GUANGZHOU FAITH · Technical Solutions
Overcoming the challenge of stacking ultra-thin silicon steel sheets
FS7360R Supports Localization of Self-Adhesive Coatings for Silicon Steel
面向新能源汽车高速、油冷电机与超薄硅钢片应用，广州飞思提供兼顾绝缘、粘接与规模化制造的水性环氧自粘涂层解决方案。
What limitations do traditional core connection processes face?
Silicon steel sheets are widely used in motor and transformer cores. To reduce interlaminar eddy current losses and improve anti-rust, corrosion resistance, and insulation properties, the surface of silicon steel sheets is typically coated with an insulating layer.
Traditional iron core manufacturing generally involves two main stages:
Pre-coat electrical steel with insulating coating and bake to form film
Stamp silicon steel sheets, then stack and secure them into a stator or rotor core using welding, riveting, bolting, or other mechanical methods.
This mature, widely adopted process is showing its limitations as silicon steel sheets become thinner and motor speeds increase.
Welding creates localized heat-affected zones that can cause edge conduction in the core, degrade interlaminar insulation, and affect magnetic properties. Welds may also lead to local deformation, stress concentration, and challenges in maintaining consistency.
Riveting creates connection points on silicon steel sheets, consuming effective magnetic circuit space. For ultra-thin silicon steel sheets as thin as 0.20 mm or even 0.15 mm, the design and manufacturing complexity of the riveted structure increases significantly.
More critically, both welding and riveting are localized connections. When the rotor operates at high speeds above 20000 rpm, the core must withstand increased centrifugal loads while facing combined challenges such as vibration, noise, thermal cycling, and long-term reliability. Localized connection methods face greater demands in terms of structural uniformity and overall fixation stability.
Self-bonding process: transforms the insulating coating into a structural bonding layer.
The approach to self-bonding silicon steel involves pre-coating the surface of silicon steel sheets with a special coating that provides both insulation and adhesion. Through pre-curing and post-curing processes, the stamped sheets achieve integrated inter-sheet bonding.
Pre-coating and Pre-curing
Apply a water-based epoxy self-adhesive coating to the surface of silicon steel sheets via roller coating, then bake at high temperature for a short duration to achieve a pre-cured state suitable for transport, storage, and stamping.
Reference Pre-curing Conditions:180～220°C, approximately 1 minutes. Actual temperature and time must be verified based on coating thickness, steel plate specifications, and production line conditions.
Layering and Full Curing
After stamping, the pre-coated silicon steel sheets are stacked in a fixture under specified pressure. The self-adhesive coating is then fully cured via baking to form a solid core.
参考后固化条件：200～230°C, approximately 2～3 hours. When using suitable high-frequency electromagnetic heating processes, the curing cycle time may be further reduced, but verification is still required based on core dimensions, equipment capabilities, and target performance.
Why Self-Bonded Cores Are Better for High-Performance Motors
After curing, the self-adhesive coating forms a continuous and uniform bonding interface between silicon steel sheets. Compared to localized welding or riveting, a well-designed self-bonded structure offers the following potential advantages:
减少对磁路和片间绝缘的局部破坏：Self-bonding processes eliminate the need for riveted points on the core, reduce the heat-affected zone during welding, and help preserve the original interlaminar insulation and magnetic circuit integrity of the silicon steel sheets.
Enhance core integrity:Interlaminar bonding ensures more uniform load distribution, enhancing the core's structural stability, geometric accuracy, and reliability at high speeds.
Improve vibration and noise performance:The continuous bonding layer constrains the silicon steel sheets and provides cushioning, helping to reduce inter-laminar loosening and high-frequency vibration. This establishes a technical foundation for improving motor NVH performance.
Supports thinner silicon steel sheets:Thinner silicon steel sheets make traditional punch-and-rivet assembly increasingly difficult, while welding raises concerns about localized conductivity and heat-affected zones. Self-bonding technology, which eliminates the need for rivet points, is better suited for assembling ultra-thin silicon steel stacks.
Maximize effective space utilization:Subject to structural design requirements, self-bonding processes can reduce end plates, retaining rings, and certain fastening components, creating space for increased effective core length and optimized motor architecture.
根据广州飞思在部分风力发电机自粘结铁芯项目中的应用经验，与传统连接方案相比，相关样机曾观察到振动和噪声改善、扭矩及效率提升、温升下降等效果。
FS7360R: Developed for oil-cooled motors in new energy vehicles
Building on its accumulated experience with self-bonding laminations for wind turbine generators, Guangzhou Feisi developed FS7360R, a water-based epoxy self-adhesive coating specifically designed for new energy vehicle motor laminations.
This product holds a Chinese invention patent, No. ZL202211414419.2, primarily designed for self-bonding applications in new energy vehicle motor cores and compatible with oil-cooled motor technology routes.
The FS7360R utilizes a waterborne epoxy system and can be applied to silicon steel sheets via roll coating. After pre-curing, the coating must withstand subsequent transportation, storage, and stamping processes. Upon stacking, pressing, and heating of the stamped laminations, the coating fully cures to bond the individual silicon steel sheets together.
To meet the manufacturing needs of new energy vehicle drive motors, FS7360R focuses on the following areas:
Insulation and Interlaminar Bonding of Ultra-Thin Silicon Steel Sheets
Integrated structural design of high-speed stator and rotor cores
Material Compatibility in Oil-Cooled Motor Environments
Reduction or replacement of welding and riveting processes
Localization of self-bonding silicon steel coatings
Two import methods to support different manufacturing systems
FS7360R can be introduced into production using different methods tailored to the customer's supply chain and manufacturing capabilities.
Steel mill or professional pre-coated line
Silicon steel sheets are coated and pre-cured by steel mills or specialized coating companies, then stamped into shape by stamping plants, and finally stacked, cured, and assembled into complete motors by motor manufacturers. This approach supports the establishment of a standardized coil coating system and large-scale supply chain.
客户自建涂覆线
Customers with the necessary equipment and process capabilities can independently perform silicon steel sheet coating, pre-curing, stamping, stacking, and post-curing to establish an in-house closed-loop manufacturing process. This approach allows customers to adjust coating thickness, pre-cure levels, and post-curing processes according to their product designs, but it requires higher standards for equipment, process control, and quality management.
From domestic materials to complete process solutions
New energy vehicle motors are evolving toward higher speeds, greater power density, lower losses, and reduced noise. While ultra-thin silicon steel addresses some core loss issues, it has introduced new challenges in stacking, connection, and mass manufacturing for the industry.
Self-bonding cores offer a new solution to this problem.
Guangzhou Feisi promotes the localization of self-adhesive materials for motor silicon steel in new energy vehicles through its FS7360R water-based epoxy self-adhesive coating, offering customers a viable alternative to reduce reliance on imported materials. Beyond supplying coatings, Guangzhou Feisi also supports process validation across key stages including coating application, pre-curing, stamping, stacking, and post-curing.
The value of domestic material localization isn't just about finding a replacement. It's about making critical materials verifiable, iteratable, and scalable for supply—ultimately integrating them into a stable manufacturing system.
This is the real challenge that silicon steel self-adhesive coatings need to solve.
广州飞思 · 技术咨询
Guangzhou Feisi Synthetic Materials Co., Ltd. specializes in the R&D and production of waterborne epoxy insulating resins, waterborne silicon steel self-adhesive coatings, and amorphous strip composite adhesives.
Providing bonding and insulation solutions for the new energy vehicle motor, industrial motor, transformer, and amorphous magnetic materials industries.
Hotline: 020-82793066
Water-based Paint Business: Engineer Liu 15920494556
Thiol Business: Engineer Zhang 13609004936