Heat treatment manner and AlMgSi based alloy material null of AlMgSi based alloy

摘要

PROBLEM TO BE SOLVED: To control the variation of proof stress value in a narrow range by subjecting an Al-Mg-Si-based alloy material contg. specified weight ratios of Mg and Si, and the balance Al with inevitable impurities to holding under heating at a specified temp. for a specified time specified times and executing an artificial aging treatment in an overaging region. ;SOLUTION: An Al-Mg-Si-based alloy contg., by weight, 0.30 to 0.70% Mg, 0.15 to 0.70% Si, and the balance Al with inevitable impurities is subjected to holding under heating at ≥190°C for ≥6 hr for one or more times and is subjected to artificial aging treatment in an overaging region. Preferably, this is a method for controlling proof stress in which the holding under heating is executed ≥ two times, also, the 1st heating is executed at a temp. lower than that in the heating on and after the 2nd time, moreover, Si is contained by the amt. surplus to the forming amt. of Mg2Si, furthermore, the Al-Mg-Si- based alloy material is composed of an extruded material, and the material temp. directly after the extrusion is controlled to 480°C. In this way, the variation of the proof stress is small, so that the selection of the artificial aging treating conditions for obtaining the objective proof stress value is made easy.;COPYRIGHT: (C)2000,JPO