AOZHAN Stainless Steel Transformer Screws: Premium Solutions for High-Voltage Power Equipment

Key Takeaways​

Understanding Transformer Screw Applications and Requirements​

Critical Applications in Power Systems​

Transformer screws serve multiple critical functions in electrical infrastructure. In high-power transformers, these fasteners are essential for joining tank and cover assemblies, particularly in areas near low-voltage bushings where stray currents can create significant heat . Our research has shown that in a 420 MVA, 20/230 kV transformer, the screws near low-voltage bushings can experience severe overheating, with temperatures reaching up to 155°C .​

High-voltage applications demand screws that can withstand extreme electrical stress while maintaining mechanical integrity. AOZHAN transformer screws are designed to operate safely in systems rated up to 72kV, as verified by IEC 62271-1 testing ​. The electrical requirements for these applications include not only mechanical strength but also the ability to maintain low electrical resistance and prevent corona discharge.​

For outdoor installations, our stainless steel screws provide exceptional protection against environmental factors. The transformer housing materials we use, such as HCEP (High Creepage and Erosion Resistant Polymer), ensure highly reliable performance in outdoor wet or humid environments ​. Our grounding components are precision-engineered using high-conductivity bronze and copper alloys to ensure optimal electrical performance, corrosion resistance, and long-term durability in high-voltage outdoor environments ​.​

In control cabinet applications, our screws must meet specific environmental protection standards. We offer solutions compliant with NEMA Type 3R and IP32 ratings, featuring drip shield tops and seamless sides ​. The slip-on removable covers are fastened with captive plated steel screws along the bottom edge, providing easy access while maintaining environmental protection ​.​

Material Selection and Performance Criteria​

• SUS304 Stainless Steel (A2-70): This is our most versatile option, containing 18-20% chromium and 8-12% nickel ​. The A2-70 designation indicates a minimum tensile strength of 700 MPa . SUS304 provides excellent general corrosion resistance and is suitable for most indoor and outdoor applications where chloride exposure is minimal. It offers maximum chloride tolerance of approximately 200 ppm ​.​

• SUS316 Stainless Steel (A4-80): Our premium marine-grade option contains 16-18% chromium, 10-14% nickel, and 2-3% molybdenum ​. The addition of molybdenum provides superior resistance to chloride-induced pitting and crevice corrosion. The A4-80 designation indicates a minimum tensile strength of 800 MPa . SUS316 offers chloride tolerance up to 2000 ppm, making it ideal for coastal installations and chemical processing environments ​.​

• Both grades offer excellent mechanical properties, including minimum yield strength of 205 MPa and minimum elongation of 40% ​. The materials are non-magnetic in their annealed condition, which is important for applications where magnetic interference must be avoided ​.

  ​

Technical Specifications and Performance Data​

AOZHAN transformer screws are manufactured to precise technical specifications to ensure consistent performance and reliability. Our products comply with international standards including ISO 3506 and GB/T 3098.6 for stainless steel fasteners .​

The following table provides key technical specifications for our primary transformer screw products:​

Hot Spot Prevention and Thermal Management​

One of the most critical challenges in transformer screw design is preventing hot spots caused by stray currents. Research conducted on power transformers has shown that stray currents in structural elements near high-current bushings can create significant heat, leading to hot spots on the screws that join the tank and cover .​

AOZHAN has developed an innovative solution using copper sills to reduce these hot spots. In a case study of a 420 MVA transformer, our solution reduced maximum temperatures from 155°C to 80°C after installing copper sills in all cover screws . This represents a temperature reduction of nearly 50%, significantly improving the reliability and lifespan of the transformer.​

The solution involves using a copper sill as a conductor bridge between the tank and cover, combined with stainless steel screws (A-316), Belleville washers and flat washers made of anti-magnetic material, and stainless steel nuts . This combination ensures both electrical conductivity and mechanical strength while minimizing thermal effects.​

Installation and Torque Requirements​

Proper installation of transformer screws is essential for their long-term performance. AOZHAN provides detailed torque specifications based on international standards and material properties. Our screws must be tightened using torque wrenches according to design values, and when no specific torque is Regulation，industry standard values should be followed .​

The following table provides recommended torque values for our transformer screws:​

For electrical connections, we recommend torque values of 250-350 lb-in (28-40 N·m) for larger connections and 50-75 lb-in (6-8 N·m) for 1/4" screws ​. It's important to note that actual torque values must be adjusted based on bolt performance class, surface condition, and washer type .​

Environmental Considerations and Protection​

Transformer screws in outdoor applications must withstand harsh environmental conditions. AOZHAN's stainless steel screws are designed to provide exceptional resistance to corrosion, UV radiation, and temperature variations. Our marine-grade SUS316 screws have passed 500-hour salt spray tests (ASTM B117 compliant) and meet vibration endurance requirements according to IEC 60068-2 standards .​

For high-humidity environments, our transformer housing materials ensure reliable performance with adequate creepage distances to meet customer requirements ​. The materials we use provide protection against moisture ingress, chemical exposure, and extreme temperature fluctuations.​

Quality Standards and Certifications​

For transformer applications, our products are designed to meet the requirements of EN 61558 series for low-voltage transformers and EN 60076 series for medium and large power transformers ​. We work with approved notified bodies such as TÜV and CESI to ensure our products meet all necessary safety and performance requirements ​.​

FAQ Section​

1. What material grades does AOZHAN offer for transformer screws?​

AOZHAN provides two primary stainless steel grades for transformer applications: SUS304 (A2-70) and SUS316 (A4-80) ​. SUS304 contains 18-20% chromium and 8-12% nickel, offering excellent general corrosion resistance suitable for most environments. SUS316 contains 16-18% chromium, 10-14% nickel, and 2-3% molybdenum, providing superior resistance to chloride-induced corrosion for marine and high-salinity applications ​.​

2. What certifications do AOZHAN transformer screws have?​

Our transformer screws meet multiple international certifications including CE Mark (compliant with Low Voltage Directive 2014/35/EU and EMC Directive 2014/30/EU), IEC 61558 series for small transformers, IEC 60076 series for power transformers, UL 506, and CSA C22.2 standards ​. We are also RoHS compliant and hold ISO 9001:2015 certification for our quality management system ​.​

3. How do I choose the right screw for my transformer application?​

The selection depends on several factors:​

• Environmental conditions: Use SUS304 for general environments and SUS316 for marine or high-chloride environments​
• Voltage rating: Our screws are suitable for applications up to 72kV ​​
• Current requirements: Consider the electrical load and ensure adequate conductor size​
• Temperature range: Both grades perform well in typical transformer operating temperatures​
• Corrosion resistance needs: Evaluate exposure to salt, chemicals, or moisture​

4. What torque values should I use for installation?​

Torque values vary by thread size and material:​

• M6: 13 N·m (SUS304) / 15 N·m (SUS316)​
• M8: 32 N·m (SUS304) / 37 N·m (SUS316)​
• M10: 65 N·m (SUS304) / 74 N·m (SUS316)​
• M12: 110 N·m (SUS304) / 130 N·m (SUS316)​

Always use a torque wrench and follow manufacturer specifications . Actual torque may need adjustment based on surface condition and washer type.​

5. Can AOZHAN provide custom transformer screw solutions?​

Yes! AOZHAN specializes in OEM and ODM services . We can develop and manufacture screws according to customer drawings or specific requirements. Our capabilities include:​

• Custom thread sizes and pitches​
• Special surface treatments​
• Unique head styles and drive systems​
• Material modifications for specific applications​
• Pre-assembled solutions with washers and nuts​

Contact our engineering team to discuss your specific transformer screw requirements, and we'll provide a tailored solution to meet your needs.​

For over a decade, AOZHAN has been committed to providing the highest quality stainless steel fasteners for electrical applications. Our transformer screws combine superior materials, precision engineering, and rigorous quality control to deliver reliable performance in even the most demanding environments. Whether you're working on a small distribution transformer or a large power substation, AOZHAN has the right solution for your fastening needs.​