Metallurgy and Foundry Engineering
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ISSN 1230-2325
e-ISSN: 2300-8377
Issue Date
2009
Volume
Vol. 35
Number
No. 2
Description
Journal Volume
Metallurgy and Foundry Engineering
Vol. 35 (2009)
Projects
Pages
Articles
Strain distribution in cogging process of ingots with internal discontinuities
(2009) Chyła, Paweł; Łukaszek-Sołek, Aneta; Sińczak, Jan
In this paper is presented analysis of cogging process of the 16 Mg ingot in the three-dimensional state of deformation, using commercial program QForm 3D to valuate effective strain distribution. Additionally voids closing were analysed, which were purposely inserted (various diameters and shapes) in selected areas. Numerical calculations were carried out for two following processes: upsetting of the reforged ingot and cogging process. Cogging operation of reforged material was simulated according to two schedules from the head and the bottom side of the ingot. As a criterion of valuation of the cogging process with flat dies were accepted maps of effective strain distribution.
Effect of the cooling rate on the mottled cast iron microstructure designed for the mill rolls
(2009) Krawczyk, Janusz Ryszard; Pacyna, Jerzy
The influence of the cooling rate changes on the mottled cast iron microstructure was described in the paper. The investigated material constituted mottled cast iron, spheroidal, chromium-nickel. This cast iron, according to currently binding standards was marked GJS-HV300(SiCrNi2-3). The microstructure was described both qualitatively and quantitatively. The discussion of the formation mechanisms and their influence on the morphology of structural components and phases was conducted. The heat treatment was performed in such a way as to obtain either a pearlitic or a bainitic matrix as well as a different morphology of lederburitic cementite and graphite precipitates for the same matrix.
Assessment of a long-term and short-term process capability in the approach of analysis of variance (ANOVA)
(2009) Czarski, Andrzej
One of the fundamental tasks of the Statistical Process Control (SPC) is the assessment of capability of a process relating to client's expectations. Relating to a client, all process capability indices are, first of all, information on technological potential of a process, so they can be a criterion respecting selection of a producer. Relating to a producer, the indices can be a proof for process improvement or an alarm signal regarding a process performance. In the industrial practice long-term and short-term capability indices are determined very often (marked adequately as Pp, Ppk and Cp, Cpk). This method enables a detailed analysis of the process performance relating to a variability. The point is, first of all, to identify a presence of a so-called variability dependent on time caused e.g. by changes in a lot of raw material, successive process settings, a service of different operators etc. In other words we are interested if a process position for the sake of an analyzed parameter undergoes statistically significant variations in time. The study is mainly of a methodological character. There is a deepened interpretation of indices of a long-term and short-term process capability based on a one-way analysis of variance (ANOVA) presented. The performed considerations are illustrated with a computational example based on data concerning heat treatment of drop forgings. The better, more complete understanding the method of the assessment of a long-term and short-term process capability should facilitate the Users a correct interpretation of results and enable to avoid mistakes connected with possible not meeting the method assumptions necessary for use.
Some factors influencing the determination of eutectoid transformation start and finish temperatures in hypoeutectoid steels
(2009) Pawłowski, Bogdan; Bała, Piotr; Krawczyk, Janusz Ryszard
This paper presents problems related to the proper determination of the eutectoid transformation start and finish temperatures in steels during heating. Information from references indicate an essential influence of interlamellar spacing in pearlite on the formation of the dilatation effect related to the eutectoid transformation finish, on dilatometric curves. It was revealed, in this paper, that the appearance of the dilatation effect related to the eutectoid transformation finish in hypoeutectoid steels or its lack in the heating dilatograms depends on the resolution ability of the applied dilatometer.
Simulation of dispersed microstructure
(2009) Czarski, Andrzej
Stereological description of dispersed microstructure is not an easy problem and is constantly a subject of research [1, 2]. From the practical point of view, the stereological description of this type of microstructures is essential in analyses of such processes as coarsening, spheroidization or in research of relationship between the microstructure and mechanical properties (e.g. bearing steel). The method of computer simulation is a very comfortable and effective way to test properties of stereological parameters of a microstructure. The computer model of a dispersed microstructure presented in the work is based on the following assumptions: (1) particles of dispersed phase are spheres randomly distributed in space, the input data are: number of spheres in unit volume Nv, volume fraction of spheres Vv and distribution of sphere diameters in space (through the probability density function f(D), (2) the system of spheres is being cut by the cutting planes. As a result of the simulation we obtain the distributions of flat sections' diameters. The correctness of the model performance has been verified considering two cases relating to which we know analytical relations between distribution of spheres in space and distributions of flat sections' diameters: (1) the simulated structure consists of spheres of equal size, (2) spheres are subject to the Rayleigh distribution.