Finished Steel Products Research Articles

Overview of Multi-Scale Simulation Techniques for Three Typical Steel Manufacturing Processes.

Steel products typically undergo intricate manufacturing processes, commencing from the liquid phase, with casting, hot rolling, and laminar cooling being among the most crucial processes. In the background of carbon neutrality, thin-slab casting and direct rolling (TSCR) technology has attracted significant attention, which integrates the above three processes into a simpler and more energy-efficient sequence compared to conventional methods. Multi-scale computational modeling and simulation play a crucial role in steel design and optimization, enabling the prediction of properties and microstructure in final steel products. This approach significantly reduces the time and cost of production compared to traditional trial-and-error methodologies. This study provides a review of cross-scale simulations focusing on the casting, hot-rolling, and laminar cooling processes, aiming at presenting the key techniques for realizing cross-scale simulation of the TSCR process.

A bottom-up assessment of recent (2016–20) energy use by the global iron and steel industry constrained to match a top-down (International Energy Agency) assessment

This paper presents the first estimates, at the global scale, of energy use by energy type associated with individual steps in the production of fabricated steel products. Estimates are averaged over the period 2016–20, based on a synthesis of literature regarding energy use for (i) preparation of iron ore; (ii) production of iron in a blast furnace (BF) and as direct reduced iron; (iii) production of refined steel in the basic oxygen furnace or electric arc furnace; (iv) steel casting, hot and cold rolling, and coating; (v) fabrication of intermediate steel products; and (vi) processing of scrap. The International Energy Agency provides separate global energy use for coking, transformation energy use by BF, and by the remainder of the iron and steel industry (rISI) including the remaining BF energy use. With re-allocation of the BF portion of rISI back to BF, and a 9% increase in literature-based estimates of energy intensity across all production steps except coking, bottom-up and IEA estimates of total energy use agree. The resulting mean cumulative energy intensity of fabricated steel products is 24.1 GJ/t. The energy content of the lost iron equals about 10% of the total energy used in producing finished steel products.

AI assisted steel cleanness evaluation: Predicting the morphology of La-traced non-metallic inclusions using backscattered-electron images

This study shows how computer vision, a field of artificial intelligence (AI), can be used to gain access to morphological information for a better process understanding and furthermore, how it can be implemented in the evaluation of active tracing experiments. Non-metallic inclusions (NMIs) play a crucial role in determining the chemical and physical properties of the final steel product. The active tracing technique allows for tracking the formation and modification mechanisms of detrimental NMIs throughout the steelmaking process by adding rare earth elements (REEs) to the melt. The interaction of REEs with NMIs results in the formation of traced multiphase particles and, therefore, lead to challenges for accurate evaluation by automated scanning electron microscopy with energy-dispersive spectroscopy (SEM/EDS). However, obtaining information about the REE distribution in traced NMIs without extensive, time-consuming human effort is not feasible using the existing method. A two-step classification process with AI was established, which included training and testing of two random forest classifiers (RFC). The first RFC achieved for the binary NMI/non-NMI classification an accuracy of 94.8 %. Four different morphology-based classes were considered in the second classification, whereas traced homogeneous NMIs and NMIs with a high La content got classified with a precision exceeding 90 %. However, caution is required in interpreting results for traced heterogeneous NMIs, as they have a higher prediction error of 37.2 %.

Thermal cycling to improve the impact toughness of 1Cr11Ni2W2MoV steel with banded microstructure

Microscopic segregation of chemical elements results in the banded microstructure of finished steel products, and the harmful effect of banded microstructure on toughness is well recognized. However, typical industrial hot work processing, such as hot rolling and forging, cannot erase the banding, and eliminating it with homogenization heat treatment is also challenging and uneconomical. In this study, the impact energy of a 12%Cr tempered martensitic steel with the banded microstructure was significantly improved from 74 J to 154 J by employing thermal cycling and tempering as the final heat treatment to meet the service performance requirement. Compared to conventional quenching and tempering (Q + T), thermal cycling and tempering (TC + T) simultaneously refined the effective grain size of tempered martensite matrix and coarse M23C6 carbides that were continuously distributed along the δ-ferrite/matrix phase boundaries. As a result, more high angle grain boundaries (HAGBs) were introduced and acted as obstacles in retarding the propagation of microcracks. Additionally, finer carbides precipitated at the banding boundary during tempering, owing to the increasing triple junctions between δ-ferrite and tempered martensite. These finer carbides prevent the initiation of microcracks. The results demonstrate the potential of TC + T as a final heat treatment to remove the detrimental effect of banded microstructure on impact toughness.

Modification of Inclusions by Rare Earth Elements in a High-Strength Oil Casing Steel for Improved Sulfur Resistance

Steel casing pipes used in the construction of deep oil wells usually require both high strength and corrosion-resistant behavior. Due to the exploration of deep H2S-bearing oil reservoirs, sulfide stress cracking (SSC) is becoming an increasingly serious concern for casing steel. The nonmetallic inclusions in the steel are among the key reasons for its service failure. The rare earth element Ce can be used to modify the inclusions in casing steel and improve its SSC resistance. Here, taking C110 grade casing steel (the highest class currently in service) as the investigated object, the modification behavior of Ce inclusions in the steel and the effect of the addition of Ce in varying amounts (0.01, 0.024, and 0.042 wt.%) on the modified products were studied through high-temperature tube furnace experiments and thermodynamic calculations. The results showed that Ce had an obvious modification effect on the CaO·Al2O3 inclusions in casing steel, and the diffusion of dissolved Ce in the steel was the limiting step of the modification reaction. With the extension of reaction time, the sequence describing the modification of inclusions in the steel was determined as follows: CaO·Al2O3 → CeAlO3 → Ce2O3/Ce2O2S. The final stable product after modification depended on the amount of Ce added. With 0.01 wt.% Ce, the stable phase in molten steel was Ce2O3; on the other hand, upon adding ≥0.024 wt.% Ce, the stable phase became Ce2O2S. In addition, the thermodynamic stability of Ce2O3 decreased, and it was transformed into CeAlO3, Ce2O2S, Ce2S3, and CeS during solidification. On the basis of our results and the considerations for smooth casting, the addition of a proper amount of a rare earth element is suggested for industrial trials, following the achievement of a significant and surprising improvement in the qualified rate of SSC resistance for the final steel products. The relevant mechanism is also analyzed.

Predicting Grain Structure in Continuously-Cast Stainless Steel Slab

Macrostructural features in continuously-cast stainless steel slabs such as the distribution of equiaxed and columnar grains, and microporosity, are crucial to the post-processes, and the mechanical properties of the final steel products. Among the methods for controlling grain structure during the continuous casting process, the application of electromagnetic stirring (EMS) during casting is known to alter the grain structure of the slab. In this study, we predicted macrostructural features in a continuous-cast stainless steel slab using computer simulation. We approximated the heat transfer system as a one-dimensional heat conduction model with solidification. The effect of EMS was investigated by introducing an effective thermal conductivity of the melt. We assumed that EMS caused turbulent flow, and enhanced the thermal conductivity. Columnar-to-equiaxed transition (CET) and microporosity were estimated with the models proposed by Hunt and Niyama, respectively. The effect of EMS on microporosity was negligible, and microporosity was inevitable in the centerline of the slab. EMS made a second equiaxed region between the outer wall and the center of the slab. Because the effective thermal conductivity was high due to EMS, the temperature field in the slab was distorted, and the Hunt criterion for CET was satisfied in the region. The CET results were compared and verified with cellular automata simulation. Various process parameters including casting speed, superheating, and the position of the EMS module, were examined to predict the macrostructure of the slab.

Advanced Soft-Sensor Systems for Process Monitoring, Control, Optimisation, and Fault Diagnosis

As processes become more complex and the need to measure each and every variable becomes more critical, the ability of physical sensors to always provide the sufficient accuracy and sampling time can be difficult. For many complex systems, such as nonideal mixtures, multiphase fluids, and solid-based systems, it may not be possible to even use a physical sensor to measure the key variables. For example, in a multiphase fluid, the concentration or density may only be able to be accurately estimated using a laboratory procedure that can only produce a limited number of samples. Similarly, the quality variables of steel may only be determinable once the final steel product has been produced, which limits the ability to effectively control the process with small time delays. In such cases, recourse has to be made to soft sensors, or mathematical models of the system that can be used to forecast the difficult-to-measure variables and allow for real-time process monitoring, control, and optimisation. Although the development of the soft-sensor model is well-established, the various applications and use cases have not been often considered and the key challenges examined. It can be seen that soft sensors have been applied to a wide range of processes from simple, chemical engineering systems to complex mining processes. In all cases, major improvements in the process operations have been observed. However, key challenges remain in updating the soft-sensor models over time, combining laboratory measurements, especially when they are infrequent or of uncertain quality, and the development of soft sensors for new conditions or processes.

Analysis of the use of magnesium-containing additives in the charge of iron flux in order to reduce CO2 emissions

The growing requirements for the quality of finished steel products oblige to obtain steel with a low content of harmful impurities, especially sulfur. The main charge for steel production in the conditions of JSC EVRAZ NTMK is vanadium iron, the external desulfurization of which leads to large losses of valuable vanadium. Therefore, the smelting of iron with a low sulfur content is an urgent task. The main way to reduce sulfur in iron is to increase the basicity of the slag (B2), but MgO is the best desulfurizer. The paper evaluates the effectiveness of the use of various magnesium-containing materials in the conditions of the blast-furnace stage of JSC EVRAZ NTMK, taking into account CO2 emissions. The possibility of replacing limestone in the iron flux charge with dolomite, as well as with steel converter slag, is considered. Both materials will increase the proportion of MgO in blast-furnace slag, however, the use of dolomite is accompanied by a two-fold increase in CO2 emissions compared to limestone. Converter steel slag (CSS) does not contain carbonates, thus eliminating the formation of CO2 during the limestone decomposition. An additional advantage of CSS is its high content of valuable vanadium and manganese. The effect of an increase in MgO in slag on its melting point is considered. It has been established that an increase in the proportion of MgO to 14% will not cause difficulties in the processing of blast-furnace smelting products and will reduce the sulfur content in iron and the formation of titanium carbides and carbonitrides.

Simulation of Inclusion Particle Motion Behavior under Interfacial Tension in Continuous Casting Mold

Inclusions entrapped by the solidifying front during continuous casting adversely affect the properties of the final steel products. In this study, we investigated the effect of the interfacial tension due to surfactant concentration, particularly sulfur, on alumina inclusion motion behavior during molten steel solidification in a continuous casting mold. A two-dimensional numerical model was developed in Ansys Fluent software to simulate the inclusion motion in a continuous casting mold. Further, the impacts of different values of the alumina inclusion diameter, sulfur concentration, and melt temperature were studied to understand the inclusion motion behavior. The inclusion diameter affected the inclusion distribution throughout the domain. The alumina inclusion entrapment percentage varied in the case of sulfur mixing (using an empirical relationship for modeling). It was found that the removal percentage varied according to the sulfur concentration. The addition of sulfur at concentrations from 10 ppm to 70 ppm resulted in a 4% increase in the removal of alumina inclusions (trapped in the solidifying shell), except for the 100-ppm case. Smaller-sized inclusion particles had a 25% higher chance of entrapment at the top level of the mold. Under the effect of a higher surface tension gradient between inclusions and the melt, the predicted findings show that inclusions were vulnerable to engulfment by the solidification front.

Modeling and Simulation of Steel Rolling with Microstructure Evolution: An Overview

As part of rolled steel's design and optimization, computational modeling and simulation are increasingly applied for predicting the properties and microstructure of final steel products. The time and cost of resorting to traditional trial‐and‐error‐based methods can be significantly reduced using the computational method. Among the numerical approaches, the finite‐element (FE) method has been customarily utilized in various cold and hot rolling processes over the years for its numerical efficiency and precision. The rolling process involves a thermomechanical–metallurgical phenomenon, and thus the interdisciplinary coupling of these is a challenge to rolling simulation and modeling the scientific community. Herein, recent studies on FE modeling for predicting rolled shape, microstructural, and mechanical properties, among others, in steel rolling are extensively reviewed. An overview of the recent progress of the computational methods in multiscale computational architecture, which models the microstructural evolution and phase transformation by various sources, is particularly highlighted.

Deoxidation and modification of steels with reduced silicon content

The object of research is the processes that affect the mechanical characteristics of steels after the treatment of melts with silicon-free complex master alloys according to existing technologies. One of the most problematic places is the negative effect of silicon on the weldability of low-alloy steel, sharply increasing the heterogeneity of welds in sulfur and phosphorus and increasing their susceptibility to hot cracks. The cyclic strength of welded joints decreases markedly with an increase in the silicon concentration of steel. Also in this case, there is a threat of the formation of silicon monoxide, which significantly increases the fragility of the finished steel products. Also, steels processed with alloys containing silicon are prone to decarburization, the formation of surface defects during hot working and graphite formation, which reduces their endurance limit. In the research it was possible to prove that the use of silicon-free complex ligatures (SFCL) in smelting made it possible to obtain an increase (2–3 times) in the entire complex of mechanical and operational properties, especially ductility, impact strength at normal and negative test temperatures (cold resistance) , fatigue strength. In some cases, the level of properties of cast metal reaches the deformed version of its manufacture, for example, rolled products and even metal obtained by electroslag remelting. Processing of the melt of various BKL steels when tapping from the furnace into a pouring ladle instead of aluminum master alloys, silicocalcium and ferrocerium (according to the current technology) provided the required level and high stability of the mechanical properties of 20GML steel. Also, thanks to the use of BCL, it was possible to reduce the consumption of ligatures and deoxidizers by 4.2 kg per ton of liquid metal and increase the yield of rejection of casting defects by 6–10 %. It has been established in the work that BCL treatment leads to stabilization of the chemical composition, refinement of the grain structure of steels, as well as an increase in its dispersion and the level of mechanical characteristics.

Reconciling global iron and steel mass flow datasets, with an update to 2011-2015 and an assessment of uncertainty in global end-of-life scrap flow

The first part of this paper constructs global flows of steel for 2011-15 from usable iron ore, to the production of pig iron (hot metal) and direct reduced iron, crude steel, and hot- and cold-rolled products, through to 19 intermediate products (IPs) that are inputs to the fabrication of final steel products. Flows are constructed so as to exactly or closely match the amounts of each IP or group of IPs as given by the Steel Statistical Yearbook (SSY), while starting from the usable iron ore amount as given by the SSY, and matching various intermediate quantities as closely as possible (given the inconsistencies in the SSY data). The starting points of this analysis are the flow structure and methods used by Cullen et al. (2012; henceforth C2012) to construct global flows for 2008. However, some data sources available for 2008 are not available for more recent years, new datasets have become available, and revisions to some of the data used for the 2008 reconstruction have rendered some of the fractional shares used by C2012 implausible. Modifications to the approach used by C2012 are developed here and applied to the 2011-15 data. The second part of this paper allocates the global IP amounts, as given by the SSY, among 11 end-use sectors. The flow model provides an estimate of the global supply of end-of-life scrap, along with its uncertainty.

Future Scenarios for Reducing Emissions and Consumption in the Italian Steelmaking Industry

The amount of CO2 emissions, water and electricity consumption, and soil exploitation of the main steel production routes (integrated cycle, scrap recycling, and direct reduction) are analyzed applying three possible future scenarios: use of carbon capture and storage (CCS); use of green hydrogen in substitution of natural gas; use of biomethane. Using actual process data and theoretical assumptions, the emissions and consumptions of the whole steel production cycle (from the iron ore extraction to the final steel product) are computed, taking into account also the auxiliary sources of emissions (i.e., limestone calcination and gas compression). The assessment results have highlighted the huge energy requirements and soil exploitation related to the application of green hydrogen in the steelmaking cycle, despite its low CO2 emissions. On the contrary, the use of biomethane appears more attractive if combined with carbon capture and storage systems. Overall, the results of the assessment provide a starting point for understanding the current level of sustainability of steel production and allow the identification of the most promising and plausible scenario for the steel industry of the future and the possible criticalities of each.

Artificial Inclusion Environments—Replicating Industry in the Laboratory

The authors present a series of complementary test methods which were developed and used to investigate reactions between high aluminium steel and silica rich inclusions. Non-metallic inclusions (NMIs) cause many defects in the final steel product, therefore the ability to track their size, morphology and composition and correlate this with fundamental reaction kinetics provides important knowledge to support the production of clean quality steel products. Novel steel grades such as TRIP, TWIP and low-density steels have high aluminium contents; aluminium is a readily oxidisable species presenting the potential for instability and excessive reaction with commonly used mould powders that contain silica. A novel combination of techniques including HT-CLSM (High-Temperature Confocal Laser Scanning Microscope), XCT (X-ray computed tomography) and SEM/EDS (scanning electron microscopy/electron dispersive spectroscopy) have been used to study the interaction of entrained mould powder inclusions with steel at high temperatures simulating industrial conditions. This report presents a discussion on the development of techniques and samples to achieve representative and repeatable results that can provide information on the complex chemical and physical interaction phenomena with confidence. Each experimental technique had its own learning points and consequent results. Outcomes presented include possible confirmation of the chemical reaction rate controlling step being aluminium mass transfer; heterogeneous local environmental conditions including fluidity and chemical composition; and occurrence of spontaneous emulsification where the mould powder inclusion breaks apart into a cloud of smaller fragments.

Collision-coalescence among inclusions with bubble attachment and transport in molten steel of RH

Inclusions can lead to various defects in the final steel products, and RH vacuum refining is an effective and vital technology to remove inclusions from molten steel. By the computational fluid dynamics (CFD) method, the inclusion mass/population conservation model is developed to have a deep insight into the inclusion transfer behavior in the argon molten steel flow of RH. Particularly, the argon slip velocity is introduced into the inclusion convection velocity in the mathematical model, and the inclusions attached by argon bubbles can return to the molten steel when bubbles escape from the free surface of the vacuum chamber. The numerical results of the fluid flow and the inclusion transfer behavior are validated by the measured data in the actual experiment. The argon bubbles significantly enhance the inclusion transport and collision-coalescence process. Besides, the variations of the inclusion volume concentration and the inclusion number density in the up snorkel are about 2 times those in the down snorkel. The number of inclusions with diameters less than 10 μm decreases with the vacuum treatment time, while the number of inclusions with diameters greater than 10 μm increases first and then decreases gradually. Near the free surface of the ladle, there are the greatest inclusion volume concentration, the greatest inclusion number density and the lowest inclusion characteristic radius.

Modeling of Inclusion Capture in a Steel Slab Caster with Vertical Section and Bending

Particles in molten steel, including argon-gas bubbles, slag droplets, and non-metallic inclusions, are removed into the surface-slag layer or captured by the solidifying steel-shell during continuous steel casting. Captured particles often become serious defects in the final steel product, so understanding particle-capture mechanisms is important for steel quality. Slab casters often have a straight mold and upper-strand prior to a curved lower-strand. The present work investigates particle capture in such a caster using computational modeling with a standard k-ε model for molten-steel flow, a discrete phase model for inclusion transport, and an advanced capture criterion for inclusion entrapment and engulfment into the steel shell. A new postprocessing methodology is presented and applied to predict inclusion-capture rates in commercial cast product. The locations and size distributions of particles captured into the shell, and actual capture rates are quantified. The model predictions are validated with ultrasonic-test plant measurements of the locations of large particles captured in a steel slab. The results reveal how large-inclusion capture accumulates in the beginning of the curved strand, leading to a capture band in the slab inside radius. Finally, the capture fractions and locations due to all capture mechanisms are compared for different inclusion sizes, and the implications are discussed.

Adaptive Mesh Refinement Method for Speeding Up Numerical Simulation of Electroslag Remelting Process

The electromagnetic field and the droplet profile in electroslag remelting (ESR) process play a pivotal role in the quality of final steel products. Numerical simulation remains a central challenge to investigate ESR process with a high‐efficiency and high‐accuracy method. Herein, a strategy embedding an adaptive mesh refinement (AMR) method in 3D‐coupled model is proposed to speed up the simulation of ESR process. The coupling phenomena of the electromagnetic field and the droplet profile are successfully predicted using this method. Compared with the results of uniform mesh, the deviation of AMR results is less than 2.2%, whereas the computational speed of the AMR method is 10 times faster. Moreover, the effects of two key parameters in AMR method, maximum refinement level and refinement interval, on computational accuracy and speed are studied. With the increasing maximum refinement level, the computational accuracy is improved obviously first and then slightly, but the computation time increases exponentially. The increasing refinement interval has little effect on the computational accuracy but can greatly save the time of mesh operation. The proposed strategy can promote the application of numerical simulation in industrial ESR process.

MATHEMATICAL MODELING OF THE TEMPERATURE FIELD OF WARM ROLLING MILLS ROLLS THAT HAVE AN INTERNAL HEATING SOURCE

Recently, a fairly common method of expanding the range of finished steel products is to obtain metal products with given, sometimes unique properties due to the use of warm rolling modes in the temperature range before recrystallization. There are two approaches to implementation of warm rolling process. The first one involves non-invasive heating of the strip before the deformation zone. The second approach prefers additional heating of sheets or strips directly in the deformation zone due to the contact heat exchange with the working rolls preheated to certain temperatures. From the point of view of reconstruction of the existing equipment, convenience and speed of regulation of heating temperature, stability of work and, finally, efficiency and environmental friendliness, the most reasonable is to use internal heating of working rolls. The implementation of this approach is also effective in terms of minimizing oxidative processes. It should be noted that the rolls in such a scheme plays a significant role in the formation of the resulting temperature field of the strip, and, therefore, significantly affect the final properties of the products. The paper presents a mathematical mo-dele of the temperature field of the working rolls of warm rolling mills with an internal heating point. Numerical implementation of the model is carried out on the basis of superposition approach, which provides for the breakdown of the roll cross-section into ij-nodes in the period of time. The results showed significant heterogeneity of temperature distribution both in radius and outer surface, as well as the presence of maximum at the exit from the deformation zone and minimum in the section before it.

Optimizing ladle-refining performance during treating special steel melts for aviation technology

The ever increasing demands of consumers towards superior quality steel products urged steelmakers to consider the implementation of various relatively new metallurgical technologies into the classical operations. The necessity to produce high quality steels led to the use of two stage steel production processes, one is the primary steelmaking and the other stage is the outside furnace treatment through which many metallurgical functions can be achieved like degassing, stirring and inclusion removal, Inclusion modification, desulphurization, deoxidation, decarburization, heating and alloying. In this research a trial was done to optimize the performance and usage of 30tons-ladle refining system during production of X65-pipeline steel as final product-Aluminium killed steel melts through controlling the mass flow contour using optimized modelling, optimum usage of Al2O3 and Sulphide modifiers and enhancing removal of non-metallic inclusions by altering their morphologies and hence floatation speed. Assessment of fine clusters of inclusions in the final steel product has been industrially correlated to the cleanness of melt before refining, to the slag composition and to the parameters of materials flow rates as well as their effects on the mechanical properties of final X65-steel product. Scanning-EM+DX analyzing unit and metallurgical microscopes were used to emphasis qualitatively and quantitatively the characters of non-metallic inclusions.

Assessment of Critical Hydrogen Concentration in As‐Cast and Hot‐Rolled Billets in Medium Carbon Steels

The presence of hydrogen severely affects the mechanical properties of semi‐manufactured and final steel products. Such presence is affected by different factors which show up throughout the whole manufacturing process and varies during the different stages according to both product features and various process parameters. This article presents an experimental methodology to assess the critical hydrogen concentration in as‐cast and hot‐rolled billets in medium carbon steels, which allows highlighting their robustness to hydrogen embrittlement. Such approach is based on a combination of hydrogen‐induced cracking and slow strain rate tensile tests, which are conducted on both as‐cast and hot‐rolled billets samples. The experiments highlight that the hydrogen presence is more critical on the as‐cast semi‐products than on the hot‐rolled billets, which show a higher robustness, as they can tolerate higher values of hydrogen content.