GB/T 13305-2024 English PDF (GB/T13305-2024)

GB/T 13305-2024: Method for determining content of the α-phase in stainless steels
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GB/T 13305-2024
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.040.99
CCS H 24
Replacing GB/T 13305-2008
Method for determining content of the α-phase in stainless
steels
ISSUED ON: MAY 28, 2024
IMPLEMENTED ON: DECEMBER 01, 2024
Issued by: State Administration for Market Regulation;
National Standardization Administration.
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Normative references ... 5
3 Terms and definitions ... 5
4 Selection and preparation of specimens ... 6
5 Determination method of α-phase content ... 10
6 Test report ... 15
Appendix A (Normative) Austenitic stainless steel α-phase content rating chart ... 16
Appendix B (Normative) Assessment diagram of austenite-ferrite duplex stainless steel
α-phase content ... 19
Foreword
This document was drafted in accordance with the provisions of GB/T 1.1-2020
"Directives for standardization - Part 1: Rules for the structure and drafting of
standardizing documents".
This document replaces GB/T 13305-2008 " Method for determining content of the α-
phase in stainless steels". Compared with GB/T 13305-2008, in addition to structural
adjustments and editorial changes, the main technical changes are as follows:
a) ADD the term and definition of "α-phase in stainless steel" (see Chapter 3);
b) CHANGE the schematic diagram of steel sampling method (see Figure 1; Figures
1 ~ 5 of the 2008 edition);
c) ADD the corrosion method of cupric chloride hydrochloric acid alcohol solution
[see 4.3a)];
d) ADD the mean value, standard deviation, confidence level, relative error formula
for the determination of α-phase content in austenitic-ferritic duplex stainless
steel (see 5.2.1.2; 4.1.2 of the 2008 edition);
e) CHANGE the magnification of the determination of α-phase content in austenitic
stainless steel (see 5.2.2.1; 4.1.1 of the 2008 edition);
f) CHANGE the comparison method rating limit table for the determination of α-
phase content in austenitic stainless steel (see 5.2.2.1; 4.1.1 of the 2008 edition);
g) ADD the table of α-phase types and contents in austenitic-ferritic duplex stainless
steel (see 5.2.2.2);
h) ADD the key operating instructions and calculation formulas for the quantitative
grid determination method (see 5.2.3);
i) ADD the key operating instructions for the automatic image analysis
determination method (see 5.2.4);
j) ADD the ferrite instrument determination method (see 5.3);
k) CHANGE the requirements for the content of the test report (see Chapter 6;
Chapter 5 of the 2008 edition);
l) CHANGE the standard rating chart for the metallographic determination method
of α-phase content in austenitic stainless steel (see Appendix A; Appendix A of
the 2008 edition);
m) CHANGE the standard evaluation chart for the metallographic determination
Method for determining content of the α-phase in stainless
steels
1 Scope
This document specifies the selection and preparation of specimens for the
determination of α-phase content in stainless steel, the determination method, the test
report.
This document is applicable to the determination of α-phase content in austenitic
stainless steel and austenitic-ferritic duplex stainless steel.
2 Normative references
The contents of the following documents constitute essential clauses of this document
through normative references in the text. Among them, for dated references, only the
version corresponding to that date applies to this document; for undated references, the
latest version (including all amendments) applies to this document.
GB/T 1954 Methods of measurement for ferrite content in austenitic Cr-Ni stainless
steel weld metals
GB/T 13298 Inspection methods of microstructure for metals
GB/T 15749 Measuring method in quantitative metallography
GB/T 18876.1 Standard practice for determining the metallographical constituent
and inclusion content of steels and other metals by automatic image analysis - Part
1: Determining the inclusion or second-phase constituent content of steels and other
metals by automatic
GB/T 30067 Standard terminology relating to metallography
YB/T 4402 Micrographic method for determining content of δ-ferrite in martensitic
stainless steel
3 Terms and definitions
The terms and definitions defined in GB/T 30067 and the following terms and
definitions apply to this document.
3.1
α-phase in stainless steel
The ferrite phase in stainless steel, which has a body-centered cubic (bcc) crystal
structure.
Note 1: Ferrite is an interstitial solid solution with a body-centered cubic structure formed
by carbon dissolving in α-Fe or δ-Fe.
Note 2: The α-phase in the austenitic stainless steel and austenitic-ferrite duplex stainless
steel covered in this document actually also contains δ-phase, collectively referred to as α-
phase.
4 Selection and preparation of specimens
4.1 General
4.1.1 The specimens are cut from the steel in the delivery state. The sampling location
and quantity shall be in accordance with the relevant product standards or agreements.
4.1.2 The test surface of the specimen of rolled steel is a longitudinal section parallel to
the rolling direction, wherein one side shall coincide with its axis. The orientation of
the test surface of forgings and other specimens without obvious axes shall be in
accordance with the relevant product standards or agreements. The area of the test
surface of the specimen shall not be less than 10 mm2. Steels with special dimensions
are allowed to be divided into several pieces; these specimens are regarded as one
specimen.
4.1.3 The specimens shall be cut mechanically in a cold state. If cutting is done by gas
cutting or hot cutting, the metal melting zone, plastic deformation zone, heat affected
zone shall be completely removed. The distance between the cutting surface and the
inspection surface depends on the cutting method, which is generally not less than 0.5
mm.
4.2 Sampling method
4.2.1 Sampling method for round steel and square steel
4.2.1.1 For steel with a nominal diameter or side length greater than 40 mm, the
inspection surface is the longitudinal section through the axis of the steel, one side of
which coincides with the axis of the steel, see Figure 1a).
4.2.1.2 The sampling method for round steel and square steel, which has a nominal
diameter or side length less than or equal to 40 mm, is as follows:
a) For steel with a nominal diameter or side length of > 30 mm ~ 40 mm, the
d) Etching with ferric chloride hydrochloric acid ethanol aqueous solution:
Ferric chloride (FeCl3) 5 g, hydrochloric acid (HCl) 100 mL, ethanol (C2H5OH)
100 mL, water 100 mL.
After etching at room temperature, heat the specimen to 500 °C ~ 600 °C until the
corrosion surface turns yellow and the α-phase turns brown.
e) Oxalic acid electrolytic etching:
Oxalic acid (H2C2O4) 10 g, water 100 mL. Etching voltage is 3 V ~ 12 V, etching
time is 15 s ~ 45 s.
f) Potassium (sodium) hydroxide electrolytic etching:
Potassium (sodium) hydroxide (NaOH or KOH) 20 g, water 100 mL. Etching
voltage is 2 V ~ 20 V, etching time is 5 s ~ 20 s.
5 Determination method of α-phase content
5.1 General
5.1.1 The following method is usually used to determine the α-phase content of steel.
The method used is determined by the product standard or the agreement between the
two parties.
a) Metallographic method (see 5.2), including three specific methods: standard
rating chart method, quantitative grid determination method, automatic image
analysis determination method.
b) Ferrite instrument method (see 5.3), a rapid and non-destructive determination
method.
5.1.2 The choice of determination method and its accuracy depend on the product type,
microstructure, shape of the component. The influence of second phases such as
intermetallic compounds shall be removed during the determination, but the δ-phase in
austenitic stainless steel and austenitic-ferrite duplex stainless steel should be included
in the statistics. The δ-ferrite content in martensitic stainless steel is determined in
accordance with YB/T 4402. The α-phase content in the weld of chromium-nickel
austenitic stainless steel is determined in accordance with GB/T 1954.
5.2 Metallographic method
5.2.1 General
5.2.1.1 Determination of α-phase content in austenitic stainless steel
accordance with GB/T 15749. Generate several parallel and vertical line segments on
the collected photos, to form an equally spaced grid (the grid spacing shall be close to
the width of the α-phase and the number of grids shall be no less than 7×7), covering
the entire field of view. The interception point falling within the α-phase is calculated
as 1 point; the interception point falling on the phase boundary is calculated as 1/2 point.
According to formula (5), the percentage -- of the number of grid interception points
falling on the α-phase TO the total number of grid interception points -- is calculated as
the α-phase content.
Where:
Vα,i - α-phase content in each field of view, %;
Pα,i - Number of interception points falling within the α-phase or phase boundary;
Pt - Number of interception points in the entire grid.
5.2.4 Automatic image analysis determination method
The automatic image analysis determination method is used to determine the α-phase
content in accordance with GB/T 18876.1. The α-phase in stainless steel is the
characteristic object to be detected; identification and detection are carried out by
comparing the grayscale difference between the α-phase and the matrix. When adjusting
the grayscale threshold value by the flicker method, it shall be ensured that the α-phase
extraction is sufficient and complete. The α-phase content test result of the automatic
image analysis determination method shall be accurate to 0.1%.
5.3 Ferrite meter determination method
For special cases such as on-site rapid inspection, the ferrite meter can be used to
evaluate the α-phase content in stainless steel after mutual agreement. This method
cannot be used as an arbitration method. The ferrite meter and its own proofing samples
shall be calibrated regularly (usually no more than one year), using a Magni meter or a
secondary standard sample. Before the measurement, a standard sample with the same
α-phase content as the sample to be tested shall be used to calibrate the ferrite meter.
The surface oil and rust layer of the inspection surface shall be removed. When
measuring the α-phase content in austenitic stainless steel, at least 5 positions shall be
measured to obtain the maximum value. When measuring the α-phase content in
austenitic-ferrite duplex stainless steel, at least 5 positions shall be measured to obtain
the average value. The test location and quantity shall be determined according to the
corresponding product standards or by mutual agreement.
GB/T 13305-2024
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.040.99
CCS H 24
Replacing GB/T 13305-2008
Method for determining content of the α-phase in stainless
steels
ISSUED ON: MAY 28, 2024
IMPLEMENTED ON: DECEMBER 01, 2024
Issued by: State Administration for Market Regulation;
National Standardization Administration.
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Normative references ... 5
3 Terms and definitions ... 5
4 Selection and preparation of specimens ... 6
5 Determination method of α-phase content ... 10
6 Test report ... 15
Appendix A (Normative) Austenitic stainless steel α-phase content rating chart ... 16
Appendix B (Normative) Assessment diagram of austenite-ferrite duplex stainless steel
α-phase content ... 19
Foreword
This document was drafted in accordance with the provisions of GB/T 1.1-2020
"Directives for standardization - Part 1: Rules for the structure and drafting of
standardizing documents".
This document replaces GB/T 13305-2008 " Method for determining content of the α-
phase in stainless steels". Compared with GB/T 13305-2008, in addition to structural
adjustments and editorial changes, the main technical changes are as follows:
a) ADD the term and definition of "α-phase in stainless steel" (see Chapter 3);
b) CHANGE the schematic diagram of steel sampling method (see Figure 1; Figures
1 ~ 5 of the 2008 edition);
c) ADD the corrosion method of cupric chloride hydrochloric acid alcohol solution
[see 4.3a)];
d) ADD the mean value, standard deviation, confidence level, relative error formula
for the determination of α-phase content in austenitic-ferritic duplex stainless
steel (see 5.2.1.2; 4.1.2 of the 2008 edition);
e) CHANGE the magnification of the determination of α-phase content in austenitic
stainless steel (see 5.2.2.1; 4.1.1 of the 2008 edition);
f) CHANGE the comparison method rating limit table for the determination of α-
phase content in austenitic stainless steel (see 5.2.2.1; 4.1.1 of the 2008 edition);
g) ADD the table of α-phase types and contents in austenitic-ferritic duplex stainless
steel (see 5.2.2.2);
h) ADD the key operating instructions and calculation formulas for the quantitative
grid determination method (see 5.2.3);
i) ADD the key operating instructions for the automatic image analysis
determination method (see 5.2.4);
j) ADD the ferrite instrument determination method (see 5.3);
k) CHANGE the requirements for the content of the test report (see Chapter 6;
Chapter 5 of the 2008 edition);
l) CHANGE the standard rating chart for the metallographic determination method
of α-phase content in austenitic stainless steel (see Appendix A; Appendix A of
the 2008 edition);
m) CHANGE the standard evaluation chart for the metallographic determination
Method for determining content of the α-phase in stainless
steels
1 Scope
This document specifies the selection and preparation of specimens for the
determination of α-phase content in stainless steel, the determination method, the test
report.
This document is applicable to the determination of α-phase content in aus...