Continuous Billet Research Articles

Estimating Non-Linear Heat Flux in Continuous Billet Casting Process With Limited Sensors

In a continuous billet caster, the heat transfer from the pool of molten steel to the cooling water via the copper mold depends non-linearly upon several casting parameters. A reliable and accurate methodology based on the principle of inverse heat transfer technique has been proposed in this work to obtain the nonlinear heat flux of a continuous billet casting mold. Differential evolution optimization technique has been used, in conjunction with the 2-D and 3-D steady state conduction heat transfer equations to develop the complete algorithm. It has been observed that both the 2-D and 3-D models are able to accurately predict the heat flux for different numbers and locations of temperature sensors. While the 2-D model estimates the 1-D heat flux profile varying along casting direction within a very short time period, the 3-D model offers the advantage of estimating a more accurate 2-D heat flux profile varying along both the mold length and width. The 2-D model has also been used to estimate the heat flux for an industrial continuous casting mold using measured plant data. It is observed that the present methodology accurately estimates the boundary heat flux in the continuous billet caster mold.

Вплив швидкості охолодження та перегріву вище лінії ліквідусу на формування структурних складових

In the paper, the comparative analysis of the process of forming a cast structure of carbon steel after termination of its crystallization in continuous cast steel billet with diameter of 450 mm and overheating of steel to 50° C and 150° C above the liquidus line, and further pouring into wedge-shaped molds, is performed. The microstructure of the skin zone after continuous casting of steel with maximum cooling rate of 106 °С/min consists of dendrites, which have branches of the first and second order, indicating their formation from the melt. When etching the surface of the specimens with solution of nitric acid, the microstructure of the skin zone was represented by ferrite, perlite with separate areas of martensite. The formation of ferrite, perlite and bainite areas was observed at a distance of 0.5 ingot radius and in the central part of the samples, and separate areas of bainite and perlite were observed in the central part of the ingot. Upon further cooling of steels below the temperature of Ar3, the formation of excess ferrite along the boundaries of austenitic grains occurs. Overheating of steels to 50° C and 150° C above the liquidus line gives rise to the formation of a more homogeneous structure. Non-metallic inclusions formed in steel do not exceed 1 point according to DSTU 4967:2015and are not the centres of crystallization – they are observed in perlite grains. There is the formation of separate inclusions of phases located in the perlite grain, which contributes to the finely dispersed hardening of steel. Increasing the overheating temperature leads to the formation of more finely divided inclusions and to the formation of a more homogeneous structure. After overheating to 50° C in the middle part of the wedge (cooling rate of 102-103 ° C/min) no ferrite formation is observed. At all overheating temperatures, perlite has a fine differentiation, but increasing in the overheating temperature above the liquidus line enhances the dispersion of both individual inclusions and perlite. Keywords: carbon steel, continuous cast steel billet, hardening, cooling rate, overheating of steels above the liquidus line.

The Effect of Temperature, Cooling Rate and Casting Speed on Quality of Continuous Cast Steel Billets

In continuous casting, the cooling rate, casting speed, and molten metal temperature significantly affect the quality of cast steel billets. Appropriate casting parameters can minimize quality problems such as surface, subsurface and interior crack, rhomboidity, oscillation mark depth, and central porosity. This research determines the relationship between defects and three significant factors temperature, cooling rate, and casting speed. The work has been performed on the two-strand continuous casting machine to investigate the billet (BS-4449 steel grade) cross-section of 150 x 150 cm2. The defects analysis through macro examination at different tundish temperatures (1510 °C to 1560 °C), varying cooling rates, and casting speeds (0.9 to 1.6 m/min). The present study provides detailed insight into the three parameters mentioned earlier, which directly affect the quality of cast steel billets.

Особливості формування неоднорідних структур у вуглецевих сталях

Obtaining a homogeneous structure and uniform-phase distribution is critical to a high set of mechanical and operational properties of rolled metal. However, in practice it is not always possible to create metal products with the specified characteristics. In order to determine the morphological features of the structure of rolled carbon steel, a comparative study of carbon steel samples with a carbon content of 0.49 % C and 0.2 % C selected from hot-rolled billets was carried out. The billets of each group were produced under the conditions of the same enterprise, with close temperature-time modes of deformation processing. The main difference was in manufacturing processes of the output continuous cast steel billets. This research shows that with identical normalized chemical composition of steel and the same thermomechanical treatment, the formation of the morphological structure features of hot-rolled steel occurs in a different way. Therefore, we can assume that the liquation, the diffusive mobility of elements is particularly influenced by the content of impurity elements and gases in steel, which leads to a different type of structures in the finished rolled metal. At the same time, these differences are observed in carbon steels with different carbon content. A sample of non-vacuumed OC grade axle steel (0.49 % C) from converter steelmaking has a more homogeneous structure without local areas of pearlite or ferrite accumulation. It was shown that the formation of ferrite rim in the microsegregation areas occurs not only in manganous sulfides, but also arises on the background of the smallest oxide inclusions. There is significant structural heterogeneity in the samples of electric steel, despite the lower sulfur content and gassiness of steel; at the same time, a dense perlite layer is formed around the sulfides. There is also a difference in steel grade 20 (0.2 % C) of different manufacturing processes. The structure is more homogeneous in qualitatively deoxidized vacuum degassed steel; no local areas with different dimensional characteristics were detected. The size of the structural elements is much larger and the structure has mostly large sections of the Widmanstatten ferrite. Since a large number of non-metallic inclusions and gassiness of steel is not a positive factor for providing a high set of properties of metal products, the modes of thermomechanical treatment used today require adjustments depending on the characteristics of steel melting. Keywords: microstructural heterogeneity, ferritic-pearlitic banding, mechanical properties, manganous sulfides.

Causes of Structural Heterogeneity in High-Strength OCTG Tubes and Minimizing Their Impact on Sulfide Stress Corrosion Cracking Resistance

High-strength oil country tubular goods (OCTG) like C110, according to standard API 5CT (yield strength at least 758 MPa), are subject to requirements in terms of mechanical and corrosion properties. In this work, we studied the microstructure of seamless casing tubes made of class C110 high-strength steel with a 194.5 mm diameter and 19.7 mm wall thickness, and its influence on sulfide stress corrosion cracking (SSC). Casing tubes were obtained from continuous billets by screw piercing with preliminary quenching and tempering. It was shown that cracking during the tests always begins from the inner surface of the tube. Rough segregation bands were found on the inner tube surface, which occupies about a third of the thickness of the wall. To increase the resistance of 0.3C-Cr-Mn-Mo + 0.15(V + Nb + Ti) steel to SSC, primary recommendations for adjusting the chemical composition, production technology and heat treatment were developed.

Research of the Process of Production of Steel Square Continuous Billets for Rolling Balls of Large Diameter

The paper investigates the technology of production of steel billets continuously cast billets for rolling balls of large diameter. In Kazakhstan, in connection with the development of new copper deposits such as Aktogay and Bozshakol, the need for large diameter steel grinding balls for primary ore processing has increased. The main problem in the operation of large diameter grinding balls is the tendency of the grinding media to break during operation. The authors of the work investigated the process of production of steel billets continuously cast billets with a cross section of 150 × 150 mm for rolling balls of large diameter (d 125 mm) in the PB LLP "KSP Steel", which showed that the breaking of grinding balls is initiated mainly by the presence of internal discontinuities (gas axial looseness) in continuously cast billets. Studies have shown that the technological scheme for the production of grinding balls with a diameter of 125 mm from continuously cast billets with a section of 150 × 150 mm, including steel smelting in an arc furnace with steel finishing on a ladle-furnace unit, deoxidation with aluminum and degassing in a ladle vacuum apparatus, casting steel in a closed jet on a continuous casting and further production of rolled stock on a rough rolling mill ensures the absence of internal discontinuities (gas bubbles, axial looseness) in the workpieces and ensures the production of high quality balls.

Element-Free Galerkin Method Modeling of Thermo-Elastic-Plastic Behavior for Continuous Casting Round Billet

When solving the coupled thermal-mechanical problem of the metal solidification, the mesh-based numerical methods suffer from the inconsistency of mesh lines and curved boundaries. Furthermore, the mesh should be continually reconstructed to comply with the interface when dealing with the moving boundary such as phase transition, which brings great difficulties to the numerical calculation. Based on the plane stress assumption, the present work establishes a two-dimensional thermo-elastic-plastic calculation model for continuous casting round billets using the Element-Free Galerkin method, and the correction scheme of elastoplastic transition region has been explored. The results show that the correction scheme has a slight effect on magnitude of the equivalent stress and no impact on the subsequent plastic deformation zone. The elastoplastic transition region of shell surface appears in the range of 100 to 200 mm below the meniscus, and the averaged plastic stress is about 2.27 times of the elastic stress at the mold outlet. Near the interface region of liquid–solid phase exhibits an elastic deformation behavior, while far from the interface region appears plastic deformation in which the elastic stress remains invariable. The Element-Free Galerkin method is discretized by a series of arbitrary nodes, which exhibits high accuracy and great flexibility in dealing with moving interface problems. It provides a powerful approach to calculate and analyze the heat transfer/mechanical behavior with complex geometric boundaries such as round billet, chamfered billet, and beam blank.

Increasing Casting Speed in High Carbon and Micro Alloy DIN EN ISO 16120-2: 2011-C66D Steels

Different parameters can be used together in the continuous casting process known as an important steel production stage in the world. It is important to use metallurgical appropriate parameters to meet the product properties. Many innovations have been made in the continuous casting process from past to present. It is known that studies are carried out on many effective topics such as steel analysis, refractory materials, continuous casting parameters, in order to make the proper solidification that will meet the needs with its continuous casting capabilities. When continuous casting parameters are examined; the casting speed parameter was found to be effective in terms of quality needs in macro samples. Therefore, in this study, the effect of the increase of casting speed parameters on the quality of macro samples was investigated. As a method; in high carbon, micro-alloyed DIN EN ISO 16120-2: 2011-C66D quality steels, in different castings, this parameter was changed and macro samples were taken and evaluated in terms of quality needs. When macro sample quality results are compared; the effect of casting speed was observed. In this study; the effect of the increase in casting speed in continuous billet casting facility on optimum metallographic and physical quality has been investigated and the results have been interpreted.

Effect of fluorine on surface tension of CaO-SiO2-Al2O3-Na2O-CaF2 mold flux

The surface tension of mold flux is an important parameter for controlling the quality of continuous billet, affected deeply by the compositions of mold flux and temperature, andclosed related with the structure of mold flux. In the present study, the effect of CaF2and temperature on the surface tension of CaO-SiO2-Al2O3-Na2O-CaF2 mold flux melts is investigated by the pulling cylinder method; furthermore, the structure of melts is determined by FT-IR spectroscopy to analyze the change mechanism of surface tension. The results indicate that the variation of surface tension is in accord with that of structure of melts. The surface tension of melt decreases with the increase of CaF2 mass fraction, and this tendency becomes more apparent at higher temperature. The FT-IR spectra show thatboth the amount of Obandthe degree of structural polymerization of melts decrease as the CaF2 content increases. This is because the Si-Ob bonds in the [SiO4]-tetrahedrons are broken by F− and transformed into Si-F bonds, and the silicon-oxygen anions with more complex structure were depolymerized into silicon-oxygen anions containing fluorine with simpler structure, resulting in an increase of Si-F saturated bonds on the melt surface, and thusreducing the surface tension of melts.

Analysis of the influence of deformation working of a continuous billet on macro- and microstructure of structural steel (review)

The purpose of the study is to analyze the results of existing studies of the effect of hot deformation on quality indicators and methods for assessing the deformation processing of the macro- and microstructure of metal products made of structural steels. Analysis of existing publications on the subject − matters of research of influence of deformation modes in the elaboration of the structure of the finished product takes a lot of teams of scientists, such as A.P. Chekmarev, I.Yu. Tarnowskyi, N.Yu. Dzugutov, V.A. Tyurin and their followers. Now, a large number of works have been published, which provide the results of studies of the effect of the degree of deformation on the structure and mechanical properties of rolled products from a continuously cast billet. Results. Based on the results of the analysis, it was found that modern technologies for the production of continuously cast billets and hot rolling make it possible to ensure compliance with the surface quality, macro- and microstructure, mechanical properties of rolled products at a certain coefficient of total stretch. The minimum coefficient of drawing required to minimize the macrostructure defects and mechanical properties of stabilization, increases with increasing carbon content and alloying elements in the steel. Scientific novelty. This definition of deformation processing from the standpoint of materials science, as fragmentation of the dendritic structure of cast metal in the process of deformation of the initial ingot. The design of the steel structure during hot deformation is influenced by the size of the initial continuously cast billet due to its macrostructure and the stress-strain state pattern: the larger the BLZ section, the more uneven the cast structure and unfavorable stress-strain state in the central zone of the billet. Practical significance. The developed methodological foundations for a quantitative assessment of the direct effect of deformation effect on the microstructure of structural steels using the structural development coefficient K. This allows for a quantitative assessment of the intensity and localization of deformation in the volume of the workpiece and makes it possible to analyze the technological processes of metal forming with a deliberately high degree of non-uniformity of deformation.

A fast method based on GPU for solidification structure simulation of continuous casting billets

The present paper develops a fast method to simulate the solidification structure of continuous billets with Cellular Automaton (CA) model. Traditional solution of the CA model on single CPU takes a long time for the massive datasets and complicated calculations, making it unrealistic to optimize the parameters through numerical simulation. In this paper, a parallel method based on Graphics Processing Units (GPU) was proposed to accelerate the calculation, which developed new algorithms for the solute redistribution and neighbor capture to avoid data race in parallel computing. This new method was applied to simulate the solidification structure of Fe-0.64C alloy, and the simulating results were in good agreement with the experiment results with the same parameters. The absolute computational time for the fast method implemented on Tesla P100 GPU is 277 s, while the traditional method implemented on Intel(R) Xeon(R) CPU E5−2680 v4 @ 2.40 GHz with single core is 24.57 h. The speedup, ratio between the absolute computational time of GPU-CA and CPU-CA, varies from 300 to 400 with the increase of the grids.

Hot-Slab Charging for Energy Conservation in Continuous Furnaces

We considered the thermal operating balance of a continuous furnace being charged with 250 mm-thick cold steel slabs, and perform experimental measurements of the heat loss to the environment. The required heating time and peak productivity of a hot-charged furnace were determined under the assumption that the slabs were fed into the furnace at 700–1250°С. The calculations revealed that the amount of time required to heat the slabs is much shorter, productivity is higher, the amount of heat required per metric ton of metal is smaller, the amount of heat lost to the environment is lower, and the fuel (natural gas) consumption of the furnace per metric ton of metal is much lower. We also obtained a theoretical curve for fuel consumption as a function of charging temperature; according to this curve, as the charge temperature increases from 700 to 1000°C, the specific natural-gas consumption per metric ton of metal decreases from 27.7 m3 /metric ton to 10.3 m3 /metric ton, compared with 62 m3 /metric ton for cold feedstock. We find that the energy savings in heating furnaces is maximized by feeding the slabs in immediately after they come out of the continuous billet casting machine.

Model Studies and Modernization of a Manipulator for Tapping Spout Replacement in Continuous Steel Casting

We study the operating conditions for the specialized tapping spout used to protect molten steel against secondary oxidation between the steel pouring ladle and the tundish in a continuous billet casting machine. The following are found to be the major factors affecting premature failure of the tapping spout: Localized damage to the tapping spout walls due to installation-related misalignment between the spout and the refractory-lined slide-gate valve, and gradual encrustation of the spout during the pour process, with oxygen lancing subsequently being required to remove the encrustation. The accuracy of spout alignment with the ladle slide gate can be improved by modifying the functional configuration of the manipulator to support self-alignment of the spout to its proper location. The wear on the spout can be reduced by using a pneumatic vibrator to induce vibration, and this has been confirmed by laboratory studies using a model experiment. The proposed modernization of the manipulator will enhance tapping spout operating efficiency by reducing premature tapping spout failures.

Acquiring High-Quality Oil Casing Steel 26CrMoVTiB under Optimal Continuous Casting Process Conditions

While the solidification macrostructure of continuous cast billets is an important factor influencing the final performance and rolling yield of oil casing steel, the continuous casting process parameters have a direct influence on the solidification structure. This study simulated the solidification process of the continuous casting round billets of oil casing steel using a cellular automaton–finite element (CAFE) model. According to the simulation results, at a superheat degree of 20–35 K, a casting speed of 1.9–2.1 m/min, and a secondary cooling specific water flow of 0.34–0.45 L/Kg, the solidification structure had a relatively high equiaxed crystal ratio and small average grain radius. Guided by the simulation results, this paper establishes optimal process schemes for producing 26CrMoVTiB steel round billets, comparatively analyzes the equiaxed crystal ratio and central shrinkage of round billets produced according to these schemes, and defines the optimal continuous casting process conditions, which are: superheat degree = 25 K, casting speed = 2.1 m/min, and specific water flow = 0.35 L/Kg. When adopting these process parameters, the 26CrMoVTiB steel round billets demonstrate a tiny central shrinkage and an equiaxed crystal ratio of 45.2%.

Совершенствование наплавки и механообработки роликов МНЛЗ

Совершенствование наплавки и механообработки роликов МНЛЗ

Improvement of continuous billet casting machines

Abstract The paper describes disadvantages of known designs of machines and their components, represents new more advanced designs of continuous billet casting machines improving their quality, operational reliability and ease of operation.

MHD-equipment and technologies of semi-continuous billet casting of high-strength Al-alloys

In this study, there are presented design and conceptual approaches developments for 2 (two) kinds of the original complex technological foundry equipment for the melting, holding and managed electromagnetic magneto-hydrodynamic high-strength aluminum alloys pouring at continuous billet casting processes.First kind performed as MHD-complex device created on base of the magneto-dynamic installation (MDI MDN-6A-0.63-WMD-M), that has applied as mixer-batcher with 630 kg capacity by Al-alloys with electromagnetic pump (up to 0.35 bar pressure). An experimental approbation for workability of the developed technologies for MHD-semi continuous billet casting, by means open stream melt feeding into 7 inch crystallizer and by progressive hot-top closed process, at the producing 1.0 meter of 7’ billet from Al-Zn-Mg-Cu wrought alloy has been executed. As second kind, there are developed conceptual design of 500 kg capacity by Al-Alloy pilot plant of the foundry equipment for the melting, holding and managed electromagnetic continuous billet casting, comprised upgraded tilting reverberator melting furnace combined with multifunctional horizontal magneto-hydrodynamic units (MHDU), as a W-shaped induction channel with 2 inductors (2 × 20kW) and external C-type electromagnet (0.01∼0.3T). MHDU provide homogenization melt temperature (650∼850°C) and it chemical compositions (at circulation melt intermixing 0.5∼3.0kg/s) and at the switching electromagnet of electromagnetic melt pouring with managed flow rate 0.05kg/s ∼ 15kg/s to tundish of the 3∼10 inches billet continuous casting machine (CCM).

Pulse electromagnetic force microstructural control at continuous billet casting 7xxx Al-alloys

In this study, the original equipment and methods for the macro/microstructure managed formation in the crystallizers of continuous casting processes by the applying of the amplitude modulated (AM) pulsing magnetic fields (PMF) it the electromagnetic stirrer (EMS) has been developed and tested.Method has provide the complex electrodynamic, hydrodynamic and acoustic pulse-force processing of unsolidified casting product portion for providing equalizing of solidification front in the billet mushy zone. Resulted non-dendritic type of microstructure has been provide by the means applying: Pulse magnetic field with periodically changing in time amplitude (AM-PMF); Pulse amplitude-modulated rotating melt stirring (AM-PRMF); Pulse amplitude-modulated 3D-helicoidally rotating melt stirring.Study efficiency applying of unidirectional axial pulse magnetic field (AM-PMF) with pulse frequency in range 5~15Hz, carried frequency in range 22∼55Hz, at intensity of MF 0.05∼0.1T, for semi-continuous 7xxx alloys (analogue 7075 alloy) 7 ‘billet casting on micro- and macrostructure billet formation has been show reaching the stabile effect for non-dendrite state microstructure formation in all billet cross-section. As well-achieved uniform and homogeneity microstructure state with average grain size not more 100μm, and for middle and central billet part in range 60∼80μm, in 3∼5 times lowest instead grain sizes 200∼650μm at DC casting without EMS, or instead 150μm grain sizes as for conventional rotating EMS. As well, fully solved problems of axial and structural segregation, hot-crack ability or micro-cracks on grains edges and micro-porosity occurring.

Electron microscopy and x-ray spectral microanalysis of types and chemical propeties inclusions of the railway axis from a continuous billet

Purpose. Analysis of status and chemical composition of non-metallic inclusions of raw railway truck axle shafts steel using electron microscopy and X-ray spectral microanalysis for the improvement of the throughout technology of the axles production. Methodology. Study of phase composition and type of non-metallic inclusions in axles shaft steel was carried out with modern equipment and method of X-ray spectral microanalysis for quantitative and qualitative data. Findings. The analysis of the elements on chemical composition on EA1N steel and of non-metallic inclusions on physical and mechanical properties of railway axles made by rolling of continuous cast billt of 470 mm diameter. The types and composition of non-metallic inclusions were studied with electron microscopy and X-ray spectral microanalysis. Results can be applied for improvement of steel refining and alloying technology for railway wheel axles production. Originality. There were discovered the original data about the types and chemical compositions of nonmetallic heterophasic inclusions in railway axis metal using the electronic microscopy and X-ray microanalysis. The obtained research results about formations of multiphase inclusions were proved using the phase equilibrium charts consiolering oxide, oxide-sulphide mineral phases. Practical value. The results of electron microscopy and X-ray spectral microanalysis are important to understand and improve the throughput technology of refining and alloying of EA1N steel for railway axle shafts. Keywords: railway axle, railway truck, axle shaft, steel chemical composition, continuous casting billet, mechanical properties, non-metallic inclusions

Improvement of the metal casting process and refractory equipment design in the intermediate ladle ‒ open jet ‒ the continuous billet caster mold's installation

The steel flow and refractory arrangement of the intermediate ladle (IL) ‒ open jet (OJ) ‒ continuous casting machine (CCM) mold's installation are regarded in the article. The specifics of the metal flow controlling are mentioned. The structural features of the continuous billet caster which maintain the effective metal flowing through the IL ‒ OJ ‒ CCM mold installation are presented. The improving of the installation design allows the expedient metal flows and provides the billets' quality upgrading.