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GB/T 6394-2017 PDF in English

GB/T 6394-2017 (GB/T6394-2017, GBT 6394-2017, GBT6394-2017)
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Standards related to: GB/T 6394-2017

GB/T 6394-2017: PDF in English (GBT 6394-2017)

GB/T 6394-2017
ICS 77.040.99
H 24
Replacing GB/T 6394-2002
Determination of estimating
the average grain size of metal
Issued by. General Administration of Quality Supervision, Inspection and
Quarantine of the People's Republic of China;
Standardization Administration of PRC.
Table of contents
Foreword ... 3
Introduction ... 5
1 Scope ... 6
2 Normative references ... 6
3 Terms and definitions ... 7
4 Symbols... 8
5 Overview and application ... 10
6 Sampling ... 12
7 Sample preparation ... 12
8 Determination method ... 13
9 Grain size of non-equiaxed grain ... 26
10 Grain size of sample containing two or more phase structures ... 29
11 Grain size report ... 31
12 Precision and deviation ... 32
Appendix A (Normative) Grain size formation and display method ... 34
Appendix B (Normative) Statistical technique - Calculation of confidence
interval and relative error of grain size measurement results ... 41
Appendix C (Informative) Grain size measurement basis ... 45
This standard was drafted in accordance with the rules given in GB/T
This standard replaces GB/T 6394-2002 “Determination of estimating the
average grain size of metal”.
As compared with GB/T 6394-2002, the main technical changes of this
standard are as follows.
- ADD the terms and definitions of grain boundary, grain boundary
intersection count, and intercept length (SEE Chapter 3);
- ADD the heat treatment method, sampling location, sampling orientation,
polishing area requirements, and sample preparation requirements for the
samples forming the austenite grains (SEE Chapter 6, Chapter 7);
- In the comparison method, ADD the requirements for the inspection
parameters, view field selection, and rating operations details (SEE 8.1);
- ADD the requirements that the cementite outling grain display may use the
pattern IV (SEE Table 2 in;
- MODIFY the values of the grain diameter and magnification corresponding
to 400-timess and 500-timess rating chart; ADD the conversion values of
500-timess and 1000-timess the rating chart (SEE Table 3 and Table 4 of;
- In the area method, ADD the calculation formula of the rectangular
measurement network; ADD the methods of field selection and counting
precision (SEE 8.2.2);
- MODIFY the contents of the intersection method; ADD the various
calculation formulas of the intersection method (SEE;
- ADD the calculation method of the non-equiaxed grains; DEFINE the
calculation process (SEE Chapter 9);
- As for the assessment of the two-phase and multi-phase grains, ADD the
requirements for the determination report of the phase characteristics and
proportion; ADD the intercept method (SEE 10.4.3);
- ADD the report content requirements for the basic data, non-equiaxed
grains, and multi-phase grain through the area method and the intersection
method; IMPROVE the grain size report (SEE Chapter 11);
- ADD the precision and deviation requirements (SEE Chapter 12);
Determination of estimating
the average grain size of metal
1 Scope
1.1 This standard specifies the expression and determination methods of the
average grain size of metal structure, including the comparison method, area
method and interception method; it is applicable to the single-phase structure;
however, after being specified, it is also applicable to the determination of the
average grain size of the certain type in the multi-phase or multi-component
sample. If the histomorphology of the non-metallic material is similar to the
metal structure in the rating chart, it may also make reference to it.
1.2 This standard uses the grain area, diameter or intercept length of the
unimodal distribution (similar to the lognormal distribution) to determine the
average grain size of the sample, AND it is not applicable to the grain size of
the bimodal distribution. The evaluation of double grain size is as shown in
GB/T 24177. For the determination of individual coarse grains on a fain grain
substrate, SEE YB/T 4290.
1.3 This standard applies only to the measurement of the plane grain size
measurement, AND it is not applicable to the three-dimensional grain size, that
is, the measurement of three-dimensional grain size.
1.4 This standard is only used as a recommended test method, AND it shall
cannot determine whether the test material is received or suitable for the range
of use.
2 Normative references
The following documents are essential to the application of this document. For
the dated documents, only the versions with the dates indicated are applicable
to this document; for the undated documents, only the latest version (including
all the amendments) are applicable to this Standard.
GB/T 4335 Determination of ferrite grain size for cold rolled low carbon steel
GB/T 13298 Inspection methods of microstructure for metals
GB/T 24177 Standard test methods for characterizing duplex grain sizes
GB/T 30067 Standard terminology relating to metallography
YB/T 4290 Test methods for estimating the largest grain observed in a
metallographic section (ALA grain size)
3 Terms and definitions
The terms and definitions as defined in GB/T 30067 AND the following terms
and definitions apply to this document.
Grain boundary
It refers to, for the polycrystalline material, a narrow region transitioning from
one crystal direction to the other crystal direction, thereby separating the
adjacent grains.
It refers to the entire area surrounded by grain boundaries, that is, the area
within the original grain boundary observed on the two-dimensional plane,
or the volume surrounded by the original grain boundery on the
three-dimensional object. For twin-grain boundary materials, the twin-grain
boundary is not considered.
Grain size
It refers to the measurement of the size of grain, which is evaluated or
determined by different methods, is usually expressed using the length,
area, volume, or grain size level, AND the grain size as expressed using the
grain size level is independent of the measurement method and the unit of
Micro-grain size number
The micro-grain size number G is defined as.
Macro-grain size number
Through reasonable count, it may reach to the precision of ± 0.25 level. The
results of the area method are unbiased, AND its reproducibility and
repeatability are less than ± 0.5 level. The key to the precision of the area
method is that during counting, it must indicate the counted grain.
5.4 Intersection method. intersection method is to count the number of the
intercept between the test line (or grid) of known length and the grain or the
number of intersection between the test line (or grid) and the grain, AND to
calculate the unit length intercept count NL or the intersection count PL, so as
to determine the grain size level G. The precision of the intersection method is
a function of the intersection or intercept count, which can achieve a precision
of better than ± 0.25 level by an effective count. The results of the intersection
method are unbiased, AND the reproducibility and repeatability are less than ±
0.5 level. For the same level of precision, since the intersection method can
count accurately without the need of marking, it is faster than the area method.
5.5 For equiaxed grain samples, it is convenient and practical to use the
comparison method to evaluate the grain size. For the inspection of mass
production, its precision is sufficient. For the determination of the average grain
size requiring for higher precision, it may use the area method and the
intersection method. The intersection method is more effective for the sample
of elongated grain composition.
5.6 In the event of a dispute, the intersection method is used as the arbitration
5.7 Low-carbon steel cold-rolled sheet ferrite grain size is determined in
accordance with the provisions of GB/T 4335.
5.8 A single grain cannot be determined on the basis of the standard rating
chart. Because the composition of the standard rating chart takes into account
the relationship between the cut plane and the grain three-dimensional
arrangement, it shows the arrangement distribution of grain from the minimum
to the maximum, which reflects the representative normal distribution results.
Therefore, the rating chart cannot be used to determine a single grain.
5.9 When determining the grain size, it shall be recognized that the
determination of grain size is not a ve...
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.