Horst Hill, Deutsche Edelstahlwerke Specialty Steel GmbH & Co. KG, Germany

Co-Author:
Frank van Soest, Deutsche Edelstahlwerke Specialty Steel GmbH & Co. KG
Hans-Günter Krull, Deutsche Edelstahlwerke Specialty Steel GmbH & Co. KG
Andreas Mohr, Deutsche Edelstahlwerke Specialty Steel GmbH & Co. KG

Abstract:
Additive manufacturing technologies like the laser powder bed fusion (LPBF) process are used in various industrial applications. The advantages like a possible complex shaped geometry or small lot sizes offers a high degree in freedom, for products as well as for research and development topics. But, in most cases materials with a low amount of carbon like the 1.4404 are used for LPBF. This material exhibits and easy processing with LPBF, but these kind of materials are not suitable for tooling applications. Tool steels like 1.2343 or 1.2344 offer a higher hardness and wear resistance, but the defect-free processing is complicated. And in addition, the small lot sizes of the different AM-processes are also a drawback for this technology. Especially regarding a scale-up to a mass-production with focus on tooling. Therefore, the aim of this paper is to identify chemical compositions that provides both: a good processing with LPBF and steel shop together with properties like wear resistance. This covers the whole life-time of a part, beginning from prototyping, to mass production and finally, spare-part production

Andreas Mohr, Deutsche Edelstahlwerke Specialty Steel GmbH & Co. KG, Germany

Co-Author:
Janosch Conrads, Deutsche Edelstahlwerke Specialty Steel GmbH & Co. KG
Karlheinz Hoeren, Deutsche Edelstahlwerke Specialty Steel GmbH & Co. KG
Horst Hill, Deutsche Edelstahlwerke Specialty Steel GmbH & Co. KG

Abstract:
Additive manufacturing offers the possibility of producing geometrically complex components that cannot be manufactured by conventional machining routes. Due to this advantage, additive manufacturing is already being used in many fields of application such as medical technology or aviation. In general tooling for example, additive manufacturing can be used to realize optimized cooling channels, which can increase the production rate. However, there is currently a lack of tool steels that can be processed crack-free via additive manufacturing. As a result of their good processability, maraging steels such as 1.2709 have established as tool steels for additive manufacturing. These steels however are free from carbides, which results in lower wear properties than typical carbon tool steels. In the present work, it is shown how the tool steel 1.2083 can be optimized for use in additive manufacturing by an adapted chemical composition. The developed alloy can be easily processed in the Laser Powder Bed Fusion process and offers a hardness of 53 HRC already in the as-built condition. Furthermore, the tempering behavior is identical to that of 1.2083. Thus it is possible to produce additively manufactured components with properties comparable to a conventional carbon tool steel in mold making.

Tobias Brune, SMS group, Germany

Co-Author:
Yannik Wilkens, SMS group
Peter Weiland, SMS group

Abstract:
SMS group supplies plant technology for the production of high-quality metal powder for Additive Manufacturing (AM) and other technologies. Cost-effective and high-quality powders will be one of the main drivers for the development of metal AM towards a sustainable industrial technology. By operating a gas atomization plant (VIGA - Vacuum Induction Gas Atomization) integrated in the SMS 3D-Test Center, the SMS group has optimized the classical powder production for the requirements in AM over the last years. In addition to conventional gas atomization plants, the SMS group, together with a customer, has developed another innovative powder production process. The conventional batch-wise process is transformed into a continuous process. The continuous powder production plant enables cost-effective and large-scale production of up to 4,000 tons per year. Compared to the traditional gas atomization process the capacity is increased by a multiple. Production costs for spherical, high-quality metal powders are significantly reduced. The increase in capacity results in enormous economies of scale. Set-up times, melting and cooling times are reduced. In the new process developed by SMS group, two Vacuum Induction Melting (VIM) furnaces continuously hold liquid melt, which is atomized successively through the nozzle. The nozzle can be exchanged during operation. Melting is done under vacuum to guarantee highest quality levels like in the conventional process. In addition to the VIM route, where pure scrap is used as feedstock, the new process can also work with an existing liquid material supply. A metallurgical route with basic scrap as feedstock is also possible.

Miriam Laubrock, Fachhochschule Münster, Germany

Abstract:
One essential criterion for the design of joints in many applications is the fatigue behaviour with a coincident focus on lightweight design. In this case an increase of load cycles by the use of high strength steels in combination with welding is limited. Experiences from sectors like automotive engineering show, that bonded joints exhibit excellent behaviour under cyclic loads. Nevertheless, there is only a low use of adhesive bonding in sectors like agricultural engineering, commercial vehicles or plant engineering. One important reason for that is mainly a lack of regulations and standards, as they already exist for the design of welded joints. Typical standards used are for example IIW-guidelines, the Eurocode or the FKM-guideline. They allow the determination of Woehler curves for welded joints, while a design method for adhesive joints is not included. In addition to that, the boundary conditions in these sectors are different to those seen in automotive engineering. They can be characterized by a lot of small and medium sized companies using a large proportion of manual manufacturing methods. Further differences arise from the wall thickness of the steel sheets used, tolerances and the corrosive conditions caused by the respective environment. In order to fill this gap, a design method for load-bearing adhesive joints in applications using thicker steel sheets was developed according to the FKM-guideline. The method is based on only few input variables to create a Woehler curve and to estimate the operational stability of an adhesive joint as it can be used in the sectors mentioned.

Maxime Monnoyer, Fives Keods, France

Co-Author:
Stéphane Mehrain, Fives Stein
David Barbier, Fives Keods

Abstract:
UHSS and 3rd generation AHSS remain the best cost-effective solution for lightweighting of Automotive body in white applications, providing excellent combination of strength and formability. These steel grades are developed and processed in order to obtain multiphase microstructures with a substantial amount of retained austenite in order to achieve best possible ductility and in-use properties. Their processing imposes some constraints compared to conventional steels among which increased alloying contents, increased soaking temperatures, higher cooling rates, coatability and operational flexibility limitations. Such metallurgical and operational challenges can now be overcome thanks to key, newly developed, technologies whose advantages and features will be further presented. Induction technologies (Transverse and Longitudinal flux) allow rapid heating over a large temperature range as requested for the management of multiphase materials, thus avoiding the implementation and management of long conventional heating sections. Moreover, they allow efficient strip re-heating in the case of complex annealing cycles such as for example Q&P concepts. Application of wet cooling technologies achieve several objectives: first, high cooling rates enable managing all the product dimensional ranges without changing the metallurgical recipe whatever the strip thickness. Also, they allow fast and continuous cooling rate between high temperature soaking down to low quenching temperature as required by 3rd generation AHSS metallurgical concepts. Moreover, newly developed wet quenching technologies allow UHSS strip coatability even with high amount of Mn and Si. Overall, it can be demonstrated that new processing technologies dedicated to 3rd generation AHSS allow leaner metallurgical concepts and present high potential for cost and quality improvements.

Hans-Günter Krull, Deutsche Edelstahlwerke Specialty Steel GmbH & Co. KG, Germany

Co-Author:
Jamila Adem, Ugitech SA
Frank van Soest, Deutsche Edelstahlwerke Specialty Steel GmbH & Co. KG
Clara Herrera, Deutsche Edelstahlwerke Specialty Steel GmbH & Co. KG

Abstract:
The number of steel grades used for high pressure componentsis in a hydrogen environment is very limited. The effect on Hydrogen on the mechanical properties of steels are shown. An overview of the RRA values (relative reduction of area) of stainless and engineering steel grades will be presented and recomandation for grades regading cost and mechanical properties are given.

Alexander Gramlich, RWTH Aachen University, Germany

Co-Author:
Hauke Springer, RWTH Aachen University
Ulrich Krupp, RWTH Aachen University

Abstract:
The steel industry is a major contributor to global carbon emissions, with the production process being energy-intensive and relying heavily on fossil fuels. It is therefore crucial to find ways to reduce the carbon footprint of the industry in order to mitigate its impact on the environment. One such method is through scrap recycling, where existing steel products are reused instead of producing new steel from raw materials, saving on energy and resources. However, pronounced material integration and multi-material use in technical products lead to a contamination of steel scrap. Some of these contaminations cannot be economically removed during remelting and refining in the electric arc furnace and therefore, a gradual accumulation of detrimental impurities, like Cu or Sn, causes a deterioration of quality. Accordingly, the respective recycling steel grades are not sufficient to fulfil the demanding specifications of flat products, e.g. in the packaging or automotive industry. Strong segregations at the prior austenite grain boundaries leads to the problem of hot shortness, i.e., massive embrittlement of hot-formed steel products. Therefore, a need for the investigation of the influence of elements like Cu on the properties and processability of different steel grades exists and new approaches for tolerating higher Cu concentrations must be developed. The study presents the effects of adding 0.5% and 1.0% copper to reference alloy 42CrMo4 on its transformation behavior and mechanical properties. To investigated the risk of Cu-embrittlement, hot tensile tests were performed. Microstructures are investigated with light optical, scanning electron, and transmission electron microscopy. The results show that copper contamination, which is unavoidable in steel recycling, has the potential to increase the hardness and strength of high strength steels, if it can be controlled during the processing.

Rabi Lahdo, Laser Zentrum Hannover e.V., Germany

Co-Author:
Stefan Kaierle, Laser Zentrum Hannover e.V.
Frank Riedel, Fraunhofer Institute for Machine Tools and Forming Technology
Markus Puschmann, Fraunhofer Institute for Machine Tools and Forming Technology
Patrick Urbanek, Fraunhofer Institute for Machine Tools and Forming Technology
Jörg Hermsdorf, Laser Zentrum Hannover e.V.
Sarah Nothdurft, Laser Zentrum Hannover e.V.

Abstract:
Duplex stainless steels are utilized for many applications in oil, gas and hydrogen industry due to their excellent properties regarding strength, toughness and corrosion resistance. This outstanding performance is realized owing to a two-phase micro-structure of ferrite and austenite with a portion of at least of 30 % austenite. During welding, this microstructure ratio can be lost because of unfavorable heat input. Arc welding processes have become established in practice for welding duplex steels. These welding processes can produce joints with the required microstructure ratio, but the productivity is low. Beam welding processes exhibit high productivity, however cannot produce welded joints with the required microstructure ratio. Laser beam-submerged arc hybrid welding combines the advantages of both welding processes and can be a good alternative with high productivity. In this study, laser beam-submerged arc hybrid welding processes are developed for butt joints of duplex stainless steel S31803 with different thicknesses of 16 mm, 20 mm and 30 mm using a disc laser beam source with a max. output power of PL = 16 kW. In this context, the parameters laser beam power, welding speed, wobble amplitude and the edge preparation are investigated to achieve a good weld appearance, 30 % austenite content and an impact energy of at least of 40 J at a test temperature of −40 °C. By means of visual inspections, metallographic analysis and Charpy impact tests, it can be proven that the weld seams meet these requirements. As results, efficient high-performance welding processes with welding speeds of up to vS = 1.0 m/min are achievable. Based on these results, laser beam-submerged arc hybrid welding has been shown to be a welding method with high productivity, which can play an important role in the future for the welding production of duplex steel parts.

Maximilian Nagel, thyssenkrupp Hohenlimburg GmbH, Germany

Co-Author:
André Matusczyk, thyssenkrupp Hohenlimburg GmbH
Henrike Bröker, thyssenkrupp Hohenlimburg GmbH
Andreas Tomitz, thyssenkrupp Hohenlimburg GmbH
Max Müntefering, thyssenkrupp Hohenlimburg GmbH
Gerhard Gevelmann, thyssenkrupp Hohenlimburg GmbH
Marisa Taube-Levermann, thyssenkrupp Hohenlimburg GmbH
Stephan Kovacs, thyssenkrupp Hohenlimburg GmbH

Abstract:
Modern applications demand high formability due to increased complexity in part designs. Conventional microalloyed steels are often limited in this respect. The new High Ductility (HD) grades solve that issue. In yield strength ranges from 315 up to 700 MPa, their outstanding local forming reserves enable a reliable production process even for components that require complex forming operations. Especially in the automotive industry easy to weld materials for lightweight applications – with higher strength levels and lower sheet thicknesses – have become more and more important in the recent years. The HD grades fulfill all normative requirements of the EN 10149 and VDA 239-100 respectively and can be used to easily replace conventional HSLA steels. Beneficial for the medium strength grades is also their higher value in scrap commercialization due to specifically designed chemical compositions. All available hot-strip HD grades are fully characterized regarding their local formability, hole expansion ratio, bending radii and welding behavior. Narrow scatter bands in material properties allow a smooth production. With their quasi-single-phase ferritic matrix, they are already applied in automotive safety components and modern axle designs within electric vehicles.

Franz He, Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany

Co-Author:
Marion Merklein, Fraunhofer Institute for Manufacturing Technology and Advanced Materials

Abstract:
Energy conservation and overall vehicle efficiency has been steadily gaining importance in the automotive sector over the years, especially with the technological switch to electrically powered vehicles. Lightweight parts are therefore required to provide safety relevant components with reduced part weight for the automobile while at the same time not compromising in aspects of passenger security. Hot stamping has proven itself to be a suitable process for the generation of automotive components, which meet the contrary requirements by improving mechanical properties and thereby passenger safety while at the same time providing lowered part weight through reduced sheet thickness. Due to increased forming temperatures above 850 °C, the usage of lubricants is not yet viable for hot stamping. To prevent decarburization and scale formation an additional aluminium-silicon based coating is applied to the boron manganese base material. The lack of lubricant usage combined with the coating material results in occurrences of high friction and wear at high temperatures. Previous investigations have shown that process parameters exhibit a significant influence on friction and wear in the process. Furthermore, the workpiece sided austenitization parameters as well as coating thickness have proven to influence the layer formation in the coating layer. Within this study the influence of the initial coating thickness on the friction and wear behaviour as well as interdependencies with other significant parameters is investigated. To this end, strip drawing tests are performed with both coating strengths and analysed in regard to the resulting tribological behaviour. The results of this study help in improving the understanding of the tribological conditions within the hot stamping process and to develop tailored measures for reducing tool and part wear.

Alexander Gramlich, RWTH Aachen University, Germany

Co-Author:
Ulrich Krupp, RWTH Aachen University
Frederike Brasche, RWTH Aachen University

Abstract:
Press hardening of manganese-boron steels is one of the most efficient production processes for high strength automotive sheet components. However, the energy absorption capacity of these components is greatly limited by the formation of fully martensitic microstructure during in-die quenching. In order to extend the application range of press hardened components, the use of third-generation advanced high strength steels, especially medium manganese steels, achieves increasing attention. The alloying concept of these steels allows the critical cooling rate and the Ac3-temperature to be significantly lowered compared to manganese-boron steels, resulting in a lower austenitizing temperature and shorter cycle times. Aim of the presented research is to analyze the potential of press hardening of lean medium manganese steels with an integrated intercritical annealing or quenching & partitioning treatment. Therefore, different heat treatments were performed on Fe-0.3%C-5%Mn-1.5%Si and Fe-0.2%C-7%Mn-0.2%Si. By adjusting the heat treatment parameters, the microstructure and hence the mechanical properties can be modified to fit the application´s load requirements. The results demonstrate that both treatment strategies lead to complex multi-phase microstructures, which have been analyzed in detail by a combination of EBSD and EPMA. Optimization in heat treatment results not only in high tensile strength, comparable to martensitic 22MnB5, but also in significantly improved total elongation. Regarding the ductility, it was shown that besides the adjustment of a sufficient retained austenite content, the reduction of fresh martensite is indispensable to prevent brittle failure. Finally, selected heat treatments were reproduced in a laboratory-scale press hardening with temperature-controlled hat-shaped pressing tool.

Rico Haase, Fraunhofer Institute for Machine Tools and Forming Technology, Germany

Co-Author:
Matthias Nestler, Fraunhofer Institute for Machine Tools and Forming Technology
Julia Schönherr, Fraunhofer Institute for Machine Tools and Forming Technology
Verena Kräusel, Fraunhofer Institute for Machine Tools and Forming Technology

Abstract:
By press hardening of boron-manganese-alloyed steels, extraordinary strength can be achieved. Accordingly, the process is applied for different crash relevant components in the car body structure. Aiming for an outstanding energy dissipation, sections with lower ultimate strength to the benefit of an increased elongation are required. This can be achieved by a tailored tempering process, where the uniform heating and segmented cooling figured out to be the most appropriate process route on an industrial scale. Due to the non-uniform distribution of temperature during the quenching phase and the uneven level of thermal strains in the final cooling subsequent to the forming itself, a higher level of distortion was observed. Thus, a detailed understanding of the thermal effects and flux during the whole process chain is a key condition in order to achieve stable mechanical as well as geometrical properties. Within the recent research project gratefully supported by FOSTA, this detailed analysis of the thermal evolution of the different part sections of a tailor-tempered part were elaborated. By the repetitive crosscheck between process-integrated measurement and FEA prediction, the microstructural evolution and geometric accuracy were investigated. The relation between elastic spring back, thermal shrinkage and their interaction towards parts stress state and geometric deflection was examined. By the more detailed understanding of the underlying mechanisms, the route is opened for well-aimed compensation strategies. While the portion of press-hardened and in particular tailor-tempered components is established and stable in the car body structure, the ongoing development towards large-sized BIW-components such as the door ring concept come into the competition. This amplifies the relevance of the component accuracy and thus of the presented topic.

Manuel Schickbichler, Montanuniversität Leoben, Austria

Co-Author:
Martin Hafok, voestalpine Böhler Edelstahl GmbH & Co KG
Christoph Turk , voestalpine Böhler Edelstahl GmbH & Co KG
Gerald Schneeberger , voestalpine Böhler Edelstahl GmbH & Co KG
Andreas Fölzer, voestalpine Böhler Edelstahl GmbH & Co KG
Susanne Katharina Michelic, Montanuniversität Leoben

Abstract:
Tool steels produced by the powder metallurgy (PM) route are increasingly crucial in processing other materials. Considering the high demands on their mechanical properties, steel cleanness is an essential aspect. The overall cleanness in PM steels is already very high, making a reliable characterization challenging due to the rare appearance of non-metallic inclusions. However, a comprehensive characterization of non-metallic inclusions present in the steel matrix at different process steps is indispensable to improve steel performance further. This study analyzes the microscopic cleanness of a classic PM high-speed steel using manual and automated SEM/EDS measurements and chemical extractions. The size, number, morphology and chemical composition of the non-metallic inclusions are illustrated in detail. High Cycle Fatigue Tests (HCF) allow the determination of inclusions in the mesoscopic size range. Additionally, based on the data of automated SEM/EDS measurements, the maximum expected inclusion diameter in the samples is predicted using Generalized Pareto Distribution (GPD) – a statistical method of extreme value theory. The results of the various methods are compared. Combining these different approaches enables a clear description of the overall cleanness. A clear relation between the microscopic and the mesoscopic inclusion population in the investigated steel is observed, providing an essential basis for further process optimization.

Hans-Günter Krull, Deutsche Edelstahlwerke Specialty Steel GmbH & Co. KG, Germany

Co-Author:
Philipp Niederhofer, Deutsche Edelstahlwerke Specialty Steel GmbH & Co. KG
Frank van Soest, Deutsche Edelstahlwerke Specialty Steel GmbH & Co. KG
Svenja Richert, Deutsche Edelstahlwerke Specialty Steel GmbH & Co. KG

Abstract:
Usually tool steels are used in quenched and tempered condition. Due to the phase transition from austenite to martensite and the volume change during the transformation controlling of distortion might be a challenge. The end user demands for high hardness of the final tool leads to a poor machinability. Engineering steels with bainitic structure are generally based due to economic reasons on a low alloying content, especially the carbon contend is rather low compared to tool steels. Bainitic steels require often a controlled cooling to get the desired micro structure and the maximum size to achieve a fully homogeneous bainitic structure is limited to dimension far below acceptable dimension of tool steels. A new developed steel with focusing on a bainitic structure even for bigger dimensions shows a lower hardness at ambient temperature then conventional hot-working tool steels but with a lower temperature dependency. Therefor at service temperature the mechanical properties are comparable to established grades. Heat treatment is simplified by a simple austenitization and cooling process without special requirement on the cooling rate. Due to a generally lower cooling rate and lower hardness compared to a Q&T process the risk of cracking is reduced. The abcence of a quench and tempering process in combination with low hardness at ambiant temperature whats good for machining leads a low CO2 foodprint of the process chain. With the combination of good weldability and rather low hardness after rapid cooling this grade can also processed in additive manufacturing and is well suited for a hybrid process of conventional and additive manufacturing.

Lennart Mirko Scholl, RWTH Aachen University, Germany

Co-Author:
Frederik Tegeder, RWTH Aachen University
Alexander Bezold, RWTH Aachen University
Christoph Broeckmann, RWTH Aachen University

Abstract:
Improving the service life of cold forming tools is of great economic interest nowadays since productivity and resource efficiency significantly depend on tool life. High-performance, carbide-rich PM tool steels are often used in these applications, where tool service life is mainly limited by wear resistance and fatigue strength. Since cold working tools are usually subjected to non-proportional, multiaxial cyclic loadings during operations, a fatigue-oriented component design is essential along with a fundamental understanding of fatigue mechanisms. Currently, there are no validated, material-specific approaches for carbide-rich tool steels that consider the non-proportional multiaxiality or provide suitable fatigue strength data. In this study, a new concept for tool design under multiaxial fatigue loading is developed and applied to an extruder screw and a twist drill. Various failure hypotheses such as the quadratic failure hypothesis (QFH), the FKM guideline hypothesis (FKM), the shear stress intensity hypothesis (SIH) or the normal stress hypothesis (NH) are investigated, and their accuracy is validated for the widely used PM tool steels AISI D2 (1.2379 / X153CrMoV12) and AISI M3 (1.3345 / HS6-5-3). Calculations are based on statistically validated uniaxial fatigue strengths (HCF, NG = 107) under axial and torsional loading, which are used in addition to the tensile strength for the construction of appropriate Haigh diagrams. For validation of the hypotheses, multiaxial fatigue tests are performed on a 2-axis hydraulic test rig to generate suitable multiaxial Wöhler diagrams. The results indicate that both QFH and FKM provide quite good predictions of multiaxial fatigue strengths and are suitable for a design concept. The SIH mostly achieves poorer accuracy. The largest errors mostly occur with the NH. Overall, QFH, FKM and SIH show potential for accuracy improvements, e.g. through adjusting the weighting factors or including more precise Haigh diagram curves.

Abdoulfatah Moustapha Houssein, Calderys Deutschland GmbH, Germany

Co-Author:
Pascal Hubert, Imerys Villach GmbH
Steffen Moehmel, Imerys Villach GmbH

Abstract:
The new climate and environmental challenges have made the iron making industry move towards a cleaner production and therefore to a greener refractories consumption. The blast furnace being the main vessel in the iron making process, its tapping mainly relies on the quality of the Taphole Clay (THC). For a long time, coal tar bonded Taphole Clays were used for their easy injection and good adhesion to taphole walls but their high toxicity led to the use of phenolic resins. Despite their lower toxicity level, these resins are recently presenting some health issues for the plant workers especially with their free-phenol content which sometimes may be present up to nearly 10% in the resins. In this study, two different resin binding systems: a conventional phenolic resin and a low free-phenol resin were examined and compared. On a first hand, the effects of these binding systems on general plastic behavior of the products were analyzed and also correlated to their physical and mechanical properties. A comprehensive understanding of the Taphole’s severe operating conditions such as high temperature, high pressure, corrosion by slag and molten pig iron is required. Therefore, the injectability of the studied samples was investigated at high temperature in order to characterize the setting of the material, the cracks formation and the outlet of volatiles during the plugging mechanism of the Taphole Clay in the blast furnace. A chemical analysis of the Polycyclic Aromatic Hydrocarbon (PAH) present in the samples was also performed.

Thierry Joly, Vesuvius Europe, France

Co-Author:
Mathieu Dombrowski, Vesuvius Sp. z o.o
Isenbarger Roger, Vesuvius

Abstract:
Taphole clay as a key element in the proper functioning of the ironmaking process as it protects the ceramic hearth over time from damage by pig iron or slag. Using poor quality clay can be detrimental and leading to higher costs and early maintenance of BF hearth. Markets needs for sustainable products were another important factor for this evolution. Development of a binder for taphole clays which does not contain Polycyclic Aromatic Hydrocarbon and Formaldehyde was a game changer in the industry that strives towards sustainable future, which is available worldwide with performance at least equivalent to standard product, allowing cure speed of the mass to be adjusted and short inter-cast times. However, in some rare cases, we observed a hardening of the taphole mass in the plugging machine - this phenomenon required further development. Performing analytics and tests to reduce this hardening phenomenon, correlated to the high temperature in the mud gun, by developing a binder-based Formaldehyde and PAH free-tech with a higher boiling temperature. By increasing the boiling temperature of the binder, we succeeded in shifting the setting of the binder to higher temperatures, which solved the hardening problem in a way that exceed our expectations. Our methodology includes study and field trail of the implemented approach with an objective to replace the binding system without changing the formulation of the taphole mix concluding that this evolution of the binder has a positive influence on the length of the tap hole, duration of the casting and the specific consumption of the taphole clay in grams per ton of hot metal. Application in the field shows increased performance relative to traditional binder systems and does not require any reworking of the THC formulation, it can be easily substituted currently supplied materials with positive impact on health & environment.

Youn-Bae Kang, Pohang University of Science and Technology , Korea, Republic of

Co-Author:
Michael Bernhard, Pohang University of Science and Technology
Kang-Ho Bang, POSCO
Soon-Jong Jung, POSCO

Abstract:
One of the industrial wastes after alumina production from bauxite, red mud, was assessed as an additive to lime, as a new desulfurization flux for the hot metal in the steelmaking process. Its role in facilitating the melting of the lime was primarily investigated. Keeping in mind that the desulphurization mechanism under mechanical stirring such as in the KR process is different from that without mechanical stirring, a series of laboratory scale tests were carried out with a device for inducing mechanical stirring in the hot metal. A number of variables (mixing ratio between lime and red mud, pre-reduction of red mud, mechanical stirring, and additives to the lime/red mud mixture) were employed in order to elucidate the desulphurization mechanism and optimum chemistry of the desulphurization flux. In order to assess the desulphurization efficiency in a more quantitative manner, a “DeS Index” was defined. This takes into account the extent, rate, and cost of the desulphurization simultaneously. With this index, it was found that the presently developed red mud-containing desulphurization flux showed almost similar desulphurization efficiency compared with those of commercially used desulphurization fluxes. It was even better than a typical lime/fluorspar mixed flux, which is now prohibited from being used in many companies due to its environmentally harmful character. It is emphasized that the desulfurization efficiency should be assessed under mechanical stirring in order to be used in the KR-type desulphurization process.

Daniel Cruz, TMT GmbH, Germany

Co-Author:
Volker Langer, TMT Tapping Measuring Technoloy GmbH
Claude Meisch, TMT Tapping Measuring Technology S.a.r.l

Abstract:
Casthouse and Digitalization appear to exclude each other at first sight. Especially considering application of Blast and Metallurgical Furnaces. Since more than 100 years they are acme of heavy industry, hard work and challenging environmental conditions. But how does digital evolution fit into it? It is driven on the requirements of better safety, reproducibility, predictability and documentation. Since more than 20 years, TMT Tapping Measuring Technology in Luxembourg and Siegen has developed with its customers and partners solutions for • Automation, • Visualization, • Data Management and • Virtualization, in order to meet above expectations. The usability for the user are remote commissioning, virtual training, asset performance management and significant stability and efficiency on the tapping process.

Fiona Meier, RWTH Aachen University, Germany

Co-Author:
Andreas Janz, Hüttenwerke Krupp Mannesmann GmbH
Alexander Babich, Independent Ironmaking Consultant
Dieter Senk, RWTH Aachen University
M. Efetürk, Hüttenwerke Krupp Mannesmann GmbH
R. Peter, Hüttenwerke Krupp Mannesmann GmbH

Abstract:
Effect of the co-injection of PC and coke oven gas on the raceway and shaft phenomena in a blast furnace Injection of coke oven gas (COG) containing about 60% of pure hydrogen and nearly 25% hydrocarbons, has a potential for lowering the CO2 emissions from a blast furnace (BF). Hüttenwerke Krupp Mannesmann (HKM) in Duisburg has commissioned a COG injection system to operate blast furnaces with injection of PC and COG via two lances in the tuyere. In order to optimise this technology, a theoretical and experimental study on the raceway conditions, coal conversion, as well as pellets and sinter reduction behaviour while injecting COG has been conducted at RWTH Aachen University. In this contribution, first, the analysis of the COG influence on the BF process parameters and the effect of tuyere and lance design on PC conversion were undertaken. Then, injection trials using the MIRI plant were performed with varying PC and COG amounts while keeping constant blast temperature and oxygen enrichment. Furthermore, COG was replaced with natural gas. The conversion degree is determined based on the offgas analysis. Coal residues are undergoing microscopical investigations. Next, isothermal reduction test of pellets and sinter at three temperatures (850, 1000 and 1150°C) under two gas compositions with different contents of CO, CO2, H2, H2O and N2 were conducted using a 3-zone tube furnace. Mass losses were measured continuously during the test and the reduction degree was determined. In addition, changes in material microstructure and morphology were analysed using a scanning electronic microscope combined with EDX.

Ricardo Sebastião Nadur Motta, Ternium, Brazil

Co-Author:
Deilton de Oliveira Sousa , Ternium
Beatriz Lopes, Ternium
Deyvid Martins de Souza, Ternium

Abstract:
This work aims to show the industrial development carried out to expand the PCI plant capacity of Ternium’s blast furnaces in Rio de Janeiro-Brazil. Ternium has got two blast furnaces with a daily production of 7500 thm each. The PCI plant's original design features have got two 60 t/h pulverized coal mills with two injection stations with dual vessels allowing average PCRs of up to a maximum of 180 kg/thm for each blast furnace. Over the years, the PCI plant has presented capacity and availability problems regarding the coal injection and grinding stations, affecting the plant's hot metal production and leading to losses due to the lack of coal and consequent instability in the operation of the blast furnaces. The PCI expansion improved the injection stations with the addition of a third injection vessel, a new coal silo of 800 tons and a third coal grinding mill and drying plant with the same type and grinding capacity and with alternative pneumatic transport increasing the versatility of the plant in general. In addition, dual coal lances were implemented with dynamic distributor and closed loops control allowing uniform distribution of coal between lances and higher PCR up to 220 kg/thm.

Colin Morrison, Primetals Technologies UK, United Kingdom

Co-Author:
Rainer Klock, thyssenkrupp AT.PRO tec GmbH
Bartosz Smaha, thyssenkrupp Steel Europe AG
Hauke Bartusch, VDEh-Betriebsforschungsinstitut GmbH
William (Ross) Edmond, Primetals Technologies Ltd.

Abstract:
"When operating a blast furnace, the ability to positively influence raceway characteristics and improve the permeability of the process, are key features that can enhance performance. The Sequence Impulse Process (SIP) is an oxygen pulsing technology credited with providing a way for blast furnaces to realise such benefits, at scale, today. This paper explains the technology and provides operational feedback from Schwelgern BF1, Germany operated by thyssenkrupp Steel AG. It discusses how regular injection of high energy SIP oxygen, has enabled a shift in operational outcomes. The total reducing agent rate and the carbon footprint have been lowered, as have heat loads to the tuyeres and shaft areas of the blast furnace. These compounded changes lead to significantly reduced OPEX and a rapid return on investment for the plant. Through the use of SIP, the performance improvements have been experienced even during periods of reduced burden material quality and have realised greatly enhanced stability characteristics in the blast furnace when compared to conventional operation. Raceway material analysis reveals improved conditions for metal/slag removal providing a mechanism for better drainage such that production level increases could also be considered. In utilising SIP, blast furnace operators now have a tool that provides flexibility to shift their operational drivers between gas utilisation, productivity and material use according to the requirements dictated by a multitude of influencing factors,"

Hauke Bartusch, VDEh-Betriebsforschungsinstitut GmbH, Germany

Co-Author:
Andreas Janz, Hüttenwerke Krupp Mannesmann GmbH
Fatima Demirci, Hüttenwerke Krupp Mannesmann GmbH
Thorsten Hauck, VDEh-Betriebsforschungsinstitut GmbH

Abstract:
Until 2030 the EU has the objective to decrease CO2 emissions by 55%. The steel industry plans to reach substantial emission reductions by shifting to new steel production process routes like direct reduction combined with electric melting – but those process routes require availability of hydrogen, or in the first step natural gas in huge amounts and at competitive prices. However, currently the energy crisis decreases the economic feasibility of those new process routes. Consequently, it is reasonable to think about fast feasible bridge technologies to enable maximum CO2 mitigation in current blast furnace based process routes. One such bridge technology, already followed by multiple steel producers, is increasing the ore reduction share by hydrogen in the blast furnace. Higher hydrogen concentrations in the reducing gas lead to a shift between direct and indirect reduction, but also influence the process gas density and viscosity. Especially in Europe there is only little experience on blast furnace operations points with such higher hydrogen loads. HKM already announced to increase the hydrogen content in their blast furnaces by injection of coke oven gas. To prepare this operation, a study was executed comparing several historical operation periods at HKM with mixed natural gas and coal injection to similar periods with coal only operation. This study comprises analysis of differences in data distributions for nearly all data series from a blast furnace often used to rate the furnace working state. This article presents the differences found e.g. for the top gas properties, stack wall pressure and temperature measurements as well as other operational parameters to work out the changes in blast furnace working states with a higher hydrogen reduction share.

Fabian Perret, Hüttenwerke Krupp Mannesmann GmbH, Germany

Co-Author:
Alexander Babich, Independent Ironmaking Consultant
Dieter Senk , RWTH Aachen University

Abstract:
It is almost impossible for the injected pulverised coal (PC) to be completely converted in the raceway at very high PC injection rates (≥ 200 kg/tHM). Therefore, it is crucial to understand whether the unburnt coal particles (Char) can be converted outside the raceway and, if so, to what extent. The incomplete coal combustion in the raceway leads to a decrease in the blast furnace (BF) productivity and operation efficiency and increases the specific coke rate. RWTH Aachen University intensively studies the properties, the behaviour, and the interaction of char with coke, iron burden, liquids, and gases outside the raceway. This contribution focuses on the fluid dynamics of gas-liquid flow in the dripping zone as well as the char effect on liquid products (hot metal and slag). To investigate these effects, an experimental BF dripping zone setup with ignited coke was developed. Several experiments including a reference test without injection were conducted with variable parameters such as the injected material (char, PC, coke fines), the injection rate, the hot metal temperature, the coke size, and the coke bed height. Thus, it was possible to evaluate the effect of these parameters on char behaviour as well as on static and dynamic holdups. In addition, the char effect of slag properties such as viscosity, basicity and melting range was examined using the simulation software FactSage™ and was afterwards compared with experimental measurements. These experiments and simulations are helpful for BF process monitoring and control as well as further prediction of char behaviour in the BF.

Edward Long, Primetals Technologies UK, United Kingdom

Co-Author:
Richard Harvey, Primetals Technologies UK
David Osborne, Primetals Technologies UK

Abstract:
"Blast furnace stave design robustness has significant impact on the longevity of secure, reliable blast furnace operations. Blast furnaces are forecast to be in operation for years to come, but ultimately will be replaced by alternative steelmaking routes. A likely impact for blast furnace operators is to extend campaigns. Short interim repairs will become the norm, with major rebuilds and relines (which can take many months) becoming less common. The purpose of the stave cooling system is to preserve blast furnace shell integrity making it suitable for many campaigns without change. Consequently, it is imperative to avoid premature failure. Copper and cast iron staves have been shown to bend, due to thermal effects of hot and cold sides, resulting in pipe connection failures and water leaks into the furnace. Additionally copper staves have experienced excessive wear as a result of cold abrasive materials being present at the furnace walls. These problems became well known in the early 2000’s. Primetals Technologies studied these phenomena and developed patented solutions to prevent bending in the critical area of the staves, as well as using abrasion resistant, hot face inserts. These retain burden material & whilst allowing freezing of soft, melting materials and create a wear barrier. Results from regular monitoring of current wear-resistant installations have validated the continued presence of the wear-resistant solutions and demonstrate the potential for many decades of copper cooling staves life. Additionally the data reveals that copper staves with wear-resistant solutions retain more stable and lower heat loads through the range of operating conditions. The conclusion from this is that an additional benefit of fuel saving can be realised. "

Afshin Sadri, Hatch Ltd. , Canada

Co-Author:
Jesson Ma, Hatch Ltd.
Wai Lai Ying, Hatch Ltd.
Sun Ya Ping, Heibei JinXi Iron & Steel Group Co., Ltd
Li Jian Wei, Heibei JinXi Iron & Steel Group Co., Ltd

Abstract:
The wear and erosion of the refractory lining and cooling elements in blast furnaces are the main reason for the termination of their campaign life. This paper presents the results of combined AU-E inspection and thermal analysis of refractory lining in blast furnace #9 at the JinXi steel plant in Tangshan, China. In June 2019, BF#9 was relined and allowed us to compare the AU-E inspection results with actual physical refractory thickness measurements. This comparison helps us understand the strengths and weaknesses of indirect methods utilized to monitor blast furnace hearths' refractory condition.

Christof Dratner, cunova GmbH, Germany

Co-Author:
Hebel Rudolf, FKM Engineering
Jürgen Hochhaus, AG der Dillinger Hüttenwerke
Jörg Hunger, ArcelorMittal Eisenhüttenstadt

Abstract:
Significant campaign life extensions of the Blast Furnace (BF) of more than 15 years are the customers demand all over the world. The required target life can be reached by the well established classical copper cooling stave, covering the BF-shell from the hearth up to parts of the BF-stack. Some BF-areas, like bosh and belly (cohesive zone) as well as the transition zone (lower and middle stack) are critical wear attack mechanism zones. In these critical BF-areas, the copper cooling staves, covered with conventional wear protection linings have shown that they are not sufficient enough to reach the customers demand. During the long-lasting BF-campaign, especially in the cohesive zone, like bosh, belly and lower stack; natural accretion layers may form in front of the copper cooling staves by freezing a mixture of slag and pig iron. Unfortunately, all of the formed accretion layers are not stable enough to protect the copper stave surface in case of rough wear mechanisms, like descending burden and upstreaming gasjets during the BF-campaign. Copper stave wear protection linings, such as metal- or cast iron inserts, refractory mass / mixes- top coatings, shotcastings/shotcretings, solgel refractory mass; as well as all kind of graphite-, doped carbon-, high alumina- or silicon carbide refractory bricks are not abrasion resistant enough to protect the copper cooling stave surface during the long-lasting BF-campaign, to reach the required life time target. This presentation is focusing on: • The proven copper cooling stave concept, design and realisation; especially for the bosh and the stack transition zone. • The developed, well experienced and installed copper cooling stave wear protection; using very high abrasion resistant silicon-infiltrated and reaction-bonded silicon carbide (RBSiC)-Inserts.