The Arvedi ESP process and a variety of produced materials have been continuously developed since the opening of the Arvedi ESP plant in Cremona in 2009 to meet market demands for more sophisticated steel grades. The development of grades for more advanced applications such as advanced high strength steels and multiphase grades is of interest. Dual phase grades such as DP600 are already produced through an ESP line on an industrial scale; additional multi-phase grades such as TRIP are under development. High-strength steels for the automotive industry have especially high demands on material properties. In addition to the mechanical material properties, an excellent surface quality is required. The fundamental basis for such material properties on rolled coils needs to be provided from continuous casting. This paper deals with the classification of different – either Si - or Al-based – alloying concepts for TRIP steels with respect to their prospective behaviour in a thin slab caster.
Today, continuous casting is the common technology for casting commercial steel grades. Conventional casting processes, like slab casting, are characterised by a moderate heat withdrawal and a rather low solidification velocity and cooling rate. Linking the casting and the rolling process demands a higher casting velocity, an increased heat withdrawal and thus, a higher local cooling rate. The absence of phase transformations during cooling and reheating before the rolling process makes the solidification microstructure more important for the behaviour of the steel during rolling and for the final product properties. Over several years the Christian Doppler Laboratory for "Metallurgical Fundamentals of Continuous Casting Processes" has developed an experimental setup for the simulation of solidification at higher cooling rates. The experiment is based on the principle of a dipping test under inert gas atmosphere inside a vacuum induction furnace. Recently, this apparatus has been equipped with a pyrometer in order to measure the temperature of the solidified sample during the subsequent cooling phase and also with a furnace in order to simulate different cooling and heat treatment strategies. Thus, it is possible to reproduce solidification and subsequent cooling of the cast material in casting-rolling processes and to characterise the microstructure and the mechanical properties of the solidified samples. The present work will give an overview on heat transfer in conventional casting processes, present a laboratory scale simulation of solidification a higher cooling rate, touch some aspects like the numerical simulation of the experiment and conclude with some results and an outlook on further planned work. Experimentelle Simulation der Erstarrung von Stahl bei hohenKühlraten. Der konventionelle Stranggießprozess ist der dominierende Prozess für das Vergießen herkömmlicher Kohlenstoffstähle. Die Erstarrung im Stranggießprozess, vor allem beim Brammenstranggießen, ist durch eine moderate Wärmeabfuhr und entsprechend geringe Erstarrungsgeschwindigkeiten und Kühlraten gekennzeichnet. Die Kopplung des Gieß-und Walzprozesses oder das direkte Gießen eines Produktes verlangt die Erhöhung der Gießgeschwindigkeit und deshalb auch die Erhöhung der Wärmeab-fuhr. Da die Phasenumwandlungen, die beim konventionellen Prozess während des Abkühlens und Wiedererwärmens auftreten, beim gekoppelten Gießwalzen fehlen, kommt der Erstarrungsstruktur auch eine größere Bedeutung für den nachfolgenden Walzprozess zu. Am Christian-Doppler-Labor für Metallurgische Grundlagen von Stranggießen wurde in Zusammenarbeit mit Siemens-VAI Metals Technologies ein Versuchsstand zur Nachbildung der beschleunigten Erstarrung entwickelt und umgesetzt. Das Experiment beruht auf einem Tauchversuch in einem Vakuuminduktionsofen unter kontrollierter Gasatmosphäre. Die Apparatur wurde vor kurzem mit einem Pyrometer ausgestattet, um die Temperatur der erstarrten Proben während der Abkühlung bestimmen zu können. Auch das Nachstellen bestimmter Temperaturzykle...
Thin slab casting and direct rolling technologies became important for hot strip production to increase the productivity, to lower the investment costs and to increase the energy efficiency. The main objective of our investigation is to gain a better understanding of the microstructural evolution starting from solidification through to the final hot rolled sheet. Small ingots were cast and direct rolled and reheated and rolled, using a thermomechanical testing machine. The differences in the recrystallization kinetics during both production routes were measured using double hit hot compression tests. In addition, multipass deformation trials were performed to reveal differences in the resulting microstructure and the grain size homogeneity. It was found, that the coarse initial microstructure before rolling become negligible after three rolling passes. This means that despite the simple and economical direct rolling similar mechanical strip properties can be obtained in comparison to conventional strip production routes.
With five Arvedi ESP lines, Rizhao Steel in China is now focusing on the highly attractive local and export markets for high-quality, thin-gauge strip products. The first lines began operations in 2015.High-strength but lightweight car bodies, ultra-thin structures paired with the highest tensile strength – and all at the lowest production costs. Innovative processes are required in order to fulfil the demands of the car and metals industries. With precise thermo-mechanical rolling and rigorous temperature guidance in the narrowest possible operations windows Arvedi ESP opens the door to producing demanding steel grades in the shortest implementation times and at reduced alloying costs. Low operation costs are also provided by efficient induction heating and the resulting energy savings.This paper presents the ESP plant setup of Rizhao Steel as well as the training and support program. Additionally the potentials of AHSS production with ESP will be described by referencing the results of the first ESP plant in operation since 2009 at Arvedi Steel, Italy, and the ESP plants of Rizhao steel.
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