ASTM E696-23 PDF

Overview

ASTM E696-23 is the internationally recognized standard specification for tungsten-rhenium alloy thermocouple wire. Developed by ASTM International, this standard outlines the requirements for bare, solid conductors made of tungsten and rhenium alloys, supplied in matched pairs. These wires are specifically designed as thermoelements for use in high-temperature thermocouple assemblies, including bead-insulated, bare-wire thermocouples, or compacted metal-sheathed, ceramic-insulated thermocouples. ASTM E696-23 applies to two specific tungsten-rhenium thermocouple combinations: W3Re/W25Re and W5Re/W26Re (Type C). All requirements are tailored to ensure consistency, reliability, and high performance in demanding industrial applications.

Key Topics

• Thermocouple Wire Combinations

  • W3Re/W25Re (Tungsten-3% Rhenium vs. Tungsten-25% Rhenium)
  • W5Re/W26Re (Tungsten-5% Rhenium vs. Tungsten-26% Rhenium, Type C) These combinations are supplied in diameters from 0.127 mm to 0.508 mm and are delivered as matched pairs.

• Physical and Mechanical Requirements

  • Wire must be solid, round, smooth, and free from visible defects such as welds, kinks, and slivers.
  • Strict diameter and uniformity tolerances ensure compatibility and accuracy.
  • Mechanical integrity is verified by mandrel wrap and elongation tests for ductility.

• Thermoelectric Characteristics

  • Thermoelements must meet specified standards for emf (electromotive force) versus temperature relationships, using accepted calibration techniques.
  • Initial calibration tolerances ensure accurate, repeatable measurements.

• Compositional Requirements

  • Positive and negative wires must conform to the nominal tungsten and rhenium compositions required for each thermocouple type.
  • Doping is allowed to support grain structure and long-term workability.

• Packaging and Documentation

  • Each spool is clearly labeled and matched for correct pairing.
  • Certificates of analysis and calibration data are provided with every lot.

Applications

• High-Temperature Measurement Tungsten-rhenium thermocouple wires are primarily used in extreme environments where conventional thermocouple materials are unsuitable. Typical applications include:

  • Industrial furnaces and kilns
  • Aerospace and propulsion testing
  • Metallurgy and materials research
  • Nuclear and particle physics experiments

• Bead-Insulated & Metal-Sheathed Assemblies The specification allows use in bare-wire or more robust metal-sheathed, ceramic-insulated thermocouple assemblies, catering to diverse process requirements.

• Research and Development The high melting point and stability of tungsten-rhenium alloys make them ideal for laboratory measurement systems and scientific instrumentation operating at elevated temperatures in inert or vacuum atmospheres.

• Extension Leads To reduce costs and address ductility challenges, compensating extension wires made of suitable base metal alloys may be used for connecting the sensing element to the measuring instruments, as defined in related tables and standards.

Related Standards

• ASTM E8/E8M - Test Methods for Tension Testing of Metallic Materials
• ASTM E207 - Thermal EMF Test for Thermoelement Materials
• ASTM E220 - Calibration of Thermocouples By Comparison Techniques
• ASTM E230/E230M - Specification for Temperature-EMF Tables for Standardized Thermocouples
• ASTM E344 - Terminology Relating to Thermometry and Hydrometry
• ASTM E452 - Calibration of Refractory Metal Thermocouples Using a Radiation Thermometer
• ASTM E1751/E1751M - Guide for EMF Tables for Non-Letter Designated Thermocouple Combinations

These documents support calibration, terminology, and the testing of thermocouple wires, ensuring comprehensive quality and interoperability in temperature measurement systems.

Keywords: tungsten-rhenium thermocouple, ASTM E696-23, high temperature measurement, thermoelements, W3Re/W25Re, W5Re/W26Re, Type C thermocouple wire, refractory metal thermocouples, industrial temperature sensing.