Wheel Disc Hot Forming for Lightweight High-Strength Steel Wheels
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Solution Overview
Problem
Conventional methods for manufacturing vehicle wheels face limitations in achieving lightweight construction, design freedom, and rigidity due to the exhaustion of cold formability in high-strength steels, and the complexity of producing design-optimized spoke-shaped wheel discs with sufficient thinning and mechanical properties.
Innovation Solution
A method involving the use of hardenable steel materials with a predominantly martensitic and/or bainitic microstructure, where a flat steel plate is cold-formed into a bowl-shaped preform, then hot-formed with partial press hardening to create a spoke-shaped wheel disc with optimized geometry and bolt hole features, allowing for reduced sheet thickness and enhanced design capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If high-strength steels are used to reduce wheel weight, then weight reduction is achieved, but cold formability decreases and is nearly exhausted
Solution Approach 1:
The patent changes the temperature parameter during manufacturing, transitioning from cold forming to hot forming processes. This allows the use of high-strength steels with improved formability at elevated temperatures, enabling weight reduction while maintaining manufacturability through thermal parameter modification
Solution Approach 2:
The patent employs dual-phase steels and micro-alloyed steels with specific compositional characteristics (carbon content 0.15-0.40%, alloying elements) to create a composite microstructure that provides both high strength and adequate formability, resolving the contradiction between weight reduction and manufacturing ease
2Weight of moving object
If material strength is increased to enable lightweight construction, then weight reduction potential is unlocked, but cold formability decreases
Solution Approach 1:
The patent utilizes temperature parameter changes to decouple the relationship between strength and formability. By performing hot forming at elevated temperatures, the material exhibits improved formability during processing, then achieves high strength after cooling and phase transformation, effectively resolving the contradiction
3Device complexity
If conventional cold forming processes are used, then manufacturing simplicity is maintained, but design freedom and stiffness are severely limited
Solution Approach 1:
The patent introduces hot forming as an alternative parameter regime that expands design freedom and achievable stiffness while maintaining relatively simple manufacturing processes. The thermal parameter change enables new geometric possibilities and material properties without significantly increasing process complexity
4Weight of moving object
If sheet thickness is reduced for lightweight construction, then weight reduction is achieved, but stiffness losses occur requiring geometric adjustments
Solution Approach 1:
The patent uses hot forming to achieve superior strength-to-thickness ratios through controlled phase transformation and microstructure development. This allows thinner sheets to maintain or exceed the stiffness of thicker conventional sheets, enabling weight reduction without stiffness compromise
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 approach enables significant weight reduction, improved cyclic bending fatigue strength, and increased design freedom for vehicle wheels while maintaining the necessary mechanical properties and safety, overcoming the limitations of conventional manufacturing techniques.
Implementation Method 1
heating the spoke-shaped wheel rim preform (1'') to a temperature of at least AC1, in particular to an austenitic temperature range
Implementation Method 2
wherein the spoke-shaped wheel rim preform (1'') is heated to a temperature of at least AC1 for subsequent hot forming or re-forming with at least partial press hardening
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The present invention relates to a method for producing a wheel disc (1"") for a vehicle wheel, comprising an inner region (2) with a wheel contact region (2.1), in which wheel bolt holes (2.3) with a wheel bolt hole geometry and/or a wheel bolt seat face (2.31) are provided, an outer region (3) with a wheel disc lug (3.1) for attachment to a rim, and a middle region (4) connecting the outer and inner region (2.3). The invention further relates to a method for production of a vehicle wheel of this kind.