Wyniki wyszukiwania - Biblioteka Nauki

1

Relation of structure and mechanical properties of austempered ductile iron

100%

Podrábský T. , Věchet S. , Kohout J.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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1999

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tom z. 59

91-94

EN

The purpose of the study is to find out the relations among structure, mechanical properties, chemical composition and conditions of heat treatment of austempered ductile iron (ADI). The study is directed to obtain the best combination of strength and plastic properties of this ADI. Knowledge obtained from the study of mention characteristics creates the main basis for practical technical application of ADI. Sructure and mechanical properties of ADI are specially influenced by the conditions of heat treatment. Temperature and duration of the isothermal transformation has a special influence on the resulting structural mixture of ADI matrix and, therefore, in the same time on its mechanical properties [1]. In the study we concentrate to the structural - mechanical characteristics of ADI in dependence on the temperature of isothermal transformation in the range of 380 - 500 C.

2

ADI - a prospective structural material

80%

Dorazil E. , Věchet S. , Kohout J. , Klakurková L.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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1999

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tom z. 59

103-106

EN

Austempered ductile iron (ADI) presents relatively new high strength structural material with very good mechanical and technological properties along with relatively low price (see Fig. 1). This type of nodular cast iron is produced in wide measure not only in large and developed countries (U.S.A. - full half of world-wide production, Japan, China, Germany, Great Britain, France, Italy, Sweden etc.) but also in countries comparable with our country (Finland, Netherlands, Belgium etc.). Word-wide production per year exceeded 60,000 tons in 1995 [1], in 2005 already the production of 230,000 tons is expected (Fig. 2).

3

Influence of transformation temperature on fatigue properties of ADI

80%

Věchet S. , Kohout J. , Podrábský T.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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1999

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tom z. 59

87-90

EN

Structure and mechanical properties of austempered ductile iron (ADI) are in a pronounced way influenced by the conditions of heat treatment. While conditions of austenitization are not manifested in a special way, coditions of isothermal transformation have a very substantial influence on the resulting structural matrix mixture, and so at the same time on its mechanical properties. In the work the influence of the temperature of isothermal transformation in the range 380-500 C above all on the fatigue properties of ADI is studied.

4

The mystery of ADI

60%

Krzyńska A. , Kaczorowski M.

Archives of Foundry Engineering

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2007

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tom Vol. 7, iss. 4

111-114

EN

The considerations of ADI strengthening mechanisms based on results of previous structure investigations are presented. The aim of this elaboration was to discuss which mechanism looks to be most responsible for strengthening of ADI. It was concluded that the high strength of ADI which matrix consist mostly ferrite, austenite and sometimes some amount of martensite is caused by strengthening these three phases. Neglecting high carbon martensite which strength properties are nothing surprising, it is proposed that different mechanism of strengthening are responsible for ferrite and austenite strength increase. In case first of these phases strengthening is caused mainly by strain hardening. It is evidenced with very high dislocations and dislocation loops density which are typical in case of ferrite grains. The mechanism of austenite strengthening is more complicated. First of all hardening of austenite is connected with high supersaturation with carbon. The effect of strengthening is additionally increased with grains refinement caused by twinning and formation of stacking faults. The first of them supply extra coherent grain boundaries and the second lead to distortion of perfect lattice structure. It looks from the analysis, that strengthening rather soft and ductile phases which are ferrite and austenite is high enough to explain high strength properties of ADI.

5

Microadditions of boron and vanadium in ADI. Part 2. Own investigations

51%

Pirowski Z. , Wodnicki J. , Olszyński J.

Archives of Foundry Engineering

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2007

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tom Vol. 7, iss. 1

171-174

EN

In the second part of the study, describing the role of vanadium and boron microadditions in the process of structure formation in heavy-walled castings made from ADI, the results of own investigations were presented. Within this study two series of melts of the ductile iron were made, introducing microadditions of the above mentioned elements to both unalloyed ductile iron and the ductile iron containing high levels of nickel and copper (the composition typical of ADI). Melts were conducted with iron-nickel-magnesium master alloy. Thermal analysis of the solidification process of the cast keel blocks was conducted, the heat treatment of the alloys was carried out, and then the effect of the introduced additions of boron and vanadium on the hardenability of the investigated cast iron was examined and evaluated.

6

Mechanical properties and structure of austempered ductile iron -ADI

51%

Kaczorowski M. , Krzyńska A.

Archives of Foundry Engineering

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2007

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tom Vol. 7, iss. 1

161-166

EN

The results of experimental study of austempered ductile iron are presented. The aim of the investigations was to look closer into the structure – mechanical properties relationships of this very attractive cast material. The experiment was carried out with 500 7 grade ductile iron, which was austempered using different parameters of heat treatment. The specimens were first solution treated 1 hour in 910°C and then isothermally quenched for different time in silicon oil bath of temperature 275, 325, 300 and 350°C. The mechanical properties heat treated specimens were tested in tensile to evaluate yield stress R_e, 0.2, tensile strength R_m and elongation A_10. Additionally hardness of heat treated samples was measured using Brinell-Rockwell hardness tester. Structure of the specimens was studied either with conventional metallography, scanning (SEM) and transmission (TEM) electron microscopy. It followed from the study that conventional grade ductile iron enabled to produce both low and high strength ADI, depend on heat treatment parameters. As expected the low temperature isothermal quenching produced higher strength ADI compare to the same ductile iron but austempered at 350°C. It was discovered however, that low yield strength ADI obtained for short time quenching at 275°C exhibited high strengthening effect while strained in tensile. So it was concluded that this had to by cause by large amount of untransformed austenite, which FCC lattice is characterized by high strengthening coefficient.

7

Microadditions of boron and vanadium in ADI. Pt 2. Own investigations

51%

Pirowski Z. , Wodnicki J. , Olszyński J.

Prace Instytutu Odlewnictwa

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2008

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tom T. 48, z. 3

49-56

EN

In the second part of the study, describing the role of vanadium and boron microadditions in the process of structure formation in heavy-walled castings made from ADI, the results of own investigations were presented. Within this study two series of melts of the ductile iron were made, introducing microadditions of the above mentioned elements to both unalloyed ductile iron and the ductile iron containing high levels of nickel and copper (the composition typical of ADI). Melts were conducted with ironnickel-magnesium master alloy. Thermal analysis of the solidification process of the cast keel blocks was conducted, the heat treatment of the alloys was carried out, and then the effect of the introduced additions of boron and vanadium on the hardenability of the investigated cast iron was examined and evaluated.

PL

W drugiej części pracy, opisującej rolę mikrododatków wanadu i boru w procesie kształtowania się struktury grubościennych odlewów z żeliwa ADI, omówiono wyniki przeprowadzonych badań własnych. W ramach pracy wykonano dwie serie wytopów żeliwa sferoidalnego wprowadzając mikrododatki tych pierwiastków zarówno do niestopowego żeliwa sferoidalnego, jak też do żeliwa zawierającego zwiększoną zawartości niklu i miedzi (skład typowego żeliwa ADI). Wytopy prowadzono stosując zaprawy żelazowo-niklowo-magnezowe. Przeprowadzono analizę termiczną procesu krzepnięcia odlewanych wlewków, wykonano obróbkę cieplną otrzymanych stopów, a następnie oceniono wpływ wprowadzanych dodatków boru i wanadu na hartowność badanego żeliwa.

8

Określenie przewodności cieplnej wybranych gatunków żeliwa sferoidalnego za pomocą pomiaru przewodnictwa temperaturowego metodą Laser-Flash

51%

Gazda A. , Homa M.

Prace Instytutu Odlewnictwa

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2009

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tom T. 49, z. 2

5-18

PL

W pracy przedstawiono wyniki pomiarów przewodnictwa temperaturowego w funkcji temperatury dla dwóch gatunków żeliwa sferoidalnego przy zastosowaniu jednego z najnowocześniejszych zestawów aparaturowych LFA 427 (Laser Flash Apparatus) firmy Netzsch. Do pomiaru ciepła właściwego c[sub]p(T) i gęstości p(T) wykorzystano metody dynamicznej analizy termicznej - różnicową kalorymetrię skaningową DSC i technikę dylatometryczną, co pozwoliło na obliczenie współczynników przewodzenia ciepła λ(T) za pomocą oprogramowania Netzsch LFA Analysis. Zaobserwowano zmiany nachylenia krzywej zależności przewodnictwa temperaturowego od temperatury oraz gwałtowną zmianę przebiegu przewodności cieplnej λ(T) wywołaną przez efekt cieplny, zarejestrowany na krzywej C[sub]p(T). Pozwoliło to na identyfikację procesu dekompozycji struktury ausferrytycznej, polegającego na rozpadzie wysokowęglowego austenitu w żeliwie ADI w temperaturze ok. 400°C.

EN

This paper presents the results of measurements of thermal conductivity coefficient as a function of temperature for two species of spheroidal cast iron by using one of the most modern experimental sets LFA 427 (Laser Flash Apparatus) produced by Netzsch Company. In order to measure the specific heat c[sub]p(T) and density p(T), two methods of dynamic thermal analysis were used - differential scanning calorimetric DSC and dilatometric technique. Based on results of these measurements the coefficients of thermal conductivity were calculated with the use of Netzsch LFA Analysis software. Changes of slope of thermal diffusivity coefficient curvilinear dependence on temperature were observed, as well as rapid change on thermal conductivity λ(T) caused by thermal effect registered on c[sub]p(T) dependence. These observations allowed to identify decomposition process of ausferrite, caused from the disintegration of high-carbon retained austenite in ADI cast iron at approximately 400°C.

9

Neural network analysis of tensile strength of austempered ductile iron

51%

Ławrynowicz Z. , Dymski S. , Trempczyńska-Łent M. , Giętka T.

Archives of Foundry Engineering

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2007

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tom Vol. 7, iss. 3

99-104

EN

The neural technique was applied to the analysis of the ultimate tensile strength and additionally the yield strength of austempered ductile iron (ADI). Austempered ductile iron is an excellent material and it possesses attractive properties as high strength, ductility and toughness. This paper begins with an introduction to neural networks and demonstrates the ability of the method to investigate new phenomena in cases where the information cannot be accessed experimentally. The model allows the strength properties to be estimated as a function of heat treatment parameters and the chemical composition. A 'committee' model was used to increase the accuracy of the predictions. The model was validated by comparison its predictions with data of tensile tests experiments on austempered samples of ductile cast iron. The model successfully reproduces experimentally determined ultimate tensile strength and it can be exploited in the predictions of both ultimate and yield strength and in the design of chemical composition of cast irons and their heat treatments.