GB/T 40304-2021 (GB/T40304-2021, GBT 40304-2021, GBT40304-2021) & related versions
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Determination of content of nonmetallic inclusions in steel -- Billet full section method
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GB/T 40304-2021
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GB/T 40304-2021
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.040.99
CCS H 24
Determination of Content of Nonmetallic Inclusions in Steel
– Billet Full Section Method
ISSUED ON: AUGUST 20, 2021
IMPLEMENTED ON: MARCH 01, 2022
Issued by: State Administration for Market Regulation;
Standardization Administration of the People’s Republic of China.
Table of Contents
Foreword ... 3
Introduction ... 4
1 Scope ... 6
2 Normative References ... 6
3 Terms and Definitions ... 6
4 Principle ... 7
5 Sample Preparation ... 8
6 Test Equipment ... 8
7 Test Method ... 9
8 Test Report ... 11
Appendix A (Informative) An Example of the Test of Non-Metallic Inclusions in the
Full Section of the Continuous Casting Slab for Ship Plate ... 12
Determination of Content of Nonmetallic Inclusions in Steel
– Billet Full Section Method
1 Scope
This Document specifies the principles, specimen preparation, test equipment, test methods and
test reports for the content of non-metallic inclusions in billets.
This Document is applicable to the test of non-metallic inclusions (with dimensions no less than
30μm) in billets that have not been rolled, deformed or otherwise treated. Non-metallic
inclusions with a size less than 30μm can also be used for reference when the equipment allows.
2 Normative References
The provisions in following documents become the provisions of this Document through
normative reference in 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) is applicable to this Document.
GB/T 226 Test Method for Macrostructure and Defect of Steel by Etching
GB/T 4236 Steel - Examination by Sulphur Print
3 Terms and Definitions
For the purposes of this Document, the following terms and definitions apply.
3.1 Mirror surface sample
The billet full section specimen with the roughness Rα in the parallel machining direction of
less than 0.02μm, and the roughness Rα in the vertical machining direction of less than 0.05μm.
NOTE 1: The width of the mirror specimen corresponds to the width of the billet, and the thickness of
the mirror specimen corresponds to the thickness of the billet.
NOTE 2: The parallel processing direction corresponds to the sample width, and the vertical processing
direction corresponds to the mirror surface sample thickness.
3.2 Suspected defect feature points
Defects such as bubbles and shrinkage holes on the surface of the mirror surface sample (3.1)
5 – reflected light;
6 – scattered light.
Figure 1 – Schematic Diagram of Collection Principle of Suspected Defect Feature Point
5 Sample Preparation
5.1 Sample-billet cutting
The cutting of the sample-billet is carried out according to the provisions of GB/T 226 and
GB/T 4236. The continuous casting billet sample shall be clearly marked on the inner arc or
outer arc side; and ensure that it is clearly visible during processing, measurement and
preservation.
5.2 Sample processing
The sample-billet is processed into a mirror surface sample through several processes such as
milling, grinding, ultra-fine grinding or polishing, etc.
5.3 Preservation of mirror surface sample
The mirror surface sample shall be stored in a dry and clean space; and the ambient humidity
shall be less than 60% to prevent the test surface of the sample from becoming dark, polluted,
and rusted, and not to affect the test results.
6 Test Equipment
6.1 Imaging system
The imaging system shall acquire and image the detection surface of the mirror surface sample
at one time. The collected pictures shall be free of distortion and the resolution should be no
greater than 30μm.
NOTE: The minimum size of non-metallic inclusions that can be resolved is determined by the resolution
of the line scan camera.
6.2 Imaging analysis system
The imaging analysis system shall be able to perform statistical analysis on the suspected defect
feature points in the collected picture, and it should have the following functions:
a) Automatically complete the coordinate recording, quantity counting and size
measurement of all suspected defect feature points in the collected picture;
b) Give the distribution map of the suspected defect feature points on the inspection surface
of the mirror surface sample;
c) Establish a database of test results and a remote online analysis system.
6.3 Microscopic analysis system
The microscopic analysis system shall be equipped with a mobile metallographic microscope
for microscopic detection and analysis of suspected defect feature points, and it should have
the following functions:
a) Perform two-dimensional movement and Z-direction macro movement focusing
functions on the surface of mirror surface sample;
b) Complete automatic positioning, focusing and photographing functions for multiple
suspected defect feature points;
c) Multi-magnification observation function, the maximum magnification is no less than
100X;
d) Dark field, polarized light, differential interference and other functions.
7 Test Method
7.1 Establishing the coordinate system
7.1.1 Before testing, align the test surface of the mirror surface sample with the imaging system
in the test equipment; adjust the test surface of the mirror surface sample to the horizontal; and
establish a coordinate system on the mirror surface sample.
7.1.2 The coordinate system of rectangular billet and square billet takes the width direction of
the mirror surface sample as the X-axis and the thickness direction as the Y-axis [see Figure
2a)].
7.1.3 The circular billet coordinate system takes the center of the mirror surface sample as the
origin; and the two mutually perpendicular diameters as the coordinate axes, where the
intersection between the X-axis and the edge of the circular billet can be the tangent point of
the outer arc or the inner arc of the circular billet continuous casting [ See Figure 2b)].
7.1.4 The coordinate identification on the sample shall be clear and complete, to ensure that
after the mirror surface sample leaves the test equipment, the coordinate system can still be
established based on the coordinate identification and the coordinates of the suspected defect
feature points can be confirmed.
7.5 Establishing a database of non-metallic inclusions
Retain the analyzed pictures of non-metallic inclusions; establish a database of non-metallic
inclusions; and output a summary table of non-metallic inclusions. The summary table shall
include the serial numbers, coordinates and sizes of non-metallic inclusions.
7.6 Test example
See Appendix A for an example of testing the non-metallic inclusion content in the full section
of the continuous casting slab for ship plate.
8 Test Report
The test report shall include but not be limited to the following contents:
a) this Document number;
b) product standard or contract number;
c) sample-billet name, designation, specification, furnace number and batch number, etc.;
d) sample size and test area;
e) test equipment and test personnel;
f) summary table of non-metallic inclusions;
g) distribution map of non-metallic inclusions;
h) Report number and date.
......
| Standard ID | GB/T 40304-2021 (GB/T40304-2021) | | Description (Translated English) | Determination of content of nonmetallic inclusions in steel -- Billet full section method | | Sector / Industry | National Standard (Recommended) | | Classification of Chinese Standard | H24 | | Classification of International Standard | 77.040.99 | | Word Count Estimation | 14,140 | | Date of Issue | 2021-08-20 | | Date of Implementation | 2022-03-01 | | Drafting Organization | Qiqihar China Industrial Machine Tool Co., Ltd., Shougang Group Co., Ltd., Institute of Metal Research, Chinese Academy of Sciences, Baowu Equipment Intelligent Technology Co., Ltd., Shougang Co., Ltd. Qian'an Iron and Steel Company, Central Iron and Steel Research Institute, Minmetals Yingkou Medium Plate Co., Ltd., Hengyang Radium Eye Technology Co., Ltd., Metallurgical Industry Information Standards Research Institute | | Administrative Organization | National Steel Standardization Technical Committee (SAC/TC 183) | | Proposing organization | China Iron and Steel Association | | Issuing agency(ies) | State Administration for Market Regulation, National Standardization Administration |
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