GB/T 20831-2025 Method of test for the thermal endurance of surface insulation coatings of electrical sheet and strip

Scope

This document describes the test method for thermal durability of insulating coatings on electrical steel strips (sheets).
This document defines the general principles and technical details for evaluating the thermal durability of insulating coatings on electrical steel strips (sheets) after heat treatment at specified temperatures (up to 850 °C) and for specified durations (up to 2,500 hours), including the principles, samples, test steps, measurement results, and test reports.
The specified performance is measured at an ambient temperature of 23 ± 5 °C before and after heat treatment. This document applies to the following performance of insulating coatings:
—— Adhesion;
—— Surface insulation resistance/interlayer insulation resistance;
—— Laminating coefficient.
This document does not apply to other performance of insulating coatings, such as welding performance or other performance that may cause discoloration when exposed to high temperatures. Due to its long-term testing nature, this document is not suitable for acceptance testing of specific order materials.

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