•Information is presented on the production of a dual-phase magnetic material based on silicon steel.•Analysis of the samples shows the presence of magnetic phases in the treated layer.•There is a ...significant decrease in strength characteristics for the magnetic phase of a two-phase magnetic material.
Dual-phase magnetic materials are materials that have different magnetic permeability in selected areas. This feature of dual-phase magnetic materials opens up great prospects for new design solutions for some topologies of electrical machines. This article presents the results of a study on obtaining a dual-phase magnetic material from sheets of electrical silicon steel with a Si content of 2.4–3.8% during ion-plasma nitriding in a glow discharge. Based on the optimal parameters of the vacuum environment, samples of silicon steel sheets were processed with different holding times. Then, the structure of each of the samples was studied using an X-ray diffractometer with the determination of the composition of the surface layer of the treated samples and the identification of the non-magnetic phase. As a result of the study, the possibility of obtaining a non-magnetic austenite phase during ion-plasma nitriding was shown, however, the formation of a significant amount of the nitride phase was noted. An experiment on transformers shows a decrease in magnetic permeability and magnetization for a dual-phase magnetic material. Strength tests show satisfactory characteristics for the non-magnetic phase of the obtained dual-phase magnetic material, as well as a strong decrease in strength characteristics for the magnetic phase of the dual-phase magnetic material.
This articles discusses the use of 20Kh23N18T mark stainless steel and its foreign analogue AISI 310S instead of 12Kh18N10T steel as a material for making shaping dies used in the manufacture of ...glass insulators made from S93-3M mark electrovacuum glass. Such insulators are widely used in the radio-electronic industry as housings for magnetically operated contacts. It is shown that at operating temperatures a chemical interaction occurs between both grades of steel and S93-3M grade glass, which results in deterioration in the product quality on account of the appearance of a large number of gas bubbles in the product. It was ascertained that the additional heat treatment makes it possible to diminish the consequences of this chemical interaction, and thereby improve the quality of the resulting product.
In this study, the influence of different fire conditions on tempered 32CrB3 steel bolts of Grade 8.8 was investigated. In this research different temperatures, heating time, and cooling methods were ...correlated with the microstructure, hardness, and residual strength of the bolts. Chosen parameters of heat treatments correspond to simulated natural fire conditions that may occur in public facilities. Heat treated and unheated samples cut out from a series of tested bolts were subjected to microstructural tests using light microscopy (LM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), XRD phase analysis, and the quantitative analysis of the microstructure. The results of the microstructure tests were compared with the results of strength tests, including hardness and the ultimate residual tensile strength of the material (UTS) in the initial state and after the heat treatments. Results of the investigations revealed considerable microstructural changes in the bolt material as a result of exposing it to different fire conditions and cooling methods. A conducted comparative analysis also showed a significant effect of all such factors as the temperature level of the simulated fire, its duration, and the fire-fighting method on the mechanical properties of the bolts.
•Ultrasonic sound velocity and attenuation are sensitive to microstructural changes.•Volume fraction of phases and percentage of sub-grain boundaries affect greatly ultrasonic testing ...measurements.•The ultrasonic velocity and attenuation can be well correlated with the mechanical properties.•Ultrasonic velocity and attenuation indicate good capacity to identify changes in microstructure.
In this work microstructural characterization and mechanical testing results were correlated with ultrasonic velocity and sound attenuation of steels SAE-1040 and SAE-4340. Both types were subjected to three types of heat treatment; the first was annealing at 850°C, the second was austenitizing at 1000°C followed by oil quenching and the third was similar austenitizing then water quenching. Treatments of SAE-1040 steel resulted in microstructures containing different ferrite and pearlite contents, different inter-lamellar spacing and also different grain size. Similar ferrite and pearlite content was obtained when annealing SAE-4340 whereas, oil and water quenching resulted into martensite. With SAE-1040, the sound velocity was reduced in the order of annealing–oil–water quenching due to the reduction of ferrite on the expense of pearlite. The same order in sound velocity reduction was also obtained with SAE-4340 due to the change in microstructural phases from pearlite to martensite. In comparison to pearlite, the martensite possessed higher crystal lattice distortion, higher dislocation density and lower elastic modulus all of which contribute in reducing sound velocity. Attenuation of SAE-1040 increased in the order of annealing–oil–water quenching because of higher pearlite content and the reduction in inter-lamellar spacing. Attenuation of SAE-4340 gave an opposite order due to the reduction of the extent of microstructural anisotropy. The mechanical properties and hardness were predominantly affected by the microstructural phases leading to the logical correlation with ultrasonic parameters.
In the present work laser surface alloying of low carbon steel with carbon has been investigated for automotive application. The laser used was Nd-YAG, having a wavelength of 1.06
μm. It was operated ...at energy levels between 5 and 30
J, pulse duration from 1.5 to 4
ms and beam diameter varied between 1 and 3
mm. As a result of laser treatment at different energy levels and pulse durations, treated layers of varying thickness between 0.03 and 0.20
mm with carbon concentrations exceeding the eutectic point are produced. As a consequence of this treatment, a range of microstructures and microhardness values was obtained. High hardness values were observed in the layers with predominantly martensite structure (650
Hv) and relatively low values in region showing austenite microstructure (500
Hv) and maximum hardness (850
Hv) was found in the layer, which showed large proportion of Fe
3C. Surface melting of nodular cast iron by ruby laser (0.69
μm wavelength) has been also reported. The presence of retained austenite and martensite was found to be a characteristic feature in most of the treated layers.
The quench cracking that occurs in steels with carbon contents greater than about 0.3
wt% when the steel is austenitized and quenched into water is shown here to require contact of water with the ...surface of the steel. It can be avoided by first plating the steel with nickel. The appearance of the fracture surface of a quench crack is identical with that of a similar steel that has suffered hydrogen-induced cracking. It is concluded that quench cracking emanates from hydrogen released by the breakdown of water molecules that contact the steel surface.
During heat treatment and other production processes, gradients of temperature and other observables may vary rapidly in narrow regions, while in other parts of the workpiece the behaviour of these ...quantities is quite smooth. Nevertheless, it is important to capture these fine structures during numerical simulations. Local mesh refinement in these regions is needed in order to resolve the behaviour in a sufficient way. On the other hand, these regions of special interest are changing during the process, making it necessary to move also the regions of refined meshes. Adaptive finite element methods present a tool to automatically give criteria for a local mesh refinement, based on the computed solution (and not only on a priori knowledge of an expected behaviour).
We present examples from heat treatment of steel, including phase transitions with transformation induced plasticity and stress dependent phase transformations. On a mesoscopic scale of grains, similar methods can be used to efficiently and accurately compute phase field models for phase transformations.
Adaptive Finite‐Elemente‐Simulationen für makroskopische und mesoskopische Modelle von Stahl
Bei der Wärmebehandlung und anderen Produktionsschritten können die Gradienten der Temperatur und anderer Größen in schmalen (Rand‐) Bereichen eines Werkstücks stark variieren, während sie in großen Bereichen relativ glatt sind. Trotzdem ist die Auflösung dieser feiner Strukturen in einer numerischen Simulation sehr wichtig. Eine lokale Gitterverfeinerung ist notwendig, um das Verhalten genügend genau aufzulösen. Darüber hinaus ändern sich diese Regionen während des Prozesses, was auch eine Veränderung der verfeinerten Gitterregionen notwendig macht. Adaptive Finite‐Elemente‐Methoden sind ein Werkzeug, das, basierend auf der berechneten Lösung (und nicht auf a priori Wissen über das Verhalten) automatische Kriterien für lokale Gitterverfeinerungen liefert.
Wir geben Beispiele aus der Wärmebehandlung von Stahl mit Phasenumwandlungen, Umwandlungsplastizität und spannungsabhängigem Umwandlungsverhalten. Auf der mesoskopischen Skala von Körnern können ähnliche Methoden benutzt werden, um Phasenfeld‐Modelle für Phasenumwandlungen effizient und hinreichend genau zu berechnen.
In our former work 1 we have discussed the impedance of differently heat treated steels X20Cr13 in 0.1 M H2SO4, undergoing an active passive transition. Impedance spectra were interpreted in terms of ...a model by Armstrong 2, 3, describing the electrochemical reaction at interfaces with adsorbed intermediates. The present work was performed in order to study this phenomenon in more detail, with computer simulations of a new created and more convenient equivalent circuit in comparison with the former model. Computer simulations of equivalent circuits were also made in the region of passivity which was also continuation of our earlier work 4. In this sense the entire study for these steels was completed by collating distinctive parameter values, demonstrating electrochemical characteristics of steel X20Cr13, undergoing different heat treatments in the active‐passive and passive region.
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