ASTM E696-23

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Designation: E696 − 07 (Reapproved 2018) E696 − 23 An American National Standard
Standard Specification for
Tungsten-Rhenium Alloy Thermocouple Wire
This standard is issued under the fixed designation E696; 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 specification covers the requirements for bare, solid conductor, tungsten and rhenium alloy thermoelements having
diameters of 0.127 mm (0.005 in.) to 0.508 mm (0.020 in.) 0.127 mm (0.005 in.) to 0.508 mm (0.020 in.) supplied in matched pairs.
These thermoelements shall be suitable for use either in bead-insulated, bare-wire thermocouples, or in compacted metal-sheathed,
ceramic insulated thermocouple material or assemblies.
1.2 This specification covers the thermocouple combinations of tungsten-3 % rhenium versus tungsten-25 % rhenium (W3Re/
W25Re) and tungsten-5 % rhenium versus tungsten-26 % rhenium (W5Re/W26Re; Type C). All information applies to both
combinations unless otherwise noted.
1.3 It is recognized that the alloys described are refractory and are not suitable for use at high temperatures in oxidizing
atmospheres. All tests and processes described herein must be performed under conditions that are non-reactive to tungsten-
rhenium alloys.
1.4 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
E8E8/E8M Test Methods for Tension Testing of Metallic Materials [Metric] E0008_E0008M
E207 Test Method for Thermal EMF Test of Single Thermoelement Materials by Comparison With Reference Thermoelement
of Similar EMF-Temperature Properties
E220 Test Method for Calibration of Thermocouples By Comparison Techniques
E230E230/E230M Specification for Temperature-Electromotive Force (emf) Tables for Standardized Thermocouples
E344 Terminology Relating to Thermometry and Hydrometry
E452 Test Method for Calibration of Refractory Metal Thermocouples Using a Radiation Thermometer
E988 Temperature-Electromotive Force (EMF) Tables for Tungsten-Rhenium Thermocouples (Withdrawn 2011)
This specification is under the jurisdiction of ASTM Committee E20 on Temperature Measurement and is the direct responsibility of Subcommittee E20.13 on
Thermocouples - Materials and Accessories Specifications.
Current edition approved Nov. 1, 2018July 1, 2023. Published November 2018July 2023. Originally approved in 1979. Last previous edition approved in 20132018 as
E696 – 07 (2013).(2018). DOI: 10.1520/E0696-07R18.10.1520/E0696-23.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
The last approved version of this historical standard is referenced on www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E696 − 23
E1751E1751/E1751M Guide for Temperature Electromotive Force (emf) Tables for Non-Letter Designated Thermocouple
Combinations
3. Terminology
3.1 Definitions:
3.1.1 For definitions used in this standard, see Terminology E344.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 dope, vt—in this specification, to add potassium, silicon and aluminum compounds or other volatile substances to the alloy
powders during the preparation to produce a ductile wire. See NASA CR-72884.
3.2.1.1 Discussion—
Some alloy powders are doped.
3.2.2 lot, n—a quantity of wire processed or heat treated as a single continuous length and identified uniquely.
4. Ordering Information
4.1 A purchase order for thermocouple material conforming to this specification shall specify the following:
4.1.1 Thermocouple Wire Composition—May be W3Re/W25Re or W5Re/W26Re.
4.1.2 Wire Size—Specify size with each order.
4.1.3 Wire Length—Specify total amount of each wire and minimum continuous length.
4.1.4 Thermocouple Calibration—Calibration will be in accordance with Section 5.1.4 unless otherwise specified.
4.1.5 Supplementary Requirements—See the Supplementary Requirements section of this specification.
4.1.6 Instructions for Spooling, Packaging, and Labeling—Packaging will be in accordance with Section 10 unless otherwise
specified.
4.1.7 Tests and Certifications Required from the Processor—Certification will be in accordance with Section 9 unless otherwise
specified.
5. Materials and Manufacture
5.1 Thermocouple Wire:
5.1.1 General—The thermoelements shall be tungsten-3 % rhenium and tungsten-25 % rhenium or tungsten-5 % rhenium and
tungsten-26 % rhenium (Type C), as indicated on the purchase order.
5.1.2 Physical:
5.1.2.1 The diameter of each wire shall be within 60.01 mm (0.0005 in.) 60.01 mm (0.0005 in.) of the ordered size for 0.5 mm
(0.02 in.) 0.5 mm (0.02 in.) diameter wire and smaller. The diameter of each wire shall be uniform end-to-end to within 0.01 mm
(0.0005 in.) for 0.5 mm (0.02 in.) 0.01 mm (0.0005 in.) for 0.5 mm (0.02 in.) diameter wire and smaller.
5.1.2.2 The wires shall be solid, round, smooth and be free of weld joints, slivers, kinks, pits or nicks exceeding 5 % of diameter.
5.1.2.3 The wire surface shall be uniformly clean and free of discoloration.
5.1.2.4 Mechanical or optical methods may be used to verify the requirements of 5.1.2.1, 5.1.2.2, and 5.1.2.3.
NASA CR-72884, “Some Studies on Behavior of W-Re Thermocouple Materials at High Temperatures.” Available from National Aeronautics and Space Administration,
400 Maryland Ave. S.W., Washington, DC 20546. NASA CR-72884, “Some Studies on Behavior of W-Re Thermocouple Materials at High Temperatures.” Available from
National Aeronautics and Space Administration, 400 Maryland Ave. S.W., Washington, DC 20546.
E696 − 23
5.1.3 Mechanical:
5.1.3.1 The wires shall withstand, at a temperature of 2020 °C to 35 °C (68(68 °F to 95 °F), wrapping five turns around a mandrel
five times the diameter of the wire without breaking or splitting.
5.1.3.2 The tests shall be made on at least one specimen from each end of each lot of wire.
5.1.4 Thermoelectric:
5.1.4.1 The emf versus temperature characteristics of the matched thermoelements shall be determined using procedures described
in Test Methods E207, E220, or E452.
5.1.4.2 The emf versus temperature relationship of the matched pair of thermoelements shall comply with the values shown in
Guide E1751E1751/E1751M for W3Re/W25Re or Specification E230E230/E230M for Type C (W5Re/W26Re).
5.1.4.3 The initial calibration tolerance shall be in accordance with Table 1 (W3Re/W25Re). or Specification E230E230/E230M
(W5Re/W26Re), as appropriate.
5.2 Composition:
5.2.1 Positive thermoelement:
5.2.1.1 The positive thermoelement for the W3Re/W25Re combination shall have a nominal composition of 97 % tungsten and
3 % rhenium.
5.2.1.2 The positive thermoelement for the W5Re/W26Re combination shall have a nominal composition of 95 % tungsten and
5 % rhenium.
5.
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