Electrical Steel

Electrical Steel

Mapes & Sprowl Steel is a full-service supplier of electrical steel, specializing in Grain Oriented (GO), Non-Grain Oriented (NGO), and Cold Rolled Motor Lamination (CRML). We also offer thin gauge, low loss grades for special applications with technical support to better understand customer needs and recommend most cost-effective material for intended applications. Our engineering department can offer extensive material characterization in Epstein or Ring form.

Some of our in-house engineering technical support capabilities include:

• Epstein testing.
• ASTM A717 coating Franklin measurement.
• Material selections review and support.
• Specialized testing for Single Phase and Three Phase cores.
• Coating Thickness measurement using Fischer Beta Backscattering Technology. We also retain an Eddy type coating measurement system.

Specification Charts

Electrical Steel Selection Guide

Material Specifications

Classification of Interlaminar Insulation Coatings ASTM A976

Grain Oriented Steel (GO) – ASTM A876

These are silicon electrical steel grades that possess magnetic properties that are strongly oriented with respect to the direction of rolling. Because of the crystal structure in which grains are aligned, Grain Oriented steel possesses vastly superior magnetic properties in the rolling direction. These grades are fully processed, but are generally given a final anneal to eliminate additional stresses exposed during the manufacturing process, for smaller part sizes or Cut to Length (CTL) products. Grain Oriented steel is primarily used in the production of transformers, inductors, and other applications which call for improved permeability at high flux densities, and low core losses.

We typically offer Grain oriented material with C5 over C2 coating known as Shearing Quality (SQ), but we can also supply Punching Quality (PQ) standard GO grades. For further details regarding Grain Oriented steel (GO) please see ASTM A876.

We also offer low loss Domain Refined Grain Oriented steel, either Mechanically or Laser scribed.

Non-Oriented Steel (NGO) – ASTM A677 or ASTM A683

These are silicon electrical steels with magnetic properties relatively consistent in any direction of magnetization in the plane of material, typically with low anisotropy in magnetic characteristics. These materials contain Medium to High alloy content depending on core loss requirement. These materials are available in Fully-Processed (FP) – ASTM A677 or Semi-Processed (SP) – ASTM A683 condition. Fully-Processed electrical steel has had their magnetic properties completely developed by the mill. Semi-Processed electrical steel requires a final heat treatment known as Quality Development Anneal (QDA). For Fully-Processed material a Stress Relief Anneal (SRA) is required to achieve optimum magnetic performance.

These grades are typically supplied with an insulating coating applied at the mill.  Material can be supplied with C3, C4, C5/C5A or (C6/C6A, † NOT recommended in ASTM A976) coatings types as specified by end user.  For further details regarding Insulation Coating please see ASTM A976.

Cold Rolled Motor Lamination (CRML) – ASTM A726

CRML is an electrical grade of steel containing low amounts of alloy. These grades are specifically developed for magnetic applications not requiring extremely low core losses or for those applications not requiring magnetic characteristics of high-silicon electrical steel. CRML is a lower cost option material for volume applications. Ease of stamping and reduced tool wear, extends die life and minimizes costs over the life of the tool. This class of electrical steel is Semi-Processed and must undergo a Quality Development Anneal (QDA) to develop full magnetic characteristics. In some motor applications the rotor lamination may be supplied in “AS STAMPED” or heat treated through a “ROTOR” anneal cycle. With most recent advancements in steel making CRML material is offered in Extra Low or Ultra Low carbon levels with improved permeability.

This class of electrical steel does not have an insulating coating supplied as applied by the mill.  After a Quality Development Anneal (QDA) or Rotor Anneal an insulating coating is formed in the last phase of the anneal, typically known as a Blue Oxide or Steam Blue with ASTM A976 designation of C1. This type of coating with limited interlaminar resistivity characteristics, forms on surfaces and cut edges of laminations and is primarily suitable for small Motor and Transformer applications. For further details regarding Cold Rolled Motor Lamination (CRML) please see ASTM A726.

Commercial Quality (CQ)