Liquid-Cooled Jacket Friction Stir Joining to Prevent Cavity Defects
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Solution Overview
Problem
The challenge in manufacturing liquid-cooling jackets lies in joining members made of different aluminum alloys, where the higher hardness of the jacket body results in increased material resistance during friction-stir-welding, leading to insufficient mixing and cavity defects, which reduces the strength of the joined portion.
Innovation Solution
A method involving a jacket body with a bottom portion, peripheral wall, and support pillars made of a first aluminum alloy, and a sealing body with a hole portion made of a second aluminum alloy, using a rotary tool with a base side pin and tip side pin of varying taper angles and a staircase-shaped pin step portion to perform friction-stirring, focusing on the sealing body to prevent mixing with the jacket body and ensure adequate metal flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If friction-stir-welding is performed on members of different aluminum alloys where the jacket body has higher hardness, then the joining process can connect different materials, but the stirring pin receives higher material resistance leading to insufficient mixing and cavity defects
Solution Approach 1:
The patent applies local quality by creating a step portion on the jacket body that locally changes the geometry and material distribution at the butted portion. This step structure allows the softer sealing body material to be positioned where the stirring pin primarily acts, ensuring adequate mixing while the harder jacket body material is positioned where mixing is less critical. The local geometric modification resolves the contradiction between joining different materials and achieving sufficient mixing quality.
2Device complexity
If a conventional rotary tool with single pin is used for friction-stir-welding, then the device complexity is low, but the stirring effectiveness is insufficient when joining different hardness materials
Solution Approach 1:
The patent applies segmentation by dividing the single stirring pin into multiple pins (first stirring pin and second stirring pin) with different functions. The first stirring pin primarily stirs the softer sealing body material, while the second stirring pin assists in stirring the harder jacket body material. This segmentation of the stirring function resolves the contradiction between device simplicity and joining reliability by using multiple pins only where needed.
3Reliability
If the sealing body thickness is increased to prevent metal deficiency, then the joining reliability improves, but the device complexity and material usage increase
Solution Approach 1:
The patent applies preliminary action by pre-forming a step portion on the jacket body before the friction-stir-welding process. This step structure is created in advance to control the material distribution during joining, allowing the sealing body to have sufficient thickness only where needed for reliability, while reducing material usage in areas where the step structure already provides the necessary geometry. The preliminary geometric preparation resolves the contradiction between reliability and material consumption.
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
This method enhances the strength and water-tightness of the joined portion by primarily stirring the second aluminum alloy, reducing the mixing of the first alloy and preventing metal deficiency, thus improving the overall quality of the liquid-cooling jacket.
Implementation Method 1
friction-stirring being performed by inserting the tip side pin and the base side pin of the rotary tool that is rotating into the sealing body and moving the rotary tool along the third butted portion
Implementation Method 2
having the second aluminum alloy of the sealing body flow into the gap
Data Source
AI summary
A liquid cooling jacket is produced by forming a first butted portion where a step side face of a peripheral wall portion and an outer peripheral side face of a sealing body butt each other and a third butted portion where a step side face of a support pillar portion and a hole wall of the hole portion of the sealing body portion butt each other with a gap, and friction-stirring by inserting a tip side pin and a base side pin of a primary joining rotary tool that is rotating into the sealing body and moving the primary joining rotary tool along the third butted portion with an outer circumferential face of the tip side pin being kept off the step side face while having a second aluminum alloy of the sealing body flow into the gap.