Tailor Welded Blank Composition for Strong Hot-Pressed Welds
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Solution Overview
Problem
Existing hot-press formed members using Al-Si plated steel sheets face issues with the Al component mixing into the welded joint during laser welding, leading to reduced martensitization and potential fracturing, as existing solutions like partial plating layer removal compromise corrosion resistance.
Innovation Solution
A tailor welded blank with specific Al-based plating layers and a NiCr or CrMn filler wire is used, controlling the content of C, Mn, Ni, Cr, and Al in the welded joint to prevent Al component mixing, ensuring stable austenitization and homogeneous martensite formation, thereby enhancing the physical properties of the welded joint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laser welding is performed on Al-Si plated steel sheets without plating layer removal, then welding process is simple and efficient, but Al component mixes into the welded joint causing reduced martensitization and potential fracturing
Solution Approach 1:
The invention changes the chemical composition parameters of the plating layer by controlling the Si content to 3-15 mass% and adding Fe content of 0.5-10 mass%. This parameter modification prevents Al component mixing during welding while maintaining the desired martensitic structure and strength in the welded joint after hot press forming.
2Reliability
If partial plating layer removal is performed near the weld, then Al component mixing into the welded joint is reduced, but additional equipment is required and corrosion resistance near the weld is reduced
Solution Approach 1:
The invention applies local quality by creating a Fe-alloyed plating layer specifically at the welding area through controlled Fe diffusion during the plating process. This localized Fe enrichment prevents Al mixing at the weld zone without requiring mechanical removal of the plating layer, thus avoiding additional equipment and maintaining corrosion resistance in other areas.
3Reliability
If partial plating layer removal is performed near the weld, then Al component mixing into the welded joint is reduced, but corrosion resistance near the weld is reduced
Solution Approach 1:
The invention modifies the plating layer composition parameters by adding Fe (0.5-10 mass%) and controlling Si (3-15 mass%), which creates a Fe-alloyed plating layer that prevents Al mixing during welding. This compositional change maintains the protective corrosion-resistant properties of the plating layer while ensuring welded joint strength, eliminating the need for plating layer removal.
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 prevents fracture at the welded joint and heat-affected zone, providing high strength and crash safety suitable for automotive applications without compromising corrosion resistance.
Implementation Method 1
irradiating a laser beam together with supply of a filler wire
Implementation Method 2
supply of a filler wire... controlling the content of C, Mn, Ni, Cr, and Al in the welded joint
Implementation Method 3
after heating an Al—Si plated steel sheet to a temperature range of Ac1 or higher, the structure of the parent material consists of martensite by hot forming by a press and rapid cooling
Implementation Method 4
the structure of the parent material consists of martensite by hot forming by a press and rapid cooling
Data Source
AI summary
According to one aspect of the present invention, it is possible to provide a tailor welded blank, a hot press formed part, and a method for manufacturing same, the tailor welded blank having a weld part that can effectively prevent deterioration of properties after hot press forming.