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This document is drafted 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 the Part 3 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 part replaces GB/T 231.3-2012 Metallic Materials — Brinell Hardness Test — Part 3: Calibration of Reference Blocks, and the following technical deviations have been made with respect to GB/T 231.3-2012 (the previous edition):
— the requirements for test force measurement are modified (see 5.4 hereof; 4.4 of Edition 2012);
— the requirements for indenter measurement are modified (see 5.5 hereof; 4.5 of Edition 2012);
— the requirements for indentation diameter measuring system are modified (see 5.6 hereof; 4.6 of Edition 2012);
— the requirements for the characteristic of the hard metal balls are deleted (see 4.8 of Edition 2012);
— the requirements for the maximum indenter approach velocity are modified (see Table 3 in Clause 6 hereof; Clause 5 of Edition 2012);
— the requirements for the identify of reference indentation are modified (see Clause 7);
— the requirements for uncertainty in the document are added [see 9.3, d)];
— the overview for measurement uncertainty analysis of the mean hardness value of reference blocks are added (see A.1).
This document has been redrafted and modified adoption of International Standard ISO 6506-3:2014 Metallic Materials — Brinell Hardness Test — Part 3: Calibration of Reference Blocks.
Technical deviations exist between this document and ISO 6506-3:2014 and clauses involving these deviations are indicated by perpendicular single line (|) at page margin. The specific technical deviations, together with their justifications, are given below:
— the provisions for the scope of this document are added (see Clause 1);
— ISO 6506-1 is replaced by GB/T 231.1 which has been redrafted and modified adoption of the international standard (see Clause 1, 5.7 and Clause 6);
— ISO 6506-2 is replaced by GB/T 231.2-XXXX, which has been redrafted and modified adoption of the international standard (see Clause 1, 5.1 and 5.5);
— the "notes" in 3.1 of ISO 6506-3:2014 is changed into the text (see 4.1);
— ISO 376 is replaced by JJG 144 to adapt the technical conditions of China (see 5.4).
Attention is drawn to the possibility that some of the elements 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 standard was proposed by the China Machinery Industry Federation.
This document is under the jurisdiction of the National Technical Committee 122 on Testing Machines of Standardization Administration of China (SAC/TC 122).
The previous editions of this document are as follows:
— The first edition was issued in 1986 as GB 6270-1986; the first edition was revised in 1997 as GB/T 6270-1997; the second revision was issued in 2002 as GB/T 231.3-2002; the third revision was issued in 2012;
— This is the fourth revised edition.
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Introduction
GB/T 231 specifies the test methods of Brinell hardness, inspection of test apparatus and Brinell hardness value calculation, and consists of the following parts, under the general title Metallic Materials — Brinell Hardness Test:
— Part 1: Test Method. This part specifies the procedures and methods to be followed in the Brinell hardness test.
— Part 2: Verification and Calibration of Testing Machines. This part specifies the technical requirements, test and calibration methods required by the Brinell hardness testing machines.
— Part 3: Calibration of Reference Blocks. This part specifies the technical requirements and methods for the calibration of reference blocks of Brinell hardness.
— Part 4: Tables of Hardness Values. This part specifies the calculation result of Brinell hardness.
Metallic Materials — Brinell Hardness Test — Part 3: Calibration of Reference Blocks
1 Scope
This document specifies a method for the calibration of reference blocks to be used in the indirect verification of Brinell hardness testing machines as described in GB/T 231.2 and to be used in regular inspection of Brinell hardness testing machines as described in GB/T 231.1. This document also specifies the procedures necessary to ensure metrological traceability of the Brinell hardness calibration machine (hereinafter referred to as "calibration machine").
This document is applicable to the calibration of Brinell hardness reference blocks (hereinafter referred to as "reference blocks").
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 231.1 Metallic Materials — Brinell Hardness Test — Part 1: Test Method (GB/T 231.1-2018, ISO 6506-1:2014, MOD)
GB/T 231.2-2022 Metallic Materials — Brinell Hardness Test — Part 2: Verification and Calibration of Testing Machines (ISO 6506-2:2017, MOD)
JJG 144 Verification Regulation of Standard Dynamometers
3 Terms and Definitions
No terms and definitions are listed in this document.
4 Manufacture of Reference Blocks
4.1 The block shall be specially manufactured for use as a reference block. Attention is drawn to the need to use a manufacturing process which will give the necessary homogeneity, stability of structure, and uniformity of surface hardness.
4.2 Each metal block to be calibrated shall be of a thickness:
— not less than 16 mm for 10 mm balls;
— not less than 12 mm for 5 mm balls;
— not less than 6 mm for smaller balls.
12 mm for 10 mm balls can be used only if the hardness of the reference block is greater than 150 HBW.
4.3 The reference blocks shall be free of magnetism. It is recommended that the manufacturer shall ensure that the blocks, if of steel, have been demagnetized at the end of the manufacturing process.
4.4 The flatness of the two surfaces and the parallelism of the reference block shall be in accordance with Table 1.
4.5 The test surface shall be free from scratches which interfere with the measurement of the indentations (see Table 1).
4.6 To verify that no material is subsequently removed from the reference block, the thickness at the time of calibration shall be marked on it to the nearest 0.1 mm, or an identifying mark shall be made on the test surface.
Table 1 Requirements for the reference blocks
Diameter of ball
mm Tolerance in flatness of the surfaces
mm Tolerance in parallelism
mm/50mm Permissible surface roughness, Raa
μm
Test surface Bottom surface
10 0.040 0.050 0.3 0.8
5 0.030 0.040 0.2 0.8
2.5 0.020 0.030 0.1 0.8
1.0 0.020 0.030 0.05 0.8
a Sampling length: l = 0.80 mm (see GB/T 3505).
5 Calibration Machine
5.1 In addition to fulfilling the general requirements specified in GB/T 231.2-2022, Clause 4, the calibration machine shall also meet the requirements given in 5.2 to 5.7.
5.2 The machine shall be verified directly in intervals not exceeding 12 months.
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, if this is not possible, at least the force versus time behaviour.
5.3 The instruments used for verification and calibration of the calibration machine shall be traceable to the national benchmarks.
Foreword II
Introduction IV
1 Scope
2 Normative References
3 Terms and Definitions
4 Manufacture of Reference Blocks
5 Calibration Machine
6 Calibration Procedure
7 Number of Indentations
8 Non-uniformity of Reference Block
9 Marking
10 Validity
Annex A (Informative) Uncertainty of the Mean Hardness Value of Reference Blocks
Bibliography
