Hot Rolled Coils Research Articles

Effect of location on green steel production using Australian resources

Hydrogen is being increasingly considered as a chemical feedstock and energy storage vector within the iron and steel industry. This study compares the cost and CO2 emissions associated with green steel production as a function of location for the components in its supply chain between Australia (Pilbara) and China (Beijing). Results are benchmarked against a new facility using conventional coal-based technology, producing Hot Rolled Coil (HRC) steel in China as a common final product. Green steel production in Australia using hydrogen is considerably cheaper and presents lower emissions than exporting the hydrogen and iron ore to China for subsequent processing. Costs are comparable when intermediate Hot Briquetted Iron (HBI) is exported but with increased emissions. However, utilising blue hydrogen produced in China is the most immediately dispatchable with a 35% reduction in CO2 emissions and an increase in levelised cost of steel (LCOS) of only 11% relative to current practice.

Tension fracture delamination analysis on a hot rolled Nb-bearing high-strength steel for vehicle wheel application

A comparative analysis was conducted on post-tensile specimens with and without delamination to investigate the causes of tensile delamination in hot rolled steel with a 600 MPa ultimate tensile strength (UTS) for automotive wheel applications. The tensile specimens were sampled from the hot rolled coils in the transverse direction per ASTM A370 standards, and Tensile tests were performed at room temperature with a constant crosshead speed of 0.5 mm/min. The results indicate that normal segregation is not the sole factor contributing to delamination; rather, the presence of Nb lumps within the central segregation area increased the susceptibility to tensile delamination. The statistical analysis indicates that there is a more intense presence of Nb lumps in specimens with tension delamination, tension delamination will occur during specimen stretching when there are Nb lumps with an average size greater than 6.5 μm and a quantity greater than 3 in the central segregation region. Meanwhile, the sources of lumps are also analyzed indicates that these Nb lumps originate from the ferroniobium alloy added during BOF tapping and ladle refining.

The effect of thickness of the hot-rolled sheet on the magnetic properties of non-oriented electrical steel

Non-oriented (NO) electrical steel sheets with a thin thickness are drawing interest as potential materials for electric vehicle drive motor cores due to their ability to reduce high-frequency core loss. To produce electrical steel sheets with a thickness of 0.25 mm or less, it is beneficial to minimize the thickness of the hot-rolled sheets. However, it is well known that it is difficult to achieve hot-rolled coils with a thickness of 1.4 mm or less with a conventional hot rolling process. Therefore, the thin slab casting and rolling (TSCR) process is now used to produce thin hot-rolled coils that cannot be produced by conventional methods.In this study, we investigated the effects of hot-rolled sheet thickness produced by the TSCR process and cold-rolling reduction ratio on the crystallographic texture, microstructure, and magnetic characteristics of 3% Si NO steel. The results showed that the textures of the hot-rolled sheet and the annealed hot-rolled sheet are virtually unaffected by the hot-rolling reduction ratio. However, the cold-rolling reduction ratio substantially affects many aspects of NO electrical steels. The recrystallized grain size after the final annealing process decreases as the cold reduction ratio increases, while the magnetic flux density decreases with increasing cold reduction ratio, especially for reductions exceeding 82.8 %.In conclusion, the thickness of hot-rolled steel sheets manufactured by the TSCR process has little effect on the microstructure and texture of hot-rolled sheet. Therefore, reducing the cold rolling reduction ratio, which can be achieved by using thin hot-rolled sheets manufactured by the TSCR process, is a promising method for enhancing the magnetic characteristics of thin-gauge NO electrical steel sheets.

Utilizing Lean Six Sigma and Waste Assessment Model to Reduce Waste in the Hot Rolled Coil Production

The global steel industry is pivotal, driven by substantial demand. In Indonesia, a leading steel manufacturing company, boasting significant production capacities for Hot Rolled Coil (HRC) and Cold Rolled Coil (CRC) products, with capacities of 2,400,000 and 850,000 tons per year. However, current production lags at 1,500,000 and 500,000 tons annually for HRC and CRC. Notably, the production process recorded defect ratios of 15.85%, 15.65%, and 15.56% from 2020 to 2022, with waste waiting accounting for a breakdown time and operating time ratio of ±40%. The study employs Lean Six Sigma to analyze and mitigate waste during HRC production, aiming to augment product value, production efficiency, and cost reduction. Through Value Stream Mapping and Process Activity Mapping, 44.93% of Necessary Not Value- Added Activities (NNVA). In the next stage, critical wastes including waste defects, overproduction, and waiting are selected using the Waste Assessment Model. The Analysis stage employs fishbone diagrams and Failure Mode and Effect Analysis to determine root causes and assess risk. Proposed improvements include toolbox meetings, maintenance scheduling, check sheets, a work roll replacement algorithm, and sensor adjustments, projected to raise sigma values significantly for waste defects, overproduction, and waiting.

Application of Overall Equipment Effectiveness and Failure Mode Efffect and Criticality Analysis Methods to Improve Machine Performance Effectiveness

PT XYZ is a company that produces hot rolled coils (HRC) steel products. One of the machines used in the process is a rough mill machine in the milling process. The problem is downtime on the rough mill machine that disrupts the production process time. The purpose of this study is to determine the value of the effectiveness of the machine, find the largest losses that affect the value of the effectiveness of the machine, identify the cause of the biggest losses and provide recommendations for improvement steps. The methods used are overall equipment effectiveness (OEE), six big losses, and the failure mode effect and criticality analysis (FMECA). The results show that the average OEE value of PT XYZ is 80%, but this value was still not following the ideal standard. By identifying the six big losses, the most significant losses are reduced speed losses, with a total percentage value of 86% and an average time loss of 5,020 minutes. FMECA results obtain three components that cause the biggest losses: the engine motor, gearbox, and spindle. Recommendations for improvement include making and setting schedules, implementing predictive maintenance and preventive maintenance on rough mill machines, and regularly checking and replacing component spare parts.

Investigation of oxide scale adhesion on hot-rolled steel using the tensile test and acoustic emission

This article addresses applying a tensile test with a CCD camera to assess scale adhesion on hot-rolled steel as a function of hot-rolled coil position. The scale adhesion in this study was shown in the value of the strain initiating the first scale spallation. The result of strain initiating the first scale spallation was confirmed with an acoustic emission (AE) method. The as-received hot-rolled coil was studied at the head, middle, and tail positions. A scanning electron microscope (SEM) and X-ray diffraction (XRD) were used to examine the scale morphology and phase identification respectively. The results show that the oxide scale comprises hematite and magnetite layers. It was found that the higher strain initiating the first scale spallation was revealed on the scale formed on the hot-rolled coil at the head and middle positions. This indicates that the oxide scale was more difficult to remove than at the tail position of the coil. The scale growth and cooling affects the stresses on the oxide layer and the steel substrate. A thin oxide layer on tail position of the hot-rolled coil will easily first crack and then buckle and followed by spallation, while a thick scale on head and middle positions of the hot-rolled coil was harder than that thin scale.

Optimization of hot rolling parameters of CRNO steel with the aid of hot compression test and deformation map

Abstract Cold-rolled non-oriented (CRNO) electrical steels find a wide variety of applications in the core of electrical machines due to low core loss and high magnetic permeability. Stringent market conditions not only require CRNO steel with superior magnetic properties but also demand excellent surface conditions. CRNO steel is cold rolled to 0.5 mm in reversing mill. High hot rolled input thickness (>2.6 mm) increases the number of passes during cold rolling and adversely affects the mill productivity. It also results in surface defects such as buckling and coil break. The flow stress of this steel varies differently compared to conventional rolled steel. Thus, it becomes difficult to optimize the reduction schedule and hence safe hot rolling practice is adopted to restrict roll force within permissible limit resulting in higher thickness. A hot compression test was carried out in a Gleeble–3500 to evaluate the flow stress behaviour of this steel and a deformation map was developed to optimize the hot rolling window. The input from the hot compression test and deformation map was used to develop a mill setup model to accurately predict the roll force and optimize the reduction schedule of CRNO steel in the finishing stands of HSM. The final thickness of hot-rolled coils during industrial trials with an optimized reduction schedule was found to be in the range of 2.4–2.6 mm compared to 2.7–3.0 mm during conventional rolling. These coils were further cold rolled and finished in 4–5 passes compared to 6–7 passes with conventional rolling. Reduction in the number of passes has resulted in increased productivity during cold rolling as well as improved surface finish.

Digital Twin Driven End-Face Defect Control Method for Hot-Rolled Coil With Cloud-Edge Collaboration

End-face defect control (EF-DC) of the hot-rolled coil is crucial to the quality management. The core of EF-DC is to identify defects accurately, predict defects in advance, and improve production in time to prevent similar defects. The current research works on EF-DC are mainly at the defect recognition stage, which merely rely on the operating data in physical space. However, different types of defects exist in coils with different reasons, therefore it is difficult to accurately control defects in time only through the hot rolling operating data. In order to solve the above problems, first an EF-DC framework based on digital twin with cloud-edge collaboration is designed in this article. The computing tasks are reasonably allocated through cloud-edge collaboration to realize the timeliness of control. Second, the virtual model of hot-rolled coil is constructed from four aspects: geometry, physics, behavior, and rules. Through the analysis of the defect mechanism, the abnormal behavior events are obtained, and the mapping relationship between the defect and the behavior event is established to realize the defect traceability and control. Finally, the feasibility of the proposed method is verified by taking the edge scratch defect as an example.

Adhesion of thermal oxide scales on hot-rolled steels with 0.026 and 0.193 wt% Si in Ar-20 %H2O at 900 °C

The hot-rolled coil was widely used for forming steel products. The basic problem was that the scale formed on the steel will affect the surface quality of the product. The scale must be completely removed before moving on to the next process. Therefore, the objective of this research was to evaluate the adhesion of scale on the surface of the hot-rolled steel. The hot-rolled with 0.026 and 0.193 wt% Si-containing steels were used to oxidise in Ar-20 %H2O atmosphere at 900 °C for investigating scale adhesion. The scanning electron microscope and X-ray diffractometer were used for the analysis of physical and chemical characterisation. The scale adhesion can be observed using a tensile testing machine that has a CCD camera. The result shows that the thickness of hot-rolled steel with 0.026 and 0.193 wt% Si were 8.4 and 6.3 um respectively. The oxide scale was comprised hematite, magnetite, wustite and iron. The strain initiating the first spallation of scale on the 0.193 wt% Si steel was 5.59 % which was higher than the 0.026 wt% Si steel of 4.79 %. At this strain, the adhesion energy of scale on 0.193 wt% Si steel was 692 J m−2 and 673 J m−2 for 0.026 wt% Si steel. This reveals a greater scale adherence to the steel with higher Si contents. It suggests that silicon alloys may affect the adhesion behaviour of scale on a steel substrate. As a result, higher energy was required to remove scale before further processing.

A data and model-driven predictive diagnosis framework towards hot-rolled coil defect

A data and model-driven predictive diagnosis framework towards hot-rolled coil defect

A data and model-driven predictive diagnosis framework towards hot-rolled coil defect

A data and model-driven predictive diagnosis framework towards hot-rolled coil defect

Development of technology for the production of new materials on traditional wide-strip hot rolling mills using modern methods of numerical and physical modeling. Part 1

A description of the technique for developing the technology for hot-rolled coils manufacturing in the conditions of an existing production, the technology and characteristics of which go beyond the passport characteristics of the equipment, is presented. It is proposed to carry out comprehensive laboratory studies of the developed material (the kinetics of recrystallization processes during heating and rolling, the kinetics of structural transformations, material properties at production temperatures), engineering calculations of the equipment operation and simulation of the strip behavior during the rolling and coiling before the industrial testing of the hot rolled products manufacturing technology. The practical application of the proposed approach is demonstrated by the example of the development of a technology for manufacturing hot-rolled coils from low-carbon boron steel with a minimum yield strength of 1000 MPa. For the developed steel, rational temperature parameters for slabs heating are determined, which exclude the development of collective recrystallization and the formation of an uneven-grained structure, and also limiting deformation modes are defined, which ensure efficient grain refinement and implemented on existing hot strip mills. It has been established that in low-carbon steel a high strength with satisfactory ductility, low-temperature toughness, and the ability to cold forming (bending, profiling, etc.) is achieved due to the formation of a lower bainite structure in rolled products. The required structural state was obtained by applying the technology of interrupted quenching from rolling heating at massaverage cooling rates of about 25 °C/s.The studies were carried out within the program of the Russian Federation of strategic academic leadership "Priority-2030" aimed at supporting the development programs of educational institutions of higher education, the scientific project PRIOR/SN/NU/22/SP5/26 "Development of innovative digital tools for the implementation of applied artificial intelligence and advanced statistical analysis of Big Data in production processes of metallurgical products".

Carbon Footprint and Energy Transformation Analysis of Steel Produced via a Direct Reduction Plant with an Integrated Electric Melting Unit

The production of flat steel products is commonly linked to highly integrated sites, which include hot metal generation via the blast furnace, basic oxygen furnace (BOF), continuous casting, and subsequent hot-rolling. In order to reach carbon neutrality a shift away from traditional carbon-based metallurgy is required within the next decades. Direct reduction (DR) plants are capable to support this transition and allow even a stepwise reduction in CO2 emissions. Nevertheless, the implementation of these DR plants into integrated metallurgical plants includes various challenges. Besides metallurgy, product quality, and logistics, special attention is given on future energy demand. On the basis of carbon footprint methodology (ISO 14067:2019) different scenarios of a stepwise transition are evaluated and values of possible CO2equivalent (CO2eq) reduction are coupled with the demand of hydrogen, electricity, natural gas, and coal. While the traditional blast furnace—BOF route delivers a surplus of electricity in the range of 0.7 MJ/kg hot-rolled coil; this surplus turns into a deficit of about 17 MJ/kg hot-rolled coil for a hydrogen-based direct reduction with an integrated electric melting unit. On the other hand, while the product carbon footprint of the blast furnace-related production route is 2.1 kg CO2eq/kg hot-rolled coil; this footprint can be reduced to 0.76 kg CO2eq/kg hot-rolled coil for the hydrogen-related route, provided that the electricity input is from renewable energies. Thereby the direct impact of the processes of the integrated site can even be reduced to 0.15 kg CO2eq/kg hot-rolled coil. Yet, if the electricity input has a carbon footprint of the current German or European electricity grid mix, the respective carbon footprint of hot-rolled coil even increases up to 3.0 kg CO2eq/kg hot-rolled coil. This underlines the importance of the availability of renewable energies.Graphical

Development of an Efficient Acid Pickling Bath for Hot-Rolled Steel Coil

Development of an Efficient Acid Pickling Bath for Hot-Rolled Steel Coil

A Hybrid Model of MEMD and PSO-LSSVR for Steel Price Forecasting

Herein, we propose a novel hybrid method for forecasting steel prices by modeling nonlinearity and time variations together to enhance forecasting adaptability. The multivariate empirical mode decomposition (MEMD)–ensemble-EMD (EEMD) approach was employed for preprocessing to separate the nonlinear and time variation components of a hot-rolled coil (HRC) price return series, and a particle swarm optimization (PSO)-based least squares support vector regression (LSSVR) approach and a generalized autoregressive conditional heteroskedasticity (GARCH) model were applied to capture the nonlinear and time variation characteristics of steel returns, respectively. The empirical results revealed that compared with the traditional models, the proposed hybrid method yields superior forecasting performance for HRC returns. The evidence also suggested that in capturing the price dynamics of HRC during the COVID-19 pandemic period, the asymmetric GARCH model with MEMD–LSSVR outperformed not only standard GARCH models but also the EEMD-LSSVR models. The proposed MEMD–LSSVR–GARCH model for steel price forecasting provides a useful decision support tool for steelmakers and consumers to evaluate steel price trends.

Production of hot-rolled coils in the casting and rolling complex of MMK Metalurji. Mastering experience, results achieved, prospects for further development

The article describes the practical experience of the foreign asset of the PJSC “Magnitogorsk Iron and Steel Works” - MMK Metalurji, consisting of a “hot” stage (casting and rolling complex (CRC) and a “cold” stage (cold rolling shop, hot-dip galvanizing unit, polymer coating line, metal service center) located at the production site in Iskanderun (Turkey). A brief technical description is given and the main parameters of the units used for the production of continuously cast slabs in the casting and rolling complex are given — an electric arc furnace (EAF), a ladle furnace (LF), a steel degassing unit (SDU) and a continuous casting machine (CCM), as well as advantages and disadvantages of the used concept of mini-mills. Two periods of CRC operation are described: during the starting and mastering of new units and technology (2011–2012), and from July 2021, when the complex was re-commissioned after a long period of conservation. The last part of the article indicates the actual parameters achieved for the period June-September in terms of chemical composition, assortment, standard sizes and productivity. Additionally, information is presented on the content of harmful elements and gas saturation of steel, as well as an assessment of the evolution of macrostructure defects on templates.

Sustainable transition of the primary steel production: Carbon footprint studies of hot-rolled coil according to ISO 14067

A shift away from traditional carbon-based towards a hydrogen-based steel production has to be stepwise so that technological challenges can be solved simultaneously to various other challenges like the evolution of green markets, political framework as well as the creation of hydrogen supply. First bridge technologies towards hydrogen-based steelmaking are crucial to generate a stable demand for hydrogen so that hydrogen supply can follow. Injection of hydrogen into existing blast furnaces is a prominent example to reduce greenhouse-gas emissions without the ambition to reach complete carbon neutrality. A subsequent next step on the way towards climate neutrality are modern Direct reduction units. This technology is able to reduce Iron oxides by natural gas and hydrogen, respectively. Within the existing plants Direct reduction units can be incorporated in various ways over time, thus offering a gradual and in the end complete transition to hydrogen and electricity based production. Since LCA studies provide crucial input for political and market-economy decision-making, the LCA community is of great importance for giving direction of transformation processes. Like other industries, the steel industry needs an allocation approach for greenhouse gas emission savings to evolve green markets, of which the methodology shall be discussed within the life cycle community. The current study presents carbon footprint assessments (ISO 14067) of hot-rolled coil for different future production scenarios. The following production routes are investigated: - Conventional blast furnace – basic oxygen furnace route - Injection of H2 into a blast furnace - Input of H2-based direct reduced iron (DRI) into a blast furnace - H2-based direct reduction combined with electrically melting from renewable energy.

Influence of strip non-flatness on the coil stress-strain state

Reducing the specific consumption of raw materials and materials in rolling shops is always an urgent task. Therefore, it is also important to improve the mathematical apparatus, which is a tool for optimizing technology in rolling shops. Most of the time, the metal in the rolling mills is coiled. Moreover, the coil is a complex object. The coil shape is maintained due to non-linear contact stresses distributed over the thickness and width, arising during the winding process. At the same time, the processes taking place in the metal do not stop with its winding into coil. First, stress relaxation occurs and the strip is deformed due to the creep effect. This is most important for cooling hot rolled coils and processing in bell furnaces due to the high temperature. In coils in a cold state, the processes of shaping do not proceed, but the roll may lose stability. This can lead to defects in the shape of the roll such as “birdie” or “settled coil”. Considering the above, modeling the stress-strain state of a coil is an urgent task. This article presents a mathematical model of the stress-strain state of the coil, taking into account the combined effect of non-flatness, roughness and gage thickness variation of the strip. The influence of the nonflatness of the coiled strip on the stress-strain state of the coil is considered in detail. The characteristic distribution of radial and tangential stresses in the roll after removing the roll from the drum is shown for various variants of the initial non-flatness. Taking into account the non-planarity in the mathematical model of the stress-strain state of the coil provides important advantages. First, to improve the accuracy of mathematical models for changing the shape of a strip in a roll. Secondly, to determine the critical values of the non-flatness of the strip, leading to the loss of stability of the coil.

Carbon footprint of scenarios towards climate-neutral steel according to ISO 14067

Within this paper, new findings of the potential of four considered intermediate solutions towards a primary climate-neutral steel production are reported. (1) Injection of natural gas into a blast furnace, (2) injection of hydrogen into a blast furnace, (3) natural gas-based direct reduction with subsequent input of the hot briquetted iron (HBI) in a blast furnace, and (4) hydrogen-based direct reduction with subsequent input of the hot briquetted iron in a blast furnace.The current study is a carbon footprint assessment applied to the product hot-rolled coil (HRC) according to the ISO norm 14067:2019. A cradle to gate approach is used including the production of raw materials to the production of hot-rolled coil. To define a reference point, a carbon footprint of hot-rolled coil produced via a typical blast furnace – basic oxygen furnace (BF-BOF) route is presented. The basic data set is based on primary data from the integrated site of thyssenkrupp Steel Europe AG (tkSE), year 2018. Within a novel approach, this base line is enhanced by integrating metallurgical models from the literature. Thereby all changes of the complex material and energy supply chain of an integrated site and of the upstream chain are reported. The carbon footprint of each process unit is presented in detail so that optimization potentials are identified, which impacts are analysed within a sensitivity analysis. A holistic comparison of using hydrogen in a blast furnace to using hydrogen in a direct reduction plant is presented and delivers important findings. This can help steel producers to maximize the efficiency of hydrogen use.Since the focus of this paper lies on the comparison of steel production routes and the assessments for all considered scenarios are based on the same methodologies and databases the sensitivity of made assumptions on the deltas between these scenarios is much weakened than the sensitivity of absolute values. That's one of the reasons why, the conclusions of this paper, which are referred to the plant of tkSE, can be transferred to other production sites, as well. The presented results can help decision-makers to know the potentials of possible intermediate solutions towards a climate-neutral steel production and how the potentials can be maximized.The carbon footprint of the product hot-rolled coil is 2.1 t CO2eq/tHRC following the recycled content approach and 0.82 t CO2eq/tHRC following the end-of-life recycling approach. The reduction potential for the carbon footprint is about 4 % for injecting natural gas into a blast furnace and about 9 % for injecting hydrogen into a blast furnace. The hydrogen is produced via electrolysis driven by a renewable German energy mix, year 2018. Using hot briquetted iron (HBI) within a blast furnace leads to a reduction potential between 5 % and 12 % for natural gas based-HBI and between 10 % and 17 % for H2-based HBI. The reduction potential strongly depends on the iron feedstock, which is replaced by the hot briquetted iron. Between 4.5 and 7.0 kg CO2eq/kg H2 are avoided by injecting hydrogen into a blast furnace, and about 5.4 kg CO2eq/kg H2 are prevented if the hydrogen is injected into a direct reduction plant.

Commodity markets intervention: Consequences of speculation, and informed trading

The Chinese regulatory authority's interventions into the futures market for steel during 2016 provide a rare opportunity to study the unintended consequences of interventions. Although hot rolled coil (HRC) and rebar are products with nearly identical components, their futures contracts trade separately. The regulatory authority intervened into the futures market for rebar but refrained from doing so for HRC. We document impacts of interventions measured by increased volatility, trading volume, and spreads in rebar markets. There is also evidence of informed trading in both markets, reflected by abnormally high trading volumes and low open interests occurring the day before the announcement of interventions.