Occasional grain

[lidbasky]

Hi,
What is the meaning of occasional grain ? How can I measure size of occasional grains and how shall I report it (max occasional grain)? Is there any standard for determining occasional grains in metals? I need to determine average grain size and max occasional grains in IN718 forging part according to the requirements of this part, could anyone help me?

 

[metengr]

I did some high level searching and found occasional, large grains in an otherwise uniform structure can be measured using ASTM E930 based on the reference below

http://www.metallography.com/grain.htm

http://www.astm.org/Standards/E930.htm

Seek and ye shall find.

 

[EdStainless]

I suggest that you write your own internal procedure for this. You won't find a standard that breaks it down.
In ours we outline how many fields and intercepts are required for accurate grain size.
We also then say that In each filed the operator in to measure the two grains that appear the largest.We only report the actual average grain size but we have the other data on file.


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Plymouth Tube

 

[TVP]

My first guess is that ASTM E930 is what you need. Keep in mind that this standard does not evaluate true duplex/bimodal structures (see ASTM E1181), necklace conditions near grain boundaries, or widely varying grain sizes.

 

[lidbasky]

Dear Ed
In the requirements of part was written that average grain size shall be max No. 8 and occasional grains shall be max No. 7 according to ASTM E112. Shall I report the biggest grain which I observed in 3 or 5 microstructure images?