Partial Hardening of Hot-Formed Steel Parts With In-Die Cutting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for producing formed parts for motor vehicles struggle to achieve a near-net-shape with specific material characteristics, requiring separate operations for hot-forming, cutting, and pressure hardening, which can lead to undesirable changes in shape and structure.
Innovation Solution
A process and device that integrate hot-forming, cutting, and pressure hardening in a single stage using a combined hot-forming cutting device, where a semi-finished product is heated to a hardening temperature, formed into a three-dimensional part, and then cut and pressure-hardened to create regions with varying hardness and ductility, allowing for near-net-shape production with desired material properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If separate operations are used for hot-forming, cutting, and pressure hardening, then each operation can be optimized independently, but the process complexity increases and undesirable changes in shape and structure occur
Solution Approach 1:
The patent combines hot-forming, cutting, and pressure hardening operations into a single integrated device. The forming tool includes both forming elements and cutting elements that can operate simultaneously or sequentially, eliminating the need for separate operations and reducing shape changes that would occur during multiple handling steps.
Solution Approach 2:
The forming tool is designed with multi-functionality, serving as both a forming device and a cutting device. The tool can perform hot-forming to create the basic shape, then immediately perform cutting operations and pressure hardening on the same workpiece without removal, making a single device perform multiple functions that would traditionally require separate machines.
2Productivity
If separate operations are used for hot-forming, cutting, and pressure hardening, then each operation can be performed with specialized equipment, but the production cycle time increases
Solution Approach 1:
By merging hot-forming, cutting, and pressure hardening into one integrated device, the patent eliminates the time required to transfer workpieces between separate machines and the idle time between operations. All three processes can occur in a single continuous operation, dramatically reducing the total cycle time despite the increased complexity of the equipment.
3Strength
If the entire formed part is hardened by rapid cooling, then the part achieves high strength and hardness, but the ductility is reduced in all regions
Solution Approach 1:
The patent applies local quality by differentiating the thermal treatment of different regions of the formed part. The forming tool has different thermal characteristics in different zones, causing rapid cooling (hardening) in some regions while maintaining higher temperature (ductility) in other regions. This allows the part to have high strength where needed while retaining ductility in regions requiring formability or impact absorption.
Solution Approach 2:
The forming tool is segmented into different thermal zones with distinct cooling rates. Some regions of the tool are designed to conduct heat away rapidly from the workpiece, while other regions maintain higher temperatures longer. This segmentation of the thermal field allows different material properties to be achieved in different regions of the same workpiece.
4Strength
If cutting is performed after pressure hardening, then the material strength is high, but the cutting difficulty and tool wear increase
Solution Approach 1:
The patent performs cutting action before the material fully hardens by controlling the sequence of operations within the integrated device. The cutting elements operate on the workpiece while it is still in a more ductile state, either immediately after hot-forming or during the controlled cooling process, before rapid hardening occurs in the cut regions. This preliminary cutting action reduces cutting forces and tool wear compared to cutting fully hardened material.
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 integrated process minimizes shape and structure changes, enables cost-effective production with reduced cycle times, and allows for the creation of formed parts with specific material properties suitable for motor vehicle components.
Implementation Method 1
heating a semi-finished product consisting of hardenable hot-formable sheet steel to a hardening temperature
Implementation Method 2
Rapid cooling (quenching), more particularly, takes place below the critical cooling temperature, so that a martensitic hardness structure is formed
Implementation Method 3
heating elements are integrated into a forming tool in order to heat the sheet metal in certain regions in the forming tool and to influence the material structure by specific tempering operations
Data Source
AI summary
A process of producing a partially hardened metallic formed part comprises: heating a semi-finished product of hardenable hot-formable steel sheet to a hardening temperature; hot-forming the heated semi-finished product in a combined hot-forming cutting device into a three-dimensional formed part; cutting the formed part in the combined hot-forming cutting device; pressure-hardening the formed part in the hot-forming cutting device into a hardened formed part such that a first partial region is hardened by rapid cooling and that a second partial region of the formed part is heat-treated so as to comprise a greater ductility and a lower strength than the first partial region, wherein the operation of cutting the formed part takes place at least in one of the first and second partial region. A combined hot-forming cutting device can be used to produce a metallic formed part.