December 14, 2017
Sanyo Special Steel Co., Ltd.

Development of a steel identification system analyzing spark image
Sanyo Special Steel Co., Ltd. (President: Shinya Higuchi, Head Office: Himeji, Hyogo) developed a steel
identification system by spark tests to distinguish types of steel, in joint research with Tokyo Universityof Science (President: Akira Fujishima; Shinjuku, Tokyo).
A spark test is one of inspection processes to identify steel grades from the shape and color of sparks.
We aim to make spark testing more sophisticated by replacing a sensory test, where identification isbased on a worker’s visual observation of sparks, with a machine test, where identification is based ondata analysis using a computer in this development.
To achieve this, we used image analysis technology. We developed a system for identifying the carbon
content in steel by photographing sparks, which change according to the steel's composition, and thenanalyzing the images to comprehend the characteristics of the sparks. Replacing spark testing thatcurrently depends on the proficient skills of workers with testing using machines is expected to improve
test accuracy and stability.
We have installed the machine with the newly developed steel identification system atmanufacturing sites on a trial basis, and we plan to proceed with verification of the system for practicalapplication in the future.
◆Background of the development of the steel identification system and its characteristics
A "spark test" is a test for identifying theconstituents of steel material and their content
based on the characteristics of sparks (such as
shape and color) observed from scattering sparks
when the material is applied to a grinding wheel. A
spark test is used as one testing procedure for
ensuring that the steel type and control data areconsistent. When there is an increase in the carbon
content of steel, there is typically an increase in theamount of sparks and bursts generated (see Figure

Figure 1: Example of sparks and bursts

1). Therefore, these characteristics are identified by
the human eye.
Nevertheless, identifying such characteristics requires highly developed skills, and factors such asdifficulty in mastering the spark test in a short time and the need for further test stability necessitatedreplacement of the sensory test through automation.

1/2

In 2010, we commenced joint research withProfessor Hiroshi Kobayashi of the Department of
Mechanical Engineering, Tokyo University ofScience. We developed a system capable ofidentifying different types of steel byphotographing the sparks and determining theircharacteristics through image analysis. Recently
we introduced this system (see Figure 2) on a trial
basis for practical verification. We established theconditions for photographing sparks with aFigure 2: Schematic layout of the test machine

high-speed camera to ensure the machine would
perceive the characteristics of the sparks in thesame way as the human eye does.
A new image analysis program (Patent No. 5706233) installed in the image processing unit has
improved the accuracy and speed of image analysis, which had been an issue in existing programs. The
machine continues to accumulate data for practical application. By calculating the volume of sparks
and number of bursts through image analysis and assessing their ratios, the machine is capable ofidentifying the carbon content in steel to within ±0.05%.
As one of the principles of our 10th Medium-Term Business Plan, we are promoting “further pursuit oftechnological superiority through enhancement of R&D and quality competitiveness.” We will continue
to focus on improving product quality through development of technologies, including the developmentof the steel identification system analyzing spark image.

- END -2/2