Dissimilar Sheet Welding Using Vaporized Foil Interlocks
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Solution Overview
Problem
Traditional friction stir welding technologies face difficulties in joining aluminum sheets with dissimilar materials like steel, often resulting in welds that are not suitable for structural use due to stress corrosion cracking.
Innovation Solution
A method involving resistive spot welding with metal foils, where a metal foil is vaporized to project a portion of one sheet through cut-out sections of another sheet, forming a weld, and optionally using a transition material or raising a sheet's edge for improved alignment and consistency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional friction stir welding is used to join aluminum sheets with dissimilar materials like steel, then the welding process can be performed with existing equipment, but the welds suffer from stress corrosion cracking and are not suitable for structural use
Solution Approach 1:
A metal foil intermediary is introduced between the aluminum sheet and steel sheet. The foil is vaporized by resistive heating to create a metallic bridge that projects aluminum material through cut-out sections in the steel sheet, forming a mechanical interlock weld that eliminates stress corrosion cracking
Solution Approach 2:
The invention changes the physical state of the metal foil from solid to vapor through controlled resistive heating, using this phase transition to drive the projection of aluminum material through the steel sheet and create a reliable weld structure
2Strength
If traditional resistive spot welding is used to join dissimilar materials, then the process is simple, but the welds are not strong enough for structural applications
Solution Approach 1:
The welding process is segmented into distinct stages: resistive spot welding of the foil to create localized heating zones, vaporization of the foil at these zones, and projection of aluminum material through cut-out sections in the steel sheet. This segmentation creates a mechanical interlock structure with superior strength and structural suitability
Solution Approach 2:
The invention creates a composite weld structure consisting of aluminum, vaporized metal foil, and steel materials interconnected through the projection mechanism. This composite structure achieves the strength and reliability required for structural applications by combining the advantages of different materials
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 achieves a strong mechanical interlock suitable for structural use, eliminating the need for specialized equipment and allowing for efficient welding of dissimilar materials like aluminum and steel without stress corrosion cracking.
Implementation Method 1
applying a current to a stack of sheets to resistively spot weld a first sheet of the stack of sheets to a second sheet of the stack of sheets
Implementation Method 2
vaporizing the at least one metal foil to project at least one portion of the third sheet through the at least one cut out section of the second sheet to the first sheet to form a weld
Data Source
AI summary
A method for welding a stack of sheets having a plurality of sheets of different materials is provided. In an aspect, the stack of sheets includes an aluminum sheet and a galvanneal steel sheet. In an aspect, the method includes resistively spot welding the galvanneal sheet to a hot-stamped steel sheet placed between the aluminum sheet and the galvanneal sheet, the sheet of hot-stamped steel including stress relief sections. The method further includes placing a metal foil on the aluminum sheet and vaporizing the metal foil to project portions of the aluminum sheet through the stress relief sections of the hot-stamped steel sheet to weld the portions of the aluminum sheet to the galvanized steel sheet. In another aspect, the method includes placing the metal foil on a raised portion of the aluminum sheet and projecting the raised portion of the aluminum onto the galvanneal steel sheet.