JPH10251706A

JPH10251706A - Method for sintering titanium compact

Info

Publication number: JPH10251706A
Application number: JP5723897A
Authority: JP
Inventors: Tei Yashiro; 悌家城; Takami Masui; 孝実増井
Original assignee: MIE PREF GOV
Current assignee: MIE PREF GOV
Priority date: 1997-03-12
Filing date: 1997-03-12
Publication date: 1998-09-22
Anticipated expiration: 2017-03-12
Also published as: JP3039919B2

Abstract

PROBLEM TO BE SOLVED: To prevent the penetration of oxygen from the internal atmosphere of a furnace and obtain a titanium sintered compact excellent in mechanical characteristics and almost free from deformation due to sintering by embedding a titanium compact in BN powder in a heat resistant vessel so that the surface of the compact is completely coated and the shape of the compact is retained and then sintering the compact in vacuum. SOLUTION: Since the BN powder is stable at high temp. and completely coats the surface of the titanium compact, it suppresses the penetration of oxygen without reacting with the compact at the time of high temp. sintering and ensures uniform heat distribution around the compact. A titanium material including a sintered compact reduces its breaking extension but increases its tensile strength, offset yield stress strength at 0.2% permanent set and hardness in accordance with the increase of the oxygen content. The objective titanium sintered compact properly having elongation and strength contradictory to each other in accordance with the purpose for which it is used is obtd. by coating the surface of the titanium compact with the BN powder and controlling the oxygen content of the resultant sintered compact.

Description

【発明の詳細な説明】DETAILED DESCRIPTION OF THE INVENTION

【０００１】[0001]

【発明の属する技術分野】本発明は、粉末冶金法を用い
て、軽量、高強度かつ高耐食性を有するチタン部品を製
造する方法にかかわり、焼結に際して炉内雰囲気からの
酸素、窒素、炭素からなる不純物の侵入が少なく、機械
的特性に優れたチタン焼結体を得るための焼結方法に関
する。[0001] The present invention relates to a method for producing a lightweight, high-strength, and high-corrosion-resistant titanium component using a powder metallurgy method. The present invention relates to a sintering method for obtaining a titanium sintered body having less mechanical invasion and excellent mechanical properties.

【０００２】[0002]

【従来の技術】チタンは軽く、高い強度を有し、耐食性
にも優れているため、宇宙・航空機器材料、輸送機器材
料、化学プラント材料をはじめ建築材料、レジャー用
品、スポーツ用品、生体・医療材料等に利用されてい
る。また、耐食性、高比強度の他、耐熱性や超塑性機能
も有しているので、鉄系材料に代わる機能・構造用材料
として期待されている。一般に広く使用されている鉄系
材料、アルミ系材料等の製造方法は主に溶解鋳造法であ
るが、チタンのような活性な金属では高温における溶解
等の処理に技術的な問題点が多い。また、チタンは難加
工性材料であるため、機械加工による部品製造にも困難
が伴う。2. Description of the Related Art Titanium is light, has high strength, and is excellent in corrosion resistance. Therefore, it is used in space and aviation equipment materials, transportation equipment materials, chemical plant materials, building materials, leisure goods, sports goods, biological and medical equipment. Used for materials. In addition, since it has heat resistance and superplasticity in addition to corrosion resistance and high specific strength, it is expected as a functional / structural material that replaces iron-based materials. The method of producing iron-based materials, aluminum-based materials, and the like, which are generally widely used, is mainly a melting and casting method. However, active metals such as titanium have many technical problems in processing such as melting at high temperatures. In addition, since titanium is a difficult-to-process material, it is difficult to manufacture parts by machining.

【０００３】このため、金属粉末射出成形法をはじめ様
々な粉末冶金法によりニアネット成形が試みられてい
る。これらの成形法により得られた成形体を焼結して部
品に製造する場合、チタン等の活性な金属は、１０^-2Ｐ
ａオーダーの高真空の焼結雰囲気中においても炉内から
の酸素のピックアップにより著しく延性が損なわれ、そ
のため破断伸びが極端に減少する。この酸素汚染の問題
を解決する方法として、焼結用ケース内にゲッター金属
を入れ、そのゲッター金属に酸素をピックアップさせて
被処理物を焼結する方法が開示されている（Ｔｉまたは
Ｔｉ合金焼結体の製造方法；特開平６−３３０１０
５）。For this reason, near net molding has been attempted by various powder metallurgy methods such as a metal powder injection molding method. When sintering a molded body obtained by these molding methods to produce a part, an active metal such as titanium contains 10 ⁻² P
Even in a high-vacuum sintering atmosphere of the order a, ductility is significantly impaired by the pick-up of oxygen from the furnace, and the elongation at break is extremely reduced. As a method for solving the problem of oxygen contamination, a method is disclosed in which a getter metal is placed in a sintering case, oxygen is picked up by the getter metal, and the workpiece is sintered (Ti or Ti alloy firing). Method for producing bonded body;
5).

【０００４】しかし、成形体の形状は、製品（部品）の
使用目的により平坦で単純な形状の他に複雑な形状もあ
り、焼結時における成形体の形崩れ等の形状変化を防止
するためには、成形体を耐熱性のある粉末等に埋め込ん
で成形体の形状を保持したまま焼結することが必要であ
る。ところが、チタン等の活性な金属焼結体を製造する
ためには、成形体を埋め込む粉末は耐熱性の他、成形体
との反応性のないこと及び成形体の酸素ピックアップを
できる限り妨げる効果がなければならないという問題が
あった。[0004] However, the shape of the compact may be complicated depending on the purpose of use of the product (part) in addition to a flat and simple shape. In order to prevent a shape change such as shape collapse of the compact during sintering. For this purpose, it is necessary to embed the compact in heat-resistant powder or the like and sinter it while maintaining the shape of the compact. However, in order to produce an active metal sintered body such as titanium, the powder for embedding the compact has heat resistance, has no reactivity with the compact, and has the effect of preventing oxygen pickup of the compact as much as possible. There was a problem that had to be.

【発明が解決しようとする課題】[Problems to be solved by the invention]

【０００５】本発明は、具体的には安定な非酸化物系の
ＢＮ粉末で成形体を被覆して焼結することにより、炉内
雰囲気からの酸素の侵入を極力防止して、機械的特性に
優れ、しかも焼結変形の少ないチタン焼結体を製造する
方法の提供を目的とする。The present invention specifically relates to a method for coating a compact with a stable non-oxide BN powder and sintering the same to minimize the intrusion of oxygen from the atmosphere in the furnace and to improve the mechanical properties. It is an object of the present invention to provide a method for producing a titanium sintered body which is excellent in sintering deformation and has less sintering deformation.

【０００６】[0006]

【課題を解決するための手段】上記目的を達成するため
の本発明は、耐熱性を有する容器内にＢＮ( 窒化ボロ
ン）粉末を入れ、このＢＮ粉末にチタン成形体を埋め込
んで成形体表面を完全に被覆することにより成形体の形
状を保持した後、真空雰囲気中において焼結する方法で
ある。According to the present invention for achieving the above object, a BN (boron nitride) powder is placed in a heat-resistant container, and a titanium compact is embedded in the BN powder to clean the surface of the compact. This is a method of sintering in a vacuum atmosphere after maintaining the shape of the compact by completely covering.

【０００７】[0007]

【発明の実施の形態】焼結すべき成形体には、圧縮成形
法や金属粉末射出成形法のような粉末冶金法により原料
チタン粉末を成形したものを想定しているが、本発明の
実施においては、チタンをはじめとする活性金属の圧延
材や押出し材等の高温熱処理にも利用できる。DESCRIPTION OF THE PREFERRED EMBODIMENTS As a compact to be sintered, it is assumed that a raw titanium powder is formed by a powder metallurgy method such as a compression molding method or a metal powder injection molding method. Can be used for high-temperature heat treatment of rolled or extruded materials of active metals such as titanium.

【０００８】チタン成形体及びＢＮ粉末を入れる容器
は、高温焼結において変形などを生じない程度の耐熱性
を有することが必要であり、具体的な材質のひとつにア
ルミナが挙げられる。[0008] The container for holding the titanium compact and the BN powder needs to have heat resistance that does not cause deformation or the like during high-temperature sintering. A specific material is alumina.

【０００９】また、焼結雰囲気に関しては、成形体への
不必要な酸素の侵入を予め防止しておくためにも真空雰
囲気が望ましく、真空度は１０^-2Ｐａオーダー以上の高
真空が好ましい。The sintering atmosphere is preferably a vacuum atmosphere in order to prevent unnecessary intrusion of oxygen into the compact in advance, and the degree of vacuum is preferably a high vacuum of the order of 10 ^-2 Pa or more.

【００１０】本発明に用いるＢＮ粉末は高温において安
定であり、しかも成形体表面を完全に被覆しているた
め、高温焼結時において成形体と反応することなく酸素
の侵入を抑制するとともに、成形体周辺の熱分布を均一
にする効果がある。The BN powder used in the present invention is stable at high temperatures and completely covers the surface of the compact, so that it does not react with the compact during high-temperature sintering and suppresses the invasion of oxygen. This has the effect of making the heat distribution around the body uniform.

【００１１】また、焼結体の密度向上を考慮すれば、原
料となるチタン粉末は微細な程効果があり、平均粒径３
０μｍ以下が好ましい。しかし、焼結すべきチタン成形
体を被覆するＢＮ粉末は細かいほど酸素の遮断効果は大
きいが、微細すぎると成形体に入り込む可能性もあるた
め、１０〜５０μｍの範囲とする。In consideration of the improvement in the density of the sintered body, the finer the titanium powder as the raw material, the more effective the titanium powder.
It is preferably 0 μm or less. However, the finer the BN powder that coats the titanium compact to be sintered, the greater the oxygen blocking effect. However, if the BN powder is too fine, it may enter the compact, so the range is 10 to 50 μm.

【００１２】一方、焼結体を含めたチタン材料は、材料
中の酸素含有量が増えると破断伸びが減少する反面、引
張強さ、０．２％耐力及びかたさの強度が増大するた
め、酸素含有量を制御することにより、使用目的に応じ
て伸びと強度の相反する両特性を適正に備えたチタン焼
結体製品を作製することができる。本発明における成形
体被覆材料のＢＮは粉末であるため、これに酸化物系の
アルミナ粉末等を均一に混合した複合粉末を用いて焼結
すれば、チタン焼結体の酸素含有量の制御は可能であ
り、また酸素量制御による傾斜機能材料へも応用でき
る。On the other hand, in the case of titanium materials including sintered bodies, the elongation at break decreases as the oxygen content in the material increases, but the tensile strength, 0.2% proof stress, and the strength of hardness increase. By controlling the content, it is possible to produce a titanium sintered body product that appropriately has both properties of elongation and strength opposite to each other according to the purpose of use. Since the BN of the molded body coating material in the present invention is a powder, sintering using a composite powder obtained by uniformly mixing oxide-based alumina powder or the like with the BN makes it possible to control the oxygen content of the titanium sintered body. It can be applied to functionally graded materials by controlling the amount of oxygen.

【００１３】[0013]

【実施例】本発明の実施例を図面を用いて具体的に説明
する。図１は、本発明の焼結方法を示す概略図である。DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described with reference to the drawings. FIG. 1 is a schematic diagram showing the sintering method of the present invention.

【００１４】（実施例１）原料に粒径４５μｍ以下の純
チタン粉末（ガスアトマイズ粉末、平均粒径２３μｍ）
を用いて作製した引張試験片形状の成形体を、図１に示
すように焼結用アルミナ容器の中に入れ、２００℃／時
間の速度で昇温して表１に示す条件で真空度１０^-2Ｐａ
オーダーの真空焼結を行った。(Example 1) Pure titanium powder having a particle size of 45 µm or less (gas atomized powder, average particle size of 23 µm) was used as a raw material.
The molded body in the form of a tensile test piece prepared by using the above method was placed in an alumina container for sintering as shown in FIG. 1, and the temperature was raised at a rate of 200 ° C./hour. ^-2 Pa
Order vacuum sintering was performed.

【００１５】図１の焼結用容器の縦断面略図に、焼結に
際してのチタン成形体とＢＮ粉末のセッティング方法を
示す。すなわち、耐熱性を有する焼結用アルミナ容器の
中にＢＮ粉末を敷いた後、その表面を平らにし、その上
に焼結すべきチタン成形体を静かに置いた。次に、チタ
ン成形体のすべての面が完全に覆われるようにＢＮ粉末
を追加してセットした。A method for setting a titanium compact and BN powder during sintering is shown in a schematic longitudinal sectional view of the sintering vessel of FIG. That is, after BN powder was laid in a heat-resistant alumina container for sintering, the surface was flattened, and a titanium compact to be sintered was gently placed on the surface. Next, BN powder was additionally set so that all surfaces of the titanium compact were completely covered.

【００１６】以上の方法により得られたチタン焼結体の
酸素量及び常温での引張特性を表２に示す。表２から明
らかなように、実施例ではチタン焼結体に対するＢＮ効
果により酸素の低減がはかられ、そのため伸びが著しく
向上して良好な引張特性を有するチタン焼結体が得られ
た。比較例では焼結等によく用いられているアルミナ粉
末を被覆粉末として使用しているため、焼結温度の上昇
と共に酸素量が増加している。その結果、チタン焼結体
は脆化して伸びが減少していることが明白である。ま
た、極端に脆化しない範囲においては、強度的には酸素
の侵入により引張強さ、０．２％耐力及びかたさの強度
が増大していることがわかる。Table 2 shows the oxygen content and the tensile properties at room temperature of the titanium sintered body obtained by the above method. As is clear from Table 2, in the example, oxygen was reduced by the BN effect on the titanium sintered body, so that elongation was significantly improved and a titanium sintered body having good tensile properties was obtained. In the comparative example, since the alumina powder commonly used for sintering or the like is used as the coating powder, the amount of oxygen increases as the sintering temperature increases. As a result, it is clear that the titanium sintered body is embrittled and the elongation is reduced. Further, in the range not extremely brittle, it can be seen that the tensile strength, the 0.2% proof stress, and the hardness are increased due to the penetration of oxygen.

【００１７】[0017]

【表１】 [Table 1]

【００１８】[0018]

【表２】 [Table 2]

【００１９】[0019]

【発明の効果】以上説明したように、本発明を用いてチ
タン成形体を焼結することにより、室温における破断伸
びの優れたチタン焼結体を得ることができた。このた
め、部品の信頼性を損ねる脆性破壊を回避することがで
き、しかも焼結による変形も少ないことから正確な部品
が製造できる。As described above, by sintering a titanium compact using the present invention, a titanium sintered compact having excellent breaking elongation at room temperature was obtained. For this reason, it is possible to avoid brittle fracture that impairs the reliability of the component, and it is possible to manufacture an accurate component since deformation due to sintering is small.

【００２０】また、本発明は粉末冶金法における焼結の
みの使用に限らず、チタンあるいはチタン合金のような
活性な純金属や合金の酸素含有量を制御した熱処理にも
応用できる。The present invention can be applied not only to the use of only sintering in powder metallurgy but also to a heat treatment in which the oxygen content of an active pure metal or alloy such as titanium or a titanium alloy is controlled.

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

【図１】本発明の実施例を示す焼結用容器の縦断面略
図である。FIG. 1 is a schematic longitudinal sectional view of a sintering vessel showing an embodiment of the present invention.

【符号の説明】[Explanation of symbols]

１焼結用アルミナ容器２ＢＮ粉末３チタン成形体 DESCRIPTION OF SYMBOLS 1 Alumina container for sintering 2 BN powder 3 Titanium compact

Claims

【特許請求の範囲】[Claims]

【請求項１】チタン粉末を原料として、得られた成形
体を焼結する成形体の焼結方法において、ＢＮ（窒化ボ
ロン）粉末にチタン成形体を埋め込んで焼結することを
特徴とするチタン成形体の焼結方法。1. A method for sintering a compact obtained by sintering a compact obtained using titanium powder as a raw material, wherein the titanium compact is embedded in BN (boron nitride) powder and sintered. The method of sintering the compact.