GOST R ISO 9042-2011
GOST R ISO 9042−2011 Steel. Manual method of counting points for the statistical evaluation of the volume fraction of the structural component using spot metering grid
GOST R ISO 9042−2011
Group B09
NATIONAL STANDARD OF THE RUSSIAN FEDERATION
STEEL
Manual method of counting points for the statistical evaluation of the volume fraction of the structural component using spot metering grid
Steels. Manual point counting method for statistically estimating the volume fraction of a constituent with a point grid
OKS 77.080.20*
AXTU 0709
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* ICS 9−2012 GOST R ISO 9042−2011 is with ACS
— Note the manufacturer’s database.
Date of introduction 2013−01−01
Preface
The objectives and principles of standardization in the Russian Federation established by the Federal law of 27 December 2002 N 184-FZ «On technical regulation», and rules for the application of national standards of the Russian Federation — GOST R 1.0−2004"Standardization in the Russian Federation. The main provisions"
Data on standard
1 PREPARED AND SUBMITTED by the Technical Committee for standardization TC 145 «monitoring Methods of steel products» on the basis of authentic translation into the Russian language of the international standard referred to in paragraph 3
2 APPROVED AND put INTO EFFECT by the Federal Agency for technical regulation and Metrology dated 30 November 2011 N 655-St
3 this standard is identical with ISO 9042:1988* «Steel. Manual method of counting points for the statistical evaluation of the volume fraction of the structural component using a point measurement grid» (ISO 9042:1988 «Steels — Manual point counting method for statistically estimating the volume fraction of a constituent with a point grid»)
4 INTRODUCED FOR THE FIRST TIME
Information about the changes to this standard is published in the annually issued reference index «National standards», and the text changes and amendments — in monthly indexes published information «National standards». In case of revision (replacement) or cancellation of this standard a notification will be published in a monthly information index «National standards». Relevant information, notification and lyrics are also posted in the information system of General use — on the official website of the Federal Agency for technical regulation and Metrology on the Internet
1 Scope
This standard specifies a manual method of counting points for the statistical evaluation of the volume fraction of the structural component in the microstructure of steel using point measurement grid.
This method is used for structural components, which can be clearly identified.
Note — as Used in this standard, the term «structural component» may refer to one phase and microstructural component, consisting of two phases or more.
2 the essence of the method
2.1 Basic principle of the method is that the grid containing a number of regularly spaced points, with its systematic imposition on the image of the microstructure can provide, after a representative number of overlays for the various fields of view of unbiased estimates of the volume fraction of the structural component.
2.2 Method consists of overlaying the pixel grid on the number of fields examined surface, counting the number of grid points in the structural component, and the subsequent calculation of the volume fraction.
3 Symbols and definitions
This standard uses the following notation and definitions: — the number of investigated fields;
— total number of grid points;
— counting points on
-m field;
— the proportion of grid points located in the considered structural component in the
-m field, expressed as a percentage of the total number of points in the grid:
— arithmetic average of values
;
the estimate of the standard deviation (
)
95% confidence interval:
— the volume fraction of the structural component, %:
4 Equipment
4.1 Measuring grid
The measuring grid consists of a number of evenly spaced points formed by the intersections of very fine lines. Figure 1 shows as examples two types of grids (round and square) that can be used.
Figure 1 — Examples of grids that can be used
| Round mesh | Square grid |
Note 1 — In the case of round meshes, you can use all 25 of the outer points or the outer 16 points or 9 points.
Figure 1 — Examples of grids that can be used
The mesh can be placed in the ocular of the microscope insert or printed on the transparent plate, which is placed on the screen of the microscope, or micrograph*.
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* As the use of microphotography is more time-consuming and costly, and should be avoided whenever possible.
4.2 Methods of observation
For observation of the microstructure using a microscope or other suitable device with viewing screen or eyepiece insert, preferably is provided with a table moving in directions and
.
5 Selection and preparation of samples
5.1 the Sample must be representative of the microstructure, which is necessary to assess the structural component.
The place of sampling, orientation of the observed surface, for example longitudinal or transverse, the number of samples and the area of the surface needs to be specified in the product standard or agreement between the parties.
5.2 Sample is subjected to polishing in accordance with metallographic techniques. During polishing should observe the necessary precautions, which excludes any modification of the microstructure.
5.3 If necessary, the sample can be subjected to metallographic etching to reveal the structural component, which is to be measured.
It is recommended that the depth of etching was as low as possible. The staining reagents of the type generally preferable to reagents that cause a preferential etching of one or more structural components, since the reagents of the latter type can lead to errors.
It is important to monitor the effect of time etching on the results of the evaluation of the volume fraction.
6 Methodology
6.1 Selection of measuring grid
To select the measuring grid, for example, the full number of points required preliminary visual assessment of the volume fraction of the structural component.
Table 1 shows the recommended value the total number of points of the measuring grid, depending on the volume fraction of the measured structural element. These recommendations do not correspond to the theoretical limitations, however, empirical observations have shown that the use of these values allows to optimize the test duration needed to achieve the required accuracy.
Table 1 — Recommended values the total number of points of the measuring grid
| Visual assessment of the volume fraction | The total number of points of the measuring grid |
| From 2% to 5% incl. |
100 |
| «5%" 10% « |
49 |
| «10%" 20% « |
25 |
| >20% |
16 |
6.2 Selection increase
The selected measurement grid placed on the image structure. The increase should correspond to the maximum possible magnification at which the two neighboring points of the measurement grid does not fall on the same particle or the same concentration of particles measured structural component.
6.3 the Choice of the number of studied fields
The number of fields to be measured, depends on the required degree of accuracy. Table 2 shows the number of measured fields depending on the selected measurement error and the magnitude of the volume fraction. To obtain reasonable statistical accuracy it is recommended to examine at least 30 fields.
Table 2 — number of fields to be measured, depending on the desired relative accuracy and the estimated values of the volume fraction structural component
Volume fraction |
Error 33% | Error 20% | Accuracy 10% | |||||||||
The number of fields |
The number of fields |
The number of fields | ||||||||||
| 16 points |
25 points | 49 points | 100 points | 16 points | 25 points | 49 points | 100 points | 16 points | 25 points | 49 points | 100 points | |
| 2 |
110 | 75 | 35 | (20) | 310 | 200 | 105 | 50 | 1250 | 800 | 410 | 200 |
| 5 |
50 | 30 | (15) | (8) | 125 | 80 | 40 | (20) | 500 | 320 | 165 | 80 |
| 10 |
(25) | (15) | (10) | (4) | 65 | 40 | (20) | (10) | 250 | 160 | 85 | 40 |
| 20 |
(15) | (10) | (5) | (4) | 30 | (20) | (10) | (5) | 125 | 80 | 40 | (20) |
Note 1 — the Values given in table 2 are approximate values obtained from the expression
where 
— volume fraction, %.
Note 2 — the values shown in parentheses when calculating the confidence interval from the expression (5) should use appropriate multipliers are shown in table 3.
If you score less than 30 fields in the expression (5), use the appropriate multiplier shown in table 3.
Table 3 — multiplier Value in the expression to compute a 95% confidence interval
The number of the studied fields |
Multiplier |
| 5 |
2,57 |
| 7 |
2,36 |
| 9 |
2,26 |
| 11 |
2,20 |
| 13 |
Of 2.16 |
| 15 |
2,13 |
| 20 |
Of 2.09 |
| 25 |
Of 2.06 |
| 30 |
2,04 |
6.4 the layout of the fields
When the number of fields is determined, to determine the distance between the fields in order to obtain regular distribution of the fields on the surface of the sample, excluding the overlap of the evaluated fields. Move the microscope stage in the directions
and
based on the resulting distance between the fields.
Note — If the microstructure shows a certain frequency distribution of the measured structural element, it should be avoided coincidence of grid points and structure. This can be achieved by using a circular grid or a square grid placed at an angle to the direction of periodicity of the structure.
6.5 the Research and evaluation fields
Each field is observed together with the selected grid placed on the image of the microstructure. The transition from one field to the next is carried out only by moving the table without supervision of the picture. This is done in order to eliminate any possibility of operator error in the location of the field relative to the mesh.
For each observed field to register the number of points in the structural component . All points on the boundary of the structural component shall be counted as half point.
For each field from the expression (1) determine the percentage of points that fall in the structural component:
7 Calculation of the volume fraction
The arithmetic average of the values
determined from the expression
The calculated standard deviation value from the average value calculated by the formula
The volume fraction is determined from the expression
95% confidence interval is determined from the expression
Note — If you use a small number of fields (less than 30), the multiplier 2 in the expression (5) is replaced with the appropriate value selected in table 3.
The error of determination can be calculated from the expression
Note — If it is desirable to improve the obtained accuracy, it is possible to perform additional measurements, increasing the number of fields; to reduce the error rate by 50%, the total number of measured fields should be increased four times.
8 test report
The test report shall contain at least the following information:
a) the nature and description of the investigated samples;
b) the orientation of the observed surface in the case of an anisotropic material;
c) the type of measuring grid (location, total number of points);
d) the number of investigated fields in the samples and their location;
e) the selected magnification;
f) the value of the volume fraction and, if required, the values of the confidence interval and the calculated error.
The electronic text of the document
prepared by JSC «Code» and checked by:
the official publication of the
M.: STANDARTINFORM, 2012
