ASTM E 112 (Grain Size Number)
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ASTM E 112 Grain Size Measurement Steps
Button Operator Activity Program Instructions
Push the RESET button to erase all program steps created by the previous user. 1) Grab
The Olympus microscope currently has the 50x lens in the viewing position.
  • Select the 50x lens in the System Configuration window.
  • If Digital is not active, select Digital with a mouse click on the STAGE PARAM. button followed with a mouse click on the word Manual this toggles the stage controller from Manual to Digital.
  • Make sure the Field and Standard buttons have a white border, if not, a mouse click on the button will turn the white border ON or OFF.
The sample shows good grain boundary definition and the phase boundaries are clearly defined. This is because of the contrast difference between phases. It was decided that the only Gray level adjustment needed was to light up (or better define) the grain and phase boundaries by using the Edge detect tool. Mouse click on the Edge detect button to set the program in the ANALYSIS INSTRUCTION area. 2) Edge detect
Because only one feature is of interest, the grain and phase boundaries, only the edges defined by Edge detect will be shaded.

Chord size was added to eliminate noise, and small features from the binary image.

Set the BINARY shading using the Manual shading feature.
  • If Manual is not active, mouse click on the Manual/Automatic button to toggle the button to the Manual setting.
  • Mouse click on the Initiate button.
  • Set a narrow gray level to shade only the edges by using the right and center mouse button.
  • Write the desired Threshold setting in the ANALYSIS INSTRUCTION box with a mouse click on the left mouse button.
The Thinning routine is run, which also loads the Filling routine. This process further cleans up the image and produces continuous grain boundary lines that are only one pixel wide.
3) Cord size : pl 1->1. 4x4
4) Threshold: pl 1. Phase #1 37-98
5) Filling : Plane 1
6) Thinning : plane 1
First Select FIELD measurement.
  • Mouse click on the BINARY shading color. In this example select RED, because plane 1 is being used in the Threshold routine.
  • Push the Initiate button.
7) Field meas. : Plane 1
One line of code is needed in the Report Instruction Page.
  • Select Tables
  • Select FIELD measurement.
  • Make sure a white border is surrounding the ASTM #112 and Grain size buttons. If not, mouse click on these two buttons to make it so.
  • Push the Initiate button.
1) Tables Field
  • Toggle the Report ON/OFF button to Report ON if you want a printed report.
  • Toggle the Store ON/OFF button to Store ON if you want the measurements stored on disk.
  • Push the Start button.
Wait -- 16 measurement will take for 10-15 minutes.
If you wish to save this program, Select the PRG button, name the program, then push Save. The file will be saved on the LECO Image Analyzer's hard drive.

If you wish to save your program on a diskette, type B:\myprogram , then push Save.

ASTM E 112 Grain Size Measurement Example
Program Steps

1) Grab
Program Steps

2) Edge detect
Program Steps

3) Threshold: pl 1. Phase #1 37-98
4) Chord size : pl 1->. 4x4
Grab Image. In this low-carbon steel, the Ferrite (alpha-iron) is the light phase and the Pearlite (mixture of Ferrite and iron-carbide) is the dark phase. The Edge detect program outlines the boundaries between grains and phases.
The Threshold is painted using Manual control in the shading routine. Because ASTM E 112 requires measuring and counting interfaces, only one analysis plane is needed.
Program Steps

5) Filling : Plane 1
6) Thinning : Plane 1
7) Field meas. : Plane 1

ASTM E112 Theory

The method of measuring grain size has evolved from a chart method developed in the 1930's to the modern automatic image analysis methods use today. The basic equation defining the ASTM E 112 grain size number is:

n is the number of grains per square inch at 100x.
G is the ASTM (Timken) grain size number. See the MET 231 laboratory handout or read the ASTM E112 standard for more information.

To review statistics used in these laboratory experiments review the MET 231 laboratory handout.
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One Cycle of ASTM E 112 Image Analysis Routine
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