Friction Stir Welding of High-Si Steel Sheets Without Roller Scratches
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Solution Overview
Problem
Friction stir welding of high-Si steel sheets in steel sheet production lines often results in roller scratch occurrence due to burrs formed at the joined portion, leading to decreased joint efficiency.
Innovation Solution
A friction stir welding method involving a joining process, followed by surface working to remove burrs with a maximum thickness reduction of 5.0% or less, and a heating process with a temperature range of 400 °C to 1000 °C to control deformation strain, ensuring the hardness of the surface layer region is 95% to 115% of the base metal hardness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If friction stir welding is applied to high-Si steel sheets to improve productivity and joint efficiency, then manufacturing efficiency is improved, but roller scratch occurrence increases due to burr formation at the joined portion
Solution Approach 1:
The patent applies preliminary surface working (grinding or polishing) to the joined portion after friction stir welding to remove burrs before the steel sheets are processed further. This preliminary action prevents the burrs from causing roller scratches downstream, resolving the contradiction between maintaining high joint efficiency and preventing roller scratch occurrence
Solution Approach 2:
The patent controls specific process parameters including limiting the depth of surface working to 5% or less of the steel sheet thickness and controlling the heating temperature to 400-1000°C. These parameter changes allow burr removal while preventing excessive material removal that would compromise joint strength, thus maintaining productivity while eliminating roller scratches
2Object-affected harmful factors
If surface working is performed to remove burrs and prevent roller scratches, then roller scratch occurrence is reduced, but joint efficiency decreases due to excessive material removal
Solution Approach 1:
The patent precisely controls the surface working depth parameter to be 5% or less of the steel sheet thickness. This parameter control ensures sufficient burr removal to prevent roller scratches while removing minimal material to preserve joint strength and efficiency
Solution Approach 2:
The patent replaces aggressive mechanical burr removal with controlled heating (400-1000°C) that softens and redistributes the burr material, reducing its harmful effects without significant material loss. This substitution maintains joint integrity while preventing roller scratches
3Manufacturing precision
If heating is applied to control deformation strain and improve joint quality, then microstructural deformation is controlled, but additional processing time is required
Solution Approach 1:
The patent merges the heating process with the existing production line workflow, applying heat during or immediately after the friction stir welding operation. This integration allows deformation control without adding significant separate processing time, as the heating is performed in-line rather than as a separate post-processing step
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
Prevents roller scratch occurrence and achieves excellent joint efficiency by effectively removing burrs and controlling microstructural deformation in high-Si steel sheets.
Implementation Method 1
The rotating tools are then pressed against the front surface and the back surface of the material to be joined, and are moved in a joining direction while being rotated. This allows the metal sheets to be softened by the frictional heat between the rotating tools and the material to be joined
Data Source
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AI summary
A friction stir welding method is provided that makes it possible to prevent roller scratch occurrence and obtain excellent joint efficiency even when high-Si steel sheets are used as material to be joined. The method includes a joining process, a surface working process, and a heating process, and a maximum thickness reduction of a joined member in the surface working process is 5.0 % or less of a thickness of the material to be joined, and further, a maximum arrival temperature in the heating process is 400 °C or higher and 1000 °C or lower.