Analysis of metallographic grain size

1. Crystalline Grain Size


There are various types of metals, and it is necessary to select appropriate metal materials based on their intended use and purpose. For instance, the metal materials used in automotive engine parts differ from those used in general metal parts. This is because different metals exhibit significantly varied mechanical properties (such as resistance to tensile, compressive, and shear forces).


To evaluate these mechanical properties of metal materials, it is essential to observe the crystalline structure of metals.

Metal structures consist of polycrystalline structures composed of crystalline grains. There are regions between these grains where the arrangement is disordered, and these boundaries are known as grain boundaries. The size of these crystalline grains (grain size) is a crucial factor that determines the mechanical properties of such metal materials.

Generally, crystalline grain size refers to the “size of the grains” in materials like metals.

Furthermore, metal structures change with heat treatment, not just based on the type of metal material like aluminum, iron, or alloys. Even within the same type of metal or alloy, heat treatment arranges the crystalline grains into specific patterns, forming grain boundaries different from those before heat treatment. Therefore, heat treatment alters the crystalline grain size, thereby changing the mechanical properties and characteristics of metals.


Consequently, the analysis of grain size is a critical inspection for ensuring the quality of metal products.


 ・Austenitic Crystal Grains


Face-Centered Cubic (FCC) crystal grains containing annealing twins


 ・Ferrite Crystal Grains


Body-Centered Cubic (BCC) crystal grains without annealing twins





2.Methods for analyzing crystal grain size


1. Visual Comparison between Standard Chart and Metallographic Microscope


The metal surface is prepared by polishing, followed by observation under a metallographic microscope. The grain size is estimated by visually comparing the enlarged metal structure observed through the microscope with the “Austenite Crystal Grain Size Standard Chart for Steel (×100) JIS G 0551.”






金属顕微鏡  金属顕微鏡の詳細はこちら


However, it is cumbersome as it requires temporarily looking away from the metallographic microscope.



②Integration of Eyepiece Micrometer into Metallographic Microscope for Simultaneous Observation and Comparison (Comparison Method) 

Insert an eyepiece micrometer (reticle) with grain size patterns printed on it into the eyepiece of the metallographic microscope. This allows for simultaneous visual comparison between the enlarged sample and the grain size standard pattern. By observing them concurrently without needing to look away from the metallographic microscope, the grain size can be estimated comfortably.



Shibuya Optical Co., Ltd.’s R1901 Particle Size Scale





3. Incorporating an eyepiece micrometer into a metal microscope for simultaneous observation and comparative measurement (counting / planimetric method, intercept method).


Insert the eyepiece micrometer (reticle) with the pattern printed as shown below into the eyepiece of the metal microscope. Determine the average line segment length per crystal grain crossing through enlarged samples and their patterns, calculating the grain size in accordance with JIS G0551/ASTM E112 standards.


Shibuya Optical Co., Ltd.’s R2010-24 Steel – Grain Size Testing Scale (Sectioning Method)





④ Using a camera to perform particle size measurement with software (comparative method, counting / planimetric method, intercept method)


Furthermore, attaching a microscope camera to the metal microscope and performing automatic measurements using the following measurement software.

This method enables automated measurements, significantly enhancing efficiency.


顕微鏡用USB3.0カメラ For details on the USB3.0 camera for microscopes (5MP), click here.


粒子解析ソフトウェア G-S Measure(日鉄テクノロジー株式会社製)

For details on the particle analysis software G-S Measure (manufactured by Nippon Steel Technology Co., Ltd.), click here.

◆ Particle Analysis Software G-S Measure for Grain Size Measurement

【Compliance with JIS and ASTM Standards!】


This tool evaluates grain size based on the following standards:
– JIS Standard (JIS G 0551:2005)
– ASTM Standards (ASTM E 112-96, ASTM E 1382-97)


【Up to 12 Different Grain Size Measurements Possible!】


– Evaluation methods allow simultaneous measurement of up to 12 patterns using combinations of cutting patterns, enabling calculation of grain size numbers.


【Choose from 5 Cutting Patterns!】

– In the sectioning method, you can select from 5 cutting patterns and adjust intervals and line lengths.

【Convenient for Report Generation! Excel Output】

– Measurement results for grain size can be exported to Excel (CSV format), facilitating report creation.



粒子解析ソフトウェア G-S Measure 結晶粒度測定


<Measurement Display Example> ASTM (Intersection Sectioning Method, Slice Length Comparison Method)

After measurement, the display highlights grain boundaries in blue where they intersect with the cutting pattern.
* The image example measures within a microscope magnification of 100x and a range of 1000×1000 dots.











Product Inquiry phone028-3911-2006


General Specification




Feature of the pre-installed software for Simplified Measurement


  • Observe live video
  • Simultaneous display of live image and save screen
  • Save the still image (JPEG, BMP)
  • Pause the observed image (Freeze Function)
  • Measure the distance between two points
  • Supported OS: WindowsXP, Vista, 7, 8 and 10 (Compatible with 32bit and 64bit)
  • * Saving and reading calibrated data while measure

Glass scale for the calibrations is option.

A powerful measuring software MeasurePRO


A measuring software developed by our company.
Able to display multiple crosslines, grids, saved thumbnails and comments. Can export the data to Excel.

  • Measuring types

    [Distance between 2 points]
    [3 Points Angle]
    [4 Points Angle]
    [Distance between 2 circles]
    [Perpendicular line]

  • Features

    ・Export to excel
    ・Show multiple crosslines
    ・X, Y axis scales
    ・Show grid lines
    ・Display both saved image and live image on separate screens
    ・Insert comments



Measuring software with focus stacking function

Standard accessories are two glass scales for calibration (GS - 0.2, GS - 0.5).

Measure easily on the screen.

  • Measuring types

    [Distance between 2 points]
    [3 Points Angle]
    [4 Points Angle]
    [Distance between 2 circles]
    [Perpendicular line]

  • Features

    ・Focus stacking function

The powerful MeasurePRO and the function-rich MeasurePRO-Ex measurement software comparison

 ・Please refer to the table below for the availability of the functions you need

  MeasurePRO-Ex MeasurePRO
Measure distance between 2 points
Focus stacking
Export to excel
Show thumbnails
Adjust screen magnification
Display crossline Multiple Multiple
Display grids
Display X, Y axis scales
Supports Windows XP、Vista、7、8 and 10 (32bit・64bit)

Inquire about this product


Business hour: 08:00 - 17:00
Closed on weekends & public holidays