ASTM E977-05(2014)
(Practice)Standard Practice for Thermoelectric Sorting of Electrically Conductive Materials
Standard Practice for Thermoelectric Sorting of Electrically Conductive Materials
ABSTRACT
This practice covers the procedure for sorting electrically conductive materials using the thermoelectric method, which is based on the seebeck effect. The procedure relates to the use of direct- and comparator-type thermoelectric instruments for distinguishing variations in materials which affect the thermoelectric properties of those materials. The two techniques that are primarily used in thermoelectric sorting are direct and comparative instrumentation. In the direct instruments, equipment is standardized by placing materials with known chemistry and metallurgical structure in the test system. In the comparative instruments, the thermoelectric response of the test piece is compared with that of a known standard(s) and the response indicates whether the piece is within the acceptance limits. The electronic apparatus shall be capable of maintaining a sufficient temperature differential across the electrodes to produce a suitable thermoelectric voltage. The different procedures for sorting electrically conductive materials are presented in details.
SCOPE
1.1 This practice covers the procedure for sorting materials using the thermoelectric method, which is based on the Seebeck effect. The procedure relates to the use of direct- and comparator-type thermoelectric instruments for distinguishing variations in materials which affect the thermoelectric properties of those materials.
1.2 While the practice is most commonly applied to the sorting of metals, it may be applied to other electrically conductive materials.
1.3 Thermoelectric sorting may also be applied to the sorting of materials on the basis of plating thickness, case depth, and hardness.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: E977 − 05 (Reapproved 2014)
Standard Practice for
Thermoelectric Sorting of Electrically Conductive Materials
This standard is issued under the fixed designation E977; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2.1.4 electrode—the conductors used in thermoelectric sort-
ing instruments used to generate the Seebeck effect with the
1.1 This practice covers the procedure for sorting materials
material under test.
using the thermoelectric method, which is based on the
2.1.5 Seebeck effect—the thermoelectric electromotive force
Seebeck effect. The procedure relates to the use of direct- and
(emf) produced in a circuit connecting two dissimilar conduc-
comparator-type thermoelectric instruments for distinguishing
tors at two points of different temperatures. The magnitude of
variations in materials which affect the thermoelectric proper-
this emf is a function of the chemistry of the materials, surface
ties of those materials.
metallurgical structure, and the temperature at the junctions.
1.2 While the practice is most commonly applied to the
See Fig. 1.
sorting of metals, it may be applied to other electrically
conductive materials.
3. Summary of Practice
1.3 Thermoelectric sorting may also be applied to the
3.1 The two techniques that are primarily used in thermo-
sorting of materials on the basis of plating thickness, case
electric sorting are direct and comparative instrumentation. In
depth, and hardness.
the direct instruments, equipment is standardized by placing
1.4 This standard does not purport to address all of the
materials with known chemistry and metallurgical structure in
safety concerns, if any, associated with its use. It is the
the test system. The value of the thermoelectric voltage (or
responsibility of the user of this standard to establish appro-
arbitrary unit) is read on the scale of an indicator. In the
priate safety and health practices and determine the applica-
comparative instruments, the thermoelectric response of the
bility of regulatory limitations prior to use.
test piece is compared with that of a known standard(s) and the
response indicates whether the piece is within the acceptance
2. Terminology
limits.
2.1 Descriptions of Terms:
3.1.1 Both kinds of instrumentation require comparing the
2.1.1 acceptance limits—the thermoelectric response that
pieces to be examined with the known standard(s). Two or
establishes the group into which the material being examined
more samples representing the acceptance limits may be
belongs.
required.
2.1.2 comparativeinstrumentation—a system that uses elec- 3.1.2 Direct Thermoelectric Instrumentation—a known
trode assemblies (probes), associated electronics, and known standard(s) is inserted in the system and the controls of the
standards to measure a thermoelectric response from an instrument are adjusted to obtain a voltage (or arbitrary unit)
electrically-conductive material. This response is compared reading(s). The process is then continued by inserting the
with that of the reference standard. pieces to be sorted into the system, and observing the instru-
ment reading(s).
2.1.3 direct instrumentation—a system that specifically
3.1.3 Comparative Instrumentation—Known standards rep-
measures and displays the voltage (or an arbitrary unit)
resenting the acceptance limits are inserted into the system.
generated between the electrodes when they are at different
The instrument controls are adjusted for appropriate response.
temperatures and in contact with the material.
The process is then continued by inserting the pieces to be
sorted in the system, and observing the instrument response.
This practice is under the jurisdiction of ASTM Committee E07 on Nonde-
structive Testing and is the direct responsibility of Subcommittee E07.10 on
3.2 In both instruments, the range of the instrument re-
Specialized NDT Methods.
sponse must be adjusted during standardization so that any
CurrenteditionapprovedJune1,2014.PublishedJuly2014.Originallyapproved
anticipated deviation from the known standard(s) will be
in 1984. Last previous edition approved in 2008 as E977 - 05 (2008). DOI:
10.1520/E0977-05R14. recognized as within the required acceptance limits.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E977 − 05 (2014)
FIG. 1 Typical Circuit Used in Thermoelectric Material Sorting Instruments
3.3 The examination process may consist of manual inser- 5.1.3 Contaminates that will electrically insulate material
tion of one piece after another into the system, or an automated being examined, such as rust, grease, oil, mill scale; or surface
feeding and classifying mechanism may be employed. coatings such as paint, plastic, and so forth, must be removed
to ensure clean contact between the material and the electrodes
4. Application of the device.
5.1.4 Extreme temperature differences between the stan-
4.1 Thermoelectric techniques provide a method for sorting
dard(s) and the pieces will alter the emf generated. Known
large quantities of conductive materials. The ability to accom-
standard(s) should be at the same temperature as the pieces
plish satisfactorily these types of separations is dependent upon
being examined.
the relation of the thermoelectric voltages with regard to
5.1.5 The geometry and mass of the standard and part need
composition, condition, structure, and processing.
not be a consideration to permit sorting. Fixturing may be
4.2 Comparative instrumentation is used when high-
required where the part mass is insufficient to provide an
sensitivity testing is required. The advantage of this method is
adequate heat sink (for example, thin foil, small-diameter wire,
that it reduces internal or external disturbances such as
small bearings, etc.).
temperature variations of the material or probes, or both.
5.1.6 Interference may be caused by radio frequency pro-
4.3 The success of an attempted sort will be affected by
duced by devices such as arc welders or radio and radar
instrument factors such as electrode composition, electrode
transmitters. This interference may be observed when the
temperature differential, and electrode contact.
equipment is used in proximity to the above mentioned r-f
sources.
4.4 The degree of reliability of instrument readings will be
5.1.7 If changes in the surface
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: E977 − 05 (Reapproved 2010) E977 − 05 (Reapproved 2014)
Standard Practice for
Thermoelectric Sorting of Electrically Conductive Materials
This standard is issued under the fixed designation E977; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This practice covers the procedure for sorting materials using the thermoelectric method, which is based on the Seebeck
effect. The procedure relates to the use of direct- and comparator-type thermoelectric instruments for distinguishing variations in
materials which affect the thermoelectric properties of those materials.
1.2 While the practice is most commonly applied to the sorting of metals, it may be applied to other electrically conductive
materials.
1.3 Thermoelectric sorting may also be applied to the sorting of materials on the basis of plating thickness, case depth, and
hardness.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use.
2. Terminology
2.1 Descriptions of Terms:
2.1.1 acceptance limits—the thermoelectric response that establishes the group into which the material being examined belongs.
2.1.2 comparative instrumentation—a system that uses electrode assemblies (probes), associated electronics, and known
standards to measure a thermoelectric response from an electrically-conductive material. This response is compared with that of
the reference standard.
2.1.3 direct instrumentation—a system that specifically measures and displays the voltage (or an arbitrary unit) generated
between the electrodes when they are at different temperatures and in contact with the material.
2.1.4 electrode—the conductors used in thermoelectric sorting instruments used to generate the Seebeck effect with the material
under test.
2.1.5 Seebeck effect—the thermoelectric electromotive force (emf) produced in a circuit connecting two dissimilar conductors
at two points of different temperatures. The magnitude of this emf is a function of the chemistry of the materials, surface
metallurgical structure, and the temperature at the junctions. See Fig. 1.
3. Summary of Practice
3.1 The two techniques that are primarily used in thermoelectric sorting are direct and comparative instrumentation. In the direct
instruments, equipment is standardized by placing materials with known chemistry and metallurgical structure in the test system.
The value of the thermoelectric voltage (or arbitrary unit) is read on the scale of an indicator. In the comparative instruments, the
thermoelectric response of the test piece is compared with that of a known standard(s) and the response indicates whether the piece
is within the acceptance limits.
3.1.1 Both kinds of instrumentation require comparing the pieces to be examined with the known standard(s). Two or more
samples representing the acceptance limits may be required.
3.1.2 Direct Thermoelectric Instrumentation—a known standard(s) is inserted in the system and the controls of the instrument
are adjusted to obtain a voltage (or arbitrary unit) reading(s). The process is then continued by inserting the pieces to be sorted
into the system, and observing the instrument reading(s).
This practice is under the jurisdiction of ASTM Committee E07 on Nondestructive Testing and is the direct responsibility of Subcommittee E07.10 on Specialized NDT
Methods.
Current edition approved June 1, 2010June 1, 2014. Published November 2010July 2014. Originally approved in 1984. Last previous edition approved in 20052008 as
E977 - 05.E977 - 05 (2008). DOI: 10.1520/E0977-05R10.10.1520/E0977-05R14.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E977 − 05 (2014)
FIG. 1 Typical Circuit Used in Thermoelectric Material Sorting Instruments
3.1.3 Comparative Instrumentation—Known standards representing the acceptance limits are inserted into the system. The
instrument controls are adjusted for appropriate response. The process is then continued by inserting the pieces to be sorted in the
system, and observing the instrument response.
3.2 In both instruments, the range of the instrument response must be adjusted during standardization so that any anticipated
deviation from the known standard(s) will be recognized as within the required acceptance limits.
3.3 The examination process may consist of manual insertion of one piece after another into the system, or an automated feeding
and classifying mechanism may be employed.
4. Application
4.1 Thermoelectric techniques provide a method for sorting large quantities of conductive materials. The ability to accomplish
satisfactorily these types of separations is dependent upon the relation of the thermoelectric voltages with regard to composition,
condition, structure, and processing.
4.2 Comparative instrumentation is used when high-sensitivity testing is required. The advantage of this method is that it
reduces internal or external disturbances such as temperature variations of the material or probes, or both.
4.3 The success of an attempted sort will be affected by instrument factors such as electrode composition, electrode temperature
differential, and electrode contact.
4.4 The degree of reliability of instrument readings will be affected greatly by the coupling between the electrodes and the part
and the accuracy with which the temperature is held constant during the measuring period. The surface of the materials and of both
electrodes must be kept free of any insulating materials such as surface oxide, dirt, paint, or other foreign material.
5. Interference
5.1 The specific influence of the following variables must be considered for proper interpretation of the results obtained:
5.1.1 A correlation shall be established so that if the thermoelectric properties of the various groups overlap, auxiliary methods
are used for supplementary examination.
5.1.2 In sorting materials, a temperature differential must be used that will result in a well-defined separation of the
thermoelectric properties.
5.1.3 Contaminates that will electrically insula
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