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Evaluation of spheroidal graphite cast iron

Evaluation of cast iron spheroidal graphite rate that complies with industrial standards using image analysis software

Heat treatment process
Heat treatment process


Having castability, cast iron is a material from which large-size or complicated products can be created easily, and is used with a wide range of products and in applications due to its cheaper price than steel and the ease of production. Since cast iron normally has linear graphite flakes and is brittle and less resistant to shock, ductile cast iron, to which heat treatment is applied to make the graphite spheroidal, is used for important mechanical parts such as crankshaft, rocker arm, and various gear wheels. The way of determining the spheroidal graphite rate (%) is regulated by industrial standards such as JIS, and magnified observation using a microscope is used in the determination, after cutting out a metallic piece, burying it in resin, and polishing the surface. In the past, using standard diagrams classified by shapes that were attached to a written industrial standard, every single graphite flake was visually determined as to which standard diagram resembles the graphite, and the spheroidal graphite rate was calculated for each sample. However, to reduce educational cost for regular inspectors and to eliminate variation among different inspectors, semi-automatic calculation using software becomes the mainstream these days. Because it is difficult to identify a small difference between the shape-specific standard diagrams, minor adjustment based on human determination is needed to improve the determination accuracy of the software.

The Olympus solution

Olympus' "Granularity Analysis" solution of OLYMPUS Stream Image Analysis Software allows inspectors even who use it for the first time to calculate the "spheroidal graphite rate" complying with an industrial standard for each sample and embed measured results as additional information into the image, only by selecting the industrial standard and following the software guidance to go through the steps. Using the OLYMPUS Stream, various graphite shapes can be classified, as if they were subject to human visual check, by means of its unique algorithm that involves multiple measurement parameters. This is another reason why this software is accepted by our customers. ISO945-2, JIS G5502, ASTM A247, ASTM E2567-11, EN ISO 945-1, NF A04-197, GB/T 9441, and KS D 4302 standards are supported, and ferrite/perlite rate measurement after etching your sample is also enabled.

Example of graphite flakes

Example of graphite flakes

Graphite of cast iron,classified by shapes
and determined as spheroidal

EGraphite of cast iron, classified by shapes  and determined as spheroidal

Olympus IMS
Products used for this application

The GX53 inverted microscope features exceptional image clarity and excellent resolution at high magnifications. With accessories including a coded revolving nosepiece and software, the microscope's modular design makes it easy to customize for your requirements.
OLYMPUS Stream image analysis software offers fast, efficient inspection workflows for all process steps for image acquisition, quantitative measurements and image analysis, reporting, and advanced materials science inspections tasks.
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