Thermal-Assisted Roll Forming of High-Strength Sheet Metal
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Solution Overview
Problem
High-strength materials with low ductility pose challenges in roll forming due to fracturing under large strains, especially when producing complex profiles with sharp corners, as existing processes struggle to balance strength and formability at high speeds.
Innovation Solution
A thermal-assisted roll forming process that involves locally heating high-strength cold rolled sheet metal to a temperature within the two-phase sub-critical or above the critical temperature region, followed by rapid quenching after bending, to enhance formability and retain high temperature phases for increased strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high-strength materials with low ductility are used, then product strength is improved, but the material fractures during bending due to large strains
Solution Approach 1:
The patent applies parameter changes by heating the high-strength material to elevated temperatures (e.g., austenitic temperature range for steels) before bending. This temperature parameter change transforms the material's microstructure and mechanical properties, increasing ductility and reducing flow stress during forming. After bending, rapid cooling transforms the microstructure again to achieve the desired high strength in the final product.
Solution Approach 2:
The patent utilizes phase transitions by heating the material into the two-phase or fully austenitic region, where the material exhibits superior ductility for forming operations. The subsequent rapid cooling induces a martensitic or other high-strength phase transformation, achieving both formability during processing and high strength in the final product.
2Ease of manufacture
If room temperature roll forming is used for high-strength materials, then manufacturing simplicity is maintained, but the material cannot accommodate sharp corners and complex profiles due to low ductility
Solution Approach 1:
The patent changes the temperature parameter during critical forming operations to enable complex profiles and sharp corners. By locally or globally heating the material before bending operations, the material's ductility increases, allowing it to accommodate complex geometries without fracture. The process maintains manufacturing efficiency through continuous processing with integrated heating and forming zones.
3Productivity
If conventional roll forming at room temperature is used, then process continuity and high speed are maintained, but the material properties deteriorate due to inability to achieve required deformation
Solution Approach 1:
The patent applies preliminary action by heating the material before it enters the forming rollers. This pre-heating prepares the material with appropriate ductility and reduced flow stress, enabling successful deformation at high speeds. The heating occurs in advance in a separate zone, allowing the material to be properly conditioned before the critical bending operations.
Solution Approach 2:
The patent utilizes phase transitions to enable high-speed continuous forming. By maintaining the material in an austenitic or two-phase region during forming, the material exhibits enhanced formability. Rapid cooling after forming transforms the microstructure to achieve high strength, allowing continuous high-speed processing without compromising material properties.
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
Enables high-speed, continuous deformation of high-strength materials without sacrificing strength, allowing for the production of complex profiles with reduced springback and enabling the use of lower alloy materials, such as aluminum for lighter and cost-effective components like automobile bumpers.
Implementation Method 1
providing intense local heat from a heat source that is targeted at the location that will subsequently become bent upon entering the rollers, heating the cold rolled sheet metal to a temperature within the two-phase sub-critical temperature region or above the critical temperature
Implementation Method 2
rapidly quenching the cold rolled sheet metal after bending
Implementation Method 3
the high temperature phase will transform upon quenching to room temperature to other higher strength phases, such as retained austenite, martensite, and/or bainite
Implementation Method 4
The rapid quench allows the alloys that demonstrate subsequent precipitation hardening, such as aluminum or magnesium, to retain the high temperature phase structure at room temperature
Data Source
AI summary
A thermal-assisted method deforms plastically a high-strength material using a high-intensive heat source. The high-strength material may be a cold-rolled sheet aluminum of strength greater than 300 megapascal (MPa) or a cold-rolled sheet steel of strength greater than 1000 MPa. The cold-rolled sheet metal is heated just before bending to a temperature near or above the critical temperature for the material and is followed by rapid quenching after bending.