JP6165687B2 - Aluminum alloy plate - Google Patents

Aluminum alloy plate Download PDF

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JP6165687B2
JP6165687B2 JP2014161498A JP2014161498A JP6165687B2 JP 6165687 B2 JP6165687 B2 JP 6165687B2 JP 2014161498 A JP2014161498 A JP 2014161498A JP 2014161498 A JP2014161498 A JP 2014161498A JP 6165687 B2 JP6165687 B2 JP 6165687B2
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aluminum alloy
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松本 克史
克史 松本
有賀 康博
康博 有賀
健太郎 伊原
健太郎 伊原
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株式会社神戸製鋼所
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本発明は、伸びフランジ性、高強度、耐食性を各々兼備し、通常の圧延によって製造される、7000系アルミニウム合金板に関するものである。   The present invention relates to a 7000 series aluminum alloy sheet that has stretch flangeability, high strength, and corrosion resistance, and is manufactured by ordinary rolling.
構造材料として自動車の例を取ると、近年、地球環境などへの配慮から、自動車車体の軽量化の社会的要求はますます高まってきている。かかる要求に答えるべく、自動車車体のうち、パネル(フード、ドア、ルーフなどのアウタパネル、インナパネル)や、バンパリーンフォース(バンパーR/F)やドアビームなどの補強材などを、部分的に鋼板等の鉄鋼材料に代えて、アルミニウム合金材料を適用することが行われている。   Taking automobiles as an example of a structural material, in recent years, social demands for reducing the weight of automobile bodies are increasing due to consideration for the global environment. In order to meet such demands, panels (outer panels such as hoods, doors, and roofs, inner panels), bumper force (bumper R / F), and reinforcing materials such as door beams, etc., are partly made of steel, etc. Instead of the steel material, an aluminum alloy material is applied.
ただ、自動車車体のより軽量化のためには、自動車部材のうちでも特に軽量化に寄与する、フレーム、ピラーなどの構造部材にも、アルミニウム合金材料の適用を拡大することが必要となる。ただ、これら自動車構造部材は、要求される0.2%耐力が350MPa以上であるなど、前記自動車パネルに比べて、高強度化が必要である。このような高強度な自動車構造部材には、同じような高強度が要求される前記補強材として使用されているJIS乃至AA 7000系アルミニウム合金を用いる必要がある。   However, in order to reduce the weight of the automobile body, it is necessary to expand the application of the aluminum alloy material to structural members such as frames and pillars that contribute particularly to weight reduction among the automobile members. However, these automobile structural members need to have higher strength than the above-mentioned automobile panels, for example, the required 0.2% proof stress is 350 MPa or more. For such a high-strength automobile structural member, it is necessary to use a JIS to AA7000 series aluminum alloy that is used as the reinforcing material that requires the same high strength.
これら7000系アルミニウム合金のうち、熱間押出加工により製造される押出材は、バンパ補強材やドアビームなどの自動車構造部材の補強材として、既に汎用されている。これに対して、鋳塊を均熱処理後に熱間圧延する、あるいは更に冷間圧延するような、常法によって製造される圧延板は、高合金ゆえのつくりにくさもあって、これまであまり実用化されていない。   Among these 7000 series aluminum alloys, extruded materials produced by hot extrusion are already widely used as reinforcing materials for automobile structural members such as bumper reinforcing materials and door beams. On the other hand, rolled plates produced by conventional methods, such as hot rolling after soaking and further cold rolling of the ingot, are difficult to make due to the high alloy, and so far have been less practical. It has not been converted.
ただ近年、この高強度な7000系アルミニウム合金圧延板(以下、7000系アルミニウム合金板、あるいは単に板とも言う)を、鋼板等の鉄鋼材料に代えて、自動車構造部材を始め、自転車、鉄道車両などの構造部材に適用する検討が行われている。   However, in recent years, this high-strength 7000 series aluminum alloy rolled plate (hereinafter also referred to as 7000 series aluminum alloy plate or simply referred to as plate) is replaced with steel materials such as steel plates, automobile structural members, bicycles, railway vehicles, etc. The application to the structural member is being studied.
7000系アルミニウム合金板を構造部材に適用する場合には、素材板を構造部材形状にプレス成形などの加工を行う。この際、構造部材として他の部材との、取り付けやボルト等の機械的接合のために、伸びフランジ加工(バーリング加工、穴拡げ加工)が必要となる。このため、これらの構造部材用の7000系アルミニウム合金板は、この伸びフランジ加工における加工性(成形性)が必要で、このために板の伸びフランジ性をより向上させる必要がある。   When a 7000 series aluminum alloy plate is applied to a structural member, the material plate is processed into a shape of the structural member such as press molding. In this case, stretch flange processing (burring processing, hole expansion processing) is necessary for attachment to other members as structural members and mechanical joining such as bolts. For this reason, the 7000 series aluminum alloy plate for these structural members needs workability (formability) in this stretch flange processing, and for this reason, it is necessary to further improve the stretch flangeability of the plate.
しかし、この伸びフランジ性について、7000系アルミニウム合金板の特性を向上させた技術は、これまで殆ど提案がない。   However, there has been almost no proposal for a technique for improving the characteristics of the 7000 series aluminum alloy plate for the stretch flangeability.
ちなみに、7000系アルミニウム合金押出材の分野では、その実用化の早さや多さに比例して、強度と耐SCC性を向上させるための、組成制御例や析出物などの組織制御例が多数存在する。これに対して、7000系アルミニウム合金板における、組成や析出物、集合組織などの組織の制御例は、板での実用化例の少なさに比例して、元々数が少ない。   By the way, in the field of 7000 series aluminum alloy extruded materials, there are many examples of composition control and structure control such as precipitates to improve strength and SCC resistance in proportion to the speed and number of practical applications. To do. On the other hand, in the 7000 series aluminum alloy plate, the number of examples of control of the structure such as composition, precipitates, and texture is originally small in proportion to the small number of practical examples of the plate.
この数少ない7000系アルミニウム合金板の集合組織の制御例として、特許文献1、2では、構造材用の板の高強度化、高耐SCC性化を図るために、鋳塊を鍛造後に、温間加工域にて繰り返して圧延して、板組織を細かくしている。これは、板組織を細かくすることによって、耐SCC性低下の原因となる粒界と粒内との電位差の要因となる、方位差が20°以上の大傾角粒界を抑制して、3〜10°の小傾角粒界が25%以上である集合組織を得るためである。ただ、特許文献1、2が、このような特殊な温間圧延の繰り返しを行うのは、通常の熱間圧延、冷間圧延の製造方法では、このような小傾角粒界が多い集
合組織を得ることができないためである。したがって、通常の製造方法とは、その工程が大きく異なるため、板の製造方法としては実用的ではない。
As an example of control of the texture of the few 7000 series aluminum alloy plates, in Patent Documents 1 and 2, in order to increase the strength of the structural material plate and increase the SCC resistance, the ingot is warmed after forging. The plate structure is finely rolled by repeatedly rolling in the processing area. This is because, by making the plate structure fine, a large tilt grain boundary with a misorientation of 20 ° or more, which causes a potential difference between the grain boundary and the grain boundary, which causes a decrease in SCC resistance, This is to obtain a texture in which the 10 ° small-angle grain boundary is 25% or more. However, Patent Documents 1 and 2 repeat such a special warm rolling because a texture having a large number of such low-angle grain boundaries is used in a normal hot rolling or cold rolling manufacturing method. It is because it cannot be obtained. Therefore, since the process is greatly different from a normal manufacturing method, it is not practical as a method for manufacturing a plate.
なお、この集合組織の制御に関して、7000系アルミニウム合金の板ではなく押出材ではあるが、特許文献3では、温間加工性に優れさせるために、亜結晶粒からなる繊維状組織で構成し、主方位がBrass方位であり、ODF(結晶方位分布関数)で表現されるBrass方位への集積度がランダム方位の10倍以上とした集合組織の提案もある。   In addition, regarding the control of this texture, it is an extruded material instead of a 7000 series aluminum alloy plate, but in Patent Document 3, in order to improve the warm workability, it is composed of a fibrous structure composed of sub-crystal grains, There is also a proposal of a texture in which the main orientation is the Brass orientation and the degree of integration in the Brass orientation expressed by ODF (crystal orientation distribution function) is 10 times or more of the random orientation.
特開2001−335874号公報JP 2001-335874 A 特開2002−241882号公報Japanese Patent Laid-Open No. 2002-241882 特開2009−114514号公報JP 2009-114514 A
以上の通り、7000系アルミニウム合金板について、伸びフランジ性を向上させた技術、そして、構造部材用として、この伸びフランジ性と、高強度、そして耐食性を兼備させることについては、これまで殆ど提案がない。このため、通常の圧延によって製造される7000系アルミニウム合金板に、伸びフランジ性、高強度、耐食性を各々兼備させる組織制御技術については、未だ有効な手段が不明で、解明乃至改善の余地がある。   As described above, with regard to the 7000 series aluminum alloy plate, there have been almost no proposals for the technology that has improved the stretch flangeability, and for the use of the stretch flangeability, high strength, and corrosion resistance for structural members. Absent. For this reason, there is still room for elucidation or improvement regarding the structure control technology that combines stretch flangeability, high strength, and corrosion resistance with a 7000 series aluminum alloy plate produced by ordinary rolling. .
このような状況に鑑み、本発明の目的は、7000系アルミニウム合金板に、伸びフランジ性、高強度、耐食性を各々兼備させる組織制御技術を提案することである。そして、伸びフランジ性、高強度、耐食性を各々兼備し、通常の圧延によって製造される構造部材用の7000系アルミニウム合金板を提供することである。   In view of such a situation, an object of the present invention is to propose a structure control technique in which a 7000 series aluminum alloy plate has stretch flangeability, high strength, and corrosion resistance. And it is providing the 7000 series aluminum alloy plate for structural members which combines stretch flangeability, high intensity | strength, and corrosion resistance, respectively, and is manufactured by normal rolling.
この目的を達成するために、本発明の構造部材用アルミニウム合金板の要旨は、質量%で、Zn:3.0〜6.0%、Mg:1.5〜4.5%、Cu:0.05〜0.5%を各々含有し、残部がAl及び不可避的不純物からなり、
等軸な再結晶組織として、平均結晶粒径が50μm以下であるとともに、
これらの結晶粒のうち、Cube方位を有する結晶粒の面積率[Cube]とCR方位を有する結晶粒の面積率[CR]とが、
[Cube]+[CR]≧10%、
0.33≦[Cube]/[CR]≦3.0の関係を各々満足するとともに、
前記結晶粒のうち、Brass方位を有する結晶粒の面積率[Brass]と、S方位を有する結晶粒の面積率[S]と、Cu方位を有する結晶粒の面積率[Cu]とが、
[Brass]+[S]+[Cu]<30%の関係を満足する、
集合組織を有することとする。
In order to achieve this object, the gist of the aluminum alloy plate for a structural member of the present invention is mass%, Zn: 3.0 to 6.0%, Mg: 1.5 to 4.5%, Cu: 0 0.05 to 0.5% each, the balance consisting of Al and inevitable impurities,
As an equiaxed recrystallized structure, the average crystal grain size is 50 μm or less,
Among these crystal grains, the area ratio [Cube] of crystal grains having a Cube orientation and the area ratio [CR] of crystal grains having a CR orientation are:
[Cube] + [CR] ≧ 10%,
Each satisfies the relationship of 0.33 ≦ [Cube] / [CR] ≦ 3.0,
Among the crystal grains, the area ratio [Brass] of the crystal grains having the Brass orientation, the area ratio [S] of the crystal grains having the S orientation, and the area ratio [Cu] of the crystal grains having the Cu orientation are:
Satisfies the relationship of [Brass] + [S] + [Cu] <30%.
It shall have a texture.
本発明では、溶体化および焼入れ処理後の7000系アルミニウム合金板の集合組織に着目して、伸びフランジ性との関係を解析した。その結果、伸びフランジ性は、特定の集合組織の量的関係が支配していることを見出し、それらを精緻に制御することで、強度と成形性のバランスを向上させたものである。   In the present invention, focusing on the texture of the 7000 series aluminum alloy plate after solution treatment and quenching, the relationship with stretch flangeability was analyzed. As a result, it has been found that the stretch flangeability is governed by the quantitative relationship of a specific texture, and the balance between strength and formability is improved by precisely controlling them.
本発明では、通常の圧延法によって製造された7000系アルミニウム合金板の組織を、等軸で微細な再結晶組織とした上で、これらの結晶粒のうち、Cube方位を有する結晶粒とCR方位を有する結晶粒とを一定の相互割合で一定量以上存在させるとともに、更に前記結晶粒のうち、Brass方位を有する結晶粒、S方位を有する結晶粒、Cu方位を有する結晶粒を規制する。そして、これによって、強度と成形性のバランスを向上させ、伸びフランジ性を向上させる。そして、前記7000系アルミニウム合金板に、伸びフランジ性、高強度、耐食性を各々兼備させる。   In the present invention, the structure of a 7000 series aluminum alloy plate produced by a normal rolling method is made into an equiaxed and fine recrystallized structure, and among these crystal grains, the crystal grains having the Cube orientation and the CR orientation In addition, a crystal grain having a Brass orientation, a crystal grain having an S orientation, and a crystal grain having a Cu orientation are regulated among the crystal grains. And thereby, the balance between strength and formability is improved, and stretch flangeability is improved. The 7000 series aluminum alloy plate is provided with stretch flangeability, high strength, and corrosion resistance.
本発明で言うアルミニウム合金板とは、鋳塊を均熱処理後に熱間圧延され、更に冷間圧延された冷延板であって、更に溶体化処理などの調質が施される、通常の圧延法によって製造された7000系アルミニウム合金板のことを言う。言い換えると、前記特許文献1、2のような、鋳塊を鍛造した上で温間圧延を何回も繰り返すような特殊な圧延方法や製法により製造される板を含まない。   The aluminum alloy sheet referred to in the present invention is a cold-rolled sheet that is hot-rolled after the soaking of the ingot and further cold-rolled, and is further subjected to tempering such as solution treatment. It means a 7000 series aluminum alloy plate manufactured by the method. In other words, it does not include a plate manufactured by a special rolling method or manufacturing method in which warm rolling is repeated many times after forging an ingot as in Patent Documents 1 and 2.
このような7000系アルミニウム合金板は、本発明で課題とする伸びフランジ性が要求される伸びフランジ加工(バーリング加工、穴拡げ加工)などを含む、プレス成形や加工が施された上で、自動車、自転車、鉄道車両などの構造部材とされる。   Such a 7000 series aluminum alloy sheet is subjected to press molding and processing including stretch flange processing (burring processing, hole expansion processing) and the like required for stretch flangeability, which is a subject of the present invention. And structural members such as bicycles and railway vehicles.
以下に、本発明の実施の形態につき、要件ごとに具体的に説明する。   Hereinafter, embodiments of the present invention will be specifically described for each requirement.
アルミニウム合金組成:
先ず、本発明アルミニウム合金板の化学成分組成について、各元素の限定理由を含めて、以下に説明する。なお、各元素の含有量の%表示は全て質量%の意味である。
Aluminum alloy composition:
First, the chemical component composition of the aluminum alloy sheet of the present invention will be described below, including reasons for limiting each element. In addition,% display of content of each element means the mass% altogether.
本発明アルミニウム合金板の化学成分組成は、Al−Zn−Mg−Cu系の7000系アルミニウム合金として、自動車構造部材に要求される、伸びフランジ性、強度、耐SCC性などの諸特性を保証するために決定される。この観点から、本発明アルミニウム合金板の化学成分組成は、質量%で、Zn:3.0〜6.0%、Mg:1.5〜4.5%、Cu:0.05〜0.5%を各々含有し、残部がAl及び不可避的不純物からなるものとする。この組成に、更に、質量%で、Zr:0.02〜0.3%、Mn:0.05〜1.5%、Cr:0.05〜0.3%、Sc:0.02〜0.3%の1種又は2種以上を含んでも良い。これに加えて、あるいはこれとは別に、質量%で、Ag:0.01〜0.2%、Sn:0.001〜0.1%の1種又は2種を選択的に含んでも良い。また、これらに加えて、あるいはこれらとは別に、Ti:0.001〜0.1%を含んでも良い。   The chemical composition of the aluminum alloy plate of the present invention guarantees various characteristics such as stretch flangeability, strength, and SCC resistance required for automobile structural members as an Al—Zn—Mg—Cu based 7000 series aluminum alloy. To be determined. From this viewpoint, the chemical composition of the aluminum alloy sheet of the present invention is, in mass%, Zn: 3.0 to 6.0%, Mg: 1.5 to 4.5%, Cu: 0.05 to 0.5. %, And the balance consists of Al and inevitable impurities. In addition to this composition, by mass%, Zr: 0.02-0.3%, Mn: 0.05-1.5%, Cr: 0.05-0.3%, Sc: 0.02-0 .3% of 1 type or 2 types or more may be included. In addition to this, or alternatively, one or two of Ag: 0.01 to 0.2% and Sn: 0.001 to 0.1% may be selectively included in mass%. Further, in addition to or separately from these, Ti: 0.001 to 0.1% may be included.
Zn:3.0〜6.0%
必須の合金元素であるZnは、Mgとともに、溶体化処理後の室温時効時にクラスタ(微細析出物)を形成して加工硬化特性を向上させる。また、人工時効処理時に時効析出物を形成して強度を向上させる。Zn含有量が3.0%未満では強度が不足し、また集合組織を規定通りに制御できず、強度と成形性とのバランスが低下する可能性もある。一方Znが6.0%を超えると粒界析出物MgZnが増えて粒界腐食が起こりやすくなり、耐食性が劣化する。従って、Zn含有量は3.0〜6.0%の範囲、好ましくは4.0〜5.5%の範囲とする。
Zn: 3.0-6.0%
Zn, which is an essential alloy element, together with Mg, forms clusters (fine precipitates) during room temperature aging after solution treatment and improves work hardening characteristics. Moreover, an aging precipitate is formed during the artificial aging treatment to improve the strength. If the Zn content is less than 3.0%, the strength is insufficient, the texture cannot be controlled as prescribed, and the balance between strength and formability may be reduced. On the other hand, if Zn exceeds 6.0%, the grain boundary precipitate MgZn 2 increases and intergranular corrosion tends to occur, and the corrosion resistance deteriorates. Therefore, the Zn content is in the range of 3.0 to 6.0%, preferably in the range of 4.0 to 5.5%.
Mg:1.5〜4.5%
必須の合金元素であるMgは、Znとともに、溶体化処理後の室温時効時にクラスタ(微細析出物)を形成して加工硬化特性を向上させる。また、人工時効処理時に時効析出物を形成して強度を向上させる。Mg含有量が1.5%未満では強度が不足し、4.5%を超えると、鋳造割れが発生し、また板の圧延性が低下し、板の製造試作が困難になる。従って、Mg含有量は1.5〜4.5%、好ましくは2.0〜4.0%の範囲とする。
Mg: 1.5-4.5%
Mg, which is an essential alloy element, together with Zn, forms clusters (fine precipitates) during room temperature aging after solution treatment, thereby improving work hardening characteristics. Moreover, an aging precipitate is formed during the artificial aging treatment to improve the strength. If the Mg content is less than 1.5%, the strength is insufficient. If the Mg content exceeds 4.5%, casting cracks occur, the rolling property of the plate is lowered, and it becomes difficult to manufacture the plate. Therefore, the Mg content is 1.5 to 4.5%, preferably 2.0 to 4.0%.
Cu:0.05〜0.5%
CuはAl−Zn−Mg系合金の耐SCC性を向上させる作用がある。さらに強度向上効果もある。Cu含有量が0.05%未満では、耐SCC性向上効果が小さい。また、強度も低下する。一方、Cu含有量が0.5%を超えると、集合組織を規定通りに制御できず、伸びフランジ性など構造部材への成形性を却って低下させる。また、圧延性及び溶接性等の諸特性も低下させる。従って、Cu含有量は0.05〜0.5%、好ましくは0.05〜0.4%とする。
Cu: 0.05 to 0.5%
Cu has the effect of improving the SCC resistance of the Al—Zn—Mg alloy. Furthermore, there is an effect of improving strength. When the Cu content is less than 0.05%, the effect of improving the SCC resistance is small. In addition, the strength decreases. On the other hand, if the Cu content exceeds 0.5%, the texture cannot be controlled as specified, and the formability of the structural member such as stretch flangeability is reduced. In addition, various properties such as rollability and weldability are also reduced. Therefore, the Cu content is 0.05 to 0.5%, preferably 0.05 to 0.4%.
Zr:0.02〜0.3%、Mn:0.05〜1.5%、Cr:0.05〜0.3%、Sc:0.02〜0.3%の1種又は2種以上
Zr、Mn、Cr及びScは、鋳塊及び最終製品板の結晶粒を微細化して強度向上に寄与する。これらの元素をいずれか1種又は2種以上含有する場合、各々その下限未満では、含有量が不足して、強度向上効果が発揮できない。一方、これらの元素の含有量がそれぞれの上限を超えた場合には、粗大晶出物を形成するため伸びが低下する。従って、Zr:0.02〜0.3%、Mn:0.05〜1.5%、Cr:0.05〜0.3%、Sc:0.02〜0.3%の各範囲とする。
One or more of Zr: 0.02-0.3%, Mn: 0.05-1.5%, Cr: 0.05-0.3%, Sc: 0.02-0.3% Zr, Mn, Cr and Sc contribute to strength improvement by refining the crystal grains of the ingot and the final product plate. When any one or two or more of these elements are contained, if less than the lower limit of each, the content is insufficient and the effect of improving the strength cannot be exhibited. On the other hand, when the content of these elements exceeds the respective upper limit, a coarse crystallized product is formed, resulting in a decrease in elongation. Therefore, Zr: 0.02 to 0.3%, Mn: 0.05 to 1.5%, Cr: 0.05 to 0.3%, Sc: 0.02 to 0.3%, respectively. .
Ag:0.01〜0.2%、Sn:0.001〜0.1%の1種又は2種
Ag及びSnは、構造材への成形加工後の人工時効処理によって強度向上に寄与する時効析出物を緊密微細に析出させ、高強度化を促進する効果があるので、必要に応じて選択的に含有させる。これらをいずれか一方又は両方含有する場合、Sn含有量が0.001%未満、Ag含有量が0.01%未満では、強度向上効果が小さい。一方、SnやAg含有量が多すぎると、圧延性及び溶接性などの諸特性を却って低下させる。また、強度向上効果も飽和し、Agに関しては高価となるだけである。従って、Ag:0.01〜0.2%、Sn:0.001〜0.1%の範囲とする。
One or two types of Ag: 0.01 to 0.2%, Sn: 0.001 to 0.1% Ag and Sn are aging that contributes to strength improvement by artificial aging treatment after molding processing to a structural material Precipitates are closely and finely precipitated, and have the effect of promoting high strength, so they are selectively contained as required. When one or both of these are contained, if the Sn content is less than 0.001% and the Ag content is less than 0.01%, the strength improvement effect is small. On the other hand, when there is too much Sn and Ag content, various characteristics, such as rolling property and weldability, will be reduced. In addition, the strength improvement effect is saturated, and Ag is only expensive. Therefore, Ag: 0.01 to 0.2% and Sn: 0.001 to 0.1% are set.
Ti:0.001〜0.1%
Tiは、Bとともに、圧延板としては不純物であるが、アルミニウム合金鋳塊の結晶粒を微細化する効果があるので、7000系合金としてJIS規格で規定する範囲での各々の含有を許容する。Tiが0.001%未満では結晶粒微細化効果が得られない。一方、Tiが0.1%を超える場合、粗大な化合物を形成し、機械的特性が劣化する。従って、Tiの上限は0.1%、好ましくは0.05%以下とする。また、このTiとともに、Bを0.03%まで含有することを許容する。Bが0.03%を超える場合、粗大な化合物を形成し、機械的特性が劣化する。
Ti: 0.001 to 0.1%
Ti, together with B, is an impurity in the rolled plate, but has the effect of refining the crystal grains of the aluminum alloy ingot, so that it is allowed to be contained as a 7000 series alloy within the range specified by the JIS standard. If Ti is less than 0.001%, the effect of crystal grain refinement cannot be obtained. On the other hand, when Ti exceeds 0.1%, a coarse compound is formed and the mechanical properties are deteriorated. Therefore, the upper limit of Ti is 0.1%, preferably 0.05% or less. Further, it is allowed to contain up to 0.03% of B together with this Ti. When B exceeds 0.03%, a coarse compound is formed and the mechanical properties deteriorate.
その他の元素:
これら記載した以外のその他の元素は不可避的な不純物である。溶解原料として、純アルミニウム地金以外に、アルミニウム合金スクラップの使用による、これら不純物元素の混入なども想定(許容)して、7000系合金のJIS規格で規定する範囲での各々の含有を許容する。また、Fe:0.5%以下、Si:0.5%以下であれば、本発明に係るアルミニウム合金板の特性に影響せず、含有が許容される。
Other elements:
Other elements other than those described are inevitable impurities. As a melting raw material, in addition to pure aluminum ingots, the inclusion of these impurity elements due to the use of aluminum alloy scrap is assumed (allowed), and each content within the range specified by the JIS standard of 7000 series alloys is allowed. . Further, if Fe: 0.5% or less and Si: 0.5% or less, the inclusion is allowed without affecting the characteristics of the aluminum alloy sheet according to the present invention.
組織:
本発明の7000系アルミニウム合金板は、前提として、その組成と多くの製造工程とが、従来の7000系アルミニウム合金板や、その製造方法(通常の圧延法)と共通する。このため、板組織として、微細なナノレベルのサイズの析出物が、結晶粒内に多数存在して、強度や耐食性などの基本特性を満たす土台となっている点も共通している。これらの微細なナノレベルのサイズの析出物とは、結晶粒内に生成する、前記MgとZnとの金属間化合物(組成はMgZnなど)であり、これに前記組成に応じて更にCu、Zrなどの含有元素が含まれる微細分散相である。
Organization:
As a premise, the 7000 series aluminum alloy plate of the present invention has the same composition and many production steps as the conventional 7000 series aluminum alloy plate and its production method (normal rolling method). For this reason, as the plate structure, a large number of fine nano-sized precipitates are present in the crystal grains, which is the basis for satisfying basic characteristics such as strength and corrosion resistance. These fine nano-level size precipitates are the intermetallic compounds of Mg and Zn (composition is MgZn 2 and the like) that are generated in the crystal grains, and depending on the composition, Cu, It is a finely dispersed phase containing a contained element such as Zr.
集合組織:
その上で、本発明の7000系アルミニウム合金板組織は、更なる高強度化や耐食性などの特性の向上のために、平均結晶粒径を50μm以下とした等軸で微細な再結晶組織とする。
Texture:
In addition, the 7000 series aluminum alloy sheet structure of the present invention has an equiaxed and finely recrystallized structure with an average crystal grain size of 50 μm or less in order to further improve the properties such as higher strength and corrosion resistance. .
Cube方位、CR方位:
そして、更に、これらの結晶粒のうち、先ず、Cube方位を有する結晶粒とCR方位を有する結晶粒とを、一定量以上存在させるとともに、互いの量的な割合も特定の範囲とする。そして、これによって、強度と成形性のバランスを向上させ、伸びフランジ性を向上させる。すなわち、Cube方位を有する結晶粒の面積率[Cube]とCR方位を有する結晶粒の面積率[CR]との合計が10%以上である、[Cube]+[CR]≧10%の関係を満足する集合組織を有するようにする。また、更に、[Cube]と[CR]との割合(比)が一定の範囲である、0.33≦[Cube]/[CR]≦3.0の関係も満足する集合組織を有するようにする。
Cube orientation, CR orientation:
Further, among these crystal grains, first, crystal grains having a Cube orientation and crystal grains having a CR orientation are present in a certain amount or more, and their quantitative ratio is also set to a specific range. And thereby, the balance between strength and formability is improved, and stretch flangeability is improved. That is, the sum of the area ratio [Cube] of crystal grains having a Cube orientation and the area ratio [CR] of crystal grains having a CR orientation is 10% or more, and the relationship of [Cube] + [CR] ≧ 10% Have a satisfactory texture. Furthermore, the texture (ratio) of [Cube] and [CR] is in a certain range, and has a texture that also satisfies the relationship of 0.33 ≦ [Cube] / [CR] ≦ 3.0. To do.
これらCube方位を有する結晶粒とCR方位を有する結晶粒とが上記規定を両方満足しなければ、強度と成形性のバランスが崩れて、伸びフランジ性を向上させることができない。また、これらCube方位を有する結晶粒とCR方位を有する結晶粒とが上記規定を両方満足しなければ、Brass方位、S方位、Cu方位、Goss方位 、Rotated−Goss方位、S方位、B/G方位、B/S方位、P方位などの他の方位を存在させても、強度と成形性のバランスは向上せず、伸びフランジ性を向上させることができない。   If the crystal grains having the Cube orientation and the crystal grains having the CR orientation do not satisfy both of the above rules, the balance between strength and formability is lost, and the stretch flangeability cannot be improved. Further, if the crystal grains having the Cube orientation and the crystal grains having the CR orientation do not satisfy both of the above specifications, the Brass orientation, S orientation, Cu orientation, Goss orientation, Rotated-Goss orientation, S orientation, B / G Even if other orientations such as an orientation, a B / S orientation, and a P orientation are present, the balance between strength and formability is not improved, and stretch flangeability cannot be improved.
Cube方位を有する結晶粒とCR方位を有する結晶粒とを一定量以上存在させた集合組織とすることによって、常法によって製造された7000系アルミニウム合金板であっても、板に歪が入った場合に、局所的に歪が集中せずに、均一に変形する組織とできる。これによって、0.2%耐力が350MPa以上であるような高強度とし、このような高強度であっても、延性や伸びがバランスした、伸びフランジ性の高い特性を得られる。   Even if it is a 7000 series aluminum alloy plate manufactured by a conventional method, the plate is distorted by forming a texture in which a certain amount or more of crystal grains having a Cube orientation and crystal grains having a CR orientation exist. In some cases, the tissue can be uniformly deformed without locally concentrating strain. As a result, a high strength such that the 0.2% proof stress is 350 MPa or more can be obtained, and even with such a high strength, it is possible to obtain high stretch flangeability characteristics in which ductility and elongation are balanced.
このような集合組織は、前記常法によって製造されて溶体化処理された後の7000系アルミニウム合金板の等軸な微細再結晶組織である。[Cube]+[CR]の上限は、製造限界からすると、40%程度である。この点で、[Cube]+[CR]の好ましい範囲は10%以上、40%以下の範囲となる。   Such a texture is an equiaxed fine recrystallized structure of a 7000 series aluminum alloy plate after being manufactured by the conventional method and subjected to a solution treatment. The upper limit of [Cube] + [CR] is about 40% from the manufacturing limit. In this respect, the preferable range of [Cube] + [CR] is in the range of 10% to 40%.
Brass方位、S方位、Cu方位:
伸びフランジ性を向上させるためには、前記[Cube]と[CR]とを規定する一方で、溶体化処理時に起こる再結晶での圧延集合組織の残存量を低下させる必要がある。その目安として、Brass方位を有する結晶粒、S方位を有する結晶粒、Cu方位を有する結晶粒を極力少なくする。圧延集合組織の残存量が多くなり、Brass方位を有する結晶粒、S方位を有する結晶粒、Cu方位を有する結晶粒が各々多くなった場合には、強度と成形性のバランスが崩れて、伸びフランジ性を向上させることができなくなる。
Brass orientation, S orientation, Cu orientation:
In order to improve stretch flangeability, it is necessary to reduce the residual amount of rolling texture in recrystallization that occurs during solution treatment while defining the above [Cube] and [CR]. As a guide, crystal grains having the Brass orientation, crystal grains having the S orientation, and crystal grains having the Cu orientation are minimized. When the remaining amount of the rolling texture increases and the number of crystal grains having the Brass orientation, the crystal grains having the S orientation, and the crystal grains having the Cu orientation increase, the balance between strength and formability is lost, and elongation occurs. Flangeability cannot be improved.
すなわち、Brass方位を有する結晶粒の面積率[Brass]と、S方位を有する結晶粒の面積率[S]と、Cu位を有する結晶粒の面積率[Cu]との合計が30%未満となる、[Brass]+[S]+[Cu]<30%の関係を満足させるようにする。但し、製造限界から、[Brass]+[S]+[Cu]を0%として、Brass方位を有する結晶粒、S方位を有する結晶粒、Cu方位を有する結晶粒を無くすことはできない。したがって、[Brass]+[S]+[Cu]が30%未満である上記式は、[Brass]+[S]+[Cu]が0%の場合を含まない。   That is, the sum of the area ratio [Brass] of the crystal grains having the Brass orientation, the area ratio [S] of the crystal grains having the S orientation, and the area ratio [Cu] of the crystal grains having the Cu position is less than 30%. The relation of [Brass] + [S] + [Cu] <30% is satisfied. However, from the manufacturing limit, it is not possible to eliminate [Brass] + [S] + [Cu] at 0%, so that crystal grains having the Brass orientation, crystal grains having the S orientation, and crystal grains having the Cu orientation cannot be eliminated. Therefore, the above formula in which [Brass] + [S] + [Cu] is less than 30% does not include the case where [Brass] + [S] + [Cu] is 0%.
集合組織の測定:
これら本発明で規定する平均結晶粒径や、各方位を有する結晶粒の面積率は、いずれもEBSP法によって測定する。より具体的に、溶体化処理後の冷延板(T4材)の幅方向断面を機械研磨し、更に、バフ研磨に次いで電解研磨して、表面を調製した試料を用意し、SEMあるいはFESEMを用いて、EBSPによる結晶方位測定並びに結晶粒径測定を行う。EBSP測定・解析システムは、EBSP:TSL社製(OIM)あるいはOXFORD社製(CHANNEL5)を用いる。板の組織の測定部位は、通常のこの種組織の測定部位と同じく、この板の幅方向断面として、この板の幅方向断面の任意の箇所から採取した5個の測定試験片(5箇所の測定箇所)の各測定値を平均化したものを、本発明で規定する平均結晶粒径や各方位を有する結晶粒の面積率とする。
Texture measurement:
The average crystal grain size and the area ratio of crystal grains having each orientation defined in the present invention are all measured by the EBSP method. More specifically, the cross-section in the width direction of the cold-rolled sheet (T4 material) after the solution treatment is mechanically polished, and further subjected to electrolytic polishing after buff polishing to prepare a sample whose surface is prepared, and SEM or FESEM is prepared. The crystal orientation measurement and the crystal grain size measurement by EBSP are performed. The EBSP measurement / analysis system uses EBSP: manufactured by TSL (OIM) or OXFORD (CHANNEL5). The measurement site | part of the structure | tissue of a board is five measurement test pieces (5 place | parts) extract | collected from the arbitrary places of the width direction cross section of this board as a width direction cross section of this board similarly to the measurement site | part of this normal structure | tissue. A value obtained by averaging each measured value of the measurement location) is defined as an average crystal grain size defined in the present invention and an area ratio of crystal grains having each orientation.
前記SEM/EBSP法は、集合組織の測定方法として汎用され、走査型電子顕微鏡(Scanning Electron Microscope:SEM)あるいは電界放出型走査電子顕微鏡(Field Emission Scanning Electron Microscope:FESEM)に、後方散乱電子回折像[EBSP: Electron Back Scattering (Scattered) Pattern] システムを搭載した結晶方位解析法である。この測定方法は、他の集合組織の測定方法に比して、高分解能ゆえに高測定精度である。そして、この方法によって、板の同じ測定部位の平均結晶粒径も同時に高精度に測定できる利点がある。アルミニウム合金板の集合組織や平均結晶粒径の測定をEBSP法により行うこと自体は、従来から、例えば特開2008−45192号、特許4499369号、特開2009−7617号、あるいは前記特許文献1、2、3などの公報で公知であり、本発明でもこの公知の方法で行う。   The SEM / EBSP method is widely used as a texture measurement method, and is applied to a scanning electron microscope (SEM) or a field emission scanning electron microscope (FESEM). [EBSP: Electron Back Scattering (Scattered) Pattern] This is a crystal orientation analysis method equipped with a system. This measurement method has high measurement accuracy because of its high resolution as compared with other texture measurement methods. This method has the advantage that the average crystal grain size at the same measurement site on the plate can be measured simultaneously with high accuracy. The measurement itself of the texture and average crystal grain size of an aluminum alloy plate by the EBSP method has been conventionally performed, for example, in Japanese Patent Application Laid-Open No. 2008-45192, Japanese Patent No. 4499369, Japanese Patent Application Laid-Open No. 2009-7617, or the above-mentioned Patent Document 1, It is known in publications such as 2, 3 and the like, and in the present invention, this known method is used.
これら開示されたEBSP法は、前記SEMあるいはFESEM(FE−SEM)の鏡筒内にセットしたAl合金板の試料に、電子線を照射してスクリーン上にEBSPを投影する。これを高感度カメラで撮影して、コンピュータに画像として取り込む。コンピュータでは、この画像を解析して、既知の結晶系を用いたシミュレーションによるパターンとの比較によって、結晶の方位が決定される。算出された結晶の各方位は3次元オイラー角として、位置座標(x、y)などとともに記録される。このプロセスが全測定点に対して自動的に行なわれるので、測定終了時には数万〜数十万点の結晶方位データが得られる。   In these disclosed EBSP methods, an EBSP is projected on a screen by irradiating an electron beam onto a sample of an Al alloy plate set in a lens barrel of the SEM or FESEM (FE-SEM). This is taken with a high-sensitivity camera and captured as an image on a computer. In the computer, the orientation of the crystal is determined by analyzing this image and comparing it with a pattern obtained by simulation using a known crystal system. Each calculated orientation of the crystal is recorded as a three-dimensional Euler angle together with position coordinates (x, y) and the like. Since this process is automatically performed for all measurement points, tens of thousands to hundreds of thousands of crystal orientation data can be obtained at the end of measurement.
このように、SEM/EBSP法には、透過電子顕微鏡を用いた電子線回折法よりも、観察視野が広く、数百個以上の多数の結晶粒に対する、平均結晶粒径、平均結晶粒径の標準偏差、あるいは方位解析の情報を、数時間以内で得られる利点がある。また、結晶粒毎の測定ではなく、指定した領域を任意の一定間隔で走査して測定するために、測定領域全体を網羅した上記多数の測定ポイントに関する、上記各情報を得ることができる利点もある。これらSEMあるいはFESEMにEBSPシステムを搭載した結晶方位解析法の詳細は、神戸製鋼技報/Vol.52 No.2(Sep.2002)P66-70などに詳細に記載されている。   Thus, the SEM / EBSP method has a wider field of view than the electron diffraction method using a transmission electron microscope, and has an average crystal grain size and an average crystal grain size of hundreds of crystal grains. There is an advantage that information on standard deviation or orientation analysis can be obtained within a few hours. In addition, since the measurement is performed by scanning a specified region at an arbitrary fixed interval instead of measurement for each crystal grain, there is also an advantage that each of the above-described information on the numerous measurement points covering the entire measurement region can be obtained. is there. Details of the crystal orientation analysis method in which the EBSP system is mounted on these SEM or FESEM are described in detail in Kobe Steel Technical Report / Vol.52 No.2 (Sep.2002) P66-70 and the like.
ここで、アルミニウム合金板の場合、通常は、以下に示す多くの方位因子(これら各方位を有する結晶粒)からなる集合組織を形成し、それらに応じた結晶面が存在する。これらの事実は、例えば、長島晋一編著、「集合組織」(丸善株式会社刊)や軽金属学会「軽金属」解説Vol.43、1993、P285-293などに記載されている。   Here, in the case of an aluminum alloy plate, usually, a texture composed of many orientation factors (crystal grains having these orientations) shown below is formed, and there are crystal planes corresponding to them. These facts are described in, for example, “Cross Texture” (published by Maruzen Co., Ltd.) edited by Shinichi Nagashima, “Light Metal”, Vol. 43, 1993, P285-293, etc.
これらの集合組織の形成は同じ結晶系の場合でも加工、熱処理方法によって異なる。圧延による板材の集合組織の場合は、圧延面と圧延方向で表されており、圧延面は{ABC}で表現され、圧延方向は<DEF>で表現される(ABCDEFは整数を示す)。かかる表現に基づき、各方位は下記の如く表現される。
Cube方位 {001}<100>
Goss方位 {011}<100>
Rotated−Goss方位{011}<011>
Brass方位(B方位) {011}<211>
Cu方位(Copper方位){112}<111>
(若しくはD方位{4411}<11118>
S方位 {123}<634>
B/G方位 {011}<511>
B/S方位 {168}<211>
P方位 {011}<111>
The formation of these textures differs depending on the processing and heat treatment methods even in the case of the same crystal system. In the case of a texture of a plate material by rolling, it is expressed by a rolling surface and a rolling direction, the rolling surface is expressed by {ABC}, and the rolling direction is expressed by <DEF> (ABCDEF indicates an integer). Based on this expression, each direction is expressed as follows.
Cube orientation {001} <100>
Goss orientation {011} <100>
Rotated-Goss orientation {011} <011>
Brass orientation (B orientation) {011} <211>
Cu orientation (Copper orientation) {112} <111>
(Or D direction {4411} <11118>
S orientation {123} <634>
B / G direction {011} <511>
B / S orientation {168} <211>
P direction {011} <111>
本発明においては、基本的に、これらの結晶面から±15°未満の方位のずれ(傾角)のものは同一の結晶面(方位因子)に属するものとする。また、隣り合う結晶粒の方位差(傾角)が5°以上の結晶粒の境界を結晶粒界と定義する。   In the present invention, basically, those whose orientation deviation (tilt angle) is less than ± 15 ° from these crystal planes belongs to the same crystal plane (orientation factor). Further, the boundary between crystal grains in which the orientation difference (tilt angle) between adjacent crystal grains is 5 ° or more is defined as a crystal grain boundary.
そして、前記したSEMあるいはFESEMにEBSPシステムを搭載した結晶方位解析法を用いて、前記板の集合組織を測定して、本発明で規定した[Cube]+[CR]、[Cube]/[CR]、[Brass]+[S]+[Cu]などの算出を行なった。この際、上記記載したCube方位からP方位までの各結晶方位(全結晶方位)の合計の面積を100として、本発明で規定した各方位の面積率の算出を行なった。   Then, using the crystal orientation analysis method in which the EBSP system is mounted on the SEM or FESEM, the texture of the plate is measured, and [Cube] + [CR], [Cube] / [CR ], [Brass] + [S] + [Cu], etc. were calculated. Under the present circumstances, the area ratio of each orientation prescribed | regulated by this invention was computed by making the total area of each crystal orientation (all crystal orientations) from the above-mentioned Cube orientation to P orientation into 100.
なお、前記平均結晶粒径も、傾角が5°以上の粒界で測定、算出する。言い換えると、本発明では、±5°未満の方位のずれは同一の結晶粒に属するものと定義し、隣り合う結晶粒の方位差(傾角)が5°以上の結晶粒の境界を結晶粒界と定義した上で、平均結晶粒径を以下の式により算出した。平均結晶粒径=(Σx)/n(ここで、nは測定した結晶粒の数、xはそれぞれの結晶粒径を示す)。   The average crystal grain size is also measured and calculated at a grain boundary having an inclination angle of 5 ° or more. In other words, in the present invention, an orientation shift of less than ± 5 ° is defined as belonging to the same crystal grain, and a boundary between crystal grains having an orientation difference (tilt angle) of 5 ° or more between adjacent crystal grains is defined as a grain boundary. And the average crystal grain size was calculated by the following formula. Average crystal grain size = (Σx) / n (where n is the number of crystal grains measured and x is the respective crystal grain size).
(製造方法)
本発明の7000系アルミニウム合金板は、鋳塊を均熱処理後に熱間圧延され、更に冷間圧延された冷延板であって、更に溶体化処理などの調質が施される、常法によって製造される。即ち、鋳造、均質化熱処理、熱間圧延の通常の各製造工程を経て製造され、板厚が2〜10mm程度であるアルミニウム合金熱延板とされる。次いで、冷間圧延されて板厚が3mm以下の冷延板とされる。したがって、双ロール法などの薄板連続鋳造後に冷延して熱延を省略したり、温間圧延を行うような特殊な製造方法や圧延方法によっては製造されない。但し、本発明の集合組織とするための均熱条件と冷間圧延条件とは、後述する通り、常法による工程とは、その条件が特に異なる。
(Production method)
The 7000 series aluminum alloy sheet of the present invention is a cold-rolled sheet obtained by subjecting an ingot to hot rolling after soaking and further cold rolling, and further subjected to tempering such as solution treatment. Manufactured. That is, an aluminum alloy hot rolled sheet having a thickness of about 2 to 10 mm is manufactured through normal manufacturing processes such as casting, homogenization heat treatment, and hot rolling. Subsequently, it is cold-rolled to obtain a cold-rolled sheet having a thickness of 3 mm or less. Therefore, it is not manufactured by a special manufacturing method or a rolling method in which hot rolling is omitted by cold rolling after thin plate continuous casting such as a twin roll method or warm rolling is performed. However, the soaking conditions and the cold rolling conditions for obtaining the texture of the present invention are particularly different from the conditions according to the conventional method, as will be described later.
(溶解、鋳造冷却速度)
先ず、溶解、鋳造工程では、上記7000系成分組成範囲内に溶解調整されたアルミニウム合金溶湯を、連続鋳造法、半連続鋳造法(DC鋳造法)等の通常の溶解鋳造法を適宜選択して鋳造する。
(Dissolution, casting cooling rate)
First, in the melting and casting process, an ordinary molten casting method such as a continuous casting method or a semi-continuous casting method (DC casting method) is appropriately selected for the aluminum alloy melt adjusted within the above-mentioned 7000-based component composition range. Cast.
(均質化熱処理)
次いで、前記鋳造されたアルミニウム合金鋳塊に、熱間圧延に先立って、均質化熱処理を施す。この均質化熱処理(均熱処理)は、組織の均質化、すなわち、鋳塊組織中の結晶粒内の偏析をなくすことを目的とする。但し、この均熱処理は集合組織の形成にも大きく影響するので、本発明で規定する集合組織とするためには、この均熱処理を、通常の1回だけの均熱ではなく、2回均熱あるいは2段均熱とする。
(Homogenization heat treatment)
Next, the cast aluminum alloy ingot is subjected to a homogenization heat treatment prior to hot rolling. The purpose of this homogenization heat treatment (soaking) is to homogenize the structure, that is, eliminate segregation in crystal grains in the ingot structure. However, this soaking process has a great influence on the formation of the texture. Therefore, in order to obtain a texture as defined in the present invention, this soaking process is carried out twice soaking instead of the usual one soaking. Or it shall be two-stage soaking.
2回均熱とは、1回目の均熱後に、一旦室温を含む200℃以下の温度まで冷却し、更に、再加熱し、その温度で一定時間維持した後に、熱延を開始する。これに対して、2段均熱とは、1回目の均熱後に冷却はするものの、200℃以下までは冷却せず、より高温で冷却を停止した上で、その温度で維持した後に、そのままの温度か、より高温に再加熱した上で熱延を開始する。   In the second soaking, after the first soaking, the steel sheet is once cooled to a temperature of 200 ° C. or less including room temperature, reheated, and maintained at that temperature for a certain time, and then hot rolling is started. On the other hand, the two-stage soaking means cooling after the first soaking, but it is not cooled to 200 ° C. or lower, and after stopping the cooling at a higher temperature, the temperature is maintained as it is. The hot rolling is started after reheating to a higher temperature.
1回目の均熱条件は、400℃以上、融点未満の温度範囲で、2時間以上の均質化時間の範囲から適宜選択される。   The first soaking condition is appropriately selected from a range of homogenization time of 2 hours or more in a temperature range of 400 ° C. or higher and lower than the melting point.
この1回目の均熱処理後に、2回均熱のために、一旦、室温を含む200℃以下まで冷却するか(2回均熱)、2段均熱のために、一旦、200℃よりも高温の温度まで冷却する(2段均熱)。この際の冷却速度は、2回均熱あるいは2段均熱とも共通して、30℃/hr以下、好ましくは10℃/hr以下の緩冷却とする。   After this first soaking process, it is once cooled to 200 ° C. or less including room temperature for soaking twice (twice soaking), and once higher than 200 ° C. for two-stage soaking. (2 stage soaking). The cooling rate at this time is a slow cooling of 30 ° C./hr or less, preferably 10 ° C./hr or less, in common with the two-step soaking or the two-stage soaking.
このように冷却速度を低下させることで、冷却中に分散粒子の析出量を増大させて、それによって冷延時の圧延集合組織の発達を弱める。これによって、冷延後の溶体化処理時に起こる再結晶での圧延集合組織の残存量を低下させ、[Brass]、[S]、[Cu]を減らすことができる。   By reducing the cooling rate in this way, the amount of dispersed particles precipitated during cooling is increased, thereby weakening the development of the rolling texture during cold rolling. As a result, the remaining amount of the rolling texture in recrystallization that occurs during the solution treatment after cold rolling can be reduced, and [Brass], [S], and [Cu] can be reduced.
また、この冷却速度を低下させることで、冷延後の溶体化処理時に起こる再結晶後のCR方位、[CR]を発達させることができる。同時に、この冷却速度を低下させることで、前記した分散粒子の析出量を増大させ、マトリックスへの元素の固溶量を低下させることで、溶体化処理時に起こる再結晶後のCube方位、[Cube]を適度に発達させることができる。   Further, by reducing the cooling rate, the CR orientation [CR] after recrystallization that occurs during the solution treatment after cold rolling can be developed. At the same time, by reducing the cooling rate, the amount of precipitation of the dispersed particles described above is increased, and the solid solution amount of the element in the matrix is reduced, so that the Cube orientation after recrystallization that occurs during the solution treatment, [Cube ] Can be developed moderately.
このような2回均熱あるいは2段均熱における、1回目の均熱処理後の冷却条件によって、後述する冷間圧延条件と合わせて、本発明で規定する集合組織として、[Cube]+[CR]≧10%、0.33≦[Cube]/[CR]≦3.0、[Brass]+[S]+[Cu]<30%を満足させることができる。この冷却条件から外れるか、通常の1回の均熱処理では、後述する冷間圧延条件が好ましい範囲内で行われたとしてもて、本発明で規定する集合組織が得られず、[Cube]+[CR]が10%未満か、0.33≦[Cube]/[CR]≦3.0とならない可能性が高くなる。また、冷延時の圧延集合組織が発達しすぎて、冷延後の溶体化処理時に起こる再結晶での圧延集合組織の残存量が過大となって、[Brass]、[S]、[Cu]を減らすことができず、[Brass]+[S]+[Cu]が30%以上となる可能性が高くなる。   Depending on the cooling conditions after the first soaking in such two-stage soaking or two-stage soaking, together with the cold rolling conditions described later, the texture defined in the present invention is [Cube] + [CR ] ≧ 10%, 0.33 ≦ [Cube] / [CR] ≦ 3.0, and [Brass] + [S] + [Cu] <30% can be satisfied. In this normal soaking process, the texture specified in the present invention cannot be obtained even if the cold rolling conditions described later are performed within a preferable range, and [Cube] + There is a high possibility that [CR] is less than 10% or 0.33 ≦ [Cube] / [CR] ≦ 3.0. Further, the rolling texture at the time of cold rolling develops too much, and the residual amount of the rolling texture at the recrystallization that occurs during the solution treatment after cold rolling becomes excessive, and [Brass], [S], [Cu] Cannot be reduced, and there is a high possibility that [Brass] + [S] + [Cu] will be 30% or more.
2回目あるいは2段目の均熱温度は、熱延開始温度以上、500℃以下の温度範囲で2時間以上の均質化時間の範囲から、前記1回目よりも低温の温度まで再加熱し、熱延開始温度まで冷却するか、あるいは熱延開始温度やその近傍で保持すれば良い。   The soaking temperature in the second or second stage is reheated from a range of homogenization time of 2 hours or more in the temperature range from the hot rolling start temperature to 500 ° C. to a temperature lower than the first time. What is necessary is just to cool to a rolling start temperature, or just hold | maintain at the hot rolling start temperature or its vicinity.
(熱間圧延)
熱間圧延は、熱延開始温度が固相線温度を超える条件では、バーニングが起こるため熱延自体が困難となる。また、熱延開始温度が350℃未満では熱延時の荷重が高くなりすぎ、熱延自体が困難となる。したがって、熱延開始温度は350℃〜固相線温度の範囲から選択して熱間圧延し、2〜10mm程度の板厚の熱延板とする。この熱延板の冷間圧延前の焼鈍 (荒鈍) は必ずしも必要ではないが実施しても良い。
(Hot rolling)
In the hot rolling, the hot rolling itself becomes difficult because burning occurs under conditions where the hot rolling start temperature exceeds the solidus temperature. On the other hand, when the hot rolling start temperature is less than 350 ° C., the load during hot rolling becomes too high, and the hot rolling itself becomes difficult. Therefore, the hot rolling start temperature is selected from the range of 350 ° C. to the solidus temperature and hot rolled to obtain a hot rolled plate having a thickness of about 2 to 10 mm. Annealing (roughening) of the hot-rolled sheet before cold rolling is not necessarily required, but may be performed.
(冷間圧延)
冷間圧延では、上記熱延板を圧延して、自動車構造部材用としては1〜5mm程度の所望の最終板厚の冷延板 (コイルも含む) に製作する。この際、本発明で規定する集合組織を形成させるために、冷延工程を複数回行い、最終の冷延工程前に必ず中間焼鈍を行う。最終の冷延工程前に中間焼鈍を行わない場合、後述する最終回の冷延工程における冷延率を30%以上とした場合には、冷延時の圧延集合組織が発達しすぎて、冷延後の溶体化処理時に起こる再結晶での圧延集合組織の残存量が過大となって、[Brass]、[S]、[Cu]を30%未満に減らすことができない。
(Cold rolling)
In cold rolling, the hot-rolled sheet is rolled into a cold-rolled sheet (including a coil) having a desired final thickness of about 1 to 5 mm for automobile structural members. Under the present circumstances, in order to form the texture prescribed | regulated by this invention, a cold rolling process is performed in multiple times, and intermediate annealing is always performed before the last cold rolling process. When intermediate annealing is not performed before the final cold rolling process, when the cold rolling rate in the final cold rolling process to be described later is 30% or more, the rolling texture at the time of cold rolling develops too much, and cold rolling is performed. The remaining amount of the rolling texture in the recrystallization that occurs at the time of the subsequent solution treatment is excessive, and [Brass], [S], and [Cu] cannot be reduced to less than 30%.
この冷延工程の回数は、熱延板の板厚と冷延板の最終板厚との関係で自由に選択され、この1回当たりの冷延工程における冷間圧延機への板(コイル)のパス回数も自由に選択される。   The number of cold rolling processes is freely selected according to the relationship between the thickness of the hot rolled sheet and the final thickness of the cold rolled sheet, and the sheet (coil) to the cold rolling mill in this cold rolling process. The number of passes can be freely selected.
但し、選択した冷延工程回数における、最終回の(最終の中間焼鈍後の)冷延工程における冷延率は、本発明で規定する集合組織として、[Cube]+[CR]≧10%、0.33≦[Cube]/[CR]≦3.0、を得るために、30%以上とする。この最終回の冷延工程における冷延率が30%未満では、それ以前の(最終の中間焼鈍前の)冷延工程における冷延率が例え30%以上の高い圧下率であったとしても、このような集合組織が得られず、[Cube]+[CR]が10%未満か、0.33≦[Cube]/[CR]≦3.0とならない。   However, the cold rolling ratio in the final cold rolling process (after the final intermediate annealing) in the selected number of cold rolling processes is [Cube] + [CR] ≧ 10% as a texture defined in the present invention, In order to obtain 0.33 ≦ [Cube] / [CR] ≦ 3.0, the content is made 30% or more. If the cold rolling rate in the final cold rolling step is less than 30%, even if the cold rolling rate in the previous cold rolling step (before the final intermediate annealing) is a high reduction rate of 30% or more, Such a texture cannot be obtained, and [Cube] + [CR] is less than 10% or 0.33 ≦ [Cube] / [CR] ≦ 3.0.
この際、1回当たりの冷延工程における冷間圧延のパス間で中間焼鈍を行っても良く、更には冷間圧延を行う前に中間焼鈍を行なっても良い。以上の中間焼鈍温度は、400〜550℃の範囲で、用いる連続炉やバッチ炉での通板条件に応じた適当な所要時間が選択される。   At this time, intermediate annealing may be performed between cold rolling passes in one cold rolling step, and further, intermediate annealing may be performed before cold rolling. The above-mentioned intermediate annealing temperature is in the range of 400 to 550 ° C., and an appropriate required time is selected according to the sheet passing conditions in the continuous furnace or batch furnace to be used.
このような冷延条件とすることで、冷延後の溶体化処理時に起こる再結晶後の、CR方位や[CR]、Cube方位や[Cube]を適度に発達させることができる。また、冷延時の圧延集合組織の発達を弱め、冷延後の溶体化処理時に起こる再結晶での圧延集合組織の残存量を低下させ、[Brass]、[S]、[Cu]を減らすことができる。すなわち、前記2回均熱あるいは2段均熱における1回目の均熱処理後の冷却条件と合わせて、本発明で規定する集合組織として、[Cube]+[CR]≧10%、0.33≦[Cube]/[CR]≦3.0、[Brass]+[S]+[Cu]<30%を満足させることができる。   By adopting such cold rolling conditions, the CR orientation, [CR], Cube orientation, and [Cube] after recrystallization that occurs during the solution treatment after cold rolling can be appropriately developed. Also, the development of the rolling texture during cold rolling is weakened, the residual amount of the rolling texture during recrystallization that occurs during the solution treatment after cold rolling is reduced, and [Brass], [S], and [Cu] are reduced. Can do. That is, together with the cooling conditions after the first soaking in the two-time soaking or the two-stage soaking, as a texture defined in the present invention, [Cube] + [CR] ≧ 10%, 0.33 ≦ [Cube] / [CR] ≦ 3.0 and [Brass] + [S] + [Cu] <30% can be satisfied.
一方、このような好ましい冷延条件から外れた場合、前記2回均熱あるいは2段均熱における1回目の均熱処理後の好ましい冷却条件としても、本発明で規定する集合組織が得られない可能性が高くなる。   On the other hand, when it deviates from such preferable cold rolling conditions, it is possible that the texture defined in the present invention cannot be obtained even as the preferable cooling conditions after the first soaking in the two-time soaking or the two-stage soaking. Increases nature.
(溶体化処理)
冷間圧延後は調質として溶体化処理を行う。この溶体化処理については、通常の連続熱処理ラインによる加熱,冷却でよく、特に限定はされない。ただ、各元素の十分な固溶量を得ることや結晶粒の微細化のためには、450〜550℃の溶体化処理温度とすることが望ましい。
(Solution treatment)
After cold rolling, solution treatment is performed as a tempering. The solution treatment is not particularly limited and may be heating and cooling using a normal continuous heat treatment line. However, in order to obtain a sufficient solid solution amount of each element or to refine crystal grains, it is desirable to set a solution treatment temperature of 450 to 550 ° C.
溶体化処理時の加熱(昇温)速度は平均で0.01℃/s以上、100℃/s以下の範囲とすることが望ましい。平均加熱速度が0.01℃/s未満と小さすぎては、粗大な結晶粒が生じて、溶体化処理後の組織を、等軸な再結晶組織として、平均結晶粒径が50μm以下であることや、[Cube]と[CR]、[Brass]と[S]と[Cu]とを規定した集合組織とすることができない。一方、溶体化処理炉の設備能力の限界から、平均加熱速度は100℃/sを超えて大きくはできない。   The heating (temperature increase) rate during the solution treatment is desirably 0.01 ° C./s or more and 100 ° C./s or less on average. When the average heating rate is too small as less than 0.01 ° C./s, coarse crystal grains are formed, and the structure after solution treatment is regarded as an equiaxed recrystallized structure, and the average crystal grain size is 50 μm or less. In addition, [Cube] and [CR], [Brass], [S] and [Cu] cannot be defined as a texture. On the other hand, the average heating rate cannot exceed 100 ° C./s due to the limit of the equipment capacity of the solution treatment furnace.
なお、溶体化処理後の平均冷却(降温)速度は特に問わないが、溶体化処理後の冷却は、ファンなどの空冷、ミスト、スプレー、浸漬等の水冷手段など、強制的な冷却手段や条件を各々選択して用いる。ちなみに、溶体化処理は基本的に1回のみであるが、室温時効硬化が進みすぎた場合などには、自動車部材への成形性の確保のため、溶体化処理を前記好ましい条件にて再度施して、この進みすぎた室温時効硬化を一旦キャンセルしても良い。   The average cooling (temperature decrease) rate after the solution treatment is not particularly limited, but the cooling after the solution treatment may be performed by forced cooling means such as air cooling such as a fan, water cooling means such as mist, spraying, and immersion. Are selected and used. Incidentally, although the solution treatment is basically only once, when the room temperature age hardening has progressed too much, the solution treatment is performed again under the above-mentioned preferable conditions in order to ensure the moldability to automobile members. Thus, the excessive room temperature age hardening may be canceled once.
そして、本発明のアルミニウム合金板は、素材として、伸びフランジ性が要求される伸びフランジ加工(バーリング加工、穴拡げ加工)などを含む、プレス成形や加工が施された上で、自動車、自転車、鉄道車両などの構造部材とされる。また、成形性の確保の点で、これら構造部材に成形や加工された後で、別途、必要に応じて、人工時効硬化処理されて高強度される。   And, the aluminum alloy plate of the present invention is subjected to press molding and processing, including stretch flange processing (burring processing, hole expansion processing) and the like, which require stretch flangeability as a material, and is applied to automobiles, bicycles, A structural member such as a railway vehicle. In addition, from the viewpoint of securing moldability, after being molded or processed into these structural members, they are separately subjected to artificial age-hardening treatment as necessary to increase the strength.
(人工時効硬化処理)
この人工時効硬化処理は、一般的な人工時効条件(T6、T7)で良く、温度や時間の条件は、所望の強度や素材の7000系アルミニウム合金板の強度、あるいは室温時効の進行程度などから自由に決定される。例示すると、1段の時効処理であれば、100〜150℃での時効処理を12〜36時間(過時効領域を含む)行う。また、2段の工程においては、1段目の熱処理温度が70〜100℃の範囲で2時間以上、2段目の熱処理温度が100〜170℃の範囲で5時間以上の範囲(過時効領域を含む)から選択する。
(Artificial age hardening treatment)
This artificial age hardening treatment may be performed under general artificial aging conditions (T6, T7), and the temperature and time conditions are based on the desired strength, the strength of the 7000 series aluminum alloy plate of the material, or the progress of aging at room temperature. It is decided freely. For example, in the case of one-stage aging treatment, aging treatment at 100 to 150 ° C. is performed for 12 to 36 hours (including an overaging region). In the two-stage process, the first-stage heat treatment temperature is in the range of 70 to 100 ° C. for 2 hours or longer, and the second-stage heat treatment temperature is in the range of 100 to 170 ° C. for five hours or longer (over-aged region). Select from).
下記表1に示す各成分組成の7000系アルミニウム合金の冷延板の集合組織を、表2のように製造条件を変えて種々変えたものについて、強度などの機械的な特性と伸びフランジ性との関係を評価した。これらの結果を下記表3に示す。   Regarding the texture of the 7000 series aluminum alloy cold-rolled sheet of each component composition shown in the following Table 1, variously changing the production conditions as shown in Table 2, mechanical properties such as strength and stretch flangeability Evaluated the relationship. These results are shown in Table 3 below.
冷延板の集合組織は、主として、表2に示すように、均熱条件と冷延条件とを変えて制御した。具体的には、各例とも共通して、下記表1に示す各成分組成の7000系アルミニウム合金溶湯をDC鋳造し、45mm厚み×220mm幅×145mm長さの鋳塊を得た。この鋳塊を表2の通り均質化熱処理後に熱間圧延を行い、7mmあるいは10mmの板厚の熱延板を製造し、この熱延板を、荒鈍(焼鈍)することなしに、冷間圧延して、共通して2mmの板厚の冷延板を得た。   The texture of the cold-rolled sheet was controlled mainly by changing the soaking condition and the cold-rolling condition as shown in Table 2. Specifically, in common with each example, a 7000 series aluminum alloy molten metal having each component composition shown in Table 1 below was DC cast to obtain an ingot of 45 mm thickness × 220 mm width × 145 mm length. The ingot is hot-rolled after homogenization heat treatment as shown in Table 2 to produce a hot-rolled sheet having a thickness of 7 mm or 10 mm, and the hot-rolled sheet is cold-rolled without being roughened (annealed). Rolled to obtain a cold-rolled sheet having a thickness of 2 mm in common.
各例での冷延の工程数は2あるいは3としたが、共通して各冷延工程1回当たりのパス回数は3とした。また、冷圧工程間の中間焼鈍は、連続焼鈍炉の場合は昇温は200℃/min、冷却はファン空冷で行い、バッチ焼鈍炉の場合は昇降温は40℃/hrで行った。   Although the number of cold rolling processes in each example was 2 or 3, the number of passes per cold rolling process was 3 in common. Further, the intermediate annealing between the cold-pressure processes was performed at a temperature increase of 200 ° C./min in the case of a continuous annealing furnace, cooling was performed by fan air cooling, and the temperature increase / decrease was performed at 40 ° C./hr in the case of a batch annealing furnace.
表2のうち、発明例1、3、5、比較例13、16が連続焼鈍で、他は全てバッチ焼鈍である。また、表2の発明例のうち、冷延工程を3工程とした発明例7、8、9、11は、共通して、冷延1工程目で10mmの熱延板を板厚5mmまで冷延し、表3に記載した3工程目(最終冷延工程)の各冷延率となるように、冷延2工程目の冷延率を設定した。
冷延工程を2工程とした他の発明例や比較例では、共通して、表3に記載した2工程目(最終冷延工程)の各冷延率となるように、冷延1工程目の冷延率を設定した。
In Table 2, Invention Examples 1, 3, 5 and Comparative Examples 13 and 16 are continuous annealing, and all others are batch annealing. In addition, among Invention Examples in Table 2, Invention Examples 7, 8, 9, and 11 in which the cold rolling process is performed in three steps are commonly used to cool a 10 mm hot-rolled sheet to a thickness of 5 mm in the first cold rolling process. Then, the cold rolling rate of the second cold rolling step was set so that the respective cold rolling rates of the third step (final cold rolling step) described in Table 3 were obtained.
In other invention examples and comparative examples in which the cold rolling process is performed in two steps, the first cold rolling process is performed so that the respective cold rolling rates in the second process (final cold rolling process) described in Table 3 are common. The cold rolling rate was set.
これらの冷延板を、各例とも共通して490℃×1分の溶体化処理を行い、強制空冷して室温まで冷却しT4材を得た。このT4材を室温で1週間時効させた後に、供試材を採取して、0.2%耐力を測定し、伸びフランジ性を評価するためのバーリング試験を行った。また、集合組織を調査した。これらの結果を各々表3に示す。   These cold-rolled plates were subjected to a solution treatment at 490 ° C. for 1 minute in common with each example, forced air cooled to room temperature, and a T4 material was obtained. After this T4 material was aged at room temperature for 1 week, a test material was collected, 0.2% proof stress was measured, and a burring test for evaluating stretch flangeability was performed. The texture was also investigated. These results are shown in Table 3, respectively.
伸びフランジ性:
前記T4材から1辺が100mmの正方形の板(サンプル)を採取して、この板中央に直径10mmの穴を機械加工で開けた上で、以下の2種類のポンチを用いてバーリング(穴広げ)試験を行った。なお、このバーリング試験前に、前記サンプルを400℃×0.1sの復元処理を施して時効硬化を一旦キャンセルした後で、この処理の4時間以内にバーリング試験を実施した。
(1)円錐ポンチ:φ33、 角度60°、ダイス:φ35、R5
(2)円筒ポンチ:φ40、 肩R5、ダイス:φ52.4、肩R6
Stretch flangeability:
A square plate (sample) with a side of 100 mm was taken from the T4 material, a hole with a diameter of 10 mm was machined in the center of the plate, and burring (hole expansion) was performed using the following two types of punches. ) Tested. Before the burring test, the sample was subjected to a restoring process of 400 ° C. × 0.1 s to cancel the age hardening once, and then the burring test was performed within 4 hours of the process.
(1) Conical punch: φ33, angle 60 °, dice: φ35, R5
(2) Cylindrical punch: φ40, shoulder R5, dice: φ52.4, shoulder R6
バーリング試験は、東京衡機製作所製500kN深絞り試験機を用い、打抜き穴の縁に破断が発生した段階でポンチを止め、破断後の穴内径(ds)と成形試験前の初期穴径(d0)から、下記式によって、円筒ポンチでのバーリング率λ(%)と、円錐ポンチでのバーリング率λ(%)を各々を求めた。
λ=(ds−d0)/d0×100
For the burring test, a 500 kN deep drawing tester manufactured by Tokyo Henki Seisakusho Co., Ltd. was used. The punch was stopped when the edge of the punched hole was broken. From the following equations, the burring rate λ (%) in the cylindrical punch and the burring rate λ (%) in the conical punch were obtained, respectively.
λ = (ds−d0) / d0 × 100
(集合組織、平均結晶粒径)
前記T4材の板状試験片の集合組織、平均結晶粒径の測定は、板の幅方向断面の組織を前記した測定方法により行った。測定は、TSL社製EBSP測定・解析システム(OIM)を搭載した、日本電子社製SEM(JEOL JSM 6500F)を用いた。各例とも、板の幅方向断面の任意の箇所から採取した試験片5個について各々行い、これらの測定値を各々平均化した。各試験片の測定領域は共通して圧延方向に平行な断面の圧延方向400μm×最表層から板厚方向100μmの領域とし、測定ステップ間隔も共通して0.4μmとした。
(Texture, average grain size)
The texture and average crystal grain size of the plate-shaped test piece of the T4 material were measured by the measurement method described above for the structure of the cross section in the width direction of the plate. For the measurement, an SEM (JEOL JSM 6500F) manufactured by JEOL Ltd. equipped with an EBSP measurement / analysis system (OIM) manufactured by TSL was used. In each example, five test pieces taken from arbitrary positions in the cross-section in the width direction of the plate were each measured, and these measured values were averaged. The measurement area of each test piece is commonly an area of 400 μm in the rolling direction of the cross section parallel to the rolling direction × 100 μm in the plate thickness direction from the outermost layer, and the measurement step interval is also 0.4 μm in common.
また、構造部材への成形加工後の人工時効硬化処理を模擬して、T6処理として、前記T4材を、90℃×3hr+140℃×8hrの2段階の共通する条件で、人工時効硬化処理を行った。こうして得られた人工時効硬化処理後のアルミニウム合金板の中央部から板状試験片を採取して、機械的特性や耐食性を以下のようにして調査した。これらの結果も各々表3に示す。   In addition, the artificial age hardening treatment after forming the structural member is simulated, and as the T6 treatment, the artificial age hardening treatment is performed on the T4 material under two common conditions of 90 ° C. × 3 hr + 140 ° C. × 8 hr. It was. A plate-like test piece was collected from the central part of the aluminum alloy plate after the artificial age hardening treatment thus obtained, and the mechanical properties and corrosion resistance were investigated as follows. These results are also shown in Table 3.
(機械的特性)
各例とも採取した板状試験片の圧延方向に対して平行方向の室温引張試験を行い、引張強度(MPa)、0.2%耐力(MPa)、全伸び(%)を測定した。室温引張り試験はJIS2241(1980)に基づき、室温20℃で試験を行った。引張り速度は5mm/分で、試験片が破断するまで一定の速度で行った。
(Mechanical properties)
In each case, a room temperature tensile test was performed in a direction parallel to the rolling direction of the plate-shaped specimens collected, and tensile strength (MPa), 0.2% proof stress (MPa), and total elongation (%) were measured. The room temperature tensile test was performed at a room temperature of 20 ° C. based on JIS2241 (1980). The tensile speed was 5 mm / min, and the test was performed at a constant speed until the test piece broke.
(微細析出物)
各例とも、参考として、前記T4材の板状試験片の表面から板厚中心である1/2t深さ部の断面を、倍率300000倍の透過型電子顕微鏡により観察し、結晶粒内の2.0〜20nmのサイズの析出物の平均数密度(個/μm)を測定した。この観察を試験片5個について行い、結晶粒内の2.0〜20nmのサイズの析出物の数密度を各々求めて、平均化(平均数密度と)したところ、各発明例ともに、2.0〜20nmのサイズの析出物の数密度は平均で2〜9×10個/μmの範囲であった。ここで、析出物のサイズは面積が等価な円の直径に換算して測定した。
(Fine precipitate)
In each example, as a reference, a cross section from the surface of the plate-shaped specimen of the T4 material to a 1 / 2t depth portion, which is the center of the plate thickness, was observed with a transmission electron microscope at a magnification of 300000 times. The average number density (pieces / μm 3 ) of precipitates having a size of 0.0 to 20 nm was measured. This observation was performed on five test pieces, and the number density of precipitates having a size of 2.0 to 20 nm in the crystal grains was obtained and averaged (average number density). The number density of precipitates having a size of 20 nm was in the range of 2 to 9 × 10 4 pieces / μm 3 on average. Here, the size of the precipitate was measured in terms of the diameter of a circle having an equivalent area.
(粒界腐食感受性)
耐食性評価として、旧JIS-W1103 の規定に準じた粒界腐食感受性試験を、前記人工時効硬化処理後の板状試験片(試験片3個)に対して行った。試験条件は、試験片を硝酸水溶液(30質量%)に室温で1分間浸漬した後、水酸化ナトリウム水溶液(5質量%)に40℃で20秒浸漬した後、硝酸水溶液(30質量%)に室温で1分間浸漬することによって試験片の表面を洗浄した。その後、塩化ナトリウム水溶液(5質量%)に浸漬した状態で、1mA/cmの電流密度の電流を24時間流した後、試料を引き上げ、その後、試験片の断面を切断・研磨し、光学顕微鏡を用いて、試料表面からの腐食深さを測定した。倍率は×100とし、腐食深さが200μm 以下までを軽微な腐食として「○」と評価した。また、200μm を超える場合を大きな腐食として「×」と評価した。
(Intergranular corrosion sensitivity)
As the corrosion resistance evaluation, an intergranular corrosion susceptibility test according to the provisions of the former JIS-W1103 was performed on the plate-like test pieces (three test pieces) after the artificial age hardening treatment. The test condition was that the test piece was immersed in an aqueous nitric acid solution (30% by mass) for 1 minute at room temperature, then immersed in an aqueous sodium hydroxide solution (5% by mass) at 40 ° C. for 20 seconds, and then immersed in an aqueous nitric acid solution (30% by mass). The surface of the test piece was cleaned by immersion for 1 minute at room temperature. Thereafter, a current having a current density of 1 mA / cm 2 was allowed to flow for 24 hours in a state immersed in an aqueous sodium chloride solution (5% by mass), and then the sample was pulled up, and then the cross section of the test piece was cut and polished. Was used to measure the depth of corrosion from the sample surface. The magnification was x100, and a corrosion depth of 200 μm or less was evaluated as “◯” as minor corrosion. Moreover, the case where it exceeded 200 micrometers was evaluated as "x" as big corrosion.
(耐SCC性)
更に、耐食性評価として、耐SCC性評価試験を、前記人工時効硬化処理後の板状試験片に対して行った。試験条件は、50mm×10mmの短冊状試験片に、3点支持法によって、試験片長手方向に負荷応力240N/mmをかけ、90〜95℃に保持したクロム酸水溶液(純水15リットルに、塩化ナトリウム30g/リットルを15リットル、無水クロム酸カリウム36g/リットルを15リットル、重クロム酸カリウム30g/リットルを15リットル加えた水溶液)に浸漬し、割れが発生するまでの時間が7時間以上を「○」、7時間未満を「×」と評価した。この耐SCC性評価試験は、前記付加応力のレベルを含めて、構造材用のアルミニウム合金押出材の耐SCC性評価試験を模擬しており、板の評価試験としては厳しい条件となっている。
(SCC resistance)
Furthermore, as a corrosion resistance evaluation, an SCC resistance evaluation test was performed on the plate-shaped test piece after the artificial age hardening treatment. The test conditions were as follows: a 50 mm × 10 mm strip test piece was subjected to a load stress of 240 N / mm 2 in the longitudinal direction of the test piece by a three-point support method and maintained at 90 to 95 ° C. (to 15 liters of pure water). Soaked in 15 liters of sodium chloride 30 liters, 15 liters of anhydrous potassium chromate 36 liters / liter and potassium dichromate 30 gram / liter 15 liters) Was evaluated as “◯” and less than 7 hours as “×”. This SCC resistance evaluation test simulates the SCC resistance evaluation test of the aluminum alloy extruded material for structural materials, including the level of the applied stress, and is a severe condition as a plate evaluation test.
表1〜3から明らかなように、各発明例は、本発明アルミニウム合金組成範囲内であり、前記した好ましい均熱処理条件と冷延条件の範囲内で製造されている。この結果、T4材の組織として、平均結晶粒径が50μm以下であるとともに、[Cube]+[CR]≧10%、0.33≦[Cube]/[CR]≦3.0、[Brass]+[S]+[Cu]<30%を満足する。   As is apparent from Tables 1 to 3, each of the inventive examples is within the composition range of the aluminum alloy of the present invention, and is manufactured within the range of the preferred soaking conditions and cold rolling conditions described above. As a result, as the structure of the T4 material, the average crystal grain size is 50 μm or less, and [Cube] + [CR] ≧ 10%, 0.33 ≦ [Cube] / [CR] ≦ 3.0, [Brass] + [S] + [Cu] <30% is satisfied.
この結果、バーリング試験における円筒ポンチでのバーリング率λが40%以上、円錐ポンチでのバーリング率λも60%以上で、伸びフランジ性に優れている。また、T6材の0.2%耐力も370MPa以上、高いものでは400MPa以上であり、耐粒界腐食性や耐SCC性などの耐食性にも優れている。ただ、Zn含有量が上限に近い表2、3の発明例4(表1の発明例4の合金組成)は、耐粒界腐食性や耐SCC性につき、今回の評価では〇であるが、Zn含有量が低い他の発明例に比して、より厳しい腐食環境下では不利となる。   As a result, the burring rate λ in the cylindrical punch in the burring test is 40% or more, and the burring rate λ in the conical punch is also 60% or more, which is excellent in stretch flangeability. Further, the 0.2% proof stress of the T6 material is 370 MPa or more, and a high one is 400 MPa or more, and is excellent in corrosion resistance such as intergranular corrosion resistance and SCC resistance. However, Invention Example 4 in Tables 2 and 3 (alloy composition of Invention Example 4 in Table 1) whose Zn content is close to the upper limit is ◯ in this evaluation for intergranular corrosion resistance and SCC resistance. Compared to other inventive examples having a low Zn content, this is disadvantageous in a more severe corrosive environment.
これに対して、各比較例は、合金組成が、表1の通り、本発明範囲から外れるか、合金組成は表1の通り本発明範囲内であるものの、前記した好ましい均熱処理条件と冷延条件の範囲からはずれて、各々製造されている。   On the other hand, in each comparative example, the alloy composition deviates from the scope of the present invention as shown in Table 1, or the alloy composition is within the scope of the present invention as shown in Table 1, but the preferred soaking conditions and cold rolling described above. Each is manufactured out of the range of conditions.
表2の比較例12は、従来の一回均熱である。このため、表1の発明例1の合金組成を用いているものの、表3の通り、T4材の集合組織が、[Cube]+[CR]が10%未満、[Cube]/[CR]が0.33未満、[Brass]+[S]+[Cu]が30%超、と規定から外れている。この結果、伸びフランジ性が劣る。   The comparative example 12 of Table 2 is the conventional one-time soaking. Therefore, although the alloy composition of Invention Example 1 in Table 1 is used, as shown in Table 3, the texture of the T4 material is [Cube] + [CR] is less than 10%, and [Cube] / [CR] is Less than 0.33, and [Brass] + [S] + [Cu] exceeds 30%. As a result, stretch flangeability is inferior.
表2の比較例13、14は、2段均熱、2回均熱だが、1回目の均熱処理後の、冷却速度が速すぎる。このため、表1の発明例1の合金組成を用いているものの、表3の通り、T4材の集合組織が、[Cube]+[CR]が10%未満、[Brass]+[S]+[Cu]が30%超、と規定から外れている。この結果、伸びフランジ性が劣る。   Comparative Examples 13 and 14 in Table 2 are two-stage soaking and two-time soaking, but the cooling rate is too high after the first soaking. Therefore, although the alloy composition of Invention Example 1 in Table 1 is used, as shown in Table 3, the texture of the T4 material is [Cube] + [CR] is less than 10%, and [Brass] + [S] + [Cu] exceeds 30%, which is out of the regulation. As a result, stretch flangeability is inferior.
表2の比較例15、16は、2回均熱、2段均熱だが、最終回の冷延工程における冷延率が10%と小さすぎる。このため、表1の発明例1の合金組成を用いているものの、表3の通り、T4材の集合組織が、[Cube]+[CR]が10%未満、[Brass]+[S]+[Cu]が30%超、と規定から外れている。この結果、伸びフランジ性が劣る。   Comparative Examples 15 and 16 in Table 2 are soaking twice and soaking in two stages, but the cold rolling rate in the final cold rolling step is too small at 10%. Therefore, although the alloy composition of Invention Example 1 in Table 1 is used, as shown in Table 3, the texture of the T4 material is [Cube] + [CR] is less than 10%, and [Brass] + [S] + [Cu] exceeds 30%, which is out of the regulation. As a result, stretch flangeability is inferior.
表2の比較例17、18は、2回均熱、2段均熱で、冷延工程を2回行っているが、この冷延工程間での、最終の冷延工程前の中間焼鈍を行っていない。このため、表1の発明例1の合金組成を用いているものの、表3の通り、T4材の集合組織が、[Cube]+[CR]が10%未満、[Brass]+[S]+[Cu]が30%超、と規定から外れている。この結果、伸びフランジ性が劣る。   Comparative Examples 17 and 18 in Table 2 are two-stage soaking and two-stage soaking, and the cold rolling process is performed twice. The intermediate annealing before the final cold rolling process between the cold rolling processes is performed. not going. Therefore, although the alloy composition of Invention Example 1 in Table 1 is used, as shown in Table 3, the texture of the T4 material is [Cube] + [CR] is less than 10%, and [Brass] + [S] + [Cu] exceeds 30%, which is out of the regulation. As a result, stretch flangeability is inferior.
表2の比較例19は、2段均熱だが、冷延工程が1回で、冷延工程前の中間焼鈍を行っていない。このため、表1の発明例1の合金組成を用いているものの、表3の通り、T4材の集合組織が、[Cube]+[CR]が10%未満、[Cube]/[CR]が0.33未満、[Brass]+[S]+[Cu]が30%超、と規定から外れている。この結果、伸びフランジ性が劣る。   Comparative Example 19 in Table 2 has two-stage soaking, but the cold rolling process is performed once, and the intermediate annealing before the cold rolling process is not performed. Therefore, although the alloy composition of Invention Example 1 in Table 1 is used, as shown in Table 3, the texture of the T4 material is [Cube] + [CR] is less than 10%, and [Cube] / [CR] is Less than 0.33, and [Brass] + [S] + [Cu] exceeds 30%. As a result, stretch flangeability is inferior.
また、表1の比較例12、13は、Zn、Mgが下限に外れ、必須元素が少なすぎる。このため、これらの合金組成を用いた表2、3の比較例20、21の通り、前記した好ましい均熱処理条件と冷延条件の範囲内で製造されているものの、T4材の集合組織が、[Cube]/[CR]が3.0超で、規定から外れ、比較例20は[Brass]+[S]+[Cu]も30%となっており、規定から外れている。このため、伸びフランジ性は優れるものの、T6材の0.2%耐力が低すぎ、強度と成形性のバランスが悪い。   In Comparative Examples 12 and 13 in Table 1, Zn and Mg are out of the lower limit, and the essential elements are too small. For this reason, as shown in Comparative Examples 20 and 21 in Tables 2 and 3 using these alloy compositions, the texture of the T4 material is manufactured within the range of the preferable soaking conditions and cold rolling conditions described above. [Cube] / [CR] is over 3.0, which is out of the specification, and in Comparative Example 20, [Brass] + [S] + [Cu] is also 30%, which is out of the specification. For this reason, although the stretch flangeability is excellent, the 0.2% proof stress of the T6 material is too low, and the balance between strength and formability is poor.
表1の比較例14はCuが下限に外れ、少なすぎる。このため、この合金組成を用いた表2、3の比較例22の通り、前記した好ましい均熱処理条件と冷延条件の範囲内で製造されているものの、T4材の集合組織が、[Cube]/[CR]が3.0超となって、規定から外れている。このため、伸びフランジ性も低く、T6材の0.2%耐力も低すぎ、耐粒界腐食性や耐SCC性などの耐食性にも劣る。   In Comparative Example 14 of Table 1, Cu is too low because Cu is out of the lower limit. For this reason, as shown in Comparative Examples 22 in Tables 2 and 3 using this alloy composition, the texture of the T4 material is [Cube] although it is manufactured within the range of the preferable soaking conditions and cold rolling conditions described above. / [CR] is over 3.0, which is not within the regulation. For this reason, stretch flangeability is also low, 0.2% proof stress of T6 material is too low, and it is inferior to corrosion resistance, such as intergranular corrosion resistance and SCC resistance.
表1の比較例15はZnが上限に外れ、多すぎる。このため、この合金組成を用いた表2、3の比較例23の通り、前記した好ましい均熱処理条件と冷延条件の範囲内で製造されており、T4材の組織として、本発明で規定する集合組織条件を満たし、強度や伸びフランジ性は優れるものの、耐粒界腐食性や耐SCC性などの耐食性が劣る。   In Comparative Example 15 of Table 1, Zn deviates from the upper limit and is too much. For this reason, as shown in Comparative Examples 23 and 2 in Tables 2 and 3 using this alloy composition, it is manufactured within the range of the preferred soaking conditions and cold rolling conditions described above, and the structure of the T4 material is specified in the present invention. Although satisfying the texture condition and excellent in strength and stretch flangeability, corrosion resistance such as intergranular corrosion resistance and SCC resistance is inferior.
表1の比較例16はMgが上限に外れ、多すぎる。このため、この合金組成を用いた表2、3の比較例24の通り、熱延で割れが発生して、板に圧延できず、集合組織の調査や特性評価もできなかった。   In Comparative Example 16 of Table 1, Mg deviates from the upper limit and is too much. For this reason, as in Comparative Example 24 in Tables 2 and 3 using this alloy composition, cracks were generated by hot rolling, and the sheet could not be rolled, and the texture and the property evaluation could not be performed.
表1の比較例17はCuが上限に外れ、多すぎる。このため、この合金組成を用いた表2、3の比較例25の通り、前記した好ましい均熱処理条件と冷延条件の範囲内で製造されているものの、T4材の集合組織も、[Brass]+[S]+[Cu]が30%超、と規定から外れている。この結果、伸びフランジ性が低すぎる。   In Comparative Example 17 in Table 1, Cu deviates from the upper limit and is too much. For this reason, as shown in Comparative Examples 25 in Tables 2 and 3 using this alloy composition, the texture of the T4 material is [Brass], although it is manufactured within the range of the preferred soaking conditions and cold rolling conditions described above. + [S] + [Cu] is more than 30%, which is out of the regulation. As a result, stretch flangeability is too low.
以上の結果から、本発明アルミニウム合金板が伸びフランジ性、高強度、そして耐食性を各々兼備するための、本発明の各要件の臨界的な意義が裏付けられる。   The above results support the critical significance of the requirements of the present invention for the aluminum alloy sheet of the present invention to have both stretch flangeability, high strength, and corrosion resistance.
以上説明したように、本発明は、常法の圧延によって製造される、伸びフランジ性に優れた7000系アルミニウム合金板を提供できる。したがって、本発明は軽量化に寄与する、伸びフランジ加工(バーリング加工、穴拡げ加工)などを含む、プレス成形や加工が施される、自動車、自転車、鉄道車両などの構造部材に好適である。   As described above, the present invention can provide a 7000 series aluminum alloy plate excellent in stretch flangeability, which is manufactured by a conventional rolling method. Therefore, the present invention is suitable for structural members such as automobiles, bicycles, and railway vehicles that are subjected to press molding and processing, including stretch flange processing (burring processing, hole expansion processing) and the like that contribute to weight reduction.

Claims (4)

  1. 質量%で、Zn:3.0〜6.0%、Mg:1.5〜4.5%、Cu:0.05〜0.5%を各々含有し、残部がAl及び不可避的不純物からなり、
    等軸な再結晶組織として、平均結晶粒径が50μm以下であるとともに、
    これらの結晶粒のうち、Cube方位を有する結晶粒の面積率[Cube]とCR方位を有する結晶粒の面積率[CR]とが、
    [Cube]+[CR]≧10%、
    0.33≦[Cube]/[CR]≦3.0の関係を各々満足するとともに、
    前記結晶粒のうち、Brass方位を有する結晶粒の面積率[Brass]と、S方位を有する結晶粒の面積率[S]と、Cu方位を有する結晶粒の面積率[Cu]とが、
    [Brass]+[S]+[Cu]<30%の関係を満足する、
    集合組織を有することを特徴とするアルミニウム合金板。
    By mass%, Zn: 3.0-6.0%, Mg: 1.5-4.5%, Cu: 0.05-0.5%, respectively, the balance is made of Al and inevitable impurities ,
    As an equiaxed recrystallized structure, the average crystal grain size is 50 μm or less,
    Among these crystal grains, the area ratio [Cube] of crystal grains having a Cube orientation and the area ratio [CR] of crystal grains having a CR orientation are:
    [Cube] + [CR] ≧ 10%,
    Each satisfies the relationship of 0.33 ≦ [Cube] / [CR] ≦ 3.0,
    Among the crystal grains, the area ratio [Brass] of the crystal grains having the Brass orientation, the area ratio [S] of the crystal grains having the S orientation, and the area ratio [Cu] of the crystal grains having the Cu orientation are:
    Satisfies the relationship of [Brass] + [S] + [Cu] <30%.
    An aluminum alloy plate characterized by having a texture.
  2. 前記アルミニウム合金板が、更に、質量%で、Zr:0.02〜0.3%、Mn:0.05〜1.5%、Cr:0.05〜0.3%、Sc:0.02〜0.3%の1種又は2種以上を含む請求項1に記載のアルミニウム合金板。   The aluminum alloy plate is further in terms of mass%, Zr: 0.02-0.3%, Mn: 0.05-1.5%, Cr: 0.05-0.3%, Sc: 0.02. The aluminum alloy plate according to claim 1, comprising one or more of ˜0.3%.
  3. 前記アルミニウム合金板が、更に、質量%で、Ag:0.01〜0.2%、Sn:0.001〜0.1%の1種又は2種を含む請求項1または2に記載のアルミニウム合金板。   The aluminum according to claim 1 or 2, wherein the aluminum alloy plate further contains one or two of Ag: 0.01 to 0.2% and Sn: 0.001 to 0.1% by mass. Alloy plate.
  4. 前記アルミニウム合金板が、更に、質量%で、Ti:0.001〜0.1%を含む請求項1乃至3のいずれか1項に記載のアルミニウム合金板。
    The aluminum alloy plate according to any one of claims 1 to 3, wherein the aluminum alloy plate further contains Ti: 0.001 to 0.1% by mass.
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