3D Bending High-Strength Metal Tubes via Local Heating and Quenching
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Solution Overview
Problem
Existing methods for bending metal materials, such as grab bending and high-frequency heating benders, face challenges in achieving high accuracy and speed due to variations in feeding speed and residual stress, leading to uneven distortion and reduced dimensional accuracy, especially when bending high-strength materials for automotive parts.
Innovation Solution
A three-dimensional bending method involving a feeding unit, a supporting unit, and a three-dimensionally movable unit that locally heats and rapidly cools the workpiece using a high-frequency heating coil and cooling medium, ensuring precise control over the cooling speed and quenching process to maintain shape fixability and uniform hardness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If grab bending method with rotatable arm is used, then bending capability is achieved, but feeding speed varies remarkably and quenching accuracy deteriorates
Solution Approach 1:
The patent replaces the mechanical grab bending system with a high-frequency induction heating system combined with a push bending roller. The heating unit induces eddy currents in the metal tube, generating heat through electromagnetic induction rather than mechanical contact, thereby eliminating feeding speed variations and enabling precise thermal control for accurate quenching.
Solution Approach 2:
The patent changes the physical state of the metal tube by heating it to a specific temperature range (A3 transformation point or higher) before bending. This parameter change makes the material more formable during bending and enables subsequent quenching to achieve high strength, while the controlled heating process eliminates the feeding speed issues of mechanical grab bending.
2Productivity
If high-frequency heating bender without clamping is used, then feeding speed is improved, but dimensional accuracy deteriorates due to residual stress
Solution Approach 1:
The patent applies local quality by using a push bending roller that contacts only the heated portion of the metal tube for bending, while separate clamping units secure both side-faces of the workpiece. This localized bending approach, combined with proper clamping, prevents residual stress-induced distortion while maintaining high feeding speed through continuous high-frequency heating.
Solution Approach 2:
The patent introduces a cooling unit as an intermediary between the heating unit and the final bending operation. The cooling unit rapidly cools the heated portion after bending, controlling the quenching process to achieve uniform hardness and prevent distortion, thereby maintaining dimensional accuracy while enabling high-speed continuous processing.
3Strength
If thermal treatment is performed to improve strength, then tensile strength increases, but feeding speed must be reduced for control
Solution Approach 1:
The patent performs preliminary local heating of the metal tube to the A3 transformation point or higher before bending. This preliminary thermal action prepares the material for both easy forming during bending and subsequent quenching to achieve high tensile strength (900 MPa or more), while the localized nature of the heating allows continuous high-speed processing without sacrificing productivity.
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 ensures high accuracy and efficiency in bending metal materials with tensile strengths of 900 MPa or more, preventing uneven distortion and achieving uniform hardness, making it suitable for diverse automotive parts with improved shape fixability and reduced production costs.
Implementation Method 1
a heating step to locally heat a portion of the workpiece in a temperature range which allows quenching to be performed, by a heating unit
Implementation Method 2
a cooling step to rapidly cool down the heated portion in order to quench the metal material of the workpiece
Data Source
AI summary
A method for three-dimensionally bending a workpiece comprises feeding the workpiece by a feeding unit provided at an upstream side of the workpiece, supporting the workpiece by a supporting unit at a downstream side of the feeding unit, processing the workpiece by clamping the workpiece with a three-dimensionally movable unit that is provided downstream of the supporting unit, heating a local part of the workpiece in a temperature range which allows quenching to be performed, applying a bending moment to the heated local part of the workpiece by the three-dimensionally movable unit in association with the supporting position and/or the moving speed of the workpiece after the heating step, and rapidly quenching the heated portion. Even when a high-strength workpiece is bent, it is possible to effectively obtain a product having excellent shape fixability and uniform hardness distribution at low costs for wide application for bending sophisticated automobile parts.