1. Product Overview
Zhongxin Steel supplies premium-grade M4 Grain Oriented Electrical Steel (GOES), a professional silicon steel material tailor-made for power transformer cores. Featuring a nominal thickness of 0.28 mm and maximum core loss of 0.89 W/kg under 1.7 T / 50 Hz working condition, this steel grade delivers stable magnetic performance and excellent dimensional consistency. It is widely applicable for manufacturing large power transformers, distribution transformers and wound core products all over the world.
- Custom Service: OEM / ODM orders & full-spec customization available
- Manufacturer: Zhongxin Steel
- Brand: Zhongxin Steel
2. Core Manufacturing Principle & Key Properties
2.1 Production Process & Magnetic Mechanism
M4 GOES is manufactured complying with IEC 60404-8-7 and ASTM A876 standards. It owns unique Goss texture with highly aligned internal grain structure, where most crystals are arranged along the rolling direction.
The complete production process includes: hot rolling → cold rolling (reduction rate ≥ 70%) → decarburization annealing → high-temperature final annealing (above 1100 °C, dry N₂/H₂ mixed protective atmosphere). The highly oriented grain structure endows M4 steel with high magnetic permeability and low rolling-direction core loss, making it the mainstream cost-effective material for medium and high-efficiency transformers.
2.2 Basic Physical & Magnetic Parameters
| Parameter | M4 Value | Remarks |
|---|---|---|
| Nominal Thickness | 0.28 mm | Conventional GOES standard gauge |
| Max Core Loss (1.7 T, 50 Hz) | 0.89 W/kg | Tested per IEC 60404-8-7 |
| Min Magnetic Flux Density B800 | 1.78 T | Magnetic field strength: H = 800 A/m |
| Silicon Content | 2.9 – 3.3 % | Iron-silicon alloy substrate |
| Surface Coating | S2 / C2 | Insulation coating with stress relief function |
| Density | 7.65 g/cm³ | Standard density for grain-oriented electrical steel |
| Yield Strength | 300 – 380 MPa | Tested along rolling direction |
| Resistivity | 47 – 50 μOhm·cm | Effectively suppresses eddy current loss |
3. Advantages of 0.28mm Thickness
Eddy current loss is positively correlated with steel sheet thickness. Thinner gauge can cut down eddy current loss significantly:
- 50 Hz working condition: Replacing 0.35mm M6 steel with 0.28mm M4 steel reduces eddy current loss by around 20%, greatly improving overall transformer energy efficiency.
- 60 Hz working condition: The loss reduction effect is more prominent. 0.28mm M4 steel maintains controllable core loss, avoiding overheating risk caused by thicker electrical steel sheets.
4. Grade Comparison with Other GOES
| Steel Grade | Thickness (mm) | Max Core Loss (W/kg, 1.7 T / 50 Hz) | Typical Application Scenarios |
|---|---|---|---|
| M3 | 0.23 | 0.80 | Ultra-high efficiency large power transformers |
| M4 | 0.28 | 0.89 | Large power transformers & distribution transformers |
| M5 | 0.30 | 0.97 | Conventional distribution transformers |
| M6 | 0.35 | 1.11 | General-purpose common transformers |
Core Advantage of M4 Grade: It balances low core loss and manufacturing cost perfectly. Compared with M5/M6, its no-load loss is reduced by 10%-20%; meanwhile, it has obvious price advantages over high-end M3 and Hi-B grades (23ZDMH, 27ZDMH). It is the most cost-effective option for transformer manufacturers requiring ≥98% efficiency without excessive material cost.
5. Dual-Layer Insulation Coating System
All M4 GOES products adopt dual-layer composite coating, which provides electrical insulation, optimizes magnetic domain structure and further reduces core loss by 5%-8% compared with uncoated steel.
5.1 Substrate Forsterite Base Coating
Magnesium silicate (Mg₂SiO₄) glass film formed during high-temperature annealing:
- Provides basic inter-lamination insulation performance
- Applies surface tensile stress to refine internal magnetic domains
- Serves as adhesion base for outer surface coating
5.2 Optional Top Coating (S2 / C2)
- S2 Coating: Phosphate-based coating mixed with colloidal silica. Insulation resistance ≥5 Ohm·cm², excellent stamping lubricity and heat resistance, compatible with stress-relief annealing below 800 °C. Universal type for global markets.
- C2 Coating: Chromium-free eco-friendly insulation coating, fully compliant with RoHS and REACH standards. Suitable for EU and environmentally restricted export markets. Slightly lower insulation resistance than S2 but meets all conventional transformer production demands.
6. International Standards Compliance
Our M4 grain oriented electrical steel is manufactured following full international standards, supporting third-party official inspection and global market clearance:
- IEC 60404-8-7: Fully processed cold-rolled grain-oriented electrical steel strip and sheet
- ASTM A876: Fully processed flat-rolled grain-oriented silicon-iron electrical steel
- EN 10107: Fully processed grain-oriented electrical steel strip and sheet
- JIS C 2553: Grain-oriented magnetic steel sheet and strip
Third-party inspection reports including SGS, BV, TUV can be provided upon customer request.
7. Complete Technical Specifications
7.1 Dimension & Tolerance
| Dimension Item | Range | Tolerance |
|---|---|---|
| Nominal Thickness | 0.28 mm | ±0.02 mm |
| Original Coil Width | 900 – 1250 mm | ±0.5 mm |
| Custom Slit Width | 8 – 600 mm | ±0.1 mm |
| Coil Inner Diameter | 508 mm / 610 mm | Industry standard size |
| Single Coil Weight | 3 – 10 tons | Customizable as required |
7.2 Guaranteed & Typical Magnetic Properties
| Magnetic Property | Typical Value | Guaranteed Minimum/Maximum Value |
|---|---|---|
| Core Loss P1.7/50 (W/kg) | 0.85 | ≤ 0.89 |
| Core Loss P1.5/50 (W/kg) | 0.60 | ≤ 0.64 |
| Flux Density B800 (T) | 1.82 | ≥ 1.78 |
| Flux Density B1000 (T) | 1.88 | ≥ 1.85 |
| Lamination Factor (%) | 97.5 | ≥ 96.5 |
7.3 Surface & Flatness Quality Standard
- Surface Finish: Bright surface, no rust, oil stains, holes, scratches or roller marks
- Slit Edge Quality: Smooth cutting edge, no burrs and edge waviness
- Flatness: ≤ 3 mm / 1000 mm (steel coil); ≤ 2 mm / 1000 mm (cut sheet)
8. Deep Processing One-Stop Services
Beyond raw steel coil supply, Zhongxin Steel provides full-process deep processing to deliver finished/semi-finished products directly for transformer assembly:
- Precision Slitting: Custom width slitting from 30mm to 600mm, width tolerance ±0.1mm. Burr-free cutting edge without any coating damage.
- Cut-to-Length Shearing: Custom fixed-size sheets with length tolerance ±0.5mm, perfectly matching step-lap core production.
- Finished Wound Core Fabrication: Custom step-lap cores and conventional wound cores, finished with annealing and full performance test, ready for direct assembly.
- Surface Secondary Treatment: Insulation coating reinforcement, stress-relief annealing (max 800 °C under protective atmosphere), surface protective film lamination.
9. Main Application Fields
M4 GOES is designed for 50/60Hz power frequency electromagnetic equipment requiring low no-load loss, low operation noise and stable thermal performance:
- 110kV+ Large Power Transformers: Stably works under 1.6-1.75T rated flux density, supporting transformer efficiency over 99% for power grid transmission projects
- 10-35kV Distribution Transformers: The most mainstream material for distribution transformers, effectively cutting no-load loss and reducing overall operation cost
- Wound Core Transformers: Alternative to amorphous alloy materials, reducing no-load loss by over 50% compared with traditional stacked cores
- Instrument & Current Transformers: Stable permeability and low excitation current ensure accurate metering and reliable system protection
- Shunt Reactors: Controlled air gap design provides stable inductance and low vibration for EHV power compensation equipment
- Power Generator Stator Cores: Applicable for stator lamination of large turbo generators and hydroelectric generators
10. Why Choose Zhongxin Steel
10.1 Factory Production Capacity
Zhongxin Steel professional GOES processing base is located in Wuxi, Jiangsu Province, equipped with full-automatic slitting machines, high-precision annealing furnaces and intelligent coating production lines. Monthly output capacity reaches 8,000 tons for grain-oriented electrical steel coils and processed finished products.
10.2 Complete Quality Certification & Testing System
- System Certification: ISO 9001 / ISO 14001 / ISO 45001
- In-house Lab Equipment: Epstein frame tester, single-sheet tester, coating resistance tester, surface roughness tester
- Full Lifespan Traceability: Each steel coil can be tracked from raw steel smelting to final shipment
10.3 Core Competitive Advantages
- Stable Magnetic Performance: Precise control on silicon content and Goss texture ensures all products meet international standard requirements
- High-precision Processing: Strict ±0.1mm width tolerance, no coating peeling, no secondary processing needed for stamping production
- Competitive Price: Integrated industrial chain eliminates middleman cost. Reference price: USD 1200 – 1800 / ton (varies by specification, coating type and order quantity)
- Flexible MOQ: Standard order starts from 5 tons; small trial orders are negotiable
- Global Delivery Experience: Products exported to more than 80 countries across Southeast Asia, Middle East, South America, Europe and Africa. Standard seaworthy export packaging with complete moisture-proof and anti-rust protection
- Full Lifecycle Service: One-stop support including material selection consultation, production, deep processing, logistics and after-sales service
11. Customer Common FAQ
- Q: What is the gap between M4 and Hi-B (M0H/M1H) steel? A: Hi-B steel adopts optimized Goss texture plus laser/mechanical domain refinement technology, with 15%-25% lower core loss than M4. But its unit cost is 30%-50% higher. M4 is still the best cost-performance choice for conventional power and distribution transformers.
- Q: Can M4 steel be used under 60Hz working frequency? A: Yes. Core loss will rise by 20%-30% under 60Hz, with typical P1.7/60 loss at 1.15 W/kg. We can provide exclusive 60Hz test reports for North America, Saudi Arabia and Philippine markets.
- Q: How to choose between S2 and C2 coating? A: S2 is universal standard coating with better insulation and stamping performance for most global markets. C2 is chromium-free eco-friendly coating for EU and green regulation markets with RoHS/REACH compliance.
- Q: Is free sample available? A: Yes. We offer free A4-size sheet samples and 1-2m small coil samples for magnetic and stamping performance testing.
- Q: What is the minimum order quantity? A: Standard M4 coils: 5 tons. Custom processing or special coating orders: negotiable. Support trial order with one single coil.
- Q: How to guarantee coating integrity after slitting? A: We adopt carbide precision slitting knives and constant tension control system, plus full edge deburring process. 100% full inspection after slitting to avoid coating peeling and burrs.
- Q: What is the production lead time? A: Standard coils: 15-30 working days; Custom processed products: 20-45 working days; In-stock goods: 7-10 working days.
- Q: Information needed for official quotation? A: Please provide: Steel grade, thickness & width, coating type, order quantity, destination port & trade term (FOB/CIF/EXW), other special requirements (laser scribing, annealing, customized packaging).
Contact Us
M4 Grain Oriented Electrical Steel — Reliable & Cost-Effective Core Material for High-efficiency Transformers. Welcome to contact Zhongxin Steel for detailed datasheets, free samples and competitive quotation anytime.