Al-Si Plated Steel Sheet for Hot-Press Impact Resistance
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Solution Overview
Problem
Existing hot press formed parts exhibit poor impact properties due to the formation of locally formed ferrite in the surface layer, which concentrates deformation and leads to easy fracture, limiting the improvement of impact resistance in complex automotive components.
Innovation Solution
A plated steel sheet with a carbon-depleted layer of 5 μm or less and a carbon-enriched layer of 110% or more of the average carbon content in the surface layer, combined with an Al-Si plated layer, is used to enhance impact properties through localized hardenability and suppression of ferrite formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high strength is achieved through hot press forming with Al-Si plated layer, then tensile strength reaches 1600 MPa or more, but impact property deteriorates
Solution Approach 1:
The invention applies local quality by creating a carbon-enriched layer specifically in the surface layer part (0-200μm depth) of the base steel sheet, while maintaining the overall high strength structure. This localized carbon enrichment (1.0-3.0 times the average carbon content) provides enhanced impact resistance at the surface where deformation concentrates, without compromising the bulk material's high strength properties achieved through hot press forming
Solution Approach 2:
The invention changes the carbon content parameter locally in the surface layer part, increasing it from the average carbon content to 1.0-3.0 times the average carbon content. This parameter change creates a carbon-enriched layer that improves impact property by preventing ferrite formation and concentrating deformation, while the overall tensile strength is maintained at 1600 MPa or more through the hot press forming process
2Reliability
If carbon content is increased to improve impact property, then impact resistance improves, but tensile strength may be reduced
Solution Approach 1:
The invention applies local quality by increasing carbon content only in the surface layer part (0-200μm depth) to 1.0-3.0 times the average carbon content, while keeping the bulk material composition relatively low in carbon. This localized enrichment improves impact resistance at the critical surface region without significantly reducing the overall tensile strength of the material
Solution Approach 2:
The invention segments the steel sheet into different regions with different carbon contents: the surface layer part (0-200μm) has enhanced carbon content for impact resistance, while the core region maintains lower carbon content for high strength. This segmentation allows simultaneous optimization of both impact property and tensile strength
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 results in a hot press formed part with improved impact properties, achieving a product of tensile strength and impact absorption energy greater than 8000 MPa·J, suitable for automotive components requiring high impact resistance.
Implementation Method 1
an Al—Si plated layer which has a thickness of 10 to 45 μm and serves to suppress surface decarburization
Implementation Method 2
a carbon-depleted layer having a thickness of 5 μm or less in a surface layer part of the base steel sheet... a carbon-enriched layer having a thickness of 10 to 150 μm... the carbon content is 1.0 to 3.0 times as much as an average carbon content
Implementation Method 3
an Al—Si plated steel sheet, which is heated to 850° C. or higher and then hot press formed and quenched by a press, and a structure of the member can be formed into martensite
Data Source
AI summary
One aspect of the present invention relates to a plated steel sheet for hot press forming, having an excellent impact property.