JP2012097321A - High-strength aluminum alloy forged product excellent in stress corrosion cracking resistance and forging method for the same - Google Patents

High-strength aluminum alloy forged product excellent in stress corrosion cracking resistance and forging method for the same Download PDF

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JP2012097321A
JP2012097321A JP2010245752A JP2010245752A JP2012097321A JP 2012097321 A JP2012097321 A JP 2012097321A JP 2010245752 A JP2010245752 A JP 2010245752A JP 2010245752 A JP2010245752 A JP 2010245752A JP 2012097321 A JP2012097321 A JP 2012097321A
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forged
forging
aluminum alloy
strength
corrosion cracking
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Kensuke Mori
謙介 森
Yoshikazu Suzuki
義和 鈴木
Satoshi Wakakuri
聡史 若栗
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Furukawa-Sky Aluminum Corp
古河スカイ株式会社
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Abstract

PROBLEM TO BE SOLVED: To enhance the corrosion resistance and stress corrosion cracking resistance of a high-strength aluminum alloy.SOLUTION: The high-strength aluminum alloy forged product is produced by forging an aluminum alloy containing 0.8-2.2 mass% Si (hereinafter described as %), 0.7-1.5% Cu, 0.8-1.8% Mg, 0.5-1.1% Mn, and 0.05-0.30% Zr, with the balance composed of aluminum and unavoidable impurities in such a manner that the Zener-Hollomon parameter Z falls within the range: 2.9×10≤Z≤6.6×10, wherein a fibrous structure composed of crystal grains of an aspect ratio of 10 or more occupies 80% or more of the cross-sectional area of the forged product.

Description

本発明は、耐応力腐食割れ性に優れた高強度アルミニウム合金製鍛造品と該鍛造品の製造方法に関するものである。   The present invention relates to a high-strength aluminum alloy forged product having excellent stress corrosion cracking resistance and a method for producing the forged product.
近年、自動車を始め設備等へ使用される各種部品は環境問題への配慮から、構成する素材のリサイクル性や軽量化が進められている。特に、自動車については、安全装置などの付帯設備による重量増加を軽減する目的もあり、材料の軽量化が重要な課題となっており、ボディーシートや足回り部品にアルミニウム合金が使用され始めている。   In recent years, various parts used in equipment such as automobiles have been promoted to reduce the recyclability and weight of constituent materials in consideration of environmental problems. Especially for automobiles, the purpose is to reduce the increase in weight caused by incidental facilities such as safety devices, and weight reduction of materials has become an important issue, and aluminum alloys are beginning to be used for body seats and underbody parts.
自動車などの乗り物は、特に床下重量の軽量化が燃費に効果的であることから、足回り部品にアルミニウム合金が使用されることが多くなっている。足回り部品は、強度、加工性もさることながら、腐食による強度低下が起こらないことが重要である。つまり、それら部品には優れた耐応力腐食割れ性が要求される。   In vehicles such as automobiles, aluminum alloy is frequently used for undercarriage parts because the weight reduction under the floor is particularly effective for fuel economy. It is important for the undercarriage parts that strength and workability as well as strength do not decrease due to corrosion. That is, these parts are required to have excellent stress corrosion cracking resistance.
構造部材として使用されるアルミニウム高強度材としては、2000系(Al−Cu系)、7000系(Al−Mg−Zn系)アルミニウム合金が知られるが、鍛造品として使用される場合、材料強度が強いことから、鍛造回数が多くなる。これに対し、6000系アルミニウム合金は、加工性に優れるため鍛造などの加工が施される製品向けの材料には有効な合金であるが、前記合金系と比べ、一般的に強度が低下する。6000系アルミニウム合金の高強度材料としては、6066合金が知られるが、この合金は鍛造加工により鍛造後製品の結晶粒が粗大化することがある。結晶粒界に析出物が存在すると粒界腐食を生じることがある。応力腐食試験では、腐食環境下で応力を加えることで粒界での腐食による割れの進行が顕著となる。   As aluminum high-strength materials used as structural members, 2000-series (Al-Cu-series) and 7000-series (Al-Mg-Zn-series) aluminum alloys are known. Since it is strong, the number of forgings increases. In contrast, the 6000 series aluminum alloy is excellent in workability, and is therefore an effective alloy for materials for products such as forging. However, the strength is generally lower than that of the alloy series. As a high-strength material of the 6000 series aluminum alloy, 6066 alloy is known, but the crystal grain of the product after forging may be coarsened by this forging process. When precipitates exist at the grain boundaries, intergranular corrosion may occur. In the stress corrosion test, the progress of cracks due to corrosion at the grain boundaries becomes significant by applying stress in a corrosive environment.
再結晶した製品の中で、特にCu添加合金は、析出したCuにより、腐食が進行することがあり、製品特性に悪影響を与えることが多々ある。また、腐食環境下で応力を加えることで粒界での腐食による割れの進行が顕著となる。特に、自動車足周り部品のような応力のかかる部位では、応力腐食割れによる不具合発生が懸念される。   Among the recrystallized products, in particular, Cu-added alloys may be corroded by precipitated Cu, which often adversely affects product characteristics. Further, when stress is applied in a corrosive environment, the progress of cracks due to corrosion at the grain boundaries becomes remarkable. In particular, there is concern over the occurrence of problems due to stress corrosion cracking in parts where stress is applied, such as parts around automobile foot.
高強度6000系アルミニウム合金について、特許文献1には、強度と靭性、すなわち耐力で350MPa以上の高強度とシャルピー衝撃値20J/cm以上の高靭性を得る車両構造部材用として使用される耐食性に優れたAl−Mg−Si系アルミニウム合金鍛造材について記されている。ここでは、Mg、Si、Cu量を特定の関係としMn、Zrを添加すること、鍛造材の製造方法(鍛造条件、鍛造品の熱処理条件)を規定することにより粒界腐食を防止する。 Regarding high-strength 6000 series aluminum alloys, Patent Document 1 describes strength and toughness, that is, corrosion resistance used for vehicle structural members to obtain high strength of 350 MPa or more and high toughness of Charpy impact value of 20 J / cm 2 or more. An excellent Al—Mg—Si based aluminum alloy forging is described. Here, intergranular corrosion is prevented by prescribing Mn and Zr with specific amounts of Mg, Si, and Cu, and by specifying a method for producing a forged material (forging conditions and heat treatment conditions for the forged product).
特許文献に2は、強度と靭性、すなわち耐力で400MPa以上の高強度とシャルピー衝撃値25J/cm以上の高靭性を得る車両構造部材用として使用される耐食性に優れたAl−Mg−Si系アルミニウム合金鍛造材について記されている。ここでも特許文献1と同様にMg、Si、Cu量を特定の関係としMn、Cr、Zrを添加すること、鍛造材の製造方法(鍛造条件、減面率、鍛造品の熱処理条件)を規定し、鍛造材の断面肉厚中心部の平均結晶粒径と亜結晶粒組織が占める割合を限定することにより粒界腐食を防止する。
特開平19−169699 特開平19−177308
Patent Document 2 describes Al-Mg-Si based on strength and toughness, that is, Al-Mg-Si excellent in corrosion resistance used as a vehicle structural member for obtaining a high strength of 400 MPa or more and a high toughness of Charpy impact value of 25 J / cm 2 or more. The aluminum alloy forging is described. Here, similarly to Patent Document 1, the amount of Mg, Si, and Cu is specified, and Mn, Cr, and Zr are added, and the forging production method (forging conditions, area reduction rate, heat treatment conditions for forgings) And the grain boundary corrosion is prevented by limiting the ratio of the average crystal grain size and the sub-grain structure in the central part of the cross-sectional thickness of the forged material.
JP-A-19-169699 JP 19-177308 A
高強度アルミニウム合金としては、Al−Cu系、Al−Zn−Mg系、Al−Zn−Mg−Cu系合金が知られている。しかし、強度、加工性、耐食性を考えるとAl−Mg−Si系合金はこれらの特性のバランスが優れており、鍛造などの加工品には有用な合金である。しかし、強度は決して高いものではなく、より高強度、且つ加工性、耐食製の優れた合金が望まれる。Al−Mg−Si系合金においては、Al−Mg−Si系合金にもJIS6066合金のように強度向上を目的にCu添加が行われた合金があるものの、鍛造加工後に結晶粒が粗大化してしまうことが確認されている。また、析出したCuの影響で耐食性が低下する。このことは、自動車などの乗り物の足回り構造部材として使用を考えた場合、耐食性、耐応力腐食割れ性の低下が懸念される。このことから、耐腐食性、若しくは耐応力腐食割れ性の向上が必要であった。   As high-strength aluminum alloys, Al—Cu, Al—Zn—Mg, and Al—Zn—Mg—Cu alloys are known. However, considering the strength, workability, and corrosion resistance, the Al—Mg—Si based alloy has an excellent balance of these properties, and is a useful alloy for processed products such as forging. However, the strength is never high, and an alloy having higher strength, excellent workability and corrosion resistance is desired. In Al-Mg-Si alloys, Al-Mg-Si alloys include alloys with Cu added for the purpose of improving strength, such as JIS6066 alloy, but crystal grains become coarse after forging. It has been confirmed. Moreover, corrosion resistance falls under the influence of deposited Cu. This is a concern that the corrosion resistance and stress corrosion cracking resistance may be lowered when considering use as an undercarriage structural member of a vehicle such as an automobile. Therefore, it is necessary to improve the corrosion resistance or the stress corrosion cracking resistance.
以上のように、自動車などの乗り物の足回り部材に使用される鍛造品は、強度を有し、かつ粗大な再結晶組織ではなく、繊維状組織であることが望まれる。しかし、実際の製造では再結晶組織となることが少なくない。そこで、再結晶組織を表層の最小限にとどめ素材内部を繊維状組織とすることで、応力付加時の粒界への伝播をできる限り少なくすることが望まれる。   As described above, a forged product used for an undercarriage member of a vehicle such as an automobile is desired to have a strength and a fibrous structure rather than a coarse recrystallized structure. However, in actual manufacturing, a recrystallized structure often occurs. Therefore, it is desired to minimize the propagation to the grain boundary when stress is applied by limiting the recrystallized structure to the minimum on the surface layer and forming a fibrous structure inside the material.
上記の事情に鑑み、本発明者らは鋭意検討の結果、Al−Mg−Si系合金において、成分及び製造工程を制御することにより鍛造品内部を繊維状組織とすることで、強度を向上しつつ、耐応力腐食割れ性に優れたアルミニウム合金鍛造品が得られることを見出した。   In view of the above circumstances, as a result of intensive studies, the present inventors have improved the strength by making the inside of a forged product into a fibrous structure by controlling the components and the production process in an Al-Mg-Si alloy. However, it has been found that an aluminum alloy forged product having excellent stress corrosion cracking resistance can be obtained.
すなわち、本発明の請求項1に係る発明は、Si:0.8〜2.2mass%(以下、%と記す)、Cu:0.7〜1.5%、Mg:0.8〜1.8%、Mn:0.5〜1.1%、Zr:0.05〜0.30%を含み、残部がアルミニウムと不可避的不純物とからなるアルミニウム合金をZener−Hollomonの変数Zが2.9×1010≦Z≦6.6×1011であるように製造した鍛造品であり、該鍛造品の断面積の80%以上をアスペクト比が10以上の結晶粒からなる繊維状組織が占めることを特徴とする耐応力腐食割れ性に優れたアルミニウム合金製鍛造品である。 That is, according to the first aspect of the present invention, Si: 0.8 to 2.2 mass% (hereinafter referred to as%), Cu: 0.7 to 1.5%, Mg: 0.8 to 1. An aluminum alloy containing 8%, Mn: 0.5 to 1.1%, Zr: 0.05 to 0.30%, with the balance being aluminum and unavoidable impurities, has a Zener-Holomon variable Z of 2.9. × 10 10 ≦ Z ≦ 6.6 × 10 11 is a forged product manufactured such that a fibrous structure composed of crystal grains having an aspect ratio of 10 or more occupies 80% or more of the cross-sectional area of the forged product. It is a forged product made of an aluminum alloy excellent in stress corrosion cracking resistance.
本発明の請求項2に係る発明は、請求項1記載の鍛造品の製造方法において、常法により製造した押出材を490〜510℃に加熱し、該押出材を150〜200℃に加熱した金型で鍛造加工した鍛造品であり、該鍛造品に530〜550℃で3〜10hrの加熱を行った後、水冷または温水冷却し、さらに170〜190℃で6〜10hrの時効処理を施したことを特徴とする耐応力腐食割れ性に優れた鍛造品の製造方法である。   The invention according to claim 2 of the present invention is the method for manufacturing a forged product according to claim 1, wherein the extruded material manufactured by a conventional method is heated to 490 to 510 ° C, and the extruded material is heated to 150 to 200 ° C. This is a forged product that has been forged with a die. After heating the forged product at 530 to 550 ° C. for 3 to 10 hours, it is cooled with water or warm water, and further subjected to aging treatment at 170 to 190 ° C. for 6 to 10 hours. It is the manufacturing method of the forged product excellent in the stress corrosion cracking resistance characterized by having performed.
本発明によれば、高強度かつ耐応力腐食割れ性に優れたアルミニウム合金製鍛造品を提供することができ、自動車の足回り部品等の軽量化を可能にするものである。   ADVANTAGE OF THE INVENTION According to this invention, the forged product made from aluminum alloy excellent in the high intensity | strength and stress-corrosion cracking resistance can be provided, and weight reduction of an undercarriage part etc. of a motor vehicle is attained.
据え込み鍛造時の加工率の説明図である。It is explanatory drawing of the processing rate at the time of upset forging. 押出品および鍛造品の再結晶粒厚さ測定方法である。This is a method for measuring the recrystallized grain thickness of extruded products and forged products. カンチレバー式応力腐食試験である。This is a cantilever stress corrosion test.
以下、本発明の実施形態について説明する。
まず、本発明の各添加元素の役割について説明する。
Siは、Mgと共にMgSiを形成し、強度に寄与する元素である。Siが0.8%未満では形成されるMgSiが少なくなり、その効果が小さくなってしまう。2.2%を越えると押出加工時の表面性状、また鍛造加工時の変形抵抗が増大するため加工性が悪化する。したがって、Siは0.8〜2.2%とする。さらに好ましくは、0.8〜2.0%である。
Hereinafter, embodiments of the present invention will be described.
First, the role of each additive element of the present invention will be described.
Si is an element that forms Mg 2 Si together with Mg and contributes to strength. If Si is less than 0.8%, the amount of Mg 2 Si formed is reduced and the effect is reduced. If it exceeds 2.2%, the surface properties during extrusion and the deformation resistance during forging increase, so the workability deteriorates. Therefore, Si is 0.8 to 2.2%. More preferably, it is 0.8 to 2.0%.
Cuは、強度向上に寄与する。0.7%未満では強度向上の効果が小さく、1.5%を超えると押出加工性が低下する。また粒界への析出により耐食性が低下し、また、応力が付加された時に粒界に沿った亀裂が進行しやすくなると考えられるしたがって、Cuは0.7〜1.5%とする。さらに好ましくは、0.8〜1.2%である。   Cu contributes to strength improvement. If it is less than 0.7%, the effect of improving the strength is small, and if it exceeds 1.5%, the extrusion processability is lowered. Further, it is considered that the corrosion resistance is lowered due to precipitation at the grain boundary, and cracks along the grain boundary are likely to proceed when stress is applied. Therefore, Cu is set to 0.7 to 1.5%. More preferably, it is 0.8 to 1.2%.
Mgは、Siと共にMgSiを形成し、強度向上に寄与する。0.8%未満ではその効果が小さく、1.8%を超えると押出加工性が低下する。したがって、Mgは0.8〜1.8%とする。さらに好ましくは、0.8〜1.2%である。 Mg forms Mg 2 Si together with Si and contributes to strength improvement. If it is less than 0.8%, the effect is small, and if it exceeds 1.8%, the extrusion processability is lowered. Therefore, Mg is set to 0.8 to 1.8%. More preferably, it is 0.8 to 1.2%.
Mn、Zrは結晶粒の微細化に有効であり、強度向上に寄与する。Mnを0.5〜1.1%、Zrを0.05〜0.3%添加することにより押出加工後においても結晶粒粗大化を防止し、繊維状組織を維持することが出来る。しかし、所定量よりも添加量が多すぎると粗大な化合物を形成し、強度低下や靭性低下を招く。また、添加量が少ないと上記効果が現れない。したがって、Mn、Zrの成分範囲は、Mnが0.5〜1.1%、Zrが0.05〜0.3%である。さらに好ましくは、Mnは0.5〜0.7%、Zrは0.15〜0.2%である。   Mn and Zr are effective for refining crystal grains and contribute to the improvement of strength. By adding 0.5 to 1.1% of Mn and 0.05 to 0.3% of Zr, coarsening of crystal grains can be prevented even after extrusion, and a fibrous structure can be maintained. However, if the addition amount is too much than the predetermined amount, a coarse compound is formed, resulting in a decrease in strength and a decrease in toughness. Moreover, the said effect will not appear when there is little addition amount. Accordingly, the component ranges of Mn and Zr are 0.5 to 1.1% for Mn and 0.05 to 0.3% for Zr. More preferably, Mn is 0.5 to 0.7% and Zr is 0.15 to 0.2%.
また、本発明のアルミニウム合金には、その発明の効果を損なわない範囲でFe、Zn、Cr、Tiなどを1種または2種以上含んでも良い。具体的には、Feなら0.5%以下、Znなら0.25%以下、Crなら0.4%以下、Tiなら0.2%以下で添加することが可能である。   Further, the aluminum alloy of the present invention may contain one or more of Fe, Zn, Cr, Ti and the like within a range not impairing the effects of the present invention. Specifically, it is possible to add 0.5% or less for Fe, 0.25% or less for Zn, 0.4% or less for Cr, and 0.2% or less for Ti.
さらに、上記元素以外はアルミニウムと不可避的不純物とからなる。個々の不可避的不純物は0.05%以下であり、かつ総量で0.15%以下であることが好ましい。   Further, other than the above elements are composed of aluminum and inevitable impurities. Each inevitable impurity is 0.05% or less, and the total amount is preferably 0.15% or less.
次に、本発明の製造方法について説明する。
押出材は、常法により製造する。常法とは、連続鋳造により製造された前記合金組成を有する鋳塊を400〜490℃で3〜14hrの均質化処理を行った後、冷却、切断してビレットとする。そして、該ビレットを450〜500℃に加熱し押出し、冷却、切断し、該押出材とするものである。その後、予め150〜200℃に加熱した金型に490〜510℃に加熱した該押出材をセットした後、鍛造加工を施した鍛造品に、更に530〜550℃で3〜10hrの溶体化処理を施した後、水冷または温水冷却し、170〜190℃で6〜8hrの時効処理をすることが必要である。
Next, the manufacturing method of this invention is demonstrated.
The extruded material is produced by a conventional method. In the ordinary method, an ingot having the alloy composition manufactured by continuous casting is subjected to a homogenization treatment at 400 to 490 ° C. for 3 to 14 hours, and then cooled and cut into billets. Then, the billet is heated to 450 to 500 ° C., extruded, cooled, cut, and used as the extruded material. Then, after setting the extruded material heated to 490 to 510 ° C. in a mold heated to 150 to 200 ° C. in advance, the forged product subjected to forging is further subjected to a solution treatment for 3 to 10 hr at 530 to 550 ° C. It is necessary to carry out aging treatment at 170 to 190 ° C. for 6 to 8 hours after applying the above.
前記均質化処理は、鋳造時の偏析などをなくすために必要であり、本条件以外では、その後に行う押出加工時の面圧増加、また最終製品である鍛造品の表面品質の低下などを招く。押出時の加熱および鍛造時の加熱は変形抵抗を低減するために必要である。下限温度未満では加工性が悪化し、上限温度より高い温度では加工性などの特性が変わらなくなるので生産性の点から必要以上に温度を上げる必要はない。   The homogenization treatment is necessary to eliminate segregation at the time of casting. Except for this condition, the surface pressure is increased during the subsequent extrusion, and the surface quality of the forged product, which is the final product, is reduced. . Heating during extrusion and heating during forging are necessary to reduce deformation resistance. If the temperature is lower than the lower limit temperature, the workability deteriorates, and if the temperature is higher than the upper limit temperature, characteristics such as workability do not change. Therefore, it is not necessary to raise the temperature more than necessary from the viewpoint of productivity.
鍛造加工時の金型温度は、下限温度未満ではセットした材料温度が低下してしまい、加工性が低下する。一方、上限温度は材料温度を超えると加工時の材料の加工発熱などと大気放冷とのバランスが崩れ、必要以上に金型温度が高くなる。したがって、所定温度に設定することにより、材料温度、加工発熱、大気放冷などのバランスが取れ、安定した鍛造加工が可能となる。   If the mold temperature during forging is less than the lower limit temperature, the set material temperature is lowered, and the workability is lowered. On the other hand, if the upper limit temperature exceeds the material temperature, the balance between processing heat generated by the material during processing and air cooling will be lost, and the mold temperature will be higher than necessary. Therefore, by setting to a predetermined temperature, a balance between material temperature, processing heat generation, and air cooling can be achieved, and stable forging can be performed.
鍛造品の溶体化処理は、押出、鍛造工程で析出した化合物を固溶させるのに必要であり、下限温度未満あるいは下限時間未満では充分に固溶が進まず、上限温度より高い温度あるいは上限時間より長い時間では固溶の進行は飽和するため、製造コストの点で好ましくない。時効処理工程は、強度を得るために必要であり、前記条件以外の温度あるいは時間では充分な強度が得られない。   The solution treatment of the forged product is necessary for dissolving the compound precipitated in the extrusion and forging processes. If the temperature is less than the lower limit temperature or less than the lower limit time, the solid solution does not proceed sufficiently, and the temperature or upper limit time is higher than the upper limit temperature. A longer time is not preferable in terms of production cost because the progress of solid solution is saturated. The aging treatment step is necessary to obtain strength, and sufficient strength cannot be obtained at a temperature or time other than the above conditions.
本発明合金は、鍛造条件(鍛錬比、鍛造速度、温度など)により性能が変化する。本合金の特性をいかんなく発揮するために、温度補償ひずみ速度因子であるZener−Hollomonの変数Z(Z因子)を2.9×1010≦Z≦6.6×1011となるように、ひずみ速度および温度を制御することが必要である。ここでZ因子は、ひずみ速度をε、塑性変更の活性化エネルギーをQ、気体定数をR、絶対温度をTとすると、
Z=εexp(Q/RT)
で示される。また、亜結晶粒径dsは、
ds−1=a+blogZ(a、b:実験定数、Z:Z因子)
で示されるので、ひずみ速度と温度を管理することで、亜結晶粒径をコントロールし、繊維状組織とすることが可能である。ここでは、繊維状組織とは、下記の式で与えられるアスペクト比が10以上のものとした。
アスペクト比=(結晶最長長さ〔長手方向〕)/(結晶最短長さ〔長手方向と垂直〕)
アスペクト比が10未満の結晶粒は、粒界腐食を生ずる。
The performance of the alloy of the present invention varies depending on forging conditions (forging ratio, forging speed, temperature, etc.). In order to fully exhibit the characteristics of this alloy, the Zener-Holomon variable Z (Z factor), which is a temperature compensated strain rate factor, is 2.9 × 10 10 ≦ Z ≦ 6.6 × 10 11 , It is necessary to control the strain rate and temperature. Here, the Z factor is ε as strain rate, Q as activation energy for plastic change, R as gas constant, and T as absolute temperature.
Z = εexp (Q / RT)
Indicated by The subcrystal grain size ds is
ds −1 = a + blogZ (a, b: experimental constant, Z: Z factor)
Therefore, by controlling the strain rate and temperature, it is possible to control the subcrystal grain size to obtain a fibrous structure. Here, the fibrous structure is assumed to have an aspect ratio of 10 or more given by the following formula.
Aspect ratio = (longest crystal length [longitudinal]) / (shortest crystal length [perpendicular to longitudinal direction])
Crystal grains having an aspect ratio of less than 10 cause intergranular corrosion.
したがって、繊維状組織を有する鍛造品を得るためには、鍛造加工時の温度とひずみ速度(つまり、鍛造加工速度)を制御し、Z因子を上記範囲に設定する必要がある。Z因子が上記範囲以外では、鍛造後の断面において繊維状組織の割合が減少、つまり、再結晶の割合が増え、結果として耐応力腐食割れ性に悪影響を及ぼす。   Therefore, in order to obtain a forged product having a fibrous structure, it is necessary to control the temperature and strain rate during forging (that is, the forging rate) and set the Z factor within the above range. When the Z factor is outside the above range, the ratio of the fibrous structure decreases in the cross-section after forging, that is, the ratio of recrystallization increases, and as a result, the stress corrosion cracking resistance is adversely affected.
次に実施例に基づき本発明を詳細に説明する。   Next, based on an Example, this invention is demonstrated in detail.
表1に示す組成の合金を溶解し、直径220mmの鋳塊を得、該鋳塊に490℃で4hrの均質化処理を施した後、冷却、切断してビレットを作製した。該ビレットを500℃の押出により直径60mmの押出丸棒を作製した。該押出丸棒を長さ150mmに切断し、485〜510℃に加熱し、200℃に加熱した金型で、押出丸棒を横に寝かし30mm/sおよび270mm/sの加工速度で加工率50%の据え込み鍛造を施した。該鍛造品を更に530〜550℃で2.5〜10時間の溶体化処理の後、直ちに50℃の温水で焼入れをし、さらに160〜180℃で6〜10hrの人工時効処理を行い、材質をT6とした。   An alloy having a composition shown in Table 1 was melted to obtain an ingot having a diameter of 220 mm. The ingot was subjected to homogenization treatment at 490 ° C. for 4 hours, and then cooled and cut to produce a billet. The billet was extruded at 500 ° C. to produce an extruded round bar having a diameter of 60 mm. The extruded round bar was cut to a length of 150 mm, heated to 485 to 510 ° C., and the extruded round bar was laid sideways with a mold heated to 200 ° C., at a processing rate of 30 mm / s and 270 mm / s. % Upset forging. The forged product was further subjected to solution treatment at 530 to 550 ° C. for 2.5 to 10 hours, immediately quenched with hot water at 50 ° C., and further subjected to artificial aging treatment at 160 to 180 ° C. for 6 to 10 hours. Was T6.
ここで加工率50%とは、図1において、(r−r)/r×100において計算された値である。rは据え込み鍛造前のアルミニウム合金棒の直径であり、rは据え込み鍛造後のアルミニウム合金棒の直径である。 Here, the processing rate of 50% is a value calculated by (r 1 −r 2 ) / r 1 × 100 in FIG. r 1 is the diameter of the aluminum alloy rod before upset forging, and r 2 is the diameter of the aluminum alloy rod after upset forging.
このようにして得られた上記試験合金鍛造品について引張試験および組織観察、耐応力腐食割れ性評価を行った。この結果を表2に示す。   The test alloy forged product thus obtained was subjected to a tensile test, structure observation, and stress corrosion cracking resistance evaluation. The results are shown in Table 2.
1)引張試験
引張試験片は、鍛造品の中央から押出棒の長手方向が試験片の長さ方向になるように採取し、JIS4号試験片を作成し、試験を行った。
ここで、一般合金である6066合金T6の引張強度(TS=395MPa)を基準とし、これと同等以上の引張強度を○、強度が該基準に満がたないものを×とした。
1) Tensile test Tensile test pieces were sampled from the center of the forged product so that the longitudinal direction of the extruded bar was in the length direction of the test piece, and a JIS No. 4 test piece was prepared and tested.
Here, the tensile strength (TS = 395 MPa) of 6066 alloy T6, which is a general alloy, was used as a reference, a tensile strength equal to or higher than this was indicated by ◯, and the strength not satisfying the reference was indicated by ×.
2)組織観察
断面観察により、繊維状組織の占める面積の断面積に対する比率を求めた。鍛造加工では、表層部に加工歪が集中することにより、鍛造加工品の断面観察を行うと表層部には再結晶粒が見られる。図2に組織の違いが均一に生じた場合のモデル図を示す。繊維状組織の割合は、鍛造加工品の全断面積S、鍛造加工品の再結晶している部分の断面積Sを画像解析により測定し、以下の式にて算出した。
繊維状組織の割合:(S−S)/S×100
繊維状組織の割合が80%以上であり、かつアスペクト比が10以上の場合を○、これ以外のものを×とした。ここにアスペクト比は、結晶粒の長辺と短辺の比で表される。アスペクト比の測定は、断面マクロを観察後、繊維状組織部を光学顕微鏡により観察した。繊維状組織部は外周近い(再結晶組織部に近い)部位と中心から切り出し、光学顕微鏡にて倍率200〜100で観察し、長辺と短辺長さを測定し、比を求めた。
2) Microstructure observation The ratio of the area occupied by the fibrous tissue to the cross-sectional area was determined by cross-sectional observation. In the forging process, processing strain concentrates on the surface layer portion, and when the cross-section of the forged product is observed, recrystallized grains are observed on the surface layer portion. FIG. 2 shows a model diagram in the case where the difference in structure occurs uniformly. The ratio of the fibrous structure was calculated from the following equation by measuring the total cross-sectional area S 0 of the forged product and the cross-sectional area S r of the recrystallized portion of the forged product by image analysis.
Ratio of fibrous structure: (S 0 -S r ) / S 0 × 100
The case where the ratio of the fibrous structure was 80% or more and the aspect ratio was 10 or more was rated as ◯, and the other cases were marked as x. Here, the aspect ratio is represented by the ratio of the long side to the short side of the crystal grain. The aspect ratio was measured by observing the cross-sectional macro and then observing the fibrous tissue portion with an optical microscope. The fibrous tissue part was cut out from the part near the outer periphery (close to the recrystallized structure part) and the center, observed with an optical microscope at a magnification of 200 to 100, the long side and the short side length were measured, and the ratio was determined.
3)耐応力腐食割れ性
JIS8711「アルミニウム合金の応力腐食割れ試験方法」にならい試験片を作成し、耐力値の90%の応力を付与し、交互浸漬試験を実施した。また、併せて約95℃のクロム酸浸漬試験、カンチレバー式応力腐食割れ試験も実施した。カンチレバー式応力腐食割れ試験とは、図3に示すように片もち状の冶具に試験片をセットし、試験片に電流をかけ、強制的に破断させるものである。本試験では、25℃の食塩水中で、5mA/cmの電流をかけて試験を行った。応力腐食割れ試験開始から100hr経過後に腐食生成物に覆われ割れが見られなかったものを○、腐食性生物に覆われる前もしくは覆われた部位に微細な割れが見られたものを×とした。
3) Stress corrosion cracking resistance A test piece was prepared in accordance with JIS 8711 “Testing method for stress corrosion cracking of aluminum alloy”, stress of 90% of the proof stress value was applied, and an alternate immersion test was performed. In addition, a chromic acid immersion test at about 95 ° C. and a cantilever stress corrosion cracking test were also conducted. In the cantilever stress corrosion cracking test, as shown in FIG. 3, a test piece is set on a piece-like jig and a current is applied to the test piece to forcibly break it. In this test, the test was performed by applying a current of 5 mA / cm 2 in a 25 ° C. saline solution. A sample in which no cracks were observed after 100 hours had elapsed from the start of the stress corrosion cracking test, and a sample in which fine cracks were observed before or after being covered with corrosive organisms were marked with ×. .
実施例1〜15は、機械的性質がA6066−T6の引張強さ395MPa以上を満たし、また、鍛造後の製品断面の繊維状組織占有率が80%以上となり、応力腐食割れが発生しなかった。一方、比較例16〜25は、成分が本発明の範囲を外れるか、鍛造加工後の溶体化処理または人工時効処理の熱処理条件が規定範囲を外れたため、機械的性質がA6066合金(T6)の規格引張強さ395MPa以上を満足されなかった、また比較例16〜19、26〜30は、組織微細化に寄与するZr添加量が規定範囲を下回る、または、Z値が管理範囲を外れているために鍛造後の製品断面の繊維状組織占有率が80%以下となり、結果応力腐食割れ試験において、微小なクラックが見られた。   In Examples 1 to 15, the mechanical properties satisfy A6066-T6 tensile strength of 395 MPa or more, the fibrous structure occupancy of the product cross-section after forging is 80% or more, and stress corrosion cracking does not occur. . On the other hand, in Comparative Examples 16 to 25, the components are out of the scope of the present invention, or the heat treatment conditions for solution treatment or artificial aging treatment after forging are out of the specified range, so the mechanical properties of the A6066 alloy (T6) In Comparative Examples 16-19 and 26-30, the standard tensile strength of 395 MPa or more was not satisfied, and the Zr addition amount contributing to the refinement of the structure was below the specified range, or the Z value was outside the control range Therefore, the fiber structure occupation ratio of the product cross-section after forging was 80% or less, and as a result, micro cracks were observed in the stress corrosion cracking test.
本発明は、Al−Mg−Si系合金において、Mg、Siの添加量のみならず、Cu添加により、6061合金などの合金と比べ更に高強度で、かつMn、Zrを添加することとZ因子を制御することにより鍛造品繊維状組織となる。その結果、本発明合金は、高強度かつ耐応力腐食割れ性に優れた特性を有し、自動車の足回り等の部品に活用することで、自動車の軽量化を図ることが可能であり、工業上顕著な効果を奏するものである。   The present invention relates to the addition of Mn and Zr to an Al—Mg—Si based alloy by adding not only Mg and Si, but also Cu, and adding Mn and Zr by adding Cu and the Z factor. It becomes a forged product fibrous structure by controlling. As a result, the alloy of the present invention has characteristics of high strength and excellent stress corrosion cracking resistance, and can be used for parts such as automobile undercarriage to reduce the weight of the automobile. It has a remarkable effect.
1:アルミニウム合金棒
2:ダイス
3:繊維状組織部
4:再結晶組織部
1: Aluminum alloy rod 2: Die 3: Fibrous structure part 4: Recrystallized structure part

Claims (2)

  1. Si:0.8〜2.2mass%(以下、%と記す。)、Cu:0.7〜1.5%、Mg:0.8〜1.8%、Mn:0.5〜1.1%、Zr:0.05〜0.30%を含み、残部がアルミニウムと不可避的不純物とからなるアルミニウム合金をZener−Hollomonの変数Zが2.9×1010≦Z≦6.6×1011であるように製造した鍛造品であり、該鍛造品の断面積の80%以上をアスペクト比が10以上の結晶粒からなる繊維状組織が占めることを特徴とする耐応力腐食割れ性に優れた高強度アルミニウム合金製鍛造品。 Si: 0.8-2.2 mass% (hereinafter referred to as%), Cu: 0.7-1.5%, Mg: 0.8-1.8%, Mn: 0.5-1.1 %, Zr: 0.05 to 0.30%, and the balance Zer-Holomon variable Z is 2.9 × 10 10 ≦ Z ≦ 6.6 × 10 11 , with the balance being aluminum and inevitable impurities. It is a forged product manufactured so that it has excellent stress corrosion cracking resistance, characterized in that a fibrous structure comprising crystal grains having an aspect ratio of 10 or more occupies 80% or more of the cross-sectional area of the forged product Forged product made of high-strength aluminum alloy.
  2. 請求項1記載の鍛造品の製造方法において、常法により製造した押出材を490〜510℃に加熱し、該押出材を150〜200℃に加熱した金型で鍛造加工した鍛造品であり、該鍛造品に530〜550℃で3〜10hrの加熱を行った後、水冷または温水冷却し、さらに170〜190℃で6〜10hrの時効処理を施したことを特徴とする耐応力腐食割れ性に優れた高強度アルミニウム合金鍛造品の製造方法。   The method for producing a forged product according to claim 1, wherein the extruded material produced by a conventional method is heated to 490 to 510 ° C, and the extruded material is forged with a mold heated to 150 to 200 ° C. The forged product is heated at 530 to 550 ° C. for 3 to 10 hours, then cooled with water or warm water, and further subjected to aging treatment at 170 to 190 ° C. for 6 to 10 hours, which is characterized by resistance to stress corrosion cracking For producing high-strength aluminum alloy forgings with excellent resistance.
JP2010245752A 2010-11-02 2010-11-02 High-strength aluminum alloy forged product excellent in stress corrosion cracking resistance and forging method for the same Pending JP2012097321A (en)

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US20160233009A1 (en) * 2013-09-25 2016-08-11 Fujikura Ltd. High-frequency wire and high-frequency coil
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US20170167001A1 (en) * 2015-12-14 2017-06-15 Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.) Forged aluminum alloy for automobiles
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US10026526B2 (en) * 2013-09-25 2018-07-17 Fujikura Ltd. High-frequency wire and high-frequency coil
US20160233009A1 (en) * 2013-09-25 2016-08-11 Fujikura Ltd. High-frequency wire and high-frequency coil
CN104745902B (en) * 2013-12-30 2017-02-08 鼎镁(昆山)新材料科技有限公司 High strength Al-Mg-Si-Cu alloy for bicycles and processing technology thereof
JP2015166480A (en) * 2014-03-03 2015-09-24 住友電気工業株式会社 Aluminum alloy, aluminum alloy wire material, method for producing aluminum alloy wire material, method for producing aluminum alloy member and aluminum alloy member
EP3018226A1 (en) 2014-11-05 2016-05-11 Constellium Valais SA (AG, Ltd) Ultra high strength products forged from 6xxx aluminium alloys having excellent corrosion resistance
US20170167001A1 (en) * 2015-12-14 2017-06-15 Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.) Forged aluminum alloy for automobiles
EP3299482A1 (en) 2016-09-21 2018-03-28 Aleris Aluminum Duffel BVBA High-strength 6xxx-series forging material
WO2018181329A1 (en) * 2017-03-27 2018-10-04 古河電気工業株式会社 Aluminium alloy material, conductive member using same, conductive component, spring member, spring component, semiconductor module member, semiconductor module component, structure member, and structure component
CN109468508A (en) * 2018-12-26 2019-03-15 东莞市铝美铝型材有限公司 A kind of aluminum alloy materials and preparation method thereof for electric automobile power battery pallet
CN110343914A (en) * 2019-08-30 2019-10-18 安徽环宇铝业有限公司 A kind of production technology of road guard-rail aluminium alloy rod

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