Electrical Steel Sheet Coating for Heat-Resistant Core Bonding
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Solution Overview
Problem
Existing methods for joining electrical steel sheets in laminated cores, such as caulking or welding, lead to deterioration of magnetic properties due to thermal and mechanical strains, while adhesion using insulation coatings with epoxy resins results in stress strains and reduced Young's modulus, making it difficult to achieve both low core iron loss and high-temperature adhesion strength.
Innovation Solution
A coating composition for electrical steel sheets combining an epoxy resin, an epoxy resin curing agent, and an elastomer-modified phenolic resin is applied to ensure adhesion strength and heat resistance, using a specific ratio and curing process to maintain magnetic properties even at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If epoxy resin is used for adhesion, then adhesion strength is improved, but stress strain is applied to steel sheet causing deterioration in magnetic property
Solution Approach 1:
The patent modifies the chemical composition parameters of the resin by incorporating specific ratios of phenolic resin (5-20 parts by mass) and polyester resin (5-20 parts by mass) relative to epoxy resin (100 parts by mass). This compositional parameter change reduces the resin's hardness and curing shrinkage, thereby reducing stress strain on the steel sheet while maintaining adhesion strength.
Solution Approach 2:
The patent creates a composite resin material by combining epoxy resin with phenolic resin and polyester resin. This composite formulation leverages the complementary properties of each resin type: epoxy provides adhesion strength, while phenolic and polyester resins reduce hardness and curing shrinkage, collectively reducing stress strain on the steel sheet.
2Temperature
If phenol resins are incorporated to improve heat resistance, then heat resistance is improved, but resin becomes hard at normal temperature applying large stress to laminated core
Solution Approach 1:
The patent controls the proportion of phenolic resin within a specific range (5-20 parts by mass per 100 parts epoxy resin) and combines it with polyester resin. This parameter optimization ensures the resin maintains appropriate hardness at normal temperature while achieving sufficient heat resistance through the synergistic effect of the resin combination.
Solution Approach 2:
The patent formulates a composite resin system where phenolic resin contributes heat resistance and polyester resin contributes flexibility and reduced hardness. The combination creates a balanced material that exhibits both heat resistance and appropriate softness at normal temperature, avoiding excessive stress on the laminated core.
3Loss of energy
If steel sheet thickness is reduced to improve motor efficiency, then core iron loss is reduced, but Young's modulus decreases making steel sheet more susceptible to stress strain
Solution Approach 1:
The patent modifies the resin composition parameters to reduce curing shrinkage rate to 15% or less. This parameter change in the adhesive material compensates for the reduced mechanical strength of thinner steel sheets, preventing stress strain and magnetic property deterioration while maintaining the benefits of reduced core iron loss.
Solution Approach 2:
The patent uses the modified resin composition as an intermediary that mediates between the thin steel sheets. The resin's reduced hardness and curing shrinkage act as a cushioning medium that bonds the sheets without transmitting excessive stress, thereby protecting the thin sheets from deformation while maintaining structural integrity.
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 composition achieves both excellent magnetic properties and heat resistance, maintaining adhesion strength between electrical steel sheets even at high temperatures, thereby improving the performance of laminated cores and rotary electric machines.
Implementation Method 1
an elastomer-modified phenolic resin, wherein a glass transition point of the elastomer portion is -50°C to 0°C
Implementation Method 2
a curing shrinkage rate of the coating composition is 15% or less
Data Source
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AI summary
An electrical steel sheet used for a laminated core is an electrical steel sheet including an insulation coating 3 on a surface of a base steel sheet 2, the insulation coating being coated with a coating composition for an electrical steel sheet. The coating composition for an electrical steel sheet includes: an epoxy resin; an epoxy resin curing agent; and an elastomer-modified phenolic resin, in which the amount of the elastomer-modified phenolic resin is 10 parts by mass to 100 parts by mass with respect to 100 parts by mass of the epoxy resin.