JP4707075B2

JP4707075B2 - Aluminum alloy with excellent machinability

Info

Publication number: JP4707075B2
Application number: JP2000386180A
Authority: JP
Inventors: 伸二吉原; 正和平野
Original assignee: Kobe Steel Ltd
Current assignee: Kobe Steel Ltd
Priority date: 1999-12-21
Filing date: 2000-12-20
Publication date: 2011-06-22
Anticipated expiration: 2020-12-20
Also published as: JP2001240931A

Description

【０００１】
【発明の属する技術分野】
本発明は、切削性に優れたアルミニウム合金に関するものである。
【０００２】
【従来の技術】
アルミニウム合金のうち特に２０００系のＡｌ−Ｃｕ合金を中心とした熱処理型合金は高い機械的性質をもち、航空機等の各種構造材としての使用実績が多い。この系の合金の一般的な加工法として、押出後、切削加工や穴あけ加工を施される場合が多いが、例えば２０１４合金や２０２４合金等は切削時に発生する切り屑が分断されにくいため切削性が劣り、複雑な切削や穴あけ加工する機械部品への採用が困難であった。
【０００３】
一方、この系のアルミニウム合金押出材の切削性を向上させるためには、従来は例えばＡＡ２０１１合金（Ｃｕ：５．０〜６．０％、Ｐｂ：０．２〜０．６％、Ｂｉ：０．２〜０．６％、残部Ａｌ）のように、Ｐｂ、Ｂｉ等の低融点金属が添加された。これら低融点金属はアルミニウム中にほとんど固溶せず、アルミニウム合金中に粒状に存在し、その低融点金属粒子が切削加工時の加工発熱により溶融して切り屑を分断し（溶融脆化）、アルミニウム合金押出材の切削性を向上させる。
【０００４】
【発明が解決しようとする課題】
ところが、近年の地球環境保護要求の高まりを受け、Ｐｂなどの有害成分の使用を規制する動きが大きくなってきた。Ｐｂは人体に摂取されると蓄積し、神経障害、貧血などのＰｂ中毒症を引き起こす。
国内では１９９７年に通産省が「品目別廃棄物処理・再資源化ガイドライン」を設定し、自動車とオートバイに対してＰｂ使用量削減に関する数値目標を設定した。これを受けて自動車メーカー各社は自主行動計画を策定した。一方、欧州連合ＥＵでは、「包装および包装廃棄物に関する指令」や「使用済み自動車に関するＥＵ指令案」があり、有害物質であるＰｂやＣｄ、Ｈｇ、６価Ｃｒの使用量を削減することを規定している。
【０００５】
本発明はこのような情勢に鑑みてなされたもので、Ｐｂを含まずに従来のＡＡ２０１１合金と同等の機械的性質及び耐食性を備え、しかも切削性に優れたアルミニウム合金を得ることを目的とする。
【０００６】
【課題を解決するための手段】
本発明者らは前記課題を解決するために鋭意研究を重ねた結果、ＡＡ２０１１合金等の高切削性アルミニウム合金に切削性を向上させる目的で添加されていたＰｂを添加せず、代わりにＳｎ及びＢｉを同時添加することで上記目的を達成できることを見い出し、その知見を基に本発明を完成するに至った。
すなわち、本発明に関わる切削性に優れたアルミニウム合金は、Ｃｕ：４．８〜５．９％、Ｂｉ：０．３〜１．０％、Ｓｎ：０．３〜１．０％、Ｔｉ：０．００５〜０．０５％を含有し、残部がＡｌ及び不純物からなり、熱間加工後、溶体化・焼入れ処理及び時効処理を施したことを特徴とする。また、本発明に関わる切削性に優れたアルミニウム合金は、必要に応じて、さらに、Ｍｇ：０．４〜１．０％を含有し、又は／及びＭｎ：０．０５〜０．５％、Ｃｒ：０．０５〜０．５％、Ｚｒ：０．０５〜０．５％のうち１種以上を含有する。上記アルミニウム合金において、ＢｉとＳｎの合計含有量は０．６〜１．４％であることが望ましい。
【０００７】
上記アルミニウム合金は切り屑の分断性がよく、長い切り屑による工具への切り屑の巻き付き等のトラブルが発生しない。また、切削性向上のためＰｂを添加していないので、ＡＡ２０１１合金と比較して環境を配慮したものとなっている。
なお、上記アルミニウム合金は、常法に従い溶解、鋳造、均質化処理を施した後、例えば押出加工又は圧延加工などの熱間加工を行い、得られた押出材あるいは圧延材（棒材等）に溶体化、焼入れ、時効処理を施し所定の強度を与えた後、切削加工に供する。
【０００８】
次に、上記アルミニウム合金材における各元素の添加理由及び添加量の限定理由を説明する。
【０００９】
Ｃｕ：４．８〜５．９％
Ｃｕは熱処理により強度を高めるとともに、歪み硬化能を向上させるため切り屑分断を助長する。Ｃｕ含有量が４．８％未満ではその効果に乏しく、一方５．９％を越えて添加すると耐食性が低下し、また熱間加工性（押出性等）も低下する。望ましくは５．５％以下、特に強度と良好な耐食性及び熱間加工性を確保するとの観点から、５％を越え、５．４％以下が望まれる。
【００１０】
Ｂｉ：０．３〜１．０％
Ｓｎ：０．３〜１．０％
Ｂｉ及びＳｎを同時に添加することにより、低融点のＢｉ−Ｓｎ合金の微粒子がアルミニウム合金中に分散され、切削加工熱による切り屑の溶融脆化が起こり、優れた切り屑分断性が得られる。ＢｉとＳｎの含有量が共晶組成（Ｂｉ：Ｓｎ＝５７：４３）に近いほど分散粒子の融点を低下させることができ、切り屑の溶融脆化の効率が上がる。一方、Ｂｉ単独又はＳｎ単独、あるいは同時添加されていてもＢｉとＳｎの含有量が共晶組成から外れるほど分散粒子の融点が高くなり、切削加工熱による切り屑の溶融脆化の効率が低く、切り屑分断性に劣るようになる。しかも、Ｂｉ及びＳｎは単独添加であると結晶粒界に偏析し、伸びが低下する。さらに、ＢｉとＳｎの含有量が少ないと切削性改善の効果が少なく、含有量が多くなると伸び及び耐食性を低下させる。以上の点から、ＢｉとＳｎは同時に添加することとし、その含有量は共に０．３〜１．０％とした。合計含有量は望ましくは０．６〜１．４％である。
【００１１】
Ｔｉ：０．００５〜０．０５％
Ｔｉは鋳造組織を微細化して機械的性質を安定化する。しかし、Ｔｉ含有量が０．００５％未満ではその効果が得られず、一方０．０５％を越えて添加してもその効果は飽和する。
Ｍｇ：０．４〜１．０％
Ｍｇは、Ｃｕ、Ａｌとの共存によって、Ａｌ_２ＣｕＭｇとなって析出し、強度を高める効果があり、さらに歪み硬化能を助長し切り屑分断性を高める。Ｍｇ含有量が０．４％未満ではその効果が得られず、一方、１．０％を越えて添加すると熱間加工性（押出性等）が低下する。特に強度と良好な熱間加工性を確保するとの観点から、添加する場合は０．６％以上、０．８％以下が望ましい。
【００１２】
Ｍｎ：０．０５〜０．５％
Ｃｒ：０．０５〜０．５％
Ｚｒ：０．０５〜０．５％
Ｍｎ、Ｃｒ、ＺｒはそれぞれＡｌとの化合物を形成し、切り屑分断の起点となって切削性を向上させるため、適宜１種以上を添加する。添加量がそれぞれ０．０５％未満ではその効果が十分でなく、一方、０．５％を越えると粗大な化合物を生成し熱間加工性（押出性等）が低下する。
【００１３】
不純物
不純物のうちＦｅ及びＳｉはアルミニウム合金に多く含まれる不純物であり、それぞれ０．３５％、０．２％を超えて前記アルミニウム合金中に存在すると粗大な金属間化合物を晶出し、合金の機械的性質を損なう。従って、Ｆｅ、Ｓｉの含有量はそれぞれ０．３５％、０．２％以下に規制する。また、アルミニウム合金を鋳造する際には地金、添加元素の中間合金等様々な経路より不純物が混入する。混入する元素は様々であるが、Ｆｅ以外の不純物は単体で０．０５％以下、総量で０．１５％以下であれば前記アルミニウム合金の特性にほとんど影響を及ぼさない。従って、これらの不純物は単体で０．０５％以下、総量で０．１５％以下とする。なお、不純物のうちＢについては、Ｔｉの添加に伴い合金中にＴｉ含有量の１／５程度の量で混入するが、より望ましい範囲は０．０２％以下、さらに０．０１％以下が望ましい。
【００１４】
【実施例】
以下、本発明の実施例について、比較例と比較して具体的に説明する。
表１に示した化学組成の合金を溶解し半連続鋳造により１６０ｍｍ径の押出ビレットを作成し、４７０℃で４時間均質化熱処理を施した後、４００℃の押出温度で４６ｍｍ径に押し出し、これを５２０℃で１時間溶体化処理して水中に焼入れた後、１４５℃で９ｈｒの人工時効処理を行った。これを供試材とし、各々の機械的性質、切削性、耐食性を下記の要領で測定した。また、押出性をみるため上記押出では押出荷重を一定（６００トン）とし、その押出速度（押出材が出てくるときの速度）を計測し、各押出材の押出性を下記の要領で評価した。
【００１５】
【表１】

【００１６】
機械的性質；押出方向に採取したＪＩＳ４号試験片を用い、ＪＩＳＺ２２４１に規定する金属材料試験方法に準じ、引張強さ、耐力、及び伸びを測定した。
切削性；市販の高速度鋼製の４ｍｍ径ドリルを用い、回転数１５００ｍｍ／分、送り３００ｍｍ／分の条件にて切削し、ドリルへの巻き付き発生の有無を観察するとともに、切り屑分断性を調べるために切り屑１００ｇ当りの切り屑個数を測定した。
耐食性；２００時間のＳＳＴ試験（塩水噴霧試験方法）をＪＩＳＺ１２７１の規定に準じて行い、単位面積当りの重量減少を測定した。
押出性；押出速度の値が５ｍ／分より大のとき◎（優れている）、２〜５ｍ／分のとき○（使用可能である）、２ｍ／分より小のとき×（使用に耐えない）と評価した。
【００１７】
これらの試験結果を表２に示す。
本発明の実施例に相当する合金１〜５は、いずれも優れた機械的性質、切削性及び耐食性を示す。また、押出材にはむしれや焼き付き痕はなく表面性状は良好で、押出性も優れている。
これに対し、比較例の合金６〜１３は組成が本発明の範囲外の合金であり、いずれも何らかの特性が実施例合金１〜５に比べ劣っている。すなわち、合金６はＣｕの含有量が過剰のため押出性と耐食性が劣り、合金７はＣｕの含有量が不足するため切削性に劣り、合金８はＢｉ及びＳｎの含有量が過剰のため伸びが低く耐食性も劣り、合金９はＢｉ及びＳｎの含有量が不足するため切削性に劣り、合金１０はＳｎの添加がなく、合金１１はＢｉの添加がないため、切削性に劣りびも低く、合金１２はＢｉが過剰、合金１３はＳｎが過剰のため伸びが低く退職性が劣る。
【００１８】
【表２】

【００１９】
【発明の効果】
このように、本発明では、所定量のＣｕを含有するアルミニウム合金において、ＢｉとＳｎを同時添加することにより、従来のＡＡ２０１１合金のようにＰｂを使用せずに切削性を向上させることができ、近年の地球環境保護要求の高まりに応えることができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an aluminum alloy excellent in machinability.
[0002]
[Prior art]
Among aluminum alloys, heat-treatable alloys centering on 2000 series Al—Cu alloys have high mechanical properties and have been used as various structural materials such as aircraft. As a general processing method of this type of alloy, cutting and drilling are often performed after extrusion. For example, in 2014 alloy and 2024 alloy, chips generated at the time of cutting are difficult to be cut, so that cutting performance is improved. It was inferior, and it was difficult to adopt it for machine parts that performed complicated cutting and drilling.
[0003]
On the other hand, in order to improve the machinability of the aluminum alloy extruded material of this type, conventionally, for example, an AA2011 alloy (Cu: 5.0 to 6.0%, Pb: 0.2 to 0.6%, Bi: 0). Low melting point metals such as Pb and Bi were added, such as .2 to 0.6% and the balance Al). These low-melting-point metals are hardly dissolved in aluminum and are present in granular form in the aluminum alloy, and the low-melting-point metal particles are melted by processing heat generated during cutting to break up chips (melt embrittlement). Improves machinability of aluminum alloy extruded material.
[0004]
[Problems to be solved by the invention]
However, in response to the recent increase in demands for protecting the global environment, there has been an increasing movement to regulate the use of harmful components such as Pb. Pb accumulates when ingested by the human body and causes Pb poisoning such as neuropathy and anemia.
In Japan, the Ministry of International Trade and Industry established “Guidelines for Waste Disposal and Recycling by Item” in 1997, and set numerical targets for Pb usage reduction for automobiles and motorcycles. In response, automakers have developed voluntary action plans. On the other hand, the European Union EU has a “Direction on Packaging and Packaging Waste” and an “EU Directive on Used Vehicles” to reduce the use of harmful substances such as Pb, Cd, Hg, and hexavalent Cr. It prescribes.
[0005]
The present invention has been made in view of such circumstances, and an object thereof is to obtain an aluminum alloy that does not contain Pb, has mechanical properties and corrosion resistance equivalent to those of a conventional AA2011 alloy, and has excellent machinability. .
[0006]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventors did not add Pb, which was added for the purpose of improving the machinability to a high machinability aluminum alloy such as AA2011 alloy, instead of Sn and The inventors have found that the above object can be achieved by adding Bi simultaneously, and have completed the present invention based on the findings.
That is, the aluminum alloy excellent in machinability according to the present invention is Cu: 4.8 to 5.9%, Bi: 0.3 to 1.0%, Sn: 0.3 to 1.0%, Ti: It contains 0.005 to 0.05%, the balance is made of Al and impurities, and after hot working, it is subjected to solution treatment / quenching treatment and aging treatment. Moreover, the aluminum alloy excellent in machinability according to the present invention further contains Mg: 0.4 to 1.0%, or / and Mn: 0.05 to 0.5%, if necessary. One or more of Cr: 0.05 to 0.5% and Zr: 0.05 to 0.5% are contained. In the aluminum alloy, the total content of Bi and Sn is preferably 0.6 to 1.4%.
[0007]
The above-mentioned aluminum alloy has good chip separation, and troubles such as winding of chips around a tool due to long chips do not occur. Moreover, since Pb is not added for improving machinability, the environment is considered in comparison with the AA2011 alloy.
The aluminum alloy is melted, cast, and homogenized according to a conventional method, and then subjected to hot working such as extrusion or rolling, and the obtained extruded material or rolled material (bar material, etc.) Solution treatment, quenching, and aging treatment are performed to give a predetermined strength, and then subjected to cutting.
[0008]
Next, the reason for adding each element in the aluminum alloy material and the reason for limiting the addition amount will be described.
[0009]
Cu: 4.8 to 5.9%
Cu enhances the strength by heat treatment and promotes chip breaking in order to improve strain hardening ability. When the Cu content is less than 4.8%, the effect is poor. On the other hand, when the Cu content exceeds 5.9%, the corrosion resistance is lowered and the hot workability (extrudability, etc.) is also lowered. Desirably, it is 5.5% or less, and more than 5% and 5.4% or less is particularly desired from the viewpoint of securing strength and good corrosion resistance and hot workability.
[0010]
Bi: 0.3-1.0%
Sn: 0.3-1.0%
By adding Bi and Sn at the same time, fine particles of the low melting point Bi—Sn alloy are dispersed in the aluminum alloy, and the chips are melted and embrittled by cutting heat, and excellent chip breaking properties are obtained. The closer the Bi and Sn content is to the eutectic composition (Bi: Sn = 57: 43), the lower the melting point of the dispersed particles, and the higher the efficiency of chip melting and embrittlement. On the other hand, even if Bi alone or Sn alone or simultaneously added, the melting point of the dispersed particles increases as the content of Bi and Sn deviates from the eutectic composition, and the efficiency of melting and embrittlement of chips by cutting heat is low. It becomes inferior to chip breaking property. In addition, if Bi and Sn are added alone, they segregate at the grain boundaries and the elongation is lowered. Further, if the content of Bi and Sn is small, the effect of improving the machinability is small, and if the content is large, the elongation and the corrosion resistance are lowered. From the above points, Bi and Sn were added at the same time, and their contents were both 0.3 to 1.0%. The total content is desirably 0.6 to 1.4%.
[0011]
Ti: 0.005 to 0.05%
Ti refines the cast structure and stabilizes the mechanical properties. However, if the Ti content is less than 0.005%, the effect cannot be obtained. On the other hand, even if added over 0.05%, the effect is saturated.
Mg: 0.4 to 1.0%
Mg coexists with Cu and Al and precipitates as Al ₂ CuMg, which has the effect of increasing strength, further promotes strain hardening ability and improves chip breaking. If the Mg content is less than 0.4%, the effect cannot be obtained. On the other hand, if the Mg content exceeds 1.0%, hot workability (extrudability, etc.) is lowered. In particular, from the viewpoint of securing strength and good hot workability, when it is added, it is desirable that the content be 0.6% or more and 0.8% or less.
[0012]
Mn: 0.05 to 0.5%
Cr: 0.05-0.5%
Zr: 0.05 to 0.5%
Mn, Cr, and Zr each form a compound with Al and serve as a starting point for chip separation to improve machinability, so that one or more kinds are appropriately added. When the addition amount is less than 0.05%, the effect is not sufficient. On the other hand, when the addition amount exceeds 0.5%, a coarse compound is produced and hot workability (extrudability, etc.) is lowered.
[0013]
Among the impurity impurities, Fe and Si are impurities contained in a large amount in the aluminum alloy, and if present in the aluminum alloy exceeding 0.35% and 0.2%, a coarse intermetallic compound is crystallized, and the alloy machine Impair the physical properties. Therefore, the contents of Fe and Si are restricted to 0.35% and 0.2% or less, respectively. Further, when casting an aluminum alloy, impurities are mixed from various paths such as a metal base and an intermediate alloy of an additive element. The elements to be mixed vary, but impurities other than Fe alone are 0.05% or less, and if the total amount is 0.15% or less, the characteristics of the aluminum alloy are hardly affected. Accordingly, these impurities are 0.05% or less as a single substance, and the total amount is 0.15% or less. In addition, about impurity B, it mixes with the amount of about 1/5 of Ti content in an alloy with addition of Ti, but a more desirable range is 0.02% or less, Furthermore, 0.01% or less is desirable. .
[0014]
【Example】
Examples of the present invention will be specifically described below in comparison with comparative examples.
An alloy having the chemical composition shown in Table 1 was melted to produce a 160 mm diameter extruded billet by semi-continuous casting, subjected to a homogenization heat treatment at 470 ° C. for 4 hours, and then extruded to a 46 mm diameter at an extrusion temperature of 400 ° C. After solution treatment at 520 ° C. for 1 hour and quenching in water, an artificial aging treatment was performed at 145 ° C. for 9 hours. Using this as a test material, the respective mechanical properties, machinability, and corrosion resistance were measured in the following manner. In order to check extrudability, in the above extrusion, the extrusion load is constant (600 tons), the extrusion speed (speed when the extruded material comes out) is measured, and the extrudability of each extruded material is evaluated as follows. did.
[0015]
[Table 1]

[0016]
Mechanical properties: Tensile strength, proof stress, and elongation were measured using a JIS No. 4 test piece collected in the extrusion direction in accordance with a metal material test method specified in JIS Z2241.
Cutting performance: Using a commercially available 4 mm diameter drill made of high-speed steel, cutting was performed under the conditions of a rotation speed of 1500 mm / min and a feed of 300 mm / min. In order to investigate, the number of chips per 100 g of chips was measured.
Corrosion resistance: A 200-hour SST test (salt spray test method) was performed in accordance with the provisions of JISZ1271, and the weight loss per unit area was measured.
Extrudability: When the value of the extrusion speed is greater than 5 m / min, ◎ (excellent), when 2-5 m / min, ○ (can be used), when less than 2 m / min, x (not useable) ).
[0017]
These test results are shown in Table 2.
Alloys 1 to 5 corresponding to the examples of the present invention all exhibit excellent mechanical properties, machinability and corrosion resistance. In addition, the extruded material has no peeling or burn-in trace, has a good surface property, and has excellent extrudability.
On the other hand, the alloys 6 to 13 of the comparative examples are alloys whose composition is outside the range of the present invention, and any characteristics are inferior to those of the examples alloys 1 to 5. That is, alloy 6 is inferior in extrudability and corrosion resistance due to excessive Cu content, alloy 7 is inferior in machinability due to insufficient Cu content, and alloy 8 is elongated due to excessive Bi and Sn content. However, alloy 9 is inferior in machinability due to lack of Bi and Sn contents, alloy 10 has no addition of Sn, and alloy 11 has no addition of Bi, so inferior in machinability. The alloy 12 has an excess of Bi, and the alloy 13 has an excess of Sn, so the elongation is low and the retirement property is inferior.
[0018]
[Table 2]

[0019]
【The invention's effect】
Thus, in the present invention, in an aluminum alloy containing a predetermined amount of Cu, by simultaneously adding Bi and Sn, the machinability can be improved without using Pb as in the case of the conventional AA2011 alloy. Therefore, it can meet the increasing demand for global environmental protection in recent years.

Claims

Cu: 4.8 to 5.5 % (mass%, the same applies hereinafter), Bi: 0.3 to 0.5 %, Sn: 0.3 to 0.5 %, Ti: 0.005 to 0.05% An aluminum alloy excellent in machinability, characterized in that the remainder is made of Al and impurities, and is subjected to solution treatment, quenching treatment and aging treatment after hot working.

Furthermore, Mg: 0.4-1.0% is contained, The aluminum alloy excellent in the machinability described in Claim 1 characterized by the above-mentioned.

Furthermore, 1 or more types are contained among Mn: 0.05-0.5%, Cr: 0.05-0.5%, Zr: 0.05-0.5%. Or the aluminum alloy excellent in the machinability described in 2.