Change of Resistance With Temperature of Metallic Materials for Electrical Heating

B70-90(2013): Standard Test Method for Change of Resistance With Temperature of Metallic Materials for Electrical Heating

When designing electrical heating elements, understanding how a material's resistance changes with temperature is paramount. ASTM B70-90(2013) provides an essential and authoritative methodology for precisely quantifying this critical property, ensuring the reliable performance and safety of heating applications across numerous industries.

What is B70-90(2013)?

ASTM B70-90(2013) is a comprehensive standard test method developed by ASTM International. It establishes a validated procedure for determining the change in electrical resistance of metallic materials as they are subjected to varying temperatures, specifically within the operational range of electrical heating devices. Its primary purpose is to provide reproducible and accurate data crucial for material selection and performance prediction in heating element design.

Scope & Purpose

This standard governs the experimental determination of resistance-temperature characteristics for metallic materials intended for electrical heating applications. It outlines specific procedures for preparing specimens, controlling furnace temperatures, and performing accurate resistance measurements across a defined temperature spectrum. While it addresses the core resistance-temperature relationship, it explicitly does not cover the material's long-term durability, oxidation resistance, or other performance aspects beyond the immediate resistance change.

Who Must Comply?

• • Primary audience: Materials Scientists, Electrical Engineers, R&D Engineers, and Quality Control Technicians involved in the design, development, and manufacturing of electrical heating components.
• • Industries affected: Electrical Equipment Manufacturing, Aerospace, Automotive, Appliance Manufacturing, Industrial Heating, and any sector utilizing resistive heating elements.
• • Compliance nature: Voluntary, but highly recommended for ensuring product quality and meeting industry best practices.
• • Enforcement: Typically enforced through internal quality assurance protocols, customer specifications, and industry-wide expectations for reliable performance.

Key Requirements Overview

• • The standard requires precise preparation of test specimens, including the proper attachment of current and potential leads to minimize measurement errors.
• • Professionals must ensure the use of a calibrated electric furnace capable of maintaining uniform temperatures within the specified test range.
• • Key provisions include employing suitable resistance measurement instruments (e.g., Kelvin or Wheatstone bridges) with specified accuracy levels.
• • The test procedure mandates controlled temperature decrements and stationary readings to capture accurate resistance values at each point.
• • A proven method for plotting the temperature-resistance curve, using the room-temperature resistance as a baseline, is detailed to visualize material behavior.

Related Standards & References

ASTM B70-90(2013) often works in conjunction with standards related to thermocouple calibration (e.g., ASTM E230) for accurate temperature measurement, and standards for specific metallic alloys used in heating elements (e.g., standards for Nickel-Chromium alloys) to contextualize the test results within material specifications.