round bar, other strong magnetic material

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