Two electrical steel coils can carry the same grade but still have different measured core loss. One may test at 0.71 W/kg and another at 0.75 W/kg under the same conditions. Both can meet the grade requirement.

So when preparing an RFQ, should you specify the grade alone, or set a core-loss requirement as well?

Quick Answer

For a standard purchase, specify the electrical steel grade, thickness, applicable standard, and dimensions. Add a core-loss requirement when the project has a specific loss target or when the measured value affects material selection or price.

If you require a specific value, state it in the RFQ together with the test conditions. A result from a previous coil is reference data unless the supplier agrees to it for the new order.

What the Electrical Steel Grade Tells You — and What It Doesn't

An electrical steel grade defines the material against a particular grading system. Depending on the system, the designation may include nominal thickness and a maximum core-loss limit under defined test conditions.

That limit is a compliance boundary, not the expected test result for every coil.

Term	What It Means for the Buyer
Electrical steel grade	Identifies the material under the applicable grading system
Standard core-loss limit	The maximum permitted loss under specified test conditions
Measured core loss	The actual test result for a sample, batch, or coil
Agreed core-loss requirement	The value the supplier has agreed to meet for the order

If you need to understand how electrical steel grade designations are structured, see our guide to electrical steel grades.

When Is the Grade Usually Enough?

Not every order needs a separate core-loss target. If the specified grade already meets the design requirement, a tighter limit may add cost or sourcing constraints without changing the practical outcome.

A standard RFQ may include:

electrical steel grade;
applicable standard;
nominal thickness;
width and coil dimensions;
quantity;
coating or other required specifications.

When Should Buyers Pay Attention to Actual Core Loss?

The Project Has a Specific Loss Target

If the design requires a specific core-loss limit, such as P1.7/50 ≤ 0.90 W/kg, the grade alone may not be enough. The buyer should include that limit in the material requirement and confirm that the supplier can meet it under the specified test conditions.

1788763315615-Electrical Steel Core Loss Testing.webp

Electrical steel core loss testing under specified frequency and magnetic flux density conditions

A Tender Defines the Core-Loss Requirement

Some tenders and technical specifications already set a maximum material core loss. Carry the specified test conditions into the RFQ rather than replacing them with a general request for a "low-loss" grade.

A value such as 0.90 W/kg means little without the corresponding frequency and magnetic polarization or flux density.

You Are Comparing Material Within the Same Grade

When two offers use the same grade, measured core loss can be useful when comparing price. A lower-loss coil is not automatically the better purchase. If the higher-loss option already meets the project requirement, paying extra for a lower measured value may offer little benefit. Where core loss directly affects equipment performance, however, the lower value may justify the additional cost.

A Previous Test Result Is Not a Requirement for the Next Order

Suppose the material certificate from a previous order shows:

P1.7/50 = 0.93 W/kg

That result applies to the material tested. It does not mean the next coil of the same grade must also be 0.93 W/kg or lower.

For example, if the next coil measures 0.96 W/kg but still meets the grade requirement, it may be acceptable under a grade-only order. If your application requires P1.7/50 ≤ 0.93 W/kg, put that limit in the RFQ and have the supplier confirm it before ordering.

For repeat orders, it is also worth looking beyond the result on a single material certificate. Batch-to-batch consistency depends in part on how closely the production process is controlled.

HWHG addresses this across key production stages, from tandem rolling and heat treatment to decarburization, nitriding, coating, and tension leveling, supported by digital monitoring and inspection. Together, these measures help reduce batch-to-batch variation in core-loss performance.

HWHG electrical steel production equipment including tandem mill decarburization nitriding and tension leveling lines

How to Specify Core Loss in an RFQ

Avoid specifying only:

Core loss ≤ 1.0 W/kg

Without the test conditions, the number is incomplete.

A core-loss requirement may include:

Electrical steel grade
Nominal thickness
Required or target core loss
Magnetic polarization or flux density
Frequency
Applicable test method or standard
Quantity and coil dimensions
Required test documentation

For example:

Grade: [specified grade]
Thickness: 0.23 mm
Target core loss: P1.7/50 ≤ X W/kg
Test standard: [applicable standard]
Documentation: Actual measured core-loss value required

How HWHG Uses Actual Core Loss in Pricing

Traditional electrical steel pricing is often based mainly on grade. This can result in two coils receiving the same price even when their measured core loss is different.

HWHG factors verified core-loss values into pricing within the same grade. Instead of treating all compliant coils as having the same value, the price can reflect differences in their measured loss performance.

This matters when buyers have a specific performance target. A project that only requires grade compliance may not benefit from paying for the lowest core loss available. A transformer design with a tighter loss target, however, may place more value on a coil with a lower verified result.

Using the actual core-loss value gives buyers another way to compare performance against cost. The purchasing decision can then be based on the loss level the project requires, rather than on grade alone.

HWHG electrical steel pricing based on verified core loss values within the same grade

Check the Measured Value Against What You Ordered

At incoming inspection, check the material certificate against the requirement in the order. If the order specifies only the grade, verify grade compliance. If it includes an agreed core-loss limit, verify the measured result against that limit.

Do not use a typical datasheet value or a previous batch result as the acceptance criterion unless it was part of the order.

Electrical Steel Grade vs. Actual Core Loss: What Should Buyers Specify?

How Drone BLDC Motor Manufacturers Select Electrical Steel for Different Operating Conditions

Hysteresis Loss in Electrical Steel: What Changes It and Why It Matters

50,000 RPM EV Motors: What Ultra-High-Speed Designs Mean for Electrical Steel

Send Your Drawing or Specs, Get a Fast Material Quote