Friction Stir Welded Blanks for Stable Large Metallic Components
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Solution Overview
Problem
Friction stir welding in large metallic components results in undesirable abnormal grain growth (AGG) during heat treatment and forming, leading to reduced mechanical properties and joint efficiency, making it difficult to produce large components with stable microstructures.
Innovation Solution
A method involving a single-sided friction stir welding process with a backing plate that receives the welding tool tip, followed by removal of the backing plate, to maintain a stable microstructure during forming and heat treatment, ensuring high joint efficiency and minimizing AGG.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If friction stir welding is used to join large metallic components, then welding capability and joint formation are achieved, but abnormal grain growth occurs during heat treatment leading to microstructural instability and reduced mechanical properties
Solution Approach 1:
The weld is performed in the solution-treated state before heat treatment, establishing the microstructure in advance. The welding is completed while the material is in a controlled metallurgical state, and then the entire assembly undergoes uniform heat treatment that stabilizes the microstructure without causing abnormal grain growth.
Solution Approach 2:
The patent changes the sequence and timing of thermal parameters. By welding in the solution-treated state and then applying heat treatment to the welded assembly, the thermal parameters are optimized to avoid the abnormal grain growth that occurs when welding is performed after heat treatment or when traditional welding methods are used.
2Stability of the object's composition
If large monolithic plate stock is used to avoid welding, then microstructural stability is maintained, but component size and manufacturing cost increase
Solution Approach 1:
The large component is divided into multiple plates that are joined by friction stir welding. Each plate can be manufactured separately with controlled microstructure, and then joined together using FSW in the solution-treated state followed by heat treatment of the entire assembly, achieving both segmentation benefits and microstructural stability.
Solution Approach 2:
By changing the metallurgical state parameter to solution-treated before welding and applying subsequent heat treatment, the patent enables the use of smaller plate stock while maintaining microstructural stability, thus improving productivity without sacrificing material properties.
3Shape
If friction stir welding is performed after forming and heat treatment, then forming capability is achieved, but weld joint efficiency decreases to 65-96%
Solution Approach 1:
The welding operation is performed as a preliminary action before final heat treatment, in the solution-treated state. This allows the weld to be formed when the material has optimal plasticity and formability, and the subsequent heat treatment stabilizes the microstructure to achieve high joint efficiency exceeding 95%.
Solution Approach 2:
The patent changes the temperature and metallurgical state parameters during welding. By welding in the solution-treated state at elevated temperature and then applying controlled heat treatment, the material properties are optimized to achieve both forming capability and high weld joint efficiency.
4Productivity
If double-sided friction stir welding is used to form large blanks, then blank formation is achieved, but abnormal grain growth occurs in the weld center reducing strength and ductility
Solution Approach 1:
The double-sided friction stir welding is performed in the solution-treated state before heat treatment, establishing the weld structure in advance. The subsequent heat treatment of the entire welded blank stabilizes the microstructure uniformly, preventing abnormal grain growth in the weld center and maintaining strength and ductility above design minimum values.
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 method achieves welds with greater than 95% joint efficiency and stable microstructures, allowing the production of large components with improved mechanical properties, using narrower commodity plates and reducing production costs.
Implementation Method 1
Friction stir welding is a solid-state joining process that provides a method of joining metal components without melting of the workpiece material
Implementation Method 2
subjecting a friction stir weld to an elevated temperature forming operation, followed by solution heat treat & quench
Data Source
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AI summary
A method for forming a large metallic component, a friction stir welded component and a friction stir welded blank are provided. The method includes positioning a first metallic plate and a second metallic plate in an abutting arrangement. The first metallic plate and the second metallic plate have corresponding faying surfaces at a point of abutment. A backing plate is attached spanning the point of abutment adjacent the faying surfaces. The first metallic plate is friction stir welded to the second metallic plate to form a friction stir weld along the faying surfaces. The backing plate receives an end of a friction stir welding tool curing the friction stir welding. The backing plate is removed to form a welded blank. The welded blank is formed into a component form. The component is heat treated and aged to form the large metallic component. The friction stir weld in the welded blank has a stable microstructure having little or no abnormal grain growth during elevated temperature forming, heat treatment and aging.