Analysis of size distributions of primary oxide inclusions in Fe-10 mass Pct Ni- M ( M =Si, Ti, Al, Zr, and Ce) alloy
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I.
INTRODUCTION
IN order to understand the phenomenon of inclusion removal such as coagulation by collision and flotation, the size distribution of inclusions, which ranks as the most important parameter, has to be known as a function of time. A considerable number of size distribution measurements in plant and laboratory scale experiments have been reported, but unfortunately the verification that these results represent the true size distribution for a given sample has not been guaranteed. The principal difficulty encountered in size distribution analysis is that there is no satisfactory standard regarding the representative observed area and magnification in microanalysis to avoid the effects of inhomogeneity in particle dispersion. It is considered to be a useful approach in the estimation of observed size distribution to compare volume fraction of particles calculated from size distribution and that from chemical analysis of oxygen or metal element as inclusion. We have studied the deoxidation of an Fe-10 mass pct Ni alloy with Si, Ti, Al, Zr, and Ce deoxidants at 1873 K. The number, size, and composition of the primary inclusions in a polished cross section and on the film filter after electrolytic extraction were measured as a function of holding time at 1873 K. The difference in the inclusion characteristics among different deoxidants has been discussed on the basis of their mean values in a previous article.[1] The present article deals with the planar and spatial size distributions obtained by a cross section and extraction methods, respectively, and particular emphasis was placed on the experimental parameters such as the observed area and magnification in the microanalysis in order to obtain the true size distribution. Furthermore, the comparison between the volume fraction of inclusions obtained by chemANDREY KARASEV, Graduate Student, Department of Metallurgy, and HIDEAKI SUITO, Professor, Institute for Advanced Materials Processing, are with Tohoku University, Sendai 980-8577, Japan. Manuscript submitted July 13, 1998.
METALLURGICAL AND MATERIALS TRANSACTIONS B
ical analysis and that from inclusion size and number were made to provide the judgment of the reliable data. II.
METHODS FOR ESTIMATION OF PARTICLE CHARACTERISTICS
A. Cross-Sectional Measurement The planar size distribution of particles in a polished cross section of each sample was observed at three zones (top, middle, and bottom) by using a scanning electron microscope (SEM) at a magnification of 1000 or 2000. The total observed area of each sample was 0.25 to 1.36 mm2 and the total number of observed particles was 130 to 320 for the specimens of Si, Ti, and Al deoxidation and 330 to 660 for the specimens of Zr and Ce deoxidation. More details on the cross-sectional measurement are given in the previously cited article.[1] The diameter of a particle section, dA, was estimated as the diameter of a circle with the same area of a sectioned inclusion whose shape is spherical, polyhedral, or irregular.[1] This value for dA and the number o
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