Heat-Forming Tool with Movable Punch for Partial Press Hardening
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Solution Overview
Problem
Conventional methods for hot forming and partial press hardening of sheet steel components, such as wheel discs, face challenges in achieving high fatigue strength and low weight while minimizing production costs and tool wear due to the complexity of existing forming tools and the need for multiple heating devices.
Innovation Solution
A method and forming tool design where a workpiece is heated and then formed using a die and punch, with one tool component part moving away from the formed workpiece to expose it to ambient air for cooling, allowing for zone-specific microstructure control, reducing complete martensite formation and thus achieving high fatigue strength at lower weight and production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If complete press hardening is applied to achieve high strength, then fatigue strength is improved, but toughness is reduced in areas requiring plastic deformation
Solution Approach 1:
The patent applies different cooling rates to different areas of the workpiece by using a movable tool component part that can be retracted. The first area remains in contact with the tool component for rapid cooling and complete martensite transformation (high strength), while the second area is exposed to ambient air for slower cooling and retained austenite formation (high toughness). This local differentiation resolves the contradiction between fatigue strength and toughness requirements in different zones.
2Adaptability or versatility
If heating devices are added to the forming tool for local soft structure setting, then partial press hardening capability is improved, but device complexity and production costs increase
Solution Approach 1:
Instead of adding heating devices to create soft structures, the patent inverts the approach by using a movable tool component that can be retracted to expose certain areas to ambient air for slower cooling. This eliminates the need for complex heating devices while achieving the same partial press hardening effect through controlled cooling rates, thereby reducing device complexity and production costs.
Solution Approach 2:
The patent uses the ambient air surrounding the forming tool as a natural cooling medium, eliminating the need for active heating devices. The movable tool component part leverages the temperature difference between the heated workpiece and ambient air to achieve slower cooling in the second area, reducing device complexity while maintaining partial press hardening capability.
3Weight of moving object
If higher strength steel materials are used to reduce weight, then weight is reduced, but formability decreases
Solution Approach 1:
The patent changes the temperature parameter of the workpiece during forming by heating it before forming and then applying controlled cooling. This thermal parameter change temporarily improves the formability of high-strength steel materials during the forming process, allowing weight reduction through higher strength materials without sacrificing manufacturability. The heating enables the steel to be formed more easily, and the subsequent controlled cooling creates the desired microstructure.
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 enables the production of components with high fatigue strength and reduced weight by controlling microstructure through partial press hardening, avoiding complete martensite formation in critical areas, thereby enhancing the structural integrity and reducing material costs.
Implementation Method 1
the workpiece is heated before forming, in which the heated workpiece is then placed in a forming tool
Implementation Method 2
the formed workpiece is then exposed directly, at least in sections, to a gas surrounding the forming tool and is thereby cooled
Implementation Method 3
the structure at these points is completely transformed into martensite and thus fully press-hardened
Data Source
Figure 1a~1d
AI summary
The invention relates to a method for heat-forming a work piece (1), in particular a blank made of sheet steel, wherein: the work piece (1) is heated before being formed; the heated work piece (1) is then heat-formed in a forming tool (2), having two tool components (3, 4) in the form of a die (3) and a punch (4), by coming into contact with both tool components (3, 4); and then at least sections of the formed work piece (1) are directly exposed to a gas surrounding the forming tool (2), thereby quenching said work piece. According to the invention, in order to achieve the highest possible fatigue strength with low weight and reduced production costs, after the forming process, at least one tool component part (4.1) of the one tool component (4) is moved away from the side (1a) of the formed work piece (1) facing the tool component (4), while the side (1b) of the formed work piece (1) facing away from said tool component (4) remains entirely in contact with the other tool component (3). The invention also relates to a corresponding forming tool (2) and a corresponding work piece (1).