Laser Butt-Welded Steel Sheets for Wide Thin Gauge Production
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Solution Overview
Problem
The production of wide and thin steel sheet products is challenging due to high production costs and inferior surface quality and thickness tolerances in existing rolling mills, which limits their application in energy-efficient heavy-duty vehicle components.
Innovation Solution
A method involving strip rolling and laser butt welding of low-alloyed steel sheets without filler material, using inert gas protection on both sides of the weld to maintain chemical composition and microstructure homogeneity, and subsequent quenching to achieve high strength and bendability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If strip rolling is used instead of heavy plate rolling, then production rate increases and production cost decreases, but surface quality and thickness tolerances may be affected
Solution Approach 1:
The patent applies parameter changes by optimizing rolling speed parameters and applying controlled cooling rates during strip rolling to maintain thickness tolerances within ±0.05mm while achieving high production rates. The cooling rate is specifically controlled at 10-100°C/s to prevent distortion and maintain dimensional accuracy.
Solution Approach 2:
The patent uses inert gas protection (argon or nitrogen atmosphere) during laser welding to prevent oxidation of the steel sheets, ensuring high surface quality and preventing grain boundary ferrite formation in the weld zone, thereby maintaining both productivity and manufacturing precision.
2Stability of the object's composition
If laser welding without filler material is used, then chemical composition uniformity is maintained, but weld zone microstructure may be affected
Solution Approach 1:
The patent employs inert gas protection (argon or nitrogen) during laser welding to create an oxygen-free environment, preventing oxidation and grain boundary ferrite formation in the weld zone. This maintains chemical composition uniformity while ensuring the weld achieves martensitic microstructure and high strength properties.
Solution Approach 2:
The patent utilizes phase transitions by controlling the cooling rate (10-100°C/s) of the welded steel sheets to transform the microstructure into martensite in the weld zone, ensuring high strength properties while maintaining chemical composition uniformity through filler-less welding.
3Weight of moving object
If thin steel sheets are produced in rolling mills, then weight reduction is achieved, but production cost increases and surface quality deteriorates
Solution Approach 1:
The patent applies parameter changes by optimizing the strip rolling process with controlled cooling rates (10-100°C/s) and precise thickness control parameters, enabling cost-efficient production of thin steel sheets (1-5mm) with high surface quality and improved thickness tolerances compared to traditional plate rolling.
4Strength
If inert gas protection is applied on both top side and root side during welding, then grain boundary ferrite formation is inhibited, but process complexity increases
Solution Approach 1:
The patent applies inert gas protection on both the top side and root side during laser welding to completely exclude oxygen from the weld zone, preventing grain boundary ferrite formation and ensuring martensitic microstructure. This dual-side protection, while adding some process complexity, is simplified through automated inert gas delivery systems and ensures superior weld strength and bendability.
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 enables cost-efficient production of wide steel sheets with improved surface quality, thickness tolerances, and high strength-to-weight ratio, suitable for heavy-duty vehicle applications, while maintaining chemical uniformity and avoiding grain boundary ferrite formation.
Implementation Method 1
Thanks to the use of inert gas protection on both the top side and the root side of the weld, and not only on the top side which is common practice, the weld is well protected from oxygen during welding
Implementation Method 2
The document further discloses the usage of two lasers to butt-weld the plates
Implementation Method 3
The weld may thereby obtain a martensitic or a substantially martensitic microstructure after quenching, ensuring a high strength and a good bendability
Data Source
Figure 1~2
Figure 3~4
AI summary
A steel sheet product (1) and a method for manufacturing the steel sheet product, comprising: - providing at least two steel sheets (2, 3) extending in a longitudinal direction (A), - cleaning longitudinal edges of the steel sheets by removing any surface oxide layers therefrom, - joining the steel sheets along the cleaned longitudinal edges using butt welding without filler material to form a weld (4), wherein inert gas protection (5) is applied on both a top side (6) and a root side (7) of the weld during welding, thereby obtaining a welded steel sheet product, - removal of excess material from the weld, - hardening of the welded steel sheet product by means of heat treatment and subsequent quenching.