GB/T 229-2020Metallic Materials — Charpy Pendulum Impact Test Method

Foreword

This standard was drafted in accordance with the rules given in GB/T 1.1-2009.

This standard replaces GB/T 229-2007 "Metallic materials - Charpy pendulum impact test method". Compared with GB/T 229-2007, the main technical changes are as follows:

- In the scope, ADD the unnotched specimens; MAKE requirements for the terms and definitions, symbols and descriptions, dimensional deviations, specimen installation of unnotched specimens (see Chapter 1, 3.2.1, Table 1, Table 2, 8.1, Appendix A);

- ADD the symbol B of specimen thickness; ADD the symbol α of the angle when the pendulum is released; ADD the description of the elevation angle β1 and β2; ADD the symbol KN of the nominal value of the initial potential energy; ADD the symbol M of the moment; ADD the energy loss symbol p caused by pointer friction, the energy loss symbol p' caused by bearing friction and air resistance, the correction symbol pβ for the energy loss caused by the elevation angle β; MODIFY the symbol of shear section rate, which is changed to SFA; ADD the transition temperature symbol Tt27 corresponding to the specified absorption energy value of 27J, the transition temperature symbol Tt50%US corresponding to 50% of the energy absorbed on the upper platform, the transition temperature symbol Tt50%SFA corresponding to the shear section rate of 50%, the transition temperature symbol Tt0.9 corresponding to lateral expansion value 0.9 mm (see Table 1; Table 1 of the 2007 edition);

- SUPPLEMENT and IMPROVE the principle of impact test (see Chapter 5;

Chapter 5 of the 2007 edition);

- ADD the determination of friction loss (see 8.2);

- MODIFY the test temperature requirements (see 8.3.3; 8.2.3 of the 2007 edition);

- ADD the necessary and optional content of the test report [see 9.1 g), 9.2 j), k)];

- ADD the Informative Appendix E "Measuring uncertainty of absorbed energy value K" (see Appendix E);

temperature compensation value (see Appendix E of the 2007 edition).

This standard uses the redrafting method to amend and adopt ISO 148-1:2016 "Metallic materials - Charpy pendulum impact test - Part 1: Test method".

Compared with ISO 148-1:2016, this standard has structural differences, adding clause 8.9 test results.

Compared with ISO 148-1:2016, this standard has technical differences. The terms involved in these differences have been marked by a vertical single line (|) on the outer margins.

The technical differences between this standard and ISO 148-1:2016 and the reasons are as follows:

- In the scope of Chapter 1, ADD the unnotched specimens to suit China's national conditions;

- Regarding normative references, this standard has adjusted the technical differences to adapt to Chinese technical conditions. The adjustments are reflected in Chapter 2 "Normative references". The specific adjustments are as follows:

● USE GB/T 3808 which adopts the international standard through modification to replace ISO 148-2 (see 7.2, E.2.1.2);

- In Table 1, ADD the symbols KT and descriptions that were missed in the ISO standard; ADD the symbols and descriptions of the unnotched specimens correspondingly due to the addition of unnotched specimen in the Scope; CLARIFY the units of β1 and β2 as "°" and the unit of K1, K2, KN as "J", to avoid unit confusion;

- MODIFY the last two paragraphs of the principle of Chapter 5 to be a note, because this part of the content is a further explanation of the principle;

- In 6.1.2, ADD the "specimens of other thicknesses can also be used through agreement", to expand the scope of application of this standard;

- In 6.4, ADD that "the cutting of specimen blanks shall be carried out in accordance with the relevant product standards or the provisions of GB/T2975" for the convenience of actual operation;

- In Table 2, ADD the size and tolerance of U-notch specimens which have a ligament width of 8 mm; ADD the notes for unnotched specimens; ADJUST the angle tolerance between adjacent longitudinal surfaces of the specimen; DELETE the tolerance grades of the two notches, to meet China's national conditions;

- For the convenience of application, ADD the symbols KW2 and KW8 used for the pendulum hammer blade of the unnotched specimen in 7.3;

- In order to facilitate the operation of the application of unnotched specimens, ADD the requirements for the installation position of unnotched specimens and the pretest inspection requirements in 8.1;

- ADD the detailed requirements for bearing friction and windage loss in 8.2.2, to facilitate the implementation of the standard;

- In 8.5, ADD the lower limit of use of the testing machine and the requirements for resolution; ADD note 2 to explain it, to improve the operability of the standard and facilitate the implementation of the standard;

- In order to increase the operability, ADD the description in 8.6 when the pendulum does not break the specimen due to insufficient impact energy of the testing machine and the measured absorbed energy exceeds the energy range of the testing machine;

- In 8.9, ADD the energy-absorption rounding-off requirements to improve the standard operability;

- In 9.1, ADD the item c) notch type and ligament width (notch depth); in item d), thickness of 5 mm and 3 mm" due to data errors; ADD the requirements for clamps for unnotched specimens; ADD the requirements for clamps for Unotches, to improve the standard operability, to facilitate the implementation of standards.

This standard has made the following editorial changes:

- In the note of 3.1.2, ADD the expression that "use the letter W to represent unnotched specimens".

This standard was proposed by the China Iron and Steel Association.

This standard shall be under the jurisdiction of the National Steel Standardization Technical Committee (SAC/TC 183).

Drafting organizations of this standard: Central Iron and Steel Research Institute, Metallurgical Industry Information Standards Institute, Shanxi Taigang Stainless Steel Co., Ltd., Shanghai Shenli Testing Machine Co., Ltd., Shenzhen Wance Testing Equipment Co., Ltd., Nanjing Iron and Steel Co., Ltd., National Iron and Steel Co., Ltd. Product Quality Supervision and Inspection Center, Pabo Testing Technology Service Co., Ltd., Lixi (Shanghai) Scientific Instrument Co., Ltd., Qiqihar Huagong Machine Tool Co., Ltd., Minmetals Yingkou Medium Plate Co., Ltd., Shougang Group Co., Ltd., Chengdu Iron and Steel Research Institute Testing and Certification Co., Ltd., Dalian Hope Physical and Chemical Testing Technology Co., Ltd., Shanghai Institute of Materials.

The main drafters of this standard: Liu Tao, Gao Yifei, Dong Li, Wang Liying, Huang Xing, Li Jianfeng, Zhang Huawei, Zhang Xiaoli, Xu Liang, Wang Bin, Wang Hongliang, Zhong Yangyang, Qiu Yu, Yin Jianjun, Jia Yuanwei, Zhou Lifu, Wang Bin, Liang Caimeng, Zhang Qingshui, Hou Huining.

1 Scope

This standard specifies the Charpy pendulum impact test method for measuring the energy absorbed by impact specimens (V-shaped, U-shaped notch, unnotched specimens) in the impact test of metallic materials.

This standard applies to the Charpy pendulum impact test under room temperature, high temperature or low temperature conditions, but does not include the instrumental impact test method, the content of this part is as shown in GB/T 19748.

2 Normative references

The following documents are essential to the application of this document. For the dated documents, only the versions with the dates indicated are applicable to this document; for the undated documents, only the latest version (including all the amendments) is applicable to this standard.

3 Terms and definitions

The following terms and definitions apply to this document.

3.1 Energy-related definitions 3.1.1

The potential energy of the pendulum before the impact test of the drop pendulum, which is determined by direct calibration.

The energy required by the pendulum impact testing machine to break the specimen, which is the value after friction correction.

Note: Use the letter V or U to represent the notch geometry, the letter W to represent the unnotched specimen, the subscript number 2 or 8 to represent the radius of the pendulum hammer blade, such as KV2.

The nominal energy value as given by the manufacturer of impact testing machine.

3.2 Definitions related to specimens 3.2.1

The distance between the notch surface and its opposite surface. Note 1: For unnotched specimens, it is the distance between the surface of the striking center and the opposite surface. Note 3: In GB/T 229-2007, the distance between the notched surface and its opposite surface is defined as "height", which is replaced by "width", in order to be consistent with other fracture standards with the same principle. The dimension perpendicular to the width direction and parallel to the notch axis. Note 1: For unnotched specimens, the minimum dimension perpendicular to the width direction. […]

4 Symbols and description

The symbols and descriptions used in this document are as shown in Table 1. […]

5 Test principle

The test specified in this standard uses a single impact of a pendulum to break the specimen. The test conditions are given in Chapter 6, Chapter 7, Chapter 8. The notch of the specimen has a prescribed geometric shape and is located in the center of the two supports, opposite to the striking center. The measurement parameters include absorbed energy, lateral expansion value and shear section rate. Since the impact results of many materials will vary with temperature, the test shall be carried out at a given temperature. When the given temperature is not room temperature, the specimen shall be heated or cooled at a controlled temperature.

Note 1: The Charpy pendulum impact test is a commonly used acceptance test in industrial applications. For this type of test, the specimen is completely broken, partially broken or just plastically deformed and scratched through the anvil. These conditions are not important. In terms of theoretical research, the measured energy value needs to be studied in depth; the measured energy value may have a lot to do with whether the specimen is broken.

Note 2: It shall be noted that not all Charpy impact test results can be directly compared. For example, the pendulum blade's radius used in the test may be different, or specimens of different shapes may be used. The use of different pendulum blades may lead to differences in test results [2]. This is also the reason why the complete test report, in addition to the implementation of the standard, needs to include clear testing machine type, specimen type, specimen fracture after the test, etc. to determine the comparison items of test results.

6 Specimen

6.1 General requirements

6.1.1 The length of the standard size impact specimen is 55 mm; the cross section is a square cross-section of 10 mm × 10 mm. There is a V-shaped or U-shaped notch in the middle of the specimen length, see 6.2.1 and 6.2.2.

6.1.2 If the specimen is not enough to prepare standard size specimens, if there are no special requirements, small size specimens with a thickness of 7.5 mm, 5 mm or 2.5 mm can be used (see Figure 2 and Table 2); specimens of other thicknesses can also be used by agreement.

Note 1: The results can be directly compared only if the specimens of the same shape and size are used.

Note 2: For low-energy impact tests, it is very important to use gaskets to place smallsized specimens in the center of the pendulum to avoid additional energy absorption. The importance of using gaskets for high-energy impact tests will be reduced. The gasket can be placed above or below the support, so that the center of the specimen thickness is 5 mm above the 10 mm support (that is, the center of the standard specimen).

6.1.3 For test materials that require heat treatment, finishing and notching shall be performed on the specimen after the final heat treatment, unless it can be proven that processing the specimen before the heat treatment will not affect the test results.

6.2 Notch geometry

6.2.1 The notch of the specimen shall be carefully prepared, to ensure that the root radius of the notch has no processing traces that affect energy absorption. The plane of symmetry of the notch shall be perpendicular to the longitudinal axis of the specimen (see Figure 2). 6.2. […]

7 Test equipment

7.1 General requirements

All measuring instruments shall be traceable to national or international standards. The measuring instrument shall be calibrated within a suitable period.

7.3 Pendulum blade

The radius of curvature of the edge of the pendulum blade shall be either 2 mm or 8 mm. Use the subscript number of the symbol to indicate: KV2, KV8, KU2, KU8, KW2, KW8. The choice of pendulum blade's radius shall be based on the relevant product standards.

Note: The test results obtained by using 2 mm and 8 mm pendulum blades may be different.

8 Test procedure

8.1 General requirements

8.1.1 The specimen shall be close to the anvil of the testing machine; the distance between the symmetry plane of the specimen notch and the middle plane of the two anvils shall be no more than 0.5 mm. The strike center of the pendulum blade is located on the symmetry plane of the notch and the opposite side of the specimen notch (see Figure 1). […]