Electrical Steel Sheet Coating for Heat-Resistant Low-Stress Lamination
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Solution Overview
Problem
Existing methods for joining electrical steel sheets in laminated cores, such as swaging or welding, lead to deterioration of magnetic characteristics due to mechanical or thermal strain, while adhesives like epoxy resins, although heat-resistant, impart stress and are hard, making it difficult to achieve both excellent magnetic characteristics and heat resistance.
Innovation Solution
A coating composition for electrical steel sheets using a combination of an epoxy resin with a phenolic resin having an alkyl or alkoxy group as a curing agent, which provides both adhesive strength and heat resistance, even at high temperatures, by balancing the epoxy resin's hardness with the phenolic resin's flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If epoxy resin is used as adhesive for joining electrical steel sheets, then heat resistance and adhesion strength are improved, but stress strain is imparted to steel sheets causing iron loss deterioration
Solution Approach 1:
The patent modifies the chemical composition parameters of the adhesive by incorporating specific rubber components (polybutadiene or styrene-butadiene rubber) alongside epoxy resin. This changes the physical properties of the cured adhesive, reducing its hardness and elasticity modulus while maintaining heat resistance, thereby reducing stress strain on the steel sheets.
Solution Approach 2:
The patent creates a composite adhesive material combining epoxy resin with rubber components (polybutadiene or styrene-butadiene rubber). This composite structure integrates the heat resistance and adhesion strength of epoxy resin with the flexibility and stress-absorbing properties of rubber, resolving the contradiction between heat resistance and stress-induced iron loss.
2Loss of energy
If sheet thickness is decreased to reduce core iron loss, then core iron loss is reduced, but Young's modulus decreases making steel sheet more susceptible to stress strain
Solution Approach 1:
The patent changes the mechanical parameters of the adhesive by incorporating rubber components, reducing the adhesive's elasticity modulus to match the reduced Young's modulus of thinner steel sheets. This parameter matching prevents stress strain transmission to the thin sheets, allowing iron loss reduction through thickness decrease without compromising structural integrity.
3Temperature
If phenolic resin is blended to improve heat resistance, then heat resistance is improved, but resin becomes hard at normal temperature imparting large stress to laminated cores
Solution Approach 1:
The patent creates a composite adhesive system combining phenolic resin with rubber components. This composite structure allows the phenolic resin to provide heat resistance while the rubber components maintain flexibility at normal temperatures, preventing the hardness and excessive stress associated with pure phenolic resin.
Solution Approach 2:
The patent modifies the temperature-dependent physical parameters of the adhesive by incorporating rubber. This creates a material with appropriate hardness at normal temperatures (reducing stress) while maintaining heat resistance at elevated temperatures, effectively decoupling the temperature-performance relationship.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The coating composition maintains excellent magnetic characteristics and heat resistance, ensuring adhesion strength between electrical steel sheets even under high-temperature conditions, thereby improving the performance of laminated cores and rotary electric machines.
Implementation Method 1
a coating composition for an electrical steel sheet, an electrical steel sheet, a laminated core and a rotary electric machine... a method in which electrical steel sheets each having an insulating coating with an adhesive capability formed on a surface are caused to adhere together
Implementation Method 2
insulating coating... excellent in terms of heat resistance
Data Source
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AI summary
An electrical steel sheet that is used for laminated cores is an electrical steel sheet having an insulating coating 3 formed by applying a coating composition for an electrical steel sheet on a surface of a base material steel sheet 2, and, in the coating composition for an electrical steel sheet, an epoxy resin, a first curing agent composed of a phenolic resin including a phenol skeleton having any one or both of an alkyl group and an alkoxy group and a second curing agent of one or more selected from the group consisting of a phenolic resole resin and a phenolic novolac resin are blended at specific fractions.