GOST R ISO 14250-2013
GOST R ISO 14250−2013 Steel. Metallographic evaluation of duplex grain size and distribution
GOST R ISO 14250−2013
NATIONAL STANDARD OF THE RUSSIAN FEDERATION
STEEL
Metallographic evaluation of duplex grain size and distribution
Steel. Metallographic characterization of duplex grain size and distribution
OKS 77.080
Date of introduction 2014−10−01
Preface
1 PREPARED AND SUBMITTED by the Technical Committee for standardization TC 145 «control Methods metalloproduktsiya"
2 APPROVED AND put INTO EFFECT by the Federal Agency for technical regulation and Metrology, dated 22 November 2013 No. 2055-art.
3 this standard is identical with ISO 14250:2000* «Steel. Metallographic measurement of duplex grain size and its distribution (ISO 14250:2000 «Steel — Metallographic characterization of duplex grain size and distribution»).
________________
* Access to international and foreign documents referred to here and hereinafter, can be obtained by clicking on the link to the site shop.cntd.ru. — Note the manufacturer’s database.
4 INTRODUCED FOR THE FIRST TIME
Application rules of this standard are established in GOST R 1.0−2012 (section 8). Information about the changes to this standard is published in the annual (as of January 1 of the current year) reference index «National standards» and the official text changes and amendments — in monthly information index «National standards». In case of revision (replacement) or cancellation of this standard a notification will be published in a future issue of 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 (gost.ru)
1 Scope
This standard specifies the metallographic method for the determination of duplex grain size in the rolled or forged parts of steel, using standard reference scales or the method of calculation of points.
2 Normative references
This standard uses the regulatory references to the following international standards*:
_______________
* The table of conformity of national standards international see the link. — Note the manufacturer’s database.
ISO 643:2000 Steel — Metallographic determination of the size of the ferritic or austenitic grain (ISO 643:2000, Aciers — 
ISO 9042:1988 Steels. The method of computing the points manually for the statistical evaluation of the volume content of the component of the grid reference points (ISO 9042:1988, Aciers — 
I’aide de points de grilles)
3 Terms, definitions and abbreviations
This standard applies the following term with the appropriate definition:
3.1 duplex grain size: Grain structure in which the distribution of lengths of intersections of the grains, their diameters or squares of the deviates from a simple lognormal distribution.
Note — Different types of duplex grain size is described in 7.1.
3.2 Reduction
ALA — separate large grains (As large as);
AGS — average grain size (Average grain size);
BD — banded structure (Banding);
BM bimodal structure (Bi Modal);
CS — the change of grain size in the cross section (Cross section);
Long. — longitudinal orientation of the sample (Longitudinal);
NL — aurelita structure (Necklace);
OSS — random (Occasional);
Trans. — transverse orientation of the sample (Transverse);
WR — wide range of grain sizes (Wide Range).
4 the essence of the method
4.1 Duplex grain size PODRAZDELENIE* two classes with the individual types belonging to these classes, and assessing a share of the area occupied by grains of different sizes.
________________
* The text of the document matches the original. — Note the manufacturer’s database.
4.2 the Present method can be used for samples or products containing two or more significantly different grain size, randomly located or topologically changing picture.
Since 4.3 this test method characterizes the deviation of the grain size from simple log-normal distribution and represents the change of the grain size, should evaluate the entire surface of the sample.
5 Instrument
5.1 General provisions
Equipment used depends on the test method, see 5.2−5.4.
5.2 comparison Methodology to estimate a share of the square
This technique requires the use of a reference scale with the aim of improving the accuracy of visual estimates of proportion of area occupied by grains of different sizes. The reference scale is given in Appendix A, shows a different percentage of light grains among dark grains.
5.3 Methodology the estimate in points for proportion estimates of the square
________________
* The text of the document matches the original. — Note the manufacturer’s database.
This technique requires the use of a measurement grid on a transparent overlay or in the ocular insert, in accordance with ISO 9042
5.4 Determination of grain size
Determination of grain size — ISO 643.
6 Selection and preparation of samples for testing
To characterize the distribution pattern of duplex grain size, you should use full cross section of the specimen, otbrannyh from the product.
The test surface should be oriented in the longitudinal direction in a plane parallel to the direction of maximum deformation of the product, with the exception of bars and pipes, for which the test surface should be perpendicular to the direction of maximum deformation.
The number of samples and their cutting should be specified in the normative documents for the products. If such instructions are absent, the matter is left to the discretion of the manufacturer.
A flat surface of a sample to be polished for metallographic examination and etched with the appropriate reagent during the necessary time. The etching should be performed so that all or almost all the grain boundaries visible.
7 test procedure
7.1 the Recognition and classification of duplex grain size
7.1.1 Chaotic duplex grain size
7.1.1.1 General characteristics
Indiscriminate duplex grain size is determined by the following criteria:
7.1.1.2 Randomly distributed large grains
This type is characterized by the presence of randomly distributed individual coarse grains, differing in size, or the number of grains of the average size of the remaining grains.
These individual coarse grains should occupy 5% or less of the area of the sample. If they occupy more than 5% of the area, the assessment should be carried out in accordance with
Example photomicrographs ALA grain size are shown in figure 1.
Figure 1 — ALA grain Size
Figure 1 — ALA grain Size
7.1.1.3 a Wide range of grain sizes
This type is characterized by presence of extremely wide range of randomly distributed grain size, when the largest size is different from the smallest size for five or more rooms grain.
Example photomicrographs of a wide range of grain sizes is shown in figure 2.
Figure 2 — WR grain size
Figure 2 — WR grain size
7.1.1.4 Bimodal grain size
This type is characterized by the presence of two clearly distinguishable randomly distributed grain size, which differ by more than four the number of grains and together occupy 75% or more of the total area of the sample.
An example micrograph of bimodal grain size shown in figure 3.
Figure 3 — VM grain size
Figure 3 — VM grain size
7.1.2 Topological duplex grain size
7.1.2.1 General characteristics
Topological duplex grain size is defined by the following features:
7.1.2.2 Change in grain size across the section
This type is characterized by a systematic change in grain size across the section of the product, in which the average grain size varies from one area to another on three or more the number of grains or the presence of different sizes of grains in specific areas of a cross section of products (e.g., coarse grains resulting from embryonic growth in the areas of critical deformation), the grain size in these specific areas is different from the grain size in the main part of the cross section for three or more numbers of grains.
Example photomicrographs of the change of the grain size on the cross section shown in figure 4.
Figure 4 — CS grain size
Figure 4 — CS grain size
7.1.2.3 Aurelita structure
This type is characterized by the presence of individual coarse grains, each surrounded by a ring of smaller grains; large and small grains differ in size, or the number of grains.
Example photomicrographs agerelated structure shown in figure 5.
Figure 5 — NL grain size
Figure 5 — NL grain size
7.1.2.4 Banded grain structure
This type is characterized by the presence of bands with different grain sizes, wherein three or more rooms grain.
Example photomicrographs of banded grain structures are shown in figure 6.
Figure 6 — BD grain size
Figure 6 — BD grain size
7.2 Estimation of a share of the square
7.2.1 Methodology comparison
This methodology is compared to the observed field of view with a reference scale. Used increase should provide a visual resolution of large — and fine-grained phases such as clearly marked zones.
For a class of chaotic duplex grain size comparison should be not less than five randomly selected fields of the sample.
For a class of topological duplex grain size comparison should be performed on the entire surface of the sample.
Calculate the average value obtained a share of area (percentage of the total specimen area) occupied by distinct grain size for the studied number of plots.
7.2.2 Method of calculation of points
This technique, according to ISO 9042, should be applied based on the rules given
7.2.3 Methodology of direct measurement
True specific procedure is used only for samples with topological duplex grain size containing surface layers with different from the base metal grain size. For such samples should be performed at least 10 measurements of the depth of the specified surface layer in different places. The estimated share of the area can be calculated based on the average values of the measurements and complete the investigated area.
7.3 Determination of grain size
The size of the individual coarse grains should be determined by the method ISO 643.
8 test report
The test report shall contain:
a) the brand of the investigated steel;
b) the orientation of the sample;
c) type of duplex grain size (with associated abbreviations);
d) method used;
e) the percentage of duplex grain size on the surface;
f) grain size;
g) the most suitable formats:
— L duplex, ALA, WR, AGS and N. N;
— L duplex, WR, WR, AGS and N. N;
— L duplex, BM, WR, AGS and N. N;
— L duplex, CS, WR, AGS centre N AGS of the surface N;
— T duplex, NL, WR, AGS, x % N, % N;.
— T duplex, BD, WR, AGS, x % N, % N.
Annex a (informative). Scale to assess a share of the square
Appendix A
(reference)
Figure A. 1 — Reference scale for estimating the proportion of the square (indicated by the percentage area of light grains among dark grains)
Figure A. 1 — Reference scale for estimating the proportion of the square (indicated by the percentage area of light grains among dark grains)
App YES (reference). Information about the compliance of the referenced international standards (and acting in this capacity interstate standards), national standards of the Russian Federation
App YES
(reference)
Table YES
| Marking the reference international standard |
The degree of compliance |
Designation and name of the relevant national standard |
| ISO 643:2003 | IDT | GOST R ISO 643−2011 «Steel. Metallographic determination of the observed grain size" |
| ISO 9042:1988 | IDT | GOST R ISO 9042−2011. «Steel. Manual method of counting points for the statistical evaluation of the volume fraction of the structural component using a point measurement grid». |
| Note: In this table used the symbol of compliance of the standards: IDT — identical standard. | ||
| UDC 669.14:620.2:006.354 | OKS 77.080 |
| Key words: steel-metallographic method determination of duplex grain size and distribution | |
