IEC 60404-8-7:2020

Overview

IEC 60404-8-7:2020 is an international standard that specifies grades and delivery requirements for cold-rolled grain-oriented electrical steel strip and sheet delivered in the fully processed (final annealed) state. It applies to Goss-textured grain-oriented electrical steel in nominal thicknesses of 0.20 mm, 0.23 mm, 0.27 mm, 0.30 mm and 0.35 mm, intended for the construction of magnetic circuits (e.g., transformer and reactor cores). The standard defines general requirements, magnetic properties, geometric characteristics, tolerances, technological characteristics and inspection procedures.

Key topics

• Classification and grades
  • Three classes: conventional grades, high permeability grades, and magnetic domain refined high permeability grades.
  • Corresponds to Class C22 of IEC 60404-1.
• Magnetic property measurement
  • Conventional and high-permeability grades use the Epstein method (IEC 60404-2).
  • Magnetic domain refined high-permeability grades use the Single Sheet Tester (SST) method (IEC 60404-3) as the reference measurement.
  • A conversion factor F = 0.925 is defined to transpose SST loss results to equivalent Epstein values for continuity across grade listings.
• Geometric and technological requirements
  • Defines thickness, width and length tolerances, edge condition, residual curvature, stacking factor, insulation coating resistance and other technological characteristics important for manufacturing and assembly.
• Inspection and testing
  • Procedures for sample selection, specimen preparation, magnetic testing and geometric checks are specified to ensure consistent evaluation and acceptance.

Applications and users

• Primary applications:
  • Transformer cores, power and distribution transformers
  • Reactors, magnetic circuits, and other electromagnetic devices requiring oriented electrical steel
  • High-efficiency and low-loss magnetic assemblies (where high permeability and domain refinement are critical)
• Typical users:
  • Steel manufacturers and rolling mills for product specification and quality control
  • Transformer and motor designers specifying core materials
  • Procurement and quality engineers verifying supplier deliveries
  • Testing laboratories applying Epstein and SST measurement protocols

Practical value

• Enables consistent material selection for magnetic circuit performance (losses, permeability, stacking behavior).
• Clarifies measurement methods and conversion between SST and Epstein results, helping purchasers and designers compare modern domain-refined steels with conventional grades.
• Standardized tolerances and inspection rules reduce acceptance disputes and improve interchangeability between suppliers.

Related standards

• IEC 60404-1 (Classification of magnetic materials) - Class C22 reference
• IEC 60404-2 (Epstein frame method for specific total loss)
• IEC 60404-3 (Single Sheet Tester - SST method)
• Other parts of the IEC 60404 series for magnetic materials

Keywords: IEC 60404-8-7, cold-rolled grain-oriented electrical steel, magnetic materials, single sheet tester, Epstein method, magnetic domain refined, transformer core steel.