Hypothesis testing to confirm the influence of technological parameters on poor quality production

This report addresses some chosen statistical methods that could be used to confirm and set up the required functions of technology in foundry companies where parts are cast by the low-wax casting method, whereas these chosen statistical methods are intended to reduce poor quality of produced parts. This research was made on a practical example. Utilization of hypothesis testing methods was examined in order to confirm technological parameters having some influence on the products quality. The data were compared before and after the implementation of changes aimed at reduction of poor quality produced parts in the wax department. The results confirmed that the implemented change had a statistically conclusive influence.Artykuł przybliża niektóre wybrane metody statystyczne, które można wykorzystać w celu sprawdzenia ustawień wymaganych funkcji w technologii odlewania metodą wosku traconego, do zmniejszenia wad produkcji. Badania przeprowadzono na konkretnym przykładzie. Zbadano wykorzystanie metod testowania hipotez w celu sprawdzenia parametrów technologicznych wpływających na jakość odlewów. Porównano dane przed i po wprowadzeniu zmian w celu ograniczenia wad produkcji w dziale woskowni.Web of Science5931067106

Possibilities for increasing the purity of steel in production using secondary-metallurgy equipment

The possibilities for increasing the purity of steel during the production of the liquid phase using secondary metallurgy mainly relate to affecting the number of emerging occlusions, their size, morphology and chemical composition. The metallographic purity of steel during production in an electric-arc furnace (EAF), in a ladle furnace (LF) and during processing with VD caisson technology was assessed. The steel samples were processed by means of an electron microscope and were simultaneously tested using the single-spark-evaluation (SSE) method. The aim of this investigation was to find the possibility for an operative steel-quality control and to obtain the desired mechanical properties already while processing the liquid phase.Web of Science48578678

Effect of cast steel production metallurgy on the emergence of casting defects

The paper documents metallurgical possibilities of high alloy cast steel production in open induction medium frequency furnaces and an electric arc furnace in a gravity die casting foundry. The observation was focused on the emergence of gas defects in steel castings. The content of gases achieved during the metallurgical processes was evaluated for every unit of the production equipment and the casting ladle before casting into disposable sand moulds. The sand mould area was considered to be constant. The aim was to evaluate the current metallurgical possibilities of affecting the content of gases in high alloy cast steel in the current technical conditions of the foundry.Web of Science55470470

Effect of Higher Silicon Content and Heat Treatment on Structure Evolution and High-Temperature Behaviour of Fe-28Al-15Si-2Mo Alloy

This paper describes the structure and properties of cast Fe3Al-based alloy doped with 15 at. % of silicon and 2 at. % of molybdenum. The higher content of silicon is useful for the enhancement of high-temperature mechanical properties or corrosion resistance of iron aluminides but deteriorates their workability due to increased brittleness. It was found that the presence of both alloying elements leads to an increase of values of the high-temperature yield stress in compression. The heat treatment (annealing at 800 degrees C for 100 h) used for the achievement of phase stability causes the grain coarsening, so the values of the high-temperature yield stress in compression are lower at 600 degrees C and 700 degrees C in comparison to values measured for the as-cast state. This stabilization annealing significantly improves the workability/machinability of alloy. Furthermore, the higher silicon content positively affects the values of the thermal expansion coefficient that was found to be lower in the temperature range up to 600 degrees C compared to alloys with lower content of silicon

Uplatnění progresivních metalurgických a ekonomických prvků při řízení kyslíkové ocelárny

Import 20/04/2006Prezenční výpůjčkaVŠB - Technická univerzita Ostrava. Fakulta metalurgie a materiálového inženýrstv

Progresivní prvky výroby a plynulého odlévání oceli v Ocelárně VÍTKOVICE STEEL a.s.

Import 11/03/2008PrezenčníNeuvedenoNeuveden

Možnost razžvepljanja legiranega jekla v vod-napravi z izkoriščanjem kemijskega ogrevanja

The paper describes the knowledge about and results of the experimental heats performed in an electric steel plant. The aim was to verify the possibilities of a controlled desulphurization of alloy steel in a VOD (Vacuum Oxygen Decarburization) device, particularly when using chemical heating through the OVD process (Oxygen Vacuum Deoxidation/Degassing), as well as the standard slag formers. Experimental procedures were used in the production of alloy tool steel. Both, the system of making the reducing slag and optimizing the composition of individual oxides in order to achieve the desired basicity, are complicated by the products of the chemical heating. Therefore, it was necessary to develop a new production technology that would eliminate such oxide products of chemical heating and, thus, the maximum degree of desulphurization could be achieved. The main principle of the technology is to create appropriate thermodynamic and kinetic conditions required for desulphurization. In particular, this concerns a low oxygen activity in the steel, the composition of refining slag, and an intense bath stirring with argon.Web of Science47114013

Optimization of a concasting technology via a dynamic solidification model of a slab caster

Solidification and cooling of a continuously cast steel slab and the heating of the mould is a very complicated problem of transient heat and mass transfer. This original three-dimensional (3D) numerical model is capable of simulating the temperature field of a caster. The numerical computation has to take place simultaneously with the data acquisition-not only to confront it with the actual numerical model, but also to make it more accurate throughout the process. The utilization of the numerical model of solidification and cooling plays an indispensable role in practice. An important step in this analysis is to determine the necessary quantities in the course of concasting. The software enables data acquisition in real time, which is necessary for optimization. This is ensured by the correct process procedure: real process -> input data -> numerical analysis -> optimization -> correction of process. This procedure is necessary for optimization (i.e. maximization of the quality of the process)-especially when reacting to specific needs and conditions in the operation

Wykorzystanie przemysłowych żużli syntetycznych w hucie třinecké Železárny, a.s.

The paper summarises experience with using synthetic slags on the CaO - Al2O3 oxide basis in the technological flow of the oxygen converter steelworks in TŘINECKÉ ŽELEZÁRNY, a.s. These slags are used as an alternative to slags containing fluorspar which unfavourably affects both the service life of ladle linings and the steelwork's working environment. The content gives the first knowledge of using the Refraflux type synthetic slag to desulphurize steel, and it also provides a basic statistical evaluation of the heat produced.W pracy podsumowano doświadczenia z użyciem żużli syntetycznych bazujących na tlenkach CaO - Al2O3 w technologii dmuchu tlenu w konwertorze stalowni TŘINECKÉ ŽELEZÁRNY, a.s. Żużle te są stosowane jako alternatywa dla żużli zawierających fluoryt, które niekorzystnie wpływają zarówno na żywotność wyłożenia kadzi i środowisko pracy stalowni. Artykuł przedstawia pierwsze doświadczenia z wykorzystaniem syntetycznych żużli typu Refraflux do odsiarczania stali, a także podstawowe dane statystyczne wytopu