B27R080 0.27mm Grain-Oriented Electrical Steel

 

B27R080 is a 0.27 mm thick grain-oriented electrical steel (GOES) grade manufactured by Baosteel (Baowu Steel), belonging to the laser-scribed, domain-refined (magnetic domain refinement) family of high-permeability oriented silicon steels. It is specifically engineered for high-efficiency transformer cores, where its guaranteed maximum specific total loss of 0.80 W/kg at 1.7 T / 50 Hz (P1.7/50) and minimum magnetic polarization of 1.89 T at 800 A/m (B8) deliver measurable reductions in no-load loss compared with conventional 0.30 mm and 0.35 mm grades.

 

 

The grade designation itself is a compact technical specification:

• B - Baosteel / Baowu Steel, China's largest producer of grain-oriented electrical steel
• 27 - nominal strip thickness, 0.27 mm
• R - magnetic domain refined (laser-scribed) type, a further development of the high-permeability (Hi-B) product line
• 080 - guaranteed maximum specific total loss of 0.80 W/kg measured at 1.7 T, 50 Hz (P1.7/50)

 

Because core loss is the dominant component of a transformer's no-load loss, the low-loss characteristic of B27R080 directly translates into lower energy consumption over the equipment's entire service life. This makes the grade a standard choice for energy-efficiency-driven transformer design, including distribution transformers built to the latest energy-efficiency regulations, power transformers, reactors, instrument transformers, and renewable-energy step-up transformers.

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The table below summarises the guaranteed and typical magnetic properties of B27R080. Guaranteed values are those certified on the mill test certificate and form the contractual basis of supply; typical values represent normal production performance and are used for core design calculations.

Property	Unit	Guaranteed	Typical
Nominal thickness	mm	0.27	0.27
Specific total loss, P1.7/50 (max)	W/kg	0.80	0.78
Magnetic polarization, B8 (min)	T	1.89	1.92
Lamination factor (stacking factor), min	%	95.5	96–97
Assumed density	kg/dm³	7.65	7.65

Test conditions: P1.7/50 - specific total loss measured by the Epstein method at magnetic polarization 1.7 T, frequency 50 Hz; B8 - magnetic polarization at magnetic field strength 800 A/m. Values per GB/T 2521 and IEC 60404-8-7 test methods.

 

 

Parameter	Tolerance / value
Nominal thickness tolerance	+0.010 / −0.020 mm
Longitudinal thickness deviation (over 2000 mm)	+0.015 / 0 mm
Transverse thickness deviation	+0.012 / 0 mm
Width tolerance, cut edge (EC)	+0.5 / 0 mm
Nominal width range	900–1270 mm
Burr height, max	0.025 mm
Coil inner diameter	508 mm (+12/−8 mm)

Tight thickness control matters in lamination production: the uniformity of lamination factor and core stacking height depends directly on the consistency of strip thickness across width and along the coil.

 

 

B27R080 is supplied with a semi-organic/inorganic phosphate-based insulation coating, designated S type (equivalent to JIS T2-class inorganic coating):

Coating property	Value
Coating thickness per side	4–6 μm
Surface insulation resistance (guaranteed)	≥ 30 Ω·cm² per side (typical 80 Ω·cm²)
Annealing resistance	Withstands stress-relief annealing up to approximately 800 °C
Oil and varnish resistance	Resistant to transformer oil, insulating varnish and machine oil

The coating provides inter-lamination insulation, protects the strip surface against corrosion during handling and storage, and must remain intact through slitting and blanking without flaking.

 

 

Property	Typical value
Tensile strength	~378 MPa
Yield strength	~360 MPa
Elongation	~10 %
Hardness (HV1)	~220

Mechanical values are typical production data and are not normally part of the guarantee; refer to the mill test certificate for the specific coil.

 

 

B27R080 is produced and tested in accordance with the major international GOES standards. The Chinese designation B27R080 corresponds to the JIS R-series grade 27R080; equivalent or alternative grades are available from other mills within the same performance window.

Standard / system	Corresponding grade	Note
GB/T 2521 (China)	27R080 class, domain-refined Hi-B	Same designation logic; P1.7/50 ≤ 0.80 W/kg, B8 ≥ 1.89 T
JIS C 2553 (Japan)	27R080	R series = domain-refined, laser-scribed
IEC 60404-8-7 (International)	0.27 mm domain-refined Hi-B class	Tested per IEC 60404-2 / 60404-3 methods
Baosteel family	B27R080 / B27R085 / B27R090	R = domain refined
WISCO (Wuhan Iron & Steel)	27RK080	RK series, domain refined
Nippon Steel (approximate)	27ZH-series domain-refined Hi-B (e.g. 27ZDKH090)	Approximate equivalent; verify against mill data
POSCO (approximate)	27PNX-series domain-refined Hi-B	Approximate equivalent; verify against mill data

Note on equivalents: cross-mill grades with similar P1.7/50 and B8 windows are approximately interchangeable for many designs, but guaranteed values, coating types and mechanical properties can differ. Always confirm the mill test certificate and the exact magnetic guarantee with the supplier before design freeze.

 

 

Within the Baosteel 0.27 mm family, the R-series (domain refined) sits between the high-permeability P-series and the thinnest premium grades in terms of loss performance:

Grade	Thickness (mm)	Typical P1.7/50 (W/kg)	Typical B8 (T)	Type
B27R080	0.27	0.78	1.92	Domain refined
B27R085	0.27	0.82	1.91	Domain refined
B27R090	0.27	0.86	1.90	Domain refined
B27P095	0.27	0.92	1.91	High permeability (Hi-B)
B30R080	0.30	0.88	1.92	Domain refined

The performance step from B27P095 (Hi-B, not scribed) to B27R080 illustrates the benefit of laser scribing: at the same thickness, domain refinement lowers specific total loss by roughly 0.10–0.14 W/kg at 1.7 T/50 Hz with a slight reduction in magnetic polarization.

 

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1. Distribution transformers

The primary application. B27R080 is specified for distribution transformer cores targeting the highest practical energy-efficiency levels per GB 20052-2020 (China), DOE 2016 (US) and Ecodesign (EU) efficiency regulations. Its low P1.7/50 reduces no-load loss, which dominates the lifetime cost of a lightly loaded distribution transformer.

 

2. Power transformers

Used in medium and large power transformer cores where core loss guarantees and noise levels are contractual. The domain-refined microstructure also improves magnetostriction behaviour, supporting lower audible noise - a key requirement in urban substations.

 

3. Renewable-energy step-up transformers

With the rapid build-out of photovoltaic and wind power plants, box-type (prefabricated) step-up transformers are among the fastest-growing GOES applications. B27R080's combination of low loss and high magnetic polarization allows a smaller core cross-section and lighter, more compact transformer design - directly relevant to the containerised/box-type substations widely used in solar and storage power stations.

 

4. Reactors, instrument transformers and special equipment

B27R080 is also used for the cores of reactors, current and voltage transformers, and the electromagnetic cores of large industrial drives and UPS systems, where consistent magnetic properties and low exciting current are required.

 

 

Domain-refined grades such as B27R080 demand specific handling discipline, mainly because the low-loss performance depends on the laser-scribed domain structure applied at the mill:

 

Do not stress-relief anneal after processing.

Stress-relief annealing (typically 780–830 °C for conventional GOES) recrystallises the surface and destroys the laser-scribed domain-refinement effect, which can increase core loss by several percent. If annealing is unavoidable for a specific core construction, discuss the complete processing route with the supplier first - some wound-core designs deliberately use non-scribed Hi-B grades instead.

 

Control cutting and stacking stresses.

Shearing, punching and handling introduce mechanical stress at the strip edges. Use sharp tooling, minimise burr height (≤ 0.025 mm), and avoid bending or kinking the strip.

 

Keep the coating intact.

The S-type coating provides insulation between laminations; scratches, rust or contamination reduce inter-lamination resistance and increase local eddy currents.

 

Store properly.

Keep coils dry and protected. Condensation or long-term high humidity can promote edge rust, which is difficult to remove without damaging the coating.

 

Design for the working flux density.

B27R080 is designed to operate economically in the 1.65–1.75 T range at 50 Hz. Operating beyond the knee of the magnetisation curve increases exciting current and audible noise sharply.

 

 

When sourcing B27R080, the following items should be agreed with the supplier and confirmed on the mill test certificate:

1. Magnetic guarantees - P1.7/50 (max) and B8 (min), per GB/T 2521 / IEC 60404-8-7 test methods
2. Coating type - S type standard; confirm annealing resistance if any thermal processing is planned
3. Edge condition - cut edge (EC) standard
4. Dimensions - nominal width, coil weight, coil inner diameter (508 mm standard)
5. Slitting / cutting services - slitting to narrower widths, cut-to-length, and re-packing for consolidated shipping
6. Documentation - mill test certificate, packing list, and if required, third-party inspection (e.g. SGS, BV)
7. Quantity and lead time - confirm stock availability and production lead time for your order size

 

 

GNEE Steel is a specialist supplier of grain-oriented and non-oriented electrical steel, stocking the full Baosteel R-series and P-series range - from B18R055 up to B30P105 - for transformer and electrical equipment manufacturers worldwide. For B27R080 we offer:

• Genuine mill material with full traceability - mill test certificates supplied with every delivery
• Flexible processing - slitting, cut-to-length, re-packing and export-grade seaworthy packaging
• Technical support - grade selection guidance, core-loss comparison and material substitution advice from engineers familiar with transformer core design
• Global logistics - reliable delivery to ports worldwide with consolidated container options

 

 

Whether you are designing a new high-efficiency distribution transformer, upgrading an existing core design, or simply need a steady supply of B27R080 coils for production, our team can provide quotations, mill certificates and technical data sheets tailored to your specification.

Request a quote or datasheet today - tell us your width, coil weight, coating and destination, and we will respond with a firm offer and mill availability.

 

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FAQ

 

Q: Is B27R080 a high-permeability (Hi-B) or conventional grain-oriented steel?

It belongs to the high-permeability family further processed by laser scribing for domain refinement. Its guaranteed B8 of 1.89 T confirms the Hi-B character, while laser scribing lowers the loss below that of non-scribed Hi-B grades of the same thickness.

 

Q: Can B27R080 be stress-relief annealed after slitting or blanking?

Stress-relief annealing is generally not recommended for domain-refined grades, because the heat treatment eliminates the laser-scribed domain refinement and increases core loss. If annealing is required by the core design, consult the supplier - a non-scribed Hi-B grade may be a better choice.

 

Q: What widths and processing services are available?

Standard widths range from 900 mm to 1270 mm (cut edge). Full-width coils, slit coils, cut-to-length sheets and re-packed lots are available depending on the supplier's processing capability.

 

Q: Which standards apply to B27R080?

The grade is produced to GB/T 2521 and tested per IEC 60404 series methods; it corresponds to JIS C 2553 grade 27R080. Magnetic testing follows the Epstein (IEC 60404-2) and single-sheet (IEC 60404-3) methods.

 

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This article is provided for general information and is based on published mill data and applicable standards (GB/T 2521, JIS C 2553, IEC 60404-8-7). Specific guaranteed values, tolerances and coating properties may vary by coil and production lot; always refer to the mill test certificate and confirm technical details