Pierce Metal Structure for Crack-Resistant Aluminum-to-Steel Joining
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Solution Overview
Problem
The existing methods for spot welding aluminum die-cast members to iron-based members often result in cracks due to low ductility and misalignment issues, leading to insufficient joining and increased costs from thermal treatments.
Innovation Solution
A pierce metal with a shaft and head, featuring a dome-shaped tip surface and a hollow shape, which penetrates through the aluminum die-cast member, allowing for concentrated current density and reduced thermal stress, thereby preventing cracks and ensuring effective joining.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional spot welding is used to join aluminum die-cast members to iron-based members, then joining is achieved, but cracks occur due to low ductility and misalignment issues
Solution Approach 1:
The pierce metal acts as an intermediary component between the aluminum die-cast member and the iron-based member. It includes a shaft that penetrates the aluminum member and a head that contacts the iron-based member, enabling spot welding through the pierce metal head while the shaft provides mechanical anchoring in the aluminum member. This intermediary structure prevents direct welding between dissimilar materials, thereby reducing crack occurrence.
Solution Approach 2:
The joining system is segmented into three distinct components: the aluminum die-cast member, the pierce metal (with shaft and head), and the iron-based member. This segmentation allows each component to be optimized for its specific function - the shaft for penetration and mechanical fixation, the head for electrical contact and welding, and the separate materials for their respective structural roles, thereby improving overall joining reliability.
2Reliability
If thermal treatment is applied to improve ductility and prevent cracks, then joining quality improves, but manufacturing cost and process complexity increase
Solution Approach 1:
The invention replaces the need for thermal treatment processes with a mechanical solution - the pierce metal structure. Instead of applying heat to improve ductility and prevent cracks, the design uses the pierce metal's shaft-head configuration to achieve reliable joining through mechanical penetration and electrical contact welding, thereby simplifying the manufacturing process.
3Strength
If the shaft outer peripheral surface contacts the through-hole completely, then fixation is improved, but misalignment issues and crack risk increase
Solution Approach 1:
The shaft is designed with non-uniform outer peripheral surface characteristics - certain portions contact the through-hole for fixation while other portions are configured to avoid contact. This local differentiation allows the shaft to provide adequate mechanical anchoring at contact points while preventing excessive constraint that could lead to misalignment and cracking during the welding process.
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 pierce metal effectively joins aluminum die-cast and iron-based members with reduced crack occurrence and improved nugget formation, even under misalignment conditions, enhancing the quality and efficiency of the joining process.
Implementation Method 1
the outer peripheral surface is configured to come into contact with a through-hole of the aluminum die-cast member, upon joining the aluminum die-cast member and the iron-based member together. The head and the iron-based member which is in contact with the protruded tip surface are configured to be held under pressure by a pair of weld electrodes and are configured to be applied with electric power by the pair of weld electrodes to perform spot welding
Implementation Method 2
The head and the iron-based member which is in contact with the protruded tip surface are configured to be held under pressure by a pair of weld electrodes
Implementation Method 3
Causing the shaft to penetrate the aluminum alloy member from a tip surface of the protrusion of the shaft allows the pierce metal to be swaged and thus fixed to the aluminum alloy member owing to a swaging part provided on the head
Data Source
AI summary
A pierce metal includes a head and a shaft. The shaft is configured to penetrate through an aluminum die-cast member with a protruded tip surface of the shaft being exposed from the aluminum die-cast member, and an outer peripheral surface of the shaft is configured to come into contact with a through-hole of the aluminum die-cast member, upon joining the aluminum die-cast member and the iron-based member together. The head and the iron-based member in contact with the protruded tip surface are configured to be held under pressure and applied with electric power by weld electrodes to perform spot welding of the protruded tip surface and the iron-based member, upon joining the aluminum die-cast member and the iron-based member together. The outer peripheral surface includes a non-contact part configured to come into non-contact with the through-hole in a state in which the shaft is penetrated through the aluminum die-cast member.