Wyniki wyszukiwania - Biblioteka Nauki

1

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

100%

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

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tom 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.

2

Study on homogeneity and repeatability of single-piece flow carburizing system

100%

Madej A. , Brewka A. , Wołowiec-Korecka E.

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tom Vol. 84, nr 2

68--75

EN

Purpose: The purpose of this paper was to determine the homogeneity and replicability of carburized layers obtained by a continuous single-piece flow method. Design/methodology/approach: A series of 100 gears was carburized under low pressure atmosphere using the single-piece flow method. The microstructures of the obtained carbon layers were investigated. Hardness penetration pattern and carbon concentration profiles were tested. Findings: The findings have shown the validity/correctness of the microstructures of the carburized layers obtained by the single-piece flow method. It has been proved that the carbon layer in every gear is uniform, what confirms that each element is affected by the same process conditions and the gears in the whole series can be precisely reproduced. Research limitations/implications: The short-pulse low-pressure carburizing technology needs further investigation to understand its all mechanisms fully. Practical implications: The single-piece flow method provides the uniform and reproducible carburized layers with the precision magnitude exceeding the abilities of currently used thermo-chemical furnaces. When applying the method it is possible to obtain a uniform carburized case in every single gear from the whole series of elements subjected to the process. Optimized configuration of process parameters and carbon-carrying mixture allows to meet the high expectations of a modern and future industry, what is most crucial in exploiting carburized steel gears. Originality/value: The applicability of the LPC single-piece flow method to a demanding mass production has been verified. The statistical validity of research results of the whole manufactured series of gears is being performed for the first time.

3

Electron beam surface hardening of steel C45

80%

Śliwiński P. , Kubik K. , Kopyściański M.

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2022

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tom Vol. 66, No. 6

27--35

EN

Surface hardening makes it possible to obtain high wear resistance of components exposed to friction without the need for hardening the entire element, thereby reducing stresses and deformations as well as process costs. The electron beam, due to its ease of dynamic deflection and focusing as well as very high heating rates, makes it possible to obtain surface layers of required properties. The article presents results of metallographic tests and Vickers hardness tests of electron beam hardened shafts made of steel grade C45. The hardening process resulted in the obtainment of layers having thickness not exceeding 400 μm and hardness not exceeding 900 HV0.1.

4

An analysing of heat treatment process planning

80%

Smoljan B.

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tom Vol. 20, nr 1-2

563-566

EN

Purpose: Process planning of heat treatment has been investigated. The established approach of heat treating process planning is suitable for effective integration of heat treatment in computer added manufacturing. Design/methodology/approach: Process plan of heat treating process has been established based on fundamental process planning principals. The heat treatment was treated in the same as other manufacture processes. Findings: The general approach for process planning of heat treatment processes has been established. Heat treatment processes have to be designed into operations and sub-operations with the same principles that are also valid for other manufacturing processes. Research limitations/implications: The further research should be focused on development of methods for the better application of achieved results. Practical implications: This way of heat treatment process planning is more appropriate for integral trends of manufacturing, i.e., with the trend of introducing the modern systems in all parts of industrial manufacturing. Originality/value: The global approach of process planning of heat treatment processes was established and better unification with other manufacturing processes was achieved.

5

Wysokotemperaturowe nawęglanie próżniowe w piecach jednokomorowych

80%

Heuer V. , Schmitt G. , Pustowka C.

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2009

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tom Nr 4

41-45

PL

Artykuł przedstawia zalety wysokotemperaturowego nawęglania próżniowego realizowanego w piecach jednokomorowych. Nawęglanie próżniowe jest procesem utwardzania dyfuzyjnego, które zapewnia wysokie przenoszenie węgla do części stalowych, w porównaniu z konwencjonalnym procesem nawęglania gazowego. Te zalety można zintensyfikować przez stosowanie wyższej temperatury procesu, ponad 1000 °C. Współczynnik dyfuzji węgla w stali gwałtownie rośnie wraz z temperaturą. Dodatkowo granica wydzielania węgla przesuwa się do wyższych wartości. Poprzez stosowanie wysokiej temperatury nawęglania całkowity czas obróbki wyraźnie skraca się, co prowadzi do znacznego zwiększenia produktywności. Jako przykład zastosowania wysokotemperaturowego nawęglania próżniowego zaprezentowano w pracy jednokomorowy piec - ALD-Mono Therm.

EN

The advantages of high temperature vacuum carburizing when applied in single chamber furnaces are shown in this paper. Vacuum carburizing is a case hardening process which offers a higher carbon mass-transfer into steel-parts compared to the conventional gas-carburizing process. This advantage can be further increased when applying higher carburizing temperatures above 1000 °C. The diffusion coefficient in steel in-creases strongly with temperature. Additionally the limit of carbide precipitation is shifted to higher values. By applying higher carburizing temperatures the total treatment time is shortened dramatically which leads to a significant increase in productivity. An example for the application of high temperature vacuum carburizing in a single chamber furnace (ALD-MonoTherm) is presented in the paper.

6

Modelling of carbon diffusion and ferritic phase transformations in an unalloyed hypoeutectoid steel

80%

Wolff M. , Acht C. , Bochm M. , Meier S.

Archives of Mechanics

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2007

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tom Vol. 59, nr 4-5

435-466

EN

During the important industrial process of case hardening, phase transformations in a steel workpiece are essentially influenced by the (non-homogeneous) carbon distribution (near the surface). Moreover, the temperature course is of great importance. We develop a mathematical model of case hardening which takes diffusion of carbon in austenite, heat conduction and possible phase transformations into account. In this work, mechanical behaviour (thermo-elasticity, classical plasticity and transformation-induced plasticity) is not included in the model. As a result we obtain an initial-boundary-value problem for a coupled system of two parabolic partial and several ordinary differential equations. Finally, we present some numerical simulations.

7

Surface integrity functional analysis in hard turning AISI 8620 case hardened steel through 3D topographical measurement

80%

Farias A. , Delijaicov S. , Batalha G.

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tom Vol. 46, nr 1

47-52

EN

Purpose: This work aims investigate the resulting machined surface condition from hard turning process of mechanical components manufactured from case hardened steel. Design/methodology/approach: The surface was examined by parameters obtained from the three-dimensional surface topography obtained with an interferometric laser instrument. Findings: The selected roughness parameters analysis intends to have a functional characterization such as bearing capacity, fluid and lubricants retention ability and contact wear resistance. Research limitations/implications: The obtained results were validated against similar ones, showing that the employed measuring techniques and analyses were correctly conducted. Practical implications: The functional bearing area curve analysis parameters indicates that the resulting surface has a good area contact, good bearing capacity and reasonable ability to fluid retention as the reduced valley depth parameter Svk not produced higher values for all conditions tested. Originality/value: The obtained results in the surface roughness measurement shows consistency with other authors results, and it shows that the technique of hardened material turning is capable of producing surfaces with functionality and quality.