WO2009151031A1 - α－β TYPE TITANIUM ALLOY - Google Patents
α－β TYPE TITANIUM ALLOY Download PDFInfo
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- WO2009151031A1 WO2009151031A1 PCT/JP2009/060475 JP2009060475W WO2009151031A1 WO 2009151031 A1 WO2009151031 A1 WO 2009151031A1 JP 2009060475 W JP2009060475 W JP 2009060475W WO 2009151031 A1 WO2009151031 A1 WO 2009151031A1
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C14/00—Alloys based on titanium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/16—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of other metals or alloys based thereon
- C22F1/18—High-melting or refractory metals or alloys based thereon
- C22F1/183—High-melting or refractory metals or alloys based thereon of titanium or alloys based thereon
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- the present invention relates to a high-strength ⁇ - ⁇ type titanium alloy having excellent intermittent cutting performance by end milling or milling.
- High strength ⁇ - ⁇ type titanium alloys typified by Ti-6Al-4V are light weight, high strength, high corrosion resistance, and can easily change the strength level by heat treatment. Has been used extensively. In order to make further use of these characteristics, in recent years, automobile parts such as automobile and motorcycle engine members, sports equipment such as golf equipment, civil engineering and building materials, various tools, eyeglass frames and other consumer goods fields, The application of ⁇ - ⁇ type titanium alloys has been expanded to energy development applications.
- the titanium alloy for connecting rods described in Patent Document 1 contains rare earth elements (REM) and Ca, S, Se, Te, Pb, Bi as appropriate, and forms granular compounds to suppress deterioration in toughness and ductility. In addition, the machinability (cutability) is improved.
- REM rare earth elements
- Ca, S, Se, Te, Pb, Bi as appropriate
- the free-cutting titanium alloy described in Patent Document 2 improves machinability (cutability) by containing rare earth elements (REM) and improves hot workability by containing B. .
- the free-cutting titanium alloy described in Patent Document 3 has ductility of the matrix by adding P and S, P and Ni, or P and S and Ni as free-cutting components, and REM in addition to these elements.
- the reduction and the refinement of inclusions are performed to improve the free-cutting property and suppress the reduction of hot workability and fatigue strength.
- ⁇ - ⁇ type titanium alloy described in Patent Document 4 C is positively added, and the strength in the practical temperature range from room temperature to 500 ° C. does not decrease. Furthermore, this ⁇ - ⁇ type titanium alloy improves the hot workability as compared with the Ti-6Al-4V alloy, which is a general-purpose alloy, by reducing the strength in the higher forging temperature range, and in the titanium alloy substrate. The fatigue rate is improved by suppressing the area ratio of TiC to be 3% or less.
- the ⁇ - ⁇ type titanium alloy described in Patent Document 5 positively adds C and controls the ratio [Cr] / [Fe] between the Cr content and the Fe content to control the Fe content relative to the Cr content.
- the solid solubility limit of C is increased, the amount of TiC precipitation is suppressed, and machinability (cutability) and hot workability are improved.
- the ⁇ - ⁇ type titanium alloy described in Patent Document 6 ensures hot workability including forgeability by positive addition of C. Furthermore, this ⁇ - ⁇ type titanium alloy has both excellent machinability (cutability) and hot workability by reducing and refining the amount of TiC precipitates and limiting the upper limit of Cr concentration.
- the present invention has been made in order to solve the above-described conventional problems, and the object thereof is high strength ⁇ - ⁇ type titanium which is excellent in hot workability and excellent in intermittent cutting by end milling or milling. It is to provide an alloy.
- the present invention contains C: 0.06 to 0.13 mass%, Al: 3.0 to 8.5 mass%, V: 5.0 mass% or less, Cr: 3.0 mass% or less, Fe: Less than 2.5% by mass, Mo: 6.0% by mass or less, Ni: 5.0% by mass or less, Nb: 5.0% by mass or less, Ta: 5.0% by mass or less Total
- An ⁇ - ⁇ -type titanium alloy having a value of 0.5% or less and an average equivalent circle diameter of the TiC precipitates of 1 ⁇ m or less.
- the ⁇ - ⁇ type titanium alloy of the present invention preferably contains Si: 1.0% by mass or less.
- the ⁇ - ⁇ type titanium alloy of the present invention preferably contains one or more of Zr: 5.0 mass% or less and Sn: 5.0 mass% or less in total of 7.0 mass% or less.
- the ⁇ - ⁇ type titanium alloy of the present invention has high strength and excellent hot workability, as well as excellent continuous machinability, as well as intermittent cutability by end milling or milling.
- the present inventors have investigated the cause of the decrease in tool life when cutting ⁇ - ⁇ type titanium alloys to which C is added. As a result, it was found that even when the amount of TiC precipitates generated is small, the tool life is reduced when coarse TiC precipitates are present. In particular, it has been found that the effect of tool life reduction due to TiC precipitates is more pronounced during intermittent cutting by end milling or milling than by continuous cutting by a drill.
- the present inventors improved hot workability such as forgeability by positive addition of C, and then reduced the amount of TiC precipitate and refined, We succeeded in obtaining a high-strength ⁇ - ⁇ type titanium alloy with excellent intermittent cutting performance.
- the ⁇ - ⁇ type titanium alloy of the present invention contains C: 0.06 to 0.13 mass%, Al: 3.0 to 8.5 mass%, V: 5.0 mass% or less, Cr: 3.0 mass% or less, Fe: less than 2.5 mass%, Mo: 6.0 mass% or less, Ni: 5.0 mass% or less, Nb: 5.0 mass% or less, Ta: 5.0 mass%
- One or more of the following is contained in a total of 2.0 to 10.0% by mass, and the balance is Ti and inevitable impurities.
- the ⁇ - ⁇ type titanium alloy of the present invention has an average area ratio of TiC precipitates of 0.5% or less in an arbitrary cross section of 0.25 mm 2 or more in the titanium alloy substrate, and the circle of the TiC precipitates. The average equivalent diameter is 1 ⁇ m or less.
- the ⁇ - ⁇ type titanium alloy has an ⁇ phase which is a close hexagonal crystal (hexagonalHclose-packed lattice (HCP)) and a ⁇ phase which is a body-centered cubic crystal (Body-Centered Cubic lattice (BCC)) in the structure. It is a mixed titanium alloy.
- HCP hexagonalHclose-packed lattice
- BCC Body-Centered Cubic lattice
- C 0.06 to 0.13 mass%
- C has the effect of improving strength.
- C is finely precipitated as TiC in the ⁇ temperature range
- the ⁇ phase crystal grains are refined and the hot workability is improved by the refinement. If the C content is less than 0.06% by mass, the action is insufficient. On the other hand, if the C content exceeds 0.13% by mass, coarse TiC having an average equivalent circle diameter of more than 1 ⁇ m and not dissolved in the ⁇ phase at room temperature remains, and the mechanical properties deteriorate. As a result, the intermittent cutting performance is adversely affected.
- the lower limit of the C content is 0.06% by mass, preferably 0.07% by mass, more preferably 0.08% by mass
- the upper limit of the C content is 0.13% by mass, preferably 0%. .12% by mass, more preferably 0.11% by mass.
- Al 3.0 to 8.5% by mass
- Al is an ⁇ -stabilizing element and is an element added to generate an ⁇ -phase. If the Al content is less than 3.0% by mass, ⁇ -phase generation is insufficient, sufficient strength is not exhibited, and a tensile strength (TS) of 900 MPa or more cannot be obtained. On the other hand, if the Al content exceeds 8.5% by mass, the ductility deteriorates and the elongation (EL) decreases to less than 10%. Therefore, the lower limit of the Al content is 3.0% by mass, preferably 3.2% by mass, and the upper limit of the Al content is 8.5% by mass, preferably 8.0% by mass.
- V 5.0 mass% or less, Cr: 3.0 mass% or less, Fe: less than 2.5 mass%, Mo: 6.0 mass% or less, Ni: 5.0 mass% or less, Nb: 5. 1% or more of 0% by mass or less and Ta: 5.0% by mass or less in total 2.0 to 10.0% by mass
- These elements are all ⁇ -stabilizing elements and are elements added to generate a ⁇ -phase. If the total content of these elements is less than 2.0% by mass, the amount of ⁇ -phase produced is too small. Therefore, the total content of these elements is 2.0% by mass or more, preferably 3.0% by mass or more. These elements also have the effect of improving the strength.
- the elongation (EL) deteriorates. To do. In particular, when the Fe content is excessive, the decrease in elongation (EL) becomes significant. Moreover, when there is too much content of Cr, machinability will fall. Therefore, the upper limit of the content of these elements is defined as described above, and the upper limit of the total content of these elements is 10.0% by mass.
- the ⁇ - ⁇ type titanium alloy of the present invention is composed of Ti and unavoidable impurities in addition to the above elements, but may contain the following elements alone or in combination.
- Si 1.0% by mass or less
- the ratio of Cr content to Fe content [Cr] / [Fe] is preferably 3.0 or less.
- both Cr and Fe are ⁇ -stabilizing elements, but Fe has an effect of expanding the solid solubility limit of C as compared with Cr. If the ratio [Cr] / [Fe] of the Cr content to the Fe content exceeds 3.0, the effect of expanding the C solid solubility limit by Fe is lost, and the effect of suppressing the precipitation of TiC cannot be exhibited. Therefore, when Fe is contained, the upper limit of the Cr content to Fe content ratio [Cr] / [Fe] is 3.0, preferably 2.5.
- the titanium alloy of the present invention is an ⁇ - ⁇ type titanium alloy whose structure is composed of an ⁇ phase and a ⁇ phase at room temperature.
- TiC precipitates in the structure of the ⁇ - ⁇ type titanium alloy, that is, in the titanium alloy substrate, but the average value of the area ratio of TiC precipitates in an arbitrary cross section of 0.25 mm 2 or more in the titanium alloy substrate. Is 0.5% or less.
- the average equivalent circle diameter of the TiC precipitates is 1 ⁇ m or less.
- the upper limit of the average value of the area ratio of TiC precipitates in an arbitrary cross section of 0.25 mm 2 or more in the titanium alloy substrate is 0.5%, preferably 0.25%.
- the upper limit of the average circle equivalent diameter of the TiC precipitates is 1 ⁇ m, preferably 0.8 ⁇ m.
- the thickness of 0.25 mm 2 or more in the titanium alloy substrate is increased.
- the average value of the area ratio of the TiC precipitates in an arbitrary cross section can be 0.5% or less, and the average value of the equivalent circle diameter of the TiC precipitates can be 1 ⁇ m or less.
- ingots of titanium alloys having the component compositions shown in Table 1 were cast by the CCIM method (Cold Crucible Induction Melting). These ingots have a cylindrical shape with a diameter of 150 mm and a height of 150 mm.
- Hot forging was performed under the following production conditions. Hot forging was performed by heating the ingot at 1200 ° C., forging at a forging ratio of about 1.5, cooling to water, heating to 900 ° C., and forging at a forging ratio of about 3.2 or more. By this hot forging, a titanium alloy plate having a long plate shape with a cross section of 20 mm in thickness and 190 mm in width was obtained. Next, after air-cooling to room temperature, the final titanium alloy plate used for a test was obtained by annealing at 800 degreeC for 2 hours. From this titanium alloy plate, a structure observation test piece, an end mill cutting test piece, and a tensile test piece were sampled and subjected to the following tests.
- the tissue observation test piece is collected from a portion excluding the thickness of 2 mm from the front and back surfaces of the titanium alloy plate and the thickness of 50 mm from the side surface.
- This test piece was embedded in a synthetic resin holder, polished so that the test piece was exposed, and further buffed.
- the surface of the polished specimen is photographed at a magnification of 400 times. This photography is performed with four fields of view, and the total observation area is 0.25 mm 2 . From the image data thus obtained, image analysis software (Nano Hunter NS2K-Lt, manufactured by Nanosystem Co., Ltd.) was used to determine the area ratio of TiC precipitates and the equivalent circle diameter of each photograph.
- ⁇ Room temperature tensile test> A tensile test piece was collected from the titanium alloy plate described above. The tensile test was performed in accordance with ASTM standard E8. The shape and dimensions of the tensile test piece are shown in FIG. The test temperature is room temperature (25 ° C.), and the strain rate is 100 / sec. From the test results, those having a tensile strength (TS) of 900 MPa or more and an elongation (EL) of 10% or more were accepted and judged to be a high-strength titanium alloy. Table 2 shows the tensile strength (TS) and elongation (EL) of each sample obtained in this test.
- TS tensile strength
- EL elongation
- Sample No. in Table 2 Is the sample No. described in Table 1. Is consistent with Sample No. 4 and no. Examples 6 to 11 are invention examples, and the component composition shown in Table 1, the average area ratio of TiC precipitates and the average equivalent circle diameter shown in Table 2 both satisfy the conditions of the present invention. All others are comparative examples.
- sample no. 4 and no. 6 to 11 can be judged to be high-strength titanium alloys having excellent intermittent machinability.
- the amount of tool wear determined by the intermittent cutting test could not be satisfied with at least one of the tensile strength (TS) and elongation (EL) determined in the room temperature tensile test. That is, sample no. 1-3, no. 5 and no. 12 to 19 cannot be judged to be high-strength titanium alloys having excellent intermittent machinability.
Abstract
Provided is a high-strength α-β type titanium alloy having excellent hot working properties and excellent cutting properties with end-mill and milling operations. The titanium alloy contains 0.06 to 0.13 mass% C and 3.0 to 8.5 mass% Al as well as 2.0 to 10.0 mass% in total of one or more of not more than 5.0 mass% V, not more than 3.0 mass% Cr, less than 2.5 mass% Fe, not more than 6.0 mass% Mo, not more than 5.0 mass% Ni, not more than 5.0 mass% Nb and not more than 5.0 mass% Ta, with the balance comprising Ti and unavoidable impurities. The average value of the area ratio of TiC precipitate in the titanium alloy base material is not more than 0.5% and the average value of the round phase diameter of the TiC precipitate is not more than 1 μm.
Description
本発明は、エンドミルやフライス加工などによる断続切削性に優れた、高強度のα－β型チタン合金に関するものである。
The present invention relates to a high-strength α-β type titanium alloy having excellent intermittent cutting performance by end milling or milling.
Ｔｉ－６Ａｌ－４Ｖに代表される高強度α－β型チタン合金は、軽量、高強度、高耐食性であることに加え、熱処理によって容易に強度レベルを変化させることができることから、従来から航空機産業を中心に多用されてきた。これらの特性を更に活用すべく、近年では、自動車や二輪車のエンジン部材といった自動車部品、ゴルフ用品をはじめとしたスポーツ用品、土木建築用素材、各種工具類、眼鏡フレームなどの民生品分野や、深海やエネルギー開発用途などへ、α－β型チタン合金の適用が拡大されている。
High strength α-β type titanium alloys typified by Ti-6Al-4V are light weight, high strength, high corrosion resistance, and can easily change the strength level by heat treatment. Has been used extensively. In order to make further use of these characteristics, in recent years, automobile parts such as automobile and motorcycle engine members, sports equipment such as golf equipment, civil engineering and building materials, various tools, eyeglass frames and other consumer goods fields, The application of α-β type titanium alloys has been expanded to energy development applications.
しかしながら、α－β型チタン合金の製造コストは著しく高く、また加工性、特に切削加工性が悪いため、現状では、α－β型チタン合金の適用拡大は妨げられ、使用範囲が限定されている。このような実情に鑑み、近年、切削加工性を改善したチタン合金について、種々の提案がなされている。
However, the production cost of α-β type titanium alloys is remarkably high, and the workability, particularly the machinability, is poor, so at present, the expansion of application of α-β type titanium alloys is hindered and the range of use is limited. . In recent years, various proposals have been made for titanium alloys with improved machinability.
特許文献１に記載のコンロッド用チタン合金は、希土類元素（ＲＥＭ）とＣａ、Ｓ、Ｓｅ、Ｔｅ、Ｐｂ、Ｂｉを適宜含有し、粒状の化合物を形成することにより、靭性、延性の低下を抑制すると共に被削性（切削性）を向上している。
The titanium alloy for connecting rods described in Patent Document 1 contains rare earth elements (REM) and Ca, S, Se, Te, Pb, Bi as appropriate, and forms granular compounds to suppress deterioration in toughness and ductility. In addition, the machinability (cutability) is improved.
また、特許文献２に記載の快削チタン合金は、希土類元素（ＲＥＭ）を含有することにより被削性（切削性）を向上し、Ｂを含有することにより熱間加工性を改善している。
Moreover, the free-cutting titanium alloy described in Patent Document 2 improves machinability (cutability) by containing rare earth elements (REM) and improves hot workability by containing B. .
また、特許文献３に記載の快削チタン合金は、快削成分として、ＰおよびＳ、ＰおよびＮｉ、またはＰとＳおよびＮｉ、更にはこれら元素に加えてＲＥＭを添加することによりマトリックスの延性低下と介在物の微細化を行い、快削性を改善すると共に熱間加工性や疲労強度の低下を抑制している。
In addition, the free-cutting titanium alloy described in Patent Document 3 has ductility of the matrix by adding P and S, P and Ni, or P and S and Ni as free-cutting components, and REM in addition to these elements. The reduction and the refinement of inclusions are performed to improve the free-cutting property and suppress the reduction of hot workability and fatigue strength.
また、特許文献４に記載のα－β型チタン合金は、Ｃが積極添加されており、常温から５００℃までの実用温度域での強度が低下しない。さらに、このα－β型チタン合金は、より高温の鍛造温度域での強度を低下させることによって汎用合金であるＴｉ－６Ａｌ－４Ｖ合金より熱間加工性を向上させると共に、チタン合金素地中に析出するＴｉＣの面積率を３％以下に抑制して疲労特性を改善している。
Also, in the α-β type titanium alloy described in Patent Document 4, C is positively added, and the strength in the practical temperature range from room temperature to 500 ° C. does not decrease. Furthermore, this α-β type titanium alloy improves the hot workability as compared with the Ti-6Al-4V alloy, which is a general-purpose alloy, by reducing the strength in the higher forging temperature range, and in the titanium alloy substrate. The fatigue rate is improved by suppressing the area ratio of TiC to be 3% or less.
また、特許文献５に記載のα－β型チタン合金は、Ｃを積極添加すると共に、Ｃｒ含有量とＦｅ含有量との比［Ｃｒ］／［Ｆｅ］をコントロールしてＣｒ量に対するＦｅ量を増やすことにより、Ｃの固溶限を増大させてＴｉＣ析出量を抑制し、被削性（切削性）および熱間加工性を改善している。
In addition, the α-β type titanium alloy described in Patent Document 5 positively adds C and controls the ratio [Cr] / [Fe] between the Cr content and the Fe content to control the Fe content relative to the Cr content. By increasing, the solid solubility limit of C is increased, the amount of TiC precipitation is suppressed, and machinability (cutability) and hot workability are improved.
また、特許文献６に記載のα－β型チタン合金は、Ｃの積極添加によって鍛造性を含む熱間加工性を確保する。さらに、このα－β型チタン合金は、ＴｉＣ析出物量を低減、微細化し、Ｃｒ濃度の上限を制限することによって、優れた被削性（切削性）と熱間加工性とを兼備する。
Also, the α-β type titanium alloy described in Patent Document 6 ensures hot workability including forgeability by positive addition of C. Furthermore, this α-β type titanium alloy has both excellent machinability (cutability) and hot workability by reducing and refining the amount of TiC precipitates and limiting the upper limit of Cr concentration.
これらの特許文献には、被削性（切削性）を改善させた効果が記載されている。しかしながら、これらの特許文献に記載された技術、特に特許文献５及び特許文献６に記載された技術は、ドリルでの連続切削性を対象としており、エンドミルやフライス加工などによる断続切削性の検討はなされていない。鍛造性などの熱間加工性を改善するためにＣを積極添加するとＴｉＣが析出するが、ＴｉＣは断続切削性に対して特に顕著に影響するため、連続切削性だけではなく断続切削性に優れた高強度α－β型チタン合金が開発されることが望まれていた。
These patent documents describe the effect of improving machinability (cutability). However, the techniques described in these patent documents, especially the techniques described in Patent Document 5 and Patent Document 6, are intended for continuous machinability with a drill, and examination of intermittent machinability by an end mill or milling is not possible. Not done. When C is positively added to improve hot workability such as forgeability, TiC precipitates, but since TiC has a particularly significant effect on interrupted machinability, it is excellent not only in continuous machinability but also in intermittent machinability. It has been desired to develop a high-strength α-β type titanium alloy.
本発明は、上記従来の問題を解決するためになされたものであり、その目的は、熱間加工性に優れると共に、エンドミルやフライス加工などによる断続切削性に優れた高強度α－β型チタン合金を提供することである。
The present invention has been made in order to solve the above-described conventional problems, and the object thereof is high strength α-β type titanium which is excellent in hot workability and excellent in intermittent cutting by end milling or milling. It is to provide an alloy.
本発明は、Ｃ：０．０６～０．１３質量％、Ａｌ：３．０～８．５質量％を含有すると共に、Ｖ：５．０質量％以下、Ｃｒ：３．０質量％以下、Ｆｅ：２．５質量％未満、Ｍｏ：６．０質量％以下、Ｎｉ：５．０質量％以下、Ｎｂ：５．０質量％以下、Ｔａ：５．０質量％以下の１種以上を合計で２．０～１０．０質量％含有し、残部がＴｉおよび不可避的不純物であるチタン合金であって、チタン合金素地中の０．２５ｍｍ２以上の任意断面におけるＴｉＣ析出物の面積率の平均値が０．５％以下であり、前記ＴｉＣ析出物の円相当径の平均値が１μｍ以下であることを特徴とするα－β型チタン合金である。
The present invention contains C: 0.06 to 0.13 mass%, Al: 3.0 to 8.5 mass%, V: 5.0 mass% or less, Cr: 3.0 mass% or less, Fe: Less than 2.5% by mass, Mo: 6.0% by mass or less, Ni: 5.0% by mass or less, Nb: 5.0% by mass or less, Ta: 5.0% by mass or less Total The average of the area ratio of TiC precipitates in an arbitrary cross section of 0.25 mm 2 or more in the titanium alloy substrate, with the balance being 2.0 to 10.0% by mass and the balance being Ti and unavoidable impurities An α-β-type titanium alloy having a value of 0.5% or less and an average equivalent circle diameter of the TiC precipitates of 1 μm or less.
本発明のα－β型チタン合金は、Ｓｉ：１．０質量％以下を含有すると好ましい。
The α-β type titanium alloy of the present invention preferably contains Si: 1.0% by mass or less.
本発明のα－β型チタン合金は、Ｚｒ：５．０質量％以下、Ｓｎ：５．０質量％以下の１種以上を合計で７．０質量％以下含有すると好ましい。
The α-β type titanium alloy of the present invention preferably contains one or more of Zr: 5.0 mass% or less and Sn: 5.0 mass% or less in total of 7.0 mass% or less.
本発明のα－β型チタン合金は、高強度で熱間加工性に優れるうえに、連続切削性に優れるのはもちろん、エンドミルやフライス加工などによる断続切削性にも優れている。
The α-β type titanium alloy of the present invention has high strength and excellent hot workability, as well as excellent continuous machinability, as well as intermittent cutability by end milling or milling.
本発明者らは、Ｃを添加したα－β型チタン合金の切削時に工具寿命が低下する原因を追究した。その結果、ＴｉＣ析出物の生成量が少ない場合であっても、粗大なＴｉＣ析出物が存在した場合には、工具寿命が低下することを見出した。特に、ドリルによる連続切削時より、エンドミルやフライス加工などによる断続切削時の方が、ＴｉＣ析出物を原因とする工具寿命の低下の影響がより顕著であることが分かった。
The present inventors have investigated the cause of the decrease in tool life when cutting α-β type titanium alloys to which C is added. As a result, it was found that even when the amount of TiC precipitates generated is small, the tool life is reduced when coarse TiC precipitates are present. In particular, it has been found that the effect of tool life reduction due to TiC precipitates is more pronounced during intermittent cutting by end milling or milling than by continuous cutting by a drill.
本発明者らは、これらを前提に実験、研究を重ねた結果、Ｃの積極添加により鍛造性などの熱間加工性を改善したうえで、ＴｉＣ析出物量を低減すると共に微細化することにより、断続切削性に優れた高強度α－β型チタン合金を得ることに成功した。
As a result of repeated experiments and research on the premise of these, the present inventors improved hot workability such as forgeability by positive addition of C, and then reduced the amount of TiC precipitate and refined, We succeeded in obtaining a high-strength α-β type titanium alloy with excellent intermittent cutting performance.
以下、本発明を実施形態に基づいて更に詳細に説明する。
Hereinafter, the present invention will be described in more detail based on embodiments.
本発明のα－β型チタン合金は、Ｃ：０．０６～０．１３質量％、Ａｌ：３．０～８．５質量％を含有すると共に、Ｖ：５．０質量％以下、Ｃｒ：３．０質量％以下、Ｆｅ：２．５質量％未満、Ｍｏ：６．０質量％以下、Ｎｉ：５．０質量％以下、Ｎｂ：５．０質量％以下、Ｔａ：５．０質量％以下の１種以上を合計で２．０～１０．０質量％含有し、残部がＴｉおよび不可避的不純物である。さらに本発明のα－β型チタン合金は、チタン合金素地中の０．２５ｍｍ２以上の任意断面におけるＴｉＣ析出物の面積率の平均値が０．５％以下であり、そのＴｉＣ析出物の円相当径の平均値が１μｍ以下である。
The α-β type titanium alloy of the present invention contains C: 0.06 to 0.13 mass%, Al: 3.0 to 8.5 mass%, V: 5.0 mass% or less, Cr: 3.0 mass% or less, Fe: less than 2.5 mass%, Mo: 6.0 mass% or less, Ni: 5.0 mass% or less, Nb: 5.0 mass% or less, Ta: 5.0 mass% One or more of the following is contained in a total of 2.0 to 10.0% by mass, and the balance is Ti and inevitable impurities. Furthermore, the α-β type titanium alloy of the present invention has an average area ratio of TiC precipitates of 0.5% or less in an arbitrary cross section of 0.25 mm 2 or more in the titanium alloy substrate, and the circle of the TiC precipitates. The average equivalent diameter is 1 μm or less.
尚、α－β型チタン合金は、稠密六方晶（hexagonal close-packed lattice（ＨＣＰ））であるα相と体心立方晶（Body-Centered Cubic lattice（ＢＣＣ））であるβ相が組織中に混在するチタン合金である。
The α-β type titanium alloy has an α phase which is a close hexagonal crystal (hexagonalＨclose-packed lattice (HCP)) and a β phase which is a body-centered cubic crystal (Body-Centered Cubic lattice (BCC)) in the structure. It is a mixed titanium alloy.
まず、本発明のα－β型チタン合金の成分組成について説明する。
First, the component composition of the α-β type titanium alloy of the present invention will be described.
（Ｃ：０．０６～０．１３質量％）
Ｃは強度を向上させるという作用を有する。また、Ｃはβ温度域でＴｉＣとして微細析出するため、β相結晶粒を微細化し、その微細化によって熱間加工性を向上させるという作用も有する。Ｃの含有量が０．０６質量％未満であるとその作用が不足する。一方、Ｃの含有量が０．１３質量％を超えると、平均円相当径が１μｍ超の、室温でα相中に固溶されない粗大なＴｉＣが残留するようになり、機械的特性が劣化して断続切削性に悪影響を及ぼすようになる。従って、Ｃの含有量の下限は０．０６質量％、好ましくは０.０７質量％、更に好ましくは０．０８質量％であり、Ｃの含有量の上限は０．１３質量％、好ましくは０．１２質量％、更に好ましくは０．１１質量％である。 (C: 0.06 to 0.13 mass%)
C has the effect of improving strength. In addition, since C is finely precipitated as TiC in the β temperature range, the β phase crystal grains are refined and the hot workability is improved by the refinement. If the C content is less than 0.06% by mass, the action is insufficient. On the other hand, if the C content exceeds 0.13% by mass, coarse TiC having an average equivalent circle diameter of more than 1 μm and not dissolved in the α phase at room temperature remains, and the mechanical properties deteriorate. As a result, the intermittent cutting performance is adversely affected. Therefore, the lower limit of the C content is 0.06% by mass, preferably 0.07% by mass, more preferably 0.08% by mass, and the upper limit of the C content is 0.13% by mass, preferably 0%. .12% by mass, more preferably 0.11% by mass.
Ｃは強度を向上させるという作用を有する。また、Ｃはβ温度域でＴｉＣとして微細析出するため、β相結晶粒を微細化し、その微細化によって熱間加工性を向上させるという作用も有する。Ｃの含有量が０．０６質量％未満であるとその作用が不足する。一方、Ｃの含有量が０．１３質量％を超えると、平均円相当径が１μｍ超の、室温でα相中に固溶されない粗大なＴｉＣが残留するようになり、機械的特性が劣化して断続切削性に悪影響を及ぼすようになる。従って、Ｃの含有量の下限は０．０６質量％、好ましくは０.０７質量％、更に好ましくは０．０８質量％であり、Ｃの含有量の上限は０．１３質量％、好ましくは０．１２質量％、更に好ましくは０．１１質量％である。 (C: 0.06 to 0.13 mass%)
C has the effect of improving strength. In addition, since C is finely precipitated as TiC in the β temperature range, the β phase crystal grains are refined and the hot workability is improved by the refinement. If the C content is less than 0.06% by mass, the action is insufficient. On the other hand, if the C content exceeds 0.13% by mass, coarse TiC having an average equivalent circle diameter of more than 1 μm and not dissolved in the α phase at room temperature remains, and the mechanical properties deteriorate. As a result, the intermittent cutting performance is adversely affected. Therefore, the lower limit of the C content is 0.06% by mass, preferably 0.07% by mass, more preferably 0.08% by mass, and the upper limit of the C content is 0.13% by mass, preferably 0%. .12% by mass, more preferably 0.11% by mass.
（Ａｌ：３．０～８．５質量％）
Ａｌは、α安定化元素であり、α相を生成するために添加される元素である。Ａｌの含有量が３．０質量％未満であればα相の生成が過少になり、また、十分な強度が発現せず、９００ＭＰａ以上の引張強度（ＴＳ）が得られないようになる。一方、Ａｌの含有量が８．５質量％を超えて過多になると、延性が劣化し、伸び（ＥＬ）が１０％未満に低下する。従って、Ａｌの含有量の下限は３．０質量％、好ましくは３．２質量％であり、Ａｌの含有量の上限は８．５質量％、好ましくは８．０質量％である。 (Al: 3.0 to 8.5% by mass)
Al is an α-stabilizing element and is an element added to generate an α-phase. If the Al content is less than 3.0% by mass, α-phase generation is insufficient, sufficient strength is not exhibited, and a tensile strength (TS) of 900 MPa or more cannot be obtained. On the other hand, if the Al content exceeds 8.5% by mass, the ductility deteriorates and the elongation (EL) decreases to less than 10%. Therefore, the lower limit of the Al content is 3.0% by mass, preferably 3.2% by mass, and the upper limit of the Al content is 8.5% by mass, preferably 8.0% by mass.
Ａｌは、α安定化元素であり、α相を生成するために添加される元素である。Ａｌの含有量が３．０質量％未満であればα相の生成が過少になり、また、十分な強度が発現せず、９００ＭＰａ以上の引張強度（ＴＳ）が得られないようになる。一方、Ａｌの含有量が８．５質量％を超えて過多になると、延性が劣化し、伸び（ＥＬ）が１０％未満に低下する。従って、Ａｌの含有量の下限は３．０質量％、好ましくは３．２質量％であり、Ａｌの含有量の上限は８．５質量％、好ましくは８．０質量％である。 (Al: 3.0 to 8.5% by mass)
Al is an α-stabilizing element and is an element added to generate an α-phase. If the Al content is less than 3.0% by mass, α-phase generation is insufficient, sufficient strength is not exhibited, and a tensile strength (TS) of 900 MPa or more cannot be obtained. On the other hand, if the Al content exceeds 8.5% by mass, the ductility deteriorates and the elongation (EL) decreases to less than 10%. Therefore, the lower limit of the Al content is 3.0% by mass, preferably 3.2% by mass, and the upper limit of the Al content is 8.5% by mass, preferably 8.0% by mass.
（Ｖ：５．０質量％以下、Ｃｒ：３．０質量％以下、Ｆｅ：２．５質量％未満、Ｍｏ：６．０質量％以下、Ｎｉ：５．０質量％以下、Ｎｂ：５．０質量％以下、Ｔａ：５．０質量％以下の１種以上を合計で２．０～１０．０質量％）
これらの元素は全てβ安定化元素であり、β相を生成するために添加される元素である。これらの元素の含有量の合計が２．０質量％未満であれば、β相の生成量が過少になる。従って、これらの元素の含有量の合計は、２．０質量％以上、好ましくは３．０質量％以上であると好ましい。これらの元素も強度を向上させる作用を有するが、それぞれの元素の含有量が上限を超えると、またはそれぞれの元素の含有量の合計が１０．０質量％を超えると、伸び（ＥＬ）が劣化する。特に、Ｆｅの含有量が過多になると、伸び（ＥＬ）の低下が顕著になる。また、Ｃｒの含有量が過多になると、被削性が低下する。従って、これらの元素の含有量の上限はそれぞれ上記のように規定し、これらの元素の含有量の合計の上限は１０．０質量％である。 (V: 5.0 mass% or less, Cr: 3.0 mass% or less, Fe: less than 2.5 mass%, Mo: 6.0 mass% or less, Ni: 5.0 mass% or less, Nb: 5. 1% or more of 0% by mass or less and Ta: 5.0% by mass or less in total 2.0 to 10.0% by mass)
These elements are all β-stabilizing elements and are elements added to generate a β-phase. If the total content of these elements is less than 2.0% by mass, the amount of β-phase produced is too small. Therefore, the total content of these elements is 2.0% by mass or more, preferably 3.0% by mass or more. These elements also have the effect of improving the strength. However, when the content of each element exceeds the upper limit or the total content of each element exceeds 10.0% by mass, the elongation (EL) deteriorates. To do. In particular, when the Fe content is excessive, the decrease in elongation (EL) becomes significant. Moreover, when there is too much content of Cr, machinability will fall. Therefore, the upper limit of the content of these elements is defined as described above, and the upper limit of the total content of these elements is 10.0% by mass.
これらの元素は全てβ安定化元素であり、β相を生成するために添加される元素である。これらの元素の含有量の合計が２．０質量％未満であれば、β相の生成量が過少になる。従って、これらの元素の含有量の合計は、２．０質量％以上、好ましくは３．０質量％以上であると好ましい。これらの元素も強度を向上させる作用を有するが、それぞれの元素の含有量が上限を超えると、またはそれぞれの元素の含有量の合計が１０．０質量％を超えると、伸び（ＥＬ）が劣化する。特に、Ｆｅの含有量が過多になると、伸び（ＥＬ）の低下が顕著になる。また、Ｃｒの含有量が過多になると、被削性が低下する。従って、これらの元素の含有量の上限はそれぞれ上記のように規定し、これらの元素の含有量の合計の上限は１０．０質量％である。 (V: 5.0 mass% or less, Cr: 3.0 mass% or less, Fe: less than 2.5 mass%, Mo: 6.0 mass% or less, Ni: 5.0 mass% or less, Nb: 5. 1% or more of 0% by mass or less and Ta: 5.0% by mass or less in total 2.0 to 10.0% by mass)
These elements are all β-stabilizing elements and are elements added to generate a β-phase. If the total content of these elements is less than 2.0% by mass, the amount of β-phase produced is too small. Therefore, the total content of these elements is 2.0% by mass or more, preferably 3.0% by mass or more. These elements also have the effect of improving the strength. However, when the content of each element exceeds the upper limit or the total content of each element exceeds 10.0% by mass, the elongation (EL) deteriorates. To do. In particular, when the Fe content is excessive, the decrease in elongation (EL) becomes significant. Moreover, when there is too much content of Cr, machinability will fall. Therefore, the upper limit of the content of these elements is defined as described above, and the upper limit of the total content of these elements is 10.0% by mass.
本発明のα－β型チタン合金は、以上の元素のほか、Ｔｉと不可避的不純物により構成されるが、以下の元素を単独で、或いは複合して含有しても良い。
The α-β type titanium alloy of the present invention is composed of Ti and unavoidable impurities in addition to the above elements, but may contain the following elements alone or in combination.
（Ｓｉ：１．０質量％以下）
Ｓｉを添加すると更に強度が向上するが、１．０質量％を超えてＳｉを添加すると、延性が劣化して必要な伸び（ＥＬ）が得られなくなる。従って、Ｓｉを添加する場合、その含有量の上限は１．０質量％である。 (Si: 1.0% by mass or less)
When Si is added, the strength is further improved. However, when Si is added in excess of 1.0 mass%, the ductility deteriorates and the required elongation (EL) cannot be obtained. Therefore, when adding Si, the upper limit of the content is 1.0 mass%.
Ｓｉを添加すると更に強度が向上するが、１．０質量％を超えてＳｉを添加すると、延性が劣化して必要な伸び（ＥＬ）が得られなくなる。従って、Ｓｉを添加する場合、その含有量の上限は１．０質量％である。 (Si: 1.0% by mass or less)
When Si is added, the strength is further improved. However, when Si is added in excess of 1.0 mass%, the ductility deteriorates and the required elongation (EL) cannot be obtained. Therefore, when adding Si, the upper limit of the content is 1.0 mass%.
（Ｚｒ：５．０質量％以下、Ｓｎ：５．０質量％以下の１種以上を合計で７．０質量％以下）
ＺｒやＳｎを添加することでも更に強度が向上するが、Ｚｒ、Ｓｎをそれぞれ単独で５．０質量％を超えて、または合計で７．０質量％を超えて添加すると、延性が劣化し、必要な伸び（ＥＬ）が得られなくなる。従って、ＺｒやＳｎを添加する場合、Ｚｒの含有量、Ｓｎの含有量は、それぞれ単独で５．０質量％以下、合計で７．０質量％以下である。 (Zr: 5.0% by mass or less, Sn: 5.0% by mass or less, total of 7.0% by mass or less)
The strength is further improved by adding Zr or Sn. However, when Zr and Sn are added individually in excess of 5.0% by mass or in total exceeding 7.0% by mass, ductility deteriorates, The required elongation (EL) cannot be obtained. Therefore, when adding Zr or Sn, the content of Zr and the content of Sn are 5.0% by mass or less each independently, and 7.0% by mass or less in total.
ＺｒやＳｎを添加することでも更に強度が向上するが、Ｚｒ、Ｓｎをそれぞれ単独で５．０質量％を超えて、または合計で７．０質量％を超えて添加すると、延性が劣化し、必要な伸び（ＥＬ）が得られなくなる。従って、ＺｒやＳｎを添加する場合、Ｚｒの含有量、Ｓｎの含有量は、それぞれ単独で５．０質量％以下、合計で７．０質量％以下である。 (Zr: 5.0% by mass or less, Sn: 5.0% by mass or less, total of 7.0% by mass or less)
The strength is further improved by adding Zr or Sn. However, when Zr and Sn are added individually in excess of 5.0% by mass or in total exceeding 7.0% by mass, ductility deteriorates, The required elongation (EL) cannot be obtained. Therefore, when adding Zr or Sn, the content of Zr and the content of Sn are 5.0% by mass or less each independently, and 7.0% by mass or less in total.
以上の化学成分において、Ｃｒ含有量とＦｅ含有量の比［Ｃｒ］／［Ｆｅ］は、３．０以下であると好ましい。前記したように、ＣｒとＦｅは共にβ安定化元素であるが、Ｃｒに比してＦｅはＣの固溶限を拡大する作用を有する。Ｃｒ含有量とＦｅ含有量の比［Ｃｒ］／［Ｆｅ］が３．０を超えると、ＦｅによるＣの固溶限の拡大作用が失われ、ＴｉＣの析出の抑制効果が発揮できなくなる。従って、Ｆｅを含有する場合、Ｃｒ含有量とＦｅ含有量の比［Ｃｒ］／［Ｆｅ］の上限は３．０、好ましくは２．５である。
In the above chemical components, the ratio of Cr content to Fe content [Cr] / [Fe] is preferably 3.0 or less. As described above, both Cr and Fe are β-stabilizing elements, but Fe has an effect of expanding the solid solubility limit of C as compared with Cr. If the ratio [Cr] / [Fe] of the Cr content to the Fe content exceeds 3.0, the effect of expanding the C solid solubility limit by Fe is lost, and the effect of suppressing the precipitation of TiC cannot be exhibited. Therefore, when Fe is contained, the upper limit of the Cr content to Fe content ratio [Cr] / [Fe] is 3.0, preferably 2.5.
本発明のチタン合金は、室温においてその組織がα相とβ相よりなるα－β型チタン合金である。Ｃの添加により、α－β型チタン合金の組織中、すなわちチタン合金素地中にＴｉＣが析出するが、チタン合金素地中の０．２５ｍｍ２以上の任意断面におけるＴｉＣ析出物の面積率の平均値は０．５％以下である。ＴｉＣ析出物が存在する場合、ＴｉＣ析出物の円相当径の平均値は１μｍ以下である。
The titanium alloy of the present invention is an α-β type titanium alloy whose structure is composed of an α phase and a β phase at room temperature. By adding C, TiC precipitates in the structure of the α-β type titanium alloy, that is, in the titanium alloy substrate, but the average value of the area ratio of TiC precipitates in an arbitrary cross section of 0.25 mm 2 or more in the titanium alloy substrate. Is 0.5% or less. When TiC precipitates are present, the average equivalent circle diameter of the TiC precipitates is 1 μm or less.
Ｃの添加によりＴｉＣが生成し、このＴｉＣを核として組織がα相に変態し、結果的にα－β組織が微細化することにより、鍛造性をはじめとする熱間加工性が向上する。一方、ＴｉＣは被削性（切削性）に大きな影響を及ぼし、ＴｉＣの析出量が多い場合やＴｉＣ析出物のサイズが大きい場合には、工具磨耗が著しく促進される。特に、エンドミルやフライス加工などによる断続切削性への影響は大きくなる。従って、チタン合金素地中の０．２５ｍｍ２以上の任意断面におけるＴｉＣ析出物の面積率の平均値の上限は０．５％、好ましくは０．２５％である。ＴｉＣ析出物が存在する場合、そのＴｉＣ析出物の円相当径の平均値の上限は１μｍ、好ましくは０．８μｍである。
By adding C, TiC is generated, and the structure is transformed into an α phase using this TiC as a nucleus. As a result, the α-β structure is refined, so that hot workability including forgeability is improved. On the other hand, TiC has a great influence on machinability (cutability), and when the amount of TiC deposited is large or the size of TiC precipitate is large, tool wear is remarkably promoted. In particular, the influence on interrupted cutting performance by end milling or milling becomes large. Therefore, the upper limit of the average value of the area ratio of TiC precipitates in an arbitrary cross section of 0.25 mm 2 or more in the titanium alloy substrate is 0.5%, preferably 0.25%. When TiC precipitates are present, the upper limit of the average circle equivalent diameter of the TiC precipitates is 1 μm, preferably 0.8 μm.
上記した成分組成のα－β型チタン合金を、以下の実施例に例示するような製造条件により圧延や鍛造などの熱間加工工程で加工すれば、チタン合金素地中の０．２５ｍｍ２以上の任意断面におけるＴｉＣ析出物の面積率の平均値を０．５％以下、そのＴｉＣ析出物の円相当径の平均値を１μｍ以下とすることができる。
If the α-β type titanium alloy having the above-described composition is processed in a hot working process such as rolling or forging under the production conditions exemplified in the following examples, the thickness of 0.25 mm 2 or more in the titanium alloy substrate is increased. The average value of the area ratio of the TiC precipitates in an arbitrary cross section can be 0.5% or less, and the average value of the equivalent circle diameter of the TiC precipitates can be 1 μm or less.
以下実施例を挙げて本発明をより具体的に説明するが、本発明はもとより下記実施例によって制限を受けるものではない。本発明の趣旨に適合し得る範囲で適宜変更を加えて実施することも可能であり、それらは何れも本発明の技術的範囲に含まれる。
Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples. The present invention can be implemented with appropriate modifications within a range that can be adapted to the gist of the present invention, and they are all included in the technical scope of the present invention.
本実施例では、まず、ＣＣＩＭ法（コールドクルーシブル誘導溶解法（Cold Crucible Induction Melting））による溶解によって、表１に示す成分組成のチタン合金の約２０ｋｇの鋳塊をそれぞれ鋳造した。これらの鋳塊の形状は、直径１５０ｍｍ×高さ１５０ｍｍの円柱状である。
In this example, first, about 20 kg of ingots of titanium alloys having the component compositions shown in Table 1 were cast by the CCIM method (Cold Crucible Induction Melting). These ingots have a cylindrical shape with a diameter of 150 mm and a height of 150 mm.
この鋳塊を用いて、以下に示す製造条件で熱間鍛造を行った。熱間鍛造は、鋳塊を１２００℃で加熱した後、鍛錬比約１．５で鍛造し、水冷した後に９００℃まで加熱して、鍛錬比約３．２以上で鍛造することで実施した。この熱間鍛造により、厚さ２０ｍｍ×幅１９０ｍｍの、断面形状が長尺板状であるチタン合金板が得られた。次に室温まで空冷した後に８００℃で２時間の焼鈍を行うことにより、試験に用いる最終的なチタン合金板が得られた。このチタン合金板から組織観察試験片、エンドミル切削試験片、並びに引張試験片を採取し、以下に示す各試験を実施した。
Using this ingot, hot forging was performed under the following production conditions. Hot forging was performed by heating the ingot at 1200 ° C., forging at a forging ratio of about 1.5, cooling to water, heating to 900 ° C., and forging at a forging ratio of about 3.2 or more. By this hot forging, a titanium alloy plate having a long plate shape with a cross section of 20 mm in thickness and 190 mm in width was obtained. Next, after air-cooling to room temperature, the final titanium alloy plate used for a test was obtained by annealing at 800 degreeC for 2 hours. From this titanium alloy plate, a structure observation test piece, an end mill cutting test piece, and a tensile test piece were sampled and subjected to the following tests.
＜組織観察試験＞
組織観察では、ＴｉＣ析出物の面積率の平均値、及びＴｉＣ析出物の円相当径の平均値を、以下の手順により求めた。 <Tissue observation test>
In the structure observation, the average value of the area ratio of the TiC precipitate and the average value of the equivalent circle diameter of the TiC precipitate were obtained by the following procedure.
組織観察では、ＴｉＣ析出物の面積率の平均値、及びＴｉＣ析出物の円相当径の平均値を、以下の手順により求めた。 <Tissue observation test>
In the structure observation, the average value of the area ratio of the TiC precipitate and the average value of the equivalent circle diameter of the TiC precipitate were obtained by the following procedure.
組織観察試験片は、チタン合金板の表裏面から厚さ２ｍｍを除き且つ側面から厚さ５０ｍｍを除いた部位から採取する。この試験片を合成樹脂ホルダに埋め込み、試験片が露出するように研磨し、更にバフ研磨を施した。この研磨した試験片の表面を４００倍の倍率で写真撮影する。この写真撮影は４視野で行い、観察面積は合計で０．２５ｍｍ２である。このようにして得られた画像データから、画像解析ソフト（ナノシステム株式会社製、Ｎａｎｏ Ｈｕｎｔｅｒ ＮＳ２Ｋ－Ｌｔ）を用いて、各写真のＴｉＣ析出物の面積率、並びにその円相当径を求めた。そして、全体の平均値としてＴｉＣ析出物の面積率の平均値、並びにＴｉＣ析出物の円相当径の平均値を計算により求めた。尚、４００倍の倍率での写真撮影でＴｉＣ析出物と確定することが困難である円相当径が０．１μｍ未満の析出物については、対象から除外した。この試験で求められた各試料のＴｉＣ析出物の面積率の平均値とＴｉＣ析出物の平均円相当径の平均値をそれぞれ表２に示す。尚、実施例における各試料には、ＴｉＣ析出物以外の析出物、介在物は存在しなかった。
The tissue observation test piece is collected from a portion excluding the thickness of 2 mm from the front and back surfaces of the titanium alloy plate and the thickness of 50 mm from the side surface. This test piece was embedded in a synthetic resin holder, polished so that the test piece was exposed, and further buffed. The surface of the polished specimen is photographed at a magnification of 400 times. This photography is performed with four fields of view, and the total observation area is 0.25 mm 2 . From the image data thus obtained, image analysis software (Nano Hunter NS2K-Lt, manufactured by Nanosystem Co., Ltd.) was used to determine the area ratio of TiC precipitates and the equivalent circle diameter of each photograph. And the average value of the area ratio of a TiC precipitate and the average value of the equivalent circle diameter of a TiC precipitate were calculated | required by calculation as a whole average value. In addition, the precipitate with an equivalent circle diameter of less than 0.1 μm, which is difficult to be determined as a TiC precipitate by photography at a magnification of 400 times, was excluded from the subject. Table 2 shows the average value of the area ratio of the TiC precipitates of each sample and the average value of the average equivalent circle diameter of the TiC precipitates obtained in this test. In each sample in the examples, no precipitates and inclusions other than TiC precipitates were present.
＜断続切削試験（エンドミル切削試験）＞
前記したチタン合金板からエンドミル切削試験片を採取した。この試験片の寸法は、厚さ１５ｍｍ×幅１８０ｍｍ×長さ１４５ｍｍである。この試験片を用いて断続切削試験（エンドミル切削試験）を行い、工具摩耗量（逃げ面）を確認した。試験結果から、工具摩耗量が６０μｍ以下のものを合格とし、断続切削性に優れたチタン合金であると判断した。この断続切削試験条件を以下に示す。また、この試験で求められた各試料の工具摩耗量（逃げ面）を表２に示す。 <Intermittent cutting test (end mill cutting test)>
An end mill cutting specimen was collected from the titanium alloy plate described above. The dimensions of this test piece are 15 mm thick × 180 mm wide × 145 mm long. An intermittent cutting test (end mill cutting test) was performed using this test piece, and the amount of tool wear (flank) was confirmed. From the test results, a tool wear amount of 60 μm or less was accepted, and the titanium alloy was judged to be excellent in intermittent cutting performance. The intermittent cutting test conditions are shown below. Table 2 shows the amount of tool wear (flank) of each sample obtained in this test.
前記したチタン合金板からエンドミル切削試験片を採取した。この試験片の寸法は、厚さ１５ｍｍ×幅１８０ｍｍ×長さ１４５ｍｍである。この試験片を用いて断続切削試験（エンドミル切削試験）を行い、工具摩耗量（逃げ面）を確認した。試験結果から、工具摩耗量が６０μｍ以下のものを合格とし、断続切削性に優れたチタン合金であると判断した。この断続切削試験条件を以下に示す。また、この試験で求められた各試料の工具摩耗量（逃げ面）を表２に示す。 <Intermittent cutting test (end mill cutting test)>
An end mill cutting specimen was collected from the titanium alloy plate described above. The dimensions of this test piece are 15 mm thick × 180 mm wide × 145 mm long. An intermittent cutting test (end mill cutting test) was performed using this test piece, and the amount of tool wear (flank) was confirmed. From the test results, a tool wear amount of 60 μm or less was accepted, and the titanium alloy was judged to be excellent in intermittent cutting performance. The intermittent cutting test conditions are shown below. Table 2 shows the amount of tool wear (flank) of each sample obtained in this test.
・工具：Ｈ１３Ａチップ
・切削速度：２５ｍ／ｍｍ
・切削送り：０．２ｍｍ／ｒｅｖ
・切り込み量：半径方向０．５ｍｍ、軸方向１．０ｍｍ
・切削長さ：７．２５ｍ（１カット１４５ｍｍ）
・切削油：水溶性潤滑油 ・ Tool: H13A chip ・ Cutting speed: 25 m / mm
・ Cutting feed: 0.2 mm / rev
・ Cut amount: 0.5mm in the radial direction, 1.0mm in the axial direction
・ Cutting length: 7.25m (1cut 145mm)
・ Cutting oil: Water-soluble lubricant
・切削速度：２５ｍ／ｍｍ
・切削送り：０．２ｍｍ／ｒｅｖ
・切り込み量：半径方向０．５ｍｍ、軸方向１．０ｍｍ
・切削長さ：７．２５ｍ（１カット１４５ｍｍ）
・切削油：水溶性潤滑油 ・ Tool: H13A chip ・ Cutting speed: 25 m / mm
・ Cutting feed: 0.2 mm / rev
・ Cut amount: 0.5mm in the radial direction, 1.0mm in the axial direction
・ Cutting length: 7.25m (1cut 145mm)
・ Cutting oil: Water-soluble lubricant
＜室温引張試験＞
前記したチタン合金板から引張試験片を採取した。引張試験はＡＳＴＭ規格のＥ８に準拠して実施した。引張試験片の形状、寸法を図１に示す。試験温度は室温（２５℃）であり、歪速度は１００／ｓｅｃである。試験結果から、引張強度（ＴＳ）が９００ＭＰａ以上で、伸び（ＥＬ）が１０％以上のものを合格とし、高強度のチタン合金であると判断した。この試験で求められた各試料の引張強度（ＴＳ）と伸び（ＥＬ）を、表２に示す。 <Room temperature tensile test>
A tensile test piece was collected from the titanium alloy plate described above. The tensile test was performed in accordance with ASTM standard E8. The shape and dimensions of the tensile test piece are shown in FIG. The test temperature is room temperature (25 ° C.), and the strain rate is 100 / sec. From the test results, those having a tensile strength (TS) of 900 MPa or more and an elongation (EL) of 10% or more were accepted and judged to be a high-strength titanium alloy. Table 2 shows the tensile strength (TS) and elongation (EL) of each sample obtained in this test.
前記したチタン合金板から引張試験片を採取した。引張試験はＡＳＴＭ規格のＥ８に準拠して実施した。引張試験片の形状、寸法を図１に示す。試験温度は室温（２５℃）であり、歪速度は１００／ｓｅｃである。試験結果から、引張強度（ＴＳ）が９００ＭＰａ以上で、伸び（ＥＬ）が１０％以上のものを合格とし、高強度のチタン合金であると判断した。この試験で求められた各試料の引張強度（ＴＳ）と伸び（ＥＬ）を、表２に示す。 <Room temperature tensile test>
A tensile test piece was collected from the titanium alloy plate described above. The tensile test was performed in accordance with ASTM standard E8. The shape and dimensions of the tensile test piece are shown in FIG. The test temperature is room temperature (25 ° C.), and the strain rate is 100 / sec. From the test results, those having a tensile strength (TS) of 900 MPa or more and an elongation (EL) of 10% or more were accepted and judged to be a high-strength titanium alloy. Table 2 shows the tensile strength (TS) and elongation (EL) of each sample obtained in this test.
表２に記載の試料Ｎｏ．は、表１に記載の試料Ｎｏ．と一致している。試料Ｎｏ．４及びＮｏ．６～１１は発明例であり、表１に記載の成分組成と、表２に記載のＴｉＣ析出物の面積率の平均値及び円相当径の平均値が、共に本発明の条件を満足する。その他は全て比較例である。
Sample No. in Table 2 Is the sample No. described in Table 1. Is consistent with Sample No. 4 and no. Examples 6 to 11 are invention examples, and the component composition shown in Table 1, the average area ratio of TiC precipitates and the average equivalent circle diameter shown in Table 2 both satisfy the conditions of the present invention. All others are comparative examples.
発明例の試料Ｎｏ．４及びＮｏ．６～１１は、断続切削試験による工具摩耗量、及び室温引張試験による引張強度（ＴＳ）と伸び（ＥＬ）が全て合格判定基準を満たした。この結果から、試料Ｎｏ．４及びＮｏ．６～１１は、断続切削性に優れた高強度チタン合金であると判断することができる。
Specimen No. of invention example 4 and no. For Nos. 6 to 11, the amount of tool wear by the intermittent cutting test and the tensile strength (TS) and elongation (EL) by the room temperature tensile test all met the acceptance criteria. From this result, sample no. 4 and no. 6 to 11 can be judged to be high-strength titanium alloys having excellent intermittent machinability.
これに対し、本発明の条件の少なくとも１項目を満足しない比較例（試料Ｎｏ．１～３、Ｎｏ．５、及びＮｏ．１２～１９）の場合は、断続切削試験で求められた工具摩耗量、室温引張試験で求められた引張強度（ＴＳ）と伸び（ＥＬ）のうち少なくとも１項目で合格判定基準を満たすことができなかった。すなわち、試料Ｎｏ．１～３、Ｎｏ．５、及びＮｏ．１２～１９は、断続切削性に優れた高強度チタン合金であると判断することができない。
On the other hand, in the comparative examples (samples No. 1 to 3, No. 5, and No. 12 to 19) that do not satisfy at least one of the conditions of the present invention, the amount of tool wear determined by the intermittent cutting test The acceptance criteria could not be satisfied with at least one of the tensile strength (TS) and elongation (EL) determined in the room temperature tensile test. That is, sample no. 1-3, no. 5 and no. 12 to 19 cannot be judged to be high-strength titanium alloys having excellent intermittent machinability.
以上のとおり、本発明を詳細に、また特定の実施態様を参照して説明したが、本発明の精神と範囲を逸脱することなく様々な変更や修正を加えることができることは当業者にとって明らかである。本出願は２００８年６月１１日出願の日本特許出願（特願２００８－１５３２１７）に基づくものであり、その内容はここに参照として取り込まれる。
Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. is there. This application is based on a Japanese patent application filed on June 11, 2008 (Japanese Patent Application No. 2008-153217), the contents of which are incorporated herein by reference.
Claims (4)
- Ｃ：０．０６～０．１３質量％、Ａｌ：３．０～８．５質量％を含有すると共に、Ｖ：５．０質量％以下、Ｃｒ：３．０質量％以下、Ｆｅ：２．５質量％未満、Ｍｏ：６．０質量％以下、Ｎｉ：５．０質量％以下、Ｎｂ：５．０質量％以下、Ｔａ：５．０質量％以下の１種以上を合計で２．０～１０．０質量％含有し、残部がＴｉおよび不可避的不純物であるチタン合金であって、
チタン合金素地中の０．２５ｍｍ２以上の任意断面におけるＴｉＣ析出物の面積率の平均値が０．５％以下であり、前記ＴｉＣ析出物の円相当径の平均値が１μｍ以下であることを特徴とするα－β型チタン合金。 C: 0.06 to 0.13 mass%, Al: 3.0 to 8.5 mass%, V: 5.0 mass% or less, Cr: 3.0 mass% or less, Fe: 2. One or more of less than 5% by mass, Mo: 6.0% by mass or less, Ni: 5.0% by mass or less, Nb: 5.0% by mass or less, Ta: 5.0% by mass or less are 2.0 in total. A titanium alloy containing ˜10.0 mass%, the balance being Ti and inevitable impurities,
The average value of the area ratio of TiC precipitates in an arbitrary cross section of 0.25 mm 2 or more in the titanium alloy substrate is 0.5% or less, and the average value of the equivalent circle diameter of the TiC precipitates is 1 μm or less. Characteristic α-β type titanium alloy. - Ｓｉ：１．０質量％以下を含有する請求項１に記載のα－β型チタン合金。 The α-β type titanium alloy according to claim 1, containing Si: 1.0% by mass or less.
- Ｚｒ：５．０質量％以下、Ｓｎ：５．０質量％以下の１種以上を合計で７．０質量％以下含有する請求項１に記載のα－β型チタン合金。 The α-β-type titanium alloy according to claim 1, containing one or more of Zr: 5.0% by mass or less and Sn: 5.0% by mass or less in total of 7.0% by mass or less.
- Ｚｒ：５．０質量％以下、Ｓｎ：５．０質量％以下の１種以上を合計で７．０質量％以下含有する請求項２に記載のα－β型チタン合金。 The α-β-type titanium alloy according to claim 2, containing one or more of Zr: 5.0 mass% or less and Sn: 5.0 mass% or less in total of 7.0 mass% or less.
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| JP2008153217A JP2009299110A (en) | 2008-06-11 | 2008-06-11 | HIGH-STRENGTH alpha-beta TYPE TITANIUM ALLOY SUPERIOR IN INTERMITTENT MACHINABILITY |
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