Deoxidization

Deoxidization is a method used in metallurgy to remove the rest of oxygen content from previously reduced iron ore during steel manufacturing. In contrast, antioxidants are used for stabilization, such as in the storage of food. Deoxidation is important in the steelmaking process as oxygen is often detrimental to the quality of steel produced. Deoxidization is mainly achieved by adding a separate chemical species to neutralize the effects of oxygen or by directly removing the oxygen.

Deoxidization is a method used in metallurgy to remove the rest of oxygen content from previously reduced iron ore during steel manufacturing. In contrast, antioxidants are used for stabilization, such as in the storage of food. Deoxidation is important in the steelmaking process as oxygen is often detrimental to the quality of steel produced. Deoxidization is mainly achieved by adding a separate chemical species to neutralize the effects of oxygen or by directly removing the oxygen. K_{eq} = a_{ox} / (a_D^n * a_O^m ) where a ox is the activity, or concentration, of the oxide in the steel, a D is the activity of the deoxidizing agent, and a O is the activity of the oxygen. An increase in the equilibrium constant K eq will cause an increase in a ox , and thus more of the oxide product. K eq can be manipulated by the steel temperature via the following equation: log K_{eq} = A_D / T - B_D where A D and B D are parameters specific to different deoxidizers and T is the temperature in K°. Below are the values for certain deoxidizers at a temperature of 1873 K°. Below is a list of commonly used metallic deoxidizers: Ferrosilicon, ferromanganese, calcium silicide - used in steelmaking in production of carbon steels, stainless steels, and other ferrous alloys Manganese - used in steelmaking Silicon carbide, calcium carbide - used as ladle deoxidizer in steel production Aluminum dross - also a ladle deoxidizer, used in secondary steelmaking Calcium - used as a deoxidizer, desulfurizer, or decarbonizer for ferrous and non-ferrous alloys Titanium - used as a deoxidizer for steels Phosphorus, copper(I) phosphide - used in production of oxygen-free copper Calcium hexaboride - used in production of oxygen-free copper, yields higher conductivity copper than phosphorus-deoxidized Yttrium - used to deoxidize vanadium and other non-ferrous metals Zirconium Magnesium Carbon Tungsten K_{CO} = P_{CO}/(a_C * a_O) where P CO is the partial pressure of the carbon monoxide formed. Decreasing the oxygen activity(a O ) will raise the higher equilibrium constant, increasing CO production. To achieve this, subjecting the pool of steel to vacuum treatment decreases the value of P CO , allowing for more CO gas to be produced. K_{FeO} = a_{[O]} / a_{(O)} where a [O] is the activity of the oxygen in the slag, and a (O) is the activity of oxygen in the steel. Reducing the activity in the slag (a [O] ) will lower the oxygen levels in the slag. Afterwards, oxygen will diffuse from the steel into the lesser concentrated slag. This method is done by using deoxidizing agents on the slag, such as coke or silicon. As these agents do not come into direct contact with the steel, non-metallic inclusions will not form in the steel itself.

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