Skip to main content

Grain Size Measurement Methods.


How to calculate ASTM grian size of microstructure which have a scale bar?





Grain size analysis is used as a quality control tool to ensure that alloys are manufactured to specification.  Some examples of this include verification of the heat treatment and condition of the alloy.  It can also be used to assist in understanding material failures.


I have to find ASTM grain size, I would like to know is it a correct way to find the exact magnification of microstructure using scale bar .

We have the microstructure test specimen of various metals at the lab. I used those microstructure test specimen to calculate the grain size using the

                          Formula N*=2exp(n-1) 

at magnification of 100 X measured in an area of 1 sq. inch. I want to know if it is the standard method for obtaining the average grain size. Can anyone attach the American Society for Testing and Materials document ASTM E112-12?

Calculation of ASTM Grain Size Number?


Example:-
Supposed we count 16 Grain per square inch in a photomicrographs Taken at magnafication ×250 what is the ASTM grain number.

If we count 16 grains per square inch at magnification x 250,
then at magnification x 100 we must have:

N=(250/100}²* (16) = 100 grains/in.²=2n − 1
Log 100 = (n ~ 1) log 2
2= (n 1)(0.301)
n=7.64


Chemical Etching Process? 


Take100 ml D.M.water and heat 70~80 °C  and added picric acid 5Gm and sodium dodecylbenzene sulfonate ( C18H29NaO3S ) and continue mixed by and Glass rod.
Then add High carbon steel as like En8D and other for some time ( 1 Minute) for mixed carbon alloyment.
Then added 3ml Hydrogen peroxide (H2O2)slowly slowly in chemical , bobble are showing on upper surface in chemical solution.

The chemical solution is ready for eatching of specimens.

Surfaces clean side of specimens drop in chemical solution for 1~3 minutes and after completing the process wash with clean water. 
Then check 100×



Thanks.



Comments

Popular posts from this blog

INCLUSION RATING TESTING

INCLUSION RATING TESTING:- Non-metallic inclusions process :- Non-metallic inclusions are chemical compounds and non metals that are present in steel and other alloys. They are the product of chemical reactions, physical effects, and contamination that occurs during the melting and pouring process. Sources of inclusions formation Non-metallic inclusions that arise because of different reaction during metal production are called natural or indigenous. They include oxide , sulfide , alumina silicate and Globular oxide .Singl Globular oxide Apart from natural inclusions there are also parts of Slag, refectories , material of a casting mould (the material the metal contacts during production) in the metal. Such non-metallic inclusions are called foreign, accidental or exogenous. Most inclusions in the reduction smelting of metal formed because of admixture dissolubility decreasing during cooling and consolidation. Non-metallic...

Step Down test

Step Down ( macro-streak-flaw ) test of steel bar. Scope:- This Standard specifies a step-down test method, blue fracture test method and magnetic particle inspection method to assess the non-metallic inclusions in rolled or forged steel with the naked eye or using a magnifying glass with a magnification of not more than 10x. Test piece:- The test piece shall be machined to the dimensions given below in figure table 1 The machined surface shall not be rough but shall be fairly smooth. Test Procedure Process :- Sample preparation are complete then ,sample Deep in hydro cloric acid (HCL) temperature 70~80 Degrees centigrade for 1 Hrs. After process are complete then clean with hot & cold water . Method of Examination:- The length and the number of flaws shall be determined under good illumination cither with an unaided eye or with low magnafication 15x Terminology:- A:- For the purpose of this standard the streak flaw shall mean defects arising from n...

Heat treatment process.

Heat Treatment Processes:- Heat treatment of  steels is the heating and cooling of metals to change their physical and mechanical properties, without letting it change its shape. improving formability, machining, etc. Heat Treatment Process Steps:- In simple terms, heat treatment is the process of heating the metal, holding it at that temperature, and then cooling it back. During the process, the metal part will undergo changes in its mechanical properties. This is because the high temperature alters the microstructure of the metal. And microstructure plays an important role in the mechanical properties of a material. Holding:- During the holding, or soaking stage, the metal is kept at the achieved temperature. The duration of that depends on the requirements. For example, case hardening only requires structural changes to the surface of the metal in order to increase surface hardness. At the same time, other methods need uniform properties. In this case, the holding period is long...