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GB/T 228 consists of the following parts, under the general title Metallic Materials — Tensile Testing:
— Part 1: Method of Test at Room Temperature;
— Part 2: Method of Test at Elevated Temperature;
— Part 3: Method of Test at Low Temperature;
— Part 4: Method of Test in Liquid Helium.
This is Part 3 of GB/T 228.
This standard is drafted in accordance with the rules given in the GB/T 1.1-2009.
This part replaces GB/T 13239-2006 Metallic Materials — Tensile Testing at Low Temperature in whole. The following technical deviations have been made with respect to the GB/T 13239-2006 (the previous edition):
— modification of the standard name;
— modification and addition of the partial terms and symbols, such as change of the temperature symbol from “θi” to “T”; change of the specified temperature symbol from “θi” to “Ti”; addition of the term "soaking time ts"; change of "specified non-proportional elongation strength Rp" to " proof strength for plastic extension Rp" (see Clause 4; Clause 4 of GB/T 13239-2006);
— addition of the fixing of the extensometer (see Clause 10);
— addition of the testing rate based on strain rate control (Method A) (see Clause 10);
— modification of the rounding off for numerical values of test result (see Clause 12; Clause 10 of GB/T 13239-2006);
— addition of the example for cooling curves of steel depending on test piece dimensions and the specified test temperature in ethanol and liquid nitrogen (see Annex B)
This standard has been redrafted and modified adoption of International Standard ISO 6892-3:2015 Metallic Materials — Tensile Testing — Part 3: Method of Test at Low Temperature.
The technical deviations between this part and ISO 6892-3:2015, together with their justifications, are as follows:
— the adjustments of technical deviations are made for the normative references in this standard so as to adapt to the technical conditions in China. The adjustment is mainly reflected in Clause 2 Normative References with the specific adjustments as follows:
● IEC 6892-1:2009 is replaced by GB/T 228.1-2010, which is redrafted and modified adoption of the international standard (see each clause);
● ISO 7500-1 is replaced by GB/T 16825.1, which is identical with the international standard (see 9.1);
● ISO 9513 is replaced by GB/T 12160, which is redrafted and modified adoption of the international standard (see 9.2);
— modification of the errors in the international standard: change of ">" to "≥", and change of "≤" to "<” in the column a0 of Table A.1; change of ">" to "≥" in Table A.2 (see Annex A).
— change of the nominal diameter of thread: change of M6 to M8, M8 to M10, M10 to M12, and M12 to M14 in Table A.3 (see Annex A). The nominal diameter of thread specified in the international standard is small, and the sample is easy to break in the thread during the test. Therefore, it is suggested to increase the nominal diameter of thread according to the test experience.
For the purposes of this part, the following editorial changes have also been made:
— addition of the “total proof strength properties (Rt) (if required)” in the title of 10.4.2.3 (see 10.4.2.3);
— change of the provisions of rounding off for numerical values specified in Item j) of Clause 12 of the international standard as a clause (see Clause 12), and the serial number of the subsequent clauses extended accordingly;
— addition of the reference of Annex L (Informative) of GB/T 228.1 (see Clause 14);
— addition of the Annex L in the list of annexes of GB/T 228.1 applicable to this part (see Clause 16);
— change of the symbol "×" in Table C.1 in Annex C to "√" (see Annex C).
This part was proposed by China Iron and Steel Industry Association.
This part is under the jurisdiction of SAC/TC 183 (National Technical Committee on Iron and Steel of Standardization Administration of China).
The previous editions of the standard replaced by this part are as follows:
— GB/T 13239-1991, GB/T 13239-2006.
Introduction
This part of GB/T 228 provides two methods for control of testing speeds. Method A is based on strain rates (including crosshead separation rate) with narrow tolerances (±20%). Method B is based on conventional strain rate ranges and tolerances. Method A is intended to minimize the variation of the test rates during the moment when strain rate sensitive parameters are determined and to minimize the measurement uncertainty of the test results.
Mechanical properties determined by tensile test at low temperatures have been determined at the same rates at room temperature. The revision of this part incorporates the new set of testing rates of GB/T 228.1 and GB/T 228.2, developed to reduce the variability of test results.
Metallic Materials — Tensile Testing — Part 3: Method of Test at Low Temperature
1 Scope
This part of GB/T 228 specifies the terms and definitions, symbols and designations, test piece and determination of its size, apparatus, test conditions, determination of the properties, rounding off for numerical values of test results and test report of tensile testing methods for metallic materials at low temperature.
This part is applicable to the determination of tensile properties of metallic materials at temperatures between -196 °C and <10 °C.
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 228.1-2010 Metallic Materials — Tensile Testing — Part 1: Method of Test at Room Temperature (ISO 6892-1:2009, MOD)
GB/T 12160 Calibration of Extensometer Systems Used in Uniaxial Testing (GB/T 12160-2002, ISO 9513:1999, IDT)
GB/T 16825.1 Verification of Static Uniaxial Testing Machines — Part 1: Tension/Compression Testing Machines — Verification and Calibration of the Force-measuring System (GB/T 16825.1-2008, ISO 7500-1: 2004, IDT)
3 Terms and Definitions
For the purposes of this document, the terms and definitions given in GB/T 228.1-2010 and the following apply.
In general, all test piece geometries/dimensions are based on measurements taken at room temperature. The exception can be the extensometer gauge length (see 3.3).
Note: The following properties are generally not determined at low temperature unless required by relevant specifications or agreement:
— permanent set strength (Rr);
— percentage permanent elongation;
— percentage permanent extension;
— percentage yield point extension (Ae);
— percentage total extension at maximum force (Agt);
— percentage plastic extension at maximum force (Ag);
— percentage total extension at fracture (At).
3.1
original gauge length
Lo
gauge length measured at room temperature before cooling of the test piece and before application of force
3.2
percentage elongation after fracture
A
permanent elongation of the gauge length, measured at room temperature, after fracture (Lu - Lo), expressed as a percentage of the original gauge length (Lo)
Note: For further details, see GB/T 228.1-2010, 3.4.2.
3.3
extensometer gauge length
Le
initial extensometer gauge length used for measurement of extension by means of an extensometer
3.4
extension
increase in the extensometer gauge length (Le) at a given moment during the test
3.4.1
percentage extension
extension expressed as a percentage of the extensometer gauge length (Le)
3.5
percentage reduction of area
Z
maximum change in cross-sectional area which has occurred during the test (So - Su), expressed as a percentage of the original cross-sectional area (So), where So and Su are calculated from the dimensions at room temperature
3.6
stress
R
force at any moment during the test divided by the original cross-sectional area (So) of the test piece
Note: All stresses referenced in this part are engineering stresses, calculated using the cross-sectional area of the test piece derived from dimensions measured at room temperature.
3.7
soaking time
ts
time taken to stabilize the temperature of the test piece prior to mechanical loading
4 Symbols and Designations
For the purposes of this part, symbols and their designations given in GB/T 228.1-2010 and Table 1 apply.
Foreword II
Introduction V
1 Scope
2 Normative References
3 Terms and Definitions
4 Symbols and Designations
5 Principle
6 Test Piece
7 Determination of Original Cross-sectional Area (So)
8 Marking the Original Gauge Length (Lo)
9 Apparatus
10 Test Conditions
11 Determination of the Tensile Properties
12 Rounding Off for Numerical Values of Test Results
13 Test Report
14 Measurement Uncertainty
15 Figures
16 Annexes
Annex A (Informative) Addition to GB/T 228.1-2010, Annexes B and D
Annex B (Informative) Example for Cooling Curves of Steel Depending on Test Piece Dimensions and the Specified Test Temperature in Ethanol and Liquid Nitrogen
Annex C (Informative) Measurement Uncertainty
Bibliography
