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This standard is prepared in accordance with the rules given in GB/T 1.1-2009.
This standard replaces GB/T 351-1995 Metallic materials - Resistivity measurement method. In addition to a number of editorial changes, the following main technical changes have been made with respect to GB/T 351-1995:
—— the standard name is modified;
—— the definitions of link resistance and lead resistance are deleted;
—— definitions and calculation methods are added for conductivity, conductivity percent IACS, and direct-current resistance ratio;
—— the production inspection is modified to routine inspection;
—— the temperature control of routine inspection is modified from 10℃ ~ 35℃ to (20±5) ℃;
—— the temperature control of arbitration inspection is modified from (20±5) ℃ to (20±1) ℃;
—— the length measuring tool of vernier caliper is added;
—— the rounding off of test result and calculation is added;
—— the schematic diagram for common conductor clamping process equipment (see Annex A);
This standard was proposed by the China Iron and Steel Association.
This standard is under the jurisdiction of the National Technical Committee on Iron and Steel of Standardization Administration of China (SAC/TC 183).
The previous editions of this standard are as follows:
—— GB/T 351-1995.
Metallic materials - Resistivity measurement method
1 Scope
This standard specifies the terms and definitions, test apparatus, specimen, test, test results and calculation, and test record and report for resistivity measurement of metallic materials.
This standard is applicable to the measurement of electrical properties of metallic materials such as volume resistivity, mass resistivity, conductivity, and direct-current (DC) resistance ratio.
The methods provided in this standard are arbitration measurement method and routine measurement method for determining resistivity in the range of 0.01 Ω mm2/m to 2.0 Ω mm2/m under standard conditions.
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.
YB/T 081 Rule for rounding off of numberical values and judgment of testing values for technical standards of metallurgy
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
resistance per unit length
the resistance of conductor of per unit length at a temperature of 20℃
3.2
volume resistivity
the resistance of conductor of per unit length and unit cross-sectional area at a temperature of 20℃
3.3
mass resistivity
the resistance of conductor of per unit length and unit mass at a temperature of 20℃
3.4
conductivity
a parameter used to describe the difficulty degree of charge flow in a substance, with a value equal to the reciprocal of the resistivity
3.5
conductivity percent IACS
based on the International Annealed Copper Standard (IACS), it is a parameter used to express the relative conductivity of a substance, with a value equal to the ratio of the resistivity specified by IACS to the resistivity of the same unit specimen multiplied by 100
3.6
direct-current resistance ratio
the ratio of DC resistance measurement results at different positions of the same specimen or at the same position of the same sample by different processes under the same conditions twice
3.7
Wheatstone bridge
a one-arm bridge, only has two contacts for measuring resistance, referred to as the two-contact method; generally used to measure resistors with higher resistance values
3.8
Kelvin bridge
a double-arm bridge, has four contacts for measuring resistance, referred to as the four-contact method. It is generally used to measure resistors with lower resistance values
3.9
voltage terminal
the blade-like clamp used to clamp the specimen securely to determine the difference of voltage at the two ends of the specimen if the four-contact method is used
3.10
current terminal
the screw fixed clamp used to clamp the specimen securely when the current passes through the specimen if the four-contact method is used
4 Test apparatus
4.1 If the specimen resistance is less than 10 Ω, the Kelvin bridge shall be adopted; if the specimen resistance is not less than 10 Ω, the Wheatstone bridge shall be used. Other instruments meeting the requirements of 4.4 may also be used.
4.2 If special process equipment is used to clamp the specimen, the cutting edges of the voltage terminals shall be sharp and parallel to each other and perpendicular to the axis of the specimen. See Annex A for the schematic diagram of common conductor clamping process equipment
4.3 The distance between the voltage terminal and the corresponding current terminal shall not be less than 1.5 times of the transverse circumference of the specimen.
4.4 The total error of bridge measuring system shall not exceed ±0.15%. The total error includes calibration error of standard resistor, comparison error of specimen and standard resistor, error caused by contact potential and thermoelectric potential, and error caused by heating of specimen induced by measuring current.
4.5 Thermometer: the indication error shall not exceed 0.1 ℃.
4.6 Micrometer: the minimum division value shall not exceed 0.01 mm;
Vernier caliper: the minimum division value shall not exceed 0.1 mm.
4.7 Precision balance: the minimum division value shall not exceed 0.1 mg.
5 Specimen
5.1 The specimen shall be straight. If the specimen cannot be straightened by hand, it may be placed on the plane of soft materials such as wood and rubber, and straightened with a wooden hammer or rubber hammer with slight force.
5.2 The specimen shall be free from visible cracks or defects with a length greater than 1 mm on the surface, as well as dirt such as grease and rust to ensure sound contact.
5.3 In order to ensure the accuracy of measurement, the specimen shall be placed for at least 1 h in the same environment as the measuring equipment such as bridge and standard resistor.
5.4 The gauge length of the specimen shall not be less than 300 mm, and other dimensions shall be compatible with the test apparatus.
Foreword i
1 Scope
2 Normative references
3 Terms and definitions
4 Test apparatus
5 Specimen
6 Test
7 Test results and calculation
8 Test records and reports
Annex A (Informative) Schematic diagram of common conductor clamping process equipment
