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GB/T 231.1-2018 English PDF (GBT231.1-2018)

GB/T 231.1-2018 English PDF (GBT231.1-2018)

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GB/T 231.1-2018: Metallic materials -- Brinell hardness test -- Part 1: Test method

This Part of GB/T 231 specifies the principle, symbols and descriptions, test apparatus, test piece, test procedure, uncertainty of the results and test report of the Brinell hardness test for metallic materials. This Part applies to both fixed location Brinell hardness testers and portable Brinell hardness testers. For the Brinell hardness test for special materials or products, it may refer to GB/T 9097 and this Part.
GB/T 231.1-2018
GB
NATIONAL STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
ICS 77.040.10
H 22
Replacing GB/T 231.1-2009
Metallic materials - Brinell hardness test -
Part 1. Test method
(ISO 6506-1.2014, MOD)
ISSUED ON. MAY 14, 2018
IMPLEMENTED ON. FEBRUARY 01, 2019
Issued by. State Administration for Market Regulation;
Standardization Administration of the People's Republic of
China.
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Normative references ... 5
3 Principle ... 5
4 Symbols and descriptions ... 6
5 Test apparatus ... 7
6 Test piece ... 8
7 Test procedure ... 8
8 Uncertainty of the results ... 11
9 Test report ... 12
Annex A (normative) Minimum thickness of the test piece in relation to the mean diameter of indentation ... 13
Annex B (normative) Procedure for daily checking of the hardness tester by the user ... 15
Annex C (informative) Uncertainty of the measurement of hardness values . 16 Bibliography ... 24
Foreword
GB/T 231 ?€?Metallic materials - Brinell hardness test?€? consists of 4 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 231.
This Part is drafted in accordance with the rules given in GB/T 1.1-2009. This Part replaces GB/T 231.1-2009 ?€?Metallic materials - Brinell hardness test - Part 1. Test method?€?, and compared with GB/T 231.1-2009, the main technical changes are as follows.
- ADD reference to JJG 150 ?€?Verification regulation of metal Brinell hardness tester?€? (see Clause 5);
- ADD the requirement of ?€?Before the test, the condition of the hardness tester shall be checked in accordance with Annex B.?€? (see 7.2);
- ADD ?€?If the diameter of the indentation lies outside the above-mentioned limits, the ratio of indentation diameter to indenter diameter, d/D, shall be stated in the test report.?€? (see 7.4);
- SPECIFY that the optical measurement of the indentation diameter can be performed with either a manual or an automatic measuring system (see 7.9 of this Part, 7.8 of 2009 edition);
- ADD the rounding off requirements for hardness results (see 7.10 of this Part, 7.9 of the 2009 edition);
- MODIFY the informative Annex B as a normative annex (see Annex B of
this Part, Annex A of the 2009 edition);
- MODIFY the uncertainty of the measurement of hardness values (see
Appendix C).
This Part uses the redrafting method to modify ISO 6506-1.2014 ?€?Metallic materials - Brinell hardness test - Part 1. Test method?€?.
The structure of this Part is basically consistent with ISO 6506-1.2014. There Metallic materials - Brinell hardness test -
Part 1. Test method
1 Scope
This Part of GB/T 231 specifies the principle, symbols and descriptions, test apparatus, test piece, test procedure, uncertainty of the results and test report of the Brinell hardness test for metallic materials.
This Part applies to both fixed location Brinell hardness testers and portable Brinell hardness testers. For the Brinell hardness test for special materials or products, it may refer to GB/T 9097 and this Part.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 231.2-2012 Metallic materials - Brinell hardness test - Part 2.
Verification and calibration of testing machines (GB/T 231.2-2012, ISO 6506- 2.2005, MOD)
GB/T 231.3 Metallic materials - Brinell hardness test - Part 3. Calibration of reference blocks (GB/T 231.3-2012, ISO 6506-3.2005, MOD)
GB/T 231.4 Metallic materials - Brinell hardness test - Part 4. Tables of hardness values (GB/T 231.4-2009, ISO 6506-4. 2005, IDT)
GB/T 9097 Sintered metal materials, excluding hard metals - Determination of apparent hardness and micro-hardness (GB/T 9097-2016, ISO 4498.2010, IDT)
JJG 150 Verification regulation of metal Brinell hardness tester
3 Principle
3.1 A tungsten carbide composite ball with certain diameter, D, is forced into the surface of a test piece with a test force, F. After the prescribed duration time, 7.7 Throughout the test, the hardness tester shall be protected from shock or vibration, which can influence the test result.
7.8 The distance from the edge of the test piece to the centre of each
indentation shall be at least 2.5 times the mean indentation diameter. The distance between the centres of two adjacent indentations shall be at least 3 times the mean indentation diameter.
7.9 The optical measurement of the indentation diameter can be performed with either a manual or an automatic measuring system. The visual field for the optical measuring device shall be evenly illuminated, and the condition of illumination shall be unchanged from that used during the hardness tester?€?s direct and indirect verifications and its daily verification. The two measuring methods are as follows.
a) For manual measuring systems, measure the diameter of each
indentation in two directions approximately perpendicular to each other. The arithmetic mean of the two readings shall be taken for the calculation of the Brinell hardness. For test pieces with a ground surface, it is
recommended that the direction of the indentation measurements be at
approximately 45?? to the direction of grinding.
NOTE. It shall be noted that for anisotropic materials, for example those which have been heavily coldworked, there might be a difference between the lengths of the two diameters of the indentation. The specification for the product might indicate limits for such differences. b) For automatic measuring systems, other validated algorithms to compute the mean diameter are allowed. These algorithms include
- the average of a greater number of measurements;
- a measurement of the projected area of the indentation.
7.10 Calculate the Brinell hardness value of flat test pieces using the formula given in Table 1, rounding the result to 3 significant figures. The Brinell hardness value can also be determined using the hardness value table given in GB/T 231.4.
8 Uncertainty of the results
8.1 A complete evaluation of the uncertainty may be done according to
Reference [1] and [2].
8.2 For hardness test, independent of the type of sources, there are two evaluation methods for the measurement of the uncertainty.
- One is based on the evaluation of all relevant uncertainty components appearing during a direct calibration[3].
- One is based on indirect calibration using a hardness reference block (certified reference material), the evaluation method is given in Annex C[3],[4],[5],[6].
8.3 It may not always be possible to quantify the contributions of all the identified components to the uncertainty. In this case, an estimate of type A standard uncertainty can be obtained from the statistical analysis of repeated tests on the test piece. Care shall be taken, if standard uncertainties of type A and B are summarized, that the contributions of each component are not
counted twice[2].
9 Test report
Unless otherwise specified, at least the following information shall be included in the test report.
a) a reference to this Part of GB/T 231;
b) the detailed description of the test piece;
c) the date of the test;
d) the test temperature if it is not within the limits 10 ??C to 35 ??C;
e) the ratio of indentation diameter to indenter diameter, if it falls outside the limits of 0.24 to 0.60;
f) the test result reported in accordance with the designation specified in 4.2; g) where conversion to another hardness scale is performed, the basis of this conversion shall be specified;
NOTE. There is no general process of accurately converting Brinell hardness into other scales of hardness or into tensile strength.
h) additional requirements outside the scope of this Part;
i) details of any occurrence which may have affected the test result.
Annex C
(informative)
Uncertainty of the measurement of hardness values
C.1 General requirements
The uncertainty defined in this annex considers only those uncertainties associated with the measurement of the hardness tester with respect to the hardness reference blocks. These uncertainties reflect the combined effect of all the separate uncertainties (indirect verification). Because this approach requires each individual component of the hardness tester to operate
normally within its allowable tolerance range, it is strongly recommended that this approach be applied for a maximum of one year after the hardness tester successful passing a direct calibration.
Figure C.1 shows the four-level structure of the metrological chain necessary to define and disseminate hardness scales. The chain starts at the
international level, using international definitions of the various hardness scales to carry out international inter-comparison. A number of primary standard hardness testers at the national level "produce" primary hardness reference blocks for the calibration laboratory level. Naturally, direct verification and calibration of these primary standard hardness tester shall be at the highest possible accuracy.
item shall be higher or lower than a certain value, this shall be interpreted as simply specifying that the measured and calculated value(s) shall meet this requirement, unless specifically stated otherwise in the product standard. C.2 General procedure
This procedure calculates an expanded uncertainty by establishing a link to the measured hardness value. Two different calculation methods are given in Tables C.1 and C.2 together with details of the symbols used. In both cases, a number of uncorrelated standard uncertainty sources are combined by the Root-Sum-Square (RSS) method, and then multiplied by the coverage factor, k (k = 2).
NOTE. This uncertainty estimation makes no allowance for any possible drift in the hardness tester performance subsequent to its last calibration, as it assumes that any such changes will be insignificant in magnitude. As such, most of this analysis could be performed immediately after the hardness tester?€?s calibration and the calibration results included in the hardness tester?€?s calibration certificate.
C.3 Bias of the hardness tester
The bias, b, of a hardness tester (also termed ?€?error?€?) is derived, during an indirect verification, from the difference between.
- the certified calibration value of the hardness reference block used, and - the mean hardness value of the five indentations made in this block
during verification of the machine,
and can be implemented in different ways into the determination of
uncertainty.
C.4 Procedures for calculating uncertainty. Hardness measurement
values
NOTE. CRM (Certified Reference Material) refers to the hardness reference block calibrated by the standard hardness tester. In hardness testing standards, certified reference material is equivalent to the hardness reference block, i.e. a piece of hardness block with a certified hardness value and associated uncertainty.
C.4.1 Method without consideration of bias (method M1)
Method M1 is a simplified method without considering any systematic error of the hardness tester.
In method M1, the error limit (the maximum allowable bias of the hardness tester?€?s reading from the hardness reference block?€?s calibrated value) is used

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