Seznam abstraktů 2015: POSTEROVÁ SEKCE A
Datum: 4.6.2015
The influence of cerium addition on solidification structure of the low-carbon 42CrMo4 steel was investigated. Alloys were prepared by means of a centrifugal casting. The addition of up to 0.05 wt. % of Ce in the steel produced greatly improved solidification structure with a suppressed columnar grain zone, finer grain size in the equiaxed grain zone, and zero area fraction of casting shrinkage cavity. The added cerium occurred in the steel both in the form of Ce oxide-sulphide inclusions and as dissolved atomic Ce segregated along with other elements at prior austenite grain boundaries and at interdendritic spacings. Microstructure (light optical microscope, SEM), X-ray EDX chemical microanalysis, and TOF-SIMS analysis (TESCAN ORSAY HOLDING) – mapping of elements in the structure of alloys were obtained. Rare-earth metals addition can be considered as a potential solution for grain structure refinement in heavy-weight castings of 42CrMo4 grade steel.
ACKNOWLEDGEMENTS:
This work was solved in the frame of the projects TA CR No. TA03010161 „Experimental development of non-ferrous metals utilization for microstructure refinement in the production of steel ingots for forgings in the specific work” and No. LO1203 “Regional Materials Science and Technology Centre – Feasibility Program”.
The paper is devoted to the study of the influence of experimental conditions of the direct thermal analysis method for use in high-temperature thermal analysis Netzsch STA 449 F3 JUPITER equipment during controlled cooling mode.
The first part of the article is focused on monitoring of the effect of experimental conditions on the solidification point of the standard material, nickel, a purity of 99.995%, and the total shape of cooling curve. On the basis of experimental measurements, a deviation obtained by interpreting the cooling curves for various cooling rates (5; 10; 15 and 20 ° C min-1) for nickel samples of various weights (5; 10; 15 and 20 g) from the generally recognized melting / solidification point of nickel (1455 ° C) can be quantified.
Besides the identification of the influence of experimental conditions on the temperature of solidification and the total cooling curve of nickel shape during solidification, the paper focuses attention on the mapping and interpreting the response found during the solidification of steel sample and the resulting to liquidus and solidus temperature of this steel. Findings from the discussion about the influence of experimental conditions on the solidification point of nickel and shape of cooling curve are implemented in a contribution to the method of identifying the solidus and liquidus temperature at selected real steel grades.
Special designs of nozzles or tuyeres are used in high-temperature units treating metal scrap for blowing gaseous technological media into the melt below the bath level. The higher technology utilisation of media is achieved by the blowing of media into the melt below the bath level. Due to the momentum of the discharge stream, which flows directly into the melt, the melt is set into intensive motion, which is very advantageous especially from the point of view of both temperature homogenization and homogenization concerning the chemical composition of the bath. The structural design of the majority of these tuyeres considers one or more channels composed of steel tubes or formed directly in the basic refractory material of the tuyere. From the point of view of structural design of these tuyeres, it is very important to know the dependence of exit parameters of blown media on the design parameters of the tuyere, in short on boundary conditions. The contribution contains division of and requirements for tuyeres and also description of chosen results of mathematical modelling of gaseous media flow through a channel with given dimensional parameters.
The aim of the study was to investigate the possibility of a partial upgrade of the existing technological line at the company Calumite s.r.o., intended for the treatment of blast furnace slag for its secondary use. The first step was detailed characterization of the materials by means of mechanical-physical parameters, among which are, for example, the particle size distribution, compressibility, and the angle of internal and external friction. In the next step, the method of magnetic separation was used to reduce the content of magnetic components in the samples, due to the potential of slag to also be used in the production of clear glass, among other types of use. Subsequently, it was examined how the original mechanical-physical characteristics of the measured samples have changed.
The results suggest that the added magnetic separation operations allow us to declare the Fe content in the non-magnetic parts of the product below the 0.1% limit. There was; however, slightly less effective separation of the material. After the above-mentioned material treatment, we succeeded in both cases in reducing the wall friction and increasing compressibility of the product, whereas the angle of internal friction and flow-ability remained with unchanged modes. Therefore, in terms of economic considerations, the introduction of an additional operation with magnetic separation for the treatment of blast furnace slag on the technological line can be assessed as a suitable innovation, and the secondary product can be used for the production of clear glass.
Last year we presented the mathematical model of the motion of burden materials in the bell-less blast furnace top of the type Paul Wurth or Vitkovice. The article from previous year concerned namely with one phase of the motion - motion at the rotating chute. In the actual article we continue with describing of following phase of the motion – downfall of burden materials after leaving the rotating chute.
In the steel industry, requirements for production optimization by the help of decreasing of energy and economical demands are increasing at the production of alloyed steels in the EAF. During the treatment of alloyed steel charging in the EAF containing chromium, its loss by oxidation and by the transition into slag happens. Chromium oxidation in the EAF happens during particular technological operations, however in different intensity. The main part of chromium loss from the melting happens during the oxidation period in which oxygen is blown with the aim of ensuring of basic refining reactions and melting decarbonisation. The chromium transition and its increase in the form of chromium oxides in the slag influences its properties which is shown by the creation of slag crust with the high viscosity which decreases the slag reactivity and prevents it from creation of foam slag during production of steel in the EAF. In the presenting paper, basic possibilities of Cr2O3 reduction from the slag at using of various reduction agents, application ways and technology modification of melting are given together with the proposal of theoretical calculation of consumption of chosen refining agents presenting silicon and aluminium for the conditions of steelwork VHM a.s.
Outdated machine for continuous casting of steel (CCM) has often fail to meet the requirements for production of the desired high quality carbon or stainless steel blank. Their control system acts as a so-called Black Box System, which provides operators the possibility of the system as needed to adjust and tune in order to achieve the required quality of steel produced. During the reconstruction of the caster is especially suitable to modify the secondary cooling, and slab CCM own rollways controlled cone possibly complemented well pronounced soft reduction. The necessary hardware modifications CCM cannot be designed without major upgrades the software control system based on the formation of new numerical models and their application to reduce of surface cracks and corners and central cavities or other defects.
It was therefore developed a series of numerical models in the form of modules, control modules and data visualization modules. Based on the model of the temperature field of the strand. The inclusion of modules in the control system CCM, which depends on the capabilities of the caster and customer requirements, can be built into the server embeddable the second levels of management. This server communicates via OPC protocol with superiors and subordinates systems. It also includes off-line simulator that allows you to test and simulate different cooling strategy and settings for different steel grades. The flexibility of such a solution is presented for converting the caster with nine to thirteen engine cooling zones and optimizing the secondary cooling supported by on-line numerical optimization, the current temperature field slab. It is also demonstrated by the inclusion of a modular system management system CCM.
In this paper, the problems of steel production have been illustrated, particularly the state and dynamics inherent in the groups of 28 countries – the largest producers in the world. Likewise, the ranking of the 25 largest enterprises producing steel has been presented. Furthermore, the chosen methods for the streamlining of steel production have been outlined. In particular, the environmental aspects of the functioning of steel producers have been illustrated.