JP4067432B2 - Method for producing Al-Mg aluminum alloy plate for hot blow molding and method for producing hot blow molded product - Google Patents

Description

【００３７】
まず表１中に示す合金成分のスラブを半連続鋳造により製作した。これらの合金を５００℃に８時間保持する均質化処理を行い，面削後３９５℃に加熱して熱間圧延を施して３．９ｍｍの熱間圧延板を得た。
次に，この熱間圧延板に対し，冷間圧延（冷間圧延率５０％）→中間焼鈍（昇温速度１０℃／ｓｅｃ，保持温度５００℃，保持時間３０秒）→冷間圧延（冷間圧延率３３％）→最終焼鈍（昇温速度１０℃／ｓｅｃ，保持温度５００℃，保持時間３０秒）を順次施して，１．３ｍｍ厚みのアルミニウム合金板を得た。
【００３８】
次に，得られたアルミニウム合金板を３５０ｍｍ角の四角形状に切り出して試験片とし，実際に熱間ブロー成形を行った。具体的には，上記試験片を４９０℃に加熱して，２５０ｍｍＷ×２５０ｍｍＬ×６５ｍｍＨの角筒形状に雌型により熱間ブロー成形した。底面中心部分の肉厚は０．８５ｍｍであり，肉厚減少率は約３４．６％であった。
【００３９】
次に，得られた角筒成形品の中心部分について引張試験による機械的性質を測定した。また同じく中心部から１００ｍｍ角のテストピースを切り取り，酸洗後，一般自動車用塗装を実施し，塗膜の品質（鮮鋭性）をテンションメータで評価した。
【００４０】
ここで，上記テンションメータの評価は，図１に示すごとく，撮影装置５を用いて行う。
撮影装置５は，テストピース１を覆うＴＰ収納部５１と，その側壁部に配設されたストロボ部５２及びカメラ部５３とよりなる。
【００４１】
ストロボ部５２は，筒状の入側導光部５２１を有し，その一端には光源となるストロボ５２２を配設し，他端にはストロボ５２２から発せられる光を後述する複数の線状光線に遮るスリット板５２３を配設してなる。
また，上記カメラ部５２は，筒状の出側導光部５３１を介してフィルムをセットするカメラ５３２を有している。
【００４２】
そして，撮影装置５は，出側導光部５３１に設けられたシャッター５５を操作することにより，上記ストロボ５２２から光を発射させ，その光をスリット板５２３を通してテストピース１の表面に当て，これを反射させてカメラ５３２によってフィルムに撮影するよう構成されている。
【００４３】
上記スリット板５２３は，図２に示すごとく，９〜２０までの１２段階の点数の領域に区画されている。各領域には，それぞれ複数の平行光線（スリット光）が得られるようにスリットが設けられており，スリットの間隔は，点数が高い領域のものほど狭くなるように設定されている。本例では，スリットＳの幅寸法（太さ）は一律０．２０ｍｍとした。また，スリットＳの間隔（ピッチ）は，表２に示すごとく設定した。
【００４４】
【表２】

【００４５】
そして，テンションメータの評価は，上記テストピース１の載置位置に評価しようとするサンプルを載置して上記撮影装置５により撮影した写真を用いて行った。具体的には，写真に表れている複数のスリット光を各領域ごとに目視により観察し，隣り合うスリット光に重なりが見られるか否かを判断する。そして，スリット光に重なりが見られていない領域のうち最大の点数を評価値とした。
この評価方法は，自動車メーカ等において一般に用いられる評価方法である。
【００４６】
これらの評価結果を表３に示す。表３における○は合格，×は不合格を示す。塗装後の品質についてはテンションメータ評価値が１５以上となるものを合格とした。また，自動車用車体パネル材としては，耐デント性が必要とされるため，耐力１１０ＭＰａ以上を有するものを合格とした。また，ヘム加工などの後加工における加工性が必要なため，１５％以上の伸びがあるものを合格とした。塗装後の鮮映性（テンションメータ評価値）については評価値が１５以上となるものを合格とした。
【００４７】
【表３】

【００４８】
表３より知られるごとく，本発明品である試料Ｅ１１〜Ｅ１６においては，耐力，伸び，テンションメータのいずれの評価も合格であった。
これに対し，比較例Ｃ１１は，Ｍｇの添加量が少ないため耐力が低く，またブロー成形中の結晶粒径が大きくなったため外観の肌あれが生じてテンションメータの評価が不合格であった。
比較例Ｃ１２は，Ｍｇ添加量が高すぎたため，熱間加工中に板が割れたため評価不能であった。
比較例Ｃ１３は，ＭｎおよびＣｒが添加されておらず，ブロー成形中の結晶粒径が大きくなったため外観の肌あれが生じてテンションメータの評価が不合格であった。
比較例Ｃ１４は，Ｆｅ，Ｓｉが多いため，ブロー成形中にキャビテーションが生じたため伸びが不合格となった。
【００４９】
（実施例２）
本例では，Ａｌ−４．８％Ｍｇ−０．７％Ｍｎ−０．１５％Ｃｒ−０．０２％Ｓｉ−０．０２％Ｆｅ−０．０１％Ｃｕ−５０ｐｐｍＢｅの組成でスラブを半連続鋳造により製作した。このスラブを５００℃の温度に８時間保持する均質化処理を施し，面削後３９５℃に加熱して熱間圧延板を作成し，引き続いて，表４中の工程に従ってそれぞれ１．３ｍｍの板を作製した。表４中における工程Ｅ２１，Ｅ２２，Ｅ２３は本発明の方法であり，工程Ｃ２１〜Ｃ３０は比較のために本発明と異なる工程を採用したものである。また，これらのうち，工程Ｅ２３及びＣ２９，Ｃ３０は，バッチ炉による冷間圧延前中間焼鈍を熱間圧延後に実施したものである。
【００５０】
【表４】

【００５１】
次に，得られた１．３ｍｍ厚みのアルミニウム合金板を３５０ｍｍ角の四角形状に切り出して試験片とし，実際に熱間ブロー成形を行った。具体的には，実施例１と同様に，上記試験片を４９０℃に加熱して，２５０ｍｍＷ×２５０ｍｍＬ×６５ｍｍＨの角筒形状に雌型により熱間ブロー成形した。底面中心部分の肉厚は０．８５ｍｍであり，肉厚減少率は約３４．６％であった。
【００５２】
次に，実施例１と同様に，得られた角筒成形品の中心部分について引張試験による機械的性質を測定した。また同じく中心部から１００ｍｍ角のテストピースを切り取り，酸洗後，一般自動車用塗装を実施し，塗膜の品質（鮮鋭性）をテンションメータで評価した。テンションメータでの評価方法は実施例１と同様である。
また，本例では，テンションメータによる評価に加え，ブロー成形品の表面評価を外観観察により行った。具体的には，冷間圧延前中間焼鈍後の板表面の酸化Ｍｇに起因するまだら模様がその後の圧延で延ばされた筋状の汚れが有るか否かを目視により観察し，汚れが観察された場合を×，汚れがなく美麗な表面の場合を○とした。そして，このブロー成形品の表面評価と上記のテンションメータ評価とを総合して，総合判定を行った。評価結果を表５に示す。表５における○は合格，×は不合格を示す。
【００５３】
【表５】

【００５４】
表５より知られるごとく，工程Ｅ２１，Ｅ２２により得られたアルミニウム合金板を熱間ブロー成形して得られた成形品については，満足できる外観が得られた。
一方，工程Ｃ２１は中間焼鈍を省略したため，熱間圧延板の不均一組織を改良することができず，評価が劣った。
工程Ｃ２２は中間焼鈍前の冷間圧延率が低かったため，中間焼鈍で再結晶せずに熱間圧延板の不均一組織を改良することができず，評価が劣った。
工程Ｃ２３は最終焼鈍前の圧延率が高すぎたため，強いせん断組織を作る結果となり，最終焼鈍後の組織が代えって不均一になり，評価が劣った。
【００５５】
工程Ｃ２４，Ｃ２５は中間もしくは最終焼鈍温度が低すぎたため再結晶せず，熱間圧延板の不均一組織を改良することができず，評価が劣った。
工程Ｃ２６，Ｃ２７は中間もしくは最終焼鈍の昇温速度が低すぎたため再結晶が不均一に発生して，熱間圧延板の不均一組織を改良することができず，評価が劣った。
工程Ｃ２８は最終焼鈍前の冷間圧延率が低かったため最終焼鈍で再結晶せず，圧延板の不均一組織を改良することができず，評価が劣った。
【００５６】
また，工程Ｅ２３は，上記のごとく冷間圧延前中間焼鈍を実施したものであり，その後の冷間圧延（冷延１）において負荷が小さく容易に圧延を行うことができた。そして，得られたブロー成形品の表面は美麗であり，表面品質にも優れていた。
【００５７】
一方，工程Ｃ２９，Ｃ３０は，冷間圧延前中間焼鈍を実施したものの，その加熱温度及び保持時間が本発明（請求項２）の範囲を超えるものである。いずれも，冷間圧延前中間焼鈍の後の冷間圧延（冷延１）の負荷は小さく容易に圧延を行うことができたが，冷間圧延前中間焼鈍を行った後の板表面に，酸化Ｍｇによるまだら模様が発生しており，表面品質が劣っていた。
【００５８】
（実施例３）
本例では，Ａｌ−４．８％Ｍｇ−０．７％Ｍｎ−０．１５％Ｃｒ−０．０２％Ｓｉ−０．０２％Ｆｅ−０．０１％Ｃｕ−５０ｐｐｍＢｅの組成でスラブを半連続鋳造により製作した。このスラブを５００℃の温度に８時間保持する均質化処理を施し，面削後３９５℃に加熱して熱間圧延した。次に，得られた熱間圧延板に対し，冷間圧延（冷間圧延率５０％）→中間焼鈍（昇温速度１０℃／ｓｅｃ，保持温度５００℃，保持時間３０秒）→冷間圧延（冷間圧延率３３％）→最終焼鈍（昇温速度１０℃／ｓｅｃ，保持温度５００℃，保持時間３０秒）を順次施して，中間材としてのアルミニウム合金板を得た。
【００５９】
そして，本例では，表６に示すごとく，上記中間材としてのアルミニウム合金板に対して，さらに冷間圧延と仕上げ熱処理を施し，その効果を評価した。なお，いずれの工程を選択しても最終板厚が１．３ｍｍとなるように，上記熱間圧延板の厚みを調整した。
上記最終焼鈍後の冷間圧延としては，冷間圧延率を３３％とした工程Ｅ３１の他に，冷間圧延率を５％および６５％に変更した比較工程Ｃ３１，Ｃ３２も行った。なお，いずれの工程においても，仕上げ熱処理は，昇温速度１０℃／ｓｅｃ，保持温度３５０℃，保持時間５秒の条件で行った。
【００６０】
【表６】

【００６１】
次に，得られたアルミニウム合金板を３５０ｍｍ角の四角形状に切り出して試験片とした。そして本例では，まずこの試験片に，Ｒ３の曲げを実施した後曲げ戻す冷間加工を施した。その後，実施例１と同様に，上記試験片を４９０℃に加熱して，２５０ｍｍＷ×２５０ｍｍＬ×６５ｍｍＨの角筒形状に雌型により熱間ブロー成形した。
次に，得られた角筒成形品の中心部分から１００ｍｍ角のテストピースを切り取り，酸洗後，一般自動車用塗装を実施し，塗膜の品質（鮮鋭性）をテンションメータで評価した。
評価方法は実施例１と同様である。評価結果を表７に示す。
【００６２】
【表７】

【００６３】
工程Ｅ３１のものは，良好な外観を呈した。
工程Ｃ３１については，曲げ−曲げ戻しした折り目に沿って，畝状の欠陥が生じた。また，冷間加工度が少なかったため，曲げ加工を受けた部分で熱間ブロー成形温度への加熱中に不均一な再結晶（粗粒化）が発生したので評価不能と判定した。
工程Ｃ３２は熱処理前の圧延率が高すぎたため，強いせん断組織を作る結果となり，熱間ブロー成形温度への加熱中にせん断に沿った不均一な再結晶が生じたため，評価が劣っている。
【００６４】
本例の結果から，熱間ブロー成形前に冷間加工を施す用途に使用されるアルミニウム合金板としては，上記最終焼鈍後に，少なくとも，さらに２５％以上５０％未満の冷間圧延率で冷間圧延を行い，その後，昇温速度１℃／ｓｅｃ以上で２７０℃〜４００℃の温度範囲内に加熱して５分以内の保持を行う仕上熱処理を施すことが有効であることがわかる。
【図面の簡単な説明】
【図１】実施例１における，テンションメータ測定用の撮影装置を示す説明図。
【図２】実施例１における，スリット板のスリット配置を示す説明図。
【符号の説明】
１．．．テストピース，
５．．．撮影装置，
５０．．．基台５０，
５１．．．ＴＰ収納部，
５２．．．ストロボ部，
５３．．．カメラ部５３，[0001]
【Technical field】
TECHNICAL FIELD The present invention relates to an Al—Mg-based aluminum alloy plate subjected to hot blow molding, and particularly to a plate material suitable for a portion requiring appearance such as an automobile body panel, and a hot blow molded product using the plate material. .
[0002]
[Prior art]
Hot blow molding is suitable as a technique suitable for high-mix low-volume production because the mold and manufacturing equipment are cheaper than cold press molding and the degree of freedom in molding is large.
The hot blow molding material is required to have fine recrystallized grains of around 10 μm in terms of metal structure. The feature of the manufacturing method is that, in order to obtain fine grains, the final rapid heating annealing is performed after the strong cold working. The amount of strain in cold working correlates with the crystal grain size formed in the final annealing process, and the crystal grain size becomes smaller as hard working is added. In actual production, strong processing induces cracks during rolling, so intermediate annealing is necessary. However, even when intermediate annealing is performed, it is necessary to increase the cold rolling rate before final annealing. is there.
[0003]
On the other hand, for example, in an automobile body panel, the appearance after painting is required to be smooth as an element of appearance quality.
When cold pressing is performed using a plate material for cold pressing, it is known that a defect called a ridging mark, which is mainly caused by material anisotropy, occurs. In the conventional hot blow molded product, a phenomenon in which a defect that impairs the smoothness of the appearance after coating is observed as in the case of a ridging mark in the case of cold pressing, and the commercial value is greatly reduced. Since the hot blow molding method is a plastic working method that imparts large deformation, even if the material does not show a decrease in smoothness when performing cold pressing, the above-mentioned hot blow molding method can be used. Defects similar to ridging marks may occur, and conventional hot blow molding materials are inappropriate as materials for automobile body panels and the like.
[0004]
In addition, as a conventional hot blow molding material or its manufacturing method, there exist the technique of patent documents 1-5, for example.
[0005]
[Patent Document 1]
JP 60-238460 A
[Patent Document 2]
JP 60-238461 A
[Patent Document 3]
JP-A 62-96643
[Patent Document 4]
JP-A-7-26342
[Patent Document 5]
JP-A-7-305131
[0006]
[Problems to be solved]
  The present invention has been made in view of such conventional problems, has an appropriate hot blow moldability, suppresses the deterioration of the smoothness of the outer surface of the molded product that occurs during hot blow molding, and has an appearance after coating. High quality plate material for hot blow molding and hot blow molded productManufacturing methodIs to provide.
[0007]
[Means for solving problems]
  1st invention contains Mg: 3.5-6.0% in weight ratio, and Mn: 0.5-0.8% or Cr: 0.05-0.20% Contain 1 or 2 types, further Si content is 0.10% or less, Fe content is 0.12% or less, Cu content is 0.10% or less, the balance is Al and inevitable impurities From an alloyUsing ingot,
  TheThe ingot is hot-rolled after homogenization,
  Furthermore, cold rolling with a cold rolling rate of 25% or more was carried out,
  An intermediate annealing is performed in which the temperature is raised within a temperature range of 400 ° C. to 550 ° C. at a temperature rising rate of 1 ° C./sec or more and held for 5 minutes or less.
  Cold rolling at a cold rolling rate of 25% or more and less than 50% to the final sheet thickness after the intermediate annealing,
  After that, a final annealing is performed in which heating is performed within a temperature range of 400 ° C. to 550 ° C. at a temperature rising rate of 1 ° C./sec or more and holding is performed within 5 minutes.YouAl-Mg-based aluminum alloy sheet for hot blow moldingManufacturing method(Claim 1).
[0008]
As described above, the Al—Mg-based aluminum alloy sheet for hot blow molding of the present invention uses an alloy having a specific component composition and adopts the above specific manufacturing method, thereby improving hot blow moldability and It is intended to suppress a decrease in smoothness of the outer surface of the molded product that occurs during hot blow molding.
First, the significance and reasons for limitation of the components of the alloy constituting the Al—Mg-based aluminum alloy plate for hot blow molding of the present invention (hereinafter referred to as the aluminum alloy plate of the present invention as appropriate) will be described.
[0009]
Mg: 3.5-6.0%;
Mg increases the strength of the product after molding, and promotes dynamic recovery and recrystallization during hot blow molding to compensate for workability that decreases with molding. The preferable content range is 3.5 to 6.0%, and if it is less than 3.5%, the effect of promoting recrystallization is small, and if it exceeds 6.0%, the hot rolling property is inhibited.
[0010]
Mn: 0.5 to 0.8%, Cr: 0.05 to 0.20%;
Mn and Cr stabilize the recrystallized grains during blow molding, give good moldability and appearance quality after molding, and increase the strength after molding. The preferred contents are in the range of 0.5 to 0.8% and 0.05 to 0.20%, respectively, as described above. If both of them fall below the lower limit, the stabilizing effect diminishes and the crystal grains become coarse, leading to deterioration in formability and appearance quality due to rough skin. When the range is exceeded, coarse crystals are formed in the ingot, impairing hot blow moldability, and segregated crystals deteriorate the appearance quality after forming. Further, Mn and Cr are not necessarily contained, and the above effect can be obtained by containing at least one of them.
[0011]
Si content 0.10% or less, Fe content 0.12% or less, Cu content 0.10% or less;
In the present invention, it is important to limit the contents of Fe and Si as impurities to the above amounts. Impurities Fe and Si are insoluble Al-Fe-Si compounds and Mg₂A Si compound is generated, and this compound precipitates at the grain boundary to increase the cavity, thereby decreasing the hot blow moldability and decreasing the strength and elongation after molding. More preferably, both Fe and Si should be limited to 0.05% or less.
Moreover, since Cu inhibits hot rolling properties, it is important to limit it to 0.10% or less.
[0012]
Next, in producing the aluminum alloy sheet of the present invention, first, the ingot is hot-rolled after homogenization and further cold-rolled with a cold rolling rate of 25% or more. If the cold rolling in this case is less than 25%, there is a problem that a desired structural change cannot be obtained in the intermediate annealing described later.
[0013]
After the cold rolling, intermediate annealing is performed in which heating is performed within a temperature range of 400 ° C. to 550 ° C. at a temperature rising rate of 1 ° C./sec or more and holding is performed within 5 minutes. This intermediate annealing is necessary as an intermediate treatment for making a non-uniform hot rolled structure uniform in the final plate. During the intermediate annealing, the hot rolling structure is recrystallized to improve the structure. If intermediate annealing is not performed, non-uniformity remains in the structure of the final plate, and a smooth appearance after blow molding cannot be obtained.
[0014]
Moreover, if the temperature increase rate in the said intermediate annealing is less than 1 degree-C / sec, it will become a non-uniform recrystallizing structure again, and the role of a modification | reformation will become insufficient, and a smooth surface will not be obtained after blow molding. Further, if the holding temperature is less than 400 ° C, recrystallization does not occur sufficiently, and if it exceeds 550 ° C, there is a possibility of melting. Also, heat treatment with a holding time exceeding 5 minutes is not economically significant.
[0015]
After the intermediate annealing, cold rolling is performed again to obtain a uniform isotropic structure by recrystallization by final annealing, and a material having excellent smoothness after blow molding.
The cold rolling after the intermediate annealing is performed at a cold rolling rate of 25% or more and less than 50% up to the final thickness. At this time, if the cold rolling rate is less than 25%, recrystallization does not occur in final annealing, which will be described later, and the desired smoothness cannot be obtained. Further, if it is 50% or more, not only is it not economically significant, but also when hot blow molding is performed on the plate after the final annealing, anisotropy may be caused again to deteriorate the smoothness of the appearance.
[0016]
Thereafter, final annealing is performed in which heating is performed within a temperature range of 400 ° C. to 550 ° C. at a temperature rising rate of 1 ° C./sec or more and holding is performed within 5 minutes. If the rate of temperature increase in the final annealing is less than 1 ° C./sec, a non-uniform recrystallized structure is formed again, and a smooth surface cannot be obtained after blow molding. Further, if the holding temperature at the time of final annealing is less than 400 ° C., recrystallization does not occur sufficiently, and if it exceeds 550 ° C., there is a possibility of melting. Moreover, heat treatment exceeding 5 minutes is not economically significant.
[0017]
  The second invention is,In weight ratio, Mg: 3.5-6.0% and Mn: 0.5-0.8%, or Cr: 0.05-0.20% Furthermore, the alloy is controlled to have an Si content of 0.10% or less, an Fe content of 0.12% or less, and a Cu content of 0.10% or less, with the balance being Al and inevitable impurities.Using ingot,
  TheThe ingot is hot-rolled after homogenization,
  Furthermore, cold rolling with a cold rolling rate of 25% or more was carried out,
  An intermediate annealing is performed in which the temperature is raised within a temperature range of 400 ° C. to 550 ° C. at a temperature rising rate of 1 ° C./sec or more and held for 5 minutes or less.
  Cold rolling at a cold rolling rate of 25% or more and less than 50% to the final sheet thickness after the intermediate annealing,
  After that, a final annealing is performed in which the temperature is raised within a temperature range of 400 ° C. to 550 ° C. at a rate of temperature rise of 1 ° C./sec or more and held within 5 minutes.TheAl-Mg aluminum alloy plate for hot blow moldingMade,
Hot blow molding is performed on the aluminum alloy plate in a temperature range of 400 ° C. or higher.Hot blow molded products characterized byManufacturing method(Claim 6).
[0018]
The hot blow molded product of the present invention uses the excellent aluminum alloy plate according to the first invention described above as a material. Therefore, even if this is heated to a temperature of 400 ° C. or higher and subjected to hot blow molding, the occurrence of defects such as conventional ridging marks can be greatly suppressed. Therefore, the hot blow-molded product of the present invention has a very excellent smoothness and can be applied to various products with severe appearance requirements.
[0019]
  The third invention is,In weight ratio, Mg: 3.5-6.0% and Mn: 0.5-0.8%, or Cr: 0.05-0.20% Furthermore, the alloy is controlled to have an Si content of 0.10% or less, an Fe content of 0.12% or less, and a Cu content of 0.10% or less, with the balance being Al and inevitable impurities.Using ingot,
  TheThe ingot is hot-rolled after homogenization,
  Furthermore, cold rolling with a cold rolling rate of 25% or more was carried out,
  An intermediate annealing is performed in which the temperature is raised within a temperature range of 400 ° C. to 550 ° C. at a temperature rising rate of 1 ° C./sec or more and held for 5 minutes or less.
  Cold rolling at a cold rolling rate of 25% or more and less than 50% to the final sheet thickness after the intermediate annealing,
  Then, a final annealing is performed in which the heating rate is 1 ° C./sec or more and the heating is performed within a temperature range of 400 ° C. to 550 ° C., and the holding is performed within 5 minutes.
  Furthermore, cold rolling is performed at a cold rolling rate of 25% or more and less than 50%,
  After that, a finish heat treatment is performed by heating within a temperature range of 270 ° C. to 400 ° C. at a temperature rising rate of 1 ° C./sec or more and holding within 5 minutes.TheAl-Mg aluminum alloy plate for hot blow moldingMake
  The aluminum alloy sheet is subjected to cold plastic working and then hot blow-molded in a temperature range of 400 ° C. or higher.Hot blow molded products characterized byManufacturing method(Claim 9).
[0020]
As described above, the hot blow molded product of the present invention is manufactured by a special molding method in which the hot blow molding is performed after the cold plastic working. Then, as the aluminum alloy plate as the material, the cold-rolling and finishing heat treatment after the final annealing were further applied to the Al-Mg-based aluminum alloy plate for hot blow molding of the first invention described above. Use things.
As a result, a smooth appearance can be easily obtained without causing defects resulting from the cold plastic working.
The above hot blow-molded product can maintain excellent quality even after hot plastic molding after cold plastic forming, so it has a higher degree of freedom than when only hot blow molding is performed. High shape design is possible, and the added value of the product can be further increased.
[0021]
Here, when the cold rolling rate of the cold rolling after the final annealing is less than 25%, the effect of suppressing coarsening during heating before hot blow molding is not sufficient, and it is economical if it exceeds 50%. In addition to the lack of significance, there are cases where recrystallization before hot blow molding causes anisotropy again to deteriorate the smoothness of the appearance.
[0022]
When the heating rate of the finishing heat treatment is less than 1 ° C./sec, a non-uniform recrystallized structure is formed again in the heating before hot blow molding, and a smooth surface cannot be obtained after hot blow molding. Further, when the holding temperature of the finish heat treatment is less than 270 ° C., it is difficult to guarantee cold workability before hot blow molding, and when it exceeds 400 ° C., non-uniform re-execution is again caused by heating before hot blow molding. A crystal structure may be formed. Also, heat treatment exceeding 5 minutes is not economically significant.
The significance of other component ranges, the reasons for limitation, the significance of the conditions in the production process, and the reasons for limitation are the same as in the case of the first invention described above.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
The ingot in the first invention can be obtained by melting and casting an aluminum alloy having the above composition according to a conventional method. And it is preferable to perform the said homogenization process of this ingot in the temperature range of 450-550 degreeC, for example. If the homogenization temperature is less than 450 ° C, segregation in the ingot cannot be removed, and there is a problem that the hot workability is reduced. On the other hand, if it exceeds 550 ° C, There is a problem that melting occurs.
[0024]
Further, the hot rolling start temperature after the homogenization treatment is preferably, for example, 250 to 500 ° C, and more preferably 400 ° C or less. When the hot rolling start temperature is less than 250 ° C., there is a problem that the deformation resistance of the material is high, the number of rolling passes is increased, and there is no economic advantage. On the other hand, when it exceeds 500 ° C., it is not desirable because it induces cracking during hot rolling, and it is more preferable that the temperature is 400 ° C. or less as described above.
[0025]
Moreover, in this invention, after performing the said hot rolling, it heats within the temperature range of 300 to 500 degreeC in a batch furnace, and performs the intermediate annealing before cold rolling which hold | maintains for 1 to 10 hours. (Claim 2).
This intermediate annealing before cold rolling is not an essential process, but is preferably added because it can reduce the rolling load in the subsequent cold rolling.
[0026]
When the intermediate annealing before cold rolling is added, the batch furnace is used as described above, and the heating temperature is set in the range of 300 ° C to 500 ° C. When the heating temperature is less than 300 ° C., there is a problem that the above rolling load reduction effect cannot be obtained. On the other hand, when the heating temperature exceeds 500 ° C., Mg is concentrated on the surface layer, and an Mg oxide layer is formed on the plate surface, which causes a problem that the surface quality is remarkably deteriorated.
Further, when the holding time is less than 1 hour, the above rolling load reduction effect cannot be obtained. On the other hand, when the holding time exceeds 10 hours, the same problem as when the heating temperature exceeds 500 ° C. is likely to occur. Furthermore, even if it is held for 10 hours or more, there is no change in the rolling load reduction effect, which only increases the industrial cost.
[0027]
In the present invention, it is preferable that the alloy further contains Be: 20 to 80 ppm. In this case, the oxidation of the molten metal can be prevented, and the appearance quality abnormality caused by the entanglement of the oxide into the ingot can be prevented as in the case of a normal Al—Mg alloy. When the content of Be is less than 20 ppm, such an antioxidant effect is not obtained so much. On the other hand, when it exceeds 80 ppm, the effect is saturated and the environment is not desirable.
[0028]
In addition, after the final annealing, cold rolling is further performed at a cold rolling rate of 25% or more and less than 50%, and then within a temperature range of 270 ° C. to 400 ° C. at a temperature rising rate of 1 ° C./sec or more. It is preferable to carry out a finish heat treatment for heating and holding within 5 minutes. In this case, it is possible to more effectively improve the hot blow moldability and suppress the deterioration of the smoothness of the outer surface of the molded product that occurs during the hot blow molding. In particular, it is very effective in improving hot blow moldability in applications where cold working is performed before hot blow molding.
[0029]
When the cold rolling ratio of the cold rolling after the final annealing is less than 25%, the effect of suppressing coarsening during heating before hot blow molding is not sufficient, and if it exceeds 50%, it is economically significant. In addition to being poor, there are cases where recrystallization before hot blow molding causes anisotropy again to deteriorate the smoothness of the appearance.
[0030]
When the heating rate of the finishing heat treatment is less than 1 ° C./sec, a non-uniform recrystallized structure is formed again in the heating before hot blow molding, and a smooth surface cannot be obtained after hot blow molding. Further, when the holding temperature of the finish heat treatment is less than 270 ° C., it is difficult to guarantee cold workability before hot blow molding, and when it exceeds 400 ° C., non-uniform re-execution is again caused by heating before hot blow molding. A crystal structure may be formed. Also, heat treatment exceeding 5 minutes is not economically significant.
[0031]
  Also, the aboveAluminum alloy plateIs preferably a vehicle body panel material.
  Car body panel materials require clearness after painting. The sharpness is strongly influenced by the appearance of the molded product, particularly the smoothness, and the flatter the higher the sharpness. The smoothness of the surface of the molded product is achieved by the uniform deformation of the material during hot blow molding. Molded products with poor clarity show uneven deformation during hot blow molding. This is due to the non-uniformity of the metal structure of the plate before blow molding. These non-uniformities are affected by the non-uniform recrystallization structure and strong cold rolling that occur during hot rolling.
  In this respect, the above-described excellent aluminum alloy plate of the present invention is applied to the above-mentioned automotive body panel material, thereby preventing the non-uniformity of the metal structure and realizing an excellent sharpness. Can be obtained.
  Examples of the vehicle body panel include so-called outer materials such as bonnet hoods, trunk lids, roofs, doors, and the like, and various inner materials whose appearance characteristics are required.
[0032]
Next, in the second and third inventions, the Al—Mg-based aluminum alloy sheet for hot blow forming is subjected to the hot rolling, and then is in a temperature range of 300 ° C. to 500 ° C. in a batch furnace. It is preferable that an intermediate annealing before cold rolling which is heated for 1 hour to 10 hours is performed (Claim 7 and Claim 10). In this case, as described above, an effect of reducing the rolling load of cold rolling after hot rolling in the manufacturing method can be obtained.
[0033]
In the second invention, the Al-Mg aluminum alloy sheet for hot blow molding is further subjected to cold rolling at a cold rolling rate of 25% or more and less than 50% after the final annealing. After that, it is preferable that a finishing heat treatment is performed in which heating is performed within a temperature range of 270 ° C. to 400 ° C. at a temperature rising rate of 1 ° C./sec or more and the holding is performed within 5 minutes (Claim 8).
In this case, it is possible to obtain a hot blow molded article having further excellent smoothness.
[0034]
In the second and third inventions as well, for the same reason as described above, the alloy preferably further contains Be: 20 to 80 ppm.
The hot blow-molded product is preferably a vehicle body panel. That is, as described above, the hot blow-molded product can maintain excellent quality even after hot plastic molding after cold plastic working, as compared with the case where only hot blow molding is performed. However, shape design with a high degree of freedom is possible. Therefore, it is possible to easily cope with the vehicle body panel for automobiles, which is important for design.
[0035]
【Example】
(Example 1)
In this example, as shown in Table 1, six types of aluminum alloy plates (samples E11 to E16) as the product of the present invention and four types of aluminum alloy plates (sample C11) as comparative products whose component ranges deviated from the scope of the present invention. To C14) and their characteristics were compared.
[0036]
[Table 1]

[0037]
First, slabs having the alloy components shown in Table 1 were produced by semi-continuous casting. These alloys were homogenized by holding at 500 ° C. for 8 hours, and after surface chamfering, they were heated to 395 ° C. and hot rolled to obtain 3.9 mm hot rolled sheets.
Next, cold rolling (cold rolling rate 50%) → intermediate annealing (heating rate 10 ° C./sec, holding temperature 500 ° C., holding time 30 seconds) → cold rolling (cold rolling) The rolling ratio was 33%) → final annealing (temperature increase rate 10 ° C./sec, holding temperature 500 ° C., holding time 30 seconds) was sequentially performed to obtain an aluminum alloy plate having a thickness of 1.3 mm.
[0038]
Next, the obtained aluminum alloy plate was cut into a square shape of 350 mm square to obtain a test piece, and hot blow molding was actually performed. Specifically, the test piece was heated to 490 ° C. and hot blow molded into a rectangular tube shape of 250 mmW × 250 mmL × 65 mmH by a female die. The thickness of the bottom center portion was 0.85 mm, and the thickness reduction rate was about 34.6%.
[0039]
Next, the mechanical properties of the central part of the obtained rectangular tube molded product were measured by a tensile test. Similarly, a 100-mm square test piece was cut from the center, pickled, and applied to general automobiles, and the quality (sharpness) of the coating film was evaluated with a tension meter.
[0040]
Here, the evaluation of the tension meter is performed using a photographing device 5 as shown in FIG.
The photographing apparatus 5 includes a TP storage portion 51 that covers the test piece 1, a strobe portion 52 and a camera portion 53 that are disposed on the side wall portion thereof.
[0041]
The strobe unit 52 has a cylindrical entrance-side light guide unit 521, a strobe 522 serving as a light source is disposed at one end, and light emitted from the strobe 522 is disposed at the other end. A slit plate 523 is provided to block the screen.
The camera unit 52 has a camera 532 for setting a film via a cylindrical exit-side light guide unit 531.
[0042]
Then, the photographing device 5 operates the shutter 55 provided on the exit-side light guide unit 531 to emit light from the strobe 522 and strikes the light on the surface of the test piece 1 through the slit plate 523. Is reflected and photographed on a film by a camera 532.
[0043]
As shown in FIG. 2, the slit plate 523 is divided into 12-step score areas from 9 to 20. Each region is provided with a slit so that a plurality of parallel rays (slit light) can be obtained, and the interval between the slits is set to be narrower as the region has a higher score. In this example, the width dimension (thickness) of the slit S is uniformly 0.20 mm. The interval (pitch) of the slits S was set as shown in Table 2.
[0044]
[Table 2]

[0045]
The tension meter was evaluated using a photograph taken by the photographing device 5 with the sample to be evaluated placed on the placement position of the test piece 1. Specifically, a plurality of slit lights appearing in the photograph are visually observed for each region, and it is determined whether or not there is an overlap between adjacent slit lights. Then, the maximum score among the areas where no overlap was observed in the slit light was used as the evaluation value.
This evaluation method is an evaluation method generally used in automobile manufacturers and the like.
[0046]
These evaluation results are shown in Table 3. In Table 3, ○ indicates pass and × indicates fail. Regarding the quality after painting, those having a tension meter evaluation value of 15 or more were regarded as acceptable. Moreover, since the dent resistance is required as a vehicle body panel material for automobiles, a material having a proof stress of 110 MPa or more was accepted. In addition, since workability in post-processing such as hem processing is required, a product having an elongation of 15% or more was accepted. With regard to the sharpness after painting (tension meter evaluation value), an evaluation value of 15 or more was accepted.
[0047]
[Table 3]

[0048]
As is known from Table 3, the samples E11 to E16, which are the products of the present invention, passed all evaluations of proof stress, elongation, and tension meter.
On the other hand, Comparative Example C11 had a low yield strength due to the small amount of Mg added, and the crystal grain size during blow molding increased, resulting in a rough appearance and the evaluation of the tension meter failed.
In Comparative Example C12, since the amount of Mg added was too high, the plate was cracked during hot working and could not be evaluated.
In Comparative Example C13, Mn and Cr were not added, and the crystal grain size during blow molding was increased, so that the appearance of the skin was rough, and the tension meter was not evaluated.
In Comparative Example C14, since the amount of Fe and Si was large, cavitation occurred during blow molding, and the elongation failed.
[0049]
(Example 2)
In this example, the slab is semi-continuous with a composition of Al-4.8% Mg-0.7% Mn-0.15% Cr-0.02% Si-0.02% Fe-0.01% Cu-50ppmBe. Made by casting. The slab was homogenized by holding it at a temperature of 500 ° C. for 8 hours. After chamfering, it was heated to 395 ° C. to produce a hot rolled plate. Subsequently, a 1.3 mm plate was prepared according to the steps in Table 4. Was made. Steps E21, E22, and E23 in Table 4 are the methods of the present invention, and steps C21 to C30 employ steps different from the present invention for comparison. Of these, Steps E23, C29, and C30 are those in which intermediate annealing before cold rolling in a batch furnace is performed after hot rolling.
[0050]
[Table 4]

[0051]
Next, the obtained aluminum alloy plate having a thickness of 1.3 mm was cut into a square shape of 350 mm square to obtain a test piece, and hot blow molding was actually performed. Specifically, in the same manner as in Example 1, the test piece was heated to 490 ° C. and hot blow-molded into a rectangular tube shape of 250 mmW × 250 mmL × 65 mmH with a female die. The thickness of the bottom center portion was 0.85 mm, and the thickness reduction rate was about 34.6%.
[0052]
Next, as in Example 1, the mechanical properties of the central part of the obtained rectangular tube molded product were measured by a tensile test. Similarly, a 100-mm square test piece was cut from the center, pickled, and applied to general automobiles, and the quality (sharpness) of the coating film was evaluated with a tension meter. The evaluation method using a tension meter is the same as that in the first embodiment.
In this example, in addition to the evaluation with a tension meter, the surface of the blow-molded product was evaluated by appearance observation. Specifically, it is visually observed whether the mottled pattern due to Mg oxide on the surface of the sheet after the intermediate annealing before cold rolling has streak-like dirt extended by subsequent rolling, and the dirt is observed. The case where it was done was marked as x, and the case where the surface was clean and beautiful was marked as ◯. Then, the surface evaluation of the blow molded product and the above tension meter evaluation were integrated to make a comprehensive determination. The evaluation results are shown in Table 5. In Table 5, ○ indicates pass and × indicates failure.
[0053]
[Table 5]

[0054]
As is known from Table 5, a satisfactory appearance was obtained for the molded product obtained by hot blow molding the aluminum alloy plate obtained in steps E21 and E22.
On the other hand, since the intermediate annealing was omitted in the process C21, the uneven structure of the hot rolled sheet could not be improved, and the evaluation was inferior.
In the process C22, since the cold rolling rate before the intermediate annealing was low, the non-uniform structure of the hot rolled sheet could not be improved without recrystallization by the intermediate annealing, and the evaluation was inferior.
In the process C23, the rolling rate before the final annealing was too high, resulting in a strong shear structure. The structure after the final annealing was changed and became non-uniform, resulting in poor evaluation.
[0055]
Processes C24 and C25 were not recrystallized because the intermediate or final annealing temperature was too low, and the uneven structure of the hot-rolled sheet could not be improved, resulting in poor evaluation.
Processes C26 and C27 were inferior in evaluation because the rate of temperature increase during intermediate or final annealing was too low, and recrystallization occurred nonuniformly, and the heterogeneous structure of the hot-rolled sheet could not be improved.
In process C28, since the cold rolling rate before the final annealing was low, recrystallization did not occur in the final annealing, and the uneven structure of the rolled sheet could not be improved, resulting in poor evaluation.
[0056]
Moreover, process E23 implemented intermediate annealing before cold rolling as mentioned above, and was able to perform rolling easily with small load in subsequent cold rolling (cold rolling 1). The surface of the resulting blow-molded product was beautiful and excellent in surface quality.
[0057]
On the other hand, in steps C29 and C30, although the intermediate annealing before cold rolling was performed, the heating temperature and holding time exceed the range of the present invention (Claim 2). In both cases, the cold rolling (cold rolling 1) load after the intermediate annealing before cold rolling was small and could be easily rolled, but on the sheet surface after the intermediate annealing before cold rolling, A mottled pattern due to Mg oxide was generated, and the surface quality was poor.
[0058]
(Example 3)
In this example, the slab is semi-continuous with a composition of Al-4.8% Mg-0.7% Mn-0.15% Cr-0.02% Si-0.02% Fe-0.01% Cu-50ppmBe. Made by casting. The slab was subjected to a homogenization treatment for holding at a temperature of 500 ° C. for 8 hours, and after hot facing, heated to 395 ° C. and hot-rolled. Next, cold rolling (cold rolling rate: 50%) → intermediate annealing (heating rate: 10 ° C./sec, holding temperature: 500 ° C., holding time: 30 seconds) → cold rolling for the obtained hot rolled sheet (Cold rolling rate: 33%) → Final annealing (temperature increase rate: 10 ° C./sec, holding temperature: 500 ° C., holding time: 30 seconds) was sequentially performed to obtain an aluminum alloy sheet as an intermediate material.
[0059]
In this example, as shown in Table 6, the aluminum alloy plate as the intermediate material was further subjected to cold rolling and finish heat treatment, and the effects were evaluated. Note that the thickness of the hot-rolled sheet was adjusted so that the final sheet thickness was 1.3 mm regardless of which process was selected.
As the cold rolling after the final annealing, in addition to the step E31 in which the cold rolling rate was 33%, comparative steps C31 and C32 in which the cold rolling rate was changed to 5% and 65% were also performed. In each step, the finish heat treatment was performed under the conditions of a heating rate of 10 ° C./sec, a holding temperature of 350 ° C., and a holding time of 5 seconds.
[0060]
[Table 6]

[0061]
Next, the obtained aluminum alloy plate was cut into a square shape of 350 mm square to obtain a test piece. In this example, the test piece was first subjected to cold working to bend and then bend R3. Thereafter, in the same manner as in Example 1, the test piece was heated to 490 ° C. and hot blow-molded into a rectangular tube shape of 250 mmW × 250 mmL × 65 mmH by a female die.
Next, a 100 mm square test piece was cut out from the central portion of the obtained rectangular tube molded product, pickled, and then applied to general automobiles, and the quality (sharpness) of the coating film was evaluated with a tension meter.
The evaluation method is the same as in Example 1. Table 7 shows the evaluation results.
[0062]
[Table 7]

[0063]
The thing of the process E31 exhibited the favorable external appearance.
In step C31, a hook-like defect occurred along the crease that was bent and bent back. In addition, since the degree of cold work was small, non-evaluation was judged to be impossible because non-uniform recrystallization (coarse graining) occurred during heating to the hot blow molding temperature in the part subjected to bending.
Since the rolling rate before the heat treatment was too high in the process C32, the result was that a strong shear structure was formed, and the non-uniform recrystallization along the shear occurred during heating to the hot blow molding temperature, so the evaluation was poor.
[0064]
From the results of this example, the aluminum alloy sheet used for the application of cold working before hot blow molding is at least a cold rolling rate of 25% or more and less than 50% after the final annealing. It can be seen that it is effective to perform rolling and then finish heat treatment to heat within a temperature range of 270 ° C. to 400 ° C. at a temperature rising rate of 1 ° C./sec or more and hold within 5 minutes.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing a photographing apparatus for measuring a tension meter in Embodiment 1. FIG.
2 is an explanatory diagram showing a slit arrangement of a slit plate in Example 1. FIG.
[Explanation of symbols]
1. . . Test piece,
5. . . Photographing device,
50. . . Base 50,
51. . . TP storage unit,
52. . . Strobe section,
53. . . Camera unit 53,

Claims (12)

In weight ratio, Mg: 3.5-6.0% and Mn: 0.5-0.8%, or Cr: 0.05-0.20% Furthermore, the ingot is made of an alloy of which the Si content is 0.10% or less, the Fe content is 0.12% or less, the Cu content is 0.10% or less, and the balance is Al and inevitable impurities. Use
Hot rolled after homogenization the ingot,
Furthermore, cold rolling with a cold rolling rate of 25% or more was carried out,
An intermediate annealing is performed in which the temperature is raised within a temperature range of 400 ° C. to 550 ° C. at a temperature rising rate of 1 ° C./sec or more and held for 5 minutes or less.
Cold rolling at a cold rolling rate of 25% or more and less than 50% to the final sheet thickness after the intermediate annealing,
Thereafter, Al-Mg-based for hot blow molding, characterized in that to facilities for final annealing of heating and Hold within 5 minutes within a temperature range of 400 ° C. to 550 ° C. at a heating rate 1 ° C. / sec or higher A method for producing an aluminum alloy plate. In Claim 1, after performing the said hot rolling, it heats within the temperature range of 300 to 500 degreeC in a batch furnace, and performs the intermediate annealing before cold rolling which hold | maintains for 1 to 10 hours. A method for producing an Al—Mg-based aluminum alloy plate for hot blow molding. 3. The method for producing an Al—Mg-based aluminum alloy plate for hot blow molding according to claim 1, wherein the alloy further contains Be: 20 to 80 ppm. In any 1 paragraph of Claims 1-3, after giving the above-mentioned final annealing, it cold-rolls with a cold rolling rate of 25% or more and less than 50%, and then with a temperature increase rate of 1 ° C / sec or more method for producing a 270 ° C. to 400 ° C. hot blow molding Al-Mg series aluminum alloy sheet, characterized in that to facilities finish heat treatment for heating and hold within 5 minutes within a temperature range of. 5. The method for producing an Al—Mg-based aluminum alloy plate for hot blow molding according to claim 1, wherein the aluminum alloy plate is an automobile body panel material. In weight ratio, Mg: 3.5-6.0% and Mn: 0.5-0.8%, or Cr: 0.05-0.20% Furthermore, the ingot is made of an alloy of which the Si content is 0.10% or less, the Fe content is 0.12% or less, the Cu content is 0.10% or less, and the balance is Al and inevitable impurities. Use
Hot rolled after homogenization the ingot,
Furthermore, cold rolling with a cold rolling rate of 25% or more was carried out,
An intermediate annealing is performed in which the temperature is raised within a temperature range of 400 ° C. to 550 ° C. at a temperature rising rate of 1 ° C./sec or more and held for 5 minutes or less.
Cold rolling at a cold rolling rate of 25% or more and less than 50% to the final sheet thickness after the intermediate annealing,
Then, prepare a hot blow molding Al-Mg series aluminum alloy plate is subjected to final annealing for holding within five minutes by heating to a temperature range of 400 ° C. to 550 ° C. at a heating rate 1 ° C. / sec or higher And
A method for producing a hot blow molded product , comprising subjecting the aluminum alloy plate to hot blow molding in a temperature range of 400 ° C. or higher . In Claim 6, after performing the said hot rolling, it heated in the temperature range of 300 to 500 degreeC in a batch furnace, and performed the intermediate annealing before cold rolling which hold | maintains for 1 hour-10 hours. A method for producing a hot blow molded product. In Claim 6 or 7, after performing the said last annealing, it cold-rolls with the cold rolling rate of 25% or more and less than 50%, and is 270 degreeC-400 degreeC after that with a temperature increase rate of 1 degree-C / sec or more. A method for producing a hot blow-molded product , characterized in that a finish heat treatment is performed in which the heat treatment is carried out within a temperature range of 5 minutes and held for 5 minutes or less. In weight ratio, Mg: 3.5-6.0% and Mn: 0.5-0.8%, or Cr: 0.05-0.20% Furthermore, the ingot is made of an alloy of which the Si content is 0.10% or less, the Fe content is 0.12% or less, the Cu content is 0.10% or less, and the balance is Al and inevitable impurities. Use
Hot rolled after homogenization the ingot,
Furthermore, cold rolling with a cold rolling rate of 25% or more was carried out,
An intermediate annealing is performed in which the temperature is raised within a temperature range of 400 ° C. to 550 ° C. at a temperature rising rate of 1 ° C./sec or more and held for 5 minutes or less.
Cold rolling at a cold rolling rate of 25% or more and less than 50% to the final sheet thickness after the intermediate annealing,
Then, a final annealing is performed in which the heating rate is 1 ° C./sec or more and the heating is performed within a temperature range of 400 ° C. to 550 ° C., and the holding is performed within 5 minutes.
Furthermore, cold rolling is performed at a cold rolling rate of 25% or more and less than 50%,
Then, prepare a heating rate 1 ° C. / sec or more at 270 ° C. to 400 ° C. hot blow molding Al-Mg series aluminum alloy sheet is subjected to finish heat treatment for holding within five minutes by heating in a temperature range of And
A method for producing a hot blow-molded product , wherein the aluminum alloy plate is subjected to cold plastic working and then subjected to hot blow molding in a temperature range of 400 ° C or higher . In Claim 9, after performing the said hot rolling, it heated in the temperature range of 300 to 500 degreeC in a batch furnace, and performed the intermediate annealing before cold rolling which hold | maintains for 1 hour-10 hours. A method for producing a hot blow molded product. The method for producing a hot blow molded article according to any one of claims 6 to 10, wherein the alloy further contains Be: 20 to 80 ppm. The method of manufacturing a hot blow molded product according to any one of claims 6 to 11, wherein the hot blow molded product is an automobile body panel.

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