Kobe Steel, Ltd.

Kabushiki Kaisha Kobe Seiko Sho

Yukimasa Miyata

Shinji Yoshihara

Takahiro Shikama

Minwoo Kang

An aluminum alloy extruded material in relation with the present invention is with high strength by die quench air cooling and excellent in SCC resistance. The aluminum alloy extruded material is an Al&#x2014;Zn&#x2014;Mg-based aluminum alloy extruded material for structural member for automobiles such as a bumper reinforce, a door guard bar and the like which satisfies three expressions of 5.0&#x2264;[Zn]&#x2264;7.0, [Zn]/5.38&#x3c;[Mg]&#x2264;[Zn]/5.38+0.7, and [Zn]+4.7[Mg]&#x2264;14, where [Mg] represents mass % of Mg and [Zn] represents mass % of Zn, and contains at least either one element of Cu: 0.1-0.6 mass % and Ag: 0.01-0.15 mass %, Ti: 0.005-0.05 mass %, and at least one element out of Mn: 0.1-0.3 mass %, Cr: 0.05-0.2 mass %, Zr: 0.05-0.2 mass %.

High strength aluminum alloy extruded material excellent in stress corrosion cracking resistance

To obtain an Al&#x2014;Mg&#x2014;Si based aluminum alloy extruded material with a smooth surface and no burning without inhibiting the productivity. An aluminum alloy billet includes: Si: 2.0 to 6.0% by mass; Mg: 0.3 to 1.2% by mass; and Ti: 0.01 to 0.2% by mass, a Fe content being restricted to 0.2% or less by mass, with the balance being Al and inevitable impurities. The aluminum alloy billet is subjected to a homogenization treatment by keeping at 500 to 550&#xb0; C. for 4 to 15 hours. The billet is forcibly cooled to 250&#xb0; C. or lower at an average cooling rate of 50&#xb0; C./hr or higher. Then, the billet is subjected to hot-extruding at an extrusion rate of 3 to 10 m/min by being heating at 450 to 500&#xb0; C. The extruded material is forcibly cooled at an average cooling rate of 50&#xb0; C./sec or higher and then subjected to an aging treatment. The extruded material can be manufactured that has its surface having a ten-point average roughness Rz of 80 &#x3bc;m or less.

Free-machining aluminum alloy extruded material with reduced surface roughness and excellent productivity

A casted ingot of a heat treatment type Al&#x2014;Zn&#x2014;Mg series aluminum alloy comprising Zn: 4.0-8.0% by mass, Mg: 0.5-2.0% by mass, Cu: 0.05-0.5% by mass, Ti: 0.01-0.1% by mass, and any one or more of Mn: 0.1-0.7% by mass, Cr: 0.1-0.5% by mass and Zr: 0.05-0.3% by mass, and the balance being aluminum and incidental impurities is extruded at a homogenization treatment temperature after a homogenization treatment without cooled, and a resulted extruded material is die quenched at a cooling rate equal to or more than 100&#xb0; C./min and then subjected to an artificial aging treatment, wherein the homogenization treatment is carried out by heating to the homogenization treatment temperature as 430-500&#xb0; C. at a heating rate less than 750&#xb0; C./hr or by heating to the homogenization treatment temperature and held the homogenization treatment temperature for 3 hours.

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Shimonoseki, Japan

Yukimasa Miyata