Hot-Formed Steel Component with Multi-Phase Microstructure
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Solution Overview
Problem
The production of steel components by hot forming using press hardening above the austenitization temperature is energy-intensive, costly, and results in high CO2 emissions, with limitations in cathodic corrosion protection and reduced throughput due to the need for accelerated cooling and complex protective layers.
Innovation Solution
A method for hot forming steel components at temperatures below the Ac3 transformation point, using a multi-phase steel with a manganese content above 3% and residual austenite, which achieves a minimum tensile strength of 700 MPa and elongation at break of over 22%, allowing for improved formability and cathodic corrosion protection with reduced energy consumption and process complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If press hardening above austenitization temperature is used, then high strength components are achieved, but energy consumption and CO2 emissions increase significantly
Solution Approach 1:
The patent changes the temperature parameter from above austenitization temperature (>800°C) to below Ac3 transformation point, and modifies the steel composition parameters (adding Mn: 3-12%, Cr: 0.5-3%, Mo: 0.1-0.6%, B: 0.005-0.05%) to achieve the desired strength at lower temperatures through multi-phase microstructure control
Solution Approach 2:
The patent creates a composite microstructure consisting of multiple phases (ferrite, martensite, bainite, and retained austenite) within the steel component, where each phase contributes different properties: ferrite provides ductility, martensite provides strength, bainite provides toughness, and retained austenite enables TRIP effect for enhanced formability
2Object-affected harmful factors
If metallic protective layers are applied before hot forming, then surface scaling is prevented, but cathodic corrosion protection is lost due to zinc evaporation at high temperatures
Solution Approach 1:
The patent applies the metallic protective layer (zinc-based coating) before the hot forming process, and through the temperature reduction below Ac3 point, ensures the coating survives the forming process without evaporating, thereby maintaining both scaling protection and cathodic corrosion protection
Solution Approach 2:
The patent converts the potential harm of zinc evaporation at high temperatures into a benefit by operating at lower temperatures, where the zinc coating remains stable and provides dual functionality: preventing surface scaling during forming and providing cathodic corrosion protection after forming
3Strength
If accelerated cooling is applied to achieve desired strength, then component strength is improved, but throughput is reduced due to extended cooling time
Solution Approach 1:
The patent prepares the steel with specific alloy composition and multi-phase microstructure before forming, so that the desired strength properties are achieved through the microstructure design rather than prolonged cooling, thereby reducing cooling time and increasing throughput
Solution Approach 2:
The patent changes the cooling rate parameter from accelerated cooling to normal cooling rates, achieving the desired strength through the pre-established multi-phase microstructure (10-80% ferrite, 10-60% martensite, 5-30% bainite, 5-20% retained austenite) rather than relying on rapid cooling
4Object-affected harmful factors
If complex protective layers are used to prevent scaling, then surface protection is improved, but process complexity and manufacturing cost increase
Solution Approach 1:
The patent extracts the complex multi-layer protective coating system and replaces it with a simple zinc-based metallic coating applied before forming, which provides adequate protection at the reduced temperature range without requiring complex process steps
Solution Approach 2:
The patent changes the temperature parameter to below Ac3 point, which reduces the severity of oxidation during forming, allowing simple metallic coatings to provide adequate protection without requiring complex protective layer systems
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 method significantly reduces energy costs and CO2 emissions while achieving superior mechanical properties, including high tensile strength and elongation, and provides effective cathodic corrosion protection, making it suitable for producing complex component geometries with improved formability and reduced distortion.
Implementation Method 1
the steel used for the method according to the invention has a multi-phase structure consisting of ferrite and/or martensite and/or bainite and retained austenite. The proportion of retained austenite is 5% to 80%. When mechanical stresses are present, the retained austenite can be partially or completely transformed into martensite by the TRIP effect.
Implementation Method 2
the precursor is heated to a temperature above 60 °C and below 450 °C and then formed
Data Source
AI summary
The invention relates to a method for producing a component by hot-forming a pre-product composed of steel, wherein the pre-product is heated to a temperature above 60 °C and below the Ac3 transformation temperature and then formed in this temperature range, wherein the component has a minimum tensile strength of 700 MPa and high elongation at break, wherein the pre-product has the following alloy composition in percent by weight: C: 0.0005 to 0.9; Mn: more than 3.0 to 12; the remainder iron including unavoidable steel-accompanying elements, with the optional addition of one or more of the following elements (in percent by weight): Al: up to 10; Si: up to 6; Cr: up to 6; Nb: up to 1.5; V: up to 1.5; Ti: up to 1.5; Mo: up to 3; Cu: up to 3; Sn: up to 0.5; W up to 5; Co: up to 8; Zr: up to 0.5; Ta: up to 0.5; Te: up to 0.5; B: up to 0.15; P: at most 0.1, in particular < 0.04; S: at most 0.1, in particular < 0.02; N: at most 0.1, in particular < 0.05; Ca: up to 0.1. The invention further relates to a hot-formed component produced from a steel.