Ferrosilicon Addition Research Articles

Effect of Silicon Additions on the Wear Properties of Grey Cast Iron

This paper investigates the wear characteristic of grey cast iron composition under dry lubrication conditions. The effects of sliding speed, applied load, time and percentage of ferrosilicon additions, on the wear rate of grey cast iron were studied. The set of experimental data were taken in a controlled and sequential manner. Scanning electron microscope was used to examine the morphology of the samples as well as the worn out surfaces. Linear regression equation and analysis of variances (ANOVA) showed that the main effect of silicon additions, load and speed variable are more pronounced on the wear behaviour of the grey cast iron. Also, the result showed that the additions of silicon improved the wear resistance of the grey cast iron as the wear parameters such as speed, load and time varied. The study showed that wear transition occurred at 3.2% silicon addition.

Evaluation of Zefreh Dolomite (Central Iran) for Production of Magnesium via the Pidgeon Process

This study evaluates the production of magnesium metal from the Zefreh dolomite ore of Central Iran using the Pidgeon process. The investigation consisted of mineralogical and chemical characterization of the dolomite ore, calcining, chemical characterization, LOI (loss on ignition) determination, reduction tests on the calcined dolomite (dolime), using Iranian (Semnan) ferrosilicon and mineralogical, and chemical characterization of the reactants and products. Calcining of dolomite samples was carried out at approximately 1400°C in order to remove CO2, moisture, and other easily volatilized impurities. The dolime was then milled, along with ferrosilicon, thoroughly mixed, and briquetted. The briquettes were heated at 1125°C--1150°C and 500 Pa in a tube reactor for 10--12 hours to extract the magnesium. The ferrosilicon to dolime ratio was determined based on the chemical analyses of the two reactants, using as a guide, and Mintek's Pyrosim software package. Magnesium extraction varied with ferrosilicon addition and with the dolime used, and reach about 80% under optimal conditions. The levels of major impurities encountered in the magnesium crown were similar to those in the crude metal production.

Understanding stainless steelmaking through computational thermodynamics: Part 3 – AOD converting

The major issue in stainless steelmaking is the difficulty of oxidising carbon from molten steel without also oxidising large proportions of expensive chromium. This can, however, be achieved by reducing the partial pressure of the gaseous product of carbon oxidation, carbon monoxide, by dilution with argon. Modern stainless steelmaking is dominated by duplex processes which prepare a high carbon melt in an electric arc furnace, and then decarburise it in an argon–oxygen decarburisation (AOD) converter. In this work, the thermodynamic basis of preferential carbon oxidation by dilution of oxygen with argon is discussed, together with a review of AOD practice. The AOD process was simulated using computational thermodynamics software to illustrate the way in which it can achieve very low carbon levels in the molten steel bath without excessive co-oxidation of chromium. The slag reduction stage using ferrosilicon additions was also modelled and shown to be able to recover almost all oxidised chromium from the slag, limited only by the accompanying increase in the silicon content of the steel. The models, although simple and easy to develop, correctly predicted all trends in output variables as input parameters were changed and often matched plant data very well. The models provide a valuable learning tool for those interested in pyrometallurgical processing in general, and stainless steelmaking in particular.

Research on Smelting Vanadium Steel by Silicothermic Reduction Direct Alloying with V<sub>2</sub>O<sub>5</sub>

The basic thermodynamic analysis of silicothermic reduction during direct alloying to smelting vanadium steel with V2O5 was discussed in this paper. The high-temperature carbon tube furnace and medium frequency vacuum induction furnace were used to study the phase compositions of the reduction products and the change law of the yield of vanadium when V2O5 was reduced by ferrosilicon. The research shows that the main phases of the silicothermic reduction products were VSi2、FeVO4 and Ca2SiO4 under the condition of using CaO to restrain the volatile of V2O5. Yield of vanadium was gradually improved with the increase of ferrosilicon during the direct alloying. The yield of vanadium in the steel is as high as 95.25% when the addition of ferrosilicon is 35%.

Study on High Performance Fe<sub>3</sub>Si-Si<sub>3</sub>N<sub>4</sub>-SiC Composite Preparation and its Application in Blast Furnace

Excellent Fe3Si-Si3N4-SiC composites were successfully prepared with FeSi75 and SiC as main starting materials by nitridation reaction(at 1300°C for 8Hrs). The effect of ferrosilicon alloy addition amount on material properties was studied; the ferrosilicon nitridation mechanism was analyzed through chemical thermodynamics; phase composition, microstructure, alkali resistance of products were also investigated. The results show that when ferrosilicon addition amount is 12wt%, the comprehensive property of Fe3Si-Si3N4-SiC is the best. The nitridation products are fiber-like α-Si3N4 and rod-like β-Si3N4, which makes better mechanical behavior due to fiber reinforcement; a great deal of Fe3Si intermetallic compounds uniformly distribute in matrix, which is one of the products of Fe-Si nitridation and as a plastic phase forming in grain boundary optimizes the performance of products. Chemical thermodynamic analysis shows that the fiber-like α-Si3N4 is formed by SiO(g) and N2(g) reaction which also increases the rate of nitridation. Fe3Si-Si3N4-SiC material has good performance. Now it has been successfully applied to one 2000M3 domestic steel plant, the blast furnace operation goes well.

Understanding stainless steelmaking through computational thermodynamics Part 1: electric arc furnace melting

Stainless steel alloys are widely used in many important applications but their production presents difficulties because they contain expensive chromium, which can be extensively oxidised during decarburisation to the very low carbon levels required. Modern stainless steelmaking largely avoids this problem by having two distinct stages and is therefore described as duplex practice. Molten high carbon stainless steel is produced in an electric arc furnace and then the melt is decarburised in an argon–oxygen converter or a vacuum oxygen decarburising converter. In this work, computational thermodynamics has been used to examine the major reactions occurring in the electric arc furnace and to show the effect of various process variables on chromium recovery. It was shown that significant oxidation of the scrap must occur during melting, and that subsequent carbon/oxygen injection initially oxidises some chromium, but then mostly oxidises the added carbon. Chromium was predicted to exist in the slag as CrO and CrO1·5 in almost equal proportions. Increasing the temperature should improve chromium recovery but results in less benefit than expected due to the decreasing activity coefficients of CrO and CrO1·5 and the increasing oxygen partial pressure. Ferrosilicon additions reduce chromium oxides from the slag, but much of the silicon simply dissolves into the steel. Computational thermodynamics is seen to be a very effective educational tool for gaining an understanding of smelting processes.

Study of the Effect of Addition of ferrosilicon in Mechanical and Chemical Properties of Concrete Mix

Study of the Effect of Addition of ferrosilicon in Mechanical and Chemical Properties of Concrete Mix

Effect of ferrosilicon addition on the composition of inclusions in 16Cr-14Ni-Si stainless steel melts

The silicon deoxidation equilibrium between the 16Cr-14Ni-1.5Mn-Si melts and the CaO-SiO2-8MgO-5CaF2 (basicity=1.8) slag at 1743 K was investigated to understand the effect of aluminum and silicon contents on the composition of inclusions. Therefore, the ferrosilicon alloys with different aluminum content were chosen based on the preceding objective. In addition, the phase stability diagram of the inclusions was computed using commercial thermodynamic software based on the Gibbs energy minimization principles. The content of MnO in the inclusions sharply decreases with increasing silicon content when the steel melts were deoxidized by the ferrosilicon alloys containing high aluminum (FeSi-H). The content of SiO2 in the inclusions slightly increases with increasing silicon content when the FeSi-L is used, while a maximum value is shown at [Si]=1.5 pct when the FeSi-H is used. The content of MgO in the inclusions increases by increasing the content of silicon, regardless of the kinds of ferrosilicon alloys. The use of the FeSi-L as a deoxidizer could suppress the formation of Al2O3 in the inclusions, while the content of Al2O3 increases with increasing silicon content when the FeSi-H is used. When the FeSi-H is used as a deoxidizer, the inclusions are the glassy type with the composition of Mn-silicates at [Si]≤1.3 pct, while the Mg(Ca)-silicates with the composition of the forsterite phase are observed in the steel composition of [Si]=3.3 pct. When the steel melts were deoxidized by the FeSi-L alloys, the inclusions are the glassy-type Mn-silicates at [Si]=0.8 pct, while the Mn-silicates containing the cristobalite phase are observed at [Si]=1.5 to 2.4 pct. In the composition of [Si]=3.3 pct, the Mg-silicates with the composition of the rhodonite phase are observed. The log(X SiO2/X MnO) of the inclusions linearly increases by increasing the log [a Si · a O / a Mn] with the slope close to unity when the FeSi-L is used as a deoxidizer, while the slope of the line is about 2 times greater than that of the expected value when FeSi-H is used. The log (X MgO/X MnO) of the inclusions linearly increases by increasing the log [a Mg/a Mn] with slopes greater than the expected value of unity.

Reduction of CO2 Emissions from Integrated Steelmaking by Optimised Scrap Strategies: Application of Process Integration Models on the BF–BOF System

In integrated steelmaking there are a number of means to reduce CO 2 emissions. One approach is to increase the metallic Fe input to the production system. A common belief is that scrap works as a CO 2 diluent when introduced in iron ore based steelmaking. It is not necessarily so. Scrap is a key supplementary charge material in oxygen steelmaking converters, but scrap can also be utilised in ironmaking where it will decrease the use of'reducing agents and with that also the specific CO 2 emissions. By the use of a process integration model which basically includes the primary processes of cokemaking, sintering, ironmaking and oxygen steelmaking the overall influence of scrap input on CO 2 emissions is demonstrated and commented. The influence of hot metal silicon content is elucidated by calculations with different material and process constraints. The results show that at moderate scrap rates, the reduction of CO 2 emissions is favoured by increased scrap additions to the oxygen converter. When the scrap additions to the converter balances the actual heat capacity of the bath, other means to achieve an increased scrap melting capacity can be taken into account. This include combinations of scrap addition to the blast furnace, increased silicon content in tapped hot metal, and/or addition of Ferro-silicon combined with further scrap additions to the oxygen converter. Different strategies for CO 2 emission reduction have to be suggested depending on if the objective is to minimise the site (direct) emissions or the global (indirect+direct) emissions.

Fluid dynamics simulation of chromium recovery from AOD slags during reduction with ferrosilicon additions

The kinetic and thermodynamic efficiencies of chromium recovery from the slag in an AOD process during the slag deoxidation period with ferrosilicon is a complex process affected by slag basicity, temperature, the dissolution kinetics of the reducing agents, and intermixing of the slag/metal/alloy addition phases within the vessel. The present work focused on a study and simulation of the fluid dynamics and mixing behavior of ferrosilicon additions in the AOD process for the production of stainless steel. In order to visualise the mixing behaviour, a two dimensional slice model of an AOD vessel was first built and filled with ZnCl2 solution and then covered with silicone oil in order to represent the bulk liquid steel and slag phases respectively. The injection of argon/oxygen process gases was simulated using air or helium. Particle trajectories and intermixing of the phases was monitored with a high speed camera. To simulate the 75FeSi additions, wooden spheres were used. A three-dimensional version of the AOD model was then constructed, in order to confirm the adequacy of the slice model. Similar particle mixing behaviour was observed. Both models demonstrated that the ascending gas/liquid plume created two asymmetric mixing zones; a smaller rapidly recirculating mixing zone adjacent to the side wall locating the tuyere(s), and a larger mixing zone in the main part of the vessel. The process efficiency during the reduction period is governed by the thermal behaviour of ferroalloy as well as the mixing efficiency in the main large mixing zone. To enhance the recovery efficiency for chromium, small Fe–Si particles are suggested, given their wide distribution within the slag phase, and their large interfacial areas and rapid melting times for Cr2O3 reduction from the slag.

Morphology of nonmetallic inclusions using silicon, aluminum, and calcium-silicon alloy in steel melt

The process of deoxidation of a 15 kg melt by silicon, aluminum, and calcium-silicon alloy was studied by continuously monitoring the dissolved oxygen potential using a solid electrolyte probe. Stable oxygen potential was established within two minutes, whether the deoxidizer was added onto the melt surface or plunged into the melt. Inclusion morphology was investigated with the help of optical and scanning electron microscopic studies. The inclusion index is dependent on the type of deoxidizer added, but was independent on the mode of addition. Thus, with ferrosilicon addition the index increased significantly which decreased very slowly on holding the melt while deoxidation with aluminum and calcium-silicon alloy resulted in a continuous decrease of the inclusion index. Evidence has been found to show that the reaction between the existing inclusion before deoxidizer addition and the deoxidizers added was also very fast.

Development of a pyrometallurgical technique to recycle stainless steel wastes

It is estimated that wastes containing over 20 million lb of chromium and 8 million lb of nickel are generated annually in the production of stainless steel in the United States. These wastes, consisting of flue dusts, swarfs and mill scale are virtually all sent to dumps and landfills because of the lack of an acceptable recycling technology. The Bureau of Mines of the United States Department of the Interior, whose activities include conservation of mineral resources by the recovery of metal values from industrial wastes, has developed a method for recovering over 80 % of the chromium and 90 % of the iron and nickel contained in pelletized mixtures of these stainless steel wastes. The Bureau's two-stage recovery technique relies on an initial reduction with carbon contained in the pellets, during meltdown in the arc furnace. This is followed by an addition of ferrosilicon to recover further chromium from the slag. The result is a master alloy suitable for recycling by charging to commercial stainless steel heats. A variation in procedure involves adding pellets directly to the production furnace to replace part of the stainless scrap charge. The technique has been validated in heats of 1 500 and 2 000 lb and more recently in industrially produced heats of 12.5 – 17 tons. Details of the pelletizing and furnacing and data on recoveries are presented.

Some aspects of graphitization induced by iron and ferro-silicon additions

The effects of the introduction of iron or ferro-silicon particles on the graphitization of carbon mixes at relatively low temperatures are described. It is shown (i) that both iron and ferro-silicon materially accelerate the rate of graphitization and that ferrosilicon is more effective than iron in this respect (ii) that by the inclusion in carbon mixes of about 20% wt. of iron or ferro-silicon leads to extensive graphitization at temperatures as low as 1400°C, (iii) that the most effective silicon content of the ferro-silicon is about 25% and the most effective particle size is in the range 50–75 μ. The mechanism of the acceleration of graphitization has been studied. It is concluded that the graphite nucleates around and within the metal particles and that it is the rapid transport of carbon atoms within the liquid metal which is responsible for the ease of graphitization observed. The mechanism by which the metal is continually dispersed throughout the carbon matrix during graphitization has also been elucidated.

The effect of ferrosilicon additions on the phase composition and properties of graphite-fireclay products

Adding 75%-ferrosilicon in amounts of 10–15 % to compositions of graphite-fireclay bodies contributes to the production of specimens whose properties are not inferior to articles made from bodies containing elemental silicon.

物理化學的諸數値より見たる製鐵製鋼法

The physico-chemical principles involved in iron and steel making process were discussed. Presence of silicon reduced solubility of the carbon in iron. From this experimental data, it was concluded that the activity coefficient of the carbon diminished with the silicon. Since the diffusion constant of the silicon in iron is about one hundredth of that of the carbon, it is considered that carbon diffuses from a high-silicon steel to a low-silicon steel, even though the carbon content of the lower silicon is the greater. In steel making practice, it was found that 15min after the addition of ferrosilicon, the concentration of the silicon in the surface layer of molten bath was several times greater than that in the bottom layer, whereas, the carbon content of the surface was less than that of the bottom layer of the bath. According to J. Chipman, the reduction of silica in blast furnace slag by the carbon in molten pig iron did not reach eguilibrium even after a long period of holding at 1525°C. This results may be interpreted so that the reduction of silica forms the high-silicon layer which interrupts contact of the slag and the carbon in molten pig iron and prevent further reduction of silica. This high-silicon layer also affected upon the rate of desulphurisation of molten pig iron. Desulphurising power of the manganese increased as temperature went down. However, at 1200°C, 1% Mn in liguid iron could not lower the sulphur content to 0.47%. On the other hand, activity coefficient of the sulphur in pig iron was about five times greater than that in pure liguid iron. Therefore, it was expected that the pig iron contained about 0.09% S might be obtained by presence of 1% Mn.