JP4659278B2 - Tungsten sintered body and manufacturing method thereof, tungsten plate material and manufacturing method thereof - Google Patents
Tungsten sintered body and manufacturing method thereof, tungsten plate material and manufacturing method thereof Download PDFInfo
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Description
【0001】
【発明の属する技術分野】
本発明は、W材料およびその製造方法に関し、詳しくは高温炉用反射板および炉用構造部材および高輝度電極素材等に用いられるW材料およびその製造方法に関する。
【0002】
【従来の技術】
高融点金属材料の特長は優れた耐熱性である。高融点金属材料中でもWは、最高融点3380℃を有する金属であり、高温における多用が期待されるものである。しかしながら、現行市販されているW板材および線棒材は純Wであり、次の理由から使用の制限を受けている。その理由は、例えばW板材を1100℃以上の高温下で使用すると再結晶粒成長を起こし、圧延加工により形成された伸長した積層の繊維組織が等軸状の球状組織に変貌し高温強度が低下してしまうことである。また、この組織の変貌は、元々延性に乏しい性質を更に脆弱な材料へ変質させてしまい実用性に欠く原因となっている。
【0003】
そのような再結晶粒成長は、Wの本質的性質であり、これを防止することは不可能であるが、粒成長を抑制することによって、W本来の特質が活かされた用途の展望が開かれると考える。
【0004】
次に、純W板および線棒材の欠点について述べる。これらの材料は、再結晶開始温度が1100℃である。保持時間との関連もあるが、1100℃から再結晶粒成長が始まる。
【0005】
また、Wに期待される実用温度は1700℃以上である。Wに代用できる材料としては、モリブデン(Mo)があるが、Moの融点は、2630℃とWに比べて低いため、強度の低下が大きい。また1700℃における蒸気圧は、W(10−11torr)がMo(10−7torr)に比べ4桁以上小さく、消耗が少ないため長寿命である。
【0006】
さらに、再結晶開始と同時に組織が変化する。高温強度が維持されている組織であれば問題無いが、組織変化により高温強度が低下し、且つ脆性材料へと変質する。
【0007】
【発明が解決しようとする課題】
そこで、W材料の高温特性の改善を進める方法が種々提案されている。それらの改善方法は、次のように大別される。
【0008】
(1)ThO2などの酸化物分散効果による改善、
(2)HfCなどの炭化物析出効果による改善、
(3)Nbなどの異種金属の合金固溶効果による改善等。
【0009】
上記(2)の改善方法は、大きさがnmオーダーの微細な炭化物を析出間距離を小さくし、析出物とWマトリックスの転位との相互作用によるものである。炭化物を微細にドープ,析出させる方法としてメカニカルアロイング(MA)法がある。
【0010】
しかしながら、この(2)の方法では、W粒子も非常に微細になることにより活性となり空気との反応により着火,爆発の恐れのため取扱が困難であり、Wの工業的生産手法としては難がある。
【0011】
一方、上記(3)の改善方法は、高融点金属同士の固溶による強化を狙うものではあるが、Nbは非常に高価な金属であるため数%の添加を考えても、コストが高く商用規模の材料提供には非現実的であり、特殊部材向けなどの限定的用途となる。
【0012】
そこで、上記(1)の酸化物分散効果は、Wの組織を高温化においても安定せしめ、再結晶温度を上昇させる働きがあるためと考えられる。
【0013】
しかしながら、上記(1)の改善方法においてThO2は、放射性物質であるため、取扱の法規制や使用時の環境への飛散による汚染などの観点から使用困難な物質である。
【0014】
先行技術として、ThO2の代わる代替材として、希土類元素のうちランタン酸化物(La2O3,融点2300℃)を選定し、WにLa2O3を0.4〜1.2質量%分散させ、再結晶後に加工方向に伸長した長大結晶粒の積層組織を形成させることによって、高温域においても高い引張強度を有した板材が提案されている(特開平11−152534号公報、参照)。
【0015】
このように従来技術において、再結晶後に高温特性に優れた長大結晶粒の積層組織を有する板材を得るためには高加工率の塑性加工が不可欠となり、バルク,厚板への適用には限界がある。
【0016】
そこで、本発明の一技術的課題は、高温下においても結晶粒が殆ど粗大化しない優れた組織安定性を有する焼結体とその製造方法とを提供することにある。
【0017】
また、本発明のもう一つの技術的課題は、前記焼結体を素材として塑性加工を施した板材において、先行技術品より高い高温強度を有するタングステン板材を提供することにある。
【0018】
【課題を解決するための手段】
本発明によれば、ランタン酸化物が5〜10質量%,レニウムが3〜20質量%,残部がタングステンおよび不可避不純物分からなり、相対焼結体密度が99.2〜99.9%で、結晶粒径が5.0〜6.1μmであり、且つ真空中2200℃にて100時間加熱しても10μm以下の結晶粒径を維持することを特徴とするタングステン焼結体が得られる。
【0019】
また、本発明によれば、前記タングステン焼結体を製造する方法であって、タングステンの青色酸化物にランタン酸化物を前記タングステン焼結体に5〜10質量%含有した後、還元し、その粉末にレニウム粉末を前記タングステン焼結体中に3〜20質量%含有するように添加・混合した後、等方加圧焼結(HIP)を用いることによって、相対焼結体密度が99.2〜99.9%で且つ5.0〜6.1μmの結晶粒からなるタングステン焼結体を得ることを特徴とするタングステン焼結体の製造方法が得られる。
【0020】
また、本発明によれば、5質量%以上10質量%以下のランタン酸化物と5質量%以上20質量%以下のレニウムおよび残部がタングステンおよび不可避不純物分からなり、且つ1000℃における引張り強度が405MPa以上450MPa以下であることを特徴とするタングステン板材が得られる。
【0021】
また、本発明によれば、前記タングステン板材を製造する方法であって、タングステンの青色酸化物にランタン酸化物を前記タングステン焼結体に5〜10質量%含有するように添加した後、還元し、その粉末にレニウム粉末を前記タングステン焼結体中に5〜20質量%含有するように添加・混合した後、等方加圧焼結(HIP)を用いて焼結し、総板厚減少率93%以上で鍛造あるいは圧延することを特徴とするタングステン板材の製造方法が得られる。
【0025】
【発明の実施の形態】
まず、本発明について更に詳細に説明する。
【0026】
本発明では、W材料の高温強度を図るため、ランタン酸化物分散効果に加え、Reの固溶強化による改善を狙った。
【0027】
W材料中にドープ酸化物を均一微細分散させるには、W材料製造工程の上流、すなわち原料に近いほうが良い。安定な酸化物として、三酸化タングステン(WO3),青色酸化物(W4O11)がある。
【0028】
本発明では、酸化物粒子表面に微細なクラックが存在する青色酸化物がドープ元素量のコントロールの点で優位であると考え、これを使用することにした。
【0029】
ドープ元素は高温強度向上に不可欠であるが、少なくてもその効果は発揮できず、多すぎると圧粉体の焼結密度が不足し、後工程の熱間加工が不可能となる欠点がある。
【0030】
そこで、本発明ではLa2O3添加量を5〜10%にし、且つ固溶強化元素であるReを3〜20%添加したW圧粉体を作製し、焼結体の焼結密度を上げるため、真空焼結の後、等方加圧焼結(HIP)を用いて高緻密化させた焼結体を作製した。
【0031】
ここで、本発明において、最大La2O3添加量を10%にしたのは、これ以上添加量を増やすとHIPを用いても焼結密度が上がらないためである。
【0032】
また、本発明において、Re量を3〜20%にしたのは、3%以下だと固溶強化としての効果を示さないためであり、20%以上になると、コストが高く商用規模の材料提供には非現実的になるためである。
【0033】
次に、本発明の実施の形態によるW材料の作製方法と、材料評価方法の具体例を純W材料と比較して述べる。
【0034】
(材料作製方法)
本発明の実施の形態によるW材料は、粉末冶金法に拠り作製される。平均粒径15μm,高純度の青色W酸化物粉(通称,代表的組成式W4O11,W純度99.98%)を原料とし、これに所定量のLa2O3を分散含有させた。酸化物を数十質量ppmから数質量%の範囲で微細均一分散させるために湿式法を用いた。まずLa2O3を試薬特級の硝酸にて溶解後、エチルアルコールにて希釈し、La2O3濃度10g/lのドープ用原液を作製する。磁器製蒸発皿に、1lのエチルアルコールを計量注入し、さらに目的ドープ量に見合うドープ原液をメスビュレットにて計量注入した蒸発皿の中に、予め秤量した青色酸化物(酸素量19.4%)5,000gを投入し、スラリー状になるまで十分攪拌する。この蒸発皿を乾燥機の上に乗せ、約100℃に加熱しながら攪拌を続け、アルコール臭が無くなるまで乾燥した後冷却する。元の状態に戻った青色酸化物は、La2O3を分散させたW酸化物となる。
【0035】
ドープW酸化物を850℃の水素還元炉中のて還元し、ドープW粉を得る。このドープW粉の平均粒径は2.50μm,W純度99.95%であり、La2O3濃度はドープW酸化物状態と同一濃度である。
【0036】
それぞれ所定量のLa2O3を添加したドープW粉に所定量の金属Re粉を添加し、混合した。
【0037】
このようにして得られたW−La2O3−Re粉をラバーバックに充填、密閉後、真空引きし、静水圧プレス機により成型した。成型圧力は223MPaとした。この成型体を2000℃の真空焼結炉で10時間焼結した後、2000℃−196MPa−3時間の条件でHIPを行い、高緻密化させたW合金を得た。本発明にて作製したW焼結体の密度を表1に示す。上記手法にて得られたこれらの焼結体の組織を確認したところ、純Wと比較して非常に微細な結晶粒を有するものであった。測定した結晶粒径の値も併せて下記表1に示す。
【0038】
【表1】
【0039】
焼結体の寸法は厚さ15mm,幅60mm,長さ100mmである。焼結体中のランタン酸化物は、W焼結粒の粒界および粒内に平均粒径サブミクロンないし1μmの粒状に分布・存在していた。またReは、EPMAにて固溶状態を調べたところ、Wマトリックス中に均一に固溶していた。
【0040】
これらの焼結体を小さく切り出し、真空中2200℃にて1時間から最長100時間まで加熱処理を行い、それらの結晶粒径を測定することによって、高温加熱による組織安定性を調べた。加熱時間と結晶粒径の関係を図1に示す。図1に示すように、焼結温度より200℃高い温度にて100時間加熱を施しても、その結晶粒は殆ど粗大化はせず、10μm以下の微細結晶粒を保持していた。
【0041】
これらの焼結体を次の手順で熱間圧延し、最終板厚1mm(総板厚減少率93%)に仕上げた。熱間圧延の初期段階では加熱温度1300℃〜1500℃,圧延パス当りの圧延率を15〜30%とした。圧延終期では加熱温度800℃〜1000℃,圧延率を10〜25%とし、板厚1mm×幅70mm×長さ600mm(圧延作業に支障のため中間で長手方向半分に切断)の表面が酸化物で覆われた圧延板を得た。この圧延板を水素中,1200℃,30分の歪取焼鈍処理の後、酸洗化学処理により洗浄し金属光沢面の板となし、引張試験用素材に使用した。
【0042】
引張試験片の作製には、放電ワイヤ加工機を用いた。その試験片は全長60mm,平行部長さ30mm,幅4mmとし、平行部は1500番のエメリー紙で最終研磨し、切断時の変形層を除去した。
【0043】
一方、比較材の純W材料の作製はドープ工程を除き同じプロセスを踏襲して実施した。
【0044】
本発明と比較材との両試験片に、真空中1500℃,1時間の焼鈍処理を行った後、引張試験に供した。高温引張試験は、窒素雰囲気中,歪速度5×10−4S−1で行った。
【0045】
図2は1700℃における本発明材(W−10%La2O3−3〜20%Re)のRe量と引張強度の関係を示す図である。図2に示すように、La2O3およびReを添加した本発明材の引張強度が比較材より高い値を示した。更にRe添加量を増やすほど、引張強度は高い値を示した。
【0046】
図3は1000℃〜1700℃の高温域における本発明材(W−10%La2O3−20%Re)と比較材の引張強度と温度の関係を示す図である。図3に示すように、試験を行った全ての温度域において、本発明材の引張強度が比較材の約2.5倍の引張強度を示した。更に先行技術により提案されたW−1%La2O3板(圧延等の条件は同じ)と比較しても高い引張強度を示した。尚、他の組成のW板材の強度の例を下記表2に示す。
【0047】
【表2】
【0048】
【発明の効果】
以上、説明したように、本発明によれば、ランタン酸化物およびレニウムを均一に分散・固溶させることによって、純Wに比べ、非常に微細な結晶粒を有し、これらの焼結体は高温加熱においても結晶粒粗大化は起こらない非常に安定した焼結体およびその製造方法を提供することができる。
【0049】
さらに、本発明によれば、前述の焼結体を素材として、例えば2.5倍程度の高温強度を有する新規なタングステン板材およびその製造方法を提供することができる。
【0050】
また、本発明に用いたランタン酸化物は、ThO2に比べ取り扱いが容易で放射能汚染も全く無く、無公害の材料である。したがって本発明によれば、La2O3のドープ技術,当該ドープ焼結体の圧延技術は量産志向の高いものであり、工業化も容易であるタングステン焼結体ならびにそれらを素材として塑性加工を施した板材の製造方法を提供することができる。
【0051】
また、本発明によるタングステン焼結体ならびにそれらを素材として塑性加工を施した板材は、優れた組織安定性や高温強度を生かし、高温炉用反射板および炉用構造部材等の耐高温脆性,耐高温変形性が要求される用途に最適である。
【0052】
さらに、本発明によるタングステン焼結体ならびにそれらを素材として塑性加工を施した板材は、優れた高温強度を有するので、高温負荷や、高エネルギーが入力される高輝度電極の耐垂下性,耐消耗性および耐熱変形も改善することができる。
【図面の簡単な説明】
【図1】本発明の実施の形態による焼結体を真空中2200℃にて1時間〜100時間まで加熱処理したものの、加熱時間と結晶粒径との関係を示す図である。
【図2】本発明の実施の形態による焼鈍材(W−10%La2O3−3〜20%Re)における、Re量と引張強度との関係を示す図であり、併せて比較材として純Wの焼鈍材も示している。
【図3】本発明の実施の形態による焼鈍材(W−10%La2O3−20%Re)における、試験温度と引張強度との関係を示す図であり、併せて比較材として純Wの焼鈍材も示している。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a W material and a manufacturing method thereof, and more particularly to a W material used for a reflector for a high temperature furnace, a structural member for a furnace, a high-luminance electrode material, and the like, and a manufacturing method thereof.
[0002]
[Prior art]
The feature of the refractory metal material is excellent heat resistance. Among refractory metal materials, W is a metal having a maximum melting point of 3380 ° C. and is expected to be widely used at high temperatures. However, the currently marketed W plate and wire rod are pure W and are restricted in use for the following reasons. The reason is that, for example, when a W plate material is used at a high temperature of 1100 ° C. or higher, recrystallized grain growth occurs, and the elongated laminated fiber structure formed by rolling transforms into an equiaxed spherical structure, resulting in a decrease in high-temperature strength. It is to do. In addition, this transformation of the structure causes a property that is originally poor in ductility to be transformed into a more fragile material, which is a cause of lack of practicality.
[0003]
Such recrystallized grain growth is an essential property of W and cannot be prevented. However, by suppressing grain growth, the prospect of applications in which the original characteristics of W are utilized opens up. I think.
[0004]
Next, the disadvantages of the pure W plate and the wire rod will be described. These materials have a recrystallization start temperature of 1100 ° C. Although there is a relationship with the holding time, recrystallized grain growth starts from 1100 ° C.
[0005]
Moreover, the practical temperature expected for W is 1700 ° C. or higher. As a material that can be substituted for W, molybdenum (Mo) is available. However, since the melting point of Mo is 2630 ° C., which is lower than that of W, the strength is greatly reduced. Further, the vapor pressure at 1700 ° C. has a long life because W (10 −11 torr) is four orders of magnitude smaller than Mo (10 −7 torr) and consumption is small.
[0006]
Furthermore, the structure changes simultaneously with the start of recrystallization. There is no problem as long as the structure maintains the high-temperature strength, but the high-temperature strength decreases due to the change in structure, and the structure changes into a brittle material.
[0007]
[Problems to be solved by the invention]
Therefore, various methods for improving the high temperature characteristics of the W material have been proposed. These improvement methods are roughly classified as follows.
[0008]
(1) Improvement due to oxide dispersion effect such as ThO 2
(2) Improvement due to carbide precipitation effect such as HfC,
(3) Improvement by an alloy solid solution effect of dissimilar metals such as Nb.
[0009]
The improvement method (2) is based on the interaction between precipitates and dislocations in the W matrix by reducing the distance between precipitations of fine carbides having a size of nm order. There is a mechanical alloying (MA) method for finely doping and precipitating carbide.
[0010]
However, in the method (2), W particles become very fine and become active, and are difficult to handle due to the risk of ignition and explosion due to reaction with air. is there.
[0011]
On the other hand, the improvement method of (3) above aims at strengthening by the solid solution of refractory metals. However, Nb is a very expensive metal, so even if considering the addition of several percent, the cost is high and commercial. It is impractical to provide materials of scale, and is limited to applications such as for special members.
[0012]
Therefore, it is considered that the oxide dispersion effect (1) has a function of stabilizing the W structure even at high temperatures and increasing the recrystallization temperature.
[0013]
However, in the improvement method of (1) above, ThO 2 is a radioactive substance, so it is a difficult substance to use from the viewpoint of handling regulations and contamination due to scattering to the environment during use.
[0014]
As a prior art, lanthanum oxide (La 2 O 3 , melting point 2300 ° C.) is selected from rare earth elements as an alternative material for ThO 2 , and La 2 O 3 is dispersed in W by 0.4 to 1.2 mass%. Thus, a plate material having a high tensile strength even in a high temperature region has been proposed by forming a laminated structure of long crystal grains extending in the processing direction after recrystallization (see JP-A-11-152534).
[0015]
As described above, in the prior art, in order to obtain a plate material having a laminated structure of long and large crystal grains excellent in high temperature characteristics after recrystallization, plastic working at a high working rate is indispensable, and there is a limit to application to bulk and thick plates. is there.
[0016]
Therefore, one technical problem of the present invention is to provide a sintered body having excellent structure stability in which crystal grains are hardly coarsened even at high temperatures and a method for producing the same.
[0017]
Further, another technical object of this invention is to provide a tungsten plate material having fraud and mitigating risk higher high-temperature strength than the prior art products in a plate material subjected to plastic working the sintered body as a material.
[0018]
[Means for Solving the Problems]
According to the present invention, lanthanum oxide is 5 to 10% by mass, rhenium is 3 to 20% by mass, the balance is tungsten and inevitable impurities, the relative sintered body density is 99.2 to 99.9%, A tungsten sintered body having a grain size of 5.0 to 6.1 μm and maintaining a crystal grain size of 10 μm or less even when heated in vacuum at 2200 ° C. for 100 hours is obtained.
[0019]
Further, according to the present invention, there is provided a method for producing the tungsten sintered body, wherein after the lanthanum oxide is contained in the tungsten sintered body in an amount of 5 to 10% by mass in the blue oxide of tungsten, the tungsten sintered body is reduced, After adding and mixing the rhenium powder to the powder so as to contain 3 to 20% by mass in the tungsten sintered body, the relative sintered body density is 99.2 by using isotropic pressure sintering (HIP). A tungsten sintered body manufacturing method characterized by obtaining a tungsten sintered body comprising crystal grains of ˜99.9% and 5.0 to 6.1 μm is obtained.
[0020]
Further, according to the present invention, 5% by mass or more and 10% by mass or less of lanthanum oxide, 5% by mass or more and 20% by mass or less of rhenium and the balance are tungsten and inevitable impurities, and the tensile strength at 1000 ° C. is 405 MPa or more. A tungsten plate material having a pressure of 450 MPa or less is obtained.
[0021]
According to the present invention, there is also provided a method for producing the tungsten plate material, wherein the lanthanum oxide is added to the blue oxide of tungsten so that the tungsten sintered body contains 5 to 10% by mass, and then reduced. The rhenium powder was added to and mixed with the tungsten sintered body so as to contain 5 to 20% by mass, and then sintered using isotropic pressure sintering (HIP) to reduce the total plate thickness. A method for producing a tungsten plate material characterized by forging or rolling at 93% or more is obtained.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
First, the present invention will be described in more detail.
[0026]
In the present invention, in order to increase the high-temperature strength of the W material, in addition to the lanthanum oxide dispersion effect, improvement by solid solution strengthening of Re was aimed at.
[0027]
In order to uniformly and finely disperse the doped oxide in the W material, it is better to be upstream of the W material manufacturing process, that is, closer to the raw material. Examples of stable oxides include tungsten trioxide (WO 3 ) and blue oxide (W 4 O 11 ).
[0028]
In the present invention, a blue oxide having fine cracks on the surface of the oxide particles is considered to be superior in terms of controlling the amount of the doping element, and this is used.
[0029]
Doping elements are indispensable for improving high-temperature strength, but even if they are small, the effect cannot be exhibited, and if they are too large, the sintered density of the green compact is insufficient, and hot processing in the subsequent process becomes impossible. .
[0030]
Accordingly, in the present invention, a W compact having a La 2 O 3 addition amount of 5 to 10% and a solid solution strengthening element Re added to 3 to 20% is manufactured, and the sintered density of the sintered body is increased. For this reason, a sintered body made high-density using isotropic pressure sintering (HIP) after vacuum sintering was produced.
[0031]
Here, in the present invention, the reason that the maximum La 2 O 3 addition amount is set to 10% is that when the addition amount is further increased, the sintered density does not increase even when HIP is used.
[0032]
In the present invention, the Re amount is set to 3 to 20% because if it is 3% or less, the effect of solid solution strengthening is not exhibited. This is because it becomes unrealistic.
[0033]
Next, a specific example of a method for producing a W material according to an embodiment of the present invention and a material evaluation method will be described in comparison with a pure W material.
[0034]
(Material preparation method)
The W material according to the embodiment of the present invention is manufactured by a powder metallurgy method. An average particle size of 15 μm, high-purity blue W oxide powder (common name, typical composition formula W 4 O 11 , W purity 99.98%) was used as a raw material, and a predetermined amount of La 2 O 3 was dispersed therein. . A wet method was used to finely and uniformly disperse the oxide in the range of several tens of mass ppm to several mass%. First, La 2 O 3 is dissolved in reagent-grade nitric acid and then diluted with ethyl alcohol to prepare a dope stock solution having a La 2 O 3 concentration of 10 g / l. Into a porcelain evaporating dish, 1 liter of ethyl alcohol was metered, and a dope stock solution corresponding to the target dope amount was metered in with a mesburet, and the blue oxide (oxygen amount 19.4%) weighed in advance. ) Add 5,000 g and stir until it becomes slurry. The evaporating dish is placed on a dryer, and stirring is continued while heating to about 100 ° C., followed by drying until there is no odor of alcohol and cooling. The blue oxide returned to the original state becomes W oxide in which La 2 O 3 is dispersed.
[0035]
The dope W oxide is reduced in a hydrogen reduction furnace at 850 ° C. to obtain dope W powder. The average particle diameter of the dope W powder is 2.50 μm, the W purity is 99.95%, and the La 2 O 3 concentration is the same as that of the doped W oxide state.
[0036]
A predetermined amount of metal Re powder was added to and mixed with the dope W powder to which a predetermined amount of La 2 O 3 was added.
[0037]
The W-La 2 O 3 -Re powder thus obtained was filled in a rubber bag, sealed, vacuumed, and molded with an isostatic press. The molding pressure was 223 MPa. After this molded body was sintered in a vacuum sintering furnace at 2000 ° C. for 10 hours, HIP was performed under the condition of 2000 ° C.-196 MPa-3 hours to obtain a highly densified W alloy. Table 1 shows the density of the W sintered body produced in the present invention. When the structure of these sintered bodies obtained by the above method was confirmed, it had very fine crystal grains as compared with pure W. The measured crystal grain size is also shown in Table 1 below.
[0038]
[Table 1]
[0039]
The sintered body has a thickness of 15 mm, a width of 60 mm, and a length of 100 mm. The lanthanum oxide in the sintered body was distributed and existed in the grain boundary of the W sintered grains and in grains having an average grain size of submicron to 1 μm. In addition, when Re was examined for a solid solution state by EPMA, Re was found to be uniformly dissolved in the W matrix.
[0040]
These sintered bodies were cut into small pieces, subjected to heat treatment in vacuum at 2200 ° C. for 1 hour to a maximum of 100 hours, and the crystal grain size was measured to examine the structural stability by high-temperature heating. The relationship between the heating time and the crystal grain size is shown in FIG. As shown in FIG. 1, even when heating was performed at a temperature 200 ° C. higher than the sintering temperature for 100 hours, the crystal grains were hardly coarsened and fine crystal grains of 10 μm or less were retained.
[0041]
These sintered bodies were hot-rolled by the following procedure, and finished to a final thickness of 1 mm (total thickness reduction rate of 93%). In the initial stage of hot rolling, the heating temperature was 1300 ° C. to 1500 ° C., and the rolling rate per rolling pass was 15 to 30%. At the end of rolling, the heating temperature is 800 ° C to 1000 ° C, the rolling rate is 10 to 25%, and the surface of the plate is 1mm thick x 70mm wide x 600mm long (cut in half in the longitudinal direction in the middle to prevent rolling) A rolled plate covered with is obtained. This rolled plate was subjected to a strain relief annealing treatment in hydrogen at 1200 ° C. for 30 minutes, and then washed by pickling chemical treatment to form a metallic glossy plate, which was used as a tensile test material.
[0042]
A discharge wire processing machine was used for producing the tensile test piece. The test piece had a total length of 60 mm, a parallel part length of 30 mm, and a width of 4 mm. The parallel part was finally polished with No. 1500 emery paper to remove the deformation layer at the time of cutting.
[0043]
On the other hand, the production of the pure W material for comparison was performed following the same process except for the doping step.
[0044]
Both test pieces of the present invention and the comparative material were subjected to an annealing treatment in a vacuum at 1500 ° C. for 1 hour, and then subjected to a tensile test. The high temperature tensile test was performed at a strain rate of 5 × 10 −4 S −1 in a nitrogen atmosphere.
[0045]
FIG. 2 is a graph showing the relationship between the amount of Re and the tensile strength of the material of the present invention (W-10% La 2 O 3 -3 to 20% Re) at 1700 ° C. As shown in FIG. 2, the tensile strength of the material of the present invention to which La 2 O 3 and Re were added was higher than that of the comparative material. Furthermore, the tensile strength showed a higher value as the Re addition amount was increased.
[0046]
FIG. 3 is a diagram showing the relationship between the tensile strength and temperature of the material of the present invention (W-10% La 2 O 3 -20% Re) and the comparative material in a high temperature range of 1000 ° C. to 1700 ° C. As shown in FIG. 3, the tensile strength of the material of the present invention was about 2.5 times that of the comparative material in all the temperature ranges tested. Furthermore, even when compared with the W-1% La 2 O 3 plate proposed by the prior art (same conditions for rolling, etc.), high tensile strength was exhibited. In addition, Table 2 below shows examples of the strength of W plate materials having other compositions.
[0047]
[Table 2]
[0048]
【The invention's effect】
As described above, according to the present invention, lanthanum oxide and rhenium are uniformly dispersed and dissolved, thereby having very fine crystal grains as compared with pure W. It is possible to provide a very stable sintered body that does not cause crystal grain coarsening even at high temperature heating and a method for producing the same.
[0049]
Furthermore, according to the present invention can be provided as the material a sintered body described above, the novel tungsten plate contact and a manufacturing method thereof having high-temperature strength, for example 2.5 times.
[0050]
The lanthanum oxide used in the present invention is easier to handle than ThO 2 , has no radioactive contamination, and is a pollution-free material. Therefore, according to the present invention, the La 2 O 3 doping technology and the rolling technology of the dope sintered body are mass production-oriented, and are easily industrialized. manufacturing method of the plate material can be provided.
[0051]
Further, the tungsten sintered and plate material which has been subjected to plastic working them as a material according to the present invention have excellent structural stability and taking advantage of high temperature strength, high temperature brittleness, such as high-temperature furnace reflecting plate and the furnace for structural members, Ideal for applications requiring high temperature deformation resistance.
[0052]
Further, the tungsten sintered and plate material which has been subjected to plastic working them as a material according to the present invention has the excellent high-temperature strength, sagging under of high luminance electrode high temperature load and, high energy is input, resistance Consumability and heat distortion can also be improved.
[Brief description of the drawings]
FIG. 1 is a diagram showing the relationship between the heating time and the crystal grain size, although a sintered body according to an embodiment of the present invention was heat-treated at 2200 ° C. in a vacuum for 1 hour to 100 hours.
FIG. 2 is a diagram showing the relationship between the amount of Re and tensile strength in an annealed material (W-10% La 2 O 3 -3 to 20% Re) according to an embodiment of the present invention, and also as a comparative material A pure W annealed material is also shown.
FIG. 3 is a graph showing the relationship between test temperature and tensile strength in an annealed material (W-10% La 2 O 3 -20% Re) according to an embodiment of the present invention, and pure W as a comparative material. The annealed material is also shown.
Claims (4)
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