Continuous Casting Technology Research Articles

Development of continuous slab casting technology with dimensions of (300–400) mm × (2000–2500) mm OF high-alloy martensitic steel

Development of continuous slab casting technology with dimensions of (300–400) mm × (2000–2500) mm OF high-alloy martensitic steel

Enhancing the thermal shock and corrosion resistance of low‐carbon Al2O3–C refractories: The role of h‐BN composite powder

AbstractDeveloping low‐carbon and high‐performance Al2O3–C refractories is vital for extending the service life of slide gate plate refractories and reducing carbon emissions. In this study, hexagonal boron nitride (h‐BN) composite powder was prepared using the magnesiothermic reduction combustion synthesis route and introduced into low‐carbon Al2O3–C refractories. The phases composition, microstructure, mechanical properties, thermal shock, and slag corrosion resistance of low‐carbon Al2O3–C refractories were investigated. The results show that the thermal shock and slag corrosion resistance of low‐carbon Al2O3–C refractories enhanced by adding h‐BN composite powder. Due to the introduced h‐BN, consequent in situ formed spinel and AlN whiskers, the crack propagation in the refractories was deflected, branched forming more fine cracks, then the thermal shock resistance was enhanced. In addition to the chemical inertness of h‐BN, in situ formed spinel and AlN whiskers, the consequent decrease in pore size plays an important role in enhancing the slag corrosion resistance of the refractories. The h‐BN composite powder synthesized via the combustion synthesis in this study demonstrated potential application in high‐performance Al2O3–C slide gate plates used in continuous casting technology.

Effect of Electromagnetic Power on the Microstructure and Properties of 2219 Aluminum Alloy in Electromagnetic Continuous Casting Technology

Electromagnetic continuous casting technology serves as a significant means for enhancing the casting performance of 2219 aluminum alloy. Investigating the influence of electromagnetic field variations on the solidification process is crucial for studying the microstructure and mechanical properties of electromagnetic cast billets. Through experimental research, variations in the microstructure and mechanical properties were examined for ordinary direct chill casting, as well as three different electromagnetic power casting ingots. The COMSOL software (COMSOL Multiphysics 6.0) was utilized to simulate the temperature and flow field, enabling an explanation of the resulting performance changes. The results showed the effect on electromagnetic continuous casting technology by the electromagnetic field generated by the Lorentz force and melt stirring, improving the melt flow and temperature distribution so that the melt center and the edge of the melt forcible convection were enhanced, thus realizing the tissue refinement, mechanical properties, and Cu element segregation of the improvement. With an increase in electromagnetic power, the distribution of the temperature field was more homogeneous, the segregation phenomenon was more alleviated, and the improvement in mechanical properties was more significant. The optimal microstructure and mechanical properties were achieved at a power of 20.0 kW, with a 74.7% improvement in grain refinement in the center and a tensile strength increase of 30.8%. Additionally, significant improvements were observed in segregation phenomena.

Effect of large deformation on microstructure and properties of copper alloy wire

Cu–Ag alloy wire with different deformations and Ag contents of 1%, 2%, and 4% are prepared using vacuum continuous casting technology combined with cold drawing and intermediate annealing processes. The evolution of microstructure, electrical properties, and mechanical properties of the Cu–Ag alloy wire is investigated, and a relationship model between wire diameter, Ag content, and alloy wire properties is established. The results showed that the directionally solidified billets exhibited good elongation and are suitable for drawing fine wire. As the Ag content increased, the twinning content inside the Cu–Ag alloy wire also increased significantly. It is found through Strain++ characterization that there is non-uniform deformation within the wire, and the tensile and compressive strains that exist interactively tend to aggregate within the twins. The properties of the Cu–Ag alloy wire with different diameters varied significantly at different stages of deformation, showing a pronounced size effect below 1 mm. With decreasing wire diameter or increasing Ag content, the DC resistance, resistivity, and tensile strength of the Cu–Ag alloy wire gradually increased, while the conductivity decreased. The effect of Ag content on elongation is not significant. Statistical analysis revealed that the established performance model had high predictive accuracy and could provide references for the optimization of production processes for Cu–Ag alloy wire.

Corrosion Behavior of Nickel–Titanium Continuous-Casted Alloys

Variations in the corrosion behavior of biomedical NiTi alloys in Cl− containing and acidic environments present a problem with their biological implantation. The objective of this research was to evaluate the synergy of the microstructure, the corrosion behavior, and the biocompatibility of novel continuous-cast NiTi alloys and to compare them with commercial NiTi alloys. The two alloys have a practically identical nominal chemical composition, but they differ in production technology. The continuous casting technology involved vacuum induction melting of the basic components and vertical continuous casting, while the commercial NiTi alloy was produced through a process of casting, hot rolling, and forming into square shapes. The microstructure was revealed to determine the surface area and size of grains. The corrosion of a commercial nickel–titanium alloy and one prepared by a novel continuous casting method in acidic and chloride-containing solutions was studied via analytical and electrochemical tests. Localized corrosion characteristics related to oxide properties, when exposed to 9 g L−1 NaCl solution, were examined with focused ion beam analysis and subsequent microchemical analysis of the formed corrosive products. Corrosion potential over time and the oxide film resistance were analyzed using linear polarization measurements. To obtain a preliminary estimate of biocompatibility, human fibroblast cells were used in indirect contact, i.e., alloy conditioning medium. The continuous casting method resulted in a reduction in the average grain size in comparison to the commercial sample and better corrosion stability of the sample in an acidic environment. Also, in a solution of 9 g L−1 NaCl the commercial sample showed high values for the corrosion current density (jcorr = 6 μA cm−2), which indicated low corrosion resistance, while the continuous casting sample possessed much better corrosion stability and lower values for the corrosion current density (jcorr = 0.2 μA cm−2). In line with that, elemental analysis of the corroded surfaces showed higher Cl− ion deposition over the surface layer of the commercial sample, suggesting local oxide breakdown. Moreover, NiTicc reached a value three times higher for polarization resistance (Rp = 270 kΩ cm2) over time in comparison to the commercial sample (Rp~100 kΩ cm2). Biocompatibility evaluation showed that human fibroblast cells exhibited altered metabolic activity. An MTT assay showed that cells’ mitochondrial activity dropped below that of control cells in the presence of both materials’ supernatants.

Mikhail Ziegler, the First Professor of Metallurgy at Warsaw Polytechnic, and His Contribution for Developing our Knowledge about Steels

The article presents results of research on the origin and development of scientific schools in the field of metallurgy in Eastern Europe at the turn of the 19th–20th centuries, associated with the scientific and pedagogical activities of the famous scientist Professor Mikhail Karlovich Ziegler in the higher technical educational institutions of Warsaw (Warsaw Polytechnic Institute of Emperor Nicholas II), Kharkiv (Kharkov Technological Institute of Emperor Alexander III), St. Petersburg (Petrograd Polytechnic Institute) and Moscow (Moscow Mining Academy). The main facts of the biography of this scientist and educator are given. The stages of formation of M.K. Ziegler as a personality and a scientist against the backdrop of occurring historical processes are shown. The Soviet period of his activity was considered separately. The scientific achievements of Professor Ziegler in the field of steel metallurgy, in particular, in determining the strength of steels depending on the conditions of their crystallization, studying the diffusion of impurities in steels, which became the foundation for the development of continuous casting technology, i.e.one of the most important world inventions of the 20th century, are systematized and analyzed. His organizational and educating contribution for the training of scientific and engineering personnel for the metallurgical industry is also estimated. The article includes interesting forgotten and little-known facts from the history of metallurgical science and the training of the higher engineering and technical personnel in educational institutions located on the territory of modern Ukraine and Poland.

Identification of the nature of defects arising in the production of continuously cast pipe billets for the oil and gas industry

The paper presents the results of studies of defects that occur in the production of continuously cast pipe blanks for the oil and gas industry. It is shown that the use of the technology of continuous casting of pipe billets in comparison with the traditional methods of pouring liquid steel into a mold has a number of advantages, among which is the high productivity of the technological process. However, it was noted that in many cases, an abnormally high degree of contamination with non-metallic inclusions is observed in the structure of the steel of continuously cast pipe billets. It was revealed that the largest inclusions are oxides of silicon and manganese. On the surface of the pipes, there are defects in the form of oxide spots, near which there are large non-metallic inclusions. On the surface of the oxide spot, the presence of iron oxides in the form of scale is found, which is a consequence of the secondary oxidation of the metal by air oxygen. A mechanism for the development of oxide spots and decarburized strips in pipe billets has been determined, which consists in the formation of defects in the form of scratches and cracks on the surface before rolling. These defects during heating for rolling lead to the oxidation of the metal and the formation of scale on the surface of the pipe blanks. The results of experimental studies on the development of recommendations for improving the quality of the initial metal of seamless pipes for the oil and gas industry are presented. The study of the microstructure of steel and the assessment of its contamination with non-metallic inclusions were carried out on optical and electron microscopes, and the mechanical properties of pipe blanks were studied by standard methods

Development of technological solutions to improve the quality of railway rails by improving the technology of smelting, out-of-furnace processing and continuous casting of rail electric steel.

Based on a complex of metallographic and X-ray phase studies for the conditions of EVRAZ ZSMK, which is a leading domestic manufacturer of railway rails, the nature of characteristic defects of rails of metallurgical origin has been determined. These defects, which are the cause of rejection of rails during ultrasonic quality control in the flow of rail-block mill, are stratifications, in the localities of which accumulations of silicate, alumina and sulfide non-metallic inclusions are concentrated; at the same time, these defects in the vast majority of cases are located in the neck of the rail profiles. Analysis of contamination with non-metallic inclusions of suitable rails of the current production of EVRAZ ZSMK showed that, unlike the locations of defects in rejected rails, alumina non-metallic inclusions have an extremely low concentration, while manganese sulfides and silicate inclusions have the highest relative concentration. Based on the results obtained, technological measures were developed, pilot-industrial and implemented to improve the production technology of rail steel in the conditions of the electric steelmaking workshop of EVRAZ ZSMK. In order to reduce the concentration of oxide nonmetallic inclusions in rail steel, a new technology of ladle treatment of steel using a low-ash carburizer and calcium carbide for slag deoxidation has been developed. To reduce sulfide inclusions contamination, measures have been implemented to ensure the sulfur content in the finished steel at a level of no more than 0.008%. The optimization of the modes of electromagnetic mixing in the mold and the temperature regimes of continuous casting of steel was carried out, which also had an effect on reducing the concentration of non-metallic inclusions in continuously cast billets of rail steel and finished rails. The introduction of a set of these technological solutions and measures allowed to reduce the rejection of rails for internal defects from 7% to less than 2%

Structural Anisotropy Parameters’ Effect on the Low-Temperature Impact Strength of Alloy Steels in Rolled Products

The present work is devoted to the study of the influence of the parameters of the structural anisotropy of rolled products on the low-temperature impact strength of alloyed steels. A quantitative metallographic analysis of the microstructure of rolled steel samples obtained after testing for low-temperature toughness was carried out. It was established that the main reason for the decrease in the low-temperature impact strength of rolled steel samples is a highly developed segregation band enriched with carbon films formed at the stage of steelmaking conversion in violation of the technology of continuous casting of steel. The microstructural analysis of rolled stock samples was used in the work, and studies of the fracture surface of rolled stock samples were carried out with a scanning electron microscope using X-ray microanalysis methods. The studies carried out showed that the metallurgical quality of sheets of one heat, as well as individual samples within one sheet, varied over a wide range, from satisfactory to unacceptably low. It was established that the main reason for the decreasing low-temperature impact strength of rolled products was a highly developed segregation band enriched with carbon films, formed at the stage of steelmaking in case of violation of the continuous casting of steel technology. The multivariate statistical analysis carried out showed that only the size of the segregation band has an effect on the low-temperature impact strength of 10 mm thick rolled coil samples.

Modern approaches ensuring rational conditions for continuously cast billet formation in a billet CCM mold.

The development of technology and technology of continuous steel casting actualizes the improvement of the control system of casting processes and diagnostics of the formation of continuously cast billets. The conditions determining the stability of continuous cast billet forming process in billet CCM mold are considered: the correspondence of liquid steel mass entering the mold and the outgoing billet mass; ensuring the specified intensity and uniformity of billet cooling in the mold sleeve; ensuring a rational level of friction in the crystallizer. It is shown that, on the one hand, heat transfer in the mold is largely determined by the correspondence of the billet shrinkage and the internal profile of the mold, but, on the other hand, it is noted that it is impossible to obtain a universal profile that creates optimal conditions for the formation of billets from all grades of steel with arbitrary temperature-speed parameters. Therefore, the concept of a universal crystallizer assumes that rational conditions of heat removal are achieved due to additional influences. The basics of diagnosing of heat exchange processes in the crystallizer are presented, based on the computational processing of the current ACS signals about the cooling water temperature drop in the crystallizer and its flow rate. It is noted that this system, unfortunately, does not guarantee the detection of local unevenness of the heat removal in the crystallizer and needs to be improved by providing the possibility of assessing the billet faces cooling uniformity. Modern approaches to optimize internal profile of crystallizer sleeves, choice of materials for coating inner surface of sleeves, choice of parameters of mold swinging system and diagnostics of parameters of force interaction between crust of forming billet and mold sleeve are briefly considered on issue of friction rational level establishing. The creation of a “universal” crystallizer with an increased number of control systems and the creation of a system for optimization of casting processes for specific conditions are identified as possible directions for the development of approaches to ensure rational conditions for the formation of continuous cast billets in the crystallizer of a billet caster.

Improvement of functional and technological solutions for modernization of steel heating in the tundish of continuous casting machine

The using of the system of plasma heating of metal directly in the tundish is quite promising in terms of improving the technology of continuous casting of steel. At the same time, the efficiency of this technology is significantly influenced by the design of the tundish, the location of the plasmatron, the direction of movement of the circulation flows and their speed, the presence of forced mixing of the liquid metal bath, etc. In terms of design, the main technical solutions proposed for plasma heating of steel in a ladle are based on the creation of two-chamber tundish. Moreover, steel is heated in a special receiving chamber. Such heating devices are compact enough to be built into tundish without any significant modifications. Moreover, such heating devices practically do not reduce the useful volume of the tundish. The widespread use of the technology of plasma heating of metal in the tundish of the continuous casting machine (CCM) at a few metallurgical plants in the world is due to the need to increase the stability of the parameters of the casting process and improve the quality of the workpiece while simultaneously reducing specific energy costs. At the same time, additional prerequisites are created for the transformation of the tundish into a multifunctional unit for adjusting the steel temperature and the possibility of its refining. The using of plasma heating in the tundish is especially relevant in the conditions of mini-mills operating technological units of small capacity, for which the implementation of traditional highly efficient solutions for out-of-furnace processing, as well as processing on tundish-furnace units, is not always possible due to the complexity of organizing the heating process, large heat losses and high specific costs of refractories. In addition, such tundish can be quite effective when pouring high-quality grades of steel into billets of small cross-sections, which are produced, as a rule, in relatively small mixer-batches, which makes it difficult to prove them in small steel pouring ladles.

Effect and Mechanism of Solidified Microstructure on Deformation Behavior, Mechanical Properties, and Residual Stress of Cu-Ni-Si Alloy.

Cu-Ni-Si alloy is the key raw material for the lead frame of large integrated circuits. The disordered grain orientation of alloy billet, high hardening rate, residual stress, and poor surface quality of cold working strips seriously affect its processability. In order to improve the cold-working properties of Cu-Ni-Si alloy, two kinds of C70250 copper alloy strips were produced through hot mold continuous casting (HMCC) and cold mold continuous casting (CMCC) technology. The effects of solidified microstructure on the cold-working deformation behavior, mechanical properties, and residual stress of the alloy were studied. The results show that C70250 copper alloys with columnar grain and equiaxed grain were prepared through HMCC and CMCC. After a 98% reduction in cold rolling, columnar grain strip surface quality was very good, and the elongation was still as high as 3.2%, which is 2.9 times that of equiaxed grain alloy. The residual stress of equiaxed grain strips reached 363 MPa, which is 2.7 times that of columnar grain strips. During the cold rolling process, equiaxed grain strips are prone to cause intersecting plane dislocations, stacking faults, shear bands, and grain breakage during large deformation cold rolling. The columnar grain strip causes parallel plane dislocations, stacking faults, and shearbands. Furthermore, the deformation structure was found to be uniform, and, ultimately, the alloy formed a fibrous structure. Therefore, the elongation and latter distortion of columnar grain strips improved after being put through large deformation cold rolling, which greatly reduced residual stress.

Basic principles of the continuous casting technology development for machine‑building blanks

It is shown that during developing continuous casting technology, it is necessary to solve a number of tasks related to finding the optimal technology option, creating special equipment to expand the range of cast blanks and calculating optimal parameters. The profile, dimensions and material of the blanks determine the continuous casting method choice and the installation type. Designs of the most important components and mechanisms are being developed for the selected type of installation. For the selected design solution, based on the lesson learned and available research, optimal thermal and technological parameters of casting are calculated.

An integrated production batch planning approach for steelmaking-continuous casting with cast batching plan as the core

The development of the high-efficiency continuous casting technology makes it possible to continuously cast with multi-cast batching plans. The preparation of such steelmaking-continuous casting (SCC) production batching plan has become a new requirement to promote the efficient steel production. From the perspective of overall production system, an integrated approach with the cast batching plan as the core was proposed, which changes the step-by-step optimization way of combination and sequencing for preparing charge batching plan and cast batching plan sequentially. This approach, which can perform integrated combination and sequencing, directly prepares the SCC production batching plan with multiple cast batching plans that can be continuously cast, and takes into account the charge batching plans. Taking minimizing the weight of unplanned slabs, maximizing the production efficiency of continuous casters, and minimizing the penalty value for the change of dimensions of the adjacent slabs as the objectives, a multi-objective mixed-integer programming model was established. An improved NSGA-II combined with a local search strategy was designed, and the practical aspects such as multiple grades continuous casting rules and on-line width adjustable rules were considered. The test result with data from a steel plant in China indicated that the improved algorithm could obtain better slab combination sequence results compared with the NSGA-II and SPEA2. Simultaneously, compared with the manual approach and the traditional approach of preparing the charge batching plan and cast batching plan sequentially, the integrated approach can not only reduce the residual material rate by 4.96% and 0.42%, improve the quality of the solution, but also improve the efficiency of planning.

Numerical and Physical Study on New Simple Design of Subflux Flow Controller for One-Strand Tundish.

Tundish metallurgy is essential for continuous steel casting technology. In this study, the subflux flow controller (SFC) installed in the tundish pouring zone was tested, demonstrating the possibility of simultaneously reducing the dimensions of the flow control device (FCD) and effectively influencing the structure of the liquid steel flow. On the basis of computer simulations and water model trials, results were obtained describing the hydrodynamic structure in considered variants of the one strand slab tundish. Considering the influence of the SFC on the steel flow structure in the tundish, and the gradient of the wall shear stress and total pressure on the SFC surface/tundish walls, the most optimal SFC variant for a single-strand wedge-type tundish is SFC No. 2C.

High strength and high electrical conductivity C70250 copper alloy with fibrous structure reinforced by high density, multi-scale nano-precipitates and dislocation

Cu–Ni–Si alloy has a difficult combination of high strength and high electrical conductivity, which limits its further application in electronics industry. In this work, the effects of large deformation double cold rolling-aging processes on the microstructure, mechanical properties and electrical conductivity of the columnar grain alloy were studied, and its mechanism was revealed. The results show that the C70250 copper alloy strip prepared by hot mold continuous casting technology can be directly subjected to large deformation double cold rolling-aging treatments without solid solution process. The excellent balance of tensile strength and electrical conductivity, as high as 884 MPa and 45.7% IACS, respectively, can be obtained for the alloy after primary 95% cold rolling and aging at 450 °C for 45 min followed by secondary 60% cold rolling and aging at 400 °C for 10 min. The strength and electrical conductivity is better than the similar products reported. The realization of high strength and high electrical conductivity is attributed to the interaction between strain hardening and precipitation behavior of columnar alloy during double deformation and aging treatment. The repeated introduction of large deformation cold rolling provides a new short diffusion driving force for the precipitation of solute atoms by GPA and APT results, the precipitation rate is increased in the second stage of aging. At the same time, the nanometer-sized strengthening phase formed by primary aging can effectively nail the dislocations formed in the secondary cold rolling process, and finally form a fibrous structure with uniform mixing of multi-scale nano cluster and Ni2Si phase. The strength of the alloy is significantly improved by dislocation strengthening and multi-scale precipitation strengthening. C70250 copper alloy precipitate as many solute atoms as possible, and retains fibrous structure, the dispersing of electrons by solute particles and grain boundary limits is fundamentally diminished, and the electrical conductivity is improved.

Elimination of Primary NbC Carbides in HSLA Steels for Oil Industry Tubular Goods

Two high-strength low-alloyed steels alloyed with various Nb contents were prepared using continuous casting (CC) technology. In the round Steel 30Nb CC billet, it was the segregation of C and Nb in the central equiaxed zone that promoted the precipitation of primary NbC carbides at grain boundaries. After processing into seamless tubes, micron-sized primary NbC carbides were located in the middle of the segregation bands, surrounded by many nano-sized NbC carbides formed during the post-solidification cooling and/or hot-piercing rolling. Even when the Nb content was decreased down to 0.006 wt.%, there were still coarse primary NbC carbides in the segregation bands. However, no primary NbC carbide was found in the round Steel 30Nb billet prepared using the electroslag remelting technology. Therefore, this study revealed that a rapid solidification rate was relatively effective in eliminating primary NbC carbides compared with merely decreasing the Nb content.

Improvement of the secondary cooling mode for continuous casting of round billets at Ural Steel JSC

Formation of hot cracks on continuously cast round billets is the frequent problem in metallurgical production. The article presents the results of a study of the macrostructure, surface quality and technology of continuous casting of round billets with a diameter of 455 mm, produced at the bloom caster of Ural Steel JSC. The main defects of such billets are identified as surface cracks of “combined” type, namely, transverse cracks (the share among the billets with defects is 9.1%), cracks of the mesh form (the share among the billets with defects is 8.3%). The main reasons for the unsatisfactory quality of the ingot are determined: increased overheating of metal in the tundish, which can be partially compensated by reduction of the casting speed, and intensive cooling of billet surface in the first segments of secondary cooling, which increase thermal stresses in metal with consequent heating of surface layers. It was decided that the most effective way to minimize billet defects is to improve the secondary cooling technology in compliance with the regulated casting temperature and speed procedure. Thermal calculations of billet solidification are conducted. It was revealed that overcooling of billet surface occurs in the first segments of secondary cooling under the existing secondary cooling modes and temperature and speed modes of casting, which leads to additional thermal and phase stresses. In the third segment of the secondary cooling zone, heating of the billet surface is observed due to the heat of the central part. Rational flow rates of cooling agent for the secondary cooling segments of the bloom continuous casting machine are proposed. They include expansion of the active section of secondary cooling with a reduction of cooling agent consumption in the first segments will reduce the thermal cycling processes in the hardened crust and minimize the likelihood of cracking. The work was conducted under financial support of the RF Ministry of Science and High Education (project No. FZRU-2020-0011).

Analysis of the causes and conditions for the formation of surface defects on hot‑rolled products from peritectic steel grades obtained under the conditions OJSC “BSW – Management Company of the Holding “BMC”

OJSC “BSW – Management Company of the Holding “BMC” produces a wide range of carbon, high‑quality, alloyed and high‑carbon steel grades, among which a signifi ant share is peritectic grade steels. Basically, the steel of this group is used to produce rolled products intended for the manufacture of components for the automotive industry. The process of production and casting of these steels is characterized by the greatest instability and is often accompanied by rejects and forced sorting of products. This situation is typical for other metallurgical enterprises. Therefore, the search for technological solutions that ensure an increase in the yield while maintaining the existing productivity of metallurgical units is an urgent aspect of improving the technology of continuous casting of peritectic grade steels. At the same time, the main scientific and technical task is to obtain a stable quality of continuously cast billets, aimed at preventing and eliminating the formation of a number of characteristic defects, primarily cracks on the surface of continuously cast billets and rolled products. The search for methods and technological solutions to improve the quality of products made of peritectic grade steel is the goal of the ongoing research.

The influence of continuous casting technology on the cleanliness of carbon steel

The influence of the production method, i.e. casting technology on the cleanliness and thus the quality of carbon steels is best determined through the presence and type of non-metallic inclusions. A large number of inclusions, especially oxide and complex ones, can significantly affect the mechanical properties of carbon steels and limit their application for the production of finished products. This paper presents the influence of the presence, type and amount of non - metallic inclusions in B500B carbon steel according to ASTM / AISI produced by continuous casting technology without and with the application of stream protection.