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GB/T 4340.1-2009 English PDF (GBT4340.1-2009)

GB/T 4340.1-2009 English PDF (GBT4340.1-2009)

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GB/T 4340.1-2009: Metallic materials -- Vickers hardness test -- Part 1: Test method

GB/T 4340.1-2009
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.040.10
H 22
Replacing GB/T 4340.1-1999
Metallic materials - Vickers hardness test -
Part 1: Test method
(ISO 6507-1:2005, MOD)
ISSUED ON: JUNE 25, 2009
IMPLEMENTED ON: APRIL 01, 2010
Issued by: General Administration of Quality Supervision, Inspection and Quarantine of the PRC;
Standardization Administration of the PRC.
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Normative references ... 5
3 Principle ... 6
4 Symbols and descriptions ... 6
5 Test apparatus ... 7
6 Test piece ... 8
7 Test procedure ... 8
8 Uncertainty of the results ... 10
9 Test report ... 10
Annex A (Normative) Minimum thickness of the test piece in relation to the test force and to the hardness ... 12
Annex B (Normative) Tables of correction factors for use in tests made on curved surfaces ... 14
Annex C (Informative) Periodic checking of the testing machine by the user 19 Annex D (Informative) Uncertainty of the measured hardness values ... 20 Foreword
GB/T 4340 "Metallic materials - Vickers hardness test" is divided into the following four parts:
- Part 1: Test method;
- Part 2: Verification and calibration of testing machines;
- Part 3: Calibration of reference blocks;
- Part 4: Tables of hardness values.
This Part is Part 1 of GB/T 4340.
This Part modifies and adopts the international standard ISO 6507-1:2005 "Metallic materials - Vickers hardness test - Part 1: Test method" (English edition).
This Part is redrafted according to ISO 6507-1:2005. According to China's actual situation, this Part has been revised and supplemented when adopting the international standard. These technical differences are marked with vertical single lines in the margins of the provisions they involve.
The structure and technical content of this Part are basically consistent with ISO 6507-1:2005. According to China's situation, it has been modified in the following aspects:
- Delete the foreword of the international standard;
- CHANGE the word "this International Standard" to "this Part";
- USE the decimal point "." instead of "," as the decimal point;
- ADD the description of Vickers microhardness test force;
- ADD a description of the error of duration of test force of special materials; - Modify the measurement uncertainty of the hardness value in Annex D of the source ISO 6507-1:2005.
This Part replaces GB/T 4340.1-1999 "Metallic materials - Vickers hardness test - Part 1: Test method". Compared with the previous standard, the following contents are modified:
- ADD the requirement of diagonal field of vision under the lens;
Metallic materials - Vickers hardness test -
Part 1: Test method
1 Scope
This Part of GB/T 4340 specifies the principle, symbols and descriptions, test apparatus, test piece, test procedure, uncertainty of the results and test report for metal Vickers hardness test.
This Part specifies the Vickers hardness test method, for the three ranges of test force for metals (see Table 1).
Table 1 -- Ranges of test force
The Vickers hardness test is specified in this Part for lengths of indentation diagonals between 0.020 mm and 1.400 mm.
Note 1: For indentation diagonals less than 0.020 mm, the increase of the uncertainty has to be considered.
Note 2: In general, decreasing the test force increases the scatter of results of the measurements. This is particularly true for low-force Vickers hardness tests and Vickers microhardness tests, where the principal limitation will arise in the measurement of the diagonals of the indentation. For Vickers microhardness, the accuracy of determination of the diagonals is unlikely to be better than ± 0.001 mm. The Vickers hardness test of specific materials or products shall be specified in the relevant standards.
2 Normative references
The following documents contain provisions which, through reference in this Part of GB/T 4340, constitute provisions of this Part. For the dated references, their subsequent amendments (excluding corrections) or revisions do not apply to this Part. However, the parties who enter into agreement based on this Part are encouraged to investigate whether the latest editions of these documents in Annex C.
6 Test piece
6.1 The test shall be carried out on a surface which is smooth and even, free from oxide scale, foreign matter and, in particular, completely free from lubricants, unless otherwise specified in product standards. The finish of the surface shall ensure the measurement accuracy of the diagonal length of the indentation. It is recommended that the surface of test piece be polished. 6.2 Preparation shall be carried out in such a way that any alteration of the surface hardness, due to excessive heating or cold-working, for example, is minimized.
6.3 Due to the small depth of Vickers microhardness indentations, when
processing the test piece, it is recommended to use a polishing/electropolishing process which is suitable for the material parameters.
6.4 The thickness of the test piece, or of the layer under test, shall be at least 1.5 times the diagonal length of the indentation (see Annex A). No deformation shall be visible at the back of the test piece after the test.
6.5 For tests on curved surfaces, the corrections given in Annex B, Tables B.1 to B.6 shall be applied.
6.6 For test pieces of small cross-section or of irregular shape, the test piece can be inlaid; or a special test bench can be used for testing.
7 Test procedure
7.1 The test is generally carried out at room temperature between 10 °C and 35 °C. For tests with strict temperature requirements, the room temperature shall be 23 °C ± 5 °C.
7.2 The test force shown in Table 3 shall be selected for the test.
Note: Other test forces can also be used, such as HV2.5 (24.52 N).
The arithmetic mean shall be used to calculate the Vickers hardness value according to Table 2. The Vickers hardness value can also be found according to GB/T 4340.4.
For flat surfaces, the difference between the lengths of two indentation diagonals should not be greater than 5 % of the mean diagonal length. If the difference is greater, this shall be stated in the test report.
Magnifications should be provided so that the diagonal can be enlarged to 25 % ~ 75 % of the field of view.
8 Uncertainty of the results
If necessary, a complete uncertainty evaluation shall be carried out in accordance with JJF 1059, the guideline for the expression of uncertainty in measurement. For the hardness test, there may be the following two methods evaluating the uncertainty of measurement:
- Based on the evaluation of all relevant uncertainty sub-items that occur in direct calibration.
- Based on indirect calibration using a hardness reference block (certified reference material). A guideline for the determination is given in Annex D. 9 Test report
The test report shall include the following information:
a) A reference to this Part of GB/T 4340;
b) Detailed description related to the test piece;
c) Test result;
d) All operations not specified in this Part;
e) Various details that affect the test result;
f) The temperature of the test, if it is outside the range specified in 7.1. Note 1: A strict comparison of hardness values is only possible at identical test forces. Note 2: There is no general process of accurately converting Vickers hardness into other scales of hardness or into tensile strength. Such conversions, therefore, should be avoided, unless a basis for conversion can be obtained by comparison tests. Annex C
(Informative)
Periodic checking of the testing machine by the user
Users shall, before using the testing machine that day, check the hardness scale or range they use.
Prior to making the check, the measuring system should be indirectly verified (for each range/scale and hardness level) using a reference indentation on a hardness reference block, calibrated in accordance with GB/T 4340.3. The measured dimension should agree with the standard value on the certificate of hardness reference block to within the maximum permissible error given in GB/T 4340.2. If the measuring system fails this test, appropriate action should be taken.
The check involves at least one indentation being made on a hardness
reference block, calibrated in accordance with GB/T 4340.3. If the difference between the mean measured hardness and the block's certified value is within the permissible error limits given in GB/T 4340.2, the machine may be regarded as satisfactory. If not, an indirect verification should be performed immediately. A record of these results should be maintained over a period of time, and used to monitor the reproducibility of the testing machine and the stability of the measuring equipment.

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