JP4246440B2 - Metal boride solid solution ceramics, method for producing the same, and liner using the same - Google Patents

Description

【００１０】
結果として、2ホウ化チタン単体より、総合的に硬度が高くかつ耐欠損性の指標である破壊靭性に優れ、ハンドリング性や焼結性に優れたセラミックス固溶体が存在することを見出した。特に、Ti_1-XMe_XB₂(ここで、MeはV、Nb、Ta、Cr及びMoの少なくとも1種、0.02≦x≦0.50)の組成である金属ホウ化物固溶体セラミックスに0.01〜0.20μmの炭化珪素焼結体破砕粉を0.1〜4.0質量%を含む金属ホウ化物固溶体セラミックス焼結体は、従来の高Cr鋼やサイアロンセラミックス製ライナーに比べて、耐摩耗性を高めつつ、かつチッピングや割れ等の耐欠損性を著しく改善できる。
【００１１】
2ホウ化バナジウム(VB₂)、2ホウ化ニオブ(NbB₂)、2ホウ化タンタル(TaB₂)、2ホウ化クロム(CrB₂)、2ホウ化モリブデン(MoB₂)から選ばれる少なくとも1種の金属ホウ化物を2ホウ化チタン(TiB₂)に固溶させると、TiB₂単体に比べ、硬度や破壊靭性値が総合的に上昇する。しかしながら、Ti_1-XMe_XB₂(Me=V、Nb、Ta、Cr及びMoの少なくとも1種)と表わした場合のxが0.02より小さい場合には、TiB₂への固溶効果が乏しくなり、十分な高硬度化が図れず、一方、xが0.50を越える場合にも幾つかの機械的な特性が低下する。
【００１２】
また、前記固溶体粒子の平均粒径は1〜10μmであることが望ましい。より好ましくは3〜5μmである。平均粒径が1μm未満の粒子では、用いる原料粉を1μm未満まで粉砕しなければならないが、経済性並びに粉砕時の不可避的混入物である表面の酸化層による物性低下の影響が大きく、一方、10μmより大きいと、硬さや破壊靭性値の低下を招く。
【００１３】
ホウ化チタン粉末、及び、2ホウ化バナジウム(VB₂)、2ホウ化ニオブ(NbB₂)、2ホウ化タンタル(TaB₂)、2ホウ化クロム(CrB₂)、2ホウ化モリブデン(MoB₂)から選ばれる少なくとも1種の金属ホウ化物は、粉砕に要する費用が高額で、かつ平均粒径2μm以下の微粉末では表面酸化層の影響が大きく、焼結性や焼結体の物性を著しく低下させるため、成形並びに焼結工程の直前に粉砕並びに整粒工程が必要となる。その際に炭化珪素の混合容器と混合用メディアを用い、粉砕、整粒、並びに混合工程で混入する粒径が0.01〜0.20μmの微細な炭化珪素焼結体破砕粉を0.1〜5質量%含有させることが不可欠であり、焼結性の向上を目的として添加する焼結助剤の炭化ホウ素粉末を焼結前に均一分散させることが有効である。
【００１４】
この炭化珪素焼結体からの微細な破砕粉は、硬質かつ耐酸化性のある高融点化合物であり、焼結後にホウ化チタン焼結体中に分散粒子として残留し、焼結体全体の硬度や破壊靭性値を向上させる作用を有する。ホウ化チタンと炭化珪素との熱膨張差やヤング率の相違等により、非常に微細な状態で分散した炭化珪素の近傍に残留応力が発生し、焼結体の破壊に際して破壊エネルギーを分散させる作用を有し、靭性を著しく向上させ、耐摩耗性も向上させる効果もある。
【００１５】
靭性の向上は、耐欠損性に効果があり、セラミックスの標準的な靭性の比較評価が可能なSEPB法(JIS-R-1607)による破壊靭性値で5MPa・m^1/2以上の高靭性を有することが好適である。また、耐摩耗性の指標であるビッカース硬度は、ダイヤモンド圧子を用い、押込み荷重98Nで2.4×10⁴MPa以上で摩耗が抑制される。
【００１６】
炭化珪素焼結体から混合時に混入する微細な破砕粉は0.01〜0.20μmが好ましく、その添加範囲は0.1〜4質量%が好ましく、より好ましくは2〜4質量%である。添加量の制御法としては混合メディアである炭化珪素ボール径、ミル回転数や混合時間によって、再現性よく行うことが可能である。
【００１７】
さらに、2ホウ化バナジウム、2ホウ化ニオブ、2ホウ化タンタル、2ホウ化クロム、2ホウ化モリブデンから選ばれる少なくとも1種の金属ホウ化物粉末を2〜50モル%、混合時に不可避的に混入する非常に微細なミル容器内壁並びに混合メディアの炭化珪素セラミックス破砕粉、及び残部が2ホウ化チタン及び不可避的不純物からなる混合粉末を、焼結した焼結体の密度は、理論密度に比して98%以上であることが望ましい。理論密度比98%未満では、硬さや破壊靭性の向上効果が十分とは言い切れない。
【００１８】
ここで、Ti-Me-B固溶体粒子(Meは、V、Nb、Ta、Cr及びMoの少なくとも1種)は、各種金属ホウ化物を個々に添加する以外に、例えば、複合ホウ化物粒子として添加したり、TiB2 にVC、NbC等の金属炭化物として所定量を混合しても、焼結時の反応により複合ホウ化物を形成することが可能である。また、Ti-Me-B固溶体粒子(Meは、V、Nb、Ta、Cr及びMoの少なくとも1種)の緻密化を促進するために焼結助剤として機能する炭化ホウ素、ホウ素含有有機物を添加することが望ましい。焼結助剤としては、炭化ホウ素、金属ホウ素とカーボンブラックの混合粉体や有機質炭素等の側鎖にホウ素を有する各種前駆体材料、等を用いることができる。焼結助剤である炭化ホウ素の添加量は、炭化ホウ素0.1〜2.0質量％が好ましい。
【００１９】
本発明の金属ホウ化物固溶体セラミックスの焼結設備は、特に限定するものではなく、前記2ホウ化バナジウム、2ホウ化ニオブ、2ホウ化タンタル、2ホウ化クロム、2ホウ化モリブデンから選ばれる少なくとも1種の金属ホウ化物粉末を2〜50モル%、混合する際に混合容器や混合メディアから混入する微細な炭化珪素破砕粉、及び残部が2ホウ化チタン及び不可避的不純物からなる混合粉末を、公知の各種焼結設備を用いることにより製造できる。
【００２０】
焼結方法としては、特に限定するものではなく、例えば真空焼結法、無加圧焼結法、ガス圧焼結法、熱間静水圧プレス焼結法、ホットプレス焼結法、等の各種焼結法を用いることができ、さらにこれらの焼結法を複数組み合せても良い。中でも、1.3×10^-2Pa以下の高真空下、1700〜2200℃の温度にて、4時間以上保持を行うと緻密な焼結体が得られ易い。十分な緻密化を図るために、アルゴン雰囲気下、100〜200MPaで、1650〜2150℃の温度にて2時間以上保持の熱間静水圧加圧(HIP)処理する二次焼結を行うことが好ましい。
【００２１】
一次の焼結条件としては、1.3×10^-2Pa以下の高真空度では緻密化が進行し易く、同時に安定した物性が得られ易く、また、焼結温度が1700℃未満では、緻密な焼結体が得られず、十分な硬さを付与することが困難となり、かつ高靭性の焼結体とすることができない。一方、焼結温度が2200℃を越える高温では、破砕粉として混入した炭化珪素が昇華、分解するため、焼結体が得られない。また、保持時間が4時間未満では、焼結反応による緻密化が十分には起こらないため、目的とする焼結体の特性が得られない。
【００２２】
二次の焼結条件としては、1650℃未満では、緻密化の効果が十分に得られない。
【００２３】
一方、2150℃を越える高温では、マトリックス粒子が異常成長するため、焼結体の特性が低下する恐れがある。また、保持時間が2時間未満では、緻密化が十分に進行しない。また、一次焼結時の最高温度と二次焼結の最高温度は50℃の差を設けて、二次焼結時を低くすることが好ましい。異常粒成長が起こらず、比較的短時間の処理により緻密化が促進されるので、焼結工程の歩留りが向上し、HIP装置への負担も軽減される。
【００２４】
高炉内部で用いられる各種耐磨耗部材、製鉄用焼結ラインのクラッシングガイドのストーンボックス、製鉄用コークス炉のバケットライナー等のライナー表層材料として、該セラミックス材を用いる場合、これを接合する鋼材の熱膨張率との差を少なくすることが必要となる。鋼材の熱膨張率は、インコネル等の超低熱膨張鋼を除けば、概ね6〜11×10^-6/K(室温〜800℃)の範囲内である。該セラミックスと一般的な熱膨張率を有する鋼材について、活性金属ろう付けを行う場合も、焼き嵌め又は冷やし嵌めを行う場合も、熱膨張率の近似したもの同志が好ましい。より詳しくは、ライナーの表層材料に用いるセラミックスの室温から800℃までの平均熱膨張率が6×10^-6/K以上で、既存の耐摩耗性ファインセラミックスの代表例であるサイアロンや炭化珪素やホウ化チタン単体より大きな熱膨張率を有し、鋼材の熱膨張率により近い値を有することが好ましい。ホウ化チタン(熱膨張率4.6〜5.2×10^-6/K)にホウ化ジルコニウム(熱膨張率5.9〜6.5×10^-6/K)又はホウ化ハフニウム(熱膨張率6.3〜6.8×10^-6/K)を固溶させても各単体の熱膨張率の差が少なく、ホウ化チタンの熱膨張率を6×10^-6/K以上に増大させることが難しい。
【００２５】
また、必要に応じ、本発明のTi-Me-B固溶体(Meは、V、Nb、Ta、Cr及びMoの少なくとも1種)の熱膨張率に近い、室温から800℃までの平均熱膨張率が6×10^-6〜11×10^-6/Kを有する鋼材を選択することにより、使用される環境温度での熱膨張率を適宜合わせられ十分な接合強度を得ることに繋がる。例えば、29Ni-17Co-Fe(Kovar)鋼、42Ni-Fe鋼等に、固相点800℃以下の金属ろうを用いてろう付け接合するか、鋼材に凹状の窪みを設けこれに焼き嵌めするか、又は凸状の突起を設けこれに冷やし嵌め接合するか、ボルト締めするか、クランプ固定するか、抜けを防止するためのテーパ加工した鋼棒をセラミックスに通して溶接固定するかのいずれかの方法を用いることが可能である。セラミックス材の平均熱膨張率が6×10^-6/K未満では、鋼材との接合に不具合が生じ易く、使用時に剥離が起きることがあり、好ましくない。
【００２６】
また、大面積のライナー材を分割して該セラミックス製平板をタイル状に配列する場合には、その間隔を極力狭めることによりセラミックス端部への負荷を軽減できる。さらに分割配列することで、損耗時の交換作業を安価に簡便にできる。該接合材を比較的安価な母材(SS400、Cr-Mo鋼等)に少なくとも2枚以上隣り合わせて、これらを楔やネジやクランプやスリット挿入等の機械止めにより固定したユニットをライナー部に埋設することが好適である。
【００２７】
本発明の焼結体を用いれば、製鉄用高炉のホッパーやベルから供給落下される鉄鉱石やコークスを高炉内部に分配する旋回シュート、ベルロッドウエアリング、ムーバブルアーマーライナー、鉱石受け金物に加え、製鉄用焼結ラインのクラッシングガイドに用いられるストーンボックス、製鉄用コークス炉バケットライナー等の耐摩耗性を高めることが可能になる。長寿命化による資材費の圧縮に加え、直接摺動する部材の他にも背面に位置する部材の破損を防ぎ、安定操業や高炉自体の炉命延長にも効果を発現することが期待される。
【００２８】
コスト面でもセラミックス材の肉厚を30mm以下に設定し、背面を鋼材に接合すればライナー単価が下がり、資材費の軽減も可能になる。加えて、該接合材をライナーに被覆する際には最も負荷が大きく、摩耗が激しい部位にのみ使用しても構わない。
【００２９】
【実施例】
次に、本発明の実施例を比較例と共に説明する。
(実施例1〜9)
2ホウ化チタン(TiB₂)粉末(平均粒径4.2μm)、2ホウ化バナジウム(VB₂)粉末(平均粒径5.5μm)、2ホウ化ニオブ(NbB₂)粉末(平均粒径4.8μm)、2ホウ化タンタル(TaB₂)粉末(平均粒径5.5μm)、2ホウ化クロム(CrB₂)粉末(平均粒径4.5μm)、2ホウ化モリブデン(NoB₂)粉末(平均粒径5.8μm)、炭化ニオブ(NbC)粉末(平均粒径5.0μm)、炭化バナジウム(VC)粉末(平均粒径5.5μm)、炭化タンタル(TaC)粉末(平均粒径4.5μm)、及び、炭化ホウ素(B₄C)粉末(平均粒径0.8μm)を第2表に示す所定量(質量%)添加し、分散媒としてエタノールを用い、炭化珪素セラミックスを内貼りしたボールミルにφ10mmの炭化珪素セラミックスボールを混合メディアとして用い、48時間混練した。エタノールの添加量は、投入したセラミックス粉末100gに対し60gの割合とした。
【００３０】
次いで、得られた混合粉末を成形後、焼結した。成形条件としては、冷間静水圧による加圧150MPaとし、縦70mm×横70mm×厚さ20mmを成形した。これを素地加工し、縦65mm×横65mm×厚さ15mmの平板形状の成形体を得た。焼結条件としては、1.0×10^-3Pa中にて、第2表中に示す温度で8時間保持の真空焼結を行った。必要に応じ、その後の二次焼結として同じく第2表中に示す温度、圧力のArガス雰囲気中にて3時間保持の熱間静水圧加圧(HIP)処理を行った。得られた焼結体から、縦50mm×横50mm×厚さ10mmの平板形状を研削加工し、落重試験による耐久性を評価した。
【００３１】
また、得られた焼結体から所定形状の試験片を切り出し、機械的特性を評価した。硬さは、押込荷重98Nにてビッカース硬さとして測定した。破壊靭性についてはJIS R 1607のSEPB法により室温にて破壊靭性値KIC を測定した。焼結体密度は、アルキメデス法により相対密度として測定した。また、X線回折法を用いて、混合前の原料粉末段階での各粉末のX線回折ピークをそれぞれ測定し、混合・成形し、焼結後の焼結体のX線回折ピークと照合したところ、TiB₂中にV、Nb、Ta、Cr、Moがそれぞれ固溶し、結晶格子のずれが生じていることを確認した。さらに、破砕混入した炭化珪素(SiC)についても、X線回折で同定され、混入量についてはボールミルとφ10mm炭化珪素ボールの摩耗量から求められ、本実施例ではいずれも原料投入量に対し、2〜3質量部（1.96〜2.91質量％）の混入量であった。
【００３２】
得られた各焼結体の諸特性を焼結体密度と共に第3表に示す。落重試験はセラミックス固溶体を厚さ0.5mmのカーボンシートを挿入した鋼材(SS400)に装着(端部を機械止め)し、質量3kgの鋼球(SS400)を10cm刻みに高さを上げながら実施した。最大200cmまでの試験後、各供試材の損傷有無、チッピング及びヒビ割れの深さを蛍光探傷法及び断面研磨面の光学顕微鏡観察により評価した。
(比較例10〜14)
比較例10〜14は、それぞれ高Cr鋼の場合(比較例10)、高Cr鋼に超硬(WC)粒子を鋳ぐるんだライナーを用いた場合(比較例11)、通常のサイアロンセラミックスを用いた場合(比較例12)の各比較例である。比較例13は，一般市販のボロン-カーボン系炭化珪素セラミックス単体(純度97質量%)、比較例14は、一般市販の2ホウ化チタンセラミックス単体(純度98質量%)の焼結体である。これらを併せて第2表及び第3表の比較例の欄に示す。また、これら比較例10〜14も実施例1〜9と同様の条件で落重試験を行った。
【００３３】
【表２】

【００３４】
【表３】

【００３５】
第3表に示すように、落重試験高さが僅か50cmにおいて比較例10、11では非可逆的なヘコミが生じ、50cm超に高さを増すにつれ、ヘコミが増大した。本発明の実施例1〜10によるものは、落重試験の最大高さが何れも150cm以上と比較例の12〜14の120cm以下に比べ高く、併せてヒビ割れやチッピング等の欠損も少ない傾向が確認された。また、ヤング率について、表中には記載しなかったが、2ホウ化チタン単体の550GPaに比べ、本発明の実施例は470〜530GPaと僅かながら低下しており、耐機械的衝撃性の向上の一因と考えることも可能である。したがって、機械的特性並びに落重試験のいずれも本発明の材質が総合的に良好な結果を得ることができた。
【００３６】
【発明の効果】
以上述べたように、本発明のTi_1-XMe_XB₂(ここで、MeはV、Nb、Ta、Cr及びMoの少なくとも1種、0.02≦x≦0.50)の組成である金属ホウ化物固溶体セラミックスに0.01〜0.20μmの炭化珪素焼結体破砕粉を0.1〜5.0質量%を含有してなる焼結体は、硬度や破壊靭性値に代表される機械的安定性に優れ、落重試験で高い耐久性を有する。
【００３７】
高炉内で塊状装入物の落下衝突による負荷の大きな各種部材の表層部のライナー、製鉄用焼結ラインのクラッシングガイドで用いられるストーンボックス、製鉄用コークス炉のバケットライナー等のライナー部材に本発明のセラミックス材を使用すれば、鉄鋼製造設備の長寿命化による資材費圧縮と、高炉、焼結炉、コークス炉等の安定操業による生産性向上に伴う製造コスト低減に寄与すること大である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a ceramic material excellent in wear resistance and fracture resistance and a method for producing the same.
[0002]
[Prior art]
Usually, when distributing blast furnace charges such as iron ore, lime, and coke to the furnace center, various cantilever members are used. However, the various members have a structure in which a liner for protecting the various members from the impact due to the fall of the charge and the wear due to the sliding after the contact is embedded in the surface layer portion of the member. The liner used for these various parts is made of cast steel of high Cr steel or high Cr steel + carbide (WC) particles, but the physical properties of the charge, drop speed, lump Due to impacts that depend on the size of the material, the wear is severe, especially because the surface layer liners of various components are subject to severe wear due to contact / impact of the charge. Therefore, it is necessary to replace or repair the various components, and this leads to an increase in maintenance and maintenance costs.
[0003]
[Problems to be solved by the invention]
Development of liner materials incorporating materials that improve wear resistance and service life has been desired. In order to distribute the blast furnace charge such as iron ore, lime, and coke to the inside of the blast furnace, the present invention is used in the liner of the surface layer portion of various members mounted in the blast furnace and the crushing guide of the sintering line for iron making. It is an object of the present invention to provide a novel ceramic material that improves the wear resistance and service life of a liner used for liner members such as a stone box and a bucket liner of a coke oven for iron making, and a method for producing the same.
[0004]
[Means for Solving the Problems]
In order to solve the above problems, the present inventors have intensively studied the characteristics of various ceramic sintered bodies. As a result, when specific ceramics are used, the liners for various members used inside the blast furnace, etc. The inventors have found that a sintered body having excellent characteristics as a material can be obtained, and have completed the present invention.
[0005]
That is, the present invention
(1) Ti _1-X Me _X B ₂ (where Me is at least one of V, Nb, Ta, Cr and Mo, 0.02 ≦ x ≦ 0.50). silicon carbide sintered body crushed powder of 0.20 [mu] m 0.1 to 4 .0 wt%, metal boride solid solution ceramics comprising a sintering aid and unavoidable impurities,
(2) The metal boride solid solution ceramic according to (1 ), wherein the sintering aid is a boron carbide compound and is contained in an amount of 0.1 to 2.0% by mass,
(3) The metal boride solid solution ceramics has a theoretical density ratio of 98% or more, a Vickers hardness of 2.4 × 10 ⁴ MPa or more, a fracture toughness value of 5 MPa · m ^1/2 or more, and 6 × 10 ⁻⁶ / K or more. ( 1 ) the metal boride solid solution ceramics having an average thermal expansion coefficient (room temperature to 800 ° C.) of
( 4 ) 2 to 50 at least one metal boride powder selected from vanadium diboride, niobium diboride, tantalum diboride, chromium diboride, and molybdenum diboride to titanium diboride powder. A mixed powder obtained by adding 0.1 to 5.0% by mass of a silicon carbide sintered powder of mol%, 0.01 to 0.20 μm and a sintering aid is added under a high vacuum of 1.3 × 10 ⁻² Pa or less or under an argon atmosphere. A method for producing a metal boride solid solution ceramic sintered at a temperature of 1700-2200 ° C. for 4 hours or more,
(5) The method for producing a metal boride solid solution ceramic according to (4), wherein the sintering aid is a boron carbide compound and is contained in an amount of 0.1 to 2.0% by mass,
(6) The titanium boride-based firing according to (4), wherein the pulverized powder of the silicon carbide sintered body is mixed from a mixing container, a mixing medium, or both of the mixing container and the mixing medium. A method for producing a knot.
(7) The method for producing a metal boride solid solution ceramic according to (4), further comprising hot isostatic pressing under an argon atmosphere at a temperature of 1650 to 2150 ° C. for 2 hours or more at 100 to 200 MPa.
( 8 ) A liner comprising the metal boride solid solution ceramic according to any one of (1) to (3) arranged on a surface layer portion,
It is.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in detail below.
[0007]
As a result of earnest analysis of the wear situation of the liners arranged on the surface layers of various members used when distributing blast furnace charges such as iron ore, lime and coke into the blast furnace, It was found that the surface layer that comes into contact with the inferior hardness material easily wears and breaks down and wears out when the material falls into a lump and collides. This wear and chipping were particularly noticeable when the hardness and fracture toughness of the liner material arranged on the surface layer of various members were low. Therefore, in order to use the liners arranged on the surface layer portions of various members stably for a long period of time, it is necessary to improve the wear resistance and fracture resistance at the same time. It is essential to use a ceramic material having
[0008]
Therefore, in order to improve these characteristics at the same time, among the various metal boride ceramics known for their high hardness, the unit cell, space group, and structural type are hexagonal, D ¹ _6h -P6 / _mmm , AlB Select a combination that is exactly the same for type ₂ and have very close lattice constants (Table 1), and confirm that each forms a solid solution by X-ray diffraction pattern, and then sequentially produce ceramic sintered bodies. The characteristics were evaluated.
[0009]
[Table 1]

[0010]
As a result, the present inventors have found that there is a ceramic solid solution that is generally higher in hardness, superior in fracture toughness, which is an index of fracture resistance, and superior in handling properties and sinterability than titanium diboride alone. In particular, a metal boride solid solution ceramic having a composition of Ti _1-X Me _X B ₂ (where Me is at least one of V, Nb, Ta, Cr and Mo, 0.02 ≦ x ≦ 0.50) is 0.01 to 0.20 μm. the metal boride solid solution ceramics sintered body containing 0.1 to 4.0 wt% silicon carbide sintered body crushed powder, as compared with the conventional high-Cr steel or siAlON ceramic liner, while enhancing the abrasion resistance, and The chipping and cracking resistance can be significantly improved.
[0011]
2 vanadium boride (VB _2), 2 niobium boride (NbB _2), 2 tantalum boride (TaB _2), 2 chromium borides (CrB _2), at least one selected from 2 molybdenum borides (MoB ₂₎ When the metal boride is solid-dissolved in titanium diboride (TiB ₂ ), the hardness and fracture toughness values are generally increased as compared with TiB ₂ alone. However, when x expressed as Ti _1-X Me _X B ₂ (Me = V, Nb, Ta, Cr and Mo) is smaller than 0.02, the solid solution effect on TiB ₂ is poor. As a result, sufficient hardness cannot be achieved. On the other hand, even when x exceeds 0.50, some mechanical properties deteriorate.
[0012]
The average particle size of the solid solution particles is preferably 1 to 10 μm. More preferably, it is 3-5 micrometers. In the case of particles having an average particle size of less than 1 μm, the raw material powder to be used must be pulverized to less than 1 μm. When it is larger than 10 μm, the hardness and fracture toughness value are lowered.
[0013]
Titanium boride powder, and vanadium diboride (VB ₂ ), niobium diboride (NbB ₂ ), tantalum diboride (TaB ₂ ), chromium diboride (CrB ₂ ), molybdenum diboride (MoB ₂ At least one metal boride selected from (1) has a high cost for pulverization, and a fine powder with an average particle size of 2 μm or less has a large effect on the surface oxide layer, and significantly improves the sinterability and physical properties of the sintered body. In order to reduce this, a pulverization and sizing process is required immediately before the molding and sintering processes. At that time, using a silicon carbide mixing container and mixing media, 0.1-5% by mass of fine silicon carbide sintered powder with a particle size of 0.01-0.20μm mixed in the grinding, sizing and mixing steps It is essential to uniformly disperse the boron carbide powder as a sintering aid added for the purpose of improving the sinterability before sintering.
[0014]
The fine crushed powder from this silicon carbide sintered body is a high melting point compound that is hard and has oxidation resistance, and remains as dispersed particles in the titanium boride sintered body after sintering. And has the effect of improving the fracture toughness value. Residual stress is generated in the vicinity of silicon carbide dispersed in a very fine state due to differences in thermal expansion and Young's modulus between titanium boride and silicon carbide. Has the effect of significantly improving toughness and improving wear resistance.
[0015]
Improved toughness has an effect on fracture resistance, and has a high toughness of 5 MPa ・ m ^1/2 or more in terms of fracture toughness according to the SEPB method (JIS-R-1607), which allows comparative evaluation of standard toughness of ceramics. It is suitable to have. In addition, the Vickers hardness, which is an index of wear resistance, uses a diamond indenter, and wear is suppressed at 2.4 × 10 ⁴ MPa or more at an indentation load of 98 N.
[0016]
The fine crushed powder mixed from the silicon carbide sintered body is preferably 0.01 to 0.20 μm, and the addition range is preferably 0.1 to 4 % by mass, more preferably 2 to 4% by mass. The addition amount can be controlled with good reproducibility according to the silicon carbide ball diameter, the mill rotation speed, and the mixing time, which are mixed media.
[0017]
Furthermore, 2 to 50 mol% of at least one metal boride powder selected from vanadium diboride, niobium diboride, tantalum diboride, chromium diboride and molybdenum diboride is inevitably mixed when mixed. The density of the sintered body is very small compared to the theoretical density, which is obtained by sintering a very fine mill container inner wall, silicon carbide ceramics pulverized powder of mixed media, and mixed powder consisting of titanium diboride and inevitable impurities in the balance. 98% or more is desirable. If the theoretical density ratio is less than 98%, it cannot be said that the effect of improving hardness and fracture toughness is sufficient.
[0018]
Here, Ti-Me-B solid solution particles (Me is at least one of V, Nb, Ta, Cr and Mo) are added as, for example, composite boride particles in addition to adding various metal borides individually. However, even when a predetermined amount of TiB2 is mixed as a metal carbide such as VC or NbC, a composite boride can be formed by a reaction during sintering. In addition, boron carbide that functions as a sintering aid and boron-containing organic substances are added to promote densification of Ti-Me-B solid solution particles (Me is at least one of V, Nb, Ta, Cr, and Mo). It is desirable to do. As the sintering aid, boron carbide, mixed powder of metal boron and carbon black, various precursor materials having boron in the side chain such as organic carbon, and the like can be used. The addition amount of boron carbide is a sintered aid, charcoal boron 0.1 to 2.0% by mass.
[0019]
The sintering equipment for the metal boride solid solution ceramics of the present invention is not particularly limited, and is at least selected from the vanadium diboride, niobium diboride, tantalum diboride, chromium diboride, and molybdenum diboride. 2 to 50 mol% of one kind of metal boride powder, fine silicon carbide crushed powder mixed from a mixing container or mixing medium when mixing, and a mixed powder consisting of titanium diboride and unavoidable impurities in the balance, It can manufacture by using well-known various sintering equipment.
[0020]
The sintering method is not particularly limited. For example, various methods such as vacuum sintering method, pressureless sintering method, gas pressure sintering method, hot isostatic pressing method, hot press sintering method, etc. Sintering methods can be used, and a plurality of these sintering methods may be combined. In particular, a dense sintered body can be easily obtained by holding at a temperature of 1700-2200 ° C. for 4 hours or more under a high vacuum of 1.3 × 10 ⁻² Pa or less. In order to achieve sufficient densification, secondary sintering by hot isostatic pressing (HIP) treatment at a temperature of 1650-2150 ° C for 2 hours or more at 100-200 MPa in an argon atmosphere may be performed. preferable.
[0021]
As the primary sintering conditions, densification tends to proceed at a high vacuum of 1.3 × 10 ⁻² Pa or less, and at the same time, stable physical properties can be easily obtained. A bonded body cannot be obtained, it is difficult to impart sufficient hardness, and a high-toughness sintered body cannot be obtained. On the other hand, when the sintering temperature exceeds 2200 ° C., silicon carbide mixed as crushed powder is sublimated and decomposed, so that a sintered body cannot be obtained. In addition, if the holding time is less than 4 hours, densification due to the sintering reaction does not occur sufficiently, so that the desired characteristics of the sintered body cannot be obtained.
[0022]
If the secondary sintering condition is less than 1650 ° C., the effect of densification cannot be sufficiently obtained.
[0023]
On the other hand, when the temperature exceeds 2150 ° C., the matrix particles grow abnormally, which may deteriorate the characteristics of the sintered body. Further, if the holding time is less than 2 hours, the densification does not proceed sufficiently. In addition, it is preferable that the maximum temperature during the primary sintering and the maximum temperature during the secondary sintering be set at a difference of 50 ° C. to reduce the time during the secondary sintering. Abnormal grain growth does not occur and densification is promoted by a relatively short processing time, so that the yield of the sintering process is improved and the burden on the HIP apparatus is reduced.
[0024]
Various wear-resistant members used inside blast furnaces, stone box for crushing guides for sintering lines for iron making, and steel materials for joining these ceramic materials as liner surface materials such as bucket liners for iron making coke ovens It is necessary to reduce the difference from the coefficient of thermal expansion. The thermal expansion coefficient of the steel material is generally in the range of ^{6 to} 11 × 10 ⁻⁶ / K (room temperature to 800 ° C.) except for ultra-low thermal expansion steel such as Inconel. For steel materials having a general thermal expansion coefficient with the ceramics, those having an approximate thermal expansion coefficient are preferable both when performing active metal brazing and when performing shrink fitting or cold fitting. More specifically, the average thermal expansion coefficient from room temperature to 800 ° C. of the ceramic used as the surface material of the liner is 6 × 10 ⁻⁶ / K or more, and typical examples of existing wear-resistant fine ceramics are sialon and silicon carbide. It preferably has a larger coefficient of thermal expansion than titanium boride alone and a value closer to the coefficient of thermal expansion of the steel material. Titanium boride (thermal expansion coefficient 4.6-5.2 × 10 ⁻⁶ / K) and zirconium boride (thermal expansion coefficient 5.9-6.5 × 10 ⁻⁶ / K) or hafnium boride (thermal expansion coefficient 6.3-6.8 × 10 ⁻⁶⁾ Even if it is dissolved, there is little difference in the thermal expansion coefficient of each single body, and it is difficult to increase the thermal expansion coefficient of titanium boride to 6 × 10 ⁻⁶ / K or more.
[0025]
If necessary, the average thermal expansion coefficient from room temperature to 800 ° C. is close to the thermal expansion coefficient of the Ti-Me-B solid solution of the present invention (Me is at least one of V, Nb, Ta, Cr and Mo). However, by selecting a steel material having 6 × 10 ^{−6 to} 11 × 10 ⁻⁶ / K, the thermal expansion coefficient at the ambient temperature to be used can be appropriately adjusted, and sufficient bonding strength can be obtained. For example, whether 29Ni-17Co-Fe (Kovar) steel, 42Ni-Fe steel, etc. should be brazed using a metal braze with a solidus point of 800 ° C or lower, or a concave recess should be provided in the steel material and shrink fit Either a convex protrusion is provided, and it is cold-fitted and joined, bolted, clamped, or a steel rod with a taper to prevent it from coming out is fixed by welding through ceramics. It is possible to use a method. If the average coefficient of thermal expansion of the ceramic material is less than 6 × 10 ⁻⁶ / K, it is not preferable because defects are likely to occur in joining with the steel material and peeling may occur during use.
[0026]
Further, when the large-area liner material is divided and the ceramic flat plates are arranged in a tile shape, the load on the ceramic end can be reduced by narrowing the interval as much as possible. Further, the replacement work at the time of wear can be simplified at low cost by dividing and arranging. A unit in which at least two of the bonding materials are placed next to a relatively inexpensive base material (SS400, Cr-Mo steel, etc.) and these are fixed by mechanical stops such as wedges, screws, clamps, slits, etc. is embedded in the liner section. It is preferable to do.
[0027]
If the sintered body of the present invention is used, in addition to the turning chute, bell rod wear ring, movable armor liner, ore receiving metal that distributes the iron ore and coke supplied and dropped from the hopper and bell of the blast furnace for iron making, It becomes possible to improve the wear resistance of a stone box, a coke oven bucket liner for iron making, etc. used for a crushing guide of a steel making sintering line. In addition to reducing material costs due to longer life, it is expected to prevent damage to members located on the backside of members that slide directly, and to be effective in stable operation and extending the life of the blast furnace itself. .
[0028]
In terms of cost, if the thickness of the ceramic material is set to 30 mm or less and the back surface is joined to the steel material, the unit price of the liner will be reduced, and material costs can be reduced. In addition, when the bonding material is coated on the liner, it may be used only in a portion where the load is greatest and the wear is severe.
[0029]
【Example】
Next, examples of the present invention will be described together with comparative examples.
(Examples 1 to 9 )
Titanium diboride (TiB ₂ ) powder (average particle size 4.2 μm), Vanadium diboride (VB ₂ ) powder (average particle size 5.5 μm), Niobium diboride (NbB ₂ ) powder (average particle size 4.8 μm) Tantalum diboride (TaB ₂ ) powder (average particle size 5.5 μm), chromium diboride (CrB ₂ ) powder (average particle size 4.5 μm), molybdenum diboride (NoB ₂ ) powder (average particle size 5.8 μm) ), Niobium carbide (NbC) powder (average particle size 5.0 μm), vanadium carbide (VC) powder (average particle size 5.5 μm), tantalum carbide (TaC) powder (average particle size 4.5 μm), and boron carbide (B ₄ C) Add a specified amount (mass%) of powder (average particle size 0.8μm) as shown in Table 2, use ethanol as a dispersion medium, and mix silicon carbide ceramic balls of φ10mm in a ball mill with silicon carbide ceramics attached inside. Used as media and kneaded for 48 hours. The amount of ethanol added was 60 g with respect to 100 g of the ceramic powder charged.
[0030]
Next, the obtained mixed powder was molded and then sintered. The molding conditions were a pressure of 150 MPa by cold isostatic pressure, and a length of 70 mm × width of 70 mm × thickness of 20 mm was formed. This was processed into a plate-shaped molded body of 65 mm length × 65 mm width × 15 mm thickness. As sintering conditions, vacuum sintering was performed in 1.0 × 10 ⁻³ Pa and held at the temperature shown in Table 2 for 8 hours. If necessary, hot isostatic pressing (HIP) treatment was performed for 3 hours in an Ar gas atmosphere having the temperature and pressure shown in Table 2 as the subsequent secondary sintering. From the obtained sintered body, a flat plate shape of 50 mm long × 50 mm wide × 10 mm thick was ground and evaluated for durability by drop weight test.
[0031]
Moreover, the test piece of the predetermined shape was cut out from the obtained sintered compact, and mechanical characteristics were evaluated. The hardness was measured as Vickers hardness at an indentation load of 98N. For fracture toughness, the fracture toughness value KIC was measured at room temperature by the SEPB method of JIS R 1607. The sintered body density was measured as a relative density by the Archimedes method. Also, using the X-ray diffraction method, the X-ray diffraction peak of each powder at the raw material powder stage before mixing was measured, mixed, molded, and collated with the X-ray diffraction peak of the sintered body after sintering However, it was confirmed that V, Nb, Ta, Cr, and Mo were dissolved in TiB ₂ and the crystal lattice was displaced. Further, silicon carbide (SiC) mixed and crushed was also identified by X-ray diffraction, and the mixing amount was determined from the wear amount of a ball mill and a φ10 mm silicon carbide ball. It was a mixing amount of ˜3 parts by mass (1.96 to 2.91% by mass) .
[0032]
Table 3 shows various characteristics of the obtained sintered bodies together with the sintered body density. The drop weight test was performed by attaching a ceramic solid solution to a steel material (SS400) with a carbon sheet with a thickness of 0.5 mm inserted (machined at the end) and increasing the height of a 3 kg steel ball (SS400) in 10 cm increments. did. After the test up to a maximum of 200 cm, each specimen was evaluated for the presence or absence of damage, the depth of chipping and cracking by the fluorescence flaw detection method and observation of the cross-section polished surface with an optical microscope.
(Comparative Example 1 0-1 4)
Comparative Example 1 0-1 4, in each case a high Cr steel (Comparative Example 1 0), when using a cemented carbide (WC) Liner's glove do cast particles in high Cr steel (Comparative Example 1 1), usually when using a siAlON ceramic is the comparative example (Comparative example 1 2). Comparative Example 1 3 generally commercially available boron - carbon-based silicon carbide ceramics alone (purity 97 wt%), Comparative Example 1 4, a sintered body of a general commercial diboride of titanium ceramics alone (purity 98 wt%) is there. These are also shown in the comparative example column of Tables 2 and 3. Also, it was drop weight test under the same conditions as those in Comparative Example 1 0-1 4 also Example 1-9.
[0033]
[Table 2]

[0034]
[Table 3]

[0035]
As shown in Table 3, drop weight test height is Comparative Example 1 0, 1 1, irreversible dents in slight 50cm occur, as increasing the height 50cm greater than dent is increased. By Examples 1 to 10 of the present invention, the maximum height of the drop weight test are both higher than that below 1 2-1 4 120cm the comparative example above 150 cm, even loss of cracking and chipping in conjunction A small tendency was confirmed. Further, the Young's modulus, although not described in the table, compared to 550G P a two titanium boride alone, embodiments of the present invention is slightly decreased and 470~530G P a, resistant mechanical It can also be considered as a cause of improvement in impact properties. Therefore, both the mechanical properties and drop weight test were able to obtain comprehensively good results with the material of the present invention.
[0036]
【The invention's effect】
As described above, the metal boride having a composition of Ti _1-X Me _X B ₂ of the present invention (where Me is at least one of V, Nb, Ta, Cr and Mo, 0.02 ≦ x ≦ 0.50). Sintered body containing 0.1 to 5.0 mass% of crushed silicon carbide sintered powder of 0.01 to 0.20 μm in solid solution ceramics is excellent in mechanical stability represented by hardness and fracture toughness values, and drop weight test High durability.
[0037]
Mainly used for liners such as liners on the surface layer of various parts that are heavily loaded due to falling impact of massive charge in the blast furnace, stone boxes used in crushing guides for sintering lines for iron making, bucket liners for coke ovens for iron making If the ceramic material of the invention is used, it will greatly contribute to the reduction of production costs due to the reduction of material costs by extending the life of steel production facilities and the improvement of productivity by stable operation of blast furnaces, sintering furnaces, coke ovens, etc. .

Claims (8)

To a metal boride solid solution ceramic having a composition of Ti _1-X Me _X B ₂ (where Me is at least one of V, Nb, Ta, Cr and Mo, 0.02 ≦ x ≦ 0.50), 0.01 to 0.20 μm. 0.1 to 4.0 wt% silicon carbide sintered body crushed powder, a sintering aid and the metal boride solid solution ceramics comprising unavoidable impurities. The metal boride solid solution ceramics according to claim 1, wherein the sintering aid is a boron carbide compound and is contained in an amount of 0.1 to 2.0 mass%. The metal boride solid solution ceramic has a theoretical density ratio of 98% or more, a Vickers hardness of 2.4 × 10 ⁴ MPa or more, a fracture toughness value of 5 MPa · m ^1/2 or more, and an average heat of 6 × 10 ⁻⁶ / K or more. The metal boride solid solution ceramics according to claim 1 or 2 , having an expansion coefficient (from room temperature to 800 ° C). 2 to 50 mol% of at least one metal boride powder selected from vanadium diboride, niobium diboride, tantalum diboride, chromium diboride, and molybdenum diboride to titanium diboride powder, 0.1 to 4.0 wt% silicon carbide sintered body crushed powder of 0.01～0.20Myuemu, and a mixed powder prepared by adding a sintering aid under a high vacuum of 1.3 × 10 ^-2 Pa or in an argon atmosphere, A method for producing metal boride solid solution ceramics which is sintered at a temperature of 1700-2200 ° C. for 4 hours or more. The method for producing a metal boride solid solution ceramic according to claim 4, wherein the sintering aid is a boron carbide compound and is contained in an amount of 0.1 to 2.0 mass%. 5. The method for producing a metal boride solid solution ceramic according to claim 4, wherein the silicon carbide sintered body pulverized powder is mixed from a mixed medium. Furthermore, the manufacturing method of the metal boride solid solution ceramics of Claim 4 which carries out a hot isostatic pressing process at a temperature of 1650-2150 degreeC for 2 hours or more by 100-200 MPa in argon atmosphere. The liner which arrange | positions the metal boride solid solution ceramics of any one of Claims 1-3 in the surface layer part.