A heat treatment method that improves the formability and bake hardenability of 6XXX series aluminum alloy sheets

Abstract

The present invention provides a heat treatment method that may improve the formability and bake hardenability of 6XXX series aluminum alloy and remarkably lengthen the lasting time of bake hardenability. After solution hardening and before stamping, 6XXX series aluminum alloy sheets will undergo heat treatment for a certain period of time. The technical solution of the present invention facilitates automatic operation, can be easily realized and may save energy and equipment investment. After 6XXX series aluminum alloy sheets are treated by this method after solution hardening, its formability and bake hardenability are improved obviously. More importantly, after heat treatment by the method of the present invention, the lasting time of the bake hardenability of aluminum alloy sheets is greatly lengthened to 3-4 months, even 6 months. The above advantages will promote the substitution of aluminum alloy sheets for steel sheets to reduce car weight, thus saving energy and reducing emission while achieving desirable economic benefit.

Description

technical field [0001] The invention relates to the technical field of preheating treatment of aluminum alloy outer body plates for automobiles. The method can improve the workability, bake hardening performance and retention time of aluminum alloy plates. Background technique [0002] In the face of energy shortage, it is imperative to reduce the weight of automobiles. Aluminum alloy materials have the characteristics of high specific strength, good machinability, excellent welding performance and corrosion resistance, high impact toughness, and high-speed extrusion into various profiles with complex structures. They have many advantages in terms of energy saving, emission reduction and collision safety. Therefore, aluminum alloys have been widely used in the modern automobile industry, among which the aluminum alloys for automobile body panels are mainly 6016 and 6111 alloys. The production process of aluminum alloy sheets is roughly as follows: 1. Melting raw materials, ...

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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