Pitting

PittingPitting (Carbon Steel)Pitting presents as random smooth depressions or shallow pits in the casting. This defect indicates that oxygen reacted with the chrome in metal. This reaction is more prevalent with certain metals. 400 stainless series and pH stainless metals may be more prone to this defect.

The causes of this defect are evident in the other portion of the process. To cure these causes, R&R recommends taking the following actions.

 

Area

Cause

Cure

Wax

 

 

Shell

 

 

Metal

 

 

Other

  1. Oxygen reaction with metal.
  2. Chromium (Cr) oxides form when oxygen is present during solidification.
  3. CO gas forms through reaction between C in steel with the refractories of the mold.
  1. Eliminate/reduce oxygen presence after pouring.
  2. Avoid contact with oxygen during solidification. Implement canning practice once shells are poured.
  3. Use carbon stucco, put molds in sand and use alternative refractories.

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