Desulfurization Of Steel Research Articles

Analysis of the influence of adding CaF2 and Na2O to steel desulfurizing mixtures using computational thermodynamics

Steel desulfurization mixtures of the CaO-Al2O3 system are the most industrially used. These mixtures require an amount of solid CaO to keep them always saturated in CaO. The aim of this paper is to study the influence of adding CaF2 and Na2O on the desulfurization efficiency of CaO-Al2O3 system mixtures. Desulfurizing steel mixtures capable of producing steels with sulfur content of less than 0.0020% were formulated. Desulfurizing mixtures based on CaO-Al2O3-flux were prepared with fluxes CaF2 and Na2O. All mixtures presented 95% of liquid phase and 5% of solid CaO, which, according to the literature, are the most efficient slags of this system. The equilibrium conditions were simulated using the composition of the mixtures and the steel by means of computational thermodynamic software. In these simulations, the activities of the slag components, the percentage of solids and liquids, the slag viscosity, and the equilibrium sulfur content were determined. The experimental tests were carried out in an induction furnace at 1600 °C. In addition, data on sulfide capacity (Cs), sulfur partition (Ls) and optical basicity (ʌ) of the initial mixtures, were calculated. The results of the simulations show that all mixtures have thermodynamic potential to reach the target of sulfur content set for this work. The mixtures with CaF2 proved to be the most efficient. However, it is possible to obtain sulfur contents of 0.0020% using mixtures without CaF2.

Experimental Study of Refining and Modification of Steel with Si–Ca, Si–Sr, and Si–Ba Alloys

The results of thermodynamic calculations and experimental studies of the deoxidation, desulfurization, and modification of low-carbon steel with aluminum and Si–Ca, Si–Sr, and Si–Ba alloys are presented. The metal treatment with silicocalcium leads to the formation of corrosive non-metallic inclusions (CANI). The replacement of calcium-containing alloys with Ba and Sr alloys helps to clean steel from CANI, the formation of smaller complex oxysulfide non-metallic inclusions and a change in the grain size of metal. The calculated data are consistent with the experimental results.

Influence of the ESR Parameters on the Removal of Sulfur

The influence of the ESR parameters, namely, the flux composition, the melting rate, the electric current, the type of power supply, and the ac frequency, on the removal of sulfur is considered. These parameters are shown to play a key role in the removal of sulfur. To study the influence of the type of power supply on the desulfurization of 30Kh13 steel during ESR, we remelted ingots using both an alternating and direct current of both polarities under comparable (except for a power supply) conditions The experimental results demonstrate that the removal of sulfur for a direct current of both polarities is lower than in the case of an alternating current and that the reversed polarity leads to better desulfurization than the straight polarity does. The maximum desulfurization of ac ESR is 83%, and the desulfurization by ESR using a direct current of straight and reversed polarity is 33 and 72%, respectively.

Development of the organization of rational schemes for the use of technogenic waste in the processes of off-treatment of steel intermediate

The results of the experimental verification of the efficiency of complex out-of-furnace treatment of low carbon steel using a test mixture based on man-made waste, which is fed partly to the melting unit at the end of the oxidation period of melting and partly by pouring under a stream of liquid metal. is the use of slag-forming materials obtained by joint heat treatment of mixtures of components containing the above mentioned oxides and carbonaceous material of vegetable origin. Their weight ratio in the initial mixture is determined by the purpose and properties of the finished product. The positive technological effects that are achieved by applying the developed method of after-treatment will in future provide favorable conditions for the effective conduct of microalloying, modification, vacuuming and stable casting of low-quality and ultra-low carbon steel. A slight decrease in the temperature of the steel intermediate in the implementation of the method is about 10 - 15 ° C, which is easily compensated for the installation of the ladle, and a slight increase in electricity consumption is compensated by the effects achieved in the processing of low-carbon steel intermediate. Obtaining a higher degree of desulfurization and deoxidation of steel, as well as reducing the contamination of Al2O3 steel and improving the ecological purity of the process can be achieved by reducing the composition of the SHS used in the first stage of processing, the amount of slag aluminothermal production of ferromanganese and complete exclusion of melting, melting weight ratios of powdered waste production of lime, aluminum-thermal slag production of ferromanganese, sludge neutralization of electrocorundum and carbide cr emnia.

Thermodynamic Simulation of the Influence of the Temperature and the Basicity of a Boron-Containing Slag on Steel Desulfurization

The results of thermodynamic simulation of the desulfurization of a medium-carbon steel by slags of the CaO–SiO2–MgO–Al2O3–B2O3 system are presented. The HSC Chemistry 6.12 software package is used for the simulation. The thermodynamic simulation is performed for 20 various chemical compositions of slags with various B2O3 contents (1–4%)1 and basicities ((CaO)/(SiO2) = 2–5). The computations are performed using the Equilibrium Compositions module in the temperature range from 1500 to 1700°C with an increment of 50°C at a gas phase pressure of 0.1 MPa. The main results of the calculations are presented as the dependences of the change in the sulfur content in steel [S] on the temperature, the content of B2O3, and the slag basicity. An increase in the temperature of metal desulfurization from 1500 to 1700°C exerts a favorable effect on the sulfur content for the studied range of slag basicities. In particular, the sulfur content in steel decreases from 0.012 to 0.009% when steel is processed with the slag having 3% B2O3 and a basicity (CaO)/(SiO2) = 2. A positive effect of an increase in the slag basicity from 2 to 5 on metal desulfurization is observed: the degree of desulfurization increases from 61.1 to 97.2% at 1600°C and 3% B2O3 content in the slag. As the B2O3 content in a slag increases from 1 to 4%, its refining properties decrease significantly in the range of basicity not higher than 2. In the range of high slag basicities (3–4), the negative effect of acidic oxide B2O3 on the refining properties of the slag decreases, providing low sulfur contents (which do not exceed [S] = 0.003–0.004% at 4% B2O3). At a slag basicity of 5, the sulfur content in steel decreases to 0.001%, all other things being equal. The simulation results can be used for the calculation of steel desulfurization processed by slags containing B2O3.

EXTRA-FURNACE STEEL PROCESSING BY RECYCLED SECONDARY ALUMINUM WASTE

The paper presents the results of research on the use of recycled aluminum waste (RAW) during extra-furnace steel processing in ladle refining furnace. It has been established that simultaneously with the deoxidation of refining slags before desulfurization of steel, their liquid mobility increases, which eliminates the need for using fluorspar for these purposes.A thermodynamic analysis of possible reactions of formation of aluminates and calcium aluminosilicates in the refining slag has been carried out. It has been suggested that the cause of thinning of refining slags from the addition of RAW is the formation of a number of low-melting eutectics containing aluminates and calcium aluminosilicates. The composition of briquettes based on RAW for liquefaction of refining slags is proposed. Dependence of the friability and breaking load of briquettes on the content of CaO, the temperature and drying time is established. The data on the composition and properties of the refining slag after treatment with a diluent based on RAW are given.

Thermodynamic Modeling of Metal Desulfurization with Boron-Containing Slags of the CaO–SiO2–MgO–Al2O3–B2O3 System

In thermodynamic modeling of the desulfurization of steel by CaO–SiO2–MgO–Al2O3–B2O3 slag on the basis of HSC 6.12 Chemistry software (Outokumpu), the influence of the temperature (1500–1700°C), the slag basicity (2–5), and the B2O3 content (1–4%)1 on the desulfurization is analyzed. It is found that the sulfur content is reduced with increase in the temperature from 1500 to 1700°C, within the given range of slag basicity. At 1600°C, the sulfur content in the metal is 0.0052% for slag of basicity 2; at 1650°C, by contrast, its content is 0.0048%. Increase in slag basicity from 2 to 5 improves the desulfurization, which increases from 80.7 to 98.7% at 1600°C. If the B2O3 content in the slag rises, desulfurization is impaired. At 1600°C, the sulfur content in the metal may be reduced to 0.0052 and 0.0098% when using slag of basicity 2 with 1 and 4% B2O3, respectively; in the same conditions but with slag of basicity 5, the corresponding values are 0.00036 and 0.00088%, respectively. Note that desulfurization is better for slag without B2O3. According to thermodynamic modeling, metal with 0.0039 and 0.00019% S is obtained at 1600°C when using slag of basicity 2 and 5, respectively, that contains no B2O3. The results obtained by thermodynamic modeling for the desulfurization of metal by CaO–SiO2–MgO–Al2O3–B2O3 slag of basicity 2–5 in the range 1500–1700°C are consistent with experimental data and may be used in improving the desulfurization of steel by slag that contains boron.

Material expenditures in deep desulfurization of steel in the ladle–furnace unit

The desulfurization of steel in a 160-t casting ladle is investigated. On that basis, a technology for reducing the sulfur content of low-carbon and low-alloy pipe steel to 0.001–0.003% is developed. The material expenditures in deep desulfurization of steel in a 160-t ladle–furnace unit are assessed.

Influence of Silicon on Desulfurization of Al-Killed Steel by CaO-Al2O3Slag Contained FeO and MnO

Industry trials of slag-washing desulfurization in LD tapping process are performed to study the influence of silicon on desulfurization of Al-killed steel using CaO–Al2O3 slag contained FeO and MnO. Influence of silicon on desulfurization is found to be great, while the influences of aluminum and manganese on desulfurization are negligible. Oxygen activity at slag–steel interface together with the (FeO + MnO) content in slag, decreased with the rise of silicon content, which is considered as the main reason of different desulfurization efficiencies between Si-free steel and Si-containing steel. Oxygen activity at slag–steel interface is reduced more sharply by increasing the silicon content than that by increasing the aluminum content. As a result, desulfurization efficiency can be enhanced significantly with the rise of silicon content, rather than the aluminum content. Furthermore, the influence of silicon on desulfurization can be magnified if the slag contained FeO and MnO, while negligible for the slag with few FeO and MnO.

Researches concerning influence of magnesium, aluminum and titanium lime on steel desulfurization

The paper presents the results of laboratory experiments on steel desulphurisation with slag from the system MgO-Al2O3-TiO2. To determine the influence, on the desulphurisation process, of the titanium oxide added in calcium aluminate slag, we experimented, in the laboratory phase, the steel treatment with a mechanical mixture consisting of lime, aluminous slag and slag obtained from the titanium making process through the aluminothermic technology. The steel melting was carried out in an induction furnace of 10 kg capacity, existent in the "Metallic Melts" laboratory of the Engineering Faculty of Hunedoara. During the research, we aimed to establish correlation equations between the sulphur distribution coefficient and the slag components (MgO, Al2O3, TiO2). The data obtained in the experiments were processed in MATLAB programs, resulting multiple correlation equations, which allowed the elucidation of some physical-chemical phenomena specific to the desulphurisation processes.

O8] Development of a thermodynamic database for the Na2O-FeO-Fe2O3-SiO2-S system for the de-sulfurization of molten steel

O8] Development of a thermodynamic database for the Na2O-FeO-Fe2O3-SiO2-S system for the de-sulfurization of molten steel

A numerical analysis as a good tool for a prediction of final sulphur steel ladle content

This work presents the industrial results of sulfur level prediction at the end of vacuum degassing (VD) of low carbon Al-Si killed steels. The effect of plant conditions, such as slag chemistry, temperature, oxygen levels of the molten steel, and slag weight on desulphurization was investigated based on the measured results and thermodynamic calculations. The variables which influence steel desulfurization such as the sulfur capacity, the initial sulfur content, and the amount of ladle slag at the end of the VD process are also defined. The desulfurization procedure was numerically analyzed using the results of 31 heats under real plant conditions in which the measured final sulfur content had been reduced to less than of 10 ppm. A method for prediction of the slag amount based on the material balance of sulfur and aluminum is also presented. The values of the sulfur capacity were determined according to the well-known KTH and optical basicity based models. The obtained results of the regression equation show a predictive final sulfur level ability of R=0.911. This was proved as satisfactory.

Desulfurization of Liquid Steel by Passing Steel Droplets through a Slag Layer

In order to develop a process to effectively desulfurize liquid steel, a desulfurization of liquid steel was performed in a specially designed equipment. Reaction between a layer of liquid slag (CaO–MgO–Al2O3) and multiple steel droplets generated from a liquid steel was attempted in a two-zone heating furnace. The liquid steel containing S was melted in a crucible at an upper zone of the furnace, and droplets were generated by falling the liquid steel through a hole at the bottom of the upper crucible. The droplets were allowed to free-fall and passed through the liquid slag melted in the other crucible at a lower zone of the furnace. The liquid steel accumulated at the lower crucible was sampled and was analyzed for the S content. It was found that desulfurization took place in two distinctive modes: dynamic and static mode. A model equation was formulated in order to interpret the obtained experimental data, and apparent rate constants for the dynamic mode (kd) and the static mode (ks) were obtained. While the ks was in the order of 10−5 m sec−1 which is in agreement with the literature data obtained by usual metal-slag reaction, the kd was much higher than the ks, as high as in the order of 10−3 m sec−1. In order to maximize the desulfurization rate by the droplets/liquid slag, it is required to keep the slag having higher sulfide capacity while the desulfurization takes place. It further requires an even distribution of the droplets in the slag layer.

Erratum to “Desulfurization of Liquid Steel by Passing Steel Droplets through a Slag Layer” [ISIJ Int. 55(8): 1581–1590 (2015)

Erratum to “Desulfurization of Liquid Steel by Passing Steel Droplets through a Slag Layer” [ISIJ Int. 55(8): 1581–1590 (2015)

Increasing the efficiency of the desulfurization of structural steel for gas- and oil-main pipelines

The main laws of refining Kh70 structural steel melted according to standard ASTME 45-97 are studied by statistical analysis.

Study of Deoxidization and Desulphurization in Slag Washing Process of Al-Killed Steel

In order to reduce the production cost, In one factory product the SPHC steel of general requirements using slag washing process （BOF→Slag washing oxygen alloying→Ladle argon-blown→CC）, the system study was analyzed about deoxidization and desulphurization behavior of slag washing process. The results of the study show that, when the content of Als 300~500ppm, dissolved oxygen 3~6ppm, the steel desulfurization rate remains stable at 35% to 48%, the average desulfurization rate is 42%. The process of the [N] content, increasing [S] are lower than the LF refining, the operation is simple and can meet the metallurgical requirements.

Effect of Silicon on the Desulfurization of Al-Killed Steels: Part II. Experimental Results and Plant Trials

Recent observations suggest that increased silicon levels improve ladle desulfurization of aluminum-killed steel. A kinetic model was developed and presented in part I of this paper, demonstrating that increased silicon levels in steel suppress the consumption of aluminum by parasitic reactions like silica reduction and FeO/MnO reduction, thus making more aluminum available at the interface for desulfurization. The results are increases in the rate and the extent of desulfurization. Predictions were compared with laboratory induction furnace melts using 1 kg of steel and 0.1 kg slag. The experimental results demonstrate the beneficial effect of silicon on the desulfurization reaction and that alumina can be reduced out of the slag and aluminum picked up by the steel, if the silicon content in the steel is high enough. The experimental results are in close agreement with the model predictions. Plant trials also show that with increased silicon content, both the rate and extent of desulfurization increase; incorporating silicon early into the ladle desulfurization process leads to considerable savings in aluminum consumption.

Ladle desulfurization of steel by solid slag mixtures

When using solid slag mixtures immediately after discharge from the converter, the desulfurization of the steel is greatly improved. The refined slag formed in the casting ladle permits the removal of more than 40% of the sulfur from the steel. Reducing the initial sulfur content in the metal shortens the subsequent ladle treatment by 10 min and lowers the power consumption.

Effect of Silicon on the Desulfurization of Al-Killed Steels: Part I. Mathematical Model

Recent observations suggest that increased silicon levels improve ladle desulfurization of aluminum-killed steel. While the overall desulfurization reaction of Al-killed steels does not show a direct role of silicon in desulfurization, model calculations are presented which test the idea that silicon suppresses the reduction of silica which can consume aluminum at the slag/metal interface. Consumption of aluminum would increase the oxygen potential at the slag/metal interface and decrease the sulfur partition coefficient between slag and metal. The model considers the coupled reactions of the reduction of silica, iron oxide, and manganese oxide in the slag and desulfurization of the steel by aluminum. The results show that silicon can indeed suppress consumption of aluminum at the slag/metal interface by side reactions other than desulfurization, with silicon affecting both the kinetics and the equilibrium of desulfurization.

Study on the Desulfurization Gypsum and Steel Slag Blended Clinker-Free Cementing Material

Based on orthogonal test with steel slag and desulfurization gypsum as main raw material, mixed appropriate amount slag and compound addition a little of activator, we explored the slag dosage, the proportion of the combined admixture activator and the desulfurization gypsum dosage impact on the performance of clinker-free cementing material, such as strength, stability, standard consistency water quantity and setting time. The results showed that the best mix proportion of cementing material with slag content 40% and activator A:activator B is equal to 2.78:2.22. We explored the structure and composition of hydration products further more by micro-analysis, such as SEM, EDS and so on. We can found that the cementing material hydration products similar with hydration products of silicate cement. The cementitious material hydration with Afm crystal content increased significantly. The Aft crystal generated in early hydration(3d) gradually transformed into Afm crystal in late hydration(28d) ,and the structure becomes more dense.