Common deoxidizers for cast steel smelting usually include: aluminum, calcium, manganese, silicon, titanium, rare earth, etc.

Aluminum (Al) Final deoxidizer, deoxidation product Al2O3, melting point 2050℃, hardness HV3000.

1. Advantages
   A. Strong deoxidation power;
   B. Cheap price;
   C. Convenient operation;
   D. Less smoke ash, which can be left to prevent secondary oxidation.
2. Disadvantages
   A. Forms grain boundary AlN with N, causing embrittlement of castings (precipitation temperature below 1150℃), and the thicker the casting, the easier it is to produce;
   B. Deoxidation product, high melting point, high hardness, affects the fluidity of molten steel and the processability of castings, and is small and not easy to float;
   C. The general addition amount (about 0.1%) is easy to form type II sulfide, which is not good for the mechanical properties of castings (especially toughness).
3. Improvement of shortcomings
   A. Control the residual aluminum content between 0.03% and 0.07% (the oxidation loss of aluminum is about 50%, so the amount of aluminum added is about 0.1%). Thick castings should be reduced as appropriate.
   B. Use Zr or Ti to remove N first, and then add Al (ZrN or TiN is less harmful).
   C. Add Ca after Al to form calcium aluminate (CaO·Al2O3·SiO2) with a low melting point (1400℃). To improve fluidity and processability (hardness HV1200), at the same time, it can form type I oxysulfide to improve mechanical properties (especially toughness).

Calcium (Ca)      Final deoxidizer, deoxidation product CaO, melting point 2600℃.

1. Advantages
   A. Strong oxidizing property, so it can form stable oxides;
   B. Added after Al is added, it can improve the deficiency of Al2O3;
   C. Rapid deoxidation reaction;
   D. Promotes type I sulfide and improves mechanical properties (especially impact value);
   E. Not only deoxidation, but also desulfurization;
   F. Used in combination with dense cerium alloy, it can reduce the tendency of castings to hot crack.
2. Disadvantages
   A. Low boiling point (1492℃), so it is easy to volatilize, the effective action time is short (60~90s), it is not easy to remain and cannot prevent secondary oxidation during pouring;
   B. Pure metal is not easy to store (easy to oxidize), generally alloys, the most common is Ca-Si;
   C. Low solubility in molten steel, so it cannot be deoxidized by itself.
3. Improvement of Disadvantages
   A. Make alloys to reduce volatility, such as CaSiBa, CaSiBaAl;
   B. Austenitic stainless steel, heat-resistant steel, and high manganese steel have high contents of: Ni, Mn, which can increase their solubility, and calcium can be used alone for deoxidation (that is, not with aluminum).

Manganese (Mn) is generally used as a deoxidizer in the middle or end of the melting process.

1. Advantages
   A. It is a deoxidizer and a good desulfurizer. It can convert low-melting FeS (1200℃) into high-melting MnS (1600℃) to reduce hot brittleness;
   B. It can increase the toughness of steel (grain refinement effect), and Si can also have a similar effect;
   C. The deoxidation product MnO is harmless to processability;
   D. It is beneficial to inhibit the formation of pinholes.
2. Disadvantages
   A. The deoxidation power is insufficient, so other strong deoxidizers, such as Al, Ca, Ti, etc., are often added;
   B. When the manganese content is too high, the molten steel is easy to corrode the sand mold and produce inclusions 2Mn+SiO→2MnO+Si

Silicon (Si) Like Mn, it is generally used as a deoxidizer in the middle or end of the melting process.

Disadvantages
A. High content is harmful to welding performance (easy to crack, regardless of carbon steel, alloy steel, stainless steel);
B. Deoxidation product SiO2 is not conducive to processability.

Advantages
A. Stronger deoxidizing power than Mn;
B. Increases the fluidity of molten steel;
C. Improves the corrosion resistance and high temperature strength of steel.