Friction Stir Welding with Overlay Backfill for Corrosion Protection
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Solution Overview
Problem
Joining metals with different properties using friction stirring leads to electric corrosion at the joined portion when exposed to water, necessitating complex anti-corrosion treatments.
Innovation Solution
A friction stir welding apparatus with a replaceable joining and backfilling probe that forms a joint hole and backfills it with an overlay portion, respectively, to cover the material adjacent portion and prevent electric corrosion without additional sealing steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If friction stirring is used to join metals with different properties, then energy consumption is reduced compared to arc welding, but electric corrosion occurs at the joined portion when exposed to water
Solution Approach 1:
The invention utilizes the frictional heat generation mechanism inherent in friction stir welding to achieve a dual purpose: joining the metals and simultaneously creating a protective overlay structure. The frictional heat softens the material adjacent portion, which is then extruded to form an overlay that covers the vulnerable material adjacent portion, converting the thermal effect (which could cause unwanted exposure) into a protective mechanism.
Solution Approach 2:
The overlay portion is formed during the joining process itself, before the joint is exposed to water or corrosive environments. By creating the protective cover as part of the welding process rather than as a subsequent treatment, the material adjacent portion is preemptively protected from electric corrosion without requiring additional sealing steps.
2Object-affected harmful factors
If anti-corrosion treatment is applied to prevent electric corrosion, then corrosion protection is achieved, but the joining process becomes more complex
Solution Approach 1:
The invention merges the joining function and the anti-corrosion protection function into a single integrated process. The friction stir welding operation simultaneously creates the metallurgical bond and forms the protective overlay structure, eliminating the need for separate anti-corrosion treatment steps such as chemical conversion treatments or waterproof sealer applications.
Solution Approach 2:
The friction stir welding process is made multi-functional by enabling it to perform both joining and protective coating formation. The probe structure and process parameters are designed to extrude the material adjacent portion into an overlay that serves as both a structural element and a protective barrier against electric corrosion.
3Device complexity
If the material adjacent portion is exposed at the joined portion, then the joining process is simpler, but electric corrosion occurs when water contacts the joined portion
Solution Approach 1:
The frictional heat, which is inherent to the friction stir welding process and could potentially cause unwanted material exposure, is converted into a beneficial effect. The heat softens the material adjacent portion, enabling it to be extruded as a protective overlay that covers the previously exposed material adjacent portion, thereby improving corrosion resistance.
Solution Approach 2:
The joining process itself generates the protective overlay structure through self-service. The frictional heat and mechanical action during welding automatically form the overlay portion from the material adjacent portion, without requiring external intervention or additional processing steps to create the protective barrier.
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
Suppresses electric corrosion by covering the material adjacent portion, improving joint strength, and eliminating the need for additional waterproof sealing, while reducing the complexity of the joining process.
Implementation Method 1
forms a joint hole in the plate members softened by frictional heat generated by a joining surface of the joining probe coming into sliding contact with the plate members
Implementation Method 2
backfills the joint hole with the overlay portion softened by frictional heat generated by a backfilling surface of the backfilling probe coming into sliding contact with the overlay portion
Data Source
AI summary
A friction stir welding apparatus includes an anvil, a probe, and a shoulder member. The probe includes: a joining probe which advances toward plate members of a stacked body, forms a joint hole in the plate members softened by frictional heat generated by a joining surface of the joining probe coming into sliding contact with the plate members and joins the plate members, and forms an overlay portion protruding in a bank shape from a plate surface around the joint hole along an inner peripheral surface of the shoulder member; and a backfilling probe which advances toward the plate members, and backfills the joint hole with the overlay portion softened by frictional heat generated by a backfilling surface of the backfilling probe coming into sliding contact with the overlay portion. The joining probe and the backfilling probe are disposed to be replaceable with each other.