Examination of Some Grain Size Measurement Problems

ABSTRACT:

The measurment of grain size is performed nearly always on a metallographically prepared cross section, suitably etched to reveal the grain structure, using methods that pertain only to the grain cross sections. These measurements are termed planar and some may be converted mathematically into spatial estimates of the size of the three-dimensional grains. However, the vast majority of such work is planar where no assumptions about grain shape are required and grain size is described in one- or two-dimensional terms (intercept length, diameter, or area) based on sections through the grains. The most frequently used measurement methods are described in this paper and compared using the same images. These methods are the Jeffries planimetric method, the triple-point count method, and the Hetn intercept method. These methods base grain size on two-dimensional, zero-dimensional, and one-dimensional features
of the microstructure, resnectively (that is areas, points and lines),

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Computer-Aided Microstructural Analysis of Specialty Steels

Computers are utilized in a variety of microstructural characterization functions - some are quite common, others are not. In this paper, three case studies of detailed specialty steel image analysis programs performed at Carpenter Technology Corporation will be reviewed. All involved computer-generated graphical analysis.

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Automating the JK Inclusion Analysis

A procedure has been developed that through the use of the Leitz Texture Analyzer System (TAS) makes it possible to automatically obtain JK-inclusion ratings consonant with those obtained manually by ASTM E45, Methods A and D, which provide qualitative and quantitative data, respectively. In the new procedure, sulfide inclusions are detected by gray-level differences because image analysis techniques cannot distinguish between type-A sulfides and type-C silicates on the basis of morphological differences alone. Next, the stringered and globular oxides are seperated. Type-B and Type-C stringered oxides are seperated on the basis of the length of the largest oxides in a stringer. After each inclusion type has been isolated, the required measurement is made and the severity is calculated. For each type, the inclusions are further seperated according to thickness. Reproducibility of ratings with the new procedure is quite good, and the results obtained are in good agreement with those done manually.

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resourcesThe articles and presentations that can be down-loaded from this web site are based upon work done by GFV while employed at Bethlehem Steel (1967-1983), Carpenter Technology (1983-1996), Buehler Ltd. (1996-2009) and Struers (2009-Present) and from the authors consulting work for companies such as, Latrobe Steel, Scot Forge, etc., and from his litigation work. GFV's bylined articles appearing in various issues of the ASM Handbook series have been listed here courtesy of ASM International, Materials Park, Ohio.

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