Dross - Casting defects

Dross - Casting defects

Figure 1: Dross.

Figure 1: Dross.

Defect name: Dross
Record No.: 868
Type of defect (Internal/Surface): Internal
Defect classification: Casting defects
Steel name: Steel
Steel composition in weight %: No data.
Note: Irregularly shaped interruption in the material.

Typical characteristics: Dark scars, foamy dark surfaces, very finely distributed. Dross worsens the mechanical properties, Dross mainly consists of magnesium oxy-silicates and magnesium sulphides, and is a product of the reaction of magnesium with oxygen, sulphur and silicon.

Preferred defect locations: In the upper casting surface or beneath cores. Mostly in cast iron with nodular graphite, often only visible after the casting skin has been removed.

Remedial measures:
Dross cannot be prevented, only reduced.
Melts:
- High temperature,
- Low residual Mg contents,
- Clean melting of pure raw materials,
- Highly concentrated Mg master alloys or pure Mg,
- Gas purging(cleaning),
- Refining slags (melt cleaner)
In the work pieces:
- Draw off and restrain treatment slags (large pouring basin, optimum casting system),
- Filters are very effective,
- Dry, closed moulds,
- HOT casting.
Reference: Not shown in this demonstration version.