Friction Stir Welding Apparatus with Preheating for Structural Steel
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Solution Overview
Problem
Friction stir welding of structural steel faces challenges with plastic flow defects due to insufficient heating, leading to low welding speed and joint strength, and excessive heating causes microstructure changes that deteriorate weld quality.
Innovation Solution
A friction stir welding apparatus with a rotary tool and a heating device that preheats the steel sheets using a high-energy-density source like a laser, controlling surface temperature and depth to ensure sufficient plastic flow without altering the microstructure, followed by a combined heating and cooling process to enhance weld joint properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If friction stir welding is performed on structural steel without additional heating, then the welding process can be completed, but plastic flow defects occur due to insufficient heating of the workpieces
Solution Approach 1:
The patent applies preliminary heating action by introducing a heating device that preheats the steel sheets before the rotary tool arrives. This preliminary action raises the temperature of the workpiece to an optimal range that enables sufficient plastic flow and eliminates defects while the rotary tool performs welding, thereby resolving the contradiction between achieving reliable welds and eliminating manufacturing defects.
Solution Approach 2:
The patent changes the temperature parameter of the workpiece by introducing controlled heating. By adjusting the heating temperature and duration, the steel sheets reach an optimal temperature range that enables proper plastic flow during welding. This parameter change resolves the contradiction by providing the necessary thermal conditions for defect-free welding without altering the fundamental welding process.
2Ease of operation
If additional heating is applied to improve plastic flow, then welding workability improves, but excessive heating causes microstructure changes that deteriorate weld quality
Solution Approach 1:
The patent implements feedback control by monitoring the temperature of the steel sheets during heating and adjusting the heating power accordingly. The system maintains the temperature within an optimal range that improves plastic flow and welding workability while preventing excessive heating that would cause detrimental microstructure changes. This feedback mechanism resolves the contradiction between ease of operation and weld quality.
Solution Approach 2:
The patent applies dynamic control to the heating process, where the heating power and duration are adjusted based on real-time temperature measurements and welding progress. This dynamic approach allows the system to optimize plastic flow conditions while automatically preventing overheating, thereby resolving the contradiction between improved welding workability and maintained weld quality.
3Reliability
If friction stir welding is performed on structural steel, then solid-state welding advantages are achieved, but welding speed is limited due to high hardness and low ductility of steel
Solution Approach 1:
The patent changes the temperature parameter of the steel sheets by introducing controlled heating before welding. This temperature increase improves the ductility and reduces the hardness of the steel, enabling faster welding speeds while maintaining the advantages of solid-state welding. The parameter change resolves the contradiction between reliability and productivity.
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 apparatus improves welding workability by eliminating plastic flow defects and maintaining high joint strength, reducing microstructure changes and increasing welding speed while maintaining the quality of the weld joint.
Implementation Method 1
the steel sheets are softened by frictional heat generated between the workpieces and the rotary tool
Implementation Method 2
the softened portion is stirred with the rotary tool to produce plastic flow
Data Source
AI summary
A friction stir welding apparatus that includes a rotary tool and a heating device. The heating device is placed in front of the rotary tool to heat steel sheets that are used as a workpiece. The rotary tool is moved in the welding direction so that steel sheet is softened by frictional heat. Additionally, the surface temperature, the area, and the position of the heated region during the heating process are strictly controlled. The heating of the steel sheets by the welding apparatus provides sufficient strength and good welding workability by advantageously eliminating plastic flow defects generated due to insufficient heating of workpieces.