GB/T 34474.2-2018 PDF in English
GB/T 34474.2-2018 (GB/T34474.2-2018, GBT 34474.2-2018, GBT34474.2-2018)
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Determination of banded structure of steel -- Part 2: Quantitative method
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Standards related to (historical): GB/T 34474.2-2018
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GB/T 34474.2-2018: PDF in English (GBT 34474.2-2018) GB/T 34474.2-2018
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.040.99
H 24
Determination of Banded Structure of Steel -
Part 2: Quantitative Method
ISSUED ON: MAY 14, 2018
IMPLEMENTED ON: FEBRUARY 1, 2019
Issued by: State Administration for Market Regulation;
Standardization Administration of the People’s Republic of
China.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative References ... 4
3 Terms and Definitions ... 4
4 Symbol ... 5
5 Equipment ... 6
6 Sampling ... 7
7 Sample Preparation ... 7
8 Analytical Procedures ... 7
9 Test Report ... 13
Appendix A (informative) An Example of Quantitative Analysis of Banded
Structure: Quantitative Determination of Q235 Banded Structure ... 14
Appendix B (informative) Examples of Quantitative Results of Different Types
of Structure ... 19
Determination of Banded Structure of Steel -
Part 2: Quantitative Method
1 Scope
This Part of GB/T 34474 stipulates the qualitative description, classification and
quantitative determination methods for banded structure of steel.
This Part is applicable to the determination of banded structure of steel, including the
determination of parameters, such as: orientation degree, anisotropy index, the
number of banded structures per unit length, and the distance among banded
structures, etc. Other oriented structures may take this as a reference.
2 Normative References
The following documents are indispensable to the application of this document. In
terms of references with a specified date, only versions with a specified date are
applicable to this document. In terms of references without a specified date, the latest
version (including all the modifications) is applicable to this document.
GB/T 13298 Inspection Methods of Microstructure for Metals
GB/T 15749 Measuring Method in Quantitative Metallography
GB/T 30067 Standard Terminology Relating to Metallography
GB/T 34474.1 Determination of Banded Structure of Steel - Part 1: Micrographic
Method Using Standards Diagrams
3 Terms and Definitions
What is defined in GB/T 30067, and the following terms and definitions are applicable
to this document.
3.1 Feature Interceptions
Feature interceptions refers to the number of banded structures crossed by the
measurement grid lines (see N and N in Figure 1).
3.2 Feature Intersections
Feature intersections refers to the number of banded structure boundaries crossed by
be used to count and quantify the banded structure images with scale.
6 Sampling
6.1 Under general circumstances, samples shall be intercepted from products under
the delivery state.
6.2 In terms of plates, samples shall be intercepted at 1/4 of the plate width.
6.3 The inspection area of the samples is approximately 200 mm2 (20 mm 10 mm).
The inspection surface shall be parallel to the main deformation direction of the rolled
steel.
6.4 Sampling methods and sampling size shall comply with the stipulations of product
standards or technical conditions. If they are not specified in product standards or
technical conditions, then, comply with GB/T 34474.1.
7 Sample Preparation
The grinding and erosion of sample shall comply with the stipulations of GB/T 13298.
After grinding and polishing, the observation surface of the sample shall reach mirror
finish and manifest no stains or scratches. After the polishing, use 4% nitric acid alcohol
to erode the sample for 10 s ~ 15 s. Then, blow dry it for later usage.
8 Analytical Procedures
8.1 Image Acquisition
Place the prepared sample on the object stage; adjust the sample, so that the banded
structures are in the horizontal direction. Generally speaking, 5 X ~ 20 X objective lens
are selected. Under the condition that the phase structures can be clearly distinguished,
and the grain boundaries are clear, select the magnification as small as possible for
observation. In accordance with the agreement between the demand-side and the
supply-side, objective lens of other magnifications may also be selected. Under
general circumstances, the distribution, the degree of aggregation and the width of
banded structures vary greatly in the longitudinal section. Thus, the evaluation location
of banded structures shall be specified in product standards or the agreement between
the demand-side and the supply-side. At the evaluation location, randomly collect more
than 5 field-of-view photos.
8.2 Qualitative Description and Classification
8.2.1 General rules
not be selected with deflection. Avoid measurement lines that are merely distributed in
the local matrix phase of the field of view, or merely on two limited banded structures.
8.3.3 Counting of feature interceptions and intersections
When two or more adjacent grains in the banded structure are crossed by the
measurement line, in other words, there is no other phase between the grains, then, it
shall be recorded as one interception (N = 1) or two intersections (P = 2). When the
measurement line is tangent to the banded structure, it shall be recorded as a half
interception (N = 0.5) or one intersection (P = 1). If the measurement line ends within
the banded structure, it shall be recorded as a half interception (N = 0.5) or one
intersection (P = 1). If the measurement line is completely within the banded structure
(this circumstance sometimes occurs in the counting of the parallel direction of highly
banded structures), it shall be recorded as a half interception (N = 0.5) or zero
intersection (P = 0). It is feasible to merely count the number of feature interceptions
or feature intersections. Or, the counting of feature interceptions and feature
intersections may be simultaneously conducted. The number of feature interceptions
and feature intersections shall be respectively counted for the measurement line
parallel to the deformation direction and perpendicular to the deformation direction.
8.3.4 Calculation of feature interceptions and (or) intersections per unit length
Respectively measure the total length Lt of the inspection line parallel to the
deformation direction and the total length Lt of the inspection line perpendicular to the
deformation direction in a single field of view. In accordance with Formula (1) ~ Formula
(4), calculate NL, NL , PL , PL.
8.3.5 Calculation of average value of multiple fields of view
Calculate the average value of feature interceptions and feature intersections of
multiple fields of view (n): NL, NL , PL, PL . In terms of highly banded
microstructure, NL approximately equals to a half of PL.
8.3.6 Calculation of standard error S
In accordance with Formula (5), calculate the standard error of each measured value
when %RA is not more than 30%, the measurement result is valid. If %RA is more than
30%, the number of fields of view shall be increased, till %RA is not more than 30%.
Generally, the relative accuracy of the measurement results in the parallel deformation
direction is worse than that in the vertical deformation direction. When the number of
fields of view is fixed, the statistical accuracy of coarse-grained structure is usually
better than that of fine-grained structure. The accuracy of isotropic structure is better
than the statistical accuracy of highly banded structure.
8.3.9 Calculation of average band spacing (SB)
It is the average distance from the center of banded structure to the center of adjacent
banded structure. It may be determined through the reciprocal of NL [Formula (8)]:
8.3.10 Calculation of mean free path ()
Mean free path (the distance from the edge of banded structure to the edge of adjacent
banded structure) may be calculated in accordance with Formula (9):
In Formula (9), VV is the volume fraction of banded structure, which needs to be
determined through grid point method (comply with GB/T 15749) or other applicable
methods.
In accordance with the difference between the average band spacing and the mean
free path, the width of banded structure may be estimated. In terms of highly banded
structure, SB and may be calculated.
8.3.11 Calculation of anisotropy index AI
Calculate anisotropy index AI in accordance with Formula (10). If the tangent of the
banded structure to the grid line, and the counting error are neglected, PL shall be
approximately twice NL. Therefore, the AI values respectively calculated in accordance
with feature interceptions and feature intersection are approximately equal. The
anisotropy index AI of randomly distributed, non-oriented structures is 1. As the degree
of banding becomes aggravated, the anisotropy index AI gradually increases.
or
8.3.12 Calculation of orientation degree 12
Calculate orientation degree 12 in accordance with Formula (11). If the tangent of the
banded structure to the grid line, and the counting error are neglected, PL shall be
approximately twice NL. Therefore, the 12 values respectively calculated in
accordance with feature interceptions and feature intersection are approximately equal.
Orientation degree 12 varies between 0 (completely random distribution) and 1
(completely banded).
8.3.13 Example
Appendix A provides an example of quantitative analysis.
9 Test Report
9.1 The report shall record the designation, sampling location, status, date of analysis,
operator, location of fields of view, number of fields of view and magnification of
samples.
9.2 Describe the classification and distribution of banded structures.
9.3 List out the average value, standard deviation, 95% confidence interval, relative
accuracy percentage %RA, anisotropy index AI and orientation degree 12 of the
measured values (NL, NL , PL, PL ). In terms of relatively severe banded structure,
band spacing SB and of the banded structure may be provided. The measurement
result shall be provided in the form of a table (as it is shown in Table A.3). In the table,
Vv, SB and data may retain three decimal places; other data shall retain two
decimal places. Appendix B provides examples of quantitative results of some steels.
or
......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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