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This document is developed in accordance with the rules given in GB/T 1.1-2020 Directives for standardization — Part 1: Rules for the structure and drafting of standardizing documents.
This document is part 2 of GB/T 231 Metallic materials — Brinell hardness test. The following parts of GB/T 231 have been published:
——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 document replaces GB/T 231.2-2012 Metallic materials — Brinell hardness test — Part 2: Verification and calibration of testing machines. The following main technical changes have been made with respect to GB/T 231.2-2012:
——The hardness ranges of low, medium and high reference blocks for the testing machine used for indirect verification and the maximum permissible values of relative repeatability and relative error of the indications corresponding to different hardness ranges of the testing machine have been modified according to the force-diameter indices (see 6.7 and 6.9; 5.7 and 5.8 of 2012 edition);
——The Annex B "Verification of hardness testing machines that are incapable of meeting the specified force/time profile" has been added (see Annex B).
This document is modified in relation to ISO 6506-2: 2017 Metallic materials — Brinell hardness test — Part 2: Verification and calibration of testing machines.
The following structural changes have been made with respect to ISO 6506-2: 2017:
——The 5.3.4.1 and 5.3.4.2 in ISO 6506-2: 2017 have been modified to 5.3.5 and 5.3.6.
——Technical differences between this document and ISO 6506-2: 2017 are marked with perpendicular single line (|) in the outside page margin of the provisions concerned. The technical differences and their reasons are as follows:
——ISO 6506-1 is replaced by GB/T 231.1 (see Clause 1, 5.2.4, 5.5.2, 6.4, A.1 and Annex B) so as to adapt to the technical conditions of China;
——ISO 6506-3 is replaced by GB/T 231.3 modified in relation to the international standard (see Clause 1, 5.4.3 and 6.1) so as to adapt to the technical conditions of China;
——GB/T 36416.1-2018 are added for reference (see Clause 3)
——ISO 6507-1 is replaced by GB/T 4340.1 modified in relation to the international standard (see 5.3.4.2) so as to adapt to the technical conditions of China;
The following editorial changes have been made in this document:
——The serial numbers "1", "2" and "3" representing different hardness ranges of testing machine" in the first column of Table 2 and Table 3 (see 6.7) have been modified to the Chinese characters "low", "medium" and "high" respectively;
——The symbol "×" indicating items required to be inspected in Table 4 has been modified to the symbol "√", and the symbol "—" has been added to indicate items not required to be inspected (see Clause 7);
——The unnumbered equations in Annex A of ISO 6506-2: 2017 have been uniformly numbered in sequence (see Annex A);
——The symbol "ˉb" in Equations (A.6), (A.8) and Table A.9 in Annex A of ISO 6506-2: 2017 has been modified to the symbol "E" [see Equations (A.10), (A.13) and Table A.9].
Attention is drawn to the possibility that some of the parts of this document may be the subject of patent rights. The issuing body of this document shall not be held responsible for identifying any or all such patent rights.
This document was proposed by China Machinery Industry Federation.
This document is under the jurisdiction of the National Technical Committee on Testing Machines of Standardization Administration of China (SAC/TC 122)
The previous editions of this document are as follows:
——This document was firstly issued as GB 6269-1986 Brinell hardness testing machines — Technical conditions in 1986, and was first revised as GB/T 6269-1997 in 1997;
——It was secondly revised as GB/T 231.2-2002 in 2002, and thirdly revised in 2012;
——This is the fourth revision.?
Introduction
GB/T 231 Metallic materials — Brinell hardness test, which consists of four parts, aims to standardize the test methods of Brinell hardness, the inspection of test instruments and the calculation tables of Brinell hardness values.
——Part 1: Test method, designed to establish the procedure and method to be followed in Brinell hardness test.
——Part 2: Verification and calibration of testing machines, designed to determine the technical requirements and verification and calibration methods of Brinell hardness testing machine.
——Part 3: Calibration of reference blocks, designed to determine the technical requirements and calibration methods of Brinell reference blocks.
——Part 4: Tables of hardness values, designed to provide the calculated value of Brinell hardness.
Metallic materials — Brinell hardness test —
Part 2: Verification and calibration of testing machines
1 Scope
This document specifies methods of direct and indirect verification of Brinell hardness testing machines used for determining Brinell hardness (hereinafter referred to as "testing machines") in accordance with GB/T 231.1 and also specifies when both types of verification have to be performed.
The direct verification involves checking that verified testing machine performance parameters fall within specified limits whereas the indirect verification utilizes hardness measurements of reference blocks, calibrated in accordance with GB/T 231.3, to check the testing machine's overall performance.
If a testing machine is also to be used for other methods of hardness testing, it has to be verified independently for each method.
This document is applicable to both fixed and portable testing machines. For testing machines that are incapable of satisfying the specified force-time profile, the direct verification of force and testing cycle may be modified by the use of Annex B.
2 Normative references
The following documents contain provisions which, through reference in this text, constitute indispensable provisions of this document. For dated references, only the edition cited applies. For undated references, the latest edition (including any amendments) applies.
GB/T 231.1 Metallic materials — Brinell hardness test — Part 1: Test method (GB/T 231.1-2018, ISO 6506-1: 2014, MOD)
GB/T 231.3 Metallic materials — Brinell hardness test — Part 3: Calibration of reference blocks (GB/T 231.3-2022, ISO 6506-3: 2014, MOD)
GB/T 4340.1 Metallic materials — Vickers hardness test — Part 1: Test method (GB/T 4340.1-2009, ISO 6507-1: 2005, MOD)
GB/T 13634 Calibration of force proving instruments used for the verification of uniaxial testing machines (GB/T 13634-2019, ISO 376: 2011, IDT)
GB/T 36416.1 Testing machine vocabulary — Part 1: Material testing machines
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3 Terms and definitions
For the purpose of this document, the terms and definitions specified in GB/T 36416.1 apply.
4 General
A testing machine, prior to verification, shall be checked to ensure that it is properly set up in accordance with the manufacturer's instructions.
Especially, it should be checked that:
a) The mount holding the ball-holder slides correctly in its guide;
b) Every ball-holder with a ball used during the calibration is firmly held in the mount;
c) The test force is applied and removed without shock, vibration, or overrun and in such a manner that the readings are not influenced;
d) If the indentation diameter measuring device is integrated into the machine:
1) The change from removing the test force to measuring indentation mode does not influence the diameter measurements;
2) The illumination does not affect the diameter measurements;
3) The centre of the indentation is in the centre of the field of view, if necessary.
5 Direct verification
5.1 General
5.1.1 Direct verification shall be carried out at a temperature of (23 ± 5)°C. If the verification is made outside this temperature range, this shall be reported in the verification report.
5.1.2 The instruments used for verification shall be traceable to the national standards.
5.1.3 Direct verification involves:
a) measurement of the test forces;
b) measurement of the diameter, hardness, and density of the indenter ball;
c) calibration of the indentation diameter measuring device;
d) measurement of the testing cycle.
For each of the above items, direct verification also includes assessment of the results against the specified tolerances.
5.2 Measurement of the test forces
5.2.1 Each test force shall be measured within the working range of the testing machine. If the force is applied in open-loop mode by a lever or other device employing a mechanical advantage, each force shall be measured at no fewer than three positions of the indenter uniformly spaced throughout its range of movement during testing.
5.2.2 Three measurements shall be made for each test force at each position of the indenter. Immediately before each measurement is taken, the indenter shall be moved in the same direction as during testing.
5.2.3 The test force shall be measured by one of the following two methods:
——By means of a force-proving instrument in accordance with GB/T 13634 Class 1 or better;
——By balancing against a force, accurate to ±0.2%, applied by means of calibrated masses or another method with the same accuracy.
5.2.4 The error of each measurement of a force shall be within ±1.0% of the nominal test force [see Equation (A.2) in Annex A], as defined in GB/T 231.1.
5.3 Measurement of the properties of the indenter ball
5.3.1 The indenter consists of a ball and an indenter holder. The verification applies only to the ball.
5.3.2 For the purpose of verifying the size and the hardness of the balls, a minimum of two balls, selected at random from a batch, shall be tested. Each sample ball subject to verification shall be discarded.
5.3.3 The balls shall be polished and free from surface defects.
5.3.4 The user shall either measure the balls to ensure that they meet the requirements of 5.3.5 and 5.3.6 or shall obtain balls from a supplier certifying that the requirements of 5.3.5 and 5.3.6 are met.
5.3.5 The diameter of the ball shall be determined by taking the mean value of the individual measured value at not less than three positions on the ball. No single measured value shall differ from the nominal diameter by more than the tolerance given in Table 1.
Foreword i
Introduction iii
1 Scope
2 Normative references
3 Terms and definitions
4 General
5 Direct verification
5.1 General
5.2 Measurement of the test forces
5.3 Measurement of the properties of the indenter ball
5.4 Calibration of the indentation diameter measuring device
5.5 Verification of the testing cycle
6 Indirect verification
7 Intervals between verifications
8 Verification report/calibration certificate
Annex A (Informative) Uncertainty of measurement of the verification results of the hardness testing machine
Annex B (Normative) Verification of hardness testing machines that are incapable of meeting the specified force/time profile
Bibliography
