Aluminum-Coated Blank Joints with Martensite-Rich Laser Bonding
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Solution Overview
Problem
Existing methods for manufacturing aluminum coated blanks face challenges in maintaining the mechanical properties of joint portions, particularly in hot stamping processes, due to segregation issues and reduced strength caused by aluminum-silicon or zinc coatings during laser bonding, which affect the absorption of impact energy and structural integrity in vehicle components.
Innovation Solution
An aluminum coated blank is developed with specific chemical compositions and manufacturing processes, including a base iron with controlled carbon, silicon, manganese, and aluminum content, and a coated layer with an aluminum-iron-silicon intermetallic compound, where the joint portion contains a high percentage of martensite microstructure, achieved through precise laser bonding and cooling rates, to enhance hardness and prevent segregation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If aluminum-silicon or zinc coated layers are used on steel sheets for laser bonding, then the coated steel sheets can be bonded together, but the coating components are introduced into the melted pool during laser bonding, resulting in decreased mechanical properties of the bonded portion
Solution Approach 1:
The patent applies parameter changes by precisely controlling the aluminum content in the coated layer (5-15 wt%) and the base steel (0.01-0.1 wt%), as well as controlling the cooling rate (10-500°C/s) during hot stamping. These parameter adjustments prevent excessive aluminum segregation in the joint portion while maintaining laser bonding capability, thereby resolving the contradiction between ease of manufacture and mechanical properties.
Solution Approach 2:
The patent implements local quality by creating a specific martensitic microstructure (90% or more) in the joint portion through controlled cooling, which differs from the base material structure. This local microstructural optimization ensures that the joint portion has enhanced mechanical properties despite the presence of coating components, addressing the strength reduction issue while maintaining bonding capability.
2Productivity
If high bonding speed is used for laser bonding to increase productivity, then productivity improves, but the introduced coating components (Al) are not evenly diluted with the base material, causing segregation and insufficient effects of filler wire components
Solution Approach 1:
The patent applies preliminary action by pre-coating the steel sheets with aluminum at controlled concentrations (5-15 wt%) before laser bonding. This preliminary coating control ensures that even at high bonding speeds, the aluminum content in the melted pool remains within acceptable ranges, preventing severe segregation and maintaining manufacturing precision while enabling high productivity.
Solution Approach 2:
The patent uses parameter changes by optimizing the coating aluminum content (5-15 wt%) and base steel aluminum content (0.01-0.1 wt%) to achieve uniform component distribution even at high bonding speeds. This parameter optimization resolves the contradiction between productivity and manufacturing precision by allowing fast bonding without excessive segregation.
3Strength
If different materials with different strengths are used for upper and lower portions of B-pillar to meet strength requirements, then the strength requirements are satisfied, but the materials must be bonded by laser to create a tailor welded blank
Solution Approach 1:
The patent applies local quality by creating a tailor welded blank with different steel grades for upper (high strength) and lower (lower strength) portions of the B-pillar. Each portion is coated with aluminum at optimized concentrations, and the joint portions are bonded by laser with controlled cooling to achieve 90% or more martensitic structure. This local optimization satisfies the strength requirements for different sections while managing the bonding process complexity through standardized procedures.
4Ease of manufacture
If the joint portion contains aluminum from the coated layer, then the coated steel sheets are bonded together, but the aluminum segregation occurs and the hardness and physical properties of the joint portion are reduced
Solution Approach 1:
The patent applies parameter changes by controlling the aluminum content in the coated layer (5-15 wt%) and base steel (0.01-0.1 wt%), and by controlling the cooling rate (10-500°C/s) during hot stamping. These parameter adjustments ensure that aluminum is evenly distributed and a martensitic structure (90% or more) is formed in the joint portion, preventing aluminum segregation and maintaining high hardness and physical properties while preserving bonding capability.
Solution Approach 2:
The patent utilizes phase transitions by applying rapid cooling (10-500°C/s) to transform the microstructure of the joint portion into martensite (90% or more). This phase transition occurs after laser bonding, and it enhances the hardness and physical properties of the joint portion, counteracting the potential softening effect of aluminum segregation and resolving the contradiction between bonding ease and joint reliability.
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 effectively minimizes the reduction in hardness and physical properties of joint portions, preventing defects like segregation and ensuring the joint portion's strength is greater than the base iron's, thus improving the structural integrity and energy absorption capabilities of vehicle components.
Implementation Method 1
bonding a joint portion that connects the first coated steel sheet to the second coated steel sheet by providing a filler wire at a boundary between the first coated steel sheet and the second coated steel sheet and applying a laser beam
Implementation Method 2
when the aluminum coated blank is heated to at least Ac3 temperature to perform press molding and is cooled to 300° C. or lower at a cooling rate of 10° C./s to 500° C./s to perform hot stamping molding
Data Source
AI summary
According to an exemplary embodiment of the present disclosure, disclosed is an aluminum coated blank that includes a first coated steel sheet; a second coated steel sheet connected to the first coated steel sheet; and a joint portion that connects the first coated steel sheet to the second coated steel plate at a boundary between the first coated steel sheet and the second coated steel sheet.