Localized Induction Heating of Punched Steel Plate Edges

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Solution Overview

Problem

High-strength steel plates used in metal components are prone to delayed fracture due to residual stress and corrosive environments, which limits their application in vehicles aiming to reduce weight and emissions.

Innovation Solution

A method involving local heating of punched ends in high-strength steel plates using a heating electrode or coil, directly opposed to the punched part, to reduce residual stress and prevent delayed fractures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Weight of moving object

If high-strength steel plate is used to reduce vehicle weight, then fuel efficiency and cruising range are improved, but delayed fracture occurs due to residual stress and corrosive environment

Engineering Contradiction:
Improvevehicle weightVSAvoiddelayed fracture resistance
Core Design Contradiction:
Weight of moving objectVSReliability

Solution Approach 1:

The patent applies local heating treatment specifically to the punched end face where residual stress concentrates, rather than treating the entire component. This localized approach reduces residual stress at the critical area while maintaining the high-strength properties of the bulk material, thereby preventing delayed fracture without compromising overall vehicle weight reduction goals

Inventive Principle:
Principle #3Local quality

2Reliability

If conventional heating methods (sandwiching between electrodes or using heating coils) are used, then residual stress can be reduced, but heating range cannot be precisely controlled and overall strength decreases

Engineering Contradiction:
Improvedelayed fracture preventionVSAvoidoverall component strength
Core Design Contradiction:
ReliabilityVSStrength

Solution Approach 1:

The patent employs a heating device that applies heat locally and precisely to the punched end face, creating a temperature gradient that is high at the surface and low in the interior. This localized heating reduces residual stress at the critical surface area while leaving the bulk material strength intact, avoiding the strength reduction that occurs with conventional wide-range heating methods

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The patent applies heating treatment only to the extent necessary - specifically targeting the punched end face area where residual stress exists, rather than treating the entire component. This partial action approach achieves delayed fracture prevention without subjecting unnecessary portions of the material to thermal cycles that would reduce overall strength

Inventive Principle:
Principle #16Partial or excessive action

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 method effectively maintains the overall strength of steel plate components while preventing delayed fractures, even in corrosive environments, by reducing residual stress through localized heating.

Implementation Method 1

the steel plate component is locally heated by a heating electrode, the heating electrode being disposed on one side of the steel plate component, and spaced from and directly opposed to a punched part of the steel plate

Methodology Applied
Scientific EffectElectromagnetic induction heating: Electromagnetic Induction

Data Source

PatentEP4545199A1Method for manufacturing steel plate component and manufacturing apparatus
Publication Date: 2025.04.30 TOYOTA JIDOSHA KK
  • EP4545199A1 patent drawingFigure 1
  • EP4545199A1 patent drawingFigure 2
  • EP4545199A1 patent drawingFigure 3

AI summary

A method or the like for manufacturing a steel plate component (2), capable of maintaining the overall strength of the component and preventing a delayed fracture from occurring at the same time is provided. A method for manufacturing a steel plate component is characterized in that the steel plate component is locally heated by a heating electrode (10), the heating electrode (10) being disposed on one side of the steel plate component (2), and spaced from and directly opposed to a punched part (20) of the steel plate (2). The steel plate component is a high-strength steel plate having a tensile strength class of 780 MPa or higher. A heating temperature is 500 to 830°C. The steel plate component is locally heated by high-frequency induction for a short time period of 10 seconds or shorter. The heating electrode (10) is a coil larger than the punched part and has two turns or more for the punched part.