PROCESS FOR PRODUCING HEAT-TREATABLE SHEET ARTICLES

摘要

A process of heat treating a sheet article made of a 6000 series aluminum alloy to achieve good "paint-bake response" that is substantially unaffected by natural aging. The process comprises heating the alloy sheet article at a solutionizing temperature followed by cooling the alloy sheet article. The cooling involves the following steps: (1) cooling from said solutionizing temperature to a temperature in the range of 150 - 250 ~C at a rate greater than or equal to about 4 ~C per second; (2) further cooling the alloy to a temperature in the range of ambient to 100 ~C at a rate of 20 to 30 ~C (preferably about 25 ~C) per minute; and (3) further cooling the alloy sheet article having a temperature of 55 ~C or more after step (2) to ambient temperature at a rate of less than 2 ~C per hour. Alloy sheet articles suitable for use in the fabrication of automobile skin part can be produced in this way.