Method of manufacturing Al-Mg-Si series alloy plate excellent in thermal conductivity and intensity

A method of manufacturing an Al—Mg—Si series alloy plate excellent in thermal conductivity and hardness, the method comprising the steps of:

• preparing Al—Mg—Si series alloy ingot consisting essentially of Si:
• 0.2-0.8 wt %, Mg:
• 0.3-0.9 wt %, Fe:
• 0.35 wt % or less, Cu:0.20 wt % or less and the balance of aluminum and inevitable impurities;
• homogenizing said alloy ingot;
• subjecting said alloy ingot to rough hot rolling to obtain a roughly hot rolled plate;
• subjecting said roughly hot rolled plate to finish hot rolling to obtain a finished hot rolled plate;
• and
• subjecting said finished hot rolled plate to cold rolling to obtain a cold rolled plate,
• wherein one of plural passes preformed at said rough hot rolling is controlled such that material temperature immediately before said one of plural passes is from 350 to 440° C., cooling rate between said one of plural passes and a pass subsequent thereto is 50° C./min or more, material temperature immediately after said one of plural passes is from 250 to 340° C. and plate thickness immediately after said one of plural passes is 10 mm or less,
• wherein said cold rolling is controlled such that rolling reduction is 30% or more, and
• wherein said cold rolled plate is subjected to final aging at a temperature of 180°C. or below, or is not subjected to final aging.