Kobe Steel, Ltd.

Kabushiki Kaisha Kobe Seiko Sho

Takahiro Shikama

Shinji Yoshihara

Narikazu Hashimoto

Tsunetake Tsuyoshi

Masatoshi Yoshida

Yukimasa Miyata

Yuki Tanaka

Takahiro Ozawa

Hiroyuki Kajiwara

Ryo Unoki

Misuzu Yamamoto

A door beam of a motor vehicle includes a 7000 series aluminum alloy extruded material, the 7000 series aluminum alloy extruded material including Zn: 7.5 mass % to 9.0 mass %, Mg: 1.3 mass % to 2.0 mass %, Cu: 0.1 mass % to 0.7 mass %, Si: 0.15 mass % or less, Fe: 0.3 mass % or less, Ti: 0.005 mass % to 0.2 mass %, and at least one of Mn, Cr, and Zr: 0.1 mass % to 0.5 mass %, in which contents of Mn, Cr and Zr satisfy Mn: 0.3 mass % or less, Cr: 0.25 mass % or less, and Zr: 0.25 mass %, respectively, with the remainder being Al and impurities. A Fe-based crystallized product is contained, and an average Cu content of the Fe-based crystallized product is 5.0 mass % or less.

Automotive door beam made of aluminum alloy extruded material

A door beam including an aluminum alloy extruded material of a closed section structure having a welded part along the longitudinal direction, webs and an outer flange are inhibited from buckling and further the welded part in the outer flange is inhibited from breaking at the time of collision. In a cross section of an aluminum alloy extruded material perpendicular to the extrusion direction, each of the webs includes an outer part connected to the outer flange and an inner part connected to an inner flange and the thickness of the outer part is larger than the thickness of the inner part. Each of the outer parts is positioned in a region outside a cross section center of the aluminum alloy extruded material in the vehicle body width direction.

Aluminum alloy door beam

A door beam includes an aluminum alloy extrusion body extended in a longitudinal direction and having a pair of webs and a pair of flanges to be positioned on an inner side and an outer side in a width direction of a vehicle body. The pair of webs connect the pair of flanges at joint portions of each of the pair of webs such that the pair of webs and the pair of flanges form a closed cross section in a direction perpendicular to the longitudinal direction, and the pair of webs do not have a welded portion.

Door beam

The stress corrosion cracking resistance of an aluminum alloy member consisting of 7000-series aluminum alloy extruded shape is improved. At least one region of a quenched aluminum alloy extruded shape is subjected to a restoring treatment of heating at a temperature-raising rate of 0.4&#xb0; C./second or more, holding at a temperature ranging 300 to 590&#xb0; C. for a time longer than zero second and cooling at a cooling rate of 0.5&#xb0; C./second or more. A plastic working is applied to the region within 72 hours. The region is subjected to a heat treatment of heating at a temperature-raising rate of 0.4&#xb0; C./second or more, holding at a temperature ranging 300 to 590&#xb0; C. for a time longer than zero second and not longer than 300 seconds and cooling at a cooling rate of 2000&#xb0; C./minute or less. The whole of the aluminum alloy extruded shape is subjected to an artificial aging treatment.

Method for producing 7000-series aluminum alloy member excellent in stress corrosion cracking resistance

An aluminum alloy member resistant to cracking and having high strengths and excellent stress corrosion cracking resistance is manufactured by crushing a 7xxx aluminum alloy extrudate. Specifically, a 7xxx aluminum alloy extrudate containing Zn of 3.0-8.0%, Mg of 0.4-2.5%, Cu of 0.05-2.0%, and Ti of 0.005-0.2%, in mass percent, and prepared through press quenching is subjected to a reversion treatment, to crushing within 72 hours after the reversion treatment, and then to aging. The reversion treatment includes heating at a temperature rise rate of 0.4&#xb0; C./second or more, holding in a temperature range of 200-550&#xb0; C. for longer than 0 second, and cooling at a rate of 0.5&#xb0; C./second or more. The ratio of the tensile residual stress &#x3c3;to the 0.2% yield stress &#x3c3;after aging and the total content X of Mg and Zn satisfy a condition specified by Expression (1):&#x2264;&#x2212;0.1+1.4&#x2003;&#x2003;(1).

7xxx series aluminum alloy member excellent in stress corrosion cracking resistance and method for manufacturing the same

An aluminum alloy member resistant to cracking and having high strengths and excellent stress corrosion cracking resistance is manufactured by crushing a 7xxx aluminum alloy extrudate. Specifically, a 7xxx aluminum alloy extrudate containing Zn of 3.0-8.0%, Mg of 0.4-2.5%, Cu of 0.05-2.0%, and Ti of 0.005-0.2%, in mass percent, and prepared through press quenching is subjected to a reversion treatment, to crushing within 72 hours after the reversion treatment, and then to aging. The reversion treatment includes heating at a temperature use rate of 0.4&#xb0; C./second or more, holding in a temperature range of 200-550&#xb0; C. for longer than 0 second, and cooling at a rate of 0.5&#xb0; C./second or more. The ratio of the tensile residual stress &#x3c3;to the 0.2% yield stress &#x3c3;after aging and the total content X of Mg and Zn satisfy a condition specified by Expression (1):&#x2264;&#x2212;0.1+1.4&#x2003;&#x2003;(1).

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

An aluminum alloy member resistant to cracking and having high strengths and excellent stress corrosion cracking resistance is manufactured by expanding a 7xxx aluminum alloy hollow extrusion at a rate of 5% or more. Specifically, a 7xxx aluminum alloy hollow extrusion containing Zn of 3.0-9.5%, Mg of 0.4-2.5%, Cu of 0.05-2.0%, and Ti of 0.005-0.2%, in mass percent, and prepared through press quenching is subjected to a reversion treatment, to pipe expansion within 72 hours after the reversion treatment, and to temper aging. The reversion treatment includes heating at a temperature rise rate of 0.4&#xb0; C./second or more, holding in a temperature range of 200-550&#xb0; C. for longer than 0 second, and cooling at a rate of 0.5&#xb0; C./second or more. The ratio Y (&#x3c3;/&#x3c3;) of the tensile residual stress &#x3c3;to the 0.2% yield stress &#x3c3;after temper aging and the total content X of Mg and Zn satisfy Expression (1):Y&#x2266;&#x2212;0.1X+1.4 &#x2003;&#x2003;(1).

There is provided a bumper beam that is formed of a 7000 series aluminum alloy hollow extrusion, has a crushed longitudinal portion, and locally has a low-hardness region in a bumper stay joint section. A portion (portion to be heated) of end portions of the bumper beam formed of a tempered member of a heat-treatable aluminum alloy extrusion is subjected to reversion treatment, thereby forming a heat-affected zone in a bumper stay joint section. An end region (portion to be crushed) of the heated portion is subjected to cold crushing, and then the whole bumper beam is subjected to age hardening. The heated portion and a non-heat-affected zone are hardened through the age hardening, thereby forming a low-hardness region that overlaps the joint section in a portion of the heat-affected zone.

Bumper structure and method for manufacturing bumper beam

A 7000-series aluminum alloy hollow extruded material formed by porthole extrusion contains Zn: 3.0 to 8.0 mass %, Mg: 0.4 to 2.0 mass %, Cu: 0.05 to 2.0 mass %, Si: 0.3 mass % or less, Fe: 0.35 mass % or less, and one or more of Mn, Cr, and Zr: 0.10 mass % or less in total, with the balance being Al and unavoidable impurities. The aluminum alloy hollow extruded material has a recrystallized structure throughout the cross-section. In the case of pipe expansion by electro-magnetic forming, excellent pipe expansion formability is obtained.

Growing community of inventors

Shimonoseki, Japan

Takahiro Shikama