JP3550944B2 - Manufacturing method of high strength 6000 series aluminum alloy extruded material with excellent dimensional accuracy - Google Patents

Description

合金成分Ｍｎ，Ｃｒ，Ｚｒは、ビレットの均質化処理時に化合物として析出し、押出し時に組織が再結晶や再結晶粒が粗大化することを抑制し、組織強化により機械的強度を向上させる。このような作用は、０．２重量％以上のＭｎ，０．１重量％以上のＣｒ又は０．１重量％以上のＺｒを含むとき顕著になる。しかし、０．６０重量％を超えるＭｎ，０．４重量％を超えるＣｒ，０．２重量％を超えるＺｒ，又は合計量が０．８重量％を超える多量のＭｎ，Ｃｒ及び／又はＺｒが含まれると、押出し直後の押出し材の冷却時にＭｇ_２ Ｓｉが析出し易くなる。その結果、本発明で規定した冷却条件下でも、強度向上に寄与しないＭｇ_２ Ｓｉが析出し、強度向上に有効な時効処理時のＭｇ_２ Ｓｉ量が減少し、十分な機械的強度が得られない。
【００１１】
押出し機から出てきた直後の温度：５１０〜５７０℃
押出し材は、押出し直後の温度によって機械的性質が大きく変わる。押出し直後の温度が５１０℃を下回るようになると、Ｍｇ，Ｓｉ等の合金成分が十分に固溶せず、時効処理工程で析出するＭｇ_２ Ｓｉが減少し、必要とする機械的性質が得られなくなる。しかし、押出し直後の温度が５７０℃を超えるようになると、テアリングが発生し易くなり、生産性が低下する。
押出し直後の温度は、ビレット温度により制御できる。具体的には、押し出し直後の温度を５１０〜５７０℃の範囲に維持するためには、ビレットを４３０〜５１０℃の温度範囲に加熱保持する。４３０℃未満のビレット温度では、押出し圧力が上昇し、押出し製品速度が抑えられる。そのため、押出し直後の形材温度を５１０℃以上とすることができず、十分な機械的性質が得られない。また、低い押出し製品速度のため、生産性も阻害される。しかし、ビレット温度が５１０℃を超えるようになると、テアリング発生を防止するため押出し速度を上げることができず、生産性が低くなる。
【００１２】
また、押出しに供されるビレットを均質化処理しておくことも有効である。均質化処理によってＭｇ，Ｓｉ等の合金成分がマトリックスに析出し、時効処理工程で必要な強度を得るためのＭｇ_２ Ｓｉの析出が促進される。均質化処理としては、２００℃／時以下（好ましくは１００℃／時以下）の昇温速度で５００〜５６０℃（好ましくは５００〜５５０℃）に加熱し、この温度で１時間以上保持し、次いで２００℃／時以上の冷却速度で室温まで急冷する条件が採用される。この均質化処理により、Ｍｇ，Ｓｉ，Ｃｕ等の濃度偏析が解消される。本発明のようにＭｎ，Ｃｒ，Ｚｒを含む合金系にあっては、この均質化処理によってＭｎ，Ｃｒ，Ｚｒを微細均一に析出させ、押出し材の結晶粒を微細化させることができる。その結果、得られた製品の機械的性質が向上する。
【００１３】
４２０℃までの温度域における冷却速度：３０℃／分以上で１０００℃／分未満４５０℃から４２０℃までは、時効処理後の機械的性質を低下させることになるＭｇ_２ Ｓｉが析出する温度域である。しかし、Ｍｇ_２ Ｓｉの析出には、４５０〜４２０℃で比較的長い時間を必要とする。そのため、押出し直後から４２０℃までの温度域では、比較的緩やかな冷却速度で押出し材を冷却しても、機械的性質が劣化することはない。
緩やかに冷却することにより、押出し材が均一に冷却され、断面変形，曲り等の形状不良が発生しない。しかし、３０℃／分に達しない遅い冷却速度では、強度の改善に寄与しないＭｇ_２ Ｓｉが析出し、時効処理工程で必要とする機械的強度が得られない。また、３０℃／分に達しない冷却速度で冷却するためには、特別な装置が必要になり、生産コストが上昇する。他方、Ｍｎ，Ｃｒ，Ｚｒを含有する合金は、Ｍｎ，Ｃｒ，Ｚｒを含有していない合金に比較して強度が高いため変形しにくいものの、１０００℃／分以上の冷却速度で冷却すると、押出し材の冷却ムラが大きくなり、本発明で規定した組成をもつ合金でも変形が生じてしまう。なお、冷却水等を使用した冷却方法よりも、冷却ムラが比較的発生しにくい強制空冷で達成可能な冷却速度３００℃／分以下で冷却することが好ましい。
【００１４】
４２０〜２８０℃の温度域における冷却速度：１０００℃／分以上
４２０〜２８０℃は、時効処理後の機械的性質を低下させることになるＭｇ_２ Ｓｉが析出する温度域である。Ｍｇ_２ Ｓｉは、図１に示すように、この温度域では非常に短時間で析出する。そこで、４２０〜２８０℃の温度域では、Ｍｇ_２ Ｓｉが析出しないように冷却速度を１０００℃／分以上と高く設定する。冷却速度が１０００℃／分に達しないと、Ｍｇ_２ Ｓｉが析出し、時効処理工程で必要とする機械的強度が得られない。１０００℃／分以上の冷却速度は、水槽への浸漬等の適宜の方法で達成される。また、水槽の水温や水槽に焼入れ助剤等を投入することによっても、冷却速度を制御できる。なお、機械的強度をより向上させるためには、５０００℃／分以上の冷却速度で冷却することが好ましい。更に、４２０℃まで冷却してから冷却ムラが発生しても、押出し直後から冷却する場合に比較して冷却ムラの度合いも少ない。
【００１５】
２８０〜１５０℃の温度域における冷却速度：３０℃／分以上
２８０〜１５０℃は、Ｍｇ_２ Ｓｉが析出する温度域である。しかし、この温度域においてはＭｇ_２ Ｓｉの析出に比較的長時間がかかり、３０℃／分以上で冷却する限りＭｇ_２ Ｓｉの析出が抑制される。
１５０℃から室温までの温度域では、冷却速度が特に限定されるものではない。そのため、２８０〜１５０℃の温度域と同じ冷却条件で、押出し材を室温まで冷却することもできる。或いは、放置冷却によって押出し材を室温まで冷却しても良い。
【００１６】
時効処理：１６０〜２１０℃×１〜１５時間
室温まで冷却された押出し材は、次いで時効処理でＭｇ_２ Ｓｉを析出させることにより高強度化される。必要とする強度を得るためには、時効処理条件が１６０〜２１０℃×１〜１５時間に設定される。時効温度が１６０℃未満では、１５時間の時効処理では十分な強度が得られず、逆に２１０℃を超えるとピーク強度が低下し、十分な強度が得られない。また、１５時間を超える時効処理では、生産性が低下するばかりか、過時効となる虞れもある。逆に１時間に達しない時効処理では、安定した強度が得られない。
【００１７】
【実施例】
実施例１〜３：
表１に組成を示すアルミ合金を電気炉で溶製し、ＤＣ鋳造法で直径２０３ｍｍのビレットに鋳造した。ビレットを１００℃／時で昇温し、５４０℃×４時間保持→空冷（冷却速度２００℃／時）の均質化処理を施した。
均質化処理したビレットを、押出し直後の温度が５５０℃となるように４６０℃に加熱保持した後、図２に示した寸法の日型断面形状に押し出した。得られた押出し材を、表２に示す冷却条件下で室温まで冷却した。
【００１８】

【００１９】
比較例１：
均質化処理された試験番号１，２のアルミ合金を、押出し直後の温度が約５５０℃となるように４６０℃に加熱保持した後、実施例と同じサイズ及び形状に押し出し、７０℃の温水槽への浸漬により５５０℃から室温まで３０００℃／分の冷却速度で冷却した。
比較例２：
均質化処理された試験番号１，２のビレットを、押出し直後の温度が５５０℃となるように４２０℃に加熱保持した後、実施例と同じ形状及びサイズに押し出した。得られた押出し材を、５５０℃から室温まで５０℃／分の冷却速度で室温まで放置冷却した。
比較例３：
均質化処理された試験番号１，２のアルミ合金を、押出し直後の温度が比較的低温の約５００℃となるように４６０℃に加熱保持した後、実施例と同じサイズ及び形状に押し出し、５５０℃から４２０℃までの温度域を５０℃／分で冷却し、次いで沸騰水槽への浸漬により室温まで１５００℃／分の冷却速度で急冷した。
【００２０】

【００２１】
室温に冷却された実施例１〜３及び比較例１〜３の各押出し材に、１８０℃×６時間の時効処理を施した。時効処理された押出し材について、機械的強度（引張強さ，０．２％耐力，伸び）を測定し、変形量を調査した。変形量は、押出し材の長さ５ｍおきの測定点５点で図２に示す箇所の角度を測定し、角度の平均的な変化によって変形量を評価した。
表３の調査結果にみられるように、本発明に従った実施例１〜３では何れの押出し材も寸法精度が良好で、ＪＩＳ Ｈ４１００の角度の特殊級の規格±１度以内であった。また、７Ｎ０１合金Ｔ６材のＨ４１００規格値である引張強さ３３５Ｎ／ｍｍ^２ 以上，０．２％耐力２７５Ｎ／ｍｍ^２ 以上，伸び１０％以上を満足する優れた機械的性質を示していた。
【００２２】
これに対し、押出し後から室温までを５０００℃／分以上で急冷した比較例１では、角度形状の不良がひどく、製品として出荷できなかった。押出し後から室温まで５０℃／分で徐冷した比較例２では、必要とする機械的強度が得られなかった。押出し直後の温度が低い比較例３では、同じアルミ合金を使用したにも拘らず、時効処理後に低い強度が示された。これは、ビレットを均質化処理する際の冷却過程で析出したＭｇ_２ Ｓｉが押出し形材の温度が低いためにマトリックスに固溶せず、結果として時効処理時に析出するＭｇ_２ Ｓｉ量が不足したことが原因である。
【００２３】

【００２４】
【発明の効果】
以上に説明したように、本発明においては、成分・組成が特定されたアルミ合金を押出し成形する際、押出し直後の温度及び押出し後から室温までの冷却条件を制御することにより、急冷による断面変形や曲り等の形状不良が発生することを防止し、時効処理工程で析出硬化に有効なＭｇ_２ Ｓｉ量を確保している。そのため、時効処理後の強度が高く、寸法精度の良好な押出し材が得られる。
【図面の簡単な説明】
【図１】Ａｌ−Ｍｇ−Ｓｉ系合金のＴＴＰ曲線を示すグラフ
【図２】実施例で製造した押出し形材[0001]
[Industrial applications]
The present invention relates to a method for producing an extruded aluminum alloy material which is used as a structural material requiring the same strength as that of the 7000 series and requires excellent strength and dimensional accuracy.
[0002]
[Prior art]
Aluminum alloys such as the 6000 series are subjected to a solution treatment at a high temperature and then rapidly cooled, thereby precipitating Mg ₂ Si or the like in a subsequent aging treatment step to improve mechanical properties. The quenching after the solution treatment is a necessary step to obtain the precipitation hardening in the aging treatment step.
When quenching after solution treatment is applied during extrusion and the extruded material immediately after being sent out from the extruder is forcibly cooled, the temperature distribution becomes uneven with respect to the cross section of the extruded material due to the shape and thickness of the extruded material. Become. The non-uniform temperature distribution causes deformation such as collapse (change in shape) and bending in the longitudinal direction in the cross-sectional shape of the extruded material cooled to room temperature, causing deterioration in dimensional accuracy.
Defects such as cross-sectional deformation and bending are caused by cooling the extruded material immediately after extrusion at a temperature of 600 to 400 ° C. at a temperature of 30 to 60 ° C./sec. Japanese Patent Application Laid-Open No. 8-199319 discloses that rapid cooling can be prevented.
[0003]
[Problems to be solved by the invention]
However, the cooling rate such as 30 to 60 ° C./sec or 100 to 150 ° C./sec is lower than that of the cooling method using a fan (about 3 ° C./sec) or the cooling method using direct water cooling (about 1000 ° C./sec). It is difficult to control properly. In fact, cooling the profile under these conditions requires very sophisticated technology and special cooling equipment, which increases the heat treatment costs. Also, at this cooling rate, the cross-sectional shape of the extruded profile is likely to be changed.
The present invention has been devised to solve such a problem, and a combination of a specified composition of an aluminum alloy and a specified cooling condition enables a high strength to be developed by aging treatment, and furthermore, the dimensional accuracy is improved. It is intended to produce an aluminum alloy extruded material having a good quality.
[0004]
[Means for Solving the Problems]
In order to achieve the object, the method for manufacturing an extruded aluminum alloy material of the present invention has the following characteristics: Mg: 0.6 to 1.1% by weight, Si: 0.7 to 1.2% by weight, Cu: 0.05 to 0.1%. 8 wt%, Fe: 0.1-0.3 wt%, Ti: 0.005-0.05 wt%, B: 0.0001-0.01 wt%, and Mn: 0.2-0 60% by weight, Cr: 0.1 to 0.4% by weight, Zr: 0.1 to 0.2% by weight, containing 0.3 to 0.8% by weight in total; The billet of aluminum alloy with excess Si, calculated as% -0.58 × Mg%, in the range of 0.1-0.7% by weight, with the balance being substantially Al, emerges from the extruder. Extruded at a cooling rate of 30 ° C./min or more and less than 1000 ° C./min up to 420 ° C. Cooling the extruded material at a cooling rate of 1000 ° C / min or more in a temperature range of 420 to 280 ° C, and cooling the extruded material at a cooling rate of 30 ° C / min or more in a temperature range of 280 to 150 ° C. Features.
Prior to the extrusion, it is preferable to heat and maintain the billet of the aluminum alloy at 430 to 520 ° C. The obtained extruded material is subjected to aging treatment at 160 to 210C for 1 to 15 hours.
[0005]
[Action]
In the Al-Mg-Si alloy according to the present invention, Mg ₂ Si is precipitated in the aging treatment step to increase the strength, and at the time of extrusion by adding a transition element such as Mn, Cr, Zr, etc. By suppressing coarsening of crystals and recrystallized grains and leaving a fibrous structure formed by extrusion, a high strength equivalent to that of the 7000 series is obtained despite being a 6000 series. However, Mg ₂ Si also tends to precipitate from the matrix during the cooling process after extrusion. For example, the Al alloy according to the present invention contains a large amount of Mn, Cr, and Zr, and this tendency is particularly remarkable. When the Al alloy is maintained under the conditions on the right side of the TTP curve shown in FIG. 1, Mg ₂ Si precipitates. I do. If such precipitation of Mg ₂ Si occurs, the precipitation hardening effect due to the aging treatment is insufficient, and the strength is not sufficiently improved. Therefore, in the present invention, an extruded material having high strength and good dimensional accuracy can be obtained by specifying cooling conditions for suppressing precipitation of Mg ₂ Si in the cooling process after extrusion in relation to the composition of the aluminum alloy. I have.
[0006]
Hereinafter, the composition and temperature conditions specified in the present invention will be described.
Mg: 0.6 to 1.1% by weight
It precipitates as Mg ₂ Si at the time of aging treatment, and exhibits an effect of improving the strength of the extruded material. If the Mg content is less than 0.6% by weight, the amount of Mg ₂ Si precipitated during the aging treatment is insufficient, and sufficient mechanical strength cannot be obtained. Conversely, when a large amount of Mg exceeding 1.1% by weight is contained, Mg ₂ Si tends to precipitate when the extruded material is cooled immediately after extrusion. As a result, Mg ₂ Si that does not contribute to the strength improvement even under the cooling conditions specified in the present invention precipitates, and the amount of Mg ₂ Si deposited during aging treatment that contributes to the strength reduction is reduced, and sufficient mechanical strength is obtained. Absent.
[0007]
Si: 0.7 to 1.2% by weight
It precipitates as Mg ₂ Si at the time of aging treatment, and exhibits an effect of improving the strength of the extruded material. If the Si content is less than 0.7% by weight, the amount of Mg ₂ Si precipitated during the aging treatment is insufficient, and sufficient mechanical strength cannot be obtained. Conversely, if a large amount of Si exceeding 1.2% by weight is contained, Mg ₂ Si tends to precipitate when the extruded material is cooled immediately after extrusion. As a result, Mg ₂ Si that does not contribute to the strength improvement even under the cooling conditions specified in the present invention precipitates, and the amount of Mg ₂ Si deposited during aging treatment that contributes to the strength reduction is reduced, and sufficient mechanical strength is obtained. Absent.
Excess Si: 0.1 to 0.7% by weight
Excess Si calculated as Si% −0.58 × Mg% is important as an index when precipitating Mg ₂ Si effective for improving mechanical strength. If the excess Si is less than 0.1% by weight, the effective precipitation of Mg ₂ Si is insufficient, and sufficient mechanical strength cannot be obtained. Conversely, if the excess Si exceeds 0.7% by weight, the elongation of the extruded material decreases.
[0008]
Cu: 0.05-0.8% by weight
The mechanical strength increases as the Cu content increases to 0.05% by weight or more.
However, when a large amount of Cu exceeding 0.8% by weight is contained, Mg ₂ Si tends to precipitate when the extruded material is cooled immediately after extrusion. As a result, Mg ₂ Si that does not contribute to the strength improvement under the cooling conditions specified in the present invention precipitates, and the amount of Mg ₂ Si deposited during aging treatment that contributes to the strength reduction decreases.
Fe: 0.1 to 0.3% by weight
An effect of improving mechanical properties by forming an AlFeSi phase and refining the crystal grains of the extruded material is exhibited. Such an effect becomes remarkable at a Fe content of 0.1% by weight or more. However, when a large amount of Fe exceeding 0.3% by weight is contained, although the amount of the AlFeSi phase increases, the amount of Si decreases by that amount, and the amount of Mg ₂ Si precipitated in the aging process decreases. As a result, sufficient strength cannot be obtained.
[0009]
Ti: 0.005 to 0.05% by weight
It has the effect of refining the crystal grains of the ingot and suppressing casting cracks. Such an effect becomes remarkable at a Ti content of 0.005% by weight or more. However, when a large amount of Ti exceeding 0.05% by weight is contained, the extrudability deteriorates.
B: 0.001 to 0.01% by weight
When combined with Ti, it has the effect of further reducing the crystal grains of the ingot. The effect of adding B becomes significant at 0.001% by weight or more. However, when a large amount of B exceeding 0.01% by weight is contained, extrudability is impaired.
[0010]

The alloy components Mn, Cr, and Zr precipitate as compounds during the homogenization treatment of the billet, suppress recrystallization of the structure during extrusion and coarsening of recrystallized grains, and improve mechanical strength by strengthening the structure. Such an effect becomes remarkable when Mn of 0.2% by weight or more, Cr of 0.1% by weight or more, or Zr of 0.1% by weight or more is included. However, Mn exceeding 0.60% by weight, Cr exceeding 0.4% by weight, Zr exceeding 0.2% by weight, or a large amount of Mn, Cr and / or Zr exceeding 0.8% by weight as a total If it is included, Mg ₂ Si is likely to precipitate when the extruded material is cooled immediately after extrusion. As a result, even under the cooling conditions specified in the present invention, Mg ₂ Si not contributing to the strength improvement is precipitated, the amount of Mg ₂ Si during aging treatment effective for the strength improvement is reduced, and sufficient mechanical strength is obtained. Absent.
[0011]
Temperature immediately after coming out of the extruder: 510-570 ° C
The mechanical properties of an extruded material vary greatly depending on the temperature immediately after extrusion. When the temperature immediately after the extrusion becomes lower than 510 ° C., alloy components such as Mg and Si do not sufficiently form a solid solution, so that Mg ₂ Si precipitated in the aging treatment step is reduced, and required mechanical properties are obtained. Disappears. However, when the temperature immediately after extrusion exceeds 570 ° C., tearing is likely to occur, and the productivity is reduced.
The temperature immediately after extrusion can be controlled by the billet temperature. Specifically, in order to maintain the temperature immediately after the extrusion in the range of 510 to 570 ° C, the billet is heated and maintained in the temperature range of 430 to 510 ° C. At billet temperatures below 430 ° C., extrusion pressure increases and extrusion product speed is reduced. Therefore, the profile temperature immediately after extrusion cannot be set to 510 ° C. or higher, and sufficient mechanical properties cannot be obtained. Also, productivity is impaired due to the low extrusion product speed. However, when the billet temperature exceeds 510 ° C., the extrusion speed cannot be increased to prevent the occurrence of tearing, and the productivity is reduced.
[0012]
It is also effective to homogenize the billet to be extruded. By the homogenization treatment, alloy components such as Mg and Si precipitate in the matrix, and the precipitation of Mg ₂ Si for obtaining the necessary strength in the aging treatment step is promoted. As the homogenization treatment, heating to 500 to 560 ° C. (preferably 500 to 550 ° C.) at a heating rate of 200 ° C./hour or less (preferably 100 ° C./hour or less), and holding at this temperature for 1 hour or more, Then, a condition of rapidly cooling to room temperature at a cooling rate of 200 ° C./hour or more is adopted. By this homogenization treatment, concentration segregation of Mg, Si, Cu and the like is eliminated. In an alloy system containing Mn, Cr, and Zr as in the present invention, Mn, Cr, and Zr can be finely and uniformly precipitated by this homogenization treatment, and the crystal grains of the extruded material can be made fine. As a result, the mechanical properties of the obtained product are improved.
[0013]
Cooling rate in the temperature range up to 420 ° C .: 30 ° C./min or more and less than 1000 ° C./min. From 450 ° C. to 420 ° C., the temperature range in which Mg ₂ Si that deteriorates the mechanical properties after aging treatment is deposited. It is. However, the deposition of Mg ₂ Si requires a relatively long time at 450 to 420 ° C. Therefore, in the temperature range from immediately after extrusion to 420 ° C., even if the extruded material is cooled at a relatively slow cooling rate, the mechanical properties do not deteriorate.
By gradual cooling, the extruded material is uniformly cooled, and shape defects such as cross-sectional deformation and bending do not occur. However, at a slow cooling rate that does not reach 30 ° C./min, Mg ₂ Si that does not contribute to the improvement of the strength is precipitated, and the mechanical strength required in the aging process cannot be obtained. In addition, in order to cool at a cooling rate of less than 30 ° C./min, a special device is required, and the production cost increases. On the other hand, an alloy containing Mn, Cr, and Zr has a higher strength than an alloy containing no Mn, Cr, and Zr, and thus is less likely to be deformed. However, when cooled at a cooling rate of 1000 ° C./min or more, it is extruded. The cooling unevenness of the material increases, and deformation occurs even in the alloy having the composition specified in the present invention. It is preferable to perform cooling at a cooling rate of 300 ° C./min or less, which can be achieved by forced air cooling in which cooling unevenness is relatively unlikely to occur, as compared with a cooling method using cooling water or the like.
[0014]
Cooling rate in a temperature range of 420 to 280 ° C .: 1000 ° C./min or more 420 to 280 ° C. is a temperature range in which Mg ₂ Si that deteriorates mechanical properties after aging treatment is deposited. Mg ₂ Si is precipitated in a very short time in this temperature range as shown in FIG. Therefore, in the temperature range of 420 to 280 ° C., the cooling rate is set as high as 1000 ° C./min or more so that Mg ₂ Si does not precipitate. If the cooling rate does not reach 1000 ° C./min, Mg ₂ Si will precipitate, and the mechanical strength required in the aging step cannot be obtained. The cooling rate of 1000 ° C./min or more can be achieved by an appropriate method such as immersion in a water tank. The cooling rate can also be controlled by adding the quenching aid or the like to the water temperature of the water tank or the water tank. In order to further improve the mechanical strength, it is preferable to cool at a cooling rate of 5000 ° C./min or more. Furthermore, even if cooling unevenness occurs after cooling to 420 ° C., the degree of cooling unevenness is less than when cooling is performed immediately after extrusion.
[0015]
Cooling rate in a temperature range of 280 to 150 ° C: 30 ° C / min or more and 280 to 150 ° C is a temperature range in which Mg ₂ Si is deposited. However, in this temperature range, the precipitation of Mg ₂ Si takes a relatively long time, and the precipitation of Mg ₂ Si is suppressed as long as cooling is performed at 30 ° C./min or more.
In the temperature range from 150 ° C. to room temperature, the cooling rate is not particularly limited. Therefore, the extruded material can be cooled to room temperature under the same cooling conditions as in the temperature range of 280 to 150 ° C. Alternatively, the extruded material may be cooled to room temperature by standing cooling.
[0016]
Aging treatment: The extruded material cooled to room temperature at 160 to 210 ° C. for 1 to 15 hours is then strengthened by precipitating Mg ₂ Si by aging treatment. In order to obtain the required strength, the aging condition is set to 160 to 210 ° C. × 1 to 15 hours. If the aging temperature is lower than 160 ° C., sufficient strength cannot be obtained by aging treatment for 15 hours. Conversely, if the aging temperature exceeds 210 ° C., the peak strength decreases and sufficient strength cannot be obtained. Further, in the aging treatment for more than 15 hours, not only the productivity is lowered but also there is a possibility that the overaging may occur. Conversely, if the aging treatment does not reach 1 hour, stable strength cannot be obtained.
[0017]
【Example】
Examples 1-3:
An aluminum alloy having the composition shown in Table 1 was melted in an electric furnace and cast into a billet having a diameter of 203 mm by a DC casting method. The billet was heated at a rate of 100 ° C./hour, kept at 540 ° C. × 4 hours, and subjected to a homogenization treatment of air cooling (cooling rate 200 ° C./hour).
The billet subjected to the homogenization treatment was heated and maintained at 460 ° C. so that the temperature immediately after the extrusion became 550 ° C., and then extruded into a Japanese sectional shape having the dimensions shown in FIG. The obtained extruded material was cooled to room temperature under the cooling conditions shown in Table 2.
[0018]

[0019]
Comparative Example 1:
The homogenized aluminum alloys of Test Nos. 1 and 2 were heated and maintained at 460 ° C. so that the temperature immediately after extrusion was about 550 ° C., and then extruded to the same size and shape as in the example, and a 70 ° C. hot water tank was used. 550 ° C. to room temperature at a cooling rate of 3000 ° C./min.
Comparative Example 2:
The billets of Test Nos. 1 and 2 that had been homogenized were heated and maintained at 420 ° C. so that the temperature immediately after extrusion became 550 ° C., and then extruded into the same shape and size as in the examples. The obtained extruded material was allowed to cool to room temperature from 550 ° C. to room temperature at a cooling rate of 50 ° C./min.
Comparative Example 3:
The homogenized aluminum alloys of Test Nos. 1 and 2 were heated and maintained at 460 ° C. so that the temperature immediately after the extrusion was relatively low, about 500 ° C., and then extruded to the same size and shape as in the example. The temperature range from 50 ° C. to 420 ° C. was cooled at 50 ° C./min, and then rapidly cooled to room temperature at a cooling rate of 1500 ° C./min by immersion in a boiling water bath.
[0020]

[0021]
Each extruded material of Examples 1 to 3 and Comparative Examples 1 to 3 cooled to room temperature was subjected to an aging treatment at 180 ° C for 6 hours. The mechanical strength (tensile strength, 0.2% proof stress, elongation) of the aged extruded material was measured, and the amount of deformation was investigated. As for the amount of deformation, the angle of the location shown in FIG. 2 was measured at five measurement points every 5 m of the extruded material, and the amount of deformation was evaluated based on the average change in the angle.
As can be seen from the investigation results in Table 3, in Examples 1 to 3 according to the present invention, all extruded materials had good dimensional accuracy, and were within ± 1 degree of the JIS H4100 special angle standard. The tensile strength is H4100 standard value of 7N01 alloy T6 material 335n / mm ² or more, a 0.2% proof stress 275 N / mm ² or more, showed excellent mechanical properties that satisfy more than 10% elongation.
[0022]
On the other hand, in Comparative Example 1, in which the temperature was rapidly cooled from the extrusion to room temperature at 5000 ° C./min or more, the angular shape was bad and the product could not be shipped as a product. In Comparative Example 2, which was gradually cooled from the extrusion to room temperature at 50 ° C./min, the required mechanical strength was not obtained. In Comparative Example 3 in which the temperature immediately after extrusion was low, low strength was exhibited after the aging treatment, despite the use of the same aluminum alloy. This is because Mg ₂ Si precipitated in the cooling process when the billet was homogenized did not form a solid solution in the matrix due to the low temperature of the extruded profile, and as a result, the amount of Mg ₂ Si precipitated during the aging treatment was insufficient. That is the cause.
[0023]

[0024]
【The invention's effect】
As described above, in the present invention, when extruding an aluminum alloy having a specified composition and composition, by controlling the temperature immediately after the extrusion and the cooling conditions from the extrusion to the room temperature, the cross-sectional deformation due to rapid cooling is performed. The occurrence of shape defects such as bending and bending is prevented, and the amount of Mg ₂ Si effective for precipitation hardening in the aging treatment step is secured. Therefore, an extruded material having high strength after aging treatment and good dimensional accuracy can be obtained.
[Brief description of the drawings]
FIG. 1 is a graph showing a TTP curve of an Al—Mg—Si based alloy. FIG. 2 is an extruded member manufactured in Example.

Claims (3)

Mg: 0.6 to 1.1% by weight, Si: 0.7 to 1.2% by weight, Cu: 0.05 to 0.8% by weight, Fe: 0.1 to 0.3% by weight, Ti: 0.005 to 0.05% by weight, B: 0.001 to 0.01% by weight, Mn: 0.2 to 0.60% by weight, Cr: 0.1 to 0.4% by weight, Zr : Containing 0.1 to 0.2% by weight of one or more kinds in total of 0.3 to 0.8% by weight, and excess Si calculated as Si% −0.58 × Mg% is 0.1% A billet of an aluminum alloy having a composition of substantially 0.7% by weight, with the balance being substantially Al, is extruded so that the temperature immediately after coming out of the extruder is 510 to 570 ° C., and up to 420 ° C. Cools the extruded material at a cooling rate of 30 ° C./min or more and less than 1000 ° C./min, and a cooling rate of 1000 ° C./min or more in a temperature range of 420 to 280 ° C. In the extruded material is cooled, the production method of the aluminum alloy extruded material for cooling the extruded material at a cooling rate of more than 30 ° C. / minute in a temperature range of two hundred and eighty to one hundred fifty ° C.. The method for producing an aluminum alloy extruded material according to claim 1, wherein the aluminum alloy billet is extruded while being heated and maintained at 430 to 520 ° C. A method for producing an aluminum alloy extruded material, wherein the extruded material according to claim 1 or 2 is subjected to aging treatment at 160 to 210 ° C for 1 to 15 hours.

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