Low-Temperature Sheet Metal Forming for High-Strength Parts
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Solution Overview
Problem
Existing methods for producing load-compliant sheet-metal parts, such as hot forming, require significant energy for heating and pose challenges with surface coatings, and low-temperature forming methods using liquid refrigerants are not suitable for industrial-scale use due to safety concerns and inefficiencies.
Innovation Solution
A method involving a thermally regulated cooling apparatus to reduce the material temperature of sheet-metal parts to below −20°C, combined with a thermally regulated forming tool, allowing for partial conversion of austenite to martensite and enabling industrial-scale low-temperature forming without the risks associated with liquid refrigerants, while maintaining cathodic corrosion protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If hot forming is used to achieve high tensile strengths and yield points, then the material strength is improved, but the energy consumption increases enormously due to heating above AC1 transition temperature
Solution Approach 1:
The patent inverts the conventional hot forming approach by using cold forming instead. The sheet metal is formed at ambient or low temperatures, and the desired high strength is achieved through subsequent heat treatment that transforms the microstructure, rather than forming at high temperature and then cooling. This inversion eliminates the enormous energy outlay for heating while still achieving high tensile strengths and yield points through controlled phase transformation during or after forming.
Solution Approach 2:
The patent changes the temperature parameter from high (above AC1 transition temperature) to ambient or low temperatures during the forming process. By adjusting the forming temperature and subsequent heat treatment parameters, the material achieves high strength properties without requiring enormous energy input for heating, thus resolving the contradiction between strength improvement and energy consumption.
2Object-affected harmful factors
If tin-containing surface coatings are used to provide cathodic corrosion protection, then corrosion protection is improved, but the risk of melting the zinc surface coating increases during heating
Solution Approach 1:
The patent inverts the sequence and temperature conditions: instead of applying tin-containing coatings and then subjecting them to high-temperature hot forming (which risks melting the zinc substrate), the patent uses ambient or low-temperature forming followed by controlled heat treatment. This inversion eliminates the risk of surface coating melting while still achieving high material strength through microstructure transformation, and maintains cathodic corrosion protection through appropriate coating selection.
3Ease of manufacture
If uncoated semifinished parts are used to avoid coating issues, then processing simplicity is improved, but scaling occurs if operation is not carried out in protective gas
Solution Approach 1:
The patent inverts the approach by using ambient or low-temperature forming without protective gas atmospheres, followed by controlled heat treatment. This eliminates the need for expensive protective gas environments during forming while preventing scaling through the lower processing temperatures. The material still achieves high strength properties through controlled phase transformation during heat treatment, thus resolving the contradiction between processing simplicity and prevention of scaling.
4Strength
If liquid refrigerants like liquid nitrogen or oxygen are used for low-temperature forming, then high tensile strengths and yield points are achieved, but safety risks increase and industrial-scale use becomes difficult
Solution Approach 1:
The patent replaces expensive and hazardous liquid refrigerants with ambient temperature or mildly cooled environments. Instead of immersing components in liquid nitrogen or oxygen, the patent uses controlled cooling apparatus that can achieve the necessary low temperatures through more safe and economically viable means, making the process suitable for industrial-scale production while maintaining the material strength benefits of low-temperature forming.
Solution Approach 2:
The patent introduces a controlled cooling apparatus as an intermediary between the component and the environment, rather than directly exposing components to liquid refrigerants. This intermediary system achieves the necessary low temperatures through controlled heat exchange, eliminating the safety risks and operational difficulties associated with liquid nitrogen or oxygen while still enabling high strength properties through low-temperature forming.
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 achieves significant increases in yield point and tensile strength, enables efficient industrial-scale production of load-compliant sheet-metal parts with enhanced corrosion protection, and reduces energy consumption and production costs by avoiding expensive tailored blanks and additional reinforcements.
Implementation Method 1
the panel or the semifinished part is at least partially cooled to a temperature below −20° C. before the shaping
Implementation Method 2
reduction of the material temperature of the panel or the semifinished part to below −20° C. is carried out in a thermally regulated cooling apparatus
Implementation Method 3
the austenitic structure is converted into martensite by the rapid cooling, so that very high tensile strengths and yield points can be provided
Data Source
AI summary
The invention relates to a method for producing a shaped sheet-metal part from a panel or a semifinished part made of a material consisting of steel with at least 60 wt. % Fe and a residual austenite content of at least 5%, in which the panel or the semifinished part is at least partially cooled to a temperature below −20° C. before the shaping and is shaped at a temperature below −20° C. in a forming tool. The object of providing a method for producing load-compliantly configured components, which on the one hand permits industrial-scale use of low-temperature forming and is configured particularly simply, is achieved by reducing the material temperature of the panel or semifinished part to below −20° C. is carried out in a thermally regulated cooling apparatus.