Heat treatment method for improving shaping property and bake-hardening property of 6XXX series aluminum alloy sheet

Abstract

The invention provides a heat treatment method for improving shaping property and bake-hardening property of a 6XXX series aluminum alloy sheet and greatly prolonging bake-hardening property keeping time. The 6XXX series aluminum alloy sheet undergoes heat treatment for some time after solution quenching treatment and before stamping forming. The technical scheme of the invention makes automated operation convenient and can be easily realized and save energy and equipment investments. After the 6XXX series aluminum alloy sheet undergoing the solution quenching treatment is treated by the method provided by the invention, the shaping property and the baking varnish strengthening property of the 6XXX series aluminum alloy sheet are obviously improved, and more importantly, by the preheat treatment of the method, the bake-hardening property keeping time of the aluminum alloy sheet is greatly prolonged to 3 to 4 months, even 6 months; due to the advantages, the aluminum alloy sheet is enabled to replace the steel plate so as to reduce the weight of an automobile body; and thus, the aim of saving energy and reducing emission while creating good economic benefits is also achieved.

Description

Technical field [0001] The invention relates to the technical field of pre-heat treatment of aluminum alloy outer body plates for automobiles. This method can improve the workability, bake hardening performance and retention time of aluminum alloy plates. Background technique [0002] Energy shortages make it imperative to reduce the weight of automobiles. Aluminum alloy materials have the characteristics of high specific strength, good processability, excellent welding performance and corrosion resistance, high impact toughness, and high-speed extrusion into various shapes with complex structures. They have many advantages in energy saving, emission reduction and collision safety. Advantages, therefore, aluminum alloys have been widely used in the modern automobile industry. Among them, aluminum alloys for automobile body panels are mainly 6016 and 6111 alloys. The production process of aluminum alloy plates is roughly as follows: 1. Melt raw materials, directly cold cast into ...

AI Technical Summary

Problems solved by technology

However, the strength of 6016 aluminum alloy after painting and baking is lower than that of 6111 aluminum alloy, which greatly limits the application of 6016 aluminum alloy in automobile body

World Patent No. WO 98 / 59086 published in 1998 discloses a preheating method in which coils are rapidly cooled to 65-75°C and then cooled to room temperature at a rate of 2°C / h. In this method, accurate cooling speed is difficult to achieve and It has limited ability to improve the paint strengthening of the board

Patent No. WO 00 / 70115 published in 2000 and Patent No. WO 2005 / 071127 published in 2005 disclose a short-time annealing method at 180-300°C before baking to improve its workability and bake hardenability, but These two methods also have limited ability to improve bake hardening and also need to add medium temperature (300°C) heat treatment equipment in the automobile factory

However, the most critical thing is that the various pretreatment methods proposed before maintain the bake hardening performance for a short time (≤1month) or have not been studied.

There is no systematic research on the relationship between pretreatment process and processing formability, bake hardening and its retention time

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