Dissimilar Metal Friction Stir Joining With Single-Side Pin Insertion
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Solution Overview
Problem
Conventional friction stir welding faces challenges in joining metal members with significantly different softening temperatures, leading to issues like excessive burr generation, increased frictional resistance, and potential joining defects due to uneven heat input and frictional stress.
Innovation Solution
A method involving a rotary tool with a stirring pin inserted only into the metal member with the lower softening temperature, where the second metal member with a higher melting temperature is positioned as a shear side to control heat input and reduce frictional resistance, preventing excessive burr formation and ensuring a strong bond.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional friction stir welding is used to join metal members with significantly different softening temperatures, then the joining process can be performed, but excessive burr generation occurs and joining defects appear due to uneven heat input
Solution Approach 1:
The patent applies local quality by inserting the stirring pin only into the metal member with lower softening temperature (first metal member) while keeping the metal member with higher softening temperature (second metal member) as a shear side without direct pin insertion. This localized differentiation of treatment allows the softer metal to receive frictional heating and plasticization where needed, while the harder metal serves as a shear surface, preventing excessive burr generation and joining defects that occur when both metals are treated uniformly.
2Strength
If the rotary tool is inserted into both metal members during friction stir welding, then joining can be achieved, but frictional resistance increases and load on the tool increases
Solution Approach 1:
The patent reduces frictional resistance and tool load by applying different interaction modes to different metal members: the stirring pin is inserted only into the first metal member (lower softening temperature) to generate necessary frictional heat and plasticization, while the second metal member (higher softening temperature) serves purely as a shear side. This localized differentiation eliminates unnecessary frictional contact between the tool and the harder metal, reducing overall frictional resistance and tool load while maintaining joining strength.
3Reliability
If uniform heat input is applied to both metal members, then the joining process can proceed, but uneven softening occurs leading to joining defects
Solution Approach 1:
The patent achieves uniform softening and reliable joining by applying localized quality control: the stirring pin is inserted only into the first metal member with lower softening temperature, providing concentrated frictional heat input where it is most needed. The second metal member with higher softening temperature serves as a shear side that receives heat indirectly through conduction and shear deformation. This differentiated approach ensures each metal member receives appropriate heat input relative to its properties, achieving uniform softening across the interface without the joining defects caused by uneven softening.
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 approach effectively reduces burr generation, minimizes load on the rotary tool, and enhances the joining process by maintaining optimal heat distribution, resulting in a stronger and more reliable bond between dissimilar metal members.
Implementation Method 1
friction stirring is performed to a butting interface between a couple of metal members with a stirring pin and a shoulder portion of a rotary tool
Implementation Method 2
difference in the softening temperatures of the metal members is large, it is difficult to properly join the metal members at the butting interface
Data Source
Figure 1A~1B
Figure 2A~2C
Figure 3~4
AI summary
Provided is a joining method capable of suitably joining metal members of different kinds. The joining method is characterized by including a preparatory step of preparing a first metal member (1) having a first upper surface (1b), a first lower surface (1c) and a first inclined surface (1a) connecting the first upper surface (1b) and the first lower surface (1c), and a second metal member (2) having a second upper surface (2b), a second lower surface (2c), and a second inclined surface (2a) connecting the second upper surface (2b) and the second lower surface (2c), the second metal member having a higher melting temperature than the first metal member (1); a butting step of forming a butting interface (J) by butting the first inclined surface (1a) and the second inclined surface (2a); and a joining step of joining the first metal member (1) and the second metal member (2) by moving the rotary tool (F) along the butting interface (J) while the rotary tool (F) being rotated is inserted only from the first upper surface (1b) and only the stirring pin (F2) is in contact with at least the first metal member (1).