JP2007077415A - Method for producing aluminum alloy sheet for truncated cone bulging - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an aluminum alloy sheet having excellent ductility and satisfactory truncated cone bulging formability. <P>SOLUTION: An aluminum ingot containing 2.2 to <3.0% Mg, 0.2 to 1.0% Mn, 0.05 to 0.25% Fe and 0.02 to 0.2% Si, and the balance inevitable impurities is subjected to homogenizing treatment, and is thereafter subjected to hot rolling where the rolling ratio in the final pass is 30 to 60%, and rolling finishing temperature is 300 to 340°C, thus, in the cross-section in the sheet thickness-rolling direction, the crystal grain size in the sheet thickness direction is controlled to ≤50 microns, and elongation in the rolling direction is controlled to ≥20%. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

本発明は、例えばブレーキディスクハブ用などに用いられる延性に優れた円錐台張出成形用アルミニウム合金板の製造方法に関するものである。   The present invention relates to a method for manufacturing an aluminum alloy plate for frustoconical overhanging that is excellent in ductility, for example, used for a brake disc hub.

２輪車用ブレーキはブレーキパッドと摺動するディスク部にはスチールが、ディスクを支えるハブ部には軽量化のためアルミが多く使用されている。このディスクハブ材には強度・耐食性の点からＡｌ−Ｍｇ系合金が用いられており、さらなる高強度化のためにはＭｇ含有量の増加あるいは調質を加工材（Ｈ調質）とすることが挙げられるが、一般的にこれらは耐食性の低下や成形性が低下することが言われている。   In motorcycle brakes, steel is used for the disk part that slides with the brake pad, and aluminum is used for the hub part that supports the disk for weight reduction. This disk hub material is made of Al-Mg alloy from the viewpoint of strength and corrosion resistance. To increase the strength further, increase the Mg content or temper the material (H tempered). In general, it is said that these have lower corrosion resistance and lower formability.

特許文献1（特開２００１−２９４９６４号公報）ではさらに高強度化あるいはアルマイト後の色調を目的としてＭｎ，Ｚｒを含むＡｌ−Ｍｇ合金が提案されている。この方法ではＭｎ，Ｚｒによる再結晶抑制によりサブグレイン組織を維持し高強度化を計る方法や冷間圧延後に焼鈍を行いサブグレインを安定させる方法が提案されている。
特開２００１−２９４９６４号公報 Patent Document 1 (Japanese Patent Laid-Open No. 2001-294964) proposes an Al—Mg alloy containing Mn and Zr for the purpose of further increasing the strength or color tone after anodizing. In this method, a method of maintaining the subgrain structure by suppressing recrystallization by Mn and Zr to increase the strength, and a method of stabilizing the subgrain by annealing after cold rolling are proposed.
JP 2001-294964 A

しかしながら内部を加工組織として高強度を計った場合、ディスクハブ材に深い絞り成形を行う際に材料の延性不足により割れが発生し問題となることがある。このため冷間加工後に完全焼鈍を行いＯ材調質で使用されることが多い。   However, when high strength is measured using the inside as a processed structure, cracking may occur due to insufficient ductility of the material when deep drawing is performed on the disk hub material. For this reason, it is often used in the O material refining after complete annealing after cold working.

本発明ではＡｌ−Ｍｇ系合金の添加元素量および圧延条件について検討し、延性に優れ良好な円錐台張出成形性を有するアルミニウム合金板の製造方法を提供するものである。   In the present invention, the amount of additive elements and rolling conditions of an Al-Mg alloy are studied, and a method for producing an aluminum alloy sheet having excellent ductility and excellent truncated cone formability is provided.

本発明は、請求項1記載の通り、Ｍｇ：２．２〜３．０％未満，Ｍｎ：０．２〜１．０％，Ｆｅ：０．０５〜０．２５％，Ｓｉ：０．０２〜０．２％を含有し、残部不可避的不純物を含むアルミニウム合金鋳塊を、均質化処理を行った後、最終パスの圧延率を３０〜６０％で圧延終了温度を３００〜３４０℃とする熱間圧延を行うことによって、板厚−圧延方向断面において板厚方向の結晶粒径を５０ミクロン以下，圧延方向の伸びを２０％以上とすることを特徴とする円錐台張出成形用アルミニウム合金板の製造方法である。   According to the present invention, Mg: 2.2 to less than 3.0%, Mn: 0.2 to 1.0%, Fe: 0.05 to 0.25%, Si: 0.02 The aluminum alloy ingot containing ~ 0.2% and containing the remaining inevitable impurities is homogenized, and then the rolling rate of the final pass is 30 ~ 60% and the rolling finish temperature is 300 ~ 340 ° C. An aluminum alloy for frustoconical overhang forming characterized by performing hot rolling so that the crystal grain size in the plate thickness direction is 50 microns or less and the elongation in the rolling direction is 20% or more in the cross section in the plate thickness-rolling direction It is a manufacturing method of a board.

本発明によって得られるアルミニウム合金板は延性および円錐台張出成形性に優れており、ブレーキディスクハブ等の用途に好適に用いることができる。   The aluminum alloy plate obtained by the present invention is excellent in ductility and frusto-extrusion formability, and can be suitably used for applications such as a brake disc hub.

次に本発明の構成の限定理由を以下説明する。   Next, the reasons for limiting the configuration of the present invention will be described below.

まず、合金成分の限定理由を説明する。   First, the reasons for limiting the alloy components will be described.

ＭｇはＡｌ中に固溶し強度を向上させる働きがあり重要な元素である。Ｍｇ含有量が２．２％未満では強度向上効果が小さくブレーキディスク用ハブ材として十分な強度が得られない。また３．０％以上の場合、耐食性が低下し問題となる。従って、Ｍｇの添加量は２．２％以上３．０％未満とする。   Mg is an important element having the function of improving the strength by solid solution in Al. If the Mg content is less than 2.2%, the strength improvement effect is small and sufficient strength as a brake disk hub material cannot be obtained. On the other hand, if it is 3.0% or more, the corrosion resistance is lowered, which is a problem. Therefore, the addition amount of Mg is set to 2.2% or more and less than 3.0%.

ＭｎはＡｌ中に固溶すると同時にＡｌ−Ｍｎ系の微細な析出物を分散し、強度を向上させる働きと結晶粒を微細化する働きがある。その効果は０．２％未満では十分ではなく、１．０％を超えると飽和すると同時に粗大な金属間化合物を形成し、延性あるいは疲労特性を低下させる。従って、Ｍｎの添加量は０．２％以上１．０％以下とする。   Mn dissolves in Al and simultaneously disperses Al-Mn fine precipitates to improve strength and refine crystal grains. The effect is not sufficient if it is less than 0.2%, and if it exceeds 1.0%, it becomes saturated and a coarse intermetallic compound is formed, and ductility or fatigue properties are lowered. Therefore, the amount of Mn added is 0.2% to 1.0%.

ＦｅはＡｌに含まれる不純物の一つである。ただしＦｅ含有量が０．０５〜０．２５％ではＡｌ−Ｆｅ系化合物として分散し、結晶粒の微細化としての効果もある。ただし０．２５％を超えると粗大な金属間化合物を形成し、延性あるいは疲労特性を低下させる。従って、Ｆｅの添加量は０．０５％以上０．２５％以下とする。   Fe is one of impurities contained in Al. However, when the Fe content is 0.05 to 0.25%, it is dispersed as an Al—Fe-based compound, which also has an effect of making crystal grains finer. However, if it exceeds 0.25%, a coarse intermetallic compound is formed, and ductility or fatigue characteristics are lowered. Therefore, the addition amount of Fe is set to 0.05% or more and 0.25% or less.

ＳｉもＡｌ中に含まれる不純物の一つであり、０．２％を超えるとＭｇ_２ＳｉやＡｌ−Ｆｅ−Ｓｉ系化合物により延性あるいは疲労特性を低下させる。従って、Ｓｉの含有量は０．２％以下とする。 Si is also one of the impurities contained in Al, and when it exceeds 0.2%, ductility or fatigue characteristics are lowered by Mg ₂ Si or Al—Fe—Si based compounds. Therefore, the Si content is 0.2% or less.

その他不純物元素については特に規定するものではないが、通常工業的に用いられるＡｌ合金中にはＣｕ，Ｚｎ，Ｃｒ，Ｎｉなどが含まれるが０．２％以下の含有量であれば本発明の特性を損なわないかぎり含まれていても問題ない。またＴｉは通常結晶粒微細化のため０．１％以下程度添加される。   Other impurity elements are not particularly specified, but Al alloys usually used industrially contain Cu, Zn, Cr, Ni, etc., but if the content is 0.2% or less, There is no problem even if it is included as long as the characteristics are not impaired. Ti is usually added in an amount of about 0.1% or less for crystal grain refinement.

次に製造方法に関して述べる。   Next, a manufacturing method will be described.

上記成分組成の合金を通常の半連続鋳造で鋳塊を製造し、必要に応じて面削し、均質化処理して熱間圧延する。   An ingot is produced by an ordinary semi-continuous casting of the alloy having the above component composition, faced as necessary, homogenized, and hot-rolled.

本発明合金においては熱間圧延時の温度条件は最も重要である。本発明合金は熱間圧延中あるいは熱間圧延終了後にコイル状に巻取られた状態で再結晶することが見出された。この温度を制御することで熱間圧延後の板材で歪みの少ない完全焼鈍材に近い特性が得ることができる。その熱間圧延終了温度は３００℃未満では内部まで均一に再結晶を完了させるのに温度が不十分で、内部特に板厚中央部に加工組織が残存した場合は延性あるいは成形性を低下させる。また再結晶率を１００％とするために熱間圧延終了温度は高い方が望ましいが３４０℃を超えると１００％の再結晶率は得られるものの結晶粒の成長が生じ、粗大化するため成形後に肌荒れと呼ばれる表面に凹凸が発生するため問題となる。また本発明の温度範囲であれば、従来熱間圧延後あるいは冷間圧延後に実施していた焼鈍工程が省略でき、エネルギー面や環境保護の点からも大きなメリットが得られる。   In the alloy of the present invention, the temperature condition at the time of hot rolling is the most important. It has been found that the alloy of the present invention recrystallizes in a coiled state during hot rolling or after completion of hot rolling. By controlling this temperature, it is possible to obtain characteristics close to that of a completely annealed material with little distortion in a plate material after hot rolling. If the hot rolling finish temperature is less than 300 ° C., the temperature is insufficient to complete the recrystallization uniformly to the inside, and if the processed structure remains inside, particularly in the central portion of the plate thickness, ductility or formability is lowered. In order to set the recrystallization rate to 100%, it is desirable that the hot rolling finish temperature is higher. However, if the temperature exceeds 340 ° C., although a recrystallization rate of 100% can be obtained, crystal grains grow and become coarse after forming. This is a problem because irregularities occur on the surface called rough skin. Moreover, if it is the temperature range of this invention, the annealing process conventionally implemented after hot rolling or after cold rolling can be skipped, and the big merit is acquired also from the point of an energy surface or environmental protection.

熱間圧延時の圧延率も同様に完全再結晶組織を得るために重要な因子である。特に熱間圧延最終パスは再結晶を起こすための歪み駆動力を与えるため非常に重要となる。この熱間圧延最終パスの圧延率が３０％未満では再結晶するための歪みが不十分となり、回復組織となるかあるいは歪み誘起粒界移動により結晶粒の粗大化を起こす恐れがある。また圧延率が６０％を超えると変形抵抗が大きくなり工業的に製造することが困難となる。変形抵抗の低減には材料温度の高温化が挙げられるが結果的に熱間圧延終了後の温度が高くなりすぎるため、結晶粒の粗大化を引き起こす恐れがある。   The rolling ratio during hot rolling is also an important factor for obtaining a complete recrystallization structure. In particular, the final hot rolling pass is very important because it gives a strain driving force to cause recrystallization. If the rolling ratio of this final hot rolling pass is less than 30%, the strain for recrystallization is insufficient, and there is a risk of becoming a recovery structure or coarsening of crystal grains due to strain-induced grain boundary movement. On the other hand, when the rolling rate exceeds 60%, the deformation resistance increases and it is difficult to manufacture industrially. Reduction of the deformation resistance includes raising the material temperature, but as a result, the temperature after the hot rolling is too high, there is a risk of causing coarsening of crystal grains.

次に本発明方法によって得られる板材の特性の規定について述べる。   Next, the characteristics of the plate material obtained by the method of the present invention will be described.

ブレーキディスクハブ材のような円錐台張出し成形を行う場合の成形時の割れを防止することが必要である。成形性の改善としては素材の延性が重要であり、圧延方向の伸びが２０％以上であれば成形時に割れが発生せず、良好な成形性が得られる。   It is necessary to prevent cracking during molding when performing frustoconical overhanging molding such as a brake disc hub material. In order to improve the formability, the ductility of the material is important. If the elongation in the rolling direction is 20% or more, cracks do not occur during molding, and good formability is obtained.

結晶粒径は最終の板材での機械的特性を大きく決定するだけでなく、成形後の表面品質にも大きく影響する。本発明のように冷間圧延を行わず熱間圧延をもって最終板とする場合においては結晶粒径は等軸状ではなく圧延方向に伸長した形状となる。このため板厚−圧延方向断面の板厚方向で結晶粒径を規定する必要があり、その大きさが５０μｍを超えると成形後に肌荒れなどの表面不良を起こす。   The crystal grain size not only greatly determines the mechanical properties of the final plate, but also greatly affects the surface quality after molding. When the final plate is formed by hot rolling without cold rolling as in the present invention, the crystal grain size is not an equiaxed shape but a shape elongated in the rolling direction. For this reason, it is necessary to define the crystal grain size in the plate thickness direction of the cross section in the plate thickness-rolling direction. If the size exceeds 50 μm, surface defects such as roughening of the surface occur after molding.

なお本発明では熱間圧延により最終板を製造する方法であるが、フラット矯正のための矯正工程は組織的な変化を起こさないため必要に応じて実施しても問題ない。   In the present invention, the final plate is manufactured by hot rolling. However, the correction process for flat correction does not cause a systematic change, and there is no problem even if it is performed as necessary.

表１に示す通り１４種類の組成について実験室的に厚さ８０ｍｍｘ幅２００ｍｍｘ長さ２００ｍｍの鋳塊を作製し、均質化処理を行った。続いてそれぞれの条件で厚さ５ｍｍまで実験圧延機にて熱間圧延を行った。なお熱間圧延最終パス圧延率６０％以上についても実験を行ったが、変形抵抗の増大により圧延不可能であった。   As shown in Table 1, an ingot having a thickness of 80 mm, a width of 200 mm, and a length of 200 mm was experimentally prepared for 14 types of compositions, and homogenized. Subsequently, hot rolling was performed with an experimental rolling mill to a thickness of 5 mm under each condition. An experiment was also conducted for a hot rolling final pass rolling rate of 60% or more, but rolling was impossible due to an increase in deformation resistance.

得られた板材から圧延方向にＪＩＳ５号引張り試験片を作製し延性（伸び）を測定した。また、成形性の評価は圧延方向と直角方向に短冊状試験片を切り出し板厚断面をミーリング加工により厚さ５ｍｍｘ幅３０ｍｍｘ長さ１５０ｍｍの試験片を作製した。この試験片を曲げ部が圧延方向と平行になるように先端Ｒを変えて１８０°曲げ試験を行い、２ｔ（Ｒ＝１０ｍｍ）曲げが可能かどうかで評価をおこなった。結晶粒径は板厚−圧延方向断面を研磨後ケラー氏液でエッチングし板厚方向の結晶粒径を切断法により求めた。   A JIS No. 5 tensile test piece was produced in the rolling direction from the obtained plate material, and the ductility (elongation) was measured. In addition, for the evaluation of formability, a strip-shaped test piece was cut out in a direction perpendicular to the rolling direction, and a test piece having a thickness of 5 mm, a width of 30 mm, and a length of 150 mm was produced by milling the plate thickness section. The test piece was subjected to a 180 ° bending test while changing the tip R so that the bent portion was parallel to the rolling direction, and evaluated by whether 2t (R = 10 mm) bending was possible. The crystal grain size was obtained by polishing the cross section in the plate thickness-rolling direction and then etching with Keller solution to obtain the crystal grain size in the plate thickness direction by a cutting method.

表２に評価結果を示す。   Table 2 shows the evaluation results.

本発明例では圧延方向の伸びが２０％以上得られており、曲げ半径２ｔによる１８０°曲げでも割れは発生しなかった。さらに結晶粒径も５０μｍ以下で曲げ部の外観も良好であった。   In the examples of the present invention, an elongation in the rolling direction of 20% or more was obtained, and no cracks were generated even when bending at 180 ° with a bending radius of 2t. Furthermore, the crystal grain size was 50 μm or less, and the appearance of the bent part was good.

これに対して比較例ではＩ，Ｋのように曲げ成形で割れは認められなかったものの、結晶粒径の粗大化により肌荒れと呼ばれる外観不良が発生した。またＪ，Ｌ，Ｍ，Ｎでは圧延終了温度が低いため伸びが低い値となっており、曲げ性が著しく劣る結果となっている。
On the other hand, in the comparative example, cracks were not recognized by bending as in I and K, but an appearance defect called rough skin occurred due to the coarsening of the crystal grain size. Further, in J, L, M, and N, since the rolling end temperature is low, the elongation is low and the bendability is remarkably inferior.

Claims (1)

Ｍｇ：２．２〜３．０％未満（ｍａｓｓ％、以下同じ），Ｍｎ：０．２〜１．０％，Ｆｅ：０．０５〜０．２５％，Ｓｉ：０．０２〜０．２％を含有し、残部不可避的不純物を含むアルミニウム合金鋳塊を、均質化処理を行った後、最終パスの圧延率を３０〜６０％で圧延終了温度を３００〜３４０℃とする熱間圧延を行うことによって、板厚−圧延方向断面において板厚方向の結晶粒径を５０ミクロン以下，圧延方向の伸びを２０％以上とすることを特徴とする円錐台張出成形用アルミニウム合金板の製造方法。
Mg: 2.2 to less than 3.0% (mass%, the same applies hereinafter), Mn: 0.2 to 1.0%, Fe: 0.05 to 0.25%, Si: 0.02 to 0.2 The aluminum alloy ingot containing the remaining unavoidable impurities is subjected to homogenization treatment, and then subjected to hot rolling at a rolling rate of 30 to 60% in the final pass and a rolling end temperature of 300 to 340 ° C. A method for producing an aluminum alloy plate for frustoconical overhang forming, characterized in that the crystal grain size in the plate thickness direction is 50 microns or less and the elongation in the rolling direction is 20% or more in the cross section in the plate thickness-rolling direction. .