JPH0135068B2 - - Google Patents

Description

【発明の詳細な説明】[Detailed description of the invention]

［産業上の利用分野］ 本発明は表面品質並びに寸法精度の優れたα＋
β型Ti合金線材を製造する方法に関するもので
ある。 ［従来の技術］ α＋β型Ti合金は比強度が高く耐食性に優れ
ているところから航空機や宇宙機器等の広い分野
に適用されている。しかるにα＋β型Ti合金は
Ti合金全般に当てはまることではあるが加工性
が極めて悪いという欠点があり所望形状に仕上げ
ることが難しく、特にTi合金線材の製造には多
くの困難を伴ない表面品質並びに寸法精度の優れ
た線材を得ることができなかつた。尚α＋β型
Ti合金の例としてはTi−6Al−4V合金をはじめ
としてTi−3Al−2.5V合金、Ti−8Mn合金、Ti
−8Al−1Mo−1V合金、Ti−6Al−6V−2Sn合
金、Ti−6Al−2Sn−4Zr−2Mo合金等が挙げら
れる。 即ちα＋β型Ti合金線材を製造するに当たつ
ては、該Ti合金を真空溶解して得た鋳塊を分塊
圧延してビレツトとし、これを更に圧延して粗線
材とする。次いで粗線材を焼鈍処理（通常700〜
750℃に加熱後、空冷）に付して焼鈍線材を得、
これを成形加工して所望径のTi合金線材とする。
ところで上記成形加工手段として伸線加工を適用
することができれば問題は少ないが、上述の焼鈍
線材を伸線しようとする途中で断線してしまい伸
線することができない。そこで止むを得ず皮削加
工によつて所望線径に仕上げている。この原因の
１つはTi合金材を圧延および熱処理する際に表
面に強靭なスケールが発生するだけでなくTi合
金中に酸素が侵入してαケースと呼ばれる硬化層
が生成するからであると言われている。従つて伸
線加工する前に上記スケールや硬化層を除去する
必要があるが、現状では有効な除去手段が見出さ
れていない。また伸線加工を困難にしている原因
は上記スケールや硬化層の存在だけではなく、焼
鈍線材自身の塑性加工性が悪いことが大きなウエ
ートを占めていると考えなければならないと思わ
れる。そこで焼鈍処理後、皮削加工に付して得た
Ti合金線材を引張試験に供し、その諸特性を調
べてみると第２図に示す通りであつて、降伏比が
90％を超えており塑性加工性が非常に悪いのも当
然であることが判明した。 ［発明が解決しようとする問題点］ 上記の如く、従来法では伸線加工という手段を
採用することができない為焼鈍線材を皮削加工し
ているが、皮削加工自体の精度の悪さに加えてス
ケールや硬化層の存在する焼鈍線材を皮削りする
ことや圧延表面の残つている焼鈍線材を直接皮削
りすること等の為に皮削位置が不安定となり、そ
れらの結果表面品質並びに寸法精度の優れたTi
合金線材を得ることができなかつた。 ［問題点を解決するための手段］ 本発明はこうした事情に着目し鋭意検討を重ね
た結果完成されたものであつて、その要旨は、α
＋β型Ti合金鋳塊を圧延して得た線材を800〜
900℃に加熱し、直ちに浸水冷却処理を行なつた
後伸線加工に付し、次いで皮削加工を行なう点に
存在する。 ［作用］ 本発明者等は、表面品質並びに寸法精度の優れ
たTi合金線材を得るために、(1)材料自体の塑性
加工性を向上させると共に、(2)スケールや硬化層
の生成をできる限り抑える必要があると考え、熱
処理条件の見直しを行なつた。 即ち伸線加工に際し塑性加工性を向上させる手
段としては従来焼鈍処理を行なうことが望ましい
とされていたが、α＋β型Ti合金の場合には前
述の如く焼鈍処理では塑性加工性を上げる（降伏
比を下げる）ことができず、しかもこのときに材
料表層にスケールや硬化層が生成しており、熱処
理条件に問題があつた。こうした状況から本発明
者等はスケールや硬化層の発生を最小限に抑えつ
つ降伏比を下げることができる様な熱処理条件に
ついて種々検討を重ねた結果前記構成に到達し
た。 即ち本発明においてはα＋β型Ti合金を溶解
して得た鋳塊を圧延して素線材を製造し、これを
800〜900℃に加熱した後直ちに浸水冷却処理を行
なう。これによりスケールや硬化層の生成が僅か
で且つ降伏比の低い熱処理線材を得ることができ
る。即ち上記熱処理温度が800℃より低い場合に
は降伏比の低下度が少なく満足し得る塑性加工性
を得ることができない。一方熱処理温度が900℃
を超えると降伏比の低下度が少ないだけでなく引
張強さ並びに耐力が上昇して塑性加工性が悪化す
る。従つて熱処理温度は800〜900℃とする必要が
ある。尚熱処理時間は線径の中心部が所定の温度
に達するに要する時間であれば十分である。即ち
空中加熱の場合あまり長時間加熱すれば酸化スケ
ールが厚くなる等の不都合なことが生じる。した
がつて加熱時間の目安としては直径８mmのとき10
〜30分とすることが望ましい。また熱処理は従来
と同様空気中で行なえばよいが、スケール等の生
成をより確実に抑える為にはArやCO₂等の不活
性ガス雰囲気中で行なうことが望ましい。次いで
加熱した素線材を冷却するに当たつては熱処理完
了後直ちに素線材を冷却水中に浸漬する。これに
より加熱素線材が急冷されて機械的性質の改善が
進むと共に空気との接触を防止してスケールおよ
び硬化層の生成を抑制する。 尚上記熱処理・急冷によつて降伏比が低下する
理由は明確にし得た訳ではないが、焼入れ処理に
よつて不安定β相が残留したことによるものと考
えられる。この不安定β相は別の温度で焼入れた
ときに得られるβ相より小さい応力で変態をとも
なつて変形をはじめるため降伏応力が最も低くな
るものと考えられる。そしてこの最適不安定β相
が得られる焼入れ温度が合金組成に依存すること
は言う迄もない。 こうして得た熱処理素線材は塑性加工性に優れ
ており、これを伸線加工に付すことによつて表面
状態を平滑で寸法精度の優れたα＋β型Ti合金
線材を得ることができる。次いで該伸線材を皮削
りすると表層に僅かに残つているスケールや硬化
層が比較的簡単に除去され、表面品質並びに寸法
精度の優れたα＋β型Ti合金線材を得ることが
できる。尚上記皮削加工においては被皮削材の表
面が平滑化されているので皮削位置が安定し、表
面精度の低下をまねくことがない。 本発明の基本構成は上記の通りである。ところ
で本発明課題とは別の問題であるが、従来は厚い
スケールや硬化層を有する材料を皮削りしていた
為に皮削工具（鋼の場合に切削性がよいという経
験からJIS−Ｓ種Ti含有超硬工具がそのまま使用
されていた）が激しく損耗するという問題があつ
た。即ち工具の損傷による線材寸法精度の低下お
よび工具交換による生産性の低下を解消すること
が別の要請として存在していた。しかるに本発明
の完成により、被皮削材料はスケールや硬化層を
僅かに有するだけでしかも表面性状の平滑な材料
となつたので皮削用切削工具の損耗も小さくなり
寸法精度の低下および生産性の低下を防止するこ
とができる様になつた。 尚本発明者等は皮削工具の種類についても検討
を加えた結果、α＋β型Ti合金線材の皮削に当
たつてはTiを含まない切削工具［JIS−Ｇ種や
JIS−Ｄ種の超硬工具（第１表参照）、セラミツク
製工具等］の方が耐摩耗性に優れ、損傷し難いこ
とを見出し、またこれらの切削工具を用いること
によつて長期に亘り工具交換を行なうことなし
に、寸法精度の優れたα＋β型Ti合金線材を得
ることに成功した。 [Industrial Application Field] The present invention is an α+ film with excellent surface quality and dimensional accuracy.
The present invention relates to a method for manufacturing a β-type Ti alloy wire. [Prior Art] α+β type Ti alloys have high specific strength and excellent corrosion resistance, so they are used in a wide range of fields such as aircraft and space equipment. However, α+β type Ti alloy
This applies to Ti alloys in general, but they have the disadvantage of extremely poor workability, making it difficult to finish them into the desired shape.In particular, the manufacture of Ti alloy wires involves many difficulties. I couldn't get it. Furthermore, α+β type
Examples of Ti alloys include Ti-6Al-4V alloy, Ti-3Al-2.5V alloy, Ti-8Mn alloy, Ti
Examples include -8Al-1Mo-1V alloy, Ti-6Al-6V-2Sn alloy, Ti-6Al-2Sn-4Zr-2Mo alloy, and the like. That is, in producing an α+β type Ti alloy wire, an ingot obtained by vacuum melting the Ti alloy is bloomed into a billet, which is further rolled to form a rough wire. Next, the rough wire is annealed (usually 700~
After heating to 750℃, air cooling) to obtain annealed wire.
This is formed into a Ti alloy wire rod of a desired diameter.
By the way, if wire drawing can be applied as the above-mentioned forming processing means, there will be fewer problems, but the above-mentioned annealed wire will break during the wire drawing process, making it impossible to draw the wire. Therefore, we had no choice but to finish the wire to the desired wire diameter by skin cutting. One of the reasons for this is that when rolling and heat treating Ti alloy materials, not only tough scale is generated on the surface, but also oxygen penetrates into the Ti alloy, creating a hardened layer called α case. It is being said. Therefore, it is necessary to remove the scale and hardened layer before wire drawing, but at present no effective means of removal has been found. Furthermore, it must be considered that the cause of difficulty in wire drawing is not only the presence of the scale and hardened layer described above, but also the poor plastic workability of the annealed wire itself. Therefore, after annealing, the material was obtained by skin cutting.
When Ti alloy wire was subjected to a tensile test and its various properties were investigated, the yield ratio was as shown in Figure 2.
It was found that it was no surprise that the plastic workability was extremely poor as it exceeded 90%. [Problems to be solved by the invention] As mentioned above, in the conventional method, the annealed wire material is subjected to skin cutting because wire drawing cannot be adopted, but in addition to the poor accuracy of the skin cutting process itself, When annealed wire rods with scales and hardened layers are scraped, or annealed wire rods with remaining rolled surfaces are scraped directly, the scraping position becomes unstable, resulting in poor surface quality and dimensional accuracy. Excellent Ti
It was not possible to obtain alloy wire. [Means for Solving the Problems] The present invention was completed as a result of intensive studies focusing on these circumstances, and the gist thereof is as follows:
800 ~ wire rod obtained by rolling +β type Ti alloy ingot
It is heated to 900°C, immediately cooled by immersion in water, then subjected to wire drawing, and then subjected to skin cutting. [Function] In order to obtain a Ti alloy wire with excellent surface quality and dimensional accuracy, the inventors of the present invention (1) improved the plastic workability of the material itself, and (2) made it possible to form scales and hardened layers. Considering that it is necessary to suppress the heat treatment as much as possible, we reviewed the heat treatment conditions. In other words, it has traditionally been considered desirable to perform annealing as a means of improving plastic workability during wire drawing, but in the case of α+β type Ti alloys, as mentioned above, annealing increases plastic workability (yield ratio Moreover, at this time, scale and a hardened layer were formed on the surface layer of the material, which caused problems with the heat treatment conditions. Under these circumstances, the inventors of the present invention have repeatedly studied various heat treatment conditions that can lower the yield ratio while minimizing the generation of scale and hardened layers, and as a result have arrived at the above structure. That is, in the present invention, an ingot obtained by melting an α+β type Ti alloy is rolled to produce a wire material, and this is
Immediately after heating to 800-900°C, water immersion cooling treatment is performed. As a result, it is possible to obtain a heat-treated wire with little scale or hardened layer formation and a low yield ratio. That is, if the heat treatment temperature is lower than 800°C, the degree of decrease in yield ratio is small and satisfactory plastic workability cannot be obtained. On the other hand, the heat treatment temperature is 900℃
If it exceeds this, not only the degree of decrease in yield ratio is small, but also the tensile strength and yield strength increase, resulting in deterioration of plastic workability. Therefore, the heat treatment temperature needs to be 800 to 900°C. It is sufficient that the heat treatment time is the time required for the center of the wire diameter to reach a predetermined temperature. That is, in the case of air heating, if the heating is carried out for too long, problems such as thickening of the oxide scale will occur. Therefore, the approximate heating time is 10 for a diameter of 8 mm.
~30 minutes is recommended. Further, the heat treatment may be performed in air as in the past, but in order to more reliably suppress the formation of scale, etc., it is desirable to perform the heat treatment in an inert gas atmosphere such as Ar or CO ₂ . Next, when cooling the heated wire material, the wire material is immersed in cooling water immediately after the heat treatment is completed. As a result, the heating element wire is rapidly cooled, improving its mechanical properties, and preventing contact with air to suppress the formation of scale and hardened layer. Although the reason why the yield ratio decreases due to the heat treatment and rapid cooling described above has not been clarified, it is thought to be due to the unstable β phase remaining as a result of the quenching treatment. This unstable β phase is thought to have the lowest yield stress because it undergoes transformation and begins to deform with a smaller stress than the β phase obtained when quenched at a different temperature. It goes without saying that the quenching temperature at which this optimum unstable β phase is obtained depends on the alloy composition. The heat-treated wire rod thus obtained has excellent plastic workability, and by subjecting it to wire drawing, an α+β type Ti alloy wire rod with a smooth surface and excellent dimensional accuracy can be obtained. Next, when the drawn wire material is shaved, the slight scale and hardened layer remaining on the surface layer are relatively easily removed, and an α+β type Ti alloy wire material with excellent surface quality and dimensional accuracy can be obtained. In the above-mentioned skin cutting process, since the surface of the material to be skinned is smoothed, the position of the skin cutting is stable, and the surface accuracy is not deteriorated. The basic configuration of the present invention is as described above. By the way, this is a different problem from the problem of the present invention, but since conventionally materials with thick scales and hardened layers were scraped, a skin cutting tool (JIS-S type was used based on the experience that steel has good machinability). There was a problem that the Ti-containing carbide tools (which were used as they were) were subject to severe wear and tear. In other words, there has been another demand for eliminating the reduction in wire dimensional accuracy due to tool damage and the reduction in productivity due to tool replacement. However, with the completion of the present invention, the material to be cut has only a slight scale or hardened layer and has a smooth surface, which reduces the wear and tear on cutting tools for skin cutting, resulting in a decrease in dimensional accuracy and productivity. It is now possible to prevent the decline in The inventors also considered the types of skin cutting tools, and found that cutting tools that do not contain Ti [JIS-G type or
JIS-D class carbide tools (see Table 1), ceramic tools, etc.] were found to have better wear resistance and are less likely to be damaged, and by using these cutting tools, they can be used for a long period of time. We succeeded in obtaining α+β type Ti alloy wire with excellent dimensional accuracy without changing tools.

【表】 ［実施例］ Ti−6Al−4V合金鋳塊を圧延して得た線材を、
700〜950℃の範囲で30分間熱処理した後、直ちに
水槽へ投入して冷却した。得られた線材の機械的
性質を夫々調べたところ第１図に示す結果が得ら
れた。 第１図に示す様に、800〜900℃殊に850℃で熱
処理したとき、降伏比も低下は顕著であり優れた
塑性加工性を得ることができることが確認され
た。 実施例 Ti−6Al−4V合金を真空アーク溶解して鋳解
（5t）を溶製し、続いて分塊圧延により120mm角の
ビレツトとし、表面疵を除去した後８mm〓の線材
に圧延した。該圧延線材を大気中にて850℃で30
分加熱後、水中で冷却して得た線材の機械的性質
を調べたところ第２表に示す結果が得られた。比
較例として上記圧延線材を700℃で２時間加熱後、
空冷して得た線材の機械的性質を調べ第２表に併
記した。[Table] [Example] A wire rod obtained by rolling a Ti-6Al-4V alloy ingot was
After being heat-treated for 30 minutes in the range of 700 to 950°C, it was immediately put into a water tank and cooled. When the mechanical properties of the obtained wire rods were investigated, the results shown in FIG. 1 were obtained. As shown in FIG. 1, when heat treated at 800 to 900°C, particularly at 850°C, the yield ratio was significantly reduced, confirming that excellent plastic workability could be obtained. EXAMPLE A Ti-6Al-4V alloy was vacuum arc melted to produce a casting (5 tons), which was then bloomed into a billet of 120 mm square, and after surface defects were removed, it was rolled into a wire rod of 8 mm square. The rolled wire rod was heated at 850℃ in the atmosphere for 30 minutes.
The mechanical properties of the wire rod obtained by cooling it in water after heating for several minutes were examined, and the results shown in Table 2 were obtained. As a comparative example, after heating the above rolled wire rod at 700℃ for 2 hours,
The mechanical properties of the air-cooled wire were investigated and are also listed in Table 2.

【表】 第２表に示す様に、比較例線材の降伏比は93％
と高く伸線加工が困難であるのに対し、本発明線
材の降伏比は74％と低く塑性加工性が良好であ
り、以後の工程で伸線加工によるサイジングを行
なうことができる。 次に上述の本発明線材および比較例線材を下記
スケジユールに従つて加工し、工具の摩耗状況を
調べたところ第３表に示す結果が得られた。尚本
発明例においては皮削工具としてJIS−Ｇ種２号
およびJIS−Ｓ種２号を使用し、比較例ではJIS−
Ｓ種２号を使用した。 （加工スケジユール） 本発明 ８mm〓伸線 ――→ 7.75mm〓皮削 ――→ 7.45mm〓再皮削 ――――→ 7.15mm〓 比較例 ８mm〓皮削 ――→ 7.70mm〓[Table] As shown in Table 2, the yield ratio of the comparative example wire is 93%.
However, the yield ratio of the wire rod of the present invention is as low as 74%, and the plastic workability is good, so that sizing can be performed by wire drawing in the subsequent process. Next, the above-mentioned wire rods of the present invention and comparative example wire rods were processed according to the following schedule, and the wear conditions of the tools were examined, and the results shown in Table 3 were obtained. In the example of the present invention, JIS-G class No. 2 and JIS-S class No. 2 were used as the skin cutting tools, and in the comparative example, JIS-G class No. 2 and JIS-S class No. 2 were used.
Type S No. 2 was used. (Processing schedule) Invention 8mm = wire drawing ---> 7.75mm = skinning ---> 7.45mm = re-skinning ---> 7.15mm Comparative example 8mm = skinning ---> 7.70mm

【表】 第３表に示す様に本発明では不都合なしに伸線
加工を行なうことができたが、比較例では伸線し
ようとすると断線が起こる為止むを得ず皮削加工
のみを行なつた。また本発明においてJIS−Ｇ種
２号の切削工具を用いた場合（No.１〜３）には皮
削加工中の線径の増大は殆んど見られなかつた
が、JIS−Ｓ種２号の切削工具を用いたNo.４では
若干の線径増大並びに焼付きが見られた。これら
に対しNo.５、６（比較例）では切削工具の摩耗が
激しく皮削加工中の線径増大は加工量が18.0〜
22.5Kgと少量であるにもかかわらず0.08〜0.09mm
と激しく焼付きや工具の欠損が発生した。即ち本
発明では寸法精度並びに表面品質の優れた線材を
得ることができたが、比較例では寸法精度の悪化
と共に線材表面品質も劣悪であつた。 ［発明の効果］ 本発明は以上の様に構成されており、表面品質
並びに寸法精度の優れたα＋β型Ti合金線材を
得ることができる。[Table] As shown in Table 3, wire drawing could be carried out without any inconvenience in the present invention, but in the comparative example, wire breakage occurred when attempting to draw the wire, so only skin cutting was carried out. Ta. In addition, in the present invention, when JIS-G class No. 2 cutting tools were used (Nos. 1 to 3), almost no increase in wire diameter was observed during skin cutting, but JIS-S class 2 In No. 4, which used the No. 4 cutting tool, a slight increase in wire diameter and seizure were observed. On the other hand, in Nos. 5 and 6 (comparative examples), the cutting tool wear was severe and the increase in wire diameter during skin cutting resulted in a machining amount of 18.0~
Although it is a small amount of 22.5Kg, it is 0.08~0.09mm
Severe seizure and tool breakage occurred. That is, in the present invention, a wire with excellent dimensional accuracy and surface quality could be obtained, but in the comparative example, the dimensional accuracy deteriorated and the wire surface quality was also poor. [Effects of the Invention] The present invention is configured as described above, and it is possible to obtain an α+β type Ti alloy wire with excellent surface quality and dimensional accuracy.

【図面の簡単な説明】[Brief explanation of drawings]

第１図は熱処理条件を求めるために行なつた実
験の結果を示すグラフ、第２図は700℃および850
℃焼鈍材の機械的性質を示すグラフである。 Figure 1 is a graph showing the results of experiments conducted to determine heat treatment conditions, and Figure 2 is a graph showing the results of experiments conducted at 700℃ and 850℃.
It is a graph showing the mechanical properties of °C annealed material.

Claims (1)

【特許請求の範囲】[Claims] １ α＋β型Ti合金鋳塊を圧延して得た線材を
800〜900℃に加熱し、直ちに浸水冷却処理を行な
つた後伸線加工に付し、次いで皮削加工を行なう
ことを特徴とする表面品質並びに寸法精度の優れ
たTi合金線材の製造方法。1 A wire rod obtained by rolling an α+β type Ti alloy ingot is
A method for producing a Ti alloy wire with excellent surface quality and dimensional accuracy, which comprises heating the wire to 800 to 900°C, immediately cooling it in water, drawing it, and then skinning it.