6xxx Aluminum Strip Processing for Strength-Formability Balance
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Solution Overview
Problem
6xxx aluminum alloys face challenges in improving strength and formability without degrading other properties, particularly for automotive applications requiring sheets with good formability and high strength after paint bake thermal treatment.
Innovation Solution
A method of manufacturing 6xxx aluminum alloy strips through a continuous in-line process involving solution heat treating, quenching, and optional additional steps like off-line cold rolling, tension leveling, and coiling, followed by artificial aging to achieve improved strength and formability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the alloy composition is modified to improve strength, then tensile yield strength increases, but formability deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the alloy composition parameters (Si: 0.8-1.25 wt%, Mg: 0.2-0.6 wt%, Cu: 0.5-1.15 wt%, Mn: 0.01-0.20 wt%, Fe: 0.01-0.3 wt%) and processing parameters (solution heat treatment temperature: 510-571°C, quenching temperature: 37.8-93.3°C) to achieve an optimal balance between strength and formability. This systematic parameter optimization allows the alloy to attain tensile yield strength of 160-350 MPa while maintaining FLD values of 28.0-35.0, resolving the contradiction between strength improvement and formability preservation.
2Strength
If solution heat treatment temperature is increased to improve strength, then tensile yield strength increases, but risk of incipient melting increases
Solution Approach 1:
The patent implements parameter changes by establishing an optimized solution heat treatment temperature range of 510-571°C, which is sufficiently high to achieve complete dissolution of second phase particles and maximize strength (160-350 MPa), yet remains below the incipient melting point of the alloy. This precise temperature control enables the patent to extract maximum strengthening benefit while avoiding the harmful effect of incipient melting, thus resolving the technical contradiction.
3Strength
If rapid quenching is applied to preserve solid solution and improve strength, then tensile yield strength increases, but internal stress and distortion increase
Solution Approach 1:
The patent applies parameter changes by optimizing the quenching process parameters, specifically controlling the quenching temperature to 37.8-93.3°C and selecting appropriate quenching media (water, air, or oil). This optimized quenching regime enables rapid cooling sufficient to preserve the solid solution and achieve high strength (160-350 MPa), while minimizing thermal gradients and resulting internal stresses, thus resolving the contradiction between strength improvement and stress reduction.
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 method results in an aluminum alloy strip with enhanced combination of strength and formability, suitable for automotive applications, with tensile yield strength ranging from 160 to 350 MPa and forming limit diagram (FLD) values of 28.0 to 35.0, while maintaining corrosion resistance.
Implementation Method 1
the term 'solution heat treatment' refers to a metallurgical process in which the metal is held at a high temperature so as to cause second phase particles of the alloying elements to at least partially dissolve into solid solution
Implementation Method 2
After the solution heat treating and quenching, the 6xxx aluminum alloy strip may be (v) artificially aged
Implementation Method 3
the 6xxx aluminum alloy strip may be (v) artificially aged (e.g., via a paint bake)
Implementation Method 4
the term 'anneal' refers to a heating process that causes recovery and/or recrystallization of the metal to occur (e.g., to improve formability)
Data Source
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AI summary
New 6xxx aluminum alloy strips having an improved combination of properties are disclosed. The new 6xxx new aluminum alloy strips are rolled to a target thickness in-line via at least a first rolling stand and a second rolling stand. In one approach, the 6xxx new aluminum alloy strips may contain 0.8 to 1.25 wt. % Si, 0.2 to 0.6 wt. % Mg, 0.5 to 1.15 wt. % Cu, 0.01 to 0.2 wt. % manganese, 0.01 to 0.2 wt. % iron; up to 0.30 wt. % Ti; up to 0.25 wt. % Zn; up to 0.15 wt. % Cr; and up to 0.18 wt. % Zr.