Induction Furnace Refractory Lining with Silica Ramming Mass...

Induction Furnace Refractory Lining with Silica Ramming Mass Induction furnaces are used for melting cast iron, mild steel and various alloy steels in foundries and making of steel in mini steel plants using sponge iron. Lining is the important part of induction furnace. Furnace performance is directly related to the performance of its lining. Well laid and stabilized lining results in smooth working of furnace, optimum output, and good control of the metallurgical reactions. The lining practice best suited to a particular furnace depends upon the capacity and design of the furnace, operation practice adopted during making of a heat, and furnace output. For successful and consistent performance of the lining, the important aspects are (i) use of proper grade and quality of the lining material, (ii) careful and systematic lining practice, and (iii) consistency in working conditions.  Fig 1 shows the installed refractory lining of a coreless induction furnace, Fig 1 Installed refractory lining of a coreless induction furnace The characteristics of the lining material needed for consistent lining life include (i) thermal characteristics which means that it has to withstand the stresses developed by thermal cycles during the furnace operation, (ii) chemically inert to metal being melted, (iii) structural strength under operating conditions, (iv) high erosion resistance, (v) ease of installation, (vi) reparability of the lining, (vii) ease of dismantling, and (viii) economics. As such, it is very difficult to judge the suitability of a particular lining under various conditions like operating temperature, metal being melted, the type of formed slag, and furnace capacity. Chemical inertness to the liquid metal can be achieved by using acid and neutral lining for the acidic slag and neutral or basic lining for the basic slags. Normally, the selection of refractory for the furnace lining is...

Iron Carbide

Iron Carbide Iron carbide is a high melting point, non-pyrophoric, strongly magnetic synthetic compound obtained in granular or powder form. It is composed of three atoms of Fe and one atom C and its chemical formula is Fe3C. The commercial iron carbide consists of around 90 % total iron and around 6 % to 6.5 % of total carbon. The primary use of the product is as a metallic charge during steelmaking for substitution of hot metal, direct reduced iron, or steel scrap. Iron carbide is an intermetallic compound of iron and carbon. It is, more precisely, intermediate transition metal carbide. Its stoichiometric composition consists of 6.67 % carbon and 93.3 % iron (Fe) by weight. It has an orthorhombic crystal structure (Fig 1). It is a hard, brittle material and normally classified as a ceramic in its pure form. It is a frequently found and important constituent in ferrous metallurgy. While iron carbide is present in most steels and cast irons, it is produced as a raw material by the iron carbide process, which belongs to the family of alternative ironmaking technologies. Fig 1 Crystal of iron carbide Iron carbide is a premium quality feed for steelmaking in electric arc furnaces and basic oxygen furnaces. It is available as dark gray granules or powder. It offers matchless metallurgical advantages and outstanding cost savings. It has a density of 7.64 kg/cu m and is thus slightly denser than the liquid iron, which has a density of 6.98 kg/cu m. The iron carbide is composed of three atoms of Fe and one atom C and is also known as cementite. Cementite is an intermetallic compound which is hard, brittle, and metastable because it tends to decompose in ferrite (or austenite) and graphite according to the reaction Fe3C = 3 Fe + C. In fact, this transformation is not...

Tensile Testing of Steel...

Tensile Testing of Steel Sample of steel is subjected to a wide variety of mechanical tests to measure their strength, elastic constants, and other material properties as well as their performance under a variety of actual use conditions and environments. Tensile test is one of them. Other tests are hardness test, impact test, fatigue test, and fracture test. These mechanical tests are used to measure how a sample of steel withstands an applied mechanical force. The results of such tests are used for two primary purposes namely (i) engineering design (e.g. failure theories based on strength, or deflections based on elastic constants and component geometry), and (ii) quality control either by the producer of steel to verify the process or by the end user to confirm the material specifications. Uniaxial tensile test is known as a basic and universal engineering test to achieve material parameters such as ultimate tensile strength (UTS), yield strength (YS), % elongation, % area of reduction and young’s modulus. Tensile testing is done for many reasons. The results of tensile tests are used in selecting materials for engineering applications. Tensile properties are often included in material specifications to ensure quality. Tensile properties are also normally measured during development of new materials and processes, so that different materials and processes can be compared. Also, tensile properties are generally used to predict the behaviour of a material under forms of loading other than uniaxial tension. Safely withstanding the expected maximum load without permanent deformation (or to stay within the specified deflection) is a basic requirement for a steel product. The ‘resistance’ against the load is a function of the cross-section and the mechanical properties (or in other words the ‘strength’) of the steel material. Tensile testing is done to determine the mechanical...

Corrosion in Steels – Its Types and Testing...

Corrosion in Steels – Its Types and Testing Corrosion is a universal natural process. The effect of corrosion is seen in every-day life in the form of rusted steel parts. Corrosion has a huge economic impact. About a fifth of the global annual steel production goes towards simply replacing steel parts damaged by corrosion. Even though it involves higher up-front cost, correct and efficient corrosion protection at the source helps save money and resources in the long run. Failure due to corrosion can result into dramatic consequences. Corrosion is the gradual degradation of a metal by chemical, often electrochemical reaction with the surrounding environment. Corrosion results into loss of material properties such as mechanical strength, appearance, and impermeability to liquids and gases. Whether steel is corrosion resistant in a specific environment depends on the combination of the chemical composition of steel and the aggressiveness of the environment. As per ISO 8044:2010, corrosion is the physicochemical interaction between a metal and its environment, which results in changes in the metal’s properties and which may lead to significant functional impairment of the metal, the environment, or the technical system of which they form a part. Corrosion takes place when there is a change in the steel’s or system’s properties which may lead to an undesirable outcome. This can range simply from visual impairment to complete failure of technical systems which cause great economic damage and even present a hazard to the people. The typical corrosion process can be regarded as the thermodynamically favoured reverse reaction of the metal-winning (extraction) process (Fig 1). Like all chemical reactions, corrosion processes take place when conditions favour the related chemical reactions (thermodynamics). Then, potential other factors drive the speed of the reaction (kinetics). Fig 1  Chemical reactions of iron during...

Preference of Steel as a Material of Construction...

Preference of Steel as a Material of Construction Steel is one of the most widely used materials, particularly in construction, engineering, white goods, and automobile industries. Steel is also used widely in the manufacture of electrical motors, power generation (nuclear, conventional fuels and wind), power transmission, and railway network. It is also used for gears and engines where it has to be very tough and withstand high temperatures. There is a group of steels known as ‘Advanced High Strength Steels’ (AHSS), which are specially treated steels that can be rolled very thin without losing the element of strength needed for the specific purpose.  These steels are particularly useful for the manufacture of automobiles, helping to reduce the overall mass and thus decrease the consumption of the fuel. Steels with a thin coating of tin are used to make cans for beverages and food. Steels coated in various ways with zinc are used in roofing, for example, and in automobiles as the zinc gives protection to steel against corrosion. It is estimated that there are more than 20,000 million tons of steel in use, which means that there is more than 2 tons of steel is in use for every person living on the Earth. The construction industry is the main user of steel. It uses steel from small buildings to huge bridges and uses it in multiple ways even within a single construction.  A bridge, as an example, may use steel in the huge suspension ropes, the steel plate flooring for the road, the beams for the columns, and for the safety barriers and lighting columns. A large amount of steel is also used in the reinforce concrete. In fact, steel is either used or used to produce all the items needed in our daily life....

Alumina and its Role in Iron and Steelmaking...

Alumina and its Role in Iron and Steelmaking Alumina is a chemical compound of aluminum (Al) and oxygen (O2) with the chemical formula aluminum oxide (Al2O3). It is the most commonly occurring of several aluminum oxides. It is significant in its use to produce aluminum metal. It is being used as an abrasive material because of its hardness. It is also being used as a refractory material owing to its high melting point. Aluminum oxide is an amphoteric substance. It can react with both acids and bases, acting as an acid with a base and a base with an acid, neutralizing the other and producing a salt.  It is insoluble in water. Aluminum oxide has a white solid appearance and is odorless. The molar mass of aluminum oxide is 101.96 grams per mole. Specific gravity of alumina is 3.986. It is insoluble in water. Melting point of aluminum oxide is 2072 deg C while the boiling point is 2977 deg C. Alumina affects the processes of producing iron and steel during the production of iron and steel. Besides alumina is a very important refractory material for the lining of furnaces and vessels in iron and steel plants. Role of alumina in ironmaking Alumina during ironmaking enters the process through impurities in the input materials mainly iron ore. Alumina affects the sintering of iron ore. The most harmful effect of alumina is to worsen the RDI (reduction degradation index) value of sinter. RDI value increases as the alumina content rises. It is seen that within a 10 % to 10.5 % CaO content range, an increase of 0.1 % in the alumina content raises the RDI by 2 points. The strength and quality of sinter deteriorate as the alumina content rises. Alumina promotes the formation of SFCA (silico ferrite of calcium and aluminum), which is beneficial for sinter strength, but the strength of the ore components is lower, since a...