Faisal Qayyum, Technische Universität Bergakademie Freiberg, Germany

Co-Author:
Ulrich Prahl, Technische Universität Bergakademie Freiberg
Seigfried Schmauder, University of Stuttgart
Sergey Guk, Technische Universität Bergakademie Freiberg
Ali Cheloee Darabi, University of Stuttgart

Abstract:
This study aims to investigate the effect of chromium and molybdenum on the formation of pearlitic microstructure in 1% carbon steels. To obtain experimental data, 12mm wires of one benchmark (Fe-1C) and two trial alloys (Fe-1C-1.5Cr and Fe-1C 1.5Mo) are manufactured in-house by casting and hot caliber rolling. These wires are homogenized at a temperature of 1200°C for a holding time of 12 hours. MatCalc and JMatPro software are used to identify the time-temperature and transformation curves for each alloying system. The effects of transformation times and holding temperatures on the pearlite morphology in each alloying system are systematically analyzed and compared by examining the resulting microstructures under an electron microscope. The microstructural features such as lamella length, lamella thickness and inter-lamella spacing for each case are quantitatively analyzed by post-processing the image data using FiJi-ImageJ and Python scripts. The probability and cumulative distribution plots of the microstructural features allow for the comparison and selection of optimal process routes for obtaining similar pearlitic microstructures across all alloying systems. Furthermore, a phase field simulation is performed to find an optimized heat treatment. The accuracy of the phase field models is validated through experiments. The heat treatment routine for pearlite formation in all three steels is simulated using the MICRESS software and the resulting microstructures are compared with the experimental results. To reduce computational cost, the heat treatment simulations are started from the fully austenitic microstructure and the morphology for this condition is calculated using MatCalc software. The pearlite formation heat treatment is simulated and the thermodynamic parameters are extracted using MatCalc software and literature. With the validated models, microstructures under different heat-treatment processes can be predicted and an optimized heat-treatment condition for all three materials can be obtained.

Niklas Fehlemann, RWTH Aachen University, Germany

Co-Author:
David Lenz, RWTH Aachen University
Yannik Sparrer, RWTH Aachen University
Markus Könemann, RWTH Aachen University
Sebastian Münstermann, RWTH Aachen University

Abstract:
High-strength structural steels (from 960 MPa upwards) are becoming increasingly important in modern steel construction applications. These steel grades are particularly suitable for reducing sheet thicknesses of components and thus enabling more sustainable construction. The low-temperature properties are also of great importance, and a profound understanding is necessary in order to exclude the risk for catastrophic failure due to cleavage fracture in the component design. In this study, the low-temperature properties of a structural steel of type S960 were investigated. For this purpose, specimens of different stress states (including shear, plane strain and notched round bar) were quasi-static tested in a bath of liquid nitrogen at -196°C. The resulting properties were analyzed in terms of ductility and strength and compared with the same properties at room temperature. For this purpose, a failure locus based on stress triaxiality and lode angle parameter and equivalent plastic strain was fitted to the data. In addition, the critical cleavage fracture stress of the material is identified. The probabilistic nature of the low-temperature properties was captured using a cumulative Weibull distribution so that a locus for different failure probabilities can be determined. The results show a pronounced dependence on the stress state, which is more pronounced at cryogenic temperatures than at room temperature. In the last step, a comparison was made with a high strength a pipeline steel. Comparable tendencies were found at room temperature, but a clearly different behavior at low temperatures. This shows that the stress state dependence of the low-temperature failure properties is clearly material-dependent and large deviations can occur for different steel classes. These results can be used to calibrate damage mechanics simulation models, which can significantly accelerate efficient design of steel components for various applications.

Silke Klitschke, Fraunhofer Institute for Mechanics of Materials , Germany

Co-Author:
Andreas Trondl, Fraunhofer Institute for Mechanics of Materials
Florence Andrieux, Fraunhofer Institute for Mechanics of Materials
Dennis Revin, Fraunhofer Institute for Mechanics of Materials

Abstract:
AHSS are widely used in crashrelevant components of automotive structures. Because of their low ductility an accurate failure prediction is mandatory for this class of materials. Hence, in the past different complex failure models have been developed. The calibration of those failure models is usually based on experiments with defined stress states, partly at different strain rates. Though, there is still a lack of suitable experiments for the validation of those calibrated failure models from quasi-static up to crash relevant strain rates cover-ing different complex loading situations. These validation experiments should be suitable for a wide range of test speeds, lead to nearly plane stress states from compression/shear to multiaxial tension and should show characteristic damage. In this contribution experimental validation concepts were developed and applied to a DP1000 steel sheet and a ZStE 340 steel sheet. These validation experiments are appropriate for quasi-static and highspeed testing. The key of these validation tests is to develop specimens with different potential critical areas. De-pending on the failure behavior of the material, failure occurs in the shear or in the nearly plane strain re-gion. Especially the safety-critical negative strain rate effect concerning the shear failure strain of advanced high strength steel sheets can be validated by the proposed new material dependent shear-tensile validation test. The specimen geometries are designed depending on the ductility of the material and the manufactur-ing is performed without any joining procedure. Local failure initiation on the surface of the specimens is observed by highspeed video recording and verified by FE-simulations. With these experimental concepts the validation procedure of failure models can be performed cost-efficient and reliable over a wide range of stress states and strain rates. This leads to an improvement in failure prediction and utilization of the light-weight construction potential of AHSS sheets in automotive applications.

Vahid Javaheri, University of Oulu, Finland

Co-Author:
Jukka Kömi, University of Oulu
Saeed Sadeghpour, University of Oulu
Sakari Pallaspuro, University of Oulu

Abstract:
Abstract: Isothermal bainitic transformation below the Martensite start temperature (MS) has been reported in previous works [1,2]. The current study investigates the effect of bainite formation below the MS temperature where the athermal martensite formation is interrupted, on the final tensile properties. The studied material is a 0.4 (wt.%) carbon, low-alloy steel subjected to different thermal cycles in order to produce different fractions of martensite and bainite. Gleeble 3800 thermo-mechanical simulator machine was employed to perform all the cycles as well as to provide the dilatometric data. In the experiments, each sample was heated to the temperature of 850 °C at a rate of 50 °C/s and was held for the 30s. Then, the samples were quenched to a temperature between MS and MF followed by a subsequent isothermal holding in the MS–MF temperature window. A field emission scanning electron microscopy equipped with an electron back-scatter detector was used for microstructural characterization. The results showed that low-temperature bainite formation below the MS significantly improved the ductility of the samples although the strength decreased slightly. References: [1] S. Samanta, P. Biswas, S. Giri, S.B. Singh, S. Kundu, Formation of bainite below the M temperature: Kinetics and crystallography, Acta Mater. 105 (2016) 390–403. https://doi.org/10.1016/j.actamat.2015.12.027. [2] S.M.C. van Bohemen, M.J. Santofimia, J. Sietsma, Experimental evidence for bainite formation below Ms in Fe–0.66C, Scr. Mater. 58 (2008) 488–491. https://doi.org/10.1016/j.scriptamat.2007.10.045.

Renata Latypova, University of Oulu, Finland

Co-Author:
Jukka Komi, University of Oulu
Vahid Javaheri, University of Oulu

Abstract:
Abstract: This study investigates the effect of rapid tempering and cementite morphology on hydrogen permeation and diffusion in a medium carbon steel. Three materials were tested: (1) direct-quenched, (2) direct-quenched and rapid tempered at 420°C, and (3) direct-quenched and rapid tempered at 720°C. The results showed that rapid tempering at 420°C and 720°C led to a significant decrease in the dislocation density of studied materials compared to the direct-quenched sample. In addition, higher tempering temperature resulted in a higher fraction of cementite precipitation as well as a change in the cementite morphology from the continuous stick-like structure to a more fragmented, discontinued, and globular type. Electrochemically hydrogen permeation tests revealed that direct-quenched samples could reach the saturation level much faster than the other two tempered samples and also had the lowest diffusion coefficient. It means less trapping site to be occupied but stronger to hinder the hydrogen mobility. Direct-quenched and rapid tempered at 720 °C needed a relatively longer time to reach the saturation level but on the other hand, it showed the highest diffusion rate among all samples. Overall, this research highlights the morphology of cementite and dislocation density of the studied samples in the hydrogen permeation and diffusion properties which is very important when developing of hydrogen-resistant steels.

Vasile Danut Cojocaru, University Politehnica of Bucharest, Romania

Co-Author:
Elisabeta Mirela Cojocaru, University Politehnica of Bucharest
Nicoleta Zarnescu-Ivan, University Politehnica of Bucharest
Nicolae Serban, University Politehnica of Bucharest
Mariana Lucia Angelescu, University Politehnica of Bucharest

Abstract:
The influence of solution treatment duration on the microstructure and mechanical properties of a hot-rolled UNS S32750 / F53 / 1.4410 Super Duplex Stainless Steel (SDSS) alloy was investigated in this study. The UNS S32750 / F53 / 1.4410 SDSS alloy was thermomechanical (TM) processed by hot-rolling deformation at a temperature of 1100°C with a total deformation degree (total applied thickness reduction) of 70%, followed by a solution treatment. The solution treatment was performed at temperatures between 1080°C to 1180°C, in 20°C increments, with a fix treatment duration of 20min. The microstructure evolution during TM processing was investigated by XRD and SEM-EBSD techniques, while the mechanical properties by tensile and impact testing techniques. The following microstructural characteristics were analysed: constituent phases, weight fraction, grain-size and phase morphology. The mechanical behaviour was assessed through the following properties: absorbed energy, ultimate tensile strength, yield strength and, elongation to fracture. The performed solution treatments induced significant changes in relation to alloy's microstructure and showed a direct influence on the exhibited mechanical behaviour.

Elyas Ghafoori, Leibniz University of Hannover, Germany

Co-Author:
H. Dahaghin, University of Tehran
C. Diao, Cranfield University
N. Pichler, Empa, Swiss Federal Laboratories for Materials Science and Technology
L. Li, Empa, Swiss Federal Laboratories for Materials Science and Technology
M. Mohri, Empa, Swiss Federal Laboratories for Materials Science and Technology
J. Ding, Cranfield University
S. Ganguly, Cranfield University
S. Williams, Cranfield University

Abstract:
In this study, a directed energy deposition (DED) process called wire arc additive manufacturing (WAAM) is employed for the fatigue strengthening of damaged steel members. Three steel specimens with central cracks were tested under a high-cycle fatigue loading (HCF) regime: (1) the reference specimen; (2) the WAAM-repaired specimen with an as-deposited profile, and (3) the WAAM-repaired specimen machined to reduce stress concentration factors (SCF). The corresponding finite element (FE) simulation of the WAAM process was calibrated using static experimental results, which revealed the main mechanism. The process was found to introduce compressive residual stresses at the crack tip owing to the thermal contraction of the repair. The FE results also revealed that stress concentration exists at the root of the as-deposited WAAM; this stress concentration can be mitigated by machining the WAAM to a pyramid-like shape. The fractography analysis indicated that the cracks were initiated at the WAAM-steel interface, and microscopic observations revealed that the microcracks were arrested by the porosities in the melted interface. The results of this pioneering study suggest that WAAM repair is a promising technique for combating fatigue damage in steel structures.

Karsten Wandtke, Federal Institute of Materials Research and Testing, Germany

Co-Author:
Dirk Schroepfer, Federal Institute of Materials Research and Testing
Ronny Scharf-Wildenhain, University of Technology Chemnitz
André Haelsig, University of Technology Chemnitz
Arne Kromm, Federal Institute of Materials Research and Testing
Thomas Kannengiesser, Federal Institute of Materials Research and Testing
Jonas Hensel, University of Technology Chemnitz

Abstract:
High-strength steels offer great potential in weight-optimised modern steel structures. Additive manufacturing processes, such as Wire Arc Additive Manufacturing (WAAM), enable near-net-shape manufacturing of complex structures and more efficient manufacturing, offering significant savings in costs, time, and resources. Suitable filler materials for WAAM are already commercially available. However, the lack of knowledge or technical guidelines regarding welding residual stresses during manufacturing and operation in connection with cold cracking risk limit their industrial application significantly. In a project of BAM and TU Chemnitz, the influences and complex interactions of material, manufacturing process, design and processing steps on residual stress evolution are investigated. By developing process recommendations and a special cold cracking test, economic manufacturing, and stress-appropriate design of high-strength steel WAAM components are main objectives. The present study focuses on determining the influence of heat control (interpass temperature, heat input, cooling time) and the design aspects of the components on the hardness and residual stresses, which are analysed by X-ray diffraction. Defined reference specimens, i.e., hollow cuboids, are automatically welded with a special WAAM solid wire. The influences of wall length, wall thickness and wall height on the residual stresses are analysed. Geometric properties can be selectively adjusted by wire feed and welding speed but cannot be varied arbitrarily. This was addressed by adapted build-up strategies. The results indicate a significant influence of the heat control and the wall height on the residual stresses. The interpass temperature, wall thickness and wall length are not significant. These analyses allow recommendations for standards and manufacturing guidelines, enabling a safe and economic manufacturing of high-strength steel components.

Elyas Ghafoori, Leibniz University of Hannover, Germany

Co-Author:
N. Pichler, Empa, Swiss Federal Laboratories for Materials Science and Technology
L. Li, Empa, Swiss Federal Laboratories for Materials Science and Technology
C. Huang, Imperial College London
D. Ferrari, Empa, Swiss Federal Laboratories for Materials Science and Technology
E. Chatzi, ETH Zurich
L. Gardner, Imperial College London

Abstract:
Wire arc additive manufacturing (WAAM) is a metal 3D printing technique that is well recognised in the construction sector for its high efficiency, cost-effectiveness and flexibility in build scales. However, there remains a lack of fundamental data on the structural performance of WAAM elements, especially regarding their fatigue behaviour. A comprehensive experimental study into the fatigue behaviour of WAAM steel plates has therefore been undertaken and is reported herein. Following geometric, mechanical and microstructural characterisation, a series of WAAM coupons was tested under uniaxial high-cycle fatigue loading. A total of 75 fatigue tests on both as-built and machined coupons, covering various stress ranges and mean stress levels, have been conducted. The local stress concentrations in the as-built coupons, induced by their surface undulations, have also been studied by numerical simulations. The obtained fatigue test results were analysed using constant life diagrams (CLDs) and S-N (stress-life) diagrams, based on both nominal and local stresses. The CLDs revealed that the fatigue strength of the as-built WAAM steel was relatively insensitive to the different mean stress levels. The S-N diagrams showed that the surface undulations resulted in a reduction of about 35% in the fatigue endurance limit for the as-built material, relative to the machined material, and a reduction of about 60% in the fatigue life for a given stress level. The as-built and machined WAAM coupons were shown to exhibit similar fatigue behaviour to conventional steel butt welds and structural steel S355, respectively. Preliminary local stress-based and nominal stress-based S-N curves are also proposed for the WAAM steel.

Ronny Kühne, RWTH Aachen University, Germany

Co-Author:
Helen Bartsch, RWTH Aachen University
Markus Feldmann, RWTH Aachen University

Abstract:
Scope of this research is the fatigue resistance of additively manufactured steel plates with galvanized surfaces. First the manufacturing process via wire arc additive manufacturing (WAAM) and hot dip galvanizing (HDG) of the specimens is described. In order to determine the influence of HDG on the fatigue resistance next to fatigue tests itself investigations on the surface roughness, the condition of the zinc layer and quasi-static tension on galvanized and ungalvanized specimens are pointed out. Even though, statistically no influence of the zinc coating on the surface roughness has been obtained, the zinc coating influences the surface shape in local areas leading to a reduction in the fatigue resistance due to the unidirectional dentritic growth of the Zn-Fe phase.

Yu-Chiao Lu, KTH Royal Institute of Technology, Sweden

Co-Author:
Christopher Hulme, KTH Royal Institute of Technology
Leyla Koort, KTH Royal Institute of Technology
Viktoria Sutorius Trollbäck, KTH Royal Institute of Technology

Abstract:
Evaluation of non-metallic inclusions in Inconel 718 produced by conventional production and by additive manufacturing A. Karasev, V. Trollbäck, L. Koort, Ch. Hulme It is well known that non-metallic inclusions (NMIs), which are formed during steelmaking processes, can significantly effect on the final properties of steels and alloys. Therefore, it is important to investigate the inclusion characteristics (such as composition, morphology, size and number) in steels and alloys for comparison and optimization of production processes and improvement of product quality. This study focused on evaluation and comparison of main characteristics of NMIs in nickel-based alloy Inconel 718 produced by a conventional production route and by additive manufacturing. Since the common two-dimensional investigations of NMIs on polished metal samples has a number of shortcomings, three-dimensional investigations of NMIs on a film filter and on the metal sample surface after a soft electrolytic extraction were carried out by using scanning electron microscopy equipped with energy-dispersive spectroscopy. It was found, that most inclusions have similar compositions in both samples, However, significant differences were detected in the morphology, size ranges and numbers of the observed inclusions. For instance, the sizes of Nb,Ti-C carbides and Ti,Nb-N nitrides in metal sample produced by additive manufacturing are about 6 and 3 times smaller compared to the conventionally produced sample, respectively. Moreover, the number of inclusions observed in the additive manufactured sample is drastically larger than that in the conventionally produced sample. This is explained by the much higher solidification rate of metal melt in the additive manufacturing process. It was concluded that the electrolytic extraction method with subsequent investigations in the scanning electron microscope can help to determine some significant quantitative differences of NMI characteristics in Inconel 718 samples produced by different production methods. Key words: steelmaking, additive manufacturing, Inconel 718, non-metallic inclusions, electrolytic extraction.

Holger Behrens, SMS group, Germany

Co-Author:
Michael Brühl, Salzgitter Flachstahl GmbH
Oliver Meyer, Salzgitter Flachstahl GmbH

Abstract:
Salzgitter Flachstahl GmbH, Germany, successfully commissioned the new Continuous Galvanizing Line (CGL) FV 3 for the production of galvanized high strength steel coils. The new line plays an important role in SZFG’s strategy and secures regional employment. Galvanizing ultra high strength steels pays in on light weight construction and sustainability. We also increase the vertical range of manufacture in our product mix. The line is supplied by SMS group and is located in Salzgitter, Germany. On July 23rd 2022, the first galvanized prime coil was produced. Besides the design and production of the mechanical equipment as well as the complete electrics and automation package, the furnace and process technology was part of the supply scope of SMS group, except the laser welder. Each year, 500,000 tons of galvanized steel strips for automotive structural components, white goods and industrial applications will be produced. Among other sophisticated technologies, the DREVER annealing furnace allows higher annealing temperatures, followed by faster strip cooling and longer dwell times. The configuration of the line as a whole also fulfills the structural as well as technical requirements to implement further innovative material concepts for the future. The new hot dip line can handle higher strength steels and support enhanced formability, and consequently also more complex component geometries. The continuous galvanizing line is equipped with a DUMA-BANDZINK air-knife system that ensure an optimum setting of the coating thickness plus a high surface quality of the zinc coating applied. The strip movement is stabilized additionally by the integrated electro-magnetic strip stabilization system. The main themes for this paper are the current and future product capabilities and the target market. Furthermore, the paper will emphasize the line concept and the process technology.

Marcel Giese, Federal Institute of Materials Research and Testing, Germany

Co-Author:
Volker Wesling, Clausthal University of Technology
Thomas Kannengießer, Federal Institute of Materials Research and Testing
Dirk Schröpfer, Federal Institute of Materials Research and Testing
Kai Treutler, Clausthal University of Technology
Antonia Eissel, Clausthal University of Technology

Abstract:
The targets for reducing CO2 emissions are closely linked to the development of highly efficient and economical steel components in plant, process and power plant technology, which require wear protection coatings tailored to the application and steel material for high combined corrosive, tribological, thermal and mechanical stresses. In addition to increasing demands to replace conventional cobalt alloys with nickel alloys as a result of price and supply risks, there is a growing demand in industry for defined functional surfaces of high quality for these coatings. Milling is a standard process for finish machining. The desired properties of wear resistant alloys imply significant challenges for the milling process due to high tool wear and surface defects. Besides the hardness of the coating materials, especially due to the precipitations, inhomogeneous, anisotropic weld structures of the claddings lead to further deteriorations of milling processes due to unstable milling conditions and process forces. A joint project of BAM and ISAF of TU Clausthal (Fosta P1550/IGF 21959 N) investigates the optimization of these challenging machining conditions by means of alloy modifications of the welding powder for plasma transferred arc cladding, without reducing the wear protection potential and using ultrasonic assisted milling process. In this paper, the influence of the microstructure and precipitation morphology adjusted by means of alloy modification on machining is investigated. The alloy used is a NiCrMoSiFeB alloy (trade name: Colmonoy 56 PTA). Through metallurgical investigations and in-situ measurement of cutting forces and temperatures at the cutting edge during the milling process as well as the subsequent investigation of tool wear and surface integrity, a detailed analysis and correlation between microstructural properties and machinability is feasible. The findings allow recommendations for standards and processing guidelines, enabling safe and economical production of highly stressed steel components with non-critical, cost-reduced materials.

Michel Boyer, John Cockerill, Belgium

Co-Author:
Nauwfel Amimi, ArcelorMittal Liège Jemeppe
Lionel Goiset, john Cockerill
Sergio Pace, Centre de Recherches Métallurgiques
Eric Silberberg, Centre de Recherches Métallurgiques

Abstract:
In 2016, the ArcelorMittal Group became the first steelmaker to industrialize the vacuum deposition technology to galvanize steel strip. Known under the name of "Jet Vapour Deposition (JVD)", this new type of zinc coating technology in which a zinc vapor is continuously deposited onto a steel strip in a vacuum chamber. Compared to Electro-Galvanizing (EG) and Hot-Dip Galvanizing (HDG), the JVD technology allows to apply with high productivity single-side, as well as double-sided coatings with zinc thicknesses that can differentiate from one side of the steel to the other. Circumventing the major constraints of these conventional coating processes, the JVD technology allows for the optimal coating of Advanced High Strength Steels (AHSS). As such, the JVD technology prevents the hydrogen embrittlement identified as a major drawback of the EG process for the coating of AHSS. Additionally, the JVD technology also overcomes the negative influence of steel surface oxidation when using the HDG process for the coating of certain types of AHSS Today, after 6 years of production, the industrialization of the JVD steel coating line is a success. At the end of 2022, the JVD line produced over 800,000 tons of galvanized steel strip. To address all industrial constraints and make the JVD technology a high-speed deposition line exceeding the present limit of 200 m/min set by conventional EG & HDG lines due to physical limitations, numerous developments were necessary. An overview of these developments will be presented during the lecture, as well as the deployment of the JVD technology to other steelmakers worldwide through license agreements proposed by John Cockerill. Keywords Vacuum evaporation, Jet Vapour Deposition, automotive, industry, Zn coating, Advanced High Strength Steels, hydrogen, corrosion protection, environmentally friendly

Yakov Gordon, Hatch Ltd., Canada

Abstract:
Minimization of CO2 emissions required changes in reducing gas composition from mixture of CO and H2 to pure H2. Changes in properties of reducing gas leads to changes in process parameters, furnace productivity, consumption numbers and quality of product. Phenomenological analysis of furnace operation was performed to analyze furnace operation with H2 as pure reducing gas. Similarity numbers were evaluated and expected changes in furnace performance were estimated. Influence of lower grade pellets on furnace performance was also analyzed and potential furnace parameters were studied. These findings are used to consult DRI plants on expected changes in DRI furnace performance.

Richard Elliott, Hatch Ltd. , Canada

Co-Author:
Ian Cameron, Hatch Ltd.
Gino De Villa, Hatch Ltd.
Jeff Eastick, Hatch Ltd.
Julia Allard, Hatch Ltd.

Abstract:
Shaft furnace direct reduction technology has proliferated globally over the past half century and more than 100 modules are currently operating. Choosing where to build these furnaces has been generally straightforward: build where natural gas is inexpensive and abundant. The next generation of direct reduction modules faces a more complex choice. Net zero scenarios for the iron and steel industry call for doubling the number of installed modules in half the time it took to deploy the existing fleet. Many of these new facilities will eventually use hydrogen as a reductant and must consider how their location affects their ability to transition partially or completely to hydrogen, electrify heating, access a competitive global iron ore market, and respond to accelerating legislated and voluntary decarbonization drivers. A transition to hydrogen-based ironmaking also forces a discussion on where to produce the required green hydrogen. Producing the hydrogen locally requires abundant green energy and freshwater; transportation from other regions, by pipeline or liquid ammonia conversion, may struggle to economically supply the immense volumes of hydrogen required for ironmaking. So, if the goal is decarbonization of the steel industry, why not move iron instead? DRI is already an effective means of ‘virtually’ exporting natural gas, enabling movement of solid iron rather than liquified gas, and can serve a similar export function in a future hydrogen economy. This paper aims to provide guidance for assessing the complex and competing factors affecting the choice of location for the next generation of direct reduction modules. These factors will be analyzed on a global basis and used to highlight the most promising regions for producing natural gas-based DRI while enabling a transition to hydrogen-based ironmaking. This paper will also compare technical and economic aspects concerning the export of hydrogen-based DRI with the export of hydrogen energy carriers.

Jose Senra, Diproinduca Canada Limited, Canada

Co-Author:
Erick Bubniak, Diproinduca Canada Limited
Joel Morales, Tenova S.p.A.

Abstract:
To demonstrate the technical and operational feasibility of processing briquettes made from iron fines in a Direct Reduction HYL Plant (DRP). An industrial trial was conducted by loading the DRP HYL reactor with a mixture of Iron Ore Pellets and Recycled iron Briquettes (RiB) made of iron ore pellets fines and sludge from the settling ponds. The physical properties of the RiB before the reduction process allows for conventional handling with industrial equipment to be fed to the reactor. The quality of the reduced RiB in Metallization and Carbon content is superior to the quality of the DRI pellets. Reduced RiB shows a compressive strength similar to or superior to the DRI pellets processed with the current Iron Ore Pellets. The results of the Industrial Trial carried out at a Direct Reduction HYL Plant, have sufficient physical and metallurgical properties to demonstrate the technical feasibility of the RiB technology. This allows the recycling of the iron ore pellet fines and sludge from the settling ponds in the direct reduction plants by producing RiB and mixing them with the iron ore pellets.

Milena Amábilis Ribeiro Gomes, RHI Magnesita GmbH, Austria

Co-Author:
Lukas Konrad, RHI Magnesita GmbH
Antoine Ducastel, RHI Magnesita GmbH
Taco Janssen, RHI Magnesita GmbH

Abstract:
In the steelmaking industry, the largest share of CO2 emissions comes from the reduction of iron ore. A switch from the blast furnace (BF)/basic oxygen furnace (BOF) route to the direct reduced iron (DRI) process with natural gas followed by the electric arc furnace (EAF) already enables CO2 savings of up to 38%. However, in order to meet the mid- to long-term CO2 targets of the iron and steel industry, further measures are required. Most DRI plants are currently operating on natural gas, which results in approximately 60% hydrogen in the process gas. However, currently projects are underway to determine if DRI units can operate at hydrogen levels at or close to 100%, which could further reduce CO2 emissions by more than 80%. In this context, it is important to consider the impact of hydrogen on the refractory lining in the DRI shaft kiln. Previous studies have shown that hydrogen can permeate through refractories and reduce ceramic oxides under certain process conditions. Silica-containing materials are reported to be especially susceptible to hydrogen attack. However, a deeper understanding of corrosion mechanisms is still needed. This article presents the first results of modelling and experimental work carried out by RHI Magnesita on the impact of hydrogen on refractory systems. Investigations were conducted regarding the thermodynamics and kinetics of ceramic oxide reduction by hydrogen as well as the effect of hydrogen exposure on the microstructure and properties of refractories. This enables refractories to be identified that are suitable for lining a DRI shaft kiln where hydrogen is used as a reductant and supports the development of novel hydrogen-resistant refractory solutions.

Sangram Keshari Mohapatra, Calderys France, France

Abstract:
Direct reduction of iron technologies have proven to have lower CO2 footprint compared to the conventional blast furnace routes and are further moving towards higher hydrogen content in the reducing gas in order to minimize the direct CO2 emissions. High hydrogen concentration in the reducing gas may react with the refractory and change its texture, resulting in an alteration of chemical composition, thermal profile and affect the mechanical load bearing capacities of the refractory linings. This paper reviews the functional requirements of the refractory linings of a DRI reactor with higher percentage of H2 in the reducing gas and recommends optimum total solution, brick, monolithic and jointing products, based on the past experience and recent experimental studies.

Takero Adachi, KOBE STEEL, LTD. , Japan

Co-Author:
Johannes Schenk, Montanuniversität Leoben
Daniel Spreitzer, Montanuniversität Leoben

Abstract:
Fluidized bed reduction technology is one of the items in carbon neutral ironmaking because of its flexible gas input and no need for agglomeration which leads to environmental friendliness. In the case where fluidized bed reduction system is installed in an integrated steel plant, partial substitution of blast furnace ironmaking and CO2 reduction are achieved by using exhaust gas such as coke oven gas as reductant. Moreover, it helps operation of agglomeration process by using unsuitable types of ore that lowers agglomeration productivity. Hence, fluidized bed installation into steel plants is not only the possibility of hydrogen-based carbon neutral technology but also bridge technology in CO2 reduction road. A scheme of multiple fluidized bed system design for an integrated steel plant involved with mass- and heat-balance calculation has been established in former research. However, unique characteristics of ore such as dense structure or iron-bearing complex oxide formation disturb reduction reaction. Especially, the latter case is observed in using blast furnace grade ore for fluidized bed reactor. In this study, two countermeasures to increase reduction degree are proposed and evaluated experimentally. One is elimination of hematite to magnetite reduction stage to avoid structure densification. Cross sectional observation of the reduced sub-samples collected after each stage shows porous structure is formed by the countermeasure. The other is dividing first reactor into two to decrease gas oxidation degree in metallization stage. Thermodynamical study by FactSageTM reveals that required gas oxidation degree for reduction of iron-bearing complex oxide is quite low compared to reduction of pure wustite to metallic iron. These countermeasures provide increase of final reduction degree in fluidized bed reduction experiments using 160 mm inner diameter furnace.

Daniel Spreitzer, Primetals Technologies Austria, Austria

Co-Author:
Wolfinger Thomas, Primetals Technologies Austria

Abstract:
The idea of the HYFOR-process was born in 2016, as a new disruptive fluidized bed technology using directly fine-ore as solid feedstock and green or low-carbon hydrogen as reducing agent. With this concept the issue of sufficient gas permeability is not prevailing, as it is for conventional shaft-based direct reduction technologies and the blast furnace. Therefore, an agglomeration step, e.g., sintering or pelletizing, is not necessary before charging the input materials and thus costs (Capex and Opex) and CO2-emissions can be reduced. As an accompanying benefit of using ore fines, the highest iron yield due to dry dedusting and recycling of dust can be achieved. The use of green or low-carbon hydrogen as reducing agent assures the avoidance or significant reduction of CO2-emissions during the reduction step. As the only technology, iron ore concentrates (pellet feed) as main iron source with particle sizes of 100% <150 µm, without prior agglomeration of any type of iron ore (e.g., hematite, limonite, magnetite) from high quality to low quality can be processed. First tests in the year of 2016 at the reduction lab of the Chair of Ferrous Metallurgy at the Montanuniversitaet Leoben showed the proof-of-principle of the HYFOR-technology. After promising results of all the lab-scale test work, the design and engineering of the HYFOR pilot plant started by the end of 2018. After erection and commissioning in 2021, roughly 30 test campaigns were done including several modifications and improvements. The main objectives of the pilot plant are to verify the results obtained during the lab-scale investigations, to evaluate the performance of the mechanical equipment, and to provide basic data for the design for a future industrial application.

Anderson Agra, Tecnored Desenvolvimento Tecnológico S.A., Brazil

Co-Author:
Guilherme Gonçalves, Tecnored Desenvolvimento Tecnológico S.A
Manoel Gonçalves, Tecnored Desenvolvimento Tecnológico S.A
Ismael Flores, Federal University of Rio de Janeiro
Alex Campos, Tecnored Desenvolvimento Tecnológico S.A
Bruno Flores, Federal University of Rio Grande do Sul
Ronald Lopes, Tecnored Desenvolvimento Tecnológico S.A
Stephen Potter, Tecnored Desenvolvimento Tecnológico S.A

Abstract:
As an energy-intensive and waste-generating, the traditional iron and steelmaking industry is challenged to find pathways to meet climate change mitigation and sustainability demands from modern societies and governments. In this sense, the steel industry is trying to meet the challenge of a fully circular economy in a near future. The minimization of solid waste sent to landfill and the mitigation of CO2 emissions are seen as key points for the sector. Tecnored is a smelting reduction process for hot metal production based on self-reduction agglomerates (SR briquette), flexible to use iron-bearing and carbonaceous wastes from steel plants, such as sludges and dust in an efficient way. Due to the Tecnored compact design, the process can operate without coke, using a broad range of carbonaceous materials in agglomerated form (fuel briquette), allowing the technology to heavily rely on sustainable biomass-based fuels, promoting drastic CO2 reduction during hot metal production. The validation of the Tecnored process and its flexibility for raw materials has been done in the last 10 years through many campaigns in a 40 kta demonstration plant. Now the technology is being scaled up to the first commercial plant, which has its start-up schedule 2026 in Brazil. In this work, we present the basics of the technology when operating with residues, including the recycling performance during the last two campaigns in the demonstration plant. Also, an economic evaluation of crude steel production using Tecnored and a comparison with other potential routes for waste recycling. The objective of this publication is to highlight the role that Tecnored can play in the future to contribute to a sustainable low-carbon circular economy iron and steelmaking.