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Wykrywanie pęknięć hartowniczych w stali łożyskowej 100Cr6 metodą prądów wirowych

Kondej Adam, Jończyk Sylwester, Lasota Piotr

Welding Technology Review

|

2023

|

R. 95

87--93

PL

W artykule opisano wyniki badań w zakresie identyfikacji i lokalizacji pęknięć hartowniczych w stali łożyskowej 100Cr6 z wykorzystaniem autorskiego urządzenia kontrolno-pomiarowego do badań nieniszczących metodą prądów wirowych Wirotest M2 oraz automatycznego stanowiska AutoWir-S1. Do badań zastosowano głowicę stykową o częstotliwości 861 kHz. System rejestrował zmiany amplitudy napięcia oraz częstotliwości rezonansowej. Wyraźny spadek wartości obydwu parametrów wskazywał na obecność nieciągłości. Efekt krawędziowy powodował wzrost amplitudy napięcia oraz spadek częstotliwości, jednakże zmiany te nie wpłynęły na detekcję pęknięć. Najmniejsze wykryte pęknięcie charakteryzowało się maksymalną szerokością około 20 μm i było niewidoczne okiem nieuzbrojonym. Uzyskane wykresy powierzchniowe jednoznacznie obrazują przebieg oraz lokalizację poszczególnych nieciągłości.

EN

The article describes the results of research on the identification and localization of quenching cracks in 100Cr6 bearing steel using a proprietary non-destructive testing device based on the eddy current method called Wirotest M2 and an automatic stand AutoWir-S1. A surface probe with a frequency of 861 kHz was used for the tests. The system recorded changes in voltage amplitude and resonant frequency. A significant decrease in both parameters indicated the presence of discontinuities. The edge effect caused an increase in voltage amplitude and a decrease in frequency, but these changes did not affect crack detection. The smallest detected crack had a maximum width of about 20 μm and was invisible by the unaided eye. The obtained surface charts clearly illustrate the course and localization of individual discontinuities.

2

Impact of single-piece flow thermo-chemical treatment process conditions on hole quenching deformation

Stachurski Wojciech, Sawicki J., Zgórniak P., Wołowiec-Korecka E.

Archives of Materials Science and Engineering

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2023

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Vol. 121, nr 1

18--24

EN

Purpose: Pulsed low-pressure carburizing (LPC) and omnidirectional high-pressure gas quenching (HPGQ) are innovative methods for quenching the surface layer. The thermo-chemical treatment carried out by this method reduces quenching geometric deformations, with detailed numerical values not available in the literature due to the short existence of this method. Design/methodology/approach: Sixteen toothed elements of EN 20MnCr5 steel were subjected to pulsed low-pressure carburising with omnidirectional jet quenching in 4 groups, varying the process temperature (920°C, 960°C) and in two groups performing a tempering treatment. The elements were tested before machining by measuring their internal hole diameters, radial runout, roundness and cylindricity. These values were tested again after treatment. The direction of change and the statistical significance of the effect of treatment and its parameters, temperature and tempering were analysed. Findings: Thermo-chemical treatment significantly affects geometric changes in diameters, roundness, cylindricity and radial runout compared to elements without heat treatment due to physical transformations occurring during this treatment (p<0.05). Changing the process temperature in the value range of 920°C-960°C affects the hole diameter (makes it smaller) (p<0.05), but does not affect radial runout, cylindricity and roundness. The observed dimensional changes in diameters have numerically small values (<0.005 mm). The tempering treatment can affect the values of average diameters. Its effect on roundness, cylindricity and radial runout was not observed. Research limitations/implications: In the temperature range studied, the method of pulsed low-pressure carburising + omnidirectional high-pressure gas quenching makes it possible to raise the temperature of the process and shorten its duration without significant geometric changes in the treated elements. Practical implications: The method of pulsed low-pressure carburising and omnidirectional high-pressure gas quenching (HPGQ) ensures the maintenance of reproducible quenching deformations at a level significantly lower than conventional processing methods. Originality/value: The method of pulsed low-pressure carburising together with omnidirectional high-pressure gas quenching (HPGQ) is a method that has been used briefly in the industry, and there are few reports on it to date.

3

Case hardening development review (2001-2020)

Wołowiec-Korecka E.

Archives of Materials Science and Engineering

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2023

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Vol. 120, nr 2

70--85

EN

Purpose: The purpose of the work is a complex review of methods applied industrially as case hardening. The paper contains an overview of scientific and development works on surface case hardening methods, especially carburising and quenching, described in the literature from 2001-2020. Design/methodology/approach: State-of-the-art was reviewed by a critical review of the world literature published in 2001-2022, including theoretical work, scientific research, and industry reports. An additional examination of the state of the art was conducted in terms of patent works. Findings: The period of 2001-2020 was a time of intensive work on the modernisation of case hardening techniques to improve the repeatability and uniformity of the produced layers and minimise deformations after hardening. Developing computing technologies have played a large part in this progress. New technologies have also been developed. Research limitations/implications: The review of papers and patent databases was limited to databases providing English-language content options. Practical implications: Case hardening is a crucial stage of steel heat treatment in almost every industrial branch: mechanical, tool, automotive, railway, and aviation. Originality/value: A synthetic review of case hardening methods was presented, particularly carburizing and quenching methods; it also analysed the possibilities and directions of their development.

4

Dynamic Processes of Substructural Rearrangement under Friction of Carbon Steel

Shevelya Valeriy, Pashechko Mykhaylo, Kalda Galyna, Sokolan Yulia

Advances in Science and Technology. Research Journal

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2023

|

Vol. 17, no 3

236--248

EN

The effect of heat treatment (tempering temperature after quenching) of medium carbon steels (steel 45 and steel 50) on tribological indicators at sliding friction without lubrication in connection with the change in strength and rheological elastic properties of steel, controlling the dissipative properties of the frictional contact has been studied. Tribotechnical tests were conducted according to two schemes. A high-temperature tribometer was used for “soft” friction according to the “ball-plane” scheme, which allowed varying the temperature of the friction contact. Influence of load-rate modes was studied in more “hard” conditions on the friction machine under the “finger-disk” scheme. Substructural transformations of steel caused by heat treatment were evaluated by changes in amplitude-dependent internal friction on a torsion pendulum-type machine, which also allowed measuring frictional damping (contact internal friction) in the preliminary displacement mode. The interrelation between hardness, elastic modulus and internal friction of steel and wear resistance, wear capacity, friction coefficient and the level of frictional damping has been established. It is shown that the growth of elastic modulus and increase of steel relaxation resistance after the appropriate heat treatment are conjugated with the development of adhesion and setting, which, as topochemical reactions in the solid phase, are the leading forms of contact stress relaxation under the above conditions. Correlation of tribological indicators of external friction with amplitude-dependent and relaxation (temperature-dependent) internal friction taking into account structural state of steel and friction temperature regime is established. Substructural preconditions, dynamic relaxation mechanisms of hardening and load-temperature friction conditions under which martensitic structures exhibit abnormally high wear resistance and significant growth of frictional damping level are considered. The tribological analogue of the Porteuen - Le Chatelier effect, manifesting in the form of frictional self-oscillations in the range of temperatures of dynamic deformation aging is established. A treatment of the nature of the Kael-Ziebel effect, the temperature-rate and load localization of which in friction is associated with the temperature range of dynamic strain aging with Snook-Kester relaxation superimposed, is proposed.

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Studies on the Mechanical Properties of C45 Steel with Martensitic Structure after a High Tempering Process

Woźniak Waldemar, Sąsiadek Michał, Jachowicz Tomasz, Edl Milan, Zając Paweł

Advances in Science and Technology. Research Journal

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2022

|

Vol. 16, no 3

306--315

EN

This article describes the studies of the mechanical properties of the martensitic structure of C45 steel, obtained as a result of heat treatment. This steel was subjected to high tempering, within the temperature range of 500 ÷ 700°C (every 50°C) and for various exposure times, from 15 minutes to 23 hours. Moreover, martensitic steel was subjected to tests by quenching at a temperature of 850°C for 20 minutes and then tempering it for 1 hour, within the temperature range of 50 ÷ 800°C (every 50°C). The resulting steel samples were subjected to strength tests, that is, to tensile and hardness tests and also to tests on the micro-structure. The results of these studies are presented and discussed, in detail, in terms of their practical application.

6

The effect of heat treatment on mechanical properties of 42CrMo4 steel

Çalık A., Dokuzlar O., Uçar N.

Journal of Achievements in Materials and Manufacturing Engineering

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2020

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Vol. 98, nr 1

5--10

EN

Purpose: In this study, the effect of heat treatment on the microstructure and mechanical properties of 42CrMo4 steel were investigated. Design/methodology/approach: The samples were annealed at 860°C for 120 min. followed by oil quenching and then tempered at temperatures between 480 and 570°C for 120 min. The microstructure of untreated 42CrMo4 steel mainly consists of pearlite and ferrite whereas the microstructure was found to be as a martensitic structure with a quenching process. Findings: The results showed that there is an increase in yield stress, ultimate tensile stress, hardness and impact energy, while elongation decreases at the end of the quenching process. Conversely, yield stress, ultimate tensile stress and hardness decrease slightly with the increasing of tempering temperature, while elongation and impact energy increase. Research limitations/implications: Other types of steels can be heat treated in a wider temperature range and the results can be compared. Practical implications: It is a highly effective method for improving the mechanical properties of heat treatment materials. Originality/value: A relationship between the mechanical properties and the microstructure of materials can be developed. The heat treatment is an effective method for this process.

7

The influence of coolant velocity on the local heat transfer coefficient during steel quenching

Szajding Artur, Gołdasz Andrzej, Telejko Tadeusz

Computer Methods in Materials Science

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2020

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Vol. 20, No. 4

157--164

EN

The results of the calculations of the local heat transfer coefficient HTC and a heat flux HF on the face of a cylindrical sample made of 1.0503 steel are presented. The sample was cooled from a temperature of approx. 930°C in a mineral oil having a temperature equal to 50°C. The experiments were performed for three speeds of the oil stream (0.2, 0.4 and 0.6 m/s). The oil stream was directed perpendicularly to the cooled surface. The temperature of each sample was measured with 4 thermocouples and recorded with a frequency of 10 Hz. The maximum values of HTC always occurred in the axis of the sample and were in the range of 8000 to 10,000 W/(m2 K). The results are presented in the form of useful graphs showing the dependence of HTC and HF on the surface temperature for various velocities of cooling oil. The calculations were made with self-developed software using the inverse solution of the boundary heat conduction problem.

8

The influence of quenching temperature on distortions during the individual quenching method

Wołowiec-Korecka E., Stachurski W., Zgórniak P., Korecki M., Brewka A., Byczkowska P.

Archives of Materials Science and Engineering

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2020

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Vol. 105, nr 2

80--85

EN

Purpose: In this paper, the impact of hardening temperature on the quenching distortions which occur during low-pressure carburizing with gas quenching - using the individual quenching method - was analysed. Design/methodology/approach: The reference elements were subjected to carburizing at 980°C, followed by gas quenching at temperatures of 860°C, 920°C and 980°C. The geometrical measurements of the elements were made before and after the chemical treatment and the size of the quenching distortions of their geometrical parameters was determined. Findings: It was demonstrated that a high temperature of quenching has an unfavourable effect on changes in cylindricity and roundness parameters but, at the same time, reduces the size of distortion of outer parameters. Low temperature quenching reduces quenching distortions of cylindricity and roundness parameters while increasing the distortion of outer dimensions. Research limitations/implications: Based on the research and analysis carried out in this work, it was found that the use of lower quenching temperature is justified in economic and quality terms. Practical implications: In the case of the aviation or automotive industry, very high quality of manufactured elements along with a simultaneous reduction of their production costs is extremely important. Maintaining the dimensions of the elements during heat treatment is extremely difficult. The tests allowed to determine the optimal hardening temperature, which brings with it acceptable deformations. Since it is easier to “repair” the outer geometrical dimensions (diameter, thickness), it seems that quenching from lower temperatures is a more favourable process. Originality/value: The conducted tests allowed to determine the most favourable conditions for hardening elements from the automotive industry, taking into account the occurring deformations and their subsequent processing

9

Devices for modern vacuum heat treatment

Korecki M., Brewka A., Wołowiec-Korecka E.

Archives of Materials Science and Engineering

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2019

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Vol. 95, nr 2

77--85

EN

Purpose: A review regarding the devices for vacuum heat treatment is presented. Design/methodology/approach: Devices for modern heat treatment has been reviewed. The devices has been classified regarding the heat treatment (quenching, carburizing, nitriding, tempering and annealing). The possible application, materials and parts for heat treatment as well as parameters of the devices has been analysed. Findings: There is a wide range of modern vacuum heat treatment devices. All currently used heat and thermo-chemical treatments may be proceed in vacuum equipment. It is also in many cases preferable to use vacuum- because of economic reasons, better metallurgical results or environmental friendliness. Also software simulators which facilitates the planning of heat treatment are available with the equipment. Practical implications: Because of the industry expectations regarding efficiency, quality, economy and safety, vacuum equipment becoming the subject of wider and wider attention. In particular, aerospace and automotive industries pay a lot of attention to these aspects. The basic task of vacuum devices is fast, effective, environmentally friendly production of high quality machine parts. Originality/value: The synthetic presentation of modern devices for vacuum heat treatment was presented, in particular furnaces for quenching, carburizing, nitriding, tempering and annealing. The products characteristic and applications has been presented. Also equipment for some advanced vacuum applications has been presented. Modern software which complements the devices in terms of designing heat treatment processes has been described.

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Wpływ obróbki cieplnej na właściwości stali typu maraging

Michta G., Kruk A.

Zeszyty Naukowe Politechniki Rzeszowskiej. Mechanika

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2018

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z. 90 [298], nr 3

357--366

PL

Celem przeprowadzonych badań było określenie wpływu obróbki cieplnej na właściwości stali maraging o oznaczeniu N18K9M5TPr. Porównano wyniki badań właściwości mechanicznych, fraktograficznych, twardości oraz mikrostruktury materiału w stanie dostawy, po przesycaniu oraz przesycaniu i starzeniu. Wykazano, że obróbką cieplną można sterować parametrami wytrzymałościowymi oraz plastycznymi przez dobór temperatury i czasu poszczególnych etapów przesycania i starzenia.

EN

As expected, samples of maraging steel subjected to quenching and aging showed the highest increase in strength properties in comparison to the material supplied after hardening. Heat treatment significantly influences hardness of the maraging steel. The highest hardness was demonstrated in sample 3, subjected to quenching and aging, which confirmed the assumptions related to the heat treatment of this alloy, i.e. the creation of a large number of very fine precipitates of intermetallic phases reinforcing the tested steel. The N18K9M5TPr steel, in a quenched and aged condition, despite very high hardness (56 HRC), is characterized by quite high toughness (deformation about 5.2%). Observation of the fractures of samples after a tensile test allows to observe that for materials with different variants of heat treatment, characteristic dimples are observed in the fractures which indicates plasticity of the fracture.

11

Obróbka cieplna prętów zbrojeniowych z samoodpuszczaniem martenzytu

Grajcar A., Morawiec M., Kozłowska A.

Stal, Metale & Nowe Technologie

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2018

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nr 7-8

22--25

PL

Rozwój przemysłu, w tym przemysłu budowlanego, bazującego na produkcji wyrobów wykonanych ze stali konstrukcyjnych, związany jest z coraz większymi oczekiwaniami dotyczącymi własności mechanicznych, jak i ceny tych wyrobów. Procesy produkcyjne ukierunkowywane są na uzyskiwanie materiałów o wysokich własnościach mechanicznych przy zmniejszeniu zapotrzebowania na energię potrzebną do ich wytworzenia, a co za tym idzie – zmniejszeniu kosztów produkcyjnych. Jedną z takich technologii jest technologia tempcore, która pozwala na uzyskanie wyrobów o wysokiej wytrzymałości w postaci prętów o zmiennej strukturze pomiędzy powierzchnią a rdzeniem wyrobu, bez potrzeby stosowania drogich pierwiastków stopowych. Jednocześnie w technologii tej wykorzystywane jest zjawisko samoodpuszczania martenzytu, co przekłada się na oszczędność energii w procesie produkcyjnym.

EN

The development of industry (including the construction industry) based on the manufacturing of structural steel products is related to higher and higher requirements regarding the mechanical properties and the price of these products. Manufacturing processes are focused on obtaining materials characterized by high mechanical properties and decreased energy demand at the same time, which means lower production costs. One of such technologies is the tempcore process, which allows to obtain high-strength products such as rode bars with the structure varying through the cross section of the product without the need to use expensive alloying elements. Moreover, this technology uses the martensite self-tempering phenomenon, which accounts for energy savings in the manufacturing processes.

12

Dilatometric Study of High Strength Steels Hardenability

Di Schino A.

Archives of Metallurgy and Materials

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2018

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Vol. 63, iss. 1

457--460

EN

The effect of low-alloy additions on low-C steels hardenability is reported. Various as-quenched materials with microstructures consisting of low-C (granular) bainitic (B), mixed bainitic (B)/martensitic (M) and fully martensitic microstructures were produced. Results show that for a given cooling rate, an increase of austenite grain size (AGS) and of Mo and Cr contents decreases the transformation temperatures and promotes martensite formation.

13

The influence of chemical composition on the dimensions change of hardened steels in nanofluids

Łyduch K., Gęstwa W.

Archives of Mechanical Technology and Materials

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2018

|

Vol. 38

29--34

EN

The paper presents the influences of nanofluids, which are used in hardening process, to dimension changes, hardness and microstructure of hardened construction of steel samples. An analysis was also carried out with the use of English methods of cooling abilities of nanofluids environments based on water, solid nanoparticles of Al2O3 and ammoniac water. The results of this experiment show, that only one of specific dimensions of cooled samples, in the distilled water, changed for about 9%, but when using nanofluids this change was smaller. The hardness of alloy materials got a few percent more when nanofluids were used in comparasion to using the distilled water. The gained results allow to conclude the positive influence of nanofluids on parameters of the hardened materials.

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Wpływ wymuszonego ruchu na zdolność chłodzącą wybranych olejów hartowniczych

Adrian H., Osika M.

Stal, Metale & Nowe Technologie

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2017

|

nr 7-8

60--64

PL

W artykule przedstawiono wyniki badań wpływu wymuszonej cyrkulacji na zdolność chłodzącą trzech olejów hartowniczych: Hartex 70S, Hartex 70 i OH 70. Na podstawie pomiarów szybkości chłodzenia sondy pomiarowej obliczono zależności współczynnika przejmowania ciepła (α) od temperatury powierzchni (T) chłodzonego przedmiotu dla dwóch przypadków: oleju nieruchomego i wymuszonej cyrkulacji oleju z szybkością 0,23 m/s. Stwierdzono znaczny wpływ wymuszonej cyrkulacji na zdolność chłodzącą badanych olejów w dwóch fazach chłodzenia: fazie powłoki gazowej i fazie konwekcyjnej.

EN

The paper presents the effect of forced circulation on the cooling ability of three quenching oils: Hartex 70S, Hartex 70 and OH 70. Based on the measurements of the cooling rate of the test probe, the relationships between the heat transfer coefficient, α, and the surface temperature, T, of an object being cooled was calculated for two cases: stationary oil and forced circulation of oil at the rate of 0.23 m/s. A significant impact of forced circulation on the cooling ability of the tested oils in two cooling stages: vapour blanked stage and convective cooling stage was observed.

15

Wpływ czasu eksploatacji na zdolność chłodzącą wybranych olejów hartowniczych

Adrian H., Osika M.

Stal, Metale & Nowe Technologie

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2017

|

nr 3-4

98--104

PL

W pracy przedstawiono wyniki badań wpływu czasu eksploatacji na zdolność chłodzącą trzech olejów hartowniczych: Hartex 70S, Hartex 70 i OH 70. Pomiary zdolności chłodzącej olejów stosowanych w liniach technologicznych do hartowania drobnowymiarowych elementów stalowych prowadzono w stałych odstępach czasu od 12 do 24 miesięcy za pomocą urządzenia ivf SmartQuench zgodnie z normą ISO 9950. Stwierdzono, że parametry zdolności chłodzącej olejów (maksymalna szybkość chłodzenia, vmax, szybkości chłodzenia przy temperaturach 550 i 300°C, v550, v300) były stabilne i nie ulegały znacznym zmianom z upływem czasu eksploatacji.

EN

The paper presents the results of the investigation of the effect of exploitation time on the quenching ability of three quenching oils: Hartex 70S, Hartex 70 and OH 70. The measurements of the quenching ability of the oils used in production lines for the quenching of low-size steel elements were carried out at regular intervals for a period of 12 to 24 months using the Ivf SmartQuench device according to the ISO 9950 norm. It was found that the parameters of the quenching ability of the oils (maximum cooling rate, vmax, cooling rate at the temperatures of 550°C and 300°C, v550, v300) were stable and did not undergo significant changes with exploitation time.

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Obróbka cieplna wysokowytrzymałych stali wielofazowych

Grajcar A.

Stal, Metale & Nowe Technologie

|

2017

|

nr 11-12

15--19

PL

Nowoczesne materiały konstrukcyjne muszą łączyć wysoką wytrzymałość i odporność na pękanie, a także wykazywać dużą podatność na odkształcenia technologiczne. Podczas gdy pierwsze dwa parametry można z powodzeniem polepszyć przez rozdrobnienie ziarna, to zapewnienie dużej odkształcalności blach, prętów i kształtowników stalowych wymaga innego podejścia materiałowego. Coraz częściej połączenie wymienionych parametrów mechanicznych wymaga zastosowania stali o mikrostrukturze wielofazowej, kształtowanej podczas kilkuetapowej obróbki cieplnej. Koegzystencja kilku składników strukturalnych o odmiennych własnościach mechanicznych czyni współczesne stale wielofazowe podobnymi do materiałów kompozytowych, łączących efektywnie odmienne własności.

EN

Modern structural materials have to combine high strength, toughness and technological formability. The former two parameters are usually improved through grain refinement, whereas the desired deformability of steel sheets, rods, and sections requires other material approach. The mentioned mechanical parameters can be more often obtained when using multiphase microstructure steels, which are formed during a multi-step heat treatment. The coexistence of several structural constituents of different mechanical properties makes current multiphase steels similar to composite materials, which combine effectively different properties.

17

Model numeryczny zjawisk hartowania stali narzędziowej do pracy na gorąco

Kulawik A., Wróbel J., Bokota A.

Modelowanie Inżynierskie

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2017

|

T. 33, nr 64

38--46

PL

W pracy przedstawiono kompleksowy model hartowania stali narzędziowej do pracy na gorąco. Pola temperatury otrzymuje się z rozwiązania metodą elementów skończonych zagadnienia przewodzenia ciepła. Model szacowania udziałów faz oparto na wykresach ciągłego nagrzewania i ciągłego chłodzenia (CTPa i CTPc). Udział fazy powstałej podczas ciągłego nagrzewania lub chłodzenia (austenit, perlit lub bainit) wyznacza się równaniem Johnsona-Mehla i Avramiego (JMA). Obliczanie udziału tworzącego się martenzytu realizowane jest zmodyfikowanym równaniem Koistinena i Marburgera (KM). W modelu zjawisk mechanicznych uwzględniono odkształcenia cieplne, strukturalne, plastyczne oraz odkształcenia indukowane przemianami fazowymi. Wielkości termofizyczne występujące w zagadnieniu termosprężysto-plastyczności uzależniono od temperatury i składu fazowego. Założono, że materiał charakteryzuje się wzmocnieniem izotropowym.

EN

In the paper the complex quenching model of the hot-work tool steel is presented. The temperature fields are determined based on the solving of the heat transfer equation using the finite element method. Model of estimation of phase fractions is based on the continuous heating diagram (CHT) and continuous cooling diagram (CCT). Phase fractions which occur during the continuous heating and cooling (austenite, pearlite or bainite) are described by Johnson-Mehl-Avrami (JMA) formula. To determine of the formed martensite the modified Koistinen-Marburger (KM) equation is used. In the model of mechanical phenomena the thermal, structural, plastic strains transformation induced plasticity are taken into account. Thermophysical properties occurring in the thermo-elastic-plasticity model depended on the temperature and phase composition of the material. It was assumed that the material is characterized by isotropic hardening.

18

Comparison of impact of immersed and micro-jet cooling during quenching on microstructure and mechanical properties of hypoeutectic silumin AlSi7Mg0.3

Czekaj E., Kwak Z., Garbacz-Klempka A.

Metallurgy and Foundry Engineering

|

2017

|

Vol. 43, no. 3

153--168

EN

This article presents research the results of the mechanical properties at the ambient temperature of hypoeutectic cast silumin EN AC-AlSi7Mg0.3 (according to EN 1706:2011; analogic to alloy A356 according to AA – the Aluminum Association). As related to the commonly known and used process of immersion during quenching, the research also used a micro-jet system of cooling. After quenching, the experimental samples were also submitted to artificial aging in three different variations. The achieved results were compared with the mechanical properties of the alloy in the as-cast state. Samples from the experimental alloy were subjected to micro-jet cooling during quenching; in principle, they had a similar level of properties as related to the samples that were cooled by immersion; only in some cases did the micro-jet cooling give better results. Further works in the field should be aimed at constructing machines for micro-jet cooling with water pressure levels significantly higher than the typical pressure of community waterworks.

PL

W artykule zostały zaprezentowane wyniki badań podstawowych właściwości mechanicznych (UTS, YS, E, N, HB) w temperaturze pokojowej podeutektycznego siluminu odlewniczego EN AC-42100 (EN AC-AlSi7Mg0.3) (zgodnie z EN 1706:2011; analogia stopu A356 według Aluminium Association). W odniesieniu do powszechnie znanego i stosowanego zabiegu chłodzenia zanurzeniowego (I, ang. immersing) podczas przesycania, w badaniach wykorzystywano również mikrostrumieniowy (M, ang. micro-jet) system chłodzenia. Po przesycaniu – metodą chłodzenia zanurzeniowego lub mikrostrumieniowego – próbki doświadczalne poddawane były także sztucznemu starzeniu w trzech różnych wariantach: S1, S2 i S3. Uzyskiwane wyniki były porównywane z właściwościami mechanicznymi stopu w stanie po odlaniu (stan F, ang. fabrication). Próbki z doświadczalnego stopu poddane mikrostrumieniowemu chłodzeniu przy przesycaniu miały w zasadzie podobne właściwości mechaniczne w stosunku do właściwości próbek chłodzonych zanurzeniowo i tylko w niektórych przypadkach mikrostrumieniowe chłodzenie dawało lepsze wyniki. Dalsze prace w tym obszarze powinny dotyczyć konstruowania urządzeń do mikrostrumieniowego chłodzenia o ciśnieniach wody znacznie przewyższających ciśnienie sieci wodociągowej, tj. do poziomu nawet kilkuset barów.

19

Identification of material model for Finite Element Modelling of quenching process

Michalik K., Banaś K., Bzowski K., Rauch Ł., Cybułka P.

Hutnik, Wiadomości Hutnicze

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2017

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Vol. 84, nr 4

146--149

EN

The paper concerns modelling of quenching process using the finite element method. The special emphasis is put on finding the proper material characteristics, in particular for heat transfer coefficient on solid-fluid contact boundary and heat conduction for fluid, in case of highly complex flow close to the solid-fluid boundary. Only heat transfer and fluid flow are considered with solid phase mechanical behaviour neglected. The paper presents an approximate numerical model of the process and technical means by which its implementation is realised. The included numerical examples show how the obtained model allows for fast approximate simulations of quenching.

PL

W pracy analizowany jest przypadek modelowania - za pomocą metody elementów skończonych - hartowania z wykorzystaniem oleju jako czynnika chłodzącego, w którym dochodzi do kontaktu ciała stałego i płynu w temperaturach przekraczających temperatury wrzenia oleju. Praca przedstawia techniczne aspekty realizacji numerycznej w ramach własnego oprogramowania do symulacji MES [5], ze szczególnym uwzględnieniem empirycznego doboru własności materiałowych. Wyniki wskazują, że warunki brzegowe na granicy ciała stałego z płynem z eksperymentalnymi wartościami współczynnika przenikania ciepła pozwalają na bardziej dokładne modelowanie przepływu ciepła w procesie hartowania metalu w oleju.

20

Modelling the effect of phase transformations on cooling rate during quenching in nuclear forgings using effective heat capacity

Howson M. P., Wynne B. P., Davies P. S., Talamantes-Silva J.

Computer Methods in Materials Science

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2017

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Vol. 17, No. 3

137--144

EN

A modelling methodology based on experimental heat capacity measurements has been used to predict the effects of latent heat formation on cooling rates in a thick sectioned nuclear forging during quenching. Differential scanning calorimetry was used to measure specific heat capacity as a function of temperature (100 - 1000°C) and cooling rate (5 - 70°C/min) that also incorporates the heat energy release during transformations, which is termed the effective specific heat. A user defined routine then incorporated this data into a finite element model of a full scale heat treatment trial forging that had section thicknesses of 200 and 330mm approximately. Excellent agreement with thermocouple data, taken from key test locations, was obtained, particularly at 0.25 and 0.5 thickness. However, some deviations from thermocouple data were seen that has been attributed to the model assumptions, particularly the method used to represent boundary conditions.

PL

Metodologię modelowania z wykorzystaniem efektywnej pojemności cieplnej wykorzystano do przewidywania wpływu ciepli przemiany na prędkość chłodzenia w masywnych częściach hartowanej odkuwki dla przemysłu jądrowego. Różnicowa kalorymetria tria skaningowa została zastosowana do pomiaru ciepła właściwe go w funkcji temperatury (100 - 1000°C) i prędkości chłodzeni; (5 and 70°C/min) z uwzględnieniem ciepła uwalnianego w czasie przemiany. Wyznaczone w taki sposób ciepło właściwe nazywane jest efektywnym. Uzyskane dane zaimplementowano poprze procedurę użytkownika do programu metody elementów skończonych modelującego w pełnej skali obróbkę cieplną odkuwki posiadającej masywne części z przekrojem poprzecznym o grubości 200.5 i 331 mm. Uzyskano bardzo dobrą zgodność wyników z modelu i pomiaru za pomocą termopar umieszczonych w punktach testowych, w szczególności dla 0.25 i 0.5 grubości. Za przyczynę zaobserwowanych pewnych odchyłek wyników obliczeń od pomiarów uznano przyjęte założenia modelu, w szczególności metodę opisu warunków brzegowych.