Blank Gripper Temperature Control for Joinable Press-Quenched Steel
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Solution Overview
Problem
Hot-formed and press-quenched sheet-steel products often exhibit metallurgical notches and weakened joints due to heat-affected zones formed during thermal joining techniques like welding, which affect the hardness and integrity of the welds.
Innovation Solution
A hot-forming line that includes a temperature control station, a hot-forming and press-quenching tool, and blank grippers configured to selectively cool or heat the contact regions of the sheet-metal blanks before and after the hot-forming process, ensuring uniform microstructure and reducing the hardness of the contact regions to prevent weakening during subsequent joining.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If thermal joining techniques like welding are used to join hot-formed and press-quenched sheet-steel products, then the products can be connected to other components, but metallurgical notches and weakened joints are formed due to heat-affected zones
Solution Approach 1:
The patent applies parameter changes by modifying the temperature distribution across the sheet-metal blank before joining. The blank is heated to different temperatures in different regions (contact regions vs. non-contact regions), creating a temperature gradient that prevents uniform martensitic microstructure formation in contact areas. This selective temperature control eliminates the formation of hard, brittle martensite in regions that will undergo thermal joining, thereby preventing metallurgical notches and maintaining joint strength.
Solution Approach 2:
The patent implements local quality by creating spatially differentiated microstructures within the sheet-metal blank. Contact regions (where gripping and subsequent joining occurs) are maintained at lower temperatures to avoid martensitic transformation, while non-contact regions are allowed to form martensite for high strength. This local differentiation of material properties ensures that joining areas remain ductile and resistant to thermal cracking, while other areas maintain high strength through martensitic hardening.
2Strength
If the sheet-metal blank is rapidly cooled to form martensitic microstructure for hardening, then the material strength is increased, but the contact regions become too hard and brittle for subsequent thermal joining
Solution Approach 1:
The patent applies segmentation by dividing the sheet-metal blank into functionally distinct regions: contact regions and non-contact regions. Each region is subjected to different thermal treatments during the hot-forming process. Contact regions are cooled more slowly or maintained at lower temperatures to prevent martensitic transformation, ensuring ductility for joining. Non-contact regions undergo rapid cooling to form martensite for high strength. This spatial segmentation of thermal processing resolves the contradiction between overall hardening and local joinability.
3Strength
If additional aftertreatment processes are applied to prevent metallurgical notches, then joint strength is improved, but production time and costs increase
Solution Approach 1:
The patent implements preliminary action by preventing the formation of problematic martensitic microstructure in contact regions during the initial hot-forming process itself, rather than requiring subsequent corrective treatments. By controlling the temperature distribution and cooling rate during hot-forming, the blank is prepared in advance with appropriate microstructure differentiation, eliminating the need for additional aftertreatment processes like controlled cooling racks or thermal processing steps that would extend production time and increase costs.
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 solution prevents the formation of metallurgical notches and strengthens the joints by maintaining a consistent microstructure, reducing production time and costs by eliminating the need for additional aftertreatment and minimizing heat-induced stress in the contact regions.
Implementation Method 1
a sheet-metal blank composed of a hardenable steel alloy is heated at least in some region or regions to a temperature above the austenitization temperature
Implementation Method 2
the sheet-metal blank, composed of the material 22 MnB5 by way of example, is cooled rapidly at a cooling rate greater than 27 K/s in order to form a martensitic microstructure
Implementation Method 3
at least one blank gripper for gripping and transferring the sheet-metal blank before and/or after hot forming and press quenching
Data Source
AI summary
A hot-forming line for producing hot-formed and press-quenched sheet-steel products includes a temperature control station for heating at least one sheet-metal blank, a hot-forming and press-quenching tool for hot forming and press quenching the heated sheet-metal blank and at least one blank gripper for gripping and transferring the sheet-metal blank before and/or after hot forming and press quenching. The at least one blank gripper forms at least one contact region with the sheet-metal blank during the gripping of the sheet-metal blank. Also, the at least one blank gripper is configured to cool the sheet-metal blank in the at least one contact region during gripping and transfer of the sheet-metal blank before hot forming and press quenching and/or heat the sheet-metal blank in the at least one contact region during gripping and transfer after hot forming and press quenching.