GB/T 230.2-2022 English PDF (GBT230.2-2022)
GB/T 230.2-2022 English PDF (GBT230.2-2022)
GB/T 230.2-2022: Metallic materials - Rockwell hardness test - Part 2: Verification and calibration of testing machines and indenters
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 19.060; 77.040.10
CCS N 71
Replacing GB/T 230.2-2012
Metallic materials - Rockwell hardness test - Part 2:
Verification and calibration of testing machines and
(ISO 6508-2:2015, MOD)
ISSUED ON: JULY 11, 2022
IMPLEMENTED ON: FEBRUARY 01, 2023
Issued by: State Administration for Market Regulation;
Standardization Administration of PRC.
Table of Contents
Foreword ... 3
Introduction ... 6
1 Scope ... 7
2 Normative references ... 7
3 Terms and definitions ... 8
4 General requirements ... 8
5 Direct inspection by durometer ... 8
5.1 General... 8
5.2 Calibration and inspection of test force ... 9
5.3 Calibration and inspection of indentation depth measuring device ... 9 5.4 Calibration and inspection of test cycle time ... 10
5.5 Calibration and inspection of durometer hysteresis ... 11
6 Indirect inspection of durometer ... 11
6.1 General... 11
6.2 Procedure ... 12
6.3 Repeatability ... 13
6.4 Indication error ... 15
6.5 Measurement uncertainty ... 15
7 Calibration and inspection of Rockwell hardness indenter ... 15
7.1 General... 15
7.2 Diamond cone indenter ... 15
7.3 Ball indenter ... 19
7.4 Identification ... 20
8 Period of direct and indirect inspection ... 21
9 Inspection report ... 21
Appendix A (Normative) Repeatability of durometer ... 23
Appendix B (Informative) Measurement uncertainty of durometer calibration results ... 25
Metallic materials - Rockwell hardness test - Part 2:
Verification and calibration of testing machines and
This document specifies two inspection methods (direct inspection and indirect inspection) of the Rockwell durometer, for determining the Rockwell hardness, according to GB/T 230.1; specifies the inspection method of the Rockwell hardness indenter.
The direct test method is suitable for checking whether the main parameters related to the function of the durometer are within the specified tolerances, such as test force, depth measurement, test cycle time. The indirect test method is suitable for using a set of calibrated reference blocks, to determine the performance of the durometer, when measuring materials with known hardness.
The indirect test method can be used alone for regular routine inspections, using medium durometers.
If the durometer can also be used for the hardness test of other hardness test methods, the durometer shall be tested separately, according to each method.
This document applies to both stationary durometers and portable durometers. Note that tungsten carbide alloy ball indenters have been considered as Rockwell hardness standard ball indenters. The steel ball indenter is limited to use, under the conditions of Appendix A in GB/T 230.1-2018.
2 Normative references
The contents of the following documents constitute the essential provisions of this document through normative references in the text. Among them, for dated references, only the version corresponding to the date applies to this document; for undated references, the latest version (including all amendments) applies to this document. GB/T 230.1-2018 Metallic materials - Rockwell hardness test - Part 1: Test method (ISO 6508-1:2016, MOD)
GB/T 230.3-2022 Metallic materials - Rockwell hardness test - Part 3: Calibration 5.2 Calibration and inspection of test force
5.2.1 Measurements shall be made, for each initial test force F0 (see 5.2.4) and each total test force F (see 5.2.5) used. As far as practicable, in the entire movement range of the spindle during the test, the above-mentioned force measurements are made at least three positions, at certain intervals. The initial test force shall be maintained for at least 2 s.
5.2.2 At each position of the spindle, three readings shall be taken at each test force. Before each measurement reading, the direction of movement of the spindle shall be consistent with the direction of movement during the test.
5.2.3 The test force shall be measured, by one of the following two methods: - Use a standard force measuring instrument, at grade 1 or better than grade 1, that meets the requirements of GB/T 13634, AND whose return performance has been calibrated;
- Apply a force within ± 0.2% of indication error, by means of weight of calibrated mass or other means of equivalent accuracy, so that this force is in balance with the test force to be detected.
Evidence should be provided to prove that the output of the force-measuring device does not change by more than 0.2%, during the period of 1 s ~ 30 s, after the step change of the test force.
5.2.4 Before the main test force F1 is applied and after it is removed, the maximum tolerance for each measurement of the initial test force F0 shall be ±2.0% of its nominal value, see formula (B.2). The variation range (maximum value minus minimum value) of all measured values of initial test force shall not be greater than 1.5% of the nominal value of F0.
5.2.5 The maximum tolerance for each measurement of the total test force F shall be ±1.0% of its nominal value. The variation range (maximum value minus minimum value) of all measured values of the total test force shall not be greater than 0.75% of the nominal value of F.
5.3 Calibration and inspection of indentation depth measuring device
5.3.1 The indentation depth measuring device shall be calibrated, by making the indenter or indenter seat produce known displacement increments.
5.3.2 When calculated at a 95% confidence level, the expanded uncertainty of the instrument or gauge block, which is used to test the indentation depth measuring device, shall not exceed 0.0003 mm.
5.3.3 The indentation depth measuring device shall be tested, at least 4 positions evenly distributed within the entire working depth range of the durometer, during normal measurement. For conventional Rockwell hardness scales (A, C, D, B, E, F, G, H, K), the working depth is 0.25 mm; for superficial Rockwell hardness scales (N, T), the working depth is 0.1 mm.
5.3.4 The indentation depth measuring device of some durometers has a large stroke; the position of the working range of the measuring device will change with the thickness of the specimen. This type of durometer shall be able to be checked electronically, to ensure continuous operation of the indentation depth measuring device, throughout the entire travel range. This durometer shall be inspected according to the following steps: a) Select the three positions of the highest point, the center point, the lowest point of the total range of the measuring device. Near each of the three positions, use not less than four displacement increments, at equal intervals of about 0.05 mm, to test the indentation depth measuring device;
b) Operate the drive and monitor whether the measurement of the displacement is continuous, over the entire travel range of the drive. The displacement indication shall be displayed continuously, throughout the entire travel range.
5.3.5 For scales A to K, the indication value of the indentation depth measuring device shall be accurate to ±0.001 mm, within the measurement range of each scale. For scales N and T, it shall be accurate to ±0.0005 mm, within the measurement range of each scale, that is, no more than ±0.5 Rockwell hardness units.
5.4 Calibration and inspection of test cycle time
5.4.1 The test cycle time shall be verified by the manufacturer of the durometer, during production or after maintenance that may affect the test cycle time. At other times, the complete test cycle time is not required as part of the direct inspection, see Table 10. 5.4.2 The test cycle time shall comply with the provisions of GB/T 230.1-2018. 5.4.3 For durometers, that automatically control the test cycle time, the measurement expanded uncertainty (k = 2) of the timing instrument, which is used to check the test cycle time, shall not exceed 0.2 s. It is recommended that the measured value of the test cycle time, plus or minus the expanded uncertainty of measurement (k = 2) of the calibration instrument, does not exceed the time limit specified in GB/T 230.1-2018. 5.4.4 For durometers that require the operator to manually control the test cycle time, it shall be checked whether the durometer can achieve the specified test cycle time. 18.104.22.168 The diamond conical surface and top spherical surface, which are corresponding to the indentation depth range of 0.3 mm, shall be polished; the combination of the two surfaces shall be smooth and tangent. Both faces shall be free from surface defects. 22.214.171.124 The shape of the indenter can be checked, by direct measurement or optical measurement. The detection shall be carried out on at least 4 equally spaced different axial sections (e.g., 0°, 45°, 90°, 135°) of the axis of the indenter. It is also possible to use a collimator for measurement, in which case it should measure at least 4 central angles; it shall include a central angle of 120°.
The position, where the top spherical surface of the diamond indenter combines with the cone, will change due to the difference in the radius of the top spherical surface and the angle of the cone. Theoretically, the junction point of a perfect indenter geometry, which is measured along a perpendicular line to the indenter axis, shall be located at a position 100 μm away from the indenter axis. In order to avoid including the combined area of the two in the measurement of the top spherical radius and the cone angle, the 80 μm ~ 120 μm part of the diamond surface can be ignored.
126.96.36.199 When calculated according to the 95% confidence level, the expanded uncertainty of the instrument, which is used to test the geometry of the diamond indenter, shall not be greater than:
- Angle: 0.1°;
- Radius: 0.005 mm.
188.8.131.52 The apex angle of the diamond cone shall be (120 ± 0.35)°.
184.108.40.206 The top of the indenter shall be a spherical surface; its average spherical radius is determined, based on the measurement values measured in at least 4 axial sections, according to the provisions of 220.127.116.11. Each measurement shall be within (0.2 ± 0.015) mm. The average value shall be within (0.2 ± 0.01) mm. The local deviation of the actual radius shall not exceed 0.002 mm.
7.2.3 Indirect inspection of diamond indenters
18.104.22.168 The hardness value, which is measured by the durometer, depends not only on the spherical radius and cone angle, at the top of the indenter, but also on its surface roughness, the position of the crystal axis of the diamond and the setting of the diamond in the indenter body. In order to test the above effects, the performance of the tested diamond indenter shall be tested indirectly. The indirect inspection shall be done, by performing a set of comparison tests on the reference block, which meets the requirements of GB/T 230.3-2022 and the standard diamond indenter, which meets the requirements of 5.3 of GB/T 230.3-2022.
The indirect inspection shall be carried out using a standard hardness machine, that meets the requirements of Chapter 5 of GB/T 230.3-2022; the inspection procedure Appendix B
Measurement uncertainty of durometer calibration results
Measurement uncertainty analysis is a powerful tool for identifying sources of error and understanding differences in measurement results. This Appendix gives guidance on the assessment of uncertainty. If the customer has no special requirements, this method can be used as a reference. The guidelines, which are presented in this document, for the performance of durometers have been developed and refined over a considerable period of time. When the determination of the durometer needs to meet a specified tolerance, the tolerance already includes the uncertainty related to the measuring instrument and (or) reference standard used. Therefore, any further adjustments to the uncertainty (such as reduction of tolerances by measurement uncertainty) are not appropriate. This applies to all measurements, which are made on the durometer, either directly or indirectly. In various cases, these values may be simple measurements, which are taken by specified measuring instruments and/or reference standards used, when assessing compliance of a durometer with the provisions of this document. However, in some special cases, it is also permissible to reduce the tolerance by measurement uncertainty. This situation only applies where the relevant parties reach an agreement by consensus.
B.2 Direct inspection - Uncertainty of measurement of test parts of a durometer B.2.1 Uncertainty of test force calibration
Measure the test force directly. Calculate and report the difference -- BETWEEN the measured value of each force applied by the durometer AND the corresponding standard force value indicated by the standard force gauge. A direct inspection checks that each value is within the specified limits of the maximum allowable error. Therefore, a method of measuring uncertainty using the calculated value of the true value of the test force, which is specified in the relevant test method, is given below. The relative composite standard uncertainty of test force calibration is calculated according to the formula (B.1):
uFRS - The relative standard uncertainty, which is introduced by the standard force gauge (given in the calibration certificate);
B.3 Indirect inspection - Uncertainty in durometer calibration
B.3.1 Uncertainty of durometer error
Note: In this Appendix, according to the definition of the hardness test standard, the subscript "CRM (Certified Reference Material)" means "reference block".
The overall functionality of the durometer can be checked by indirect inspection using certified reference materials. The repeatability of the indication value of the durometer and the difference between the hardness measurement value of the durometer and its true value, that is, the indication value error, can be determined through indirect inspection. For the indirect inspection of the durometer, the difference or error b -- between the average hardness value as measured by the durometer on the certified reference material and the calibration value of the certified reference material -- shall be calculated and reported. The indirect inspection is to check whether the indication error of the durometer is within the limit of the maximum allowable error. A method for calculating the uncertainty of the indication error of the hardness measurement value of the certified standard material, as relative to the true value of the average hardness of the certified standard material by the durometer, is given below. This method is based on the results of indirect inspection; it is suitable for the calibration of durometers in Rockwell hardness units, using certified reference materials.
The measurement uncertainty of the indication error of the durometer, which is obtained through the indirect inspection, is calculated according to the formula (B.13): Where:
uCRM - The measurement uncertainty component, which is introduced by the calibration uncertainty of the calibration value given by the calibration certificate of the certified reference material (k = 1);
uHCRM - The measurement uncertainty component, which is introduced by the poor measurement repeatability of the durometer and the hardness inhomogeneity of the certified reference material, calculated based on the standard deviation of the hardness measurement value of the certified reference material;
ums - Component of measurement uncertainty, which is introduced by durometer resolution.
The following example illustrates the uncertainty assessment process of the indirect inspection of Rockwell hardness C scale (about 45 HRC).
Reference block (certified reference material): HCRM = 45.4 HRC