May 20 th - 22 nd 2020, Brno, Czech Republic, EU EXPERIMENTAL STUDY OF THERMOPLASTIC PROPERTIES OF AGGLOMERATE Vlastimil NOVÁK, Lenka ŘEHÁČKOVÁ, Petr KLUS, Bedřich SMETANA, Silvie ROSYPALOVÁ, Ľubomíra DROZDOVÁ, Jana DOBROVSKÁ VSB - Technical University of Ostrava, Ostrava, Czech Republic, EU, vlastimil.novak@vsb.cz https://doi.org/10.37904/metal.2020.3449 Abstract Traditional routes of ironmaking and steelmaking processes demand high-temperature preparatory steps, such as coking and sintering. These processes are of great concern since they represent a considerable environmental burden. As an alternative, carbon-containing iron oxides agglomerates (sinters) can be used. In this work, the assessment of thermoplastic properties of prepared sinters, especially the determination of softening and liquidus temperatures, was performed by two methods: optical and spindle drop method. For the first-mentioned method, high-temperature observation furnace CLASIC was employed, which enables observation of changes in specimen shape depending on temperature. While in the case of the second method, Furnace Rheometer System FRS 1600 was used. This system allows measuring changes of spindle height as a function of temperature when different normal forces, in specific 3 and 20 N, are applied. Besides, analyzed sinters were of different grain sizes and contained approximately 59 wt.% of iron and 7.2 wt.% of iron(II) oxide. The samples were measured up to liquidus temperature at various heating rates in an inert atmosphere of argon gas. In summary, a good agreement between phase transformation temperatures measured by both methods was achieved, and the influence of experimental conditions on these temperatures was confirmed. Keywords: Agglomerate, thermoplastic properties, softening temperature, melting 1. INTRODUCTION Within ironmaking and steelmaking processes, one of the most critical areas throughout a blast furnace is the cohesive zone. In this region, ore sinters begin to soften and consequently melt by further heating and reduction. This zone is hardly porous, and the gas can only flow through coke lumps [1,2]. Its shape, thickness and position significantly affect furnace productivity and fuel efficiency. The temperature properties of iron ore burden are essential, given the creation of blast furnace melting-softening zone [3,4]. Usually, consideration is being given to the softening starting temperature, softening finishing temperature and melting temperature which are defined as the temperature at which burden pressure drop is about 1 kPa or burden contraction reaches 4 - 10 %, as the temperature whereupon pressure drop falls down to 0.5 kPa or contraction attains 40 %, and as the temperature when pressure drop progresses significantly [3,5]. The study and knowledge of these characteristics are of great importance. The softening and melting behavior of blast furnace raw materials has been studied intensively for over five decades. During that period, various methodology approaches emerged, enabling either routine testing or more sophisticated testing of blast furnace burden materials concerning cohesive zone. Typically, the ferrous burden, together with coke, is placed in a graphite crucible and then into the vertically oriented furnace. The samples are heated under desired regimes while pressure drop throughout the burden is registered depending on temperature [5,6]. A similar experimental setup was used by Kaushik [7], where, instead of measurement of pressure, changes in sample shape were visualized using X-ray fluoroscopy. Ślęzak et al. used a high-temperature rheometer, which is intended primarily for testing rheological parameters, to determine softening temperatures by