Selecting the correct silicon steel (electrical steel) grade directly affects core loss, temperature rise, energy efficiency class, and total lifecycle cost of motors, transformers, and inductors. With multiple variables – non-oriented vs. grain-oriented, thickness, coating, core loss values – a systematic selection method is essential.
Wuxi Zhongxin Special Steel Co., Ltd. has over ten years of experience in silicon steel supply and technical support, serving global motor and transformer manufacturers with grade recommendation, sample testing, and batch delivery. This article, based on real application data, outlines the key parameters, common grade comparisons, and typical pitfalls to avoid.
1. Two Major Categories: Non-Oriented vs. Grain-Oriented Silicon Steel
| Type | Magnetic Directionality | Typical Applications | Example Grades |
|---|---|---|---|
| Non-oriented Silicon Steel (NGO) | Isotropic, uniform in-plane properties | AC motors, servo motors, EV traction motors, generators | 50W800, 35W270 |
| Grain oriented silicon steel (GO) | High permeability along rolling direction, anisotropic | Power transformers, distribution transformers, reactor cores | 23Q110, 27QG100 |
Silicon steel is typically identified by a grade code. For example, “50W800” indicates a thickness of 0.50 mm and a core loss P₁₅/₅₀ ≤ 8.0 W/kg (non-oriented). “23Q110” indicates 0.23 mm thickness and core loss P₁₇/₅₀ ≤ 1.10 W/kg (grain-oriented).
2. Five Key Technical Parameters
When evaluating silicon steel grades, manufacturers should focus on the following specifications:
– Core Loss (P₁₅/₅₀ or P₁₇/₅₀)
Unit: W/kg. Lower values mean less heat generation and higher efficiency. Motors typically use P₁₅/₅₀ (1.5 T, 50 Hz); transformers use P₁₇/₅₀ (1.7 T, 50 Hz).
– Magnetic Flux Density (B₅₀)
Magnetic induction at 5000 A/m (T). Higher B₅₀ allows a smaller core cross-section for the same power, reducing copper usage.
– Thickness
0.50 mm, 0.35 mm, 0.27 mm, 0.23 mm, 0.20 mm, etc. Thinner gauges reduce eddy current losses at higher frequencies, but decrease stacking factor and increase processing cost.
– Insulation Coating
C2 (organic): good punchability for small/medium motors. C3 (semi-organic): excellent weldability. C5 (inorganic): high temperature resistance, suitable for annealing.
– Mechanical Properties & Punchability
Grades with high silicon content (>3%) are harder and more brittle, accelerating die wear. For high-volume stamping, the balance between die life and material cost must be evaluated.
3. Four-Step Grade Selection Process
Step 1: Identify device type
- Rotating machine → Non-oriented Silicon Steel(NGO)
- Static transformer / reactor → Grain-oriented Silicon Steel (GO)
Step 2: Determine operating frequency
- 50/60 Hz: Standard thickness 0.35–0.65 mm sufficient
- 400 Hz (aerospace, military): Recommend 0.20–0.35 mm thin NGO
- Above 10 kHz (SMPS inductors): Requires 0.10–0.18 mm ultra-thin NGO or amorphous material
Step 3: Set target efficiency class
Select grade according to GB 18613-2020, IE2/IE3/IE4, or DOE standards. Example: upgrading a 7.5 kW motor from IE2 to IE4 reduces core loss by ~40%, typically requiring a jump from 50W1300 to 35W270 or higher.
Step 4: Balance cost and performance
Lower core loss grades cost 30–100% more due to higher silicon content and precision rolling. Evaluate total cost of ownership (TCO) over 10 years: energy savings, reduced temperature rise (enabling smaller cooling design), and weight reduction versus material premium.
4. Common Non-Oriented (NGO) Grades Comparison for Motors
The following non-oriented grades are available from Wuxi Zhongxin Special Steel Co., Ltd. , all conforming to GB/T 2521-2017 or IEC 60404-8-4.
| Grade | Thickness (mm) | Core Loss P₁₅/₅₀ (W/kg) | B₅₀ (T) | Stacking Factor (%) | Typical Motor Application | Efficiency Reference |
|---|---|---|---|---|---|---|
| 50W1300 | 0.50 | ≤13.0 | ≥1.69 | 97 | Fans, pumps, low-cost motors | IE1 |
| 50W800 | 0.50 | ≤8.0 | ≥1.72 | 97.5 | General industrial motors | IE2 |
| 50W600 | 0.50 | ≤6.0 | ≥1.73 | 97.5 | High-efficiency motors | IE3 |
| 35W440 | 0.35 | ≤4.4 | ≥1.66 | 96 | Servo motors, compressors | IE3/IE4 |
| 35W270 | 0.35 | ≤2.7 | ≥1.62 | 96 | EV traction motors | IE4 |
| 27W160 | 0.27 | ≤1.6 | ≥1.57 | 95.5 | High-speed spindles, 400 Hz motors | High-frequency |
Note: Core loss values shown are maximums. Actual values per heat are provided with each coil certificate.
5. Common Grain-Oriented (GO) Grades Comparison for Transformers
| Grade | Thickness (mm) | Core Loss P₁₇/₅₀ (W/kg) | B₈₀₀ (T) | Domain Refinement | Typical Application |
|---|---|---|---|---|---|
| 23Q120 | 0.23 | ≤1.20 | ≥1.88 | No | Distribution transformers |
| 23QG100 | 0.23 | ≤1.00 | ≥1.92 | Laser-scribed | Premium efficiency transformers |
| 27Q110 | 0.27 | ≤1.10 | ≥1.87 | No | Power transformers |
| 30Q120 | 0.30 | ≤1.20 | ≥1.85 | No | Large power transformers |
| 20RK85 | 0.20 | ≤0.85 | ≥1.94 | Yes | Ultra-high efficiency, amorphous replacement |
6. Application Case: Pump Motor Manufacturer Cuts Cost and Losses
A pump manufacturer was using 50W1300 laminations in a 7.5 kW IE2 motor. Full-load temperature rise reached 95K, requiring an additional cooling fan.Wuxi Zhongxin Special Steel Co., Ltd. recommended switching to50W800 (same 0.50 mm thickness, core loss reduced from 13 to 8 W/kg). Results:
- Motor temperature rise dropped by 15K, external fan eliminated
- Efficiency increased by 2.3 percentage points, saving ~1100 kWh per year (6,000 operating hours)
- Die life remained essentially unchanged
The customer upgraded the entire IE2 production line to 50W800, achieving annual comprehensive savings of over RMB 120,000.
7. Common Mistakes in Silicon Steel Selection
| Mistake | Consequence | Correct Approach |
|---|---|---|
| Using grain-oriented steel in a motor | High torque ripple, unpredictable core loss | Always use non-oriented for rotating machines |
| Ignoring stacking factor | Reduced effective flux area, actual B lower than design | For thin grades (≤0.35 mm), increase stack length by 2–3% |
| Semi-processed grade without annealing | Core loss 30%+ higher than nominal value | Confirm grade type: fully processed (ready to use) vs. semi-processed (needs annealing) |
| Over-specifying thin gauge for low frequency | Significant cost increase with negligible performance gain | For 50 Hz transformers, 0.27 mm is sufficient; below 0.23 mm rarely needed |
8. Why Choose Wuxi Zhongxin Special Steel Co., Ltd.?
- Reliable sources: Stable supply of silicon steel coils from major mills including Baowu, Shougang, Tisco, Nippon Steel, and ThyssenKrupp, with traceable mill certificates.
- Processing capability: In-house precision slitting and shearing lines, width tolerance ±0.1 mm, custom lamination dimensions available.
- Flexible MOQs: Trial orders from 500 kg, batch orders from 25 tons/container, mixed grades allowed.
- Technical support: Assistance with core loss simulation, stacking factor testing, and alternative grade validation.
Our Wuxi warehouse stocks over 30 grades of silicon steel for just-in-time delivery, with 72-hour shipment to major cities in the Yangtze River Delta.
9. Quick Selection Guide (Decision Tree)
10. Pre-Order Checklist
Before placing a production order, confirm the following items (our sales engineers can assist):
- ☐ Rated frequency and PWM carrier frequency of motor/transformer
- ☐ Target efficiency class (specific standard: GB, IEC, DOE, etc.)
- ☐ Stamping process and annealing capability (annealing furnace available or not)
- ☐ Design stacking factor vs. achievable value
- ☐ Sample coil testing (200–500 kg) completed
If any uncertainties remain, Wuxi Zhongxin Special Steel Co., Ltd. offers a free grade matching consultation. Provide your stator/rotor drawings or transformer specifications, and we will issue a Silicon Steel Grade Recommendation Report and sample quote within two working days.
Always validate with a sample coil before production. We support trial orders with full magnetic property test reports to ensure correct grade selection before mass production.
Technical Data Request
For a complete Silicon Steel Grade Parameter Sheet or a project-specific grade recommendation, please contact the technical department of Wuxi Zhongxin Special Steel Co., Ltd. We are committed to helping customers maximize motor/transformer efficiency at a reasonable cost.