This specification covers the requirements for bare solid conductors made of tungsten and rhenium alloy thermoelements supplied in matched pairs. These thermoelements shall be suitable for use in either bead-insulated, bare-wire thermocouples, or in compacted metal-sheathed, ceramic insulated thermocouple material or assemblies. Unless otherwise noted, all information in this specification applies to both thermocouple combinations of tungsten-3 % rhenium versus tungsten-25 % rhenium (W3Re/W25Re) and tungsten-5 % rhenium versus tungsten-26 % rhenium (W5Re/W26Re; Type C). Thermoelements should meet specified physical, mechanical, thermoelectric, and compositional requirements.

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.) 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.