Comparison environmental and technological properties of various technologies of productions of foundry moulds and cores

Tato bakalářská práce pojednává o srovnání ekologických a technologických vlastností různých technologií výroby slévárenských forem a jader. Práce obsahuje přehled technologií výroby forem a jader používaných ve slévárenské praxi a u jednotlivých technologií jsou popsány jejich vlastnosti, výhody, nevýhody a použití. Dále jsou uvedeny škodlivé látky, které jsou obsažené v pojivových systémech nebo se tvoří při odlévání. Požadavky na ekologii výroby odlitků jsou stále přísnější, a proto jsou předpokladem vývoje nových metod, které jsou šetrné k životnímu prostředí a zároveň jsou charakterizovány výhodnými technologickými a ekonomickými vlastnostmi.This bachelor thesis deals about comparison of environmental and technological properties of various technologies of productions of foundry moulds and cores. The thesis comprises overview of technologies of produciton of foundry moulds and cores used in foundry practice and the individual technologies are described properties, advantages, disadvantages and applications. There are mentioned harmful substances which are contained in the binder systems or are formed during casting. Requirements for ecological production castings are becoming stricter, therefore a prerequisite for the development of new methods which are environmentally friendly and are also characterized by advantageous technological and economical characteristics.

Numerical modelling of metal melt refining process in ladle with rotating impeller and breakwaters

The paper describes research and development of aluminium melt refining technology in a ladle with rotating impeller and breakwaters using numerical modelling of a finite volume/element method. The theoretical aspects of refining technology are outlined. The design of the numerical model is described and discussed. The differences between real process conditions and numerical model limitations are mentioned. Based on the hypothesis and the results of numerical modelling, the most appropriate setting of the numerical model is recommended. Also, the possibilities of monitoring of degassing are explained. The results of numerical modelling allow to improve the refining technology of metal melts and to control the final quality under different boundary conditions, such as rotating speed, shape and position of rotating impeller, breakwaters and intensity of inert gas blowing through the impeller.Web of Science64266465

The influence of optimization parameters on the efficiency of aluminium melt refining by using physical modelling

The article describes the influence of optimization parameters on the efficiency of aluminium melt refining by using physical modelling. The blowing of refining gas, through a rotating impeller into the ladle is a widely used operating technology to reduce the content of impurities in molten aluminium, e.g. hydrogen. The efficiency of this refining process depends on the creation of fine bubbles with a high interphase surface, wide-spread distribution, the residence time of its effect in the melt, and mostly on the wide-spread dispersion of bubbles in the whole volume of the refining ladle and with the long period of their effect in the melt. For physical modelling, a plexiglass model on a scale of 1:1 is used for the operating ladle. Part of the physical model is a hollow shaft used for gas supply equipped with an impeller and also two baffles. The basis of physical modelling consists in the targeted utilization of the similarities of the processes that take place within the actual device and its model. The degassing process of aluminium melt by blowing inert gas is simulated in physical modelling by a decrease of dissolved oxygen in the model liquid (water).Web of Scienc

Computational fluid dynamics (CFD) analysis of medium flow and removal of inclusions in a two-strand tundish

The article presents the results of the CFD simulation of the method of medium flow and mixing, as well as the movement and removal of solid particles in the model of two-strand tundish as a result of installed internal arrange ment. Two variants including turbulence inhibitor and impact pad with a ball cutting area were modeled for the tests. CFD simulations are a continuation of previous tests with the use of the physical water model of the continu ous steel casting (CSC) deviceWeb of Science623-433833

Decomposition of γ-Fe in 0.4C–1.8Si-2.8Mn-0.5Al steel during a continuous cooling process: A comparative study using in-situ HT-LSCM, DSC and dilatometry

Continuous cooling transformation (CCT) diagrams represent roadmaps for producing all heat-treatable steels. CCT curves provide valuable information on the solid-state phase transformation sequence, depending on the defined cooling strategies, the alloying concept of the steel and previous processing steps. The experimental characterization of CCT diagrams is usually done on a laboratory scale applying thermal analysis of dilatometry. In current research studies, however, also other in-situ methods such as high-temperature laser scanning confocal microscopy (HT-LSCM) or differential scanning calorimetry (DSC) are frequently used to investigate phase transformations during thermal cycling. In the present study, HT-LSCM observations and DSC analysis are critically compared with dilatometry results by investigating the CCT diagram of a 0.4%C-1.8%Si-2.8%Mn-0.5%Al (in mass pct.) advanced steel grade. Furthermore, classical examinations by optical microscopy and hardness measurements were performed to support the analysis. In general, very good consistencies between all experimental techniques were identified in determining the transformation start temperature for pearlite, bainite and martensite. The optical microscopy confirmed the observed phase transformations and the results correlated with the measured hardness response. Based on the results, coupling of HT-LSCM and DSC is considered as a valuable novel approach to plot CCT diagrams in future research.Web of Science2

Physical and Numerical Modelling of Critical State of Fluid Steel in Tundish

Předkládaná disertační práce se zabývá využitím fyzikálního a numerického modelování ke studiu procesu proudění oceli v asymetrické pětiproudé mezipánvi plynulého odlévání oceli. Pro účely fyzikálního modelování byl použit model provozní mezipánve sestrojený z plexiskla v měřítku 1:4, pro numerické modelování byla vytvořena geometrie provozní mezipánve v měřítku 1:1. Proces proudění taveniny v mezipánvi byl při fyzikálním modelování modelován modelovou kapalinou (vodou), v rámci numerického modelování byla standardně jako proudící médium použita tekutá ocel. Pozornost je zaměřena na posouzení relevantních parametrů majících vliv na charakter proudění lázně v mezipánvi – tvar dopadového místa, vnitřní výška dopadového místa, poloha stínicí trubice vůči dopadovému místu a vzdálenost ústí stínicí trubice ode dna dopadového místa. Byly verifikovány i mezní stavy těchto parametrů. Z fyzikálních experimentů byly získány C křivky, ze kterých byly stanoveny retenční časy a zastoupení podílu objemů v mezipánvi. Z numerických simulací byly retenční časy stanoveny z vypočtených F křivek. Výsledky z obou metod modelování dosáhly stejného charakteru, proto lze vzájemnou verifikaci výsledků fyzikálního a numerického modelování považovat za dostatečně vypovídající.The submitted dissertation thesis deals with the use of physical and numerical modelling to study the process of the steel flow in the asymmetric five-strand tundish of continuous casting of steel. For the purposes of physical modelling, a plexiglas model on a scale of 1:4 was used for the operating tundish, and for numerical modelling, the geometry of the operating tundish was created on a scale of 1:1. The melt flow process in the tundish was modelled with a model liquid (water) in the physical modelling, while liquid steel was used as the standard flowing medium in the numerical modelling. Attention is focused on the assessment of relevant parameters influencing the character of the flow of the bath in the tundish - the shape of the impact pad, the internal height of the impact pad, the position of the ladle shroud to the impact pad and the distance of the ladle shroud orifice from the bottom of the impact pad. The limit states of these parameters were also verified. C curves were obtained from the physical experiments, from which the residence times and the representation of the volume fraction in the tundish were obtained. From the numerical simulations, the retention times were obtained from the calculated F curves. The results from both modelling methods achieved the same character, therefore the each other verification of the results of physical and numerical modelling can be considered sufficiently informative.652 - Katedra metalurgických technologiívyhově

Numerical Modelling of Steel Flow in Tundish

Předkládaná diplomová práce pojednává o numerickém modelování proudění oceli v mezipánvi. Práce v teoretické části obsahuje popis zařízení plynulého odlévání. Větší pozornost je věnována samotné mezipánvi a procesům v ní probíhajících, numerickému modelování a rozborům celosvětové literatury z oblasti numerického modelování proudění oceli v mezipánvi. V experimentální části se práce věnuje postupu řešení modelování proudění v CFD programu ANSYS Fluent. Dosažené výsledky numerického modelování graficky zobrazují charakter proudění v mezipánvi pomocí vektorů rychlosti při změně geometrie vnitřního prostoru mezipánve.This diploma thesis deals with the numerical modeling of steel flow in tundish. The theoretical part of thesis contains the description of continuous casting. Special attention is paid to the processes in tundish and about tundish itself, numerical modeling and analysis of the world litarature, which deals with numerical modeling of steel flow in tundish. In the experimental part of thesis is based on the solution process in CFD ANSYS Fluent software. Achieved results of numerical modeling graphically show the flow pattern in the tundish by means of velocity vectors when changing the geometry of the tundish interior space.618 - Katedra metalurgie a slévárenstvívýborn

Numerical analysis of RTD curves and inclusions removal in a multi-strand asymmetric tundish with different configuration of impact ad

To effectively remove non-metallic inclusions from the steel during the flowing in a five-strand asymmetric tundish, the novel configuration of the impact pad was developed. For analysis, complex numerical modelling in the programme ANSYS Fluent was used. The Lagrangian Discrete Phase Model of inclusion tracking was applied. The distribution of inclusions, with sizes ranging from 2 mu m to 100 mu m and density from 2500 to 3500 kg center dot m(-3), was considered only through the shroud tube. The residence time distribution (RTD) curves and inclusion removal efficiency were used for evaluation of steady state steel flow character depending on internal configuration of a tundish with an impact pad in two design modifications (Modification 1-M1, Modification 2-M2). The preliminary results showed that in the case of asymmetric geometry plays a role the computational mesh independency. The assembly method with cut cell approach was satisfactory even when the tundish geometry was changed. The RTD curves with an M1 showed a huge dead volume in the tundish. In the case with an M2, the RTD curves are more or less uniform for all casting strands, and the removal of inclusions to slag increased from about 55% up to 70% in comparison with M1.Web of Science107art. no. 84

Modelling of technological parameters of aluminium melt refining in the ladle by blowing of inert gas through the rotating impeller

The presented paper deals with the use of physical modelling to study the degassing process of aluminium melts in the refining ladle by blowing inert gas through a rotating impeller. For the purposes of physical modelling, a plexiglass model in a scale of 1:1 is used for the operating ladle. Part of the physical model is a hollow shaft used for gas supply that is equipped with an impeller and two baffles. The degassing process of aluminium melt by blowing of inert gas is simulated at physical modelling by a decrease of dissolved oxygen in the model liquid (water). This paper is aimed at the evaluation of laboratory experiments that were obtained by the method of physical modelling. Attention is focused on the assessment of relevant parameters for the degassing process-rotary impeller speeds, volume flow rate of inert gas, the distance of the impeller from the bottom of the refining ladle, and impeller variant. The preliminary results of physical modelling show that the optimal results of the refining process are achieved by using the F2A 190 impeller.Web of Science112art. no. 28

Physical Experiments and Numerical Simulations of the Influence of Turbulence Inhibitors and the Position of Ladle Shroud on the Steel Flow in an Asymmetric Five-Strand Tundish

The submitted article deals with the use of physical and numerical modelling to study the process of the steel flow in an asymmetric five-strand tundish that continuously casts steel. For the purposes of physical modelling, a 1:4-scale plexiglass model was used as the operating tundish, and for numerical modelling, the geometry of the operating tundish was created on a 1:1 scale. A model liquid (water) was used in the physical modelling of the melt flow process, while liquid steel was used as the standard flowing medium in the numerical modelling. We assessed the relevant operating parameters influencing the characteristics of the flow of the bath in the tundish—the shape of the turbulence inhibitor, the position of the ladle shroud in relation to the turbulence inhibitor and the distance between the ladle shroud orifice and the bottom of the turbulence inhibitor. The preliminary results show that optimal steel flow characteristic results are achieved by using the TI3-C configuration. The results from both modelling methods achieved the same characteristics, therefore verifying the results of each other and demonstrating that when taken together, the results of physical and numerical modelling can be considered sufficiently informative