Stator Core Laser Welding Preheating to Suppress Gas Pits
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Solution Overview
Problem
Conventional stator cores in automotive alternators suffer from weld defects such as pits and blowholes due to volatile gases from thermal decomposition of organic insulating coatings, which degrade magnetic properties and increase manufacturing costs, and existing countermeasures either compromise magnetic properties or impose grade constraints on electromagnetic steel sheets.
Innovation Solution
A manufacturing method that involves preheating the outer circumferential portions of laminated magnetic segments before welding to decompose organic components in the insulating coating, thereby suppressing gas generation and eliminating the need for rough surfaces or gas drainage channels, allowing for improved magnetic properties and cost-effective production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If organic insulating coating is coated onto magnetic steel sheet surfaces, then punchability, electrical insulation, and corrosion prevention are ensured, but volatile gases from thermal decomposition cause weld defects such as pits and blowholes
Solution Approach 1:
The patent applies preliminary action by preheating the magnetic steel sheet before welding to decompose organic substances in the insulating coating in advance. This converts the harmful volatile gases into harmless combustion products (CO2 and H2O) before they can penetrate the weld bead, thereby preventing weld defects while maintaining the electrical insulation properties of the coating
2Object-affected harmful factors
If rough surfaces are formed on electromagnetic steel sheet, then gas penetration into weld bead is stopped, but magnetic properties and space factor decrease
Solution Approach 1:
The patent replaces the mechanical approach of forming rough surfaces with a thermal approach. Instead of mechanically altering the surface to prevent gas penetration, the invention uses preheating to thermally decompose organic substances, substituting a thermal field for a mechanical field to achieve the same protective effect while preserving magnetic properties
3Object-affected harmful factors
If gas drainage channels are formed on weld portions, then gas penetration is stopped, but machining strain generates and magnetic properties decrease
Solution Approach 1:
The patent replaces the mechanical method of forming gas drainage channels with a thermal process. Instead of mechanically creating channels that induce stress, the invention uses preheating to decompose organic materials, substituting a thermal field for a mechanical field to eliminate gas issues without compromising magnetic properties
4Strength
If silicon content of electromagnetic steel sheet is increased to improve hardness, then rough surface formation becomes difficult, but grade constraints are placed on the steel sheet
Solution Approach 1:
The patent replaces the mechanical process of rough surface formation with a thermal preheating process. This substitution eliminates the need to adjust steel grade or silicon content to achieve rough surfaces, thereby removing grade constraints while maintaining the ability to prevent gas penetration through thermal decomposition
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
This method effectively suppresses weld defects, enhances magnetic characteristics, and eliminates grade constraints on electromagnetic steel sheets, resulting in superior stator core quality and reduced manufacturing costs.
Implementation Method 1
a first preheating step in which a welding position on a wall surface on an opposite side of the stacked core back portions of the laminated body from the tooth portions is heated locally from a first end to a second end in a direction of lamination to decompose an organic component in the insulating coating thermally at the welding position
Implementation Method 2
organic substances in the insulating coating decompose thermally when the outer circumferential portions of the laminated body of magnetic segments are laser-welded, giving rise to volatile gases
Implementation Method 3
a first welding step in which the welding position at which the organic component in the insulating coating is decomposed thermally is welded from the first end to the second end in a direction of lamination to interconnect and integrate the laminated magnetic segments
Data Source
AI summary
The method for manufacturing a stator core includes: a punching step in which magnetic segments are punched out of an electromagnetic steel sheet that is coated with an organic insulating coating; a laminating step in which a laminated body is formed by laminating a predetermined number of the punched magnetic segments; a first preheating step in which a welding position on a wall surface of the laminated body is heated locally from a first end to a second end in a direction of lamination to decompose an organic component in the insulating coating thermally at the welding position; and a first welding step in which the welding position at which the organic component in the insulating coating is decomposed thermally is welded from the first end to the second end in the direction of lamination to interconnect and integrate the laminated magnetic segments.