Wyniki wyszukiwania - Biblioteka Nauki

1

Zmiany struktury i właściwości w procesie spawania stopu Fe-30Ni

100%

Ciura F. , Tasak E. , Dubiel B.

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2006

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tom R. 78, nr 5-6

50-52

PL

W stopach żelaza z niklem istnieje możliwość kształtowania struktury poprzez zmiany udziału objętościowego austenitu i martenzytu, jak również morfologii martenzytu w zależności od zastosowanej obróbki cieplno--plastycznej. Takie zróżnicowanie struktury ma decydujący wpływ na właściwości stopu i zwiększa jego możliwości aplikacyjne. Przeprowadzono analizę struktury w strefie wpływu ciepła spoin wykonanych na próbkach stopu Fe-30Ni poddanego uprzednio różnym obróbkom cieplno-plastycznym. W materiale po przesycaniu spawanie metodą TIG nie powoduje istotnego wzrostu wielkości ziarna w strefie przyspoinowej. Odmienną strukturę obserwowano natomiast w próbkach uprzednio odkształconych. Wewnątrz strefy grubych ziaren występowały drobne ziarna w pobliżu linii wtopienia. Taka struktura tworzy się w procesie rekrystalizacji austenitu dziedziczącego defekty struktury martenzytycznej.

EN

The structure of Fe-Ni alloys can be tailored by changing of the austenite and martensite volume fractions as well as by the change of the martensite morphology, depending on the thermo-mechanical treatment applied. A wide range of microstructures enables to achieve different properties of the alloy and increases possibility of its application. In the present work the analysis of the structure in heat-affected zone of welded Fe-30Ni alloy after different thermo-mechanical treatments was performed. In solution treated material welding by TIG method does not influence the pronounced increase of grain size close to welded zone. The different structure was observed in previously deformed specimens. Inside the zone of coarse grains the fine grains were observed close to the melting line. Such a structure is formed during recrystallization of the austenite inheriting the defects of the martensitic structure.

2

Heat treatment and mechanical properties of low-carbon steel with dual-phase microstructure

84%

Adamczyk J. , Grajcar A.

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2007

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tom Vol. 22, nr 1

13-20

EN

Purpose: The aim of the paper is to design heat treatment conditions of dual-phase steel and to determine their influence on the structure and mechanical properties of steel. Design/methodology/approach: The heat treatment of the C-Mn steel in order to obtain a dual-phase ferritic-martensitic structure of desirable phase fractions was realized. To investigate the influence of heat treatment parameters on the structure light and transmission electron microscopy methods were used. Mechanical properties were determined by means of tensile test. A strain hardening exponent as a function of true strain was evaluated, too. Findings: It was found that an initial structure influences essentially the morphology of martensite in an obtained dual-phase structure. It can occur as a network, fine fibres or islands in a ferritic matrix of high dislocation density in the vicinity of diffusionless transformation products of austenite. The best combination of strength and ductile properties has a steel with the martensite in a form of fine fibres. Research limitations/implications: Investigations concerning using the thermomechanical treatment to obtain a ferritic-martensitic structure of steel are required. Practical implications: The established heat treatment conditions can be useful for manufacturing dual-phase structure sheets characterized by high strength and ductile properties as well as a good suitability for metal forming operations. Originality/value: The relationship between the initial structure and martensite morphology in dual-phase steels was specified.

3

Austenite steel transformations under the influence of fatigue loading

84%

Skibicki D. , Dymski S.

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2008

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tom Vol. 8, iss. 3

93-98

EN

Behavior of materials and structures in fatigue non-proportional loading conditions, characterized by the principal axes rotation during fatigue cycles, is an important issue because of its impact on fatigue properties. The article presents results of an analysis of microstructural steel X5CrNi18-10, subjected to proportional fatigue loadings: torsion and push-pull, as well as non-proportional ones. Variability of the principal axes positions of non-proportional loadings was obtained by using a loading program with alternately realized torsion and tension-compression blocks. The work includes an analysis of one-phase microstructure and microhardness tests of fatigue samples were carried out. The cyclic loading value accepted for the tests caused an martensite transformation induced by plastic strain and occurrence of slip bands in the grains of austenite. A comparative analysis revealed differences in the transformation intensity, depending on the type of applied loading and on the degree of its non-proportionality.

4

The remelting of the surface layer of C15 steel with an electric arc

84%

Adamiak S.

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2008

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tom Vol. 8, iss. 3

5-10

EN

This study presents results of a research on enhancing properties of the surface layer of C15 steel by treating it with a concentrated heat stream utilizing the GTAW method. Remelting of the surface layer of C15 steel was performed by a welding head moving with a constant speed of 200 mm/min and varying current intensity of the electric arc ranging from 50A to 300A as well as with a constant current intensity of the electric arc and a varying speed of the welding head ranging from 200 mm/min to 800 mm/min. Metallographic evaluations (LM and SEM) of the resulting structure were performed as well as measurement of the hardness of the remelted layers. Correlation between current intensity of the electric arc and its speed in relation to the treated material sample and the geometry of the remelted layers and their microhardness was established.

5

Austenite-Martensite Transformation in Austempered Ductile Iron

84%

Myszka D.

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2007

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tom Vol. 52, iss. 3

475-480

EN

Austempered ductile iron, commonly known as ADI, has already gained some renown among producers and users of castings made from this material. Though famous nowadays, its properties are being improved all the time and studies are continued to better know the mechanisms that govern obtaining the properties so unusual for a material like cast iron. From the research carried out by the author of this publication it follows that at least some of the properties result from the phenomenon that is called martensitic transformation and that accompanies the formation of ADI at different stages of its manufacture and during the additional technological operations. In ADI microstructure, martensite is always the product of austenite transformation, and for this reason mainly an attempt has been made in this paper to describe this phase in more detail as well as various consequences of its presence in cast iron under different conditions.

PL

Żeliwo ADI w dzisiejszych czasach ma już swoją renomę zarówno wsród producentów, jak i odbiorców odlewów wykonanych z tego materiału. Nadal jednak ulepszane są jego właściwości oraz poznawane są mechanizmy umożliwiające uzyskiwanie niezwykłych dla żeliwa właściwości. W świetle badań prowadzonych przez autora niniejszej publikacji wynika, że niezwykle istotny wpływ na część z nich ma przemiana martenzytyczna, która będzie towarzyszyć powstawaniu ADI w różnych fazach jego produkcji oraz innych, dodatkowych zabiegach technologicznych. Martenzyt jest zawsze wynikiem przemiany austenitu w mikrostrukturze ADI, stąd w artykule podjęto próbę opisu tej fazy i konsekwencji jej występowania w różnych stanach.

6

Structure of carbon steels after remelting of the surface layer with the electric arc

84%

Adamiak S.

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2009

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tom Vol. 9, iss. 2

181-184

EN

This study presents results of a research on the enhancement of properties of the surface layer of carbon steels by treating it with a concentrated heat stream utilizing the GTAW method. Remelting of the surface layer of studied steels was performed by a welding head moving at a constant speed of 200 mm/min and varying current intensity of the electric arc ranging from 50A to 300A as well as with a constant current intensity of the electric arc and a varying speed of the welding head ranging from 200 mm/min to 800 mm/min. Metallographic evaluations (LM and SEM) of the resulting structure were performed. Correlation between the current intensity of the electric arc and its speed in relation to the treated material sample and the geometry of the remelted layers and their structure was established.

7

TDA method application to austenite transformation in nodular cast iron with carbides assessment

67%

Gumienny G.

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2011

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tom Vol. 11, iss. 3

159-166

EN

In this paper the possibility of TDA method using to austenite transformation in nodular cast iron with carbides assessment is presented. Studies were conducted on cast iron with about 2% molybdenum and 0,70% to 4,50% nickel. On diagrams, where TDA curves are presented, on time axis a logarithmic scale was applied. It has not been used up to now. It was found, that during cooling and crystallization of cast iron in TDA probe, on the derivative curve there is a slight thermal effect from austenite to upper bainite or martensite transformation. Depending on nickel concentration austenite upper bainite transformation start temperature changed (Bus), while MS temperature was independent of it. An influence of nickel on eutectic transformation temperature in nodular cast iron with carbides was determined too.

8

Efekt stabilizacji austenitu przez wodór w stopie Fe-Ni.

67%

Sozańska M.

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2002

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tom R. XXIII, nr 3

129-135

PL

Badania stabilizacji austenitu przez wodór w stopach Fe-32,06 Ni (% wagowy) prowadzono przy użyciu metod metalografii ilościowej i testów elektrochemicznych potencjostatycznych. Badany stop Fe-Ni wykazuje duże możliwości absorpcji wodoru, którego obecność modyfikuje przebieg przemiany martenzytycznej. W badaniach wykazano, że w całym zakresie temperatur hartowania (od Ms=-45 stopni Celsjusza do -196 stopni Celsjusza) różnica pomiędzy udziałem objętościowym austenitu dla próbek nawodorowanych i bez wodoru, jest stała. Ponadto wykazano, że powierzchnia rozdziału pomiędzy martenzytem i austenitem dla grup igieł martenzytu Sv jest najlepszym parametrem opisującym granicę rozdziału pomiędzy martenzytem i austenitem w badanym stopie. Znaleziono ogólną relację, w postaci równania liniowego, łączącą parametr otrzymany metodami metalografii ilościowej (powierzchnia rozdziału między martenzytem i austenitem dla grup igieł Sv) z parametrem z testów elektrochemicznych (gęstość prądu stacjonarnego I) dla próbek austenitycznych nawodorowanych lub nie przed hartowaniem.

EN

Experiment based on quantitative metallography methods and electrochemical potentiostatic tests were performed with particular attention to the influence of hydrogen on the stabilization of austenite of Fe-32.06 wt% Ni alloy. This alloy exhibits great hydrogen absorption capacity (25 ppm) and its presence modifies the martensitic transformation. In the whole range of the quenching temperatures (from Ms=-45 degrees centigrade to -196 degrees centigrade), the difference between the volume fraction of martensite, measured on specimens with hydrogen or without hydrogen, is constant. It was found that the value of the interface area for the martensite needles groups Sv is the best parameter describing the interface between martensite and austenite in this alloy. It was also found that there is general relationship, expressed by a linear function, between the parameter obtained by metallography methods (interface area between martensite and austenite Sv) and the result obtained by electrochemical tests (current density I) for hydrogenated or not hydrogenated austenite specimens before quenching.

9

Effect of the concentrated heat flow treatment on the structure and the antiwear properties of cast iron

67%

Orłowicz W. , Shevelya V. , Trytek A. , Kirilkov V.

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2009

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tom Vol. 9, iss. 2

185-188

EN

The influence of modes of surface fusion by electric arc plasma (GTAW method) on the hardness and wear-resistance of plain cast iron was studied. A possible mechanism of structural rearrangement in the processed material during the friction was analyzed. This mechanism is determined by specific behaviour of hardened martensitic structure under dynamic load. This martensitic structure forms a metal basis of cementite eutectic under conditions of fast crystallisation.

10

Badania strukturalne mechanizmu odkształcenia na zimno stali przez zgniatanie obrotowe

67%

Stępień J.

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2007

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tom Vol. 27, nr 1

169-177

PL

Zgniatanie obrotowe na zimno stali niskowęglowej Cr-Mn-Mo-V stosuje się w celu uzyskania w wyrobie gotowym bardzo drobnej struktury. Uzyskanie bardzo drobnej struktury pozwala na podwyższenie właściwości wytrzymałościowych wyrobu gotowego przy bezpiecznym poziomic wydłużenia A5 powyżej 10%. Zgniatanie obrotowe wykonano na dwóch stanowiskach: na stanowisku doświadczalnym FPS Bolechowo, stosując stal wytapianą z zastosowaniem pozapiecowej obróbki próżniowej VAD, i na stanowisku produkcyjnym niemieckiej firmy MSR, stosując stal przetapianą elektrożużlowo EŻP. Stwierdzono, że mikrostruktura stali EŻP jest bardziej jednorodna i bardziej drobnoziarnista niż stali VAD, zarówno po ulepszaniu cieplnym jak i po zgniataniu obrotowym na zimno. Niskowęglowa stal Cr-Mn-Mo-V po hartowaniu z temperatury 970°C i odpuszczaniu w temperaturze ok. 660°C ma wydłużenie A5 od 12,0 do 12,9% przy Rm od 1114 do 1154 MPa i spełnia założone kryteria: przy Rm = 1080 + 1280 MPa A5≥ > 10. Po odkształceniu na zimno wytrzymałość tej stali wzrasta do ok. 1500 MPa.

EN

Microstructure low-carbon Cr-Mn-Mo-V electro-slag remelted (ESR) steel was more homogenous and more fine-grained than vacuum argon decarburization (VAD) steel. The same was found after quenching and tempering and after cold rotary extrusion. Also, ESR steel has more lower banding structure introduced by segregation of chemical composition (major C and Mn). After cold rotary extrusion on the experimental stand of FPS and industry stand of MSR, both VAD and ESR steels had a fine-structure, witch was composed of thin lath tempered martensite. In the structure deformation bands appeared arranged in space in different directions and carbides of chromium and molybdenum type M6C (this carbides often were found in the VAD steel) and carbides vanadium type MC. The fine laths of martensite received in the ESR steel were deformed on the industry stand MSR. The low-carbon Cr-Mn-Mo-V steel after quenching from 970°C and tempering at about 660°C has elongation A5 = from 12.6 to 12.9% and strength Rm = from 1114 to 1154 MPa and fulfils criteria of standards: Rm - from 1080 to 1280 MPa, A5 ≥ 10. After cold rotary extrusion strength incrased to about 1500 MPa.

11

Obliczenia numeryczne symulacji termokinetyki przemian fazowych nawęglanej, hartowanej stali

67%

Woelke J.

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2000

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tom Nr 47

97-107

PL

Praca zawiera opis numerycznej metody analizy termokinetyki przemian fazowych nawęglanych stalowych cylindrów o przekroju okrągłym poddanych procesowi hartowania. W rozwiązaniu wykorzystano metodę wariacyjno-różnicową będącą połączeniem metody elementu skończonego i metody różnicowej. Program obliczeń numerycznych dotyczy tylko tych gatunków stali, które mają krzywe C-T-P w kształcie litery C. Rozważania oparto na teorii Sjöströma oraz na modelu Hildenwalla. Wykorzystano prace Avramiego oraz teorię Inoue-Ranieckiego. Wyznaczono rozkład pól temperatury, udziały objętościowe poszczególnych struktur i faz w funkcji czasu oraz względną zmianę objętości Uzyskane wyniki stanowią podstawę do szacowania rozkładu pól naprężeń chwilowych i szczątkowych.

EN

The paper disusses a numerical method of phase transformation termokinetics for infinite length carburiset cylindrical machine elements made of steel grade. The solution of the problem is based on the variational-finited difference method, being a combination of the finite element method (FEM) and the finite difference method (FDM). The elboratrd program of numerical calculations refers to steel grades that are characterized by C-shaped T-T-T curves. The analysis uses the theoretical background elaborad by Sjöström and Hildenwall. Also the work of Avramiego and Inoue- Raniecki theory is used in this paper. The temperature field and the weight fractions of particular Structeres and phases and the relative volumetric dilatation are determinated in the paper. The relative volume fraction is the base to estimate the instantaneous and residual stresses.

12

Micro- and nano- structural observations of the surface layer of hardened bearing steel.

59%

Barbacki A. , Kozubowski J. A. , Kawalec M.

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1998

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tom R. XIX, nr 4

978-981

EN

The paper presents the results of TEM and HREM investigations of the surface layer produced in a hardened 1% C, 1.5% Cr steel by dry machining. The investigations have revealed extremly small micro- and nano- grains probably resulting from large plastic deformation accompanied by localised stress-induced martensite to ferrite transformation and dynamic recovery.