The article presents the results of a sensitivity analysis of artificial neural networks developed for a system which predicts the durability of forging tools used in the selected hot die forging process. The developed system makes it possible to calculate the geometric loss of the examined tool for the given values of its operating parameters (number of forgings, tool temperature at selected points, type of the applied protective layer, pressure and path of friction) and estimates the intensity of the occurrence of typical mechanisms of tool destruction, i.e. thermo-mechanical fatigue, mechanical wear, abrasive wear and plastic deformation. Nine neural networks operate in the developed system. Five of them determine the geometric loss of the material used for tools operating with protective layers, including a nitrided layer, a pad welded layer and three hybrid layers, i.e. AlCrTiSiN, Cr/CrN and Cr/AlCrTiN. Four networks make calculations determining the intensity of the occurrence of typical destructive mechanisms. The developed sensitivity analysis allows for each neural network to show which input parameters are most important and have the greatest impact on the explained variables. This is determined based on the network error analysis in the case of elimination of individual variables from the input data. The greater the network error calculated after rejecting an input variable relative to the error obtained for the network with all the input variables, the more sensitive the network to the lack of this variable. The best compliance was obtained for the first developed set of networks regarding the geometric loss of material, while the lowest compliance was obtained for the second developed set of networks regarding the applied protective layers, and in particular for plastic deformation and mechanical fatigue, probably due to the smallest size of these sets in the knowledge base. The obtained results of this analysis are important for the system operation, i.e. supporting the technologist's decision in the selection of such process parameter values that will increase the die's lifetime.

EffEct of hEAt trEAtmEnt pArAmEtErs on thE formAtIon of ADI mIcrostructurE wIth ADDItIons of ni, cu, mo WpłyW parametróW obróbki cieplnej na kształtoWanie mikrostruktury żeliWa aDi z DoDatkami ni, cu, moMetallographic examinations and mechanical tests were carried out on the ductile iron with additions of Ni, Cu and Mo in as-cast state and after austempering. TTT and CCT diagrams were plotted. The heat treatment was performed in six different variants. Studies included qualitative assessment of the microstructure and testing of mechanical properties such as R0,2, Rm, A, Z, HRC, KC. An analysis of the obtained results was also presented.Keywords: ductile iron, heat treatment, the microstructure of ADI, ADI mechanical properties przeprowadzono badania metaloznawcze żeliwa sferoidalnego z dodatkami ni, cu i Mo w stanie lanym i po hartowaniu izotermicznym. opracowano wykresy cTpi i cTpc. obróbkę cieplną wykonano w sześciu różnych wariantach. Badania metaloznawcze obejmowały ocenę jakościową mikrostruktury i pomiary właściwości mechanicznych: r0,2, Rm, A, Z, HRC, Kc. dokonano analizy uzyskanych wyników

The results of examinations of microstructure and an analysis of its impact on selected mechanical properties of austempered ductile iron (ADI) were presented in the paper. The ADI was produced from the ductile iron containing 1.56% Ni only alloying addition. The effect of the austempering time and temperature on the microstructure and mechanical properties of the examined cast iron was considered. Constant conditions of austenitizing were assumed and six variants of the austempering treatment were adopted. The studyof mechanical properties included a static tensile test, Charpy impact strength test and Brinellhardness measurement.This work complements the knowledge about alloying additions effect on microstructure and mechanical properties of ADI and focuses on the impact of a single alloying element (Ni).

The paper presents a mathematical model of the pearlite -austenite transformation. The description of this process uses the diffusion mechanism which takes place between the plates of ferrite and cementite (pearlite) as well as austenite. The process of austenite growth was described by means of a system of differential equations solved with the use of the finite difference method. The developed model was implemented in the environment of Delphi 4. The proprietary program allows for the calculation of the rate and time of the transformation at an assumed temperature as well as to determine the TTT diagram for the assigned temperature range.Keywords: Modelling, phase transformations, TTT diagrams W pracy zaprezentowano matematyczny model przemiany perlit -austenit. Do opisu tego procesu wykorzystano dyfuzyjny mechanizm zachodzący pomiędzy płytkami ferrytu i cementytu (perlitu) oraz austenitu. Proces wzrostu austenitu opisany został układem równań różniczkowych rozwiązanych przy wykorzystaniu metody różnic skończonych. Opracowany model zaimplementowano w środowisku Delphi 4. Autorski program pozwala na obliczanie szybkości i czasu przemiany przy założonej temperaturze oraz na wyznaczanie wykresu CTP i dla zadanego zakresu temperatur.

The method of parametric representation of TTT diagrams on example of selected austempered ductile cast irons is presented. TTT diagrams were digitalised and n, k parameters of Johnson Mehl equation were calculated. The relationships between n, k parameters and transformation temperature were analysed for two ADI irons. Knowledge of these parameters enables to calculate the progress of austenite to bainite transformation.Keywords: TTT diagrams, austempered ductile iron, bainitie transformation W pracy zaprezentowano metodykę parametrycznej reprezentacji wykresów CTP i na przykładzie wybranych wykresów dla żeliw sferoidalnych. Wykresy CTP i digitalizowano, a następnie obliczano parametry n i k równania Johnsona-Mehla opisującego postęp przemiany przechłodzonego austenitu w bainit. Analizowano wpływ temperatury przemiany na wartość parametrów n, k. Znajomość tych parametrów pozwala obliczać postęp przemiany austenitu w bainit przy danej temperaturze.