JP3793644B2 - Multi-layer sleeve and die casting machine - Google Patents

Description

【００６３】
［純度９９％アルミナ−結晶性ｔ−ＢＮ複合焼結体：表２参照］
【００６４】
［試料８〜１２］
結晶性ｔ−ＢＮ微粉末と組み合わせて複合するセラミックス粉末にアルミナ粉末（純度９９．９９％、平均粒径０．４μｍの大明化学製）を選び複合セラミックス焼結体を試作した。但し、試料８においては結晶性ｔ−ＢＮ配合量をゼロ重量％とした。以下、この作製方法を詳細に説明する。
【００６５】
すなわち、このアルミナ粉末に水分重量２５％とポリカルボン酸アンモニューム塩の解こう剤を固形分０．６重量％添加してボールミルで１２時間分散混合して調製した。また、上記結晶性ｔ−ＢＮ微粉末に水分重量４５重量％とポリカルボン酸アンモニューム塩の解こう剤を固形分２重量％添加してボールミルで１２時間分散混合して調製した。その後、両者のスラリーを混合して結晶性ｔ−ＢＮ微粉末の配合量がゼロ重量％、１０重量％、１５重量％、２０重量％、２５重量％混合スラリーとし、各混合スラリーに成形助剤としてワックスバインダー及びポリビニールアルコール樹脂バインダーを固形分３重量％添加して、その後スプレードライヤーを用いて造粒粉を作製した。
【００６６】
この造粒粉末を金型プレス成形機で、１０００ｋｇ／ｃｍ²の成形圧力で加圧して成形体を得た。この成形体を還元雰囲気中で１３５０℃で２時間焼結して寸法が大凡１５ｃｍ×１５ｃｍ×２ｃｍの複合セラミックス焼結体を得た。
【００６７】
得られた各複合焼結体について測定した特性を表２にまとめて示した。試料９〜１２の各焼結体を粉砕して粉末Ｘ線回折で調べた結果、複合した窒化ホウ素粉末はすべて元の結晶性ｔ−ＢＮの状態で焼結体中に残存していた。
【００６８】
［試料１３、１４］
比較のため、同じアルミナ粉末に前記結晶性ｔ−ＢＮ微粉末を窒素雰囲気中で、４時間１７５０℃で加熱して得たｈ−ＢＮ粉末（平均粒径４．８μｍ、平均一次粒子径１．５μｍ、比表面積１２ｍ²／ｇの六角板状の結晶粒子からなる粉末）及びｈ−ＢＮ粉末（平均粒径約０．５μｍ、比表面積２５ｍ²／ｇの六角板状の結晶粒子からなる粉末）をそれぞれ１５重量％配合した混合スラリーを実施例１と同様にして複合セラミックス焼結体を作り（試料１３、１４）、その特性を表２に併せて示した。
【００６９】
なお、超硬バイトで切削加工を試みたところ、試料９〜１４のいずれの複合セラミックス焼結体についても良好な機械加工性があることが認められた。
【００７０】
【表２】

【００７１】
［窒化珪素−結晶性ｔ−ＢＮ複合焼結体：表３参照］
【００７２】
［試料１５〜１９］
結晶性ｔ−ＢＮ微粉末と組み合わせて複合するセラミックス粉末にα窒化けい素粉末（平均粒径０．６μｍ、比表面積２２ｍ²／ｇのＹ₂Ｏ₃を６重量％とＡｌ₂Ｏ₃を４重量％を含む秩父小野田製の窒化けい素粉末）を選び複合セラミックス焼結体を試作した。但し、試料１５においては結晶性ｔ−ＢＮ配合量をゼロ重量％とした。以下、この作製方法を詳細に説明する。
【００７３】
すなわち、この窒化けい素粉末に水分重量２５％とポリカルボン酸アンモニューム塩の解こう剤を固形分０．５重量％添加してボールミルで１２時間分散混合して調製した。また、上記結晶性ｔ−ＢＮ微粉末に水分重量４５重量％とポリカルボン酸アンモニューム塩の解こう剤を固形分２重量％添加してボールミルで１２時間分散混合して調製した。
【００７４】
その後、両者のスラリーを混合して結晶性ｔ−ＢＮ微粉末の配合量がゼロ重量％、１０重量％、１５重量％、２０重量％、２５重量％の混合スラリーとし、各混合スラリーに成形助剤としてワックスバインダー及びポリビニールアルコール樹脂バインダーを固形分３重量％添加して、その後スプレードライヤーを用いて造粒粉を作製した。
【００７５】
この造粒粉を金型プレス成形機で、１０００ｋｇ／ｃｍ²の成形圧力で加圧して成形体を得た。この成形体を窒素雰囲気中で１８００℃で５時間焼結して寸法が大凡１５ｃｍ×１５ｃｍ×２ｃｍの複合セラミックス焼結体を得た。
【００７６】
得られた各複合焼結体について測定した特性を表３に併せて示した。また実施例１６〜１９の各焼結体を粉砕して粉末Ｘ線回折で調べた結果、複合した窒化ホウ素粉末はすべてｈ−ＢＮ結晶に相転移していることが分かった。
【００７７】
［試料２０、２１］
比較のため、同じ窒化けい素粉末に前記結晶性ｔ−ＢＮ微粉末を窒素雰囲気中で、４時間１７５０℃で加熱して得たｈ−ＢＮ粉末（平均粒径約４．８μｍ、平均一次粒子径約１．５μｍ、比表面積１２ｍ²／ｇの六角板状の結晶粒子からなる粉末）及びｈ−ＢＮ粉末（平均粒径約０．５μｍ、比表面積２５ｍ²／ｇの六角板状の結晶粒子からなる粉末）をそれぞれ１５重量％配合した混合スラリーを試料１と同様にして複合セラミックス焼結体を作り（試料２０、２１）、その特性を表３に併せて示した。
【００７８】
なお、超硬バイトで切削加工を試みたところ、試料１６〜２１のいずれの複合セラミックス焼結体についても良好な機械加工性があることを認められた。
【００７９】
【表３】

【００８０】
［窒化アルミニウム−結晶性ｔ−ＢＮ複合焼結体：表４参照］
【００８１】
［試料２２〜２６］
結晶性ｔ−ＢＮ微粉末と組み合わせて複合するセラミックス粉末に窒化アルミニウム粉末（平均粒径１．４μｍ、比表面積２．７ｍ²／ｇのＹ₂Ｏ₃を５重量％含むダウケミカル製のアルミニウム粉末）を選び、複合セラミックス焼結体を試作した。但し、試料２２においては結晶性ｔ−ＢＮ配合量をゼロ重量％とした。以下、この作製方法を詳細に説明する。
【００８２】
すなわち、この窒化アルミニウム粉末にエチルアルコール重量４５％添加してボールミルで１２時間分散混合して調製した。また、上記結晶性ｔ−ＢＮ微粉末にエチルアルコール重量４５重量％添加してボールミルで１２時間分散混合して調製した。その後、両者のスラリーを混合して結晶性ｔ−ＢＮ微粉末の配合量がゼロ重量％、１０重量％、１５重量％、２０重量％、２５重量％の混合スラリーとし、各混合スラリーに成形助剤としてポリビニールブチラール樹脂バインダーを固形分３重量％添加して、その後スプレードライヤーを用いて造粒粉を作製した。
【００８３】
この造粒粉末を金型プレス成形機で、１０００ｋｇ／ｃｍ²の成形圧力で加圧して成形体を得た。この成形体を窒素雰囲気中で１８００℃で５時間焼結して寸法が大凡１５ｃｍ×１５ｃｍ×２ｃｍの複合セラミックス焼結体を得た。得られた各複合焼結体について測定した特性を表４に示した。また試料２３〜２６の各焼結体を粉砕して粉末Ｘ線回折で調べた結果、複合した窒化ホウ素粉末はすべてｈ−ＢＮ結晶に相転移していることが分かった。
【００８４】
比較のため、同じ窒化アルミニウム粉末に前記結晶性ｔ−ＢＮ微粉末を窒素雰囲気中で、４時間１７５０℃で加熱して得たｈ−ＢＮ粉末（平均粒径４．８μｍ、平均一次粒子径１．５μｍ、比表面積１２ｍ²／ｇの六角板状の結晶粒子からなる粉末）及びｈ−ＢＮ粉末（平均粒径０．５μｍ、比表面積２５ｍ²／ｇの六角板状の結晶粒子からなる粉末）をそれぞれ１５重量％配合した混合スラリーを実施例１と同様にして複合セラミックス焼結体を作り（試料２７、２８）、その特性を表４に併せて示した。
【００８５】
なお、超硬バイトで切削加工を試みたところ、試料２３〜２８のいずれの複合セラミックス焼結体についても良好な機械加工性があることを認めた。
【００８６】
【表４】

【００８７】
なお、上記の試料１〜２８の内、試料２〜５、試料９〜１２、試料１６〜１９、及び試料２３〜２６は、原料中に結晶性ｔ−ＢＮが含まれる。一方、試料１、試料８、試料１５及び試料２２は、原料中に元から結晶性ｔ−ＢＮが配合されていない。また、試料６、７、試料１３、１４、試料２０、２１及び試料２７、２８においては、予備熱処理によって、結晶性ｔ−ＢＮをｈ−ＢＮに転移した原料粉末を用いているため、焼結体中には結晶性ｔ−ＢＮが含まれない。
【００８８】
上記表１〜４に示した結果から、本発明による結晶性ｔ−ＢＮ微粉末を混合して焼結した複合セラミックス焼結体は、ｈ−ＢＮ粉末を混合して焼結した複合セラミックス焼結体と比較して焼結性がよく、曲げ強度が大きいことが分かる。
【００８９】
また、窒化硼素（結晶性ｔ−ＢＮ）を２０重量％複合した焼結体について熱膨張率を測定したところ、結晶性ｔ−ＢＮ微粉末を混合して焼結した複合セラミックス焼結体の厚さ方向と厚さに直角な方向の熱膨張率の比はほぼ１であり、成形時の加圧方向による方向性がの差異が殆どないことが分かった。また、窒化珪素を含有することによって、特に高温での強度が向上する。これらの性質は、高温の溶湯が断続的に流れるようなスリーブとして、好ましい性質である。
【００９０】
また、表１〜表４を参照して、結晶性ｔ−ＢＮの配合量が少ないほど、気孔率の低い緻密な焼結体が得られ、強度が高くなり、一方、結晶性ｔ−ＢＮの配合量が多いほど気孔率が高く、断熱性ないし保温性に優れ、熱膨張率が等方性であり、耐熱衝撃性の高い焼結体が得られることが分かる。
【００９１】
また、図６に、表３に示した結晶性ｔ−ＢＮ微粉末と窒化珪素粉末とを混合した粉末を焼結した窒化珪素質ＢＮ焼結体と同様の方法で作製した窒化珪素質ＢＮ焼結体における、原料中の結晶性ｔ−ＢＮの含有量と、焼結体中の気孔率の関係を示す。図６中、下方の折れ線が、同じＢＮ含有量の焼結体のうち最小の気孔率を示し、上方の折れ線が、同じＢＮ含有量の焼結体のうち最大の気孔率を示す。
【００９２】
図６より、結晶性ｔ−ＢＮ含有量を変化させることによって、焼結体の気孔率を制御可能であることが分かる。例えば、結晶性ｔ−ＢＮ含有量の設定によって、ダイカストマシンのプランジャスリーブ用材料として、ガス抜け特性などを最適化できることが分かる。
【００９３】
なお、結晶性ｔ−ＢＮ微粉末は非常に細かい結晶であり、一般に凝集していることが多い。したがって、成形の原料調製過程で、いかに凝集紛体を分散してマトリクスとなる原料と均一に混合するかが最終的な焼結体特性に大きく影響してくる。本発明の製造工程において、混合する粉体を個々に均一分散する処理をすることにより特性が大きく変わることを留意しておく必要がある。このようにして従来のｈ−ＢＮを用いた場合よりも、所定強度を達するために、より多量のＢＮ成分を焼結体に含有させることができる。一方、同じ気孔率であっても組織の緻密化と高強度化を達成することができる。
【００９４】
次に、本発明の基礎となる発明の実施例に係るスリーブを説明する。このスリーブは、内筒が一層構造の窒化珪素質ＢＮ焼結体の一層構造であり、外筒がメタルスリーブからなる。以下、このスリーブの製造方法及び構造を説明する。
【００９５】
表３に示した上述の試料２３と同様の焼結体を材料として、ダイカストマシンのプランジャスリーブを作製した。図７は、本発明の基礎となる発明の実施例に係るスリーブを内筒に用いたプランジャスリーブの構造を示す斜視図であり、図８（Ａ）は図７のプランジャスリーブの軸方向断面図であり、図８（Ｂ）は図７のプランジャスリーブの側面図である。
【００９６】
図７、図８（Ａ）及び図８（Ｂ）を参照して、プランジャスリーブ１００は、本発明の基礎となる発明の実施例に係るスリーブからなる薄肉の内筒２００と、内筒２００が嵌挿された耐熱鋼製の外筒３００からなる。内筒２００は機械的加工性がよく寸法精度が高く、熱膨張率の等方性により耐熱衝撃性が高いため、焼きばめせずに内筒２００と外筒３００を一体化することができる。内筒２００と外筒３００の一端部には、溶湯を導入するための孔４００が開けられている。プランジャスリーブ１００の他端部にはフランジが形成され、ダイカストマシンのプラテンに取り付けられる。このプラテンは、固定ダイに当接し、互いに型締めされた固定ダイと可動ダイの間の鋳型に、プランジャスリーブ１００内をストロークするプランジャヘッドによって押し出された溶湯が供給される。
【００９７】
［ダイカスト試験］
以上説明したプランジャスリーブを適用したダイカストマシンを用いて、溶湯温度を下記のように代えて、アルミニウム合金を鋳造した。プランジャスリーブ１００（図７参照）の寸法は、外径１５０φ×内径８０φ×長さ５２８Ｌ、内筒２００（図８（Ａ）参照）の厚さを１０ｍｍｔとした。また、比較のため、耐熱鋼製のメタルスリーブ単層のプランジャスリーブを用いて、同様に鋳造を行った。鋳造条件は下記のとおりである。
【００９８】
材質：ＡＤＣ１０、溶湯温度：６５０〜７１０℃、潤滑剤：黒鉛含有潤滑剤。
【００９９】
［評価結果］
表５に、本発明の一実施例に係るスリーブを用いたプランジャスリーブと、比較例に係る耐熱鋼製メタルスリーブの評価結果を示す。なお、表５中の局部加圧とは、鋳造品の密度と寸法精度向上を図るために、型キャビティ内に溶湯が凝固する寸前に加圧中子を挿入するものである。
【０１００】
【表５】

【０１０１】
表５より、本実施例に係る結晶性ｔ−ＢＮ複合焼結体製の内筒を備えたプランジャスリーブを用いたダイカストマシンによる製品の方が、３点曲げ強度が優れていることが分かる。さらに、断熱性がよく、したがって溶湯の保温性も高いことが分かる。
【０１０２】
また、得られた製品の破断面チル層を観察した結果、結晶性ｔ−ＢＮ複合焼結体製の内筒を備えたプランジャスリーブを用いたダイカストマシンによる製品の方が、均質な破断面となっていることが分かった。
【０１０３】
また、このプランジャスリーブ用いて耐久試験を行った結果、５０００ショットでスリーブ内周面の摩耗がわずか４μｍであった。これは、このプランジャスリーブの内筒の潤滑性、耐溶損性が優れていることを示している。
【０１０４】
なお、結晶性ｔ−ＢＮ複合焼結体の内筒の一端又は両端に、組立時又は運搬時の取り扱いの容易性を考慮して、金属製のリングを取り付けてもよい。下記の実施例においても同様である。
【０１０５】
次に、本発明の一実施例に係る軸方向に複層構造を有するスリーブを説明する。このスリーブは、上述の表１〜４に示した、結晶性ｔ−ＢＮ微粉末と他種のセラミック粉末を焼結してなるＢＮ複合焼結体からなるものである。そして、特に、ダイカストマシンのプランジャスリーブに適用されるものである。
【０１０６】
図９は、本発明の一実施例に係る軸方向に２層構造を有するスリーブの軸方向断面図である。
【０１０７】
図９を参照して、このスリーブは、高温の溶湯がへ導入される上流部に、ＢＮ含有率が高いＢＮ高含有率層１を配し、下流部にＢＮ含有率が低いＢＮ低含有率層２を配し、両層１，２を軸方向に接合したものである。なお、両層１，２は、接着、締結などの方法によらず、ＢＮ含有率が段階的に異なる成形体を一体焼成により接合することもでき、或いは、連続的（傾斜的）にＢＮ含有率が異なる成形体を焼成して得ることもできる。
【０１０８】
ＢＮ高含有率層は、例えば、上述の表３を参照して、気孔度が高く、断熱性ないし保温性に優れ、また、熱膨張に関してより等方性が強いため、耐熱衝撃性が高い。一方、ＢＮ低含有率層は、同様に表３を参照して、気孔度が低く、緻密であるため、強度が高いという特性を有する。
【０１０９】
よって、高温の溶湯が導入されるスリーブの上流部に耐熱衝撃性の高いＢＮ高含有率層１を配し、溶湯を金型に押し出す際に高い圧力が加わる下流部に高強度のＢＮ低含有率層２を配することにより、耐熱衝撃性と強度のバランスが優れたスリーブが提供され、加えて溶湯温度、押し出し圧力などに関する鋳造条件の制限を緩和される。
【０１１０】
以上説明した軸方向に２層構造を有するスリーブを内筒として、メタル製などの外筒スリーブに嵌挿してもよい。図１０は、図８に示したＢＮ高含有率層１とＢＮ低含有率層２を軸方向に接合した内筒スリーブを、外筒となるメタルスリーブ３内に嵌挿したものである。
【０１１１】
次に、本発明の他の実施例に係る軸方向に３層構造を有するスリーブを説明する。
【０１１２】
図１１は、本発明の他の実施例に係る軸方向に３層構造を有するスリーブの軸方向断面図である。
【０１１３】
図１１を参照して、このスリーブは、高温の溶湯がへ導入される上流部に、ＢＮ含有率が高いＢＮ高含有率層１０を配し、中間部にＢＮ中含有率層１１、下流部にＢＮ含有率が低いＢＮ低含有率層１２を配し、３層１０，１１，１２を軸方向に互いに接合したものである。斯くして、さらに、強度と耐熱衝撃性のバランスが改善される。
【０１１４】
【発明の効果】
本発明によれば、断熱性ないし保温性が高く、強度と耐熱衝撃性のバランスが優れたスリーブが提供される。本発明によるスリーブは、ダイカストマシンのプランジャスリーブとして有用であり、溶湯温度、溶湯の押し出し圧力などに関する鋳造条件の制限を緩和するものである。
【０１１５】
また、本発明は、新規な結晶性乱層構造窒化硼素の用途を開発するものである。この新規な結晶性乱層構造窒化硼素を用いた本発明によるスリーブは、断熱性ないし保温性が高く、強度が高く、熱膨張が等方性で耐熱衝撃性が高く、潤滑性がよく、ガス抜け性がよく、溶融金属に対して濡れにくく、機械加工性がよい、という特性を有する。このようなスリーブは、ダイカストマシンのプランジャスリーブ用材料としてきわめて優れた特性を有するものであって、鋳造品における欠陥の発生が減少されると共に、断熱性の高さにより作業環境温度が低下される。
【０１１６】
上記特性が得られる理由は、上記スリーブが、結晶性ｔ−ＢＮ粉末、又はそれと他種のセラミックス粉末を原料粉末として用いるためである。詳細には、結晶性ｔ−ＢＮ粉末の一次粒子が微細な結晶粒子であること、結晶性ｔ−ＢＮ粉末が乱層構造を有することによって、このスリーブは、規則的なｈ−ＢＮ粉末を原料粉末に用いた場合より焼結性がよく、強度が高く、熱膨張の方向性が小さくなる。
【０１１７】
さらに、焼結体中に結晶性ｔ−ＢＮが相転移しないでとどまっている限りにおいて結晶性ｔ−ＢＮは微細な結晶粒子の状態を保持しており、これによって焼結体中の気孔も微細になる。また、焼結体の組織が微細であることによって強度が大きい焼結体になる。これは、結晶性ｔ−ＢＮが焼結過程でｈ−ＢＮに変化する場合にもほぼ妥当する。このように、気孔が微細に分散していることによって、ガス抜け性が向上する。
【０１１８】
さらに、上記スリーブは、従来のｈ−ＢＮ粉末を原料に用いた複合セラミックス焼結体にも勝る優れた機械加工性（切削加工性）、熱伝導性、電気絶縁性、耐熱衝撃性等の他、溶融金属に対する濡れにくさと耐食性等の好ましい特性を兼備している。
【０１１９】
このような好ましい特性を有する上記スリーブは、無加圧焼結によって製造できる。前述した結晶性ｔ−ＢＮ微粉末の製造技術が確立されたことによって従来より格段に安価に高純度の結晶性ｔ−ＢＮ微粉末を調達できるようになった。
【０１２０】
上記スリーブは、機械加工性がよいため、これを用いて複雑な形状の高精度のスリーブを安価に提供できる。また、本発明によるスリーブは、高強度を必要とする構造用スリーブ、耐久性のある通気性多孔質溶融金属用鋳型用スリーブ、溶融金属と接触する保護スリーブなどの耐熱衝撃性を必要とするスリーブ用の材料として好適である。結晶性ｔ−ＢＮ（或いは結晶性ｔ−ＢＮに由来する微細分散ｈ−ＢＮ）の含有により複合セラミックス焼結体に高い滑り特性を与えることができ、この特性を任意の所望値に制御、調節することもできる。また、本発明は溶湯を保持又は流通させるための容器や給湯管（図１２参照）にも好適に適用される。
【図面の簡単な説明】
【図１】従来の典型的なｈ−ＢＮ粉末の粉末Ｘ線回折図である。
【図２】従来のａ−ＢＮ粉末の粉末Ｘ線回折図である。
【図３】本発明の一実施例に係るスリーブの原料として用いられる結晶性ｔ−ＢＮ微粉末の粉末Ｘ線回折図である。
【図４】図３の結晶性ｔ−ＢＮ微粉末の電子顕微鏡写真である。
【図５】本発明の一実施例に係るスリーブの原料として用いられる結晶性ｔ−ＢＮ微粉末のアトリションミルによる粉砕後の粒度分布を示すグラフである。
【図６】本発明の一実施例に係るスリーブの材料となる焼結体において、原料中の結晶性ｔ−ＢＮの含有量と、焼結体中の気孔率の関係を説明するためのグラフである。
【図７】本発明の基礎となる発明の実施例に係るプランジャスリーブの構造を示す斜視図である。
【図８】（Ａ）は図７のプランジャスリーブの断面図であり、（Ｂ）は同側面図である。
【図９】本発明の一実施例に係る軸方向に２層構造を有するスリーブの軸方向断面図である。
【図１０】図９のスリーブを外筒に嵌挿しスリーブの軸方向断面図である。
【図１１】本発明の他の実施例に係る軸方向に３層構造を有するスリーブの軸方向断面図である。
【図１２】本発明の応用例に係る給湯管を示す斜視図である。
【符号の説明】
１ ＢＮ高含有率層
２ ＢＮ低含有率層
３ メタルスリーブ
１０ ＢＮ高含有率層
１１ ＢＮ中含有率層
１２ ＢＮ低含有率層
１００ プランジャスリーブ
２００ 結晶性ｔ−ＢＮ粉末複合焼結体製内筒
３００ 耐熱鋼製外筒
４００ 孔[0001]
BACKGROUND OF THE INVENTION
  The present invention is a sleeve.And die casting machineIn particular, the present invention relates to a plunger sleeve of a die casting machine.
[0002]
[Prior art]
Conventionally, as a plunger sleeve of a die-cast machine, Japanese Patent Laid-Open No. 7-46807 discloses an outer cylinder in which an inner cylinder is formed from a porous body such as cermet in order to vent gas from a molten metal, and this inner cylinder is fitted. Has been proposed which is formed from a cast metal material. The inner cylinder and the outer cylinder are integrated by shrink fitting.
[0003]
Japanese Patent Laid-Open No. 8-243711 discloses a single-layer cylindrical member made of tool steel at the upstream portion, a porous portion at the inner peripheral portion at the downstream portion, and a radial multi-layer cylindrical member at the outer peripheral portion made of a metal body. The plunger sleeve which joined the single layer cylindrical member and the radial direction multilayer member in the axial direction is disclosed.
[0004]
[Problems to be solved by the invention]
However, the heat retaining property or heat insulating property of the plunger sleeve of the die cast machine proposed in the above-mentioned Japanese Patent Laid-Open No. 8-243711 does not necessarily satisfy the user, and causes a product defect due to a decrease in the temperature of the molten metal. There is a point. In addition, the metal outer cylinder may be overheated.
[0005]
Also, in the plunger sleeve proposed in the above-mentioned JP-A-8-243711, in which the single-layer cylindrical member and the radial multilayer member are joined in the axial direction, a metal single-layer cylindrical member is used in the upstream portion. Therefore, there are problems as described above. Furthermore, in the downstream multi-layer member, the strength and thermal shock resistance are not sufficient, and the casting conditions are limited.
[0006]
  An object of the present invention is to provide a sleeve having high heat insulation or heat retention and excellent balance between strength and thermal shock resistance.In addition, an object of the present invention is to provide a die casting machine using the sleeve.Another object of the present invention is to develop a new crystalline turbostratic boron nitride application.
[0007]
[Means for Solving the Problems]
  The sleeve according to the invention is,axisAlong the directionThe content of crystalline boron layer boron nitride isA plurality of different layers are provided.The die casting machine according to the present invention uses the sleeve as a plunger sleeve which is a flow path for injecting molten metal into the mold.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described.
[0009]
  First, in the preferred embodiment of the present invention, various types of ceramics can be used as the sleeve material. In particular, composite ceramics containing boron nitride, especially crystalline turbulent layer nitriding.boronA composite ceramic containing fine powder as a sintering raw material is used.
[0010]
  First, crystal turbulent layer nitridingboronA novel sintered body made from the above and a method for producing the same will be described. In addition, the polymorph of boron nitride will be described.
[0011]
Boron nitride (BN) is a compound composed of boron and nitrogen, but there are polymorphs having substantially the same crystal structure as carbon. That is, amorphous boron nitride (hereinafter referred to as “a-BN”) and hexagonal boron nitride (hereinafter referred to as “h-BN”) having a structure in which hexagonal network layers are laminated in a two-layer cycle are used as boron nitride. ), Rhombohedral boron nitride (hereinafter referred to as “r-BN”) having a structure in which hexagonal meshes are laminated in a three-layer cycle, and turbulent structure nitriding having a structure in which hexagonal mesh layers are randomly laminated. Boron (hereinafter referred to as “t-BN”), zinc blend type boron nitride (hereinafter referred to as “c-BN”) and wurtzite type boron nitride (hereinafter referred to as “w-BN”), which are stable phases under high pressure, Are known.
[0012]
Among the above polymorphs of boron nitride, only h-BN and c-BN are recognized as practical materials as conventional materials. h-BN is a stable phase that is superior in oxidation resistance to graphite, and the synthesized crystalline h-BN powder particles usually have a hexagonal plate-like self-shape. , Mechanical workability (cutting workability) and solid lubricity, but unlike graphite, it is white and has excellent insulation. On the other hand, since a-BN is unstable and hygroscopic, it cannot be used in the state of a-BN. The powder X-ray diffraction patterns of typical h-BN and a-BN with CuKα rays are shown in FIGS.
[0013]
As can be seen from FIG. 1, diffraction lines [002], [100], [101], [102] and [004] are prominent in the powder X-ray diffraction pattern of h-BN. On the other hand, in the powder X-ray diffraction diagram of a-BN in FIG. 2, [100] and [101] diffraction at the positions of the [100] diffraction line and the [101] diffraction line of the powder X-ray diffraction diagram of h-BN. There is only a broad diffraction line with a combined line and a broad diffraction line at the position of the [002] diffraction line in the powder X-ray diffraction diagram of h-BN. There are only weak diffraction lines that are broad and unclear even if they exist. In the structure of a-BN, the hexagonal network layer composed of boron and nitrogen is not developed, and the laminated structure of the minute hexagonal network layer that is not developed does not have regularity.
[0014]
The crystal of h-BN has a crystal structure in which developed hexagonal network layers composed of boron and nitrogen are laminated in a pattern of aa'aa'aa'aa'a ... The layer laminated with is r-BN. On the other hand, a hexagonal network layer that has developed but has no regularity in the laminated structure of the hexagonal network layer is referred to as t-BN. An example of the powder X-ray diffraction pattern of t-BN is shown in FIG. As can be seen from FIG. 3, in this powder X-ray diffraction diagram, diffraction lines corresponding to [002] and [004] diffraction lines of the h-BN powder X-ray diffraction diagram are sharp diffraction lines. 100] Diffraction lines corresponding to [102] do not exist because diffraction lines corresponding to [101] are weak and inconspicuous because the diffraction lines corresponding to the diffraction lines are widened with a skirt on the high angle side. Even if it exists, it is very weak. The diffraction line corresponding to [102] is a diffraction line that appears only when the hexagonal mesh layers are regularly stacked.
[0015]
The Journal of Resources and Materials, Vol. 105 (1989) no. 2, P201 to 204 describe boron nitride whose powder X-ray diffraction diagram shows only a broad diffraction line as t-BN. Such boron nitride is a-BN as distinguished from t-BN. It is reasonable to do.
[0016]
The following are known examples of conventional composite ceramic sintered bodies containing boron nitride. JP-A-60-195059, JP-A-60-195060 and JP-A-2-2526262 are machinables (machine workability or cutting workability) in which h-BN powder is combined with aluminum nitride and thermal conductivity. A large composite ceramic sintered body is disclosed. JP-B-5-65467 and JP-A-1-305861 disclose high strength containing h-BN in which boron nitride is combined with aluminum nitride, silicon nitride or silicon carbide using a-BN powder as a raw material. A composite ceramic sintered body having good machinability is disclosed.
[0017]
In JP-A-7-330421, porous ceramics made of oxide, nitride, carbide, etc. are impregnated with an aqueous boric acid solution, dried, heated and reduced and nitrided in an ammonia atmosphere, and porous. Boron nitride (presumed to be a-BN at this stage from the heating temperature) is produced in the sintered material. Next, this was sintered at the sintering temperature of the base material, and various composite ceramic sintered bodies having high strength containing h-BN particles in which a-BN phase changed to h-BN simultaneously with sintering were obtained. In the case of this method, in order to obtain a composite ceramic sintered body in which a relatively large amount of boron nitride is combined, it is necessary to repeat the steps of impregnation, drying and nitriding, which is complicated.
[0018]
Of the boron nitrides excluding c-BN and w-BN, which are stable crystal phases under high pressure, from the various boron nitrides mentioned above, reports on very small amounts of t-BN and r-BN have been synthesized in the laboratory. (See, for example, Journal of Solid State Chemistry Vol. 109, No. 2, p384-390 (1994)), and as far as the present inventors know, crystalline t-BN fine powder was used as a raw material. A composite sintered body or a composite sintered body containing crystalline t-BN is not yet known.
[0019]
Therefore, the present inventors have proposed a method for producing crystalline t-BN fine powder having excellent productivity in Japanese Patent Application No. 9-21052 filed earlier. Further, the inventors of the present invention have a characteristic that the crystalline t-BN fine powder described in Japanese Patent Application No. 9-21052 is inactive in moisture and is crystalline in Japanese Patent Application No. 10-152020. Production of inexpensive and useful composite ceramic sintered body using crystalline t-BN fine powder with fine particle size (same as primary particle size), uniform primary particle size and good sinterability A method was proposed, and in addition, a high-performance composite ceramic sintered body using a novel crystalline BN fine powder was also proposed.
[0020]
Furthermore, the present inventors intend to provide a novel sleeve and sleeve structure using a novel crystalline t-BN.
[0021]
In a preferred embodiment, the sleeve of the present invention and the method for producing the sleeve are formed by sintering a ceramic mixture in which an effective amount, in particular, 5% by weight or more of crystalline t-BN fine powder is mixed with other ceramic raw materials. The effective amount of crystalline t-BN is determined according to the required purpose, but can be set from about 0.1% by weight or more to 0.5%, 1, 2, 3 or 4% by weight or more. In addition, sintering causes a phase transition in which crystalline t-BN is substantially (for example, 10% or more) or more than a predetermined amount (any amount including the intermediate such as 70%, 50%, 30%, 20% or more). Can be performed under no conditions. Thereby, a crystalline t-BN-containing composite ceramic crystal body is obtained.
[0022]
In the preferred embodiment of the present invention, high-performance composite ceramic sintered body can be obtained by sintering under the condition that crystalline t-BN undergoes phase transition (particularly to h-BN). In that case, the phase transition can be controlled to 50% or less, or substantially all of the phase transition can be performed.
[0023]
A preferred method for producing the crystalline t-BN fine powder is a method for producing the crystalline t-BN fine powder described in the above-mentioned Japanese Patent Application No. 9-21052, that is, nitrogen in the presence of an effective amount of molten alkali borate. A-BN powder is heated in a non-oxidizing atmosphere such as a to crystallize a-BN into t-BN. In many cases, the composite ceramic sintered body is a porous sintered body, but the crystalline t-BN fine powder is composed of fine sub-micron primary particles, so that it is easier to sinter and form than the h-BN powder. Then, it becomes a denser compact than the powder mixed with a-BN, and if it is sintered, it becomes a dense composite sintered body. This composite sintered body has a relatively high strength even if the porosity is considerable. When fine crystalline t-BN fine particles remain in the sintered body without being transferred to h-BN at the time of sintering, fine pores are formed due to the presence of fine crystalline t-BN fine particles. The pores in the aggregate have a fine average pore size of submicron size.
[0024]
The method for synthesizing the crystalline t-BN fine powder described in Japanese Patent Application No. 9-21052 is, for example, as follows. The starting material is a mixture of urea, boric acid, and a small amount of alkali borate, which contains an excess of nitrogen components. The mixture is heated in the presence of sodium borate and reacted at 950 ° C. or lower, and boric acid mainly composed of a-BN. And a calme-baked intermediate product containing sodium ions. Next, this intermediate product is pulverized to 1 mm or less, heated to about 1300 ° C. in a nitrogen atmosphere, and crystallized to produce crystalline t-BN. When this crystallized reaction product is purified by washing with water, particularly warm pure water (if necessary, an acid is used for neutralization washing of the alkali component), it is highly pure and has a fine disk shape or spherical shape. Crystalline t-BN fine powder composed of primary particles can be obtained. Fine primary particles of crystalline t-BN fine powder are aggregated to form micron-sized secondary particles. If wet pulverized with an attrition mill, etc., they can be easily pulverized to fine primary particles. Can do. The primary particles of the crystalline t-BN fine powder are not oriented like the hexagonal plate-like h-BN particles when forming a finely pulverized mixed powder by being a fine disc or spherical. As a sintered body, there is an advantage that a sintered body having almost no difference in the coefficient of thermal expansion depending on the molding direction can be obtained.
[0025]
In the present invention, referring to FIG. 3, the diffraction line corresponding to the [004] diffraction line of h-BN (see FIG. 1) has a half-width of 2θ of 0.6 ° or less and a sharp diffraction line. The area occupied by each diffraction line corresponding to the [100], [101] and [102] diffraction lines of h-BN (meaning the intensity of the diffraction lines) S100, S101 and S102 Boron nitride satisfying the relationship of S102 / (S100 + S101) ≦ 0.02 is referred to as crystalline t-BN.
[0026]
The crystalline t-BN powder or fine powder used as the raw material of the sleeve of the present invention includes a crystalline t having a half-width of 2θ of a diffraction line corresponding to the [004] diffraction line of h-BN of 0.5 ° or less. It is preferred to use -BN fine powder.
[0027]
High-purity crystalline t-BN fine powder can be produced by the aforementioned production method. Therefore, the content of the crystalline t-BN contained in the ceramic mixed powder is determined by separately preparing a mixed powder of ceramics with a known crystalline t-BN content and preparing a plurality of standard samples. It can be obtained by comparing the intensity of the crystalline t-BN diffraction line in the line diffraction diagram with the intensity of the crystalline t-BN diffraction line in the powder X-ray diffraction pattern of the pulverized composite ceramic sintered body. .
[0028]
The advantage of using crystalline t-BN fine powder as a raw material is that it is manufactured at a lower cost than the h-BN powder commercially available by the above-mentioned method, and the primary particles of crystalline t-BN fine powder are fine. If the ceramic mixed powder compact is easily sintered, the porous composite sintered body has high strength, and boron nitride remains in crystalline t-BN in the sintered body. A composite ceramic sintered body having fine and uniform pores is obtained.
[0029]
Compared with the case where a-BN powder is used as a raw material, crystalline t-BN fine powder is more stable than moisture such as moisture than a-BN powder, so it is easy to use as a raw material for a sintered body. Compared with the ceramic mixed powder in which the a-BN powder is mixed, a compact having a higher density is obtained, and a composite ceramic sintered body having a higher density is obtained. As in the case of a conventional composite ceramic sintered body containing h-BN powder, the boron nitride-containing composite ceramic sintered body according to the production method of the present invention is a sintered body containing h-BN and / or crystalline t-BN. Because it has a low Young's modulus and high thermal conductivity, it has excellent thermal shock resistance, solid lubricity, excellent corrosion resistance against molten metal, and excellent electrical insulation. There are preferable characteristics such as being.
[0030]
The fine pulverization of crystalline t-BN powder, mixing with other ceramic powders, or mixing that also serves as pulverization is preferably performed by a wet ball mill or attrition mill using alcohol having good dispersibility as a medium. The finer the boron nitride powder mixed with the ceramic mixed powder used as the raw material of the composite ceramic sintered body, the better the sintered body of the molded body, and the primary particles of the crystalline t-BN fine powder obtained by the above-mentioned manufacturing method. Since the average particle size is as fine as 0.4 μm or less, a ceramic mixed powder compact in which this crystalline t-BN fine powder is mixed is preferable because of its excellent sinterability. As a method for producing a composite ceramic sintered body, either pressureless sintering or pressure sintering may be employed. However, if pressureless sintering is employed, the shape of the composite sintered body that can be produced is obtained. It is preferable in that it has a degree of freedom and can produce composite ceramic sintered bodies of various shapes and dimensions at low cost.
[0031]
Crystalline t-BN fine powder used as a raw material is a composite ceramic sintered body in which t-BN and h-BN coexist in a phase transition to a stable high-temperature h-BN crystal when heated for a predetermined time at 1450 ° C or higher. Alternatively, it is a composite ceramic sintered body of h-BN and other ceramics, which does not contain t-BN. When a ceramic mixed powder obtained by combining ceramic powders having a sintering temperature of 1400 ° C. or lower is used as a raw material, a composite ceramic sintered body containing almost the same amount of crystalline t-BN as that blended in the ceramic mixed powder as a starting material is obtained. can get.
[0032]
When the firing temperature of the molded body is about 1450 ° C. or higher (particularly in the range of less than 1500 ° C.), crystalline t-BN phase changes to h-BN with the sintering time. -BN content will change. When the sintering temperature is further increased (especially at about 1500 ° C. or higher), the sintering proceeds rapidly. At the same time, crystalline t-BN rapidly undergoes phase transition to h-BN, and at the same time, crystal growth occurs in the sintered body. H-BN crystal grains formed. In any case, the desired sintered state of BN in the final sintered body (whether only the turbulent layer t-BN is substantially a turbulent layer or t-BN, or a turbulent layer t-BN having a predetermined ratio or less) Accordingly, the maximum sintering temperature can be determined in relation to time.
[0033]
The compounding amount of the ceramic raw material other than boron nitride is 5 to 40% by weight, more preferably 10 to 30% by weight, or 10 to 20% by weight so that a composite ceramic sintered body having high strength can be obtained. It is preferable to use, as a raw material, a mixed powder in which crystalline t-BN (fine powder) is used and the balance is ceramic powder other than boron nitride.
[0034]
As a ceramic raw material other than boron nitride to be mixed with crystalline t-BN powder or fine powder, a ceramic raw material that can be sintered at a temperature of generally about 1450 ° C. or lower (or about 1430 ° C. or 1400 ° C. or lower) can be used. Not only powders, but also precipitation methods, sol-gel methods, mixed forms thereof, natural or synthetic substances can be arbitrarily selected and used. Furthermore, as these ceramic raw materials, those sintered at 1450 ° C. or higher can also be used.
[0035]
As these ceramic raw materials, one or more of oxides, borides, nitrides, carbides, silicides, composite compounds thereof, or composite compounds of these and oxides can be used. Examples of these ceramic raw materials are cordierite, mullite, zircon, zirconia, alumina, spinel, silicon nitride (Si_ThreeN_FourEtc.), aluminum nitride, silicon carbide, zirconium boride, titanium boride, sialon and the like can be used.
[0036]
Among these, it is preferable to obtain a composite ceramic sintered body using a ceramic mixed raw material in which alumina, zirconia, silicon nitride or aluminum nitride is combined, which can obtain a sintered body having particularly high strength and can be expected to have many uses. In the case of producing a composite ceramic sintered body with a non-sintering non-oxide ceramic, a predetermined (preferably for non-oxide ceramic) is used so that the sintering temperature can be lowered and dense sintering can be performed. It is preferable to sinter by adding a sintering aid (a known material can be selected for each ceramic material).
[0037]
If a material that can be sintered at 1450 ° C. or lower such as alumina or zirconia is used as a ceramic raw material other than boron nitride, a composite ceramic sintered body can be obtained without causing phase transition of the crystalline t-BN fine powder. In addition, when it is desired to obtain a composite ceramic sintered body having machinability (same as machinable or machinability), a crystalline t-BN fine powder is used to facilitate the machining with a carbide tip or the like. It is preferable to produce a composite ceramic sintered body using a ceramic mixed powder in which 10% by weight or more is mixed as a raw material. On the other hand, depending on the density of the target composite sintered body, it is difficult to densely sinter the ceramic mixed powder in which crystalline t-BN fine powder is mixed in an amount of more than 35% by weight. Therefore, the mixing amount of the crystalline t-BN fine powder into the ceramic mixed powder is preferably 35% by weight or less.
[0038]
In terms of density, when crystalline t-BN was used, it was found that a sintered body having a very high density (low porosity) can be produced with a blending of about 10% by weight or less. Actually, those having a theoretical density ratio of 95% or more, 98% or more to 99% or more can be sintered.
[0039]
If the porosity of the sintered body is the same, the smaller the pore diameter of the porous composite ceramic sintered body, the stronger the sintered body. In addition, when the composite ceramic sintered body is used for a structural member that requires strength, or when it is desired to provide a good machinability to the composite ceramic sintered body for high-precision processing, the strength is 5 kg / mm²The composite ceramic sintered body described above is preferable. In order to polish the surface of the sintered body to a mirror surface, it is preferable to make the composite ceramic sintered body dense with no open pores. The porosity can be measured with, for example, a mercury porosimeter. Preferably, the average pore diameter measured with a mercury porosimeter of the sintered body is 1.0 μm or less.
[0040]
In a preferred embodiment of the present invention, the average crystal grain size of the crystalline disordered layered boron nitride particles in the sintered body is 0.5 μm or less.
[0041]
In a preferred embodiment of the present invention, the purity of the crystalline disordered layer boron nitride particles is 90% or more and the balance is mainly B.₂O_ThreeIt is sintered using the thing.
[0042]
In a preferred embodiment of the present invention, the primary particle size of the crystalline turbulent structure boron nitride fine powder mixed with the ceramic mixed powder is 1 μm or less, and the average primary particle size is 0.4 μm or less. is there.
[0043]
In a preferred embodiment, the sleeve of the present invention has a thermal shock resistance such as a structural sleeve that requires high strength, a durable breathable porous molten metal mold sleeve, and a protective sleeve that contacts the molten metal. Used as a required sleeve.
[0044]
In a preferred embodiment of the present invention, two or more layers are arranged along the axial direction.
[0045]
In a preferred embodiment of the present invention, ceramic layers having different strength, porosity, and thermal shock resistance are arranged along the axial direction.
[0046]
【Example】
An embodiment of the present invention will be described below with reference to the drawings. The following examples are only examples of the present invention and do not limit the present invention.
[0047]
First, crystalline disordered layer boron nitride (hereinafter referred to as “crystalline t-BN”) included in a sleeve according to an embodiment of the present invention will be described.
[0048]
[Synthesis of crystalline t-BN]
A fine powder of crystalline boron layered boron nitride (hereinafter referred to as “crystalline t-BN”) was synthesized as follows. Boric anhydride (B₂O_Three) 3.5 kg, urea ((NH₂)₂CO) 5.3 kg, borax (Na₂B_FourO₇・ 10H₂O) A mixture consisting of 0.63 kg is used as a starting material, and this mixture is put into a stainless steel vessel with a lid having a diameter of 530 mm, and this reaction vessel is put in a furnace to be 250-500 ° C, 500-600 ° C, 600-700. The temperature was raised to 10 ° C., 700 to 800 ° C., and 800 to 900 ° C. over 10 minutes, and finally the reaction was carried out by maintaining the temperature at 900 ± 1 ° C. for 10 minutes (total 1 hour). During this time, water vapor began to spout at a temperature exceeding 100 ° C., components began to melt at 200 ° C., and bubbles burst out and the reaction proceeded with gas release. When water vapor was mainly released from 350 to 400 ° C. and kept at 900 ° C. for 10 minutes, the release of gas (water vapor and carbon dioxide) decreased.
[0049]
Thereafter, the reaction vessel was allowed to cool and the reaction vessel was opened.₂O_ThreeCompleted the reaction and became a carme-like reaction product. The carme-baked reaction product was crushed in a reaction vessel, vacuumed and taken out from the reaction vessel, crushed and passed through a 1 mm sieve. The pulverized reaction product is put in an alumina lidded pot and closed, and the temperature is raised to 1300 ° C. over 10 hours in an electric furnace with a nitrogen atmosphere. This temperature is maintained for 2 hours and then allowed to cool. did. The powder taken out from the mortar is washed with ion exchange water warmed to 80 to 85 ° C. to remove the alkali and boric acid components, then neutralized with dilute hydrochloric acid, further washed with warm ion exchange water and dried. High crystalline t-BN fine powder was obtained. The yield of the crystalline t-BN fine powder by this series of steps was about 2.8 kg with respect to 10 kg of the starting material, and the production yield with respect to the amount of boron charged in the starting material was 70% or more. The purity of crystalline t-BN ranges from 90 to 97% or more depending on the degree of water washing.
[0050]
The obtained crystalline t-BN fine powder was finely pulverized for 2 hours by an attrition mill (Pearl Mill manufactured by Serizawa Iron Works Co., Ltd.) using ethanol as a medium and zirconia beads having a diameter of 1.2 mm. As a result of examining the particle size distribution of the finely pulverized crystalline t-BN powder (using a Horiba particle size distribution analyzer LA-700), about 95% are fine particles of 1 μm or less, and the average particle size is about 0.00. It was 30 μm. The specific surface area of the powder measured by the nitrogen adsorption method is 12 m.²/ G.
[0051]
FIG. 3 shows a powder X-ray diffraction pattern of the crystalline t-BN fine powder by CuKα ray, FIG. 4 shows a micrograph of the crystalline t-BN fine powder magnified 13300 times, and FIG. 4 shows the crystalline t-BN fine powder. FIG. 5 shows the particle size distribution graphs after pulverizing with an attrition mill.
[0052]
From the powder X-ray diffraction diagram of FIG. 3, the diffraction line corresponding to the [004] diffraction line of h-BN is at 55 of 2θ, the half width of 2θ is 0.47 °, and S102 / (S100 + S101 ) Value was almost zero. Further, as can be seen from the enlarged electron micrograph of FIG. 4, the average particle size of the primary particles of the crystalline t-BN fine powder is about 0.27 μm, and the primary particles of the crystalline t-BN fine powder are circular. It consists of plate-like or spherical particles.
[0053]
The purity of the crystalline t-BN fine powder can be freely controlled depending on the degree of washing, and it can be obtained in high purity of 90% to 97% or more, 98% or 99% or more. As the residue, the crystalline t-BN fine powder obtained by the above method is B₂O_ThreeMainly. Therefore, a predetermined amount of residual B₂O_ThreeIf crystalline t-BN fine powder containing is used, residual B₂O_ThreePlays a role of sintering aid, which contributes to further enhancement of sinterability.
[0054]
Next, a composite ceramic sintered body using the above-described crystalline t-BN powder and other types of ceramic powder as a material of the sleeve according to one embodiment of the present invention will be described.
[0055]
[Purity 92% alumina-crystalline t-BN composite sintered body: see Table 1]
[0056]
[Samples 1 to 5]
Crystalline t-BN fine powder (purity 90-97%, balance is mainly B₂O_Three) And alumina powder (purity 92%, in addition to SiO2)₂A composite ceramic sintered body was prepared by selecting Mars Yuyaku Co., Ltd. having an average particle size of 3.5 μm containing 8% by weight of MgO. However, in Sample 1, the amount of crystalline t-BN blended was 0% by weight. Hereinafter, this production method will be described in detail.
[0057]
That is, 25% by weight of water and 0.3% by weight of a polyacrylic acid ammonium peptizer were added to the alumina powder, and the mixture was prepared by dispersing and mixing in a ball mill for 12 hours. Further, 45% by weight of water and 2% by weight of a polycarboxylic acid ammonium salt peptizer were added to the crystalline t-BN fine powder and dispersed and mixed in a ball mill for 12 hours. Thereafter, both the slurries are mixed to obtain mixed slurries containing 0 wt%, 10 wt%, 15 wt%, 20 wt%, and 25 wt% of the crystalline t-BN fine powder. A wax binder and a polyvinyl alcohol resin binder were added as an agent at a solid content of 3% by weight, and then granulated powder was prepared using a spray dryer.
[0058]
This granulated powder is 1000 kg / cm with a die press molding machine.²A molded body was obtained by pressurizing at a molding pressure of. This molded body was sintered in a reducing atmosphere at 1480 ° C. for 2 hours to obtain a composite ceramic sintered body having dimensions of approximately 15 cm × 15 cm × 2 cm.
[0059]
The properties measured for each composite sintered body obtained are shown in Table 1. As a result of pulverizing each sintered body of Samples 2 to 5 and examining by powder X-ray diffraction, all of the composite boron nitride powder remained in the sintered body in the original crystalline t-BN state. The bulk density, porosity, and water absorption of the sintered bodies shown in Table 1 were measured by Archimedes method, and the bending strength was measured by the method specified in JIS1601. The hardness was measured using a Vickers hardness meter.
[0060]
[Samples 6 and 7]
For comparison, h-BN powder obtained by heating the above crystalline t-BN fine powder to the same alumina powder in a nitrogen atmosphere at 1750 ° C. for 4 hours (average particle size: 4.8 μm, average primary particle size: 1. 5μm, specific surface area 12m²/ G of hexagonal plate-like crystal particles) and h-BN powder (average particle size 0.5 μm, specific surface area 25 m)²A composite ceramic sintered body was prepared in the same manner as in Example 1 using a mixed slurry in which 15% by weight of (/ g powder of hexagonal plate-like crystal particles) were mixed (samples 6 and 7). Also shown.
[0061]
In addition, when cutting was attempted with a cemented carbide tool, it was confirmed that any composite ceramic sintered body of Samples 2 to 7 had good machinability.
[0062]
[Table 1]

[0063]
[Purity 99% alumina-crystalline t-BN composite sintered body: see Table 2]
[0064]
[Samples 8 to 12]
Alumina powder (manufactured by Daimei Chemical with a purity of 99.99% and an average particle size of 0.4 μm) was selected as a ceramic powder to be combined with the crystalline t-BN fine powder to produce a composite ceramic sintered body. However, in Sample 8, the crystalline t-BN blending amount was set to zero wt%. Hereinafter, this production method will be described in detail.
[0065]
That is, 25% by weight of water and 0.6% by weight of a polycarboxylic acid ammonium salt peptizer were added to the alumina powder, and the mixture was dispersed and mixed in a ball mill for 12 hours. Further, 45% by weight of water and 2% by weight of a polycarboxylic acid ammonium salt peptizer were added to the above crystalline t-BN fine powder and dispersed and mixed in a ball mill for 12 hours. Thereafter, both slurries are mixed to obtain a mixed slurry of crystalline t-BN fine powder of zero weight%, 10 weight%, 15 weight%, 20 weight%, 25 weight%, and a molding aid for each mixed slurry. A wax binder and a polyvinyl alcohol resin binder were added at a solid content of 3% by weight, and then granulated powder was prepared using a spray dryer.
[0066]
This granulated powder is 1000 kg / cm with a die press molding machine.²A molded body was obtained by pressurizing at a molding pressure of. This molded body was sintered in a reducing atmosphere at 1350 ° C. for 2 hours to obtain a composite ceramic sintered body having dimensions of approximately 15 cm × 15 cm × 2 cm.
[0067]
The properties measured for each of the obtained composite sintered bodies are summarized in Table 2. The sintered bodies of Samples 9 to 12 were pulverized and examined by powder X-ray diffraction. As a result, all of the composite boron nitride powder remained in the sintered body in the original crystalline t-BN state.
[0068]
[Samples 13 and 14]
For comparison, h-BN powder obtained by heating the above crystalline t-BN fine powder to the same alumina powder in a nitrogen atmosphere at 1750 ° C. for 4 hours (average particle size: 4.8 μm, average primary particle size: 1. 5μm, specific surface area 12m²/ G of hexagonal plate-like crystal particles) and h-BN powder (average particle size of about 0.5 μm, specific surface area of 25 m)²A composite ceramic sintered body is prepared in the same manner as in Example 1 (samples 13 and 14), and the characteristics are shown in Table 2. Also shown.
[0069]
In addition, when cutting with a carbide tool was attempted, it was confirmed that any composite ceramic sintered body of Samples 9 to 14 had good machinability.
[0070]
[Table 2]

[0071]
[Silicon nitride-crystalline t-BN composite sintered body: see Table 3]
[0072]
[Samples 15 to 19]
Α-silicon nitride powder (average particle size 0.6 μm, specific surface area 22 m) is combined with ceramic powder combined with crystalline t-BN fine powder.²/ G Y₂O_Three6% by weight and Al₂O_ThreeWas selected from the group consisting of silicon nitride powder made by Chichibu Onoda and containing 4% by weight. However, in Sample 15, the amount of crystalline t-BN blended was zero weight percent. Hereinafter, this production method will be described in detail.
[0073]
That is, the silicon nitride powder was prepared by adding a water weight of 25% and a polycarboxylic acid ammonium salt peptizer in a solid content of 0.5% by weight, and dispersing and mixing in a ball mill for 12 hours. Further, 45% by weight of water and 2% by weight of a polycarboxylic acid ammonium salt peptizer were added to the above crystalline t-BN fine powder and dispersed and mixed in a ball mill for 12 hours.
[0074]
Thereafter, both the slurries are mixed to obtain mixed slurries containing 0 wt%, 10 wt%, 15 wt%, 20 wt%, and 25 wt% of the crystalline t-BN fine powder. A wax binder and a polyvinyl alcohol resin binder were added as an agent at a solid content of 3% by weight, and then granulated powder was prepared using a spray dryer.
[0075]
This granulated powder is 1000 kg / cm with a die press molding machine.²A molded body was obtained by pressurizing at a molding pressure of. This molded body was sintered in a nitrogen atmosphere at 1800 ° C. for 5 hours to obtain a composite ceramic sintered body having dimensions of approximately 15 cm × 15 cm × 2 cm.
[0076]
Table 3 shows the characteristics measured for each of the obtained composite sintered bodies. Moreover, as a result of grind | pulverizing each sintered compact of Examples 16-19 and investigated by powder X-ray diffraction, it turned out that all the compound boron nitride powder has phase-transformed to the h-BN crystal | crystallization.
[0077]
[Samples 20, 21]
For comparison, h-BN powder (average particle diameter of about 4.8 μm, average primary particles) obtained by heating the crystalline t-BN fine powder to the same silicon nitride powder in a nitrogen atmosphere at 1750 ° C. for 4 hours. Diameter about 1.5μm, specific surface area 12m²/ G of hexagonal plate-like crystal particles) and h-BN powder (average particle size of about 0.5 μm, specific surface area of 25 m)²A composite ceramic sintered body is prepared in the same manner as in Sample 1 (Samples 20 and 21) using a mixed slurry containing 15 wt% of hexagonal plate-like crystal particles / g), and the characteristics are shown in Table 3. Showed.
[0078]
In addition, when cutting with a carbide tool was attempted, it was confirmed that any composite ceramic sintered body of Samples 16 to 21 had good machinability.
[0079]
[Table 3]

[0080]
[Aluminum nitride-crystalline t-BN composite sintered body: see Table 4]
[0081]
[Samples 22 to 26]
Aluminum nitride powder (average particle size 1.4 μm, specific surface area 2.7 m) is combined with ceramic powder combined with crystalline t-BN fine powder.²/ G Y₂O_ThreeWas selected, and a composite ceramic sintered body was produced as a prototype. However, in the sample 22, the crystalline t-BN blending amount was set to zero weight%. Hereinafter, this production method will be described in detail.
[0082]
That is, the aluminum nitride powder was prepared by adding 45% by weight of ethyl alcohol and dispersing and mixing with a ball mill for 12 hours. The crystalline t-BN fine powder was prepared by adding 45% by weight of ethyl alcohol and dispersing and mixing with a ball mill for 12 hours. Thereafter, both the slurries are mixed to obtain mixed slurries containing 0 wt%, 10 wt%, 15 wt%, 20 wt%, and 25 wt% of the crystalline t-BN fine powder. Polyvinyl butyral resin binder was added as an agent at a solid content of 3% by weight, and then granulated powder was prepared using a spray dryer.
[0083]
This granulated powder is 1000 kg / cm with a die press molding machine.²A molded body was obtained by pressurizing at a molding pressure of. This molded body was sintered in a nitrogen atmosphere at 1800 ° C. for 5 hours to obtain a composite ceramic sintered body having dimensions of approximately 15 cm × 15 cm × 2 cm. Table 4 shows the properties measured for each obtained composite sintered body. Moreover, as a result of grind | pulverizing each sintered compact of samples 23-26 and investigating by powder X-ray diffraction, it turned out that all the composite boron nitride powder has phase-shifted to the h-BN crystal | crystallization.
[0084]
For comparison, h-BN powder obtained by heating the crystalline t-BN fine powder to the same aluminum nitride powder at 1750 ° C. for 4 hours in a nitrogen atmosphere (average particle size: 4.8 μm, average primary particle size: 1) .5 μm, specific surface area 12 m²/ G of hexagonal plate-like crystal particles) and h-BN powder (average particle size 0.5 μm, specific surface area 25 m)²A composite ceramic sintered body is prepared in the same manner as in Example 1 (samples 27 and 28) using mixed slurries each containing 15 wt% of hexagonal plate-like crystal particles / g) (samples 27 and 28). Also shown.
[0085]
In addition, when cutting with a carbide tool was attempted, it was confirmed that any composite ceramic sintered body of Samples 23 to 28 had good machinability.
[0086]
[Table 4]

[0087]
Note that, among the samples 1 to 28, the samples 2 to 5, the samples 9 to 12, the samples 16 to 19, and the samples 23 to 26 include crystalline t-BN in the raw material. On the other hand, Sample 1, Sample 8, Sample 15, and Sample 22 do not originally contain crystalline t-BN in the raw material. Also, in Samples 6, 7, 13, 13, 20, 20, and 27 and 28, since raw material powder in which crystalline t-BN is transferred to h-BN by pre-heat treatment is used, sintering is performed. The body does not contain crystalline t-BN.
[0088]
From the results shown in Tables 1 to 4, the composite ceramic sintered body obtained by mixing and sintering the crystalline t-BN fine powder according to the present invention is a composite ceramic sintered body obtained by mixing and sintering the h-BN powder. It can be seen that it has better sinterability and higher bending strength than the body.
[0089]
Further, when the thermal expansion coefficient of a sintered body in which 20% by weight of boron nitride (crystalline t-BN) was combined was measured, the thickness of the composite ceramic sintered body obtained by mixing and sintering the crystalline t-BN fine powder was measured. The ratio of the coefficient of thermal expansion in the direction perpendicular to the thickness direction and the thickness was almost 1, indicating that there was almost no difference in directionality depending on the pressing direction during molding. In addition, the inclusion of silicon nitride improves the strength particularly at high temperatures. These properties are preferable properties for a sleeve in which a high-temperature molten metal flows intermittently.
[0090]
Also, referring to Tables 1 to 4, the smaller the amount of crystalline t-BN blended, the denser the sintered body with lower porosity and the higher strength, while the crystalline t-BN It can be seen that the larger the amount, the higher the porosity, the better the heat insulating property or the heat retaining property, the isotropic thermal expansion coefficient, and the higher the thermal shock resistance.
[0091]
FIG. 6 shows a silicon nitride BN sintered body produced by the same method as a silicon nitride BN sintered body obtained by sintering a powder obtained by mixing a crystalline t-BN fine powder and a silicon nitride powder shown in Table 3. The relationship between the content of crystalline t-BN in the raw material and the porosity in the sintered body in the sintered body is shown. In FIG. 6, the lower broken line indicates the minimum porosity among the sintered bodies having the same BN content, and the upper bent line indicates the maximum porosity among the sintered bodies having the same BN content.
[0092]
FIG. 6 shows that the porosity of the sintered body can be controlled by changing the crystalline t-BN content. For example, it can be seen that the outgassing characteristics and the like can be optimized as a material for a plunger sleeve of a die casting machine by setting the crystalline t-BN content.
[0093]
Note that the crystalline t-BN fine powder is a very fine crystal and is generally often aggregated. Therefore, in the raw material preparation process of molding, how the aggregated powder is dispersed and uniformly mixed with the raw material to be a matrix greatly affects the final sintered body characteristics. In the production process of the present invention, it is necessary to keep in mind that characteristics are greatly changed by performing a process of uniformly dispersing individual powders to be mixed. In this way, a larger amount of BN component can be contained in the sintered body in order to achieve a predetermined strength than when conventional h-BN is used. On the other hand, even if the porosity is the same, it is possible to achieve densification and high strength of the structure.
[0094]
Next, the sleeve which concerns on the Example of the invention used as the foundation of this invention is demonstrated. This sleeve has a single layer structure of a silicon nitride BN sintered body having a single layer inner cylinder structure, and the outer cylinder is made of a metal sleeve. Hereinafter, the manufacturing method and structure of this sleeve will be described.
[0095]
A plunger sleeve of a die casting machine was manufactured using a sintered body similar to that of the sample 23 shown in Table 3 as a material. FIG. 7 is a perspective view showing a structure of a plunger sleeve using a sleeve according to an embodiment of the invention as the basis of the present invention as an inner cylinder, and FIG. 8A is an axial sectional view of the plunger sleeve of FIG. FIG. 8B is a side view of the plunger sleeve of FIG.
[0096]
7, 8 </ b> A, and 8 </ b> B, the plunger sleeve 100 includes a thin-walled inner cylinder 200 that includes a sleeve according to an embodiment of the invention that forms the basis of the present invention, and an inner cylinder 200. It consists of an outer tube 300 made of heat-resistant steel inserted. Since the inner cylinder 200 has good mechanical workability, high dimensional accuracy, and high thermal shock resistance due to isotropic thermal expansion coefficient, the inner cylinder 200 and the outer cylinder 300 can be integrated without shrink fitting. A hole 400 for introducing molten metal is formed in one end of the inner cylinder 200 and the outer cylinder 300. A flange is formed at the other end of the plunger sleeve 100 and is attached to the platen of the die casting machine. The platen comes into contact with the fixed die, and the molten metal pushed out by the plunger head that strokes in the plunger sleeve 100 is supplied to the mold between the fixed die and the movable die that are clamped together.
[0097]
[Die casting test]
Using a die casting machine to which the plunger sleeve described above was applied, the molten metal temperature was changed as follows, and an aluminum alloy was cast. The dimensions of the plunger sleeve 100 (see FIG. 7) were such that the outer diameter 150φ × the inner diameter 80φ × the length 528L, and the thickness of the inner cylinder 200 (see FIG. 8A) was 10 mmt. For comparison, casting was similarly performed using a heat-resistant steel metal sleeve single-layer plunger sleeve. The casting conditions are as follows.
[0098]
Material: ADC10, molten metal temperature: 650-710 ° C., lubricant: graphite-containing lubricant.
[0099]
[Evaluation results]
Table 5 shows the evaluation results of the plunger sleeve using the sleeve according to one embodiment of the present invention and the heat-resistant steel metal sleeve according to the comparative example. The local pressurization in Table 5 is to insert a pressurization core just before the molten metal solidifies in the mold cavity in order to improve the density and dimensional accuracy of the cast product.
[0100]
[Table 5]

[0101]
From Table 5, it can be seen that a product by a die casting machine using a plunger sleeve provided with an inner cylinder made of a crystalline t-BN composite sintered body according to the present example is superior in three-point bending strength. Furthermore, it can be seen that the heat insulation is good, and thus the heat retention of the molten metal is high.
[0102]
Moreover, as a result of observing the fracture surface chill layer of the obtained product, the product by the die casting machine using the plunger sleeve provided with the inner cylinder made of the crystalline t-BN composite sintered body has a more uniform fracture surface. I found out that
[0103]
Further, as a result of an endurance test using this plunger sleeve, the wear on the inner peripheral surface of the sleeve was only 4 μm after 5000 shots. This indicates that the lubricity and melt resistance of the inner sleeve of the plunger sleeve are excellent.
[0104]
A metal ring may be attached to one or both ends of the inner tube of the crystalline t-BN composite sintered body in consideration of ease of handling during assembly or transportation. The same applies to the following embodiments.
[0105]
Next, a sleeve having a multilayer structure in the axial direction according to an embodiment of the present invention will be described. This sleeve is made of a BN composite sintered body obtained by sintering crystalline t-BN fine powder and other types of ceramic powder shown in Tables 1 to 4 above. In particular, the present invention is applied to a plunger sleeve of a die casting machine.
[0106]
FIG. 9 is an axial sectional view of a sleeve having a two-layer structure in the axial direction according to an embodiment of the present invention.
[0107]
Referring to FIG. 9, in this sleeve, a BN high content layer 1 having a high BN content is arranged in the upstream portion where the high-temperature molten metal is introduced, and a low BN content is low in the downstream portion. The layer 2 is disposed, and both layers 1 and 2 are joined in the axial direction. In addition, both layers 1 and 2 can join the molded object from which a BN content rate differs in steps by integral baking irrespective of methods, such as adhesion | attachment and fastening, or contains BN continuously (gradiently). It can also be obtained by firing molded bodies having different rates.
[0108]
For example, referring to Table 3 above, the high BN content layer has high porosity, excellent heat insulation or heat retention, and is more isotropic with respect to thermal expansion, and therefore has high thermal shock resistance. On the other hand, the BN low content layer similarly has the characteristic that the strength is high because the porosity is low and dense with reference to Table 3.
[0109]
Therefore, the BN high content layer 1 with high thermal shock resistance is arranged in the upstream part of the sleeve where the high temperature molten metal is introduced, and high strength BN low content is applied in the downstream part where high pressure is applied when the molten metal is pushed out to the mold. By providing the rate layer 2, a sleeve having an excellent balance between thermal shock resistance and strength is provided, and in addition, restrictions on casting conditions relating to molten metal temperature, extrusion pressure, etc. are relaxed.
[0110]
The sleeve having the two-layer structure in the axial direction described above may be inserted into an outer cylinder sleeve made of metal or the like as an inner cylinder. FIG. 10 shows a case where an inner cylinder sleeve obtained by joining the BN high content layer 1 and the BN low content layer 2 shown in FIG. 8 in the axial direction is inserted into a metal sleeve 3 serving as an outer cylinder.
[0111]
Next, a sleeve having a three-layer structure in the axial direction according to another embodiment of the present invention will be described.
[0112]
FIG. 11 is an axial sectional view of a sleeve having a three-layer structure in the axial direction according to another embodiment of the present invention.
[0113]
Referring to FIG. 11, in this sleeve, a BN high content layer 10 having a high BN content is disposed in the upstream portion where the high-temperature molten metal is introduced, and the BN medium content layer 11 is provided in the intermediate portion. The BN low content layer 12 having a low BN content is arranged on the two layers, and the three layers 10, 11, and 12 are joined to each other in the axial direction. Thus, the balance between strength and thermal shock resistance is further improved.
[0114]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the sleeve with high heat insulation or heat retention and excellent balance of strength and thermal shock resistance is provided. The sleeve according to the present invention is useful as a plunger sleeve of a die casting machine, and relaxes restrictions on casting conditions relating to the molten metal temperature, the molten metal extrusion pressure, and the like.
[0115]
The present invention also develops the use of a novel crystalline disordered layer boron nitride. The sleeve according to the present invention using this novel crystalline turbostratic boron nitride has high heat insulation or heat retention, high strength, isotropic thermal expansion, high thermal shock resistance, good lubricity, gas It has the characteristics that it has good detachability, is difficult to wet with molten metal, and has good machinability. Such a sleeve has extremely excellent characteristics as a material for a plunger sleeve of a die casting machine, and the occurrence of defects in a cast product is reduced, and the working environment temperature is lowered due to the high heat insulating property. .
[0116]
The reason why the above characteristics are obtained is that the sleeve uses a crystalline t-BN powder or a ceramic powder of another kind as a raw material powder. Specifically, since the primary particles of the crystalline t-BN powder are fine crystal particles and the crystalline t-BN powder has a turbulent layer structure, this sleeve is made of regular h-BN powder. Sinterability is better than when used for powder, strength is high, and directionality of thermal expansion is small.
[0117]
Furthermore, as long as the crystalline t-BN remains in the sintered body without undergoing a phase transition, the crystalline t-BN retains the state of fine crystal particles, and thus the pores in the sintered body are also fine. become. Moreover, since the structure of the sintered body is fine, the sintered body has a high strength. This is also almost valid when crystalline t-BN changes to h-BN during the sintering process. Thus, the outgassing property is improved by finely dispersing the pores.
[0118]
Furthermore, the sleeve has excellent machinability (cutting workability), thermal conductivity, electrical insulation, thermal shock resistance, etc. superior to the composite ceramic sintered body using conventional h-BN powder as a raw material. Furthermore, it has favorable characteristics such as resistance to wetness to molten metal and corrosion resistance.
[0119]
The sleeve having such desirable characteristics can be manufactured by pressureless sintering. With the establishment of the above-described technology for producing crystalline t-BN fine powder, it has become possible to procure highly pure crystalline t-BN fine powder at a much lower cost than before.
[0120]
Since the above-mentioned sleeve has good machinability, a high-precision sleeve having a complicated shape can be provided at low cost by using this sleeve. Further, the sleeve according to the present invention is a sleeve that requires thermal shock resistance, such as a structural sleeve that requires high strength, a durable breathable porous molten metal mold sleeve, and a protective sleeve that contacts the molten metal. It is suitable as a material for use. The inclusion of crystalline t-BN (or finely dispersed h-BN derived from crystalline t-BN) can give the composite ceramic sintered body a high slip characteristic, and this characteristic can be controlled and adjusted to any desired value. You can also Moreover, this invention is applied suitably also for the container and hot water supply pipe (refer FIG. 12) for hold | maintaining or distribute | circulating a molten metal.
[Brief description of the drawings]
FIG. 1 is a powder X-ray diffraction pattern of a typical conventional h-BN powder.
FIG. 2 is a powder X-ray diffraction pattern of a conventional a-BN powder.
FIG. 3 is a powder X-ray diffraction pattern of crystalline t-BN fine powder used as a raw material for a sleeve according to an example of the present invention.
4 is an electron micrograph of the crystalline t-BN fine powder in FIG. 3. FIG.
FIG. 5 is a graph showing a particle size distribution after pulverization of crystalline t-BN fine powder used as a raw material of a sleeve according to an example of the present invention by an attrition mill.
FIG. 6 is a graph for explaining the relationship between the content of crystalline t-BN in the raw material and the porosity in the sintered body in the sintered body as the material of the sleeve according to one embodiment of the present invention. It is.
FIG. 7 is a perspective view showing a structure of a plunger sleeve according to an embodiment of the invention as a basis of the present invention.
8A is a cross-sectional view of the plunger sleeve of FIG. 7, and FIG. 8B is a side view thereof.
FIG. 9 is an axial sectional view of a sleeve having a two-layer structure in the axial direction according to an embodiment of the present invention.
10 is a cross-sectional view in the axial direction of a sleeve with the sleeve of FIG. 9 fitted into an outer cylinder.
FIG. 11 is an axial sectional view of a sleeve having a three-layer structure in the axial direction according to another embodiment of the present invention.
FIG. 12 is a perspective view showing a hot water supply pipe according to an application example of the present invention.
[Explanation of symbols]
1 BN high content rate layer
2 BN low content layer
3 Metal sleeve
10 BN high content rate layer
11 Content layer in BN
12 BN low content layer
100 Plunger sleeve
200 Inner cylinder made of crystalline t-BN powder composite sintered body
300 Heat-resistant steel outer cylinder
400 holes

Claims (6)

A sleeve in which a plurality of layers having different content rates of crystalline boron layer boron nitride are arranged along the axial direction ,
The crystalline disordered layer boron nitride has a half-width of 2θ of a diffraction line corresponding to the [004] diffraction line of hexagonal boron nitride in a powder X-ray diffraction pattern by CuKα ray of 0.6 ° or less. Yes, in the powder X-ray diffraction pattern of CuKα ray of hexagonal boron nitride, the area occupied by each diffraction line corresponding to the [100], [101] and [102] diffraction lines is between S 100 , S 101 and S 102. A sleeve characterized by satisfying a relationship of 102 / (S 100 + S 101 ) ≦ 0.02 . The sleeve is the one in which the molten metal flows in the sleeve;
The plurality of layers are arranged so that the content of the crystalline disordered layer boron nitride in the plurality of layers decreases continuously or stepwise from the upstream to the downstream of the sleeve. The sleeve according to claim 1 . 3. The sleeve according to claim 1, wherein the plurality of layers are formed by sintering a powder containing 0.1% by weight or more of crystalline boron layered boron nitride. 4. The plurality of layers are formed by sintering a raw material containing 10 to 20% by weight of a crystalline turbulent layer structure boron nitride powder and the balance mainly containing one or more of silicon nitride powder, alumina powder, and aluminum nitride powder. The sleeve according to any one of claims 1 to 3, characterized in that The crystalline turbostratic nitride the boron-containing is, the half width is 0.5 ° in 2θ of diffraction line corresponding to the diffraction lines [004] of the hexagonal boron nitride in the powder X-ray diffraction diagram below by the CuKα line In the powder X-ray diffraction pattern of hexagonal boron nitride by CuKα ray, S102 / (between the areas S100, S101 and S102 occupied by the diffraction lines corresponding to the [100], [101] and [102] diffraction lines. The sleeve according to any one of claims 1 to 4, wherein a relationship of S100 + S101) <0.02 is satisfied. The sleeve according to any one of claims 1 to 5 or a sleeve formed by inserting the sleeve into another sleeve is used as a plunger sleeve that is a flow path for injecting molten metal into a mold. Die casting machine.

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