CET IN SOLIDIFYING ROLL -THERMAL GRADIENT FIELD ANALYSIS KRT W KRYSTALIZUJĄCYM WALCU -ANALIZA GRADIENTOWEGO POLA TEMPERATURYAs the first step of simulation, a temperature field for solidifying cast steel and cast iron roll was created. The convection in the liquid is not comprised since in the first approximation, the convection does not influence the analyzed occurrence of the C → E (columnar to equiaxed grains) transition (CET) in the roll. The obtained temperature field allows to study the dynamics of its behaviour observed in the middle of the mould thickness. This midpoint of the mould thickness was treated as an operating point for the C → E transition. A full accumulation of the heat in the mould was postulated for the C → E transition. Thus, a plateau at the T (t) curve was observed at the midpoint. The range of the plateau existence t C ↔ t E corresponded to the real period of transition, t R C ↔ t R E that occurs in the solidifying roll. At the second step of simulation, the thermal gradients field was studied. Three ranges were distinguished: a/ for the formation of the columnar structure (the C -zone):b/ for the C → E transition (from columnar to fully equiaxed structure):c/ for the formation of the fully equiaxed structure (the E -zone):The columnar structure formation was significantly slowed down during incubation period. It resulted from a competition between columnar growth and equiaxed growth expected at that period of time.≈ 0 relationship was postulated to correspond well with the critical thermal gradient, G crit. . A simulation was performed for the cast steel and cast iron rolls solidifying as if in industrial condition. Since the incubation divides the roll into two zones (columnar and equiaxed) some experiments dealing with solidification were made on semi-industrial scale.A macrosegregation equation for both mentioned zones was formulated. It was based on a recent equation for redistribution after back-diffusion. The role of the back-diffusion parameter was emphasized as a factor responsible for the redistribution in columnar structure and equiaxed structure.Keywords: solidifying roll, thermal gradient field, columnar into equiaxed structure transition, macro-segregation index W pierwszym etapie symulacji wygenerowano numerycznie pole temperatury dla krzepnącego walca staliwnego oraz żeliwnego. Nie uwzględniono konwekcji uznając, że w pierwszym przybliżeniu konwekcja nie wpływa na przebieg transformacji C → E (struktura kolumnowa w równoosiową, CET). Uzyskane pole temperatury pozwala na analizę jego zachowania w środku grubości wlewnicy. Ten punkt wlewnicy zostałpotraktowany jako punkt operacyjny dla transformacji C → E. Postuluje się w tym modelu, że zachodzi pełna akumulacja ciepła we wlewnicy właśnie dla tej transformacji. Stąd, spłaszczenie krzywej T (t) jest obserwowane dla punktu operacyjnego. Zakres tego spłaszczenia oznaczony t C ↔ t E odpowiada rzeczywistemu okresowi transformacji, t Symulacja została przeprowadzona zarówno dla walców staliwnych jak i żeliwnych dla warunków zbl...
The presented studies are focused on the wear resistance and friction coefficient changes of the thermal diffusion (TD) zinc coating deposited on steel. The aim of research was to evaluate the variation in coating properties during dry friction as a result of the method of preparation of the basis metal. The measured properties were compared to those obtained after classic hot-dip (HD) zinc galvanizing—heat treated and untreated. Thermal diffusion zinc coatings were deposited in industrial conditions (according to EN ISO 17668:2016-04) on disc-shaped samples. The results obtained during the tribological tests (T11 pin-on-disc tester) were analysed on the basis of microscopic observations (with the use of optical and scanning microscopy), EDS (point and linear) analysis and microhardness measurements. The obtained results were similar to effects observed after heat treatment of HD zinc coating. The conducted analysis proved that the method of initial steel surface preparation results in changes in the coating’s hardness, friction coefficient and wear resistance.
The analyzed topic refers to the wear resistance and friction coefficient changes resulting from heat treatment (HT) of a hot-dip zinc coating deposited on steel. The aim of research was to evaluate the coating behavior during dry friction after HT as a result of microstructure changes and increase the coating hardness. The HT parameters should be determined by taking into consideration, on the one hand, coating wear resistance and, on the other hand, its anticorrosion properties. A hot-dip zinc coating was deposited in industrial conditions (according EN ISO 10684) on disc-shaped samples and the chosen bolts. The achieved results were assessed on the basis of tribological tests (T11 pin-on-disc tester, Schatz®Analyse device, Sindelfingen, Germany), microscopic observations (with the use of optical and scanning microscopy), EDS (point and linear) analysis, and microhardness measurements. It is proved that properly applied HT of a hot-dip zinc coating results in changes in the coating’s microstructure, hardness, friction coefficient, and wear resistance.
The analyzed topic refers to the corrosion resistance and changes in microhardness of the heat-treated (HT) hot-dip zinc coating deposited on bolts. The research aimed to evaluate the influence of the HT on the increase of the coating hardness and changes in anticorrosion properties. Hot-dip zinc coating was deposited in industrial conditions (acc. EN ISO 10684) on chosen bolts (M12x60). The achieved results were assessed based on corrosion resistance tests in neutral salt spray (salt chamber) and microhardness measurements. Tests were conducted in accordance with the adopted fractional plan, generated in the DOE module of the Statistica software. Using the conjugate gradient method optimal parameters of HT were determined. The conducted tests proved that the controlled heat treatment may increase the hardness of the hot-dip zinc coating without a significant deterioration in its basic protective function (corrosion resistance). The observed changes in the hardness and corrosion resistance of the zinc coating are a consequence of changes in its structure.
The steel substrate was cut by means of different methods, like water jet, laser or oxyacetylene blowpipe. So, some different surfaces (after cutting / without cutting) were subjected to the (Zn) -hot dip galvanizing. The galvanizing process was performed in industrial conditions by applying the constant temperature equal to 457• C, and a dipping time equal to 150 s. The (Zn) -coating morphologies and sub-layer thicknesses were analyzed to explain some expected differences in the coatings formation.Keywords: hot-dip Zn galvanizing, heat affected zone -HAZ, water jet cutting, oxyacetylene cutting, laser cutting W prezentowanej pracy podłoże stalowe cięto stosując różne metody: strumień wody, laser, palnik acetylenowo-tlenowy. W wyniku tego otrzymano zróżnicowaną powierzchnię (po cięciu/bez cięcia), którą poddano cynkowaniu ogniowemu. Proces cynkowania wykonywano w warunkach przemysłowych stosując stałe parametry: temperaturę 457• C, czas zanurzenia t=150 s. W trakcie badań analizowano morfologię powłoki cynkowej oraz grubości poszczególnych podwarstw w celu wyjaśnienia różnic w narastaniu powłok.
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