Materials needed for Steel Production in Basic Oxygen Furnace Oct16

Materials needed for Steel Production in Basic Oxygen Furnace...

Materials needed for Steel Production in Basic Oxygen Furnace The following types of materials are needed for the production of liquid steel in the basic oxygen furnace (BOF) steelmaking process (Fig 1). Basic raw materials such as hot metal, scrap, and lime etc. Secondary raw materials such as deoxidizers and carburizers. Utility gases such as oxygen, nitrogen, and argon etc. Refractories and Refractory materials such as lining material, gunning material and patching materials etc. Consumable probes such as temperature probes and sampling probes etc. Cooling water for cooling of oxygen blowing lance and exhaust gases. Fig 1 Materials needed for the production of steel in basic oxygen furnace Basic raw Materials The basic raw materials needed for making steel in the BOF converter include (i) hot metal from the blast furnace, (ii) steel scrap and/or any other metallic iron source, (iii) iron ore, and (iv) fluxes.  Scrap, charged from a scrap box, is the first material to be charged into the BOF. The hot metal is then poured into the converter from a hot metal charging ladle, after which the blowing with oxygen gas is started. The fluxes, usually in lump form, are charged into the BOF through a bin system after the start of the oxygen blow. The fluxes can also be injected into the furnace in powder form through bottom tuyeres. The composition and amounts of basic raw materials used in the BOF converter vary from one steel melting shop to another, depending on their availability and the economics of the process. The hot metal or liquid iron is the primary source of iron units and energy. Hot metal is received from the blast furnaces in either open top or torpedo cars. In case of open top ladles, hot metal is poured...

Noble ferroalloys

Noble 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 usually classified into two main categories namely (i) bulk ferroalloys and (ii) noble or special ferroalloys. Noble ferroalloys are of high value and consumed in low proportions. These ferroalloys are one of the vital inputs required for the production of special types of steels and are used as additive inputs especially in the production of alloy and special steels. Noble ferroalloys (Fig 1) are ferro nickel (Fe-Ni), ferro molybdenum (Fe-Mo), ferro vanadium (Fe-V), ferro  tungsten (Fe-W), ferro niobium (Fe-Nb), ferro titanium (Fe-Ti), ferro aluminum (Fe-Al), ferro boron (Fe-B). There are some noble ferroalloys which are having more than one non ferrous metal as alloying elements. Examples are ferro silico magnesium (Fe-Si-Mg), ferro silico zirconium (Fe-Si-Zr), ferro nickel magnesium (Fe-Ni-Mg) etc. Fig 1 Noble Ferroalloys Ferro nickel Fe-Ni is used for alloying in the production of stainless and construction steels. Laterite ore is the main raw material for the production of Fe-Ni. Laterite ore is characterized by a relatively low nickel content and a high moisture content together with chemically bound water in the form of hydroxide. Typical laterite ore contains 1 % to 3 % Ni and a moisture content of 5 % to 10 %. Besides laterite ore, coke and/or coal is needed as a reducing agent, since Fe-Ni production takes place by a carbothermic process. Fe-Ni can also be produced from secondary raw materials, such as...

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...

Deoxidation of Steel Sep03

Deoxidation of Steel

Deoxidation of Steel  Steel making process consists of refining of hot metal to steel which is done under oxidizing atmosphere. During refining process oxygen get dissolve in steel. The following are the main sources of oxygen in steel. Oxygen blowing Use of oxidizing slags and iron ore during the steel making processes Picking of atmospheric oxygen by the liquid steel during the teeming operation Oxidizing refractories of the lining Rusted and wet scrap. Deoxidation is the last stage in steelmaking. During making of steel, the steel bath at the time of tapping contains 400 to 800 ppm activity of oxygen. Deoxidation is carried out during tapping by adding into the teeming ladle appropriate amounts of ferro alloys or other special deoxidizers. If at the end of the blow the carbon content of the steel is below specifications, the liquid steel is also recarburized in the teeming ladle. However, large additions in the teeming ladle have the adverse effect on the temperature of the liquid steel. Solubility of oxygen in steel is negligibly small. During solidification of molten steel, excess oxygen is rejected by the solidifying steel. Solubility of oxygen in liquid steel is 0.23 % at 1700 deg C. It decreases during cooling down process and then drops sharply during the solidification of liquid steel reaching 0.003 % in solid steel. The excess oxygen liberated from the solid solution oxidizes the components of steel such as C, Fe, and alloying elements resulting into blowholes and non metallic inclusions entrapped within the cast steel structure. Both blowholes and inclusions have considerable effect on the mechanical properties and impact adversely the steel quality. In order to prevent oxidizing of steel components during solidification the oxygen content of liquid steel need to be reduced. This is done by deoxidation of steel which...

Submerged Arc Furnaces Jul15

Submerged Arc Furnaces...

Submerged Arc Furnaces  industrial utilization of electrical energy started with the development of the dynamo machine by Werner von Siemens. Electric arc furnaces have been used for many years both for the melting of scrap iron (open arc furnaces) and for reduction processes (submerged arc furnaces). In case of the submerged arc furnace (SAF), ore and reducing agent are fed to the furnace continuously from the top so that the electrodes are buried in the mix and the arc is submerged. The furnace is named submerged-arc furnace since the arc is submerged. The most common physical arrangement consists of a circular bath with three vertical electrodes arranged in a triangle. Six electrode furnaces with circular or rectangular baths are also used but they are less common. Submerged arc furnaces have found their application in more than 20 different main industrial areas such as ferro alloy, chemical industry, lead, zinc, copper, refractory, titanium oxide, recycling, phosphorus etc. A typical schematic diagram of a submerged arc furnace for ferro chrome production along with material balance is given at Fig.1 Fig 1 Typical schematic diagram of a submerged arc furnace for ferro chrome production along with material balance.  History  The increasing demand for ferro alloys and deoxidation agents in steel making in the beginning of the twentieth century led to the development of the first submerged arc furnace. The construction of the first SAF was started in 1905. This 1.5 MVA unit was installed in Horst Ruhr, Essen, Germany for the production of calcium carbide. It was successfully commissioned in 1906 and was based on DC (direct current) technology. Since then a large number of SAFs (both with DC and AC based furnaces) have been commissioned with diverse applications. Today, the majority of submerged arc furnaces are...