Production Of High-quality Steel Research Articles

Towards prediction of local corrosion on alumina refractories driven by Marangoni convection

Refractory materials are used in the high-temperature melting of iron and steel, which are the basic materials in various metallurgical processes and other high-temperature industrial production and technology development methods. The Marangoni effect is a key factor in the direct premature destruction of refractory materials in use and exerts a significant impact on low-cost, high-quality steel production. In this study, the area of refractory/air/slag interface was expressed and observed. Based on the previous studies, the geometrical model of corrosion groove is modified by considering the erosion and dissolution of refractory oxides. The model is used to analyze the corrosion evolution caused by the Marangoni effect. The difference between the calculated results and the experimental results is compared, and the reliability of the geometrical and corrosion models is verified for predicting the Marangoni convection influence on the service life of refractory materials.

An industrial image processing-based approach for estimation of iron ore green pellet size distribution

Green pellets are spherical objects mainly made from crushed iron and water in rotating pelletizing disk. Pellets play an important role in the process of direct reduction steel manufacturing. For high quality steel production, pellets should be of an appropriate size. Oversized pellets cannot be properly cooked in furnace and undersized pellets may pass through metal grid of the furnace, which affects the performance of the process. In most of the steel manufacturing companies, operators use sequential sampling and traditional methods to measure size of pellets, however, limited number of tested pellets, low speed of the quality control and human errors are the most common drawbacks of this method. A solution to these shortcomings is continuous monitoring and accurate measurement through a fully-automatic approach. In this paper, a method using image processing technique is proposed and verified for estimating size distribution of iron-ore green pellets. For segmentation of single and multiple pellets in images captured from live video, we have utilized morphological methods, watershed algorithm, and linear searching. Then, a Support Vector Machine (SVM) is employed for classification of segmented pellets. The proposed method has already been implemented in Mobarakeh Steel Complex, where the method was tested on about 1000 sample pellets. Results show that the accuracy of method is 95.1% in detection of single pellet elements.

Prospects for Consteel technology in Russia

The development of the Consteel process is briefly analyzed. Foreign experience with the Consteel system and its derivatives (Faststeel and Consteel Evolution) is discussed. Its introduction in Russia is expedient for the production of high-quality steel.

Numerical simulation of convection and inclusion distribution during solidification in a heavy steel ingot

Inclusions content in the steel ingot is an important index for homogeneity, and it becomes more serious for heavy steel ingots which are used for major equipment. However, knowledge about the formation of inclusion in steel ingot is limited, and modeling of inclusion distribution is still challenging, so it is of great significance to research the behavior of inclusion. In this paper, fluid flow during solidification is numerically simulated based on the equilibrium equations of mass, momentum and energy, and then inclusion distribution is modeled according to the Lagrangian Stokes trajectory method. The Results show that the inclusion distribution in the steel ingot is influenced by the flow pattern which is affected by the solidification pattern. Therefore, inclusion distribution could be controlled by the solidification front with the optimization of heat transfer condition such as the hot top design of steel ingot for the high quality steel production.

Contribution of professor Evgeny O. Paton to the development of welding materials science and production of high-quality steel

Contribution of professor Evgeny O. Paton to the development of welding materials science and production of high-quality steel

Assessment of midterm CO2 emissions reduction potential in the iron and steel industry: a case of Japan

An up-to-date techno-economic assessment was conducted on CO2 emissions reduction potential in the Japanese iron and steel industry for 2030. The following mitigation measures were investigated: (i) maximized installation of best available technologies (BAT scenario), (ii) increased use of coke substitutes in blast furnaces, and (iii) increased use of obsolete steel scrap. For measure (iii), this study assessed the obsolete scrap use in the integrated steelmaking (BF-BOF) route, rather than increasing steel production from the electric arc furnace (EAF) route. CO2 capture and storage (CCS) was not considered due to large deployment uncertainty.The results showed that 20 Mt–CO2 of emissions reductions, equivalent to 12% of the industry's total emissions in 2010, can be achieved in 2030 compared with a frozen technology scenario. More than 9 Mt–CO2 reduction was attributable to the enhanced use of obsolete scrap in the BF-BOF route. Consequently, the industry's emissions reduce by about 7 Mt–CO2 or 4% below 2010 levels. Almost all domestically recovered obsolete scrap can be fully consumed solely by increasing the scrap use in basic oxygen furnaces (BOF). Moreover, the increase in average copper concentration in the BF-BOF steel due to the increased obsolete scrap use was found unlikely to limit the production of high-quality steel products.In comparison with a scenario that only considered measure (i) and assuming a 15% real interest rate, CO2 mitigation cost curves for 2030 showed that the CO2 mitigation costs were below US$2010 20/t-CO2 for measure (ii) and around US$2010 110/t-CO2 for measure (iii). Compared to the marginal abatement costs calculated for 2030 to reduce Japan's GHG emissions by 20%–25% from 1990 levels (about US$2010 67–640/t-CO2) reported in the literature, all three measures may become economically viable.The increased use of obsolete scrap in the BF-BOF route can become an interesting option for Japanese steelmakers to stimulate the steel scrap market and achieve economical global CO2 emissions reductions while maintaining international competitiveness in the midterm future.

Effect of Slag Composition on Wettability of Oxide Inclusions

Inclusion removal is key in the production of high quality steel. The inclusions are primarily removed from liquid steel by reacting with a liquid slag phase. For efficient inclusion removal, the inclusions transfer across the steel-slag interface to dissolve in the slag. This transfer process is strongly influenced by interfacial phenomena. In this study, the dynamic wetting (θ) of a range of slags in the CaO–Al2O3–SiO2–(MgO) system on solid oxides representing inclusion phases (Al2O3, MgAl2O4 and CaO.Al2O3) at 1773 K was investigated using a sessile drop technique. It was found that for all systems studied θ versus time showed a rapid decrease in wetting in the first 10 s tending to a plateau value at extended times. Further, for basic type ladle slags the plateau value was independent of slag composition and for acid type tundish slags the plateau value decreased with increasing basicity. Through work of adhesion analysis it was shown that ladle type slags appeared more suitable for inclusion removal and that from a wetting perspective calcium aluminate would be easier to remove than spinel and alumina. Choi and Lee’s dynamic wetting model was evaluated and found to not only represent the data well but have physical relevance for the basic, but not the acid, slags investigated.

Study of the radial direction temperature change law of the coil and control strategy in ultra-fast cooling

With the increasing demand for low-cost and high-performance hot-rolled strips, ultra-fast cooling technology is being rapidly developed. The process temperature control precision is an important factor that determines mechanical properties. Even though the process temperature is controlled, the longitudinal mechanical properties contribute to non-uniformity in thick strips. To reduce the longitudinal deviation, the unloaded coil radial direction temperature distribution under five cooling processes with initial temper- atures of 300 ◦ C, 400 ◦ C, 500 ◦ C and 600 ◦ C were systematically investigated. The radial direction temperature deviation change laws affected by the five cooling processes under different initial temperatures were obtained from calculation. With increasing tail special temperature/length, radial temperature deviation decreases gradually. Equations for cal- culating the temperature deviation of the center-external ring and internal-external ring under different initial temperatures were obtained. The study of temperature distribution in a 10-mm-thick strip provided guidance for the tail process planning in strips of other thicknesses. Based on the research, the progressive-U cooling strategy was suggested to de- crease longitudinal property deviation in high-quality steel production. The strategy was successfully applied in a commercial trial production with high accuracy control, laying a solid foundation for high-quality product development.

Recent Advances in the Fluid Dynamics of Ladle Metallurgy

Ladle or secondary metallurgy in steelmaking is an essential process step for the production of high-quality steel. There has been a vast amount of research conducted in this area, particularly regarding refining reactions and inclusion chemistry. More recently, the fluid dynamic aspects of the process have been examined in more detail to provide better control of the process. In this Honorary Lecture two recent aspects related to fluid dynamics are reviewed; gas-liquid plumes and entrainment of slag droplets in metal.

Soft Reduction at a Round Bloom Caster: Implementation and Results

As a consequence of steadily increasing demands on the control of macro segregation in high quality steel products, voestalpine Stahl Donawitz GmbH started investigations on the application of the soft reduction technique for the five strand round bloom caster CC3. Between the years 2006 and 2010, a broad variety of different plant trials with steel grades ranging from 0.8 to 1.05 %C were conducted. The experiments started with the given pinch roll configuration at the pilot strand number one and finally provided a wide understanding of the influence of soft reduction on the solidification structure and on the concentration level in the core region. As a part of this project, a time and cost efficient method for the quantification of the center segregation was established. In addition, numerous segregation values were collected along the entire process route, from bloom to wire. As a consequence of the outstanding results, all five strands were equipped with a soft reduction unit in 2010.

Development of Metallurgical Processing Technology the Titanomagnetite Concentrate of the Tebinbulak Deposit

The approach to solving the problem of processing iron ore raw materials of Tebinbulak titanomagnetite deposit (Uzbekistan) is offered. It can provide high-quality steel products. The two schemes of processing of Tebinbulak ore are shown. The choice between the proposed schemes of the Tebinbulak ore processing: variant of "blast furnace – converter" and variant of "metallization – electric smelting" should be made after thorough analysis based on many factors.

Эффективность десульфурации чугуна при производстве высококачественной стали в условиях ОАО “Уральская Сталь”

The analysis of the sulfur removal in the production of high quality steel in the technological conditions of JSC "Ural Steel" was performed. An increase in the sulfur content of the pig iron at 0.007-0.010% of the tapping from the blast furnace until used in an electric arc furnace was founded. The need for preliminary hot metal desulphurization before pouring in the electric arc furnace was justified. The method of calculating the cost of hot metal desulphurization, and the performance of the electric arc furnaces and "ladle-furnace", depending on the quality of the initial charge on the sulfur content was developed. The results of optimization technology of smelting high quality steel with using hot metal desulphurization at JSC "Ural Steel" were presented. It is established that, with an average sulfur content of the pig iron from the blast furnace 0.019%, the minimum cost of production of steel with a sulfur content of 0.005% (with the share of liquid pig iron in the metal stock to 34%) are provided at the organization ladle hot metal desulphurization to a sulfur content of 0.005%.

Study and Design on Clean Steel Production Platform

The technology for clean steel production in modern steel plant is analyzed, a philosophy with production efficiency, manufacturing cost and product performance in its core. A review on functions is also made which of high-efficiency, low-cost and high-quality steel products manufactured by the new generation iron and steel plant, in combination with the study on design of steelmaking – continuous casting process of Shougang Jingtang iron and steel plant. By applying precise and dynamic design system to optimize and allocate systems and working procedures of hot metal pretreatment, converter smelting, secondary refining, continuous casting process, etc, a platform of high-efficiency, low-cost and high-quality clean steel production is built.

The Fluid Mechanics of Slag-Metal Interactions in Ladle Metallurgy

In Ladle Metallurgy operations following steelmaking, the control of the interactions between slag and metal is crucial for the production of high-quality steel. While the chemical aspects of the refining have been well studied, the fluid dynamic aspects have received less attention. Ladles are often gas-stirred by porous plugs pushing the slag to the periphery of the ladle and opening “eyes” of steel exposed to the atmosphere. The nominal slag-metal contact area is reduced, but there may be entrainment of slag in metal and vice versa which increases the effective interfacial area. Experiments were conducted with water models and the work of others in metallic systems has been included in the study. The eye size has been found to be quite different for thin and thick slag layers, and mathematical models of the controlling factors for the eye size has been determined for these two regimes. The models show that the important factor is the balance between the inertia from the gas-liquid plume and height of the slag, so the governing equations are based on Froude number control. The conditions for closure of the eye have been identified and mathematically modeled. At higher gas flow rate, droplets of slag are entrained into metal which is quantitatively linked to Kelvin-Helmholtz instability. The role that physical properties of the slag play in these phenomena is discussed.

Estimation of World Steel Demand and In-Use Stock for Ships

Recovery of materials from end-of-life products will contribute to the reduction in consumption of natural resources and global warming. For many decades, ships have been a major share of steel use, and used high quality steel products, mainly plates and high tensile strength steel. So, the steels contained in end-of-life ships should be useful for secondary resources. Therefore, it is important to estimate the in-use stock and demand of steel for ships from past to future. In this study, we conducted material flow analysis of steel for ships in global scale to estimate the in-use steel stock and demand in the future for ships. As the result, world in-use steel stock of ships was estimated as 540 million ton in 2009, and predicted to reach 900 million ton in 2035, 1.7 times in 2009. It was expected that future steel demand for ships would increase up to 41 million ton in 2035.

Study on Non-Isothermal Crystallization Kinetic of Tundish Covering Fluxes

Basic tundish covering flux is widely used in continuous casting production of high quality steel because of good heat insulation function and the properties of absorbing inclusions. However, there is a serious problem of incrustation caused by basic tundish covering flux in process of pouring and it could be dramatically influenced by the crystallization behaviors of covering flux. In the paper, the crystallization time and ratio of basic tundish covering fluxes were investigated by high temperature electrical resistance furnace and single hot thermocouple apparatus. Based on the crystallization kinetic knowledge and experimental results, Avrami equation was modified, the non-isothermal crystallization equation that could quantitatively describe the crystallization behaviors of basic tundish covering fluxes was established.

Electromagnetic Stirring Systems

Electromagnetic stirring (EMS) systems have been extensively used in the continuous casting process in steel-making industries to produce high-quality steel products. Although the operational principles of such EMS facilities are well established and extensively applied, demonstrations of actual stirring effects on molten metal are always desired for comparative investigations. To fulfill the requirements for investigating EMS phenomena, a hot-mode experimental apparatus of an EMS system with liquid zinc (Zn) as the test object has been successfully established in the laboratory. The performances of the experimental apparatus are further confirmed by detailed three-dimensional (3-D) finite element analyses (FEA). With such a well-constructed appliance, the relative behaviors at various operational conditions can be thoroughly investigated, and the characteristics of such EMS facilities can be easily realized.

UsING of CALCIUM MAGNESIUM ALUMINATE FLUX WITH HIGH MGO CONTENT TO IMPROVE secondary STEEL LADLE LIFE TIME

One of the most corroded zones in the secondary steel ladle is the contact area between the metallurgical slag and the refractory lining. The slag zone, even with specially designed Magnesia-Carbon and Doloma-Carbon bricks, is in many cases the life time limiting factor for the whole steel ladle. This makes repairs by gunning or intermediate slag zone replacements necessary. During the slag zone replacement the ladle has to be cooled down with further negative effect on the other parts of the ladle due to thermally induced stresses and consequently crack formation. In order to improve the life time of the slag zone, the impact of OPTIMET TM RG (FLUX B) and OPTIMET TM HM (FLUX C), novel synthetic Calcium Magnesium Aluminate Fluxes (CMA) with high MgO-content, has been studied. Thermodynamic simulations with the FactSage © software and laboratory experiments have been conducted. A traditional slag fluxing practice with fluorspar (CaF 2 ) has been compared with Calcium Aluminate (CA), LDSF ® RG (FLUX A), and with these novel synthetic fluxes with different MgO-contents. Calcium Magnesium Aluminate Fluxes (CMA) allow a quick formation of a homogeneous and liquid slag with a high capacity to absorb sulphur and oxide inclusions from the steel bath, very similar to Calcium Aluminate (CA). Calcium Magnesium Aluminate Fluxes (CMA) bring the MgO-content in the slag, right after tapping, close to the saturation concentration and minimise the dissolution of Magnesia-Carbon or Doloma-Carbon bricks in the slag. Life time increase of the slag zone can be expected. Calcium Magnesium Aluminate Fluxes (CMA) help to reduce the specific ladle costs per tonne of steel. The efficiency of high quality steel production can be increased which supports the efforts to reduce the CO 2 -emissions per ton of produced steel.

Effect of Properties of Mold Powder Entrapped into Molten Steel in a Continuous Casting Process

Mold powder plays an important role in the continuous casting process for high quality steel production. Qualitatively, it is well known that mold powder entrapment causes surface defects in steel sheets, and high viscosity of the mold powder prevents the entrapment of the mold powder into the molten steel in ultra-low carbon steel.This paper deals quantitatively with the entrapment of mold powder caused by suction by Karman's vortex in a laboratory experiment. First, in a water model experiment using oil as a substitute for mold powder, the effects of the viscosity of the oil and the interfacial tension between the water and oil were investigated. Following this, hot model experiments were carried out with mold powder and molten steel. The amount of mold powder entrapment was affected by the viscosity of the molten mold powder and the interfacial tension between the molten steel and mold powder. As the result, the following equation for mold powder entrapment was obtained.

「環境調和的な石炭利用」製鉄所における石炭利用

All advanced countries face the global environment issue to reduce drastically CO2 emission in the coming 50 years of this century. Iron making and power generation industries in Japan consume a huge amount of coal because of its reasonable cost and stable supply. Hence they are strongly requested to reduce CO2 emission. Iron making industry has developed a series of technologies to produce high quality steel products for saving the energy consumption over the world at the minimum energy consumption, applying raw materials and energy of low quality. Nevertheless they are asked to develop the technology to reduce further CO2 emission. In the present review, the authors summarize a series of the iron making technology developed recently and currently under development to meet future regulation of CO2 emission. The blast furnace, coke making oven and sintering of iron ore are major steps of iron making. Coal and coal derived products are heavily applied and higher efficiency of their use has been attempted. Industrial complex reconstruction, as well as technological development are continuously intended in the coming years.