Tailored Blank Weld Structure for Crack-Resistant Hot Stamping
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Solution Overview
Problem
Tailored blanks manufactured from steel sheets with different thicknesses are prone to cracks at the weld metal due to aluminum-based plating at the weld portion, compromising both strength and corrosion resistance.
Innovation Solution
A tailored blank design where the aluminum-based plated layer is partially removed at the weld interface, maintaining an average Al concentration of 0.05 to 1.00 mass% in the weld metal, with specific thickness and carbon concentration ratios between the steel sheets, and incorporating a base exposed portion to prevent stress concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If aluminum-based plating is applied to steel sheets for hot stamping, then corrosion resistance is improved, but cracks occur in weld metal
Solution Approach 1:
The patent applies local quality by creating different plating conditions at different locations: the aluminum-based plating is removed from the weld portion to prevent cracks, while maintaining plating at non-weld portions for corrosion resistance. This localized differentiation resolves the contradiction between needing plating for corrosion resistance and needing to avoid plating at weld zones for strength.
Solution Approach 2:
The steel sheet is segmented into different functional zones: a weld portion where plating is removed to ensure weld metal strength, and non-weld portions where plating remains for corrosion resistance. This segmentation allows each zone to have optimized properties for its specific function.
2Strength
If aluminum-based plating is removed from weld portion, then weld metal strength is improved, but corrosion resistance deteriorates
Solution Approach 1:
The invention applies local quality by creating different plating conditions at different locations: the aluminum-based plating is removed from the weld portion to prevent cracks, while maintaining plating at non-weld portions for corrosion resistance. This localized differentiation resolves the contradiction between needing plating for corrosion resistance and needing to avoid plating at weld zones for strength.
Solution Approach 2:
The non-weld portions with aluminum-based plating act as intermediaries that provide corrosion resistance to the overall structure, compensating for the removed plating at weld portions. This allows the weld zones to be optimized for strength while the structure maintains overall corrosion resistance through the plated non-weld areas.
3Adaptability or versatility
If steel sheets with different thicknesses are used to improve functionality, then yield and functionality are improved, but stress concentration occurs at weld interface
Solution Approach 1:
The patent applies local quality by creating a base exposed portion at the weld interface of the thin steel sheet. This local structural modification at the weld interface reduces stress concentration caused by thickness differences, allowing the use of different thickness sheets for functionality while maintaining weld interface strength.
4Reliability
If aluminum-based plating is partially removed to control Al concentration, then weld metal quality is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by removing the aluminum-based plating from the weld portion before the welding process. This pre-treatment ensures that the weld metal quality is optimized from the start, avoiding the need for complex post-weld treatments or quality corrections.
Solution Approach 2:
The invention applies parameter changes by controlling the aluminum concentration in the weld metal within a specific range (0.05-1.00 mass%) through selective plating removal. This parameter optimization improves weld metal quality while maintaining a manageable manufacturing process.
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
Ensures both high strength and corrosion resistance of the weld metal, preventing fractures and enhancing the tailored blank's structural integrity.
Implementation Method 1
the aluminum-based plated layer is partially removed at the weld interface, maintaining an average Al concentration of 0.05 to 1.00 mass% in the weld metal
Implementation Method 2
end surfaces of at least two steel sheets are butted and joined by laser welding
Implementation Method 3
a steel sheet is heated to a high temperature and press-formed in a temperature range equal to or higher than Ar3 transformation temperature
Implementation Method 4
a press-formed steel sheet is rapidly cooled by removing heat with a die, and transformation is caused simultaneously with formation
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A tailored blank includes: a first steel sheet; a second steel sheet butt-welded to the first steel sheet; and a weld metal connecting an end portion of the first steel sheet and an end portion of the second steel sheet, in which a sheet thickness h1 and a carbon concentration C1 of the first steel sheet and a sheet thickness h2 and a carbon concentration C2 of the second steel sheet satisfy predetermined formulas, a step difference LDa between the surface A S1A of the first steel sheet and the surface A S2A of the second steel sheet and a step difference LDb between the surface B S1B of the first steel sheet and the surface B S2B of the second steel sheet satisfy a predetermined formula, the first steel sheet includes an aluminum-based plated layer on the surface A S1A of the first steel sheet, the aluminum-based plated layer disposed on the surface A S1A of the first steel sheet is in contact with the weld metal, the first steel sheet includes a base exposed portion on the surface B S1B of the first steel sheet, and the base exposed portion on the surface B S1B of the first steel sheet is in contact with the weld metal.