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GB/T 39429-2020 PDF in English

GB/T 39429-2020 (GB/T39429-2020, GBT 39429-2020, GBT39429-2020)
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GB/T 39429-2020: PDF in English (GBT 39429-2020)

GB/T 39429-2020
ICS 19.100
J 04
Non-destructive Testing - Method for Thermoelectric
Sorting of Electrically Conductive Materials
Issued by: State Administration for Market Regulation;
Standardization Administration of the People’s Republic of
Table of Contents
Foreword ... 3 
1 Scope ... 4 
2 Normative References ... 4 
3 Terms and Definitions ... 4 
4 Principle of Sorting ... 5 
5 Sorting Methods ... 5 
6 Sorting Conditions ... 6 
7 Sorting Equipment ... 7 
8 Sorting Procedures ... 8 
9 Result Evaluation ... 9 
10 Test Report ... 10 
Non-destructive Testing - Method for Thermoelectric
Sorting of Electrically Conductive Materials
1 Scope
This Standard specifies the techniques and methods for material sorting of conductive
materials using direct and comparative thermoelectric potential sorters based on the
Seebeck effect.
This Standard is applicable to the sorting of metal materials, the piece-by-piece manual
sorting of metal workpieces and automatic sorting of large quantities of metal
workpieces. The identification and sorting of metal plating thickness, hardness and
hardened layer depth may take this Standard as a reference.
2 Normative References
The following documents are indispensable to the application of this document. In
terms of references with a specified date, only versions with a specified date are
applicable to this document. In terms of references without a specified date, the latest
version (including all the modifications) is applicable to this document.
GB/T 20737 Non-destructive Testing - General Terms and Definitions
3 Terms and Definitions
What is defined in GB/T 20737, and the following terms and definitions are applicable
to this document.
3.1 Seebeck Effect
Seebeck effect refers to a phenomenon, in which, an electromotive force is generated
in a loop composed of two conductors when the two contact points of the two
conductors are at different temperatures.
3.2 Comparative Instrumentation
Comparative instrumentation refers to an instrument which is composed of electrode
components (probes) and related electronic circuits. It compares the thermoelectric
potential value of a certain conductive material with the thermoelectric potential value
of a standard test piece to perform material sorting.
method and comparative sorting method. In the direct instrumentation, the data of
standard test pieces with already-known chemical composition and thermal treatment
state is built into the detection system in a standardized mode, and the instrument
directly displays the thermoelectric potential value of the metal being tested. In the
comparative instrumentation, it is necessary to compare the thermoelectric potential
value of the tested metal obtained through the test with the thermoelectric potential
value of one or more already-known standard test pieces, and judge whether it is within
the acceptability limit of a certain type of material.
Both the sorting methods need to be compared with the already-known standard test
pieces. In order to set the acceptability limit, two or more standard test pieces are
needed for calibration.
5.2 Direct Sorting
When the method of direct sorting is used, firstly, a standard test piece with already-
known material is put in contact with an electrode of a set temperature to form a closed
circuit; the direct instrumentation is adjusted to obtain a thermoelectric potential value.
Then, the electrode is put in contact with the metal to be sorted to measure its
thermoelectric potential value.
5.3 Comparative Sorting
When the method of comparative sorting is used, firstly, several standard test pieces
representing the acceptability limit (allowable limit) of a certain type of material are
respectively put in contact with the electrode to form a closed circuit; the parameters
of the comparative instrumentation are adjusted, so that the thermoelectric potential
values of several standard test pieces are in an appropriate section of the indication
range of the instrumentation. Then, put the electrode in contact with the metal to be
sorted; observe the response of the comparative instrumentation; judge whether the
thermoelectric potential value of the metal is within the acceptability limit.
For sorting with high distinguishing requirements, the comparative sorting method
should be adopted. The advantage of the comparative sorting method is that it can
suppress the internal and external interference from the comparative instrumentation,
for example, the temperature change of the tested metal or electrode.
6 Sorting Conditions
6.1 Overview
Whether the thermoelectric potential sorter can successfully realize the sorting
depends on the material of the electrodes, the temperature difference between the two
electrodes, the contact state of the electrode and the metal, and the difference of the
Seebeck effect of the different materials to be sorted. Good contact between the
7.2 Electrodes for Testing
The electrodes can be two or more independent electrodes, or a probe composed of
multiple electrodes. The electrodes shall be able to simultaneously contact the same
surface or different surfaces of the metal.
For manual sorting objects that are small in the testing area and difficult to achieve
effective heating, such as: thin foils, wires and small bearings, etc., the objects may be
fixed with clamps.
7.3 Automatic Sorting Equipment
The automatic sorting equipment used for the sorting of specific metal materials shall
be equipped with mechanical devices for automatic material-loading and automatic
8 Sorting Procedures
8.1 Preparation of Standard Test Pieces
Select two or more test pieces with already-known materials, and test pieces whose
material change can represent the material change of the material to be sorted as the
standard test pieces. Thus, provide the sorter with the acceptability limit of
thermoelectric potential for the material sorting.
8.2 Equipment Calibration
Each time the sorting equipment is re-used or when the metal type to be sorted is
changed, the standard test pieces shall be used to calibrate the equipment.
The calibration steps of the equipment shall be carried out in accordance with the
requirements of the instruction manual of the thermoelectric potential sorter.
During the calibration process, when adjusting the instrument parameters, it shall be
ensured that the value displayed by the instrument represents the thermoelectric
potential value of the standard test piece and is within the indication range of the
instrumentation. In addition, it shall also be ensured that the deviation generated by
the standard test pieces is within the allowable range, in which, the metal to be tested
is distinguishable.
8.3 Sorting and Testing
Sorting and testing can be performed after the equipment is qualified in the calibration.
The sorting shall be performed one by one or batch by batch.
During the sorting and testing, the signal displayed by the instrument shall be observed
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.