Bulk Ferroalloys

Bulk Ferroalloys  Ferroalloys are a group of materials which are alloys of iron that contain a high percentage of one or more non ferrous metals as alloying elements. These alloys are used for the addition of these other elements into liquid metal. They are normally used as addition agents. More than 85 % of ferroalloys produced are used primarily in the manufacture of steel. Ferroalloys are used as master alloys in steel making, alloying of steels, for the production of stainless steels, and in iron or steel foundries. Ferroalloys are used in steel making for deoxidation as well as for the introduction of alloying elements. They are the most economical way for introducing alloying element into the steel. Ferroalloys impart distinctive qualities to steels and cast irons. The effect on the qualities of steels and cast irons largely depends more or less on the following influences. A change in the chemical composition The removal or the tying up of harmful impurities such as oxygen, nitrogen, sulphur or hydrogen A change in the nature of the solidification, for example, upon inoculation. Ferroalloys are also added in steel production for grain size control as well as for improvement in the mechanical properties of steel. Depending upon the process of steelmaking and the type of steel being made, the requirement of different ferroalloys varies widely. The addition of ferroalloys to steel increases its resistance to corrosion and oxidation, improves its hardenability, tensile strength at high temperature, wear and abrasion resistance with added carbon and increases other desired properties in the steel such as creep strength etc. Ferroalloys are vital inputs for producing all types of steel. They are used as raw material in the production of alloys steel and stainless steel. Ferroalloys are usually classified into two...

Silicon in Steels

Silicon in Steels  Silicon (Si) (atomic number 14 and atomic weight 28.09) has density of 2.34 gm/cc. Melting point of Si is 1412 deg C and boiling point is 2355 deg C. The phase diagram of the Fe-Si binary system is at Fig 1. Fig 1 Fe-Si phase diagram  Si is present in all the types of steels either as an intentional addition or as a residual from the ore, scrap or deoxidizing agents. Available forms  There are many Si containing addition agents which are used in steel making. Ferrosilicon (Fe-Si) and silico manganese (Si- Mn) are by far the most common addition agents. Fe-Si is a ferroalloy of iron (Fe) and Si. Fe – Si contains 65 % to 90 % of Si and minor amounts of Fe, aluminum (Al) and carbon (C).  Fe – Si is usually produced in four grades. These are standard grade, low Al grade, low C grade, and high purity grade having low content of titanium (Ti). The standard grade of Fe- Si contains Al up to 2 % while the low Al grade has Al content of 0.5 % maximum. It is produced by reduction of quartzite (SiO2) with coke in presence of iron ore.  Fe- Si is made in the submerged arc furnace. Si – Mn is a ferroalloy with high content of Mn and Si. It is produced by heating a mixture of oxides of MnO2, SiO2 and Fe2O3 with C in a furnace. These oxides undergo a thermal decomposition reaction. The standard grade contains Mn in the range of 62 % to 68 %, Si in the range of 12 % to 18 % and C in the range of around 2.0 %.  The low C grade of Si – Mn has a C...