B27R090 Vs B23R090 Grain-Oriented Silicon Steel: 0.27mm Vs 0.23mm Thickness Comparison For Transformer Core Selection

When specifying grain-oriented silicon steel for transformer cores, engineers and procurement teams frequently face a deceptively simple question: two grades with the same guaranteed core loss of 0.90 W/kg (P1.7/50) but different thickness - 0.27 mm versus 0.23 mm. Does the thinner gauge actually perform better, and is it worth the cost premium?

 

This article provides a side-by-side technical comparison of B27R090 and B23R090, two Baosteel (B-prefix) grain-oriented silicon steel grades, and explains how the 0.04 mm gauge difference translates into real-world differences in core loss behavior, manufacturability, cost, and transformer efficiency.

 

Both grades follow the Baosteel grain-oriented silicon steel coding convention:

Code Segment	B27R090	B23R090	Meaning
B	B	B	Baosteel manufacturer prefix
27 / 23	27 → 0.27 mm	23 → 0.23 mm	Nominal thickness × 100
R	R	R	High heat-resistant insulation coating, non-laser scribed
090	090 → 0.90 W/kg	090 → 0.90 W/kg	Maximum core loss P1.7/50 × 100

The critical observation: both grades are guaranteed to the same 0.90 W/kg core loss limit at 1.7 T and 50 Hz, and both carry the R suffix indicating a high-heat-resistant insulation coating without laser scribing. The only specification difference is nominal thickness: 0.27 mm vs 0.23 mm.

 

 

Property	B27R090	B23R090	Difference / Note
Manufacturer	Baosteel	Baosteel	Same mill
Material type	CRGO, grain-oriented	CRGO, grain-oriented	Same class
Nominal thickness	0.27 mm	0.23 mm	0.04 mm difference
Core loss P1.7/50	≤ 0.90 W/kg	≤ 0.90 W/kg	Same guaranteed limit
Core loss P1.7/60 (typical)	~1.10 W/kg	~1.05 W/kg	B23R090 slightly lower at 60 Hz
Magnetic induction B8	≥ 1.88 T	≥ 1.88 T	Same (both R-type GO)
Silicon content	2.9 – 3.3 %	2.9 – 3.3 %	Same composition range
Density	~ 7.65 g/cm³	~ 7.65 g/cm³	Identical
Stacking factor	≥ 0.96	~ 0.95 – 0.955	B27R090 slightly higher (thicker = flatter stack)
Coating type	R - high heat-resistant, non-scribed	R - high heat-resistant, non-scribed	Same; both tolerate stress-relief annealing
Laser scribing	No	No	Neither is domain-refined
Edge condition	ME / SE	ME / SE	Both available mill edge or slit edge
Supply form	Coil, slit coil, cut-to-length	Coil, slit coil, cut-to-length	Same
Standards	GB/T 2521; IEC 60404-8-7; ASTM A876	GB/T 2521; IEC 60404-8-7; ASTM A876	Same standard framework

 

This is the central question of the comparison. Both grades are specified at ≤0.90 W/kg, so on paper their guaranteed iron loss is identical. However, the physics behind achieving that number differs significantly depending on gauge:

 

Eddy-Current Loss Scales with Thickness Squared

Core loss in grain-oriented steel = hysteresis loss + eddy-current loss + anomalous loss. The eddy-current component is proportional to thickness squared (t²). Reducing gauge from 0.27 mm to 0.23 mm reduces the eddy-current term by approximately:

 

(0.23 / 0.27)² ≈ 0.726 → ~27% reduction in eddy-current loss

 

This means B23R090 (0.23mm) has significantly more "headroom" in its eddy-current budget than B27R090 (0.27mm) to achieve the same 0.90 W/kg. In practical terms:

• B27R090 must rely more on superior Goss texture and cleaner steel chemistry to keep hysteresis loss low enough to compensate for higher eddy loss at 0.27mm - it is a more demanding metallurgical specification for the same loss target.
• B23R090 achieves 0.90 W/kg more comfortably because the thinner gauge naturally suppresses eddy currents - the 0.23mm grade typically shows lower actual (measured) loss than its 0.90 guarantee in practice.

 

Actual Measured Loss vs. Guaranteed Loss

In real mill test certificates, the actual measured core loss is typically below the guaranteed maximum:

Metric	B27R090 (0.27mm)	B23R090 (0.23mm)	Implication
Guaranteed P1.7/50	0.90 W/kg	0.90 W/kg	Same spec
Typical actual P1.7/50	~0.85 – 0.88 W/kg	~0.80 – 0.84 W/kg	B23R090 has more margin below guarantee
Excitation power at 1.7 T	Comparable	Slightly lower	Thinner gauge, lower anomalous loss

 

Stacking Factor

The stacking factor (fill factor) represents the ratio of steel volume to total core volume in a stacked core. Thinner gauge means more laminations for the same stack height, and more coating layers and air gaps:

• B27R090 (0.27mm): Stacking factor ≥ 0.96 - higher active steel cross-section, more efficient use of core window area
• B23R090 (0.23mm): Stacking factor ~0.95 - slightly lower, meaning a marginally larger core is needed for the same magnetic cross-section

 

 

For a given transformer rating, the 0.27mm core can be ~1% smaller in core cross-section than the 0.23mm core, which also slightly reduces copper length in the windings.

 

Punching, Shearing and Annealing

Process Factor	B27R090 (0.27mm)	B23R090 (0.23mm)
Shearing / punching difficulty	Easier - thicker material, more rigid	More challenging - thinner, more prone to waviness and burr
Burr formation	Less critical	Requires tighter tooling clearance control
Stress-relief annealing	Both tolerate annealing (R-type coating is heat-resistant)	Same - R coating designed for annealing
Handling in automated stacking lines	More robust	Requires gentler handling
Core winding (wound cores)	Good formability	Even better - thinner material winds tighter

 

Coating and Scribing

 

Both grades carry the R suffix - high heat-resistant insulation coating, non-laser scribed.

 

This is significant because:

• R coating tolerates stress-relief annealing after cutting/punching without degradation - unlike P-type (laser scribed) grades where annealing can destroy the domain-refinement effect
• If a customer later wants lower loss, either grade can be upgraded to the P variant (B27P090 / B23P090) for domain refinement - but at the cost of annealing compatibility
• The R suffix makes both grades suitable for step-lap core cutting lines and wound core manufacturing where annealing is part of the process

 

Cost / Supply Factor	B27R090 (0.27mm)	B23R090 (0.23mm)
Relative material cost	Baseline (lower)	~8–15% premium
Mill availability	Widely produced, standard 0.27mm gauge	Produced but lower volume; 0.23mm is a thinner specialty gauge
Lead time	Shorter - standard production	Potentially longer - thinner gauge, smaller production runs
Slitting yield	Higher - thicker material, less edge wave	Lower - thinner material more sensitive to slitting parameters
Weight per coil (same OD)	Heavier coil	Lighter coil - more coils needed for same tonnage

 

 

Choose B27R090 (0.27mm) When:

• Cost is the primary driver - you need 0.90 W/kg guaranteed performance at the best price
• Standard distribution transformers - pole-mounted, pad-mounted units where the 0.90 spec meets efficiency requirements
• High-volume production - the 0.27mm gauge is more robust for automated cutting and stacking lines
• Stacked (laminated) cores - the higher stacking factor (≥0.96) maximizes active steel in the core window
• Transformers with annealing in the process - R-type coating tolerates stress-relief annealing

 

Choose B23R090 (0.23mm) When:

• You need actual loss below the 0.90 spec - the thinner gauge delivers 5–10% lower real-world core loss
• High-efficiency / eco-design transformers - Tier-1 energy efficiency, DOE efficiency, or EU eco-design compliance
• Large power transformers - where even small loss reductions translate to significant lifetime energy savings
• Wound (toroidal / rectangular) cores - thinner material winds more tightly and conforms better
• Low-noise transformers - thinner laminations reduce magnetostriction noise
• 60 Hz applications - eddy-current advantage of thinner gauge is greater at 60 Hz than at 50 Hz

 

From a magnetic specification standpoint, yes - both grades meet the same P1.7/50 ≤0.90 W/kg limit with the same B8 ≥1.88 T induction and the same R-type coating. A core designed for B27R090 will function with B23R090, and vice versa, provided the following are addressed:

• Stacking factor difference - switching from 0.27mm to 0.23mm reduces stacking factor by ~0.5–1%; the core cross-section or stack length must be adjusted to maintain the same flux density
• Lamination count changes - a 0.23mm core needs ~17% more laminations for the same stack height, increasing cutting and stacking time
• Tooling clearance - punching/shearing tools set for 0.27mm may need adjustment for 0.23mm to control burr
• Core weight- for the same core dimensions (OD/ID/height), the 0.23mm core will be slightly lighter due to lower stacking factor

 

For qualification / approval purposes, both grades fall under the same GB/T 2521, IEC 60404-8-7, and ASTM A876 frameworks, so a design qualified with one grade can typically be re-qualified with the other via a type test with minimal documentation change.

 

 

Grade	Thickness	Core Loss	Coating/Process	Relationship to This Comparison
B27R085	0.27mm	0.85 W/kg	R, non-scribed	Same thickness as B27R090, lower loss (premium)
B23R085	0.23mm	0.85 W/kg	R, non-scribed	Same thickness as B23R090, lower loss (premium)
B27P090	0.27mm	0.90 W/kg	P, laser scribed	Same spec as B27R090 but domain-refined (lower actual loss, not annealing-compatible)
B23P090	0.23mm	0.90 W/kg	P, laser scribed	Same spec as B23R090 but domain-refined
B30R090	0.30mm	0.90 W/kg	R, non-scribed	Thicker alternative - more economical but harder to achieve 0.90 at 0.30mm
27QG090	0.27mm	0.90 W/kg	QG (HiB)	HiB equivalent - higher magnetic induction

 

 

GNEE Steel supplies both B27R090 and B23R090 (and the full range of Baosteel, Wuhan Iron & Steel, and Shougang grain-oriented silicon steel grades) with mill test certificates, thickness and core-loss verification, and slitting / cut-to-length services.

 

Our engineers can help you:

• Compare actual mill certificate values between 0.27mm and 0.23mm gauges before you commit
• Cross-reference to ASTM / EN / JIS equivalent grades for your local standard
• Select the most cost-effective grade that meets your transformer efficiency target
• Arrange slitting to exact widths with controlled burr for your stacking line

 

 

The B27R090 vs B23R090 comparison distills to a cost-versus-performance trade-off within the same 0.90 W/kg specification class:

Criterion	Winner	Winner
Guaranteed core loss	Tie	Tie
Actual measured core loss		B23R090
Material cost	B27R090
Stacking factor	B27R090
Manufacturing robustness	B27R090
Wound core formability		B23R090
Low-noise performance		B23R090
60 Hz advantage		B23R090
Availability / lead time	B27R090
Annealing compatibility	Tie	Tie

 

For most standard distribution transformer projects, B27R090 offers the best balance of guaranteed performance, manufacturability, and cost. For high-efficiency, eco-design, large power, or 60 Hz applications where beating the 0.90 W/kg spec in practice matters, B23R090 justifies its premium with measurably lower actual core loss and superior high-frequency performance.

 

Are B27R090 and B23R090 the same grade with different thickness?

They share the same manufacturer (Baosteel), same core loss guarantee (0.90 W/kg), same coating type (R = high heat-resistant, non-scribed), and same magnetic induction class. The only specification difference is nominal thickness: 0.27 mm vs 0.23 mm. However, the thinner B23R090 typically achieves lower actual core loss in practice.

 

Is 0.23mm always better than 0.27mm?

Not always. While 0.23mm reduces eddy-current loss, it also reduces stacking factor, increases lamination count, raises material cost by ~8–15%, and is more sensitive to tooling and handling. For cost-driven designs where meeting 0.90 W/kg is sufficient, 0.27mm is the better choice. For efficiency-critical designs where you want to beat the spec, 0.23mm delivers a real performance advantage.

 

What does the "R" suffix mean, and does it matter for my application?

R = high heat-resistant insulation coating, non-laser scribed. This means the grade tolerates stress-relief annealing after cutting - a critical advantage if your core manufacturing process includes annealing. If you do not anneal and want lower loss, the P-variant (B27P090 / B23P090) with laser scribing offers additional domain-refinement loss reduction.

 

Can I mix B27R090 and B23R090 in the same transformer core?

It is not recommended. Mixing gauges in a stacked core creates uneven step-lap joints, inconsistent flux distribution, and varying lamination counts that complicate assembly. Choose one gauge per core design.

 

Which grade is better for 60 Hz transformers?

B23R090 (0.23mm) has a greater advantage at 60 Hz than at 50 Hz, because eddy-current loss increases with frequency, and the thinner gauge's eddy-current suppression is more valuable at higher frequency. For 60 Hz North American markets, the 0.23mm grade is generally preferred.

 

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Disclaimer: Values are typical for the grade classification and should be verified against the mill test certificate for each coil. Actual measured core loss may vary by heat number and production batch.