Manganeso Electrolítico (EMM / AlMn)
Manganese for iron neutralization in aluminum alloys. Transforms harmful β-Fe phases into less detrimental α-Fe forms.
Manganese is used in aluminum casting primarily as an "iron corrector." In secondary alloys, iron (Fe) forms β-AlFeSi intermetallic phases (needles) that drastically reduce ductility and impact resistance. Mn promotes the transformation of these harmful β phases to the α-AlFeMnSi form (Chinese script), which is compact and less detrimental. The general rule is to maintain Mn ≥ 0.5 × Fe. Available as manganese metal flakes or AlMn20% master alloy.
Chemical Composition
| Element | Symbol | Percentage |
|---|---|---|
| Manganese (flakes) | Mn | ≥ 99.7 % (electrolítico) |
| Iron | Fe | ≤ 0.10 % |
| Silicon | Si | ≤ 0.05 % |
| Carbon | C | ≤ 0.05 % |
Physical Properties
| Property | Value |
|---|---|
| Melting point (Mn) | 1,246 °C |
| Density (Mn) | 7.47 g/cm³ |
| Form | Escamas electrolíticas o AlMn20% waffle |
Metallurgical Function
Iron correction: Mn transforms acicular β-AlFeSi phases (harmful) into compact α-AlFeMnSi phases (less harmful). Also improves mechanical strength and corrosion resistance. In 3xxx alloys it is the main alloying element.
Dosage & Usage
For Fe correction: maintain Mn ≥ 0.5 × %Fe (general rule). In 380 alloy: typical Mn 0.35–0.50%. Mn flakes dissolve slowly due to high melting point — add with vigorous stirring and allow dissolution time (15–30 min). AlMn20% dissolves faster but adds more aluminum.
Applications
- Iron correction in secondary casting alloys
- 380, 383 alloys where Fe is inherent to recovered material
- 3xxx series alloys (AlMn) for containers and sheet
Industries
Aluminum Casting
Neutralization of inherent Fe in recovered and recycled aluminum
Automotive
Mechanical property control in alloys with high Fe
Special Notes
Mn has a high melting point (1,246 °C) and does not dissolve easily in aluminum at 720 °C. For better dissolution: (1) use AlMn20% waffle that melts at ~660–700 °C, or (2) wrap Mn flakes in aluminum foil and submerge with a plunger. Excess Mn (>1%) can form hard Al₆Mn phases affecting machinability.
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