Friction Stir Welded Pipe Corrosion Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Metals used in fluid conveying systems, especially in water environments, face significant corrosion issues, particularly at weld joints, which can compromise the long-term operational integrity of the pipes.
Innovation Solution
The use of friction stir welding (FSW) to join metal pipe sections, creating a corrosion-resistant seam that extends longitudinally along the pipe, allowing for the construction of large-diameter fluid conveying pipes with reduced galvanic corrosion and retention of material properties, and enabling the use of various materials like aluminum, titanium, and steel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional welding methods are used to join metal pipe sections, then the pipes can be constructed and assembled, but significant corrosion occurs at the weld joints compromising long-term operational integrity
Solution Approach 1:
The patent applies friction stir welding which fundamentally changes the welding parameters and process mechanism compared to conventional welding. Instead of melting and fusing metals with heat, FSW uses mechanical friction and stirring to create a metallurgical bond in the solid state, transforming the welding process parameters to eliminate the harmful effects of conventional welding-induced corrosion
Solution Approach 2:
The patent replaces the thermal-mechanical system of conventional welding (heat + pressure) with a purely mechanical system (friction + stirring + pressure). The friction stir welding tool uses rotational mechanical energy to generate friction heat locally while simultaneously stirring and forging the metals together, substituting the conventional heat-based welding mechanism with a mechanics-based approach that produces corrosion-resistant joints
2Reliability
If friction stir welding is used to join pipe sections, then corrosion resistance at weld joints is improved, but the manufacturing process complexity increases
Solution Approach 1:
The patent segments the pipe construction into separate pipe sections that are joined through FSW. This segmentation allows for standardized manufacturing of individual sections with controlled FSW joints, making the overall manufacturing process more manageable despite the complexity of the FSW process itself. The pipe is divided into segments that can be manufactured and assembled systematically
Solution Approach 2:
The friction stir welding tool acts as an intermediary device that facilitates the joining process. The specialized FSW tool with its rotating probe and controlled movement system serves as a mediator between the pipe sections, enabling the complex welding operation to be performed systematically and repeatably, thereby managing the manufacturing complexity
3Area of moving object
If large-diameter pipes are constructed using multiple pipe segments, then the required pipe diameter is achieved, but the number of weld joints increases
Solution Approach 1:
The patent divides the large-diameter pipe into multiple manageable pipe sections that can be individually manufactured and then joined through FSW. This segmentation enables the construction of large-diameter pipes that would be impossible to manufacture as single pieces, while the FSW joining method ensures that each joint maintains the same high corrosion resistance as the base metal
Solution Approach 2:
The patent achieves homogeneity in material properties and corrosion resistance across all pipe sections and joints. By using FSW, the weld joints have metallurgical properties and corrosion resistance comparable to the base metal, creating a homogeneous structure throughout the entire pipe assembly despite being constructed from multiple segments
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
FSW reduces corrosion at weld joints, enhances material properties, and allows for the creation of lightweight, large-diameter pipes suitable for applications like ocean thermal energy conversion plants, with adjustable buoyancy and flexible connecting rings for stress relief.
Implementation Method 1
The use of friction stir welding (FSW) to join two metallic objects at a weld joint is known
Implementation Method 2
there is little or no corrosion that occurs, while significant corrosion occurs on the metal objects at locations outside of the FSW joint in the base metal alloy
Data Source
AI summary
Fluid conveying pipes and processes of forming such pipes using friction stir welding. The fluid conveying pipes are formed from a pipe section that includes a first barrel coaxially and concentrically disposed within a second barrel. The first barrel and the second barrel are each formed from one or more sections or plates where longitudinal extending facing edges of the plates are friction stir welded (FSW) together along a seam(s) that extends longitudinally from the first end to the second end thereof. A plurality of the pipe sections can be connected together end to end using circumferential FSW seams to form a pipe.