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1

Effect of various factors on the measurement error of structural components of machine parts materials microhardness using computer vision methods

Vlasovets Vitaliy, Vlasenko Tatiana, Kovalyshyn Stepan, Kovalyshyn Olesy, Kovalyshyn Oleg, Kurpaska Sławomir, Kiełbasa Paweł, Bilovod Oleksandra, Shulga Lyudmila

Przegląd Elektrotechniczny

|

2023

|

R. 99, nr 1

323--329

EN

To assess the causes of failure of parts in operation, it is often necessary to assess the degradation of the structural and phase composition of the material and determine the cause of its change. Microhardness test is used to evaluate the mechanical properties of microvolumes of the material. Microhardness of structural components of steels and cast irons (armco iron ferrite, austenitic component of steel 12Х18Н10Т and cementite of centrifugally cast chrome-nickel cast iron (cast coating Ø910 mm)) was determined by restored four-sided pyramid impression with a square base and a top angle of 136±1. The paper evaluates the influence of the main factors on the micro-hardness error of ferritic, austenitic and carbide component of steels and cast irons: the amount and speed of the indenter load, the stiffness of the substrate, the field of distribution of plastic deformations around the impression, the quality of the surface preparation, the influence of grain boundaries and the relaxation of the impression shape over time. The main factors affecting the accuracy of measurements by the reconstructed impression method have been determined for each of the investigated phases: ferrite, austenite, and cementite.

PL

Aby ocenić przyczyny awarii części w eksploatacji, często konieczna jest ocena degradacji składu strukturalnego i fazowego materiału oraz określenie przyczyny jego zmiany. Do oceny właściwości mechanicznych mikroobjętości materiału stosuje się test mi-rotwardości. Mikrotwardość składników strukturalnych stali i żeliwa (ferryt żelaza armco, austenityczny składnik stali 12Х18Н10Т i cementyt odśrodkowo odlewanego żeliwa chromowo-niklowego (powłoka odlewu Ø910 mm)) określono przez przywrócony wycisk piramidy czterobocznej o podstawie kwadratowej i kącie wierzchołkowym 136±1. W pracy oceniono wpływ głównych czynników na błąd mikrotwardości ferrytycznego, austenitycznego i węglikowego składnika stali i żeliwa: wielkości i prędkości obciążenia wgłębnika, sztywności podłoża, pola rozkładu odkształceń plastycznych wokół wycisku, jakości przygotowania powierzchni, wpływu granic ziaren oraz relaksacji kształtu wycisku w czasie. Określono główne czynniki wpływające na dokładność pomiarów metodą zrekonstruowanego wycisku dla każdej z badanych faz: ferrytu, austenitu i cementytu.

2

To Study the Microstructural Evolution of EN353 Steel under Different Heat Treatment Conditions

Sharma Lochan, Chaubey Sandeep Kumar

Archives of Metallurgy and Materials

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2023

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Vol. 68, iss. 2

423--430

EN

Steel is basically used in construction, automobile, buildings, infrastructure, tools, ships, appliances, machines and weapons due to its good mechanical as well as metallurgical properties. Heat treatment of steels significantly enhance its mechanical and metallurgical properties due to the formation of various phases depending upon the type of steel used for specific application. In present study, blank of EN353 grade steel having different sizes were used to investigate the effect of heat treatment and microstructural changes. JMat-Pro software was used to predict the continuous cooling transformation behaviour of EN353 steel. Different phases such as bainite, perlite and other carbide inclusion can be observed in the microstructural examination. Pearlitic microstructure developed for the specimen of size 40×40×40 mm heated at 870°C for 2 hrs and then isothermal heating was performed for same specimen at 600°C for 73 min followed by air cooling. Relevance Statement: Steel is an important material which is frequently used in almost all areas such as structure building, pressure vessels, transportation and many more other applications. Addition of alloying elements in parent steel significantly improve the metallurgical as well as mechanical properties. Steel properties like tensile strength, toughness, ductility, corrosion resistance, wear resistance, hardness, hot hardness, weldability, fatigue etc. significantly improved with the addition of alloying and heat treatment. Heat treatment processes can be used to improve the properties of steel which are frequently used in many manufacturing industries. Different grades of steels which are heat treated under a set of sequence of heating and cooling to change their physical and mechanical properties so that it can fulfil its function under loading condition. With the help of heat treatment process desired microstructure has been achieved which exhibit good mechanical properties of steels.

3

Effects of the thermomechanical treatment on the microstructure and mechanical properties of ferrite–martensite dual phase steel

Ha M. T., Pham M. K., Nguyen H. H.

Archives of Materials Science and Engineering

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2023

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Vol. 124, nr 2

49--55

EN

Purpose: The study aims to investigate the effects of thermomechanical treatment, including tempering and hot–rolling, on the microstructure and mechanical properties of ferrite–martensite dual phase steel. Design/methodology/approach: The initial steel billet was a hypoeutectoid steel, which was annealed at 1000ºC, then hot–rolled at 920ºC, followed by austenitisation at various temperatures (730, 770, 800, and 830ºC), and finally quenched to obtain ferrite–martensite dual phase steel. X-ray diffractometer and optical microscopy investigated the microstructure and grain size of the dual-phase steel. Mechanical properties such as hardness, elongation, and tensile strength were also examined. Findings: The grain size decreased with increasing elongation percentage and remained constant after an elongation of 30%. The martensite/ferrite phase ratio increased with higher tempering temperatures. The hardness, elongation, and tensile strength reached a maximum when the tempering temperature was 800ºC. Research limitations/implications: Future studies could consider the effect of hot–rolling temperature or cold-rolling. Practical implications: The study proposes a straightforward and efficient thermomechanical treatment process to transform hypereutectoid steel into ferrite-martensite dual-phase dual- phase steel with improved mechanical properties. Originality/value: The study reveals the contributions of grain size and the martensite/ferrite ratio to the mechanical properties of ferrite–martensite dual steel through thermomechanical treatment.

4

Structure and Properties of the S49 Rail after a Long Term Outdoor Exposure

Konieczny Jarosław, Labisz Krzysztof

Advances in Science and Technology. Research Journal

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2022

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Vol. 16, no 2

280--290

EN

The subject of the research in this work was the S49 rail made of R260 rail steel (1.0623). The carried out investigations concern microstructure tests and tests of mechanical properties of rails after several years of exposure in the open air without usage. The purpose of the work was to determine on the basis of the results of research the possibilities of using the tested rail for usage and application for the construction of tracks on railway sidings. For investigations there were used diverse techniques reaching such engineering materials investigations like light or scanning electron microscope for microstructure investigations, as well as hardness and microhardness test were performed for determinations of the microstructural changes occurred in the upper area of the rails surface. The microstructure changes concerns especially the ferritic and pearlitic structure and the breaks in the present carbide mesh. During investigations it was found out that the tested railway rails are fully useful for application, after machining to achieve required dimensional parameters. It is also of high importance, of the economical point of view, that their price, also in case of earlier installation of the rails, may be lower than the current price offered on the marked for a entire new product. The price difference reaches dimensions in the range of 5% - 10%.

5

Influence of plastic deformation carbon steel on the process of burning electric arc

Vakulenko Igor Alex, Plitchenko Sergey, Kurt Bulent, Askerov Hangardas, Proydak Svetlana, Erdogdu Ahmet Emrah

Zeszyty Naukowe. Transport / Politechnika Śląska

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2021

|

z. 112

211--218

EN

During a study of the combustion process of a direct polarity electric arc, a directly proportional dependence of the electric current value on the degree of cold plastic deformation of carbon steel used as an electrode was found. To calculate the value of the electric current during arc burning, in the indicated ratio, it was proposed to replace the surface tension force of the liquid metal with the surface tension of ferrite of plastically deformed carbon steel. Calculation of the ferrite’s surface tension value on the deformation degree of the steel under study through the size of the coherent scattering regions was used to explain the observed dependence of the electric current during arc burning. From the analysis of the considered correlation ratios, it was found that with an increase in the cold deformation degree, the refinement of the coherent scattering regions results in the ferrite’s surface tension increase and consequently, to an increase in the electric current during arc burning. Comparative analysis of the obtained results of calculating the value of electric current during arc burning through the surface tension of ferrite of cold-deformed carbon steel showed a fairly good coincidence with experimental data. The differences did not exceed 9%.

6

Structural-phase transformations in 0.34C–1CRr–1Ni–1Mo–Fe steel during plasma electrolytic hardening

Rakhadilov B. K., Kozhanova R. S., Popova N. A., Nugumanova A. B., Kassymov A. B.

Materials Science Poland

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2020

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Vol. 38, No. 4

699--706

EN

Structural-phase transformations in 0.34C–1Cr–1Ni–1Mo–Fe steel during plasma electrolytic hardening were investigated. Electrolytic-plasma hardening of steel samples was carried out by surface quenching with rapid concentrated heating of the surface by plasma action and subsequent rapid cooling by heat removal from the depth of the sample by electrolyte jet. Plasma electrolytic hardening was carried out in the cathode mode in an electrolyte made from an aqueous solution containing 20 % sodium carbonate and 10 % carbamide. To study the structural-phase states of the modified layer, we used the method of transmission diffraction electron microscopy on thin foils. The study of steel samples was carried out before and after the plasma electrolytic hardening. Initially, the steel was a mixture of pearlite and ferrite grains. Surface hardening of 0.34C–1Cr– 1Ni–1Mo–Fe ferrite-pearlite steel led to a change in the structural-phase state and the formation of a packet-lamellar martensite structure. It was found that PEH leads to distortion of the crystal lattice and the formation of long-range internal stresses, as well as to the release of small particles of cementite and carbide of M23C6 type, uniformly distributed throughout the volume of the material. Surface hardening led to the increase in all quantitative parameters of the fine structure (ρ, ρ±, χ, σL, σd).

7

Weld joint properties of nitrogen-alloyed austenitic stainless steel using multi-pass GMA welding

Kumar Naveen, Arora Navneet, Goel S. K.

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 3

266--278

EN

The welding of nitrogen (0.29 wt%)-alloyed austenitic steel (grade 23-8-N) was performed with gas metal arc welding process. Solution treatment was performed at 950 °C and 1150 °C on base metal prior to weld. Base metal after second treatment has maximum ultimate tensile strength of 942 MPa and impact toughness 66 J. The microstructures of different zones of the weld joint were characterized using an optical microscope and field scanning electron microscope (FESEM). The microhardness, tensile and impact toughness tests of the weldments were conducted along with weld ferrite evaluation. ER2209 duplex filler metal used for welding has lower C and N content which changed the weld solidification mode. Weld has microstructure containing austenite + ferrite. Being a strong austenite former, nitrogen caused minimum ferrite near weld–HAZ interface while maximum ferrite content was observed at weld centre. Weld metal has minimum while base metal has maximum microhardness. UTS (892 MPa) and impact strength (96 J) of weld made on 1150 °C solution-treated base metal were maximum as compared to other weld joints.

8

Softening mechanism of P91 steel weldments using heat treatments

Pandey Chandan, Mahapatra Manas Mohan, Kumar Pradeep, Daniel F., Adhithan B.

Archives of Civil and Mechanical Engineering

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2019

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Vol. 19, no. 2

297--310

EN

The tungsten inert gas welded P91 steel welded joints were subjected to the two different type of heat treatments including the postweld direct tempering (PWDT) and re-austenitizing based tempering (PWNT) treatment. The microstructure of weld fusion and heat affected zone (HAZ) were characterized in different heat treatment conditions using optical microscope and scanning electron microscope. For as-welded joint, a great heterogeneity was observed in microstructure and mechanical properties across the weldments. The Charpy toughness of the as-welded joint was measured much lower than the minimum recommended value of 47 J and it was measured 8 ± 5 J. The PWHTs have found a beneficial effect in decreasing the microstructure heterogeneity across the welded joint and improving the mechanical properties. The PWDT resulted in a drastic improvement in the Charpy impact toughness of the welded joint and it was measured 59 ± 5 J which was higher than the minimum required value of 47 J but still inferior than the base metal. The δ ferrite still remained in overlap zone of the weld fusion zone. The PWNT treatment resulted in homogeneous microstructure and hardness variation across the welded joint in transverse direction and Charpy impact toughness (149 ± 6 J) exceeded than that achieved in base metal.

9

The Combined Influence of Molybdenum and Nickel in Steel Welds

Szczucka-Lasota B., Węgrzyn T., Kurc-Lisiecka A., Piwnik J.

Archives of Metallurgy and Materials

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2018

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Vol. 63, iss. 3

1087-1091

EN

Weld metal deposit (WMD) was carried out for standard MMA welding process. This welding method is still promising mainly due to the high amount of AF (acicular ferrite) and low amount of MAC (self-tempered martensite, retained austenite, carbide) phases in WMD. That structure corresponds with good impact toughness of welds at low temperature. Separate effect of these elements on the mechanical properties of welds is well known, but the combined effect of these alloy additions has not been analyzed so far. It was decided to check the total influence of nickel with a content between 1% to 3% and molybdenum with content from 0.1% up to 0.5%.

10

Mathemathical Equations of the Influence of Molybdenum and Nitrogen in Welds

Węgrzyn T., Kamińska J., Piwnik J., Stanik Z.

Archives of Metallurgy and Materials

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2018

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Vol. 63, iss. 1

83--86

EN

The paper offers mathematical equations of the influence of micro-jet cooling on structure and impact toughness properties of metal weld deposit. Weld metal deposit (WMD) was carried out for standard MIG welding and for MIG welding with micro-jet cooling. This new method is very promising mainly due to the high amount of AF (acicular ferrite) and low amount of MAC (selftempered martensite, retained austenite, carbide) phases in WMD. That structure corresponds with very good mechanical properties ie. good impact toughness of welds at low temperature. Micro-jet cooling after welding can find serious application in automotive industry very soon. Until that moment only argon, helium, nitrogen and gas mixtures of argon were tested for micro-jet cooling after welding. The best results of mechanical properties of WMD in presented welding method correspond with micro-jet argon cooling.

11

Prediction of Ferrite Content in Austenitic Cr-Ni Steel Castings During Production

Senberger J., Pernica V., Kana V., Zadera A.

Archives of Foundry Engineering

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2018

|

Vol. 18, iss. 3

91--94

EN

Determination of the ferrite content in austenitic steels, which solidified under defined conditions. Ferrite content in austenitic matrix was determined from samples with wall thickness of 60 mm. Measured ferrite contents served to propose the regression equations for the calculation of the ferrite content in steels with Cr content of 18 up to 22 % and Ni of 9 up to 11 %. An additional regression equation was proposed for steels with a higher Ni content. The proposed regression equations have been checked up on the operating melts. In conclusion, the ferrite content in the axis of the casting of wall thickness of 500 mm has been calculated and it was compared to the ferrite determined in the usual way from the cast-on test.

12

Ausferritic Microstructure Phase Analysis in Ductile Iron

Trzaskowski W., Nawrocki P., Łukasik K., Myszka D.

Archives of Foundry Engineering

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2018

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Vol. 18, iss. 2

112--116

EN

Image analysis allows to acquire a number of valuable quantitative informations on the observed structure and make appropriate conclusions. So far, a large part of analyzed images came only from light microscopes, where it was a possibility of accurately distinguish the different phases on the plane. However, the problem happened in the case of the observation of images obtained by scanning electron microscopy. In this case, the presence of various shades of gray, and the spaciousness of the image attained. To perform the analysis the matrix images of the ausferritic ductile iron were used. Full analysis was carried out using the computer program MicroMeter 1.03. Results obtained in the analysis were related directly to the results from X-ray diffraction. Obtained as a result of the analysis were related directly to the results from X-ray diffractometer. The following technique has weaknesses, including the misinterpretation by the operator microscope or program. After all, it was possible to obtain similar results to the result that has been obtained from X-ray diffractometer.

13

Napawanie elementów wymiennika ciepła austenitycznym drutem proszkowym

Rogalski G., Fydrych D., Prokop-Strzelczyńska K.

Przegląd Spawalnictwa

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2017

|

R. 89, nr 3

13--18

PL

Na potrzeby przemysłu energetycznego produkuje się wymienniki ciepła przeznaczone do eksploatacji w warunkach agresywnych chemicznie, np. w środowisku siarkowodoru. Z przyczyn ekonomicznych często stosuje się w takim przypadku materiały bimetaliczne wytwarzane procesami napawania. W artykule przedstawiono wyniki badań nieniszczących, pomiarów twardości, analizy składu chemicznego, pomiarów ferrytu delta oraz badań makro- i mikroskopowych próbek ze stali S355J2C+N napawanych drutem proszkowym o strukturze austenitycznej. Stwierdzono, że zastosowanie tego procesu umożliwia wykonanie warstw napawanych charakteryzujących się właściwościami spełniającymi założone kryteria.

EN

Heat exchangers designed for use in chemically aggressive environments, for example in a hydrogen sulfide, are produced for the energy industry. For this purpose, surfacing of materials is often used, mostly because it is an economical process. This article presents the results of non-destructive testing, hardness measurements, chemical composition analysis, delta ferrite measurements and macro and microscopic observations of specimens of S355J2C+N steel surfaced with austenitic flux-cored wire. It was found, that application of this process allows to perform surfaced layers characterized by properties that meet the established criteria.

14

Zmiany strukturalne w stali konstrukcyjnej wywołane epizodami jej nagrzewania i stygnięcia podczas pożaru

Maślak M., Żwirski G.

Bezpieczeństwo i Technika Pożarnicza

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2017

|

Vol. 48, iss. 4

34--52

PL

Cel: Celem artykułu jest krótkie omówienie podstawowych zagrożeń wynikających z epizodów nagrzewania i stygnięcia stali konstrukcyjnej podczas pożaru, które mogą warunkować ewentualne dalsze użytkowanie elementów nośnych z niej wykonanych. Zagrożenia te wiążą się na ogół z termicznie indukowanymi i trwałymi zmianami obserwowanymi w mikrostrukturze stali wystudzonej po zakończeniu ekspozycji na ogień, z reguły niedostrzeganymi wizualnie podczas klasycznej inwentaryzacji przeprowadzanej po pożarze, której celem jest ocena stanu technicznego obiektu. Metody: Struktura artykułu pozwala prześledzić kolejne, potencjalne formy zmian mikrostruktury stali konstrukcyjnej, najpierw inicjowane monotonicznym wzrostem temperatury tego materiału, a następnie mniej lub bardziej gwałtownym jego stygnięciem. W pierwszej kolejności omówiono skutki rozrostu ziaren ferrytu, w drugiej kolejności – efekty częściowej przemiany perlitu w austenit, a w końcu – zagrożenia determinowane zainicjowaniem w fazie chłodzenia przemiany bainitycznej i/lub martenzytycznej. Na tym tle podjęto dyskusję na temat konsekwencji ewentualnego powierzchniowego odwęglenia, a także możliwego wystąpienia zjawisk grafityzacji i/lub sferoidyzacji ziaren cementytu. Wyniki: Wykazano, że zmieniające się w czasie, a przy tym niekontrolowane oddziaływanie wysokiej temperatury pożaru na stal konstrukcyjną z dużym prawdopodobieństwem prowadzi do wystąpienia w tym materiale niekorzystnych przemian strukturalnych, które z reguły skutkują drastycznym zmniejszeniem się jego efektywnej ciągliwości skojarzonym z wyraźnym zwiększeniem się jego twardości. Taki zestaw cech stali w przypadku dalszego jej użytkowania po pożarze nieuchronnie implikuje dużą jej podatność na kruche pękanie, a co za tym idzie – znaczne ryzyko nagłego i niespodziewanego zniszczenia wykonanych z niej elementów. Wnioski: Klasyczna inwentaryzacja przeprowadzana po pożarze w celu oceny deformacji stalowego ustroju nośnego, uzupełniona jedynie o eksperymentalną weryfikację parametrów wytrzymałościowych charakteryzujących taką stal, nie wystarcza, by dostatecznie wiarygodnie wnioskować o przydatności tych elementów do ich dalszego użytkowania pod obciążeniem. Taka ocena musi być bowiem bezwzględnie poszerzona co najmniej o aposterioryczne badania mikrostruktury rozpatrywanego materiału oraz o próby pozwalające na sprawdzenie jego popożarowej twardości i udarności.

EN

Aim: The aim of this article is to provide a brief review of the basic hazards which might affect the potential re-use of bearing members made of structural steel following exposure to heating and cooling episodes in a fire. These hazards generally involve thermally induced and permanent changes observed in the microstructure of the steel after the fire is extinguished, usually not seen during a standard post-fire inventory aimed at assessing the technical condition of the building. Methods: The article’s structure guides the reader through the successive potential forms of changes in the microstructure of structural steel, initiated by a monotonic increase in the temperature of the material, and followed by its more or less rapid cooling. The article first discusses the effects of ferrite-grain growth, then proceeds to a description of the effects of a partial pearlite-to-austenite transformation, and finally addresses the threats created by the initiation of a bainitic and/or martensitic transformation during the cooling phase. In this context, it discusses the consequences of potential surface decarburisation and the results of the possible occurrences of graphitisation and/or spheroidisation of cementite grains. Results: It has been shown that the time-varying and uncontrolled impact on structural steel of a high fire temperature is likely to lead to the occurrence of unfavourable structural changes in this material, which usually result in a dramatic decrease in the effective ductility, coupled with a marked increase in hardness. In structural members re-used after a fire, such a set of features inevitably implies the high vulnerability of this type of steel to brittle fracture, and, consequently, carries a significant risk of the sudden and unexpected destruction of the components made of it. Conclusions: The standard post-fire inventory of member deformations in the steel-bearing structure, supplemented only by the experimental verification of such steel-strength parameters, is not sufficient to reasonably conclude that these members are suitable for re-use under load. Such an assessment must be extended at least by a detailed study of the microstructure of the material under consideration, made a posteriori, and also by tests which allow the verification of its post-fire hardness and impact strength.

15

The influence of ferrite particle size on the quality of the magnetic marker in shale gas hydraulic fracturing

Bogacki J., Zawadzki J.

Systemy Wspomagania w Inżynierii Produkcji

|

2016

|

z. 3 (15)

25--33

EN

The study analyzes the influence of particle size of magnetic ferrite on the possibility of using it, as a marker in magnetic prop pant during hydraulic fracturing. Based on a broad and accurate literature review, it was found, that the ferrite grain size can be one of the critical parameter conditioning the quality of the magnetic marker in shale gas hydraulic fracturing. Hence, the ferrite grain size determines greatly both the costs and efficiency of hydraulic fracturing.

PL

W pracy przeanalizowano wpływ wielkości ziarna ferrytu na możliwość zastosowania go, jako markera magnetycznego podczas szczelinowania hydraulicznego. Na podstawie szerokiego przeglądu dostępnej literatury, określono, że wielkość ziarna ferrytu może być kluczowym parametrem warunkującym jakość i właściwości markera magnetycznego stosowanego podczas szczelinowania hydraulicznego gazu łupkowego. Zatem, wielkość ziarna ferrytu wpływa zarówno na koszty jak i na efektywność szczelinowania hydraulicznego.

16

Structural and electrical properties of chromium substituted nickel ferrite by conventional ceramic method

Jahan N., Chowdhury F. U. Z., Zakaria A. K. M.

Materials Science Poland

|

2016

|

Vol. 34, No. 1

185--191

EN

Polycrystalline Cr substituted Ni ferrites [NiCrxFe2-xO4 (0.0 ≤ x ≤ 1.0)] were synthesized by conventional ceramic method and sintered at 1350 degrees C in air. X-ray diffraction (XRD) patterns showing sharp peaks confirmed the formation of single phase cubic spinel structure. The lattice parameters of the samples were determined from the XRD data using Nelson-Riley extrapolation technique. They were found to decrease with increasing Cr concentration obeying Vegard's law. X-ray density, bulk density and porosity were also calculated from the XRD data. The variation of DC resistivity with temperature was measured by two-probe method. The DC resistivity was found to decrease with increasing temperature indicating the semiconducting nature of the samples. Activation energy was calculated from the Arrhenius plot. AC resistivity, dielectric constant and loss tangent were measured in the frequency range of 1 kHz to 120 MHz at room temperature.

17

Analytical description of power losses in a transformer operating in the dual active bridge converter

Barlik R., Nowak M., Grzejszczak P., Zdanowski M.

Bulletin of the Polish Academy of Sciences. Technical Sciences

|

2016

|

Vol. 64, nr 3

561--574

EN

The paper presents an analytical approach to the determination of power losses in a high-frequency transformer operating in the dual active bridge (DAB). This transformer, having two single-phase transistor bridge inverters, couples two DC circuits that significantly differ in voltages (280 V and 51 V ±20%). Power losses in the core and windings of the planar transformer 5600 VA /100 kHz were calculated taking into account changes in the value and direction of the energy flow between the coupled DC circuits. These circuits represent storage or renewable energy sources and intermediate circuits of the converters used in distributed generation systems. Calculations were performed using the Steinmetz’s and Dowell’s equations. The analytical results have been verified experimentally.

18

Development and validation of a quantitative dilatometric analysis model of austenite decomposition into ferrite and pearlite

Opara J., Wrożyna A.

Prace Instytutu Metalurgii Żelaza

|

2015

|

T. 67, nr 4

24--32

EN

The quantitative dilatometric analysis model for the austenite decomposition into ferrite and pearlite during continuous cooling treatment is presented. It is based on measurements of a relative length change of a sample during the progress of phase transformations and calculations of the difference in atomic volume of present phases. The proposed model incorporates crucial effects accompanying the austenite decomposition, i.e. the carbon enrichment of the remaining austenite during ferrite formation, which causes an increase in the definite atomic volume of austenite, while formation of pearlite has a clearly different impact with the volume fractions of cementite and ferrite regulated by constant carbon composition inherited from austenite (enriched in carbon). The analysis results are compared with quantitative microstructure analysis and an excellent convergence has been found. Depicted results state a convincing confirmation that the model is correctly developed by the authors. Additionally, kinetics of phase transformations as function of normalized time were analyzed and a process of carbon enrichment of austenite was demonstrated.

PL

W niniejszej pracy zaprezentowano model ilościowej analizy dylatometrycznej dla rozpadu austenitu w ferryt i perlit podczas ciągłego chłodzenia. Rozwiązanie bazuje na pomiarach względnej zmiany długości próbki w trakcie postępu przemian fazowych oraz obliczeniach różnic objętości atomowych występujących faz. Zaproponowany model uwzględnia kluczowe zjawiska towarzyszące rozpadowi austenitu, tzn. wzbogacanie się austenitu w węgiel podczas powstawania ferrytu, które powoduje wzrost określonej objętości atomowej austenitu, podczas gdy formowanie się perlitu ma wyraźnie odmienny wpływ poprzez udziały objętościowe ferrytu i cementu, które wynikają z ustalonej zawartości węgla dziedziczonej z austenitu (wzbogaconego w węgiel). Rezultaty ilościowej analizy dylatogramów zestawiono z ilościową analizą mikrostruktur i uzyskano doskonałą zbieżność wyników. Przedstawione wyniki stanowią wyraźne potwierdzenie, iż model jest poprawnie opracowany przez autorów. Ponadto, przeprowadzono analizę kinetyk przemian fazowych w funkcji znormalizowanego czasu oraz przedstawiono proces wzbogacania austenitu w węgiel.

19

Badania struktury i naprężeń własnych w grzybkach zaworów silników spalinowych

Samolczyk J., Pachutko B., Gralak E., Woźniak H.

Obróbka Plastyczna Metali

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2015

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T. 26, nr 3

219--228

PL

W pracy przedstawiono wyniki badań przeprowadzonych na talerzykach zaworów w stanie przed nałożeniem i po nałożeniu powłoki chromowej na trzonek zaworu silnika spalinowego. Badane zawory silnikowe wykonano w całości ze stali zaworowej X45CrSi9-3 (1.4718) w procesie elektrospęczania i procesie kucia na gorąco. Fazowany pręt jest nagrzewany indukcyjnie i spęczany, a po tym zabiegu umieszczany jest w matrycy i odkuty. Tak przygotowany zawór trafia do pieca, gdzie jest wygrzewany w temperaturze 800oC w celu usunięcia naprężeń, jakie powstały podczas procesu kucia. Ostatnią z operacji jest proces indukcyjnego hartowania przylgni talerzyka, który ma na celu zwiększenie twardości tego elementu [1–3]. Kształtowanie zaworów z wykorzystaniem procesu elektrospęczania i kucia na gorąco mimo, że od dawna jest powszechnie stosowane, to często nastręcza producentom silników wiele trudności technologicznych. Przeprowadzono pomiary naprężeń własnych metodą rentgenowską, badania mikro-struktury za pomocą skaningowego mikroskopu elektronowego oraz pomiary twardości. Uzyskano informacje, czy proces technologiczny wpływa na powstawanie dużych dodatnich naprężeń własnych; odkształcanie na gorąco i prędkość odkształcenia wywołują niejednorodność mikrostruktury i są źródłem naprężeń własnych w przekroju poprzecznym talerzyka zaworu. Stwierdzono, że nie ma istotnych różnic w stanie naprężeń własnych, powstałych na skutek zmian strukturalnych w talerzyku zaworu, w stanie przed nałożeniem i po nałożeniu powłoki chromowej na trzonek zaworu.

EN

The present paper presents the results of studies conducted on valve disks before and after deposition of a chromium coat onto the stem of an ICE poppet valve. Studied poppet valves were made entirely of X45CrSi9-3 valve steel (1.4718) in the process of electro-upsetting and in the process of hot forging. A chamfered rod is heated by induction and upset forged, and after this process, it is placed in a die and forged. A valve prepared in this way is placed in a furnace, where it is held at a temperature of 800oC in order to remove stresses created during the forging process. The final operation is the process of quenching the seat face of the disk by induction, which has the purpose of increasing the hardness of this component [1–3]. Despite the fact that valve shaping using the electro-upsetting and hot forging process has been universally applied for a long time, it often poses many technological difficulties for engine manufacturers. Measurements of internal stresses were conducted using the X-ray method, microstructure investigations were carried out using a scanning electron microscope, and hardness measurements were conducted. Information was obtained on whether the technological process has an impact on the creation of large positive internal stresses; hot deformation and strain rate cause heterogeneity of the microstructure and are the source of internal stresses in the valve disk’s cross-section. It was stated that there are not significant differences in the state of internal stresses created as a result of structural changes in the valve disk, in a state before and after deposition of a chromium coat onto the valve stem.

20

Structural and dielectric studies of Mg2+ substituted Ni-Zn ferrite

Prasad B. B. V. S. V., Babu B R., Prasad M. S. R.

Materials Science Poland

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2015

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Vol. 33, No. 4

806--815

EN

Polycrystalline ferrites having the chemical formula Ni0.65-xZn0.35MgxFe2O4 (0 ≤ x ≤ 0.2) were prepared by solid state reaction route in steps of x = 0.04. The effect of incorporation of diamagnetic divalent magnesium at expense of nickel on the structural properties of these ferrites has been studied. The proposed cation distribution was derived from theoretical X-ray diffraction intensity calculations. These intensity calculations were done by varying the concentration of magnesium ions over two sites in the lattice. For a certain amount of magnesium concentration, the calculated and observed X-ray diffraction intensities were found to be in good agreement. Site occupancy of divalent diamagnetic magnesium was established from this cation distribution. The octahedral environment facilitates magnesium to enter the B-site at about 95 % and the remaining 5 % occupy tetrahedral sites (A-sites). The movements of cations between tetrahedral and octahedral sites as a result of magnesium substitution were discussed in the view of structural parameters, such as tetrahedral and octahedral bond lengths, cation-cation and cation-anion distances, bond angles and hopping lengths, which were calculated using experimental lattice constants and oxygen parameters. All structural parameters showed slight deviations from ideal values. Among all magnesium substituted samples, the ones with x = 0.12 exhibited insignificant variation in view of structural properties. Dielectric measurements were conducted at a standard frequency of 1 kHz. Large values of the recorded dielectric constants displayed typical characteristics of bulk ferrites. Both dielectric constant and loss values showed mixed variations, attributed to the loss of zinc ions during the sintering process.