Black Stain

Black StainBlack stain presents as very superficial black spots on a good and smooth casting. This defect indicates that the metal reacted with oxygen forming Chromium (Cr) and Manganese (Mn) oxides during melting, casting and solidification.

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

 

Area

Cause

Cure

Wax

 

 

Shell

 

 

Metal

  1. High metal and mold temperatures.
  1. Melt under Argon (Ar) blanket and adjust temperatures.

Other

  1. Turbulent casting.
  2. Slow cooling down curve.
  1. Use a ceramic filter or carbon stucco.
  2. Separate molds after casting. Can molds after casting.

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