JP3563870B2 - Wire rod guide roller made of particle-dispersed silicon carbide sintered body - Google Patents
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【０００１】
【発明の属する技術分野】
本発明は、鉄などの金属線材を熱間圧延で製造する際に使用する耐摩耗性、耐欠損性に優れるガイドローラーに関するものである。
【０００２】
【従来の技術】
熱間線材圧延ラインは、一般に１０００℃以上の高温に熱した太い角柱状ビレットを多数のロールスタンド間を連続的に通過させて減面し、所定の形状、寸法に仕上げるもので、各ロールスタンド間には、圧延中の線材を圧延ロールの所定の位置に誘導するための多数のガイド部材が用いられている。
【０００３】
このガイド部材は、通常、高温かつ高速の線材の確実な誘導を実現するため回転可能なローラーとすることが多い。圧延ラインの中で、特に最終スタンドである仕上圧延機の入側に用いられるガイドローラーは、線材の減面化に従い通材速度が６０ｍ／ｓｅｃ以上と高速になっているうえ、線材の誘導性を高めるため圧延ロールに近づける必要性から直径の小さいローラーを用いることが要求されるなど使用環境は極めて厳しいものとなっている。
【０００４】
従来、これら鉄などの金属線材の圧延機のガイドローラーとしては、高硬度炭素鋼製、もしくは炭化タングステン（ＷＣ）等の超硬合金製のものが用いられてきた。
【０００５】
超硬合金製のローラーは、熱間で被圧延材と反応しにくく、かつ高硬度炭素鋼製のものに比べて耐摩耗性に優れるため、最終スタンド入側に用いた場合でも摩耗によるローラー交換は少なくてすむが、一方で、ＷＣ粒の脱落、チッピング、巨視的な割れ等が、線材と接触するローラーカリバー部で生じる場合があり、被圧延材であるところの線材表面の肌荒れや摩耗傷の原因となっていた。
【０００６】
また、脱落したＷＣ含有の硬質粒が圧延中に線材表面に付着・圧入され、後工程での更なる線材伸線化、細線化の際に断線の原因となる場合があった。
【０００７】
ガイドローラーは通常摩耗領域を研削して再利用するが、残存き裂が再利用時のチッピングの原因となるため、チッピングと割れが生じている領域を完全に削除しておく必要がある。
【０００８】
チッピング・割れが生じると、その研削量としては、割れの深さも含めると一般に摩耗深さの３倍程度必要となり、追加工コストが高くなる一方で、ローラーとしての繰返し利用寿命が短くなるなど、経済性の面で不利となっていた。
【０００９】
さらに、ＷＣ等の超硬合金は一般に比重が大きくローラーの重量が重くなるため圧延時のローラーの回転が加速されるまでの間に激しい摩耗を受け、本来の高い耐摩耗性が十分に発揮されていない場合があった。
【００１０】
一方、超硬合金に比べて低比重でかつ高硬度であるため耐摩耗性の改善が期待される炭化珪素セラミックスをガイドローラーに適用する試みもなされてきており、特開平０１―１３０８０７号公報では、線材と接触する部分を炭化珪素セラミックスで形成し、耐摩耗性と線材表面性状の改善を試みている。
【００１１】
【発明が解決しようとする課題】
ところが従来の炭化珪素セラミックス製ガイドローラーは、ローラーの軽量化の面においては十分機能を発揮しかつ比較的高い耐摩耗性を有するものの摩耗部周囲に巨視的なチッピングや割れの発生が認められ、超硬合金製ローラーとほぼ同等の耐摩耗性を維持したまま耐欠損性を飛躍的に改善するには至っていないため、圧延ラインの最終圧延機入側のように高温の圧延鋼材が極めて高速で通過するような厳しい使用環境下においては信頼性に欠ける問題点があった。
【００１２】
本発明は上記の如き課題を解決するために行われたものである。本発明の目的は、高い耐摩耗性と耐欠損性を両立する線材圧延ガイドローラーを提供することにある。
【００１３】
【課題を解決するための手段】
本発明の線材圧延ガイドローラーは、次のとおりのものである。
（１）少なくとも無加圧焼結してなる炭化珪素（ＳｉＣ）焼結体中に硼化チタン硼化ハフニウム固溶体粒子が分散した相対密度９９％以上の粒子分散炭化珪素質焼結体からなることを特徴とする線材圧延ガイドローラー。
（２）前記硼化チタン硼化ハフニウム固溶体粒子がＴｉ 1-x Ｈｆ x Ｂ 2 （ｘの範囲０．０２〜０．２５）で表される（１）記載の線材圧延ガイドローラー。
（３）前記固溶体粒子の平均径が１〜１０μｍである（１）記載の線材圧延ガイドローラー。
（４）前記固溶体粒子の体積分率が２０〜７０％の範囲である（１）記載の線材圧延ガイドローラー。
（５）前記粒子分散炭化珪素質焼結体のビッカース硬さ（ＨＶ１０）が３１００以上である（１）記載の線材圧延ガイドローラー。
（６）前記粒子分散炭化珪素質焼結体の耐熱衝撃温度差（ΔＴ）が８５０℃以上である（１）記載の線材圧延ガイドローラー。
（７）無加圧焼結を真空中で行う（１）記載の線材圧延ガイドローラー。
（８）無加圧焼結後、さらにアルゴンガス雰囲気中にて熱間静水圧プレス焼結してなる（１）記載の線材圧延ガイドローラー。
【００１４】
本発明者らは種々の研究の結果、セラミックス製線材圧延ガイドローラーの摩耗は高速で通過する線材との摺動により生じ、また摩耗部周囲のチッピングや割れ等の欠損は主に線材先端部分がローラーへ突入する際の機械的衝撃、および１０００〜１２００℃の高温の線材との接触による加熱と周囲からの水冷による熱衝撃により生成・進展するものであり、これら摩耗と欠損はローラーの材質が低硬度、低靭性、低耐熱衝撃性の場合に顕著であることを見出した。
【００１５】
従って、耐摩耗性と耐欠損性を同時に改善し本課題を達成するためには、ローラー材質の高硬度化、高靭性化、高耐熱衝撃性化が必要不可欠である。
【００１６】
これらの特性を同時に向上させる方法としては、充分緻密な焼結体において硬質の粒子を分散させることが効果的であり、特に硬質のＴｉ―Ｈｆ―Ｂ固溶体粒子を炭化珪素中に分散させることにより、従来のモノリシック炭化珪素製ガイドローラーに比べて、耐摩耗性を高めつつ、さらに耐チッピング、耐割れ等の耐欠損性を著しく向上させる効果を付与することが可能であることを見出した。
【００１７】
Ｔｉ―Ｈｆ―Ｂ固溶体は、ｈｃｐ構造をもつ硬質の高融点化合物であり、焼結後に炭化珪素焼結体中に分散粒子として残留し、焼結体全体の硬度を向上させる効果をもつ。
【００１８】
そして炭化珪素相、固溶体相の熱膨張係数差、ヤング率の相異等により、分散粒子近傍に残留応力を発生させ、破壊の際の破壊エネルギーを向上させる効果を持ち、靭性を著しく向上させつつ耐熱衝撃性を向上させる作用をもつ。
【００１９】
本発明のガイドローラーに用いられるＴｉ―Ｈｆ―Ｂ固溶体は、Ｔｉ１−ＸＨｆＸＢ２で表すことができ、Ｘの範囲としては、０．０２〜０．２５であることが好ましい。
【００２０】
ＴｉＢ２相にＨｆＢ２相を所定量固溶させるとＴｉＢ２相単身の場合に比べて硬さを著しく向上させることができるが、Ｘが０．０２より少ない場合、十分な高硬度化がはかれず、また０．２５を超えると炭化珪素との複合材料を焼結する際に９９％以上の相対密度が得られにくい。
【００２１】
本発明の焼結体ではＴｉ１−ＸＨｆＸＢ２固溶体相を２０〜７０体積％含むが、７０体積％より多く添加すると高温での耐酸化性が低下しかつ十分な靭性が得られず耐欠損性が低下する。
【００２２】
また２０体積％より少ないと硬さ、靭性、耐熱衝撃性の向上に充分寄与が認められない。また、分散させるＴｉ１−ＸＨｆＸＢ２固溶体相の粒子径としては、平均結晶粒径の範囲が、１〜１０μｍであることが好ましい。
【００２３】
１μｍより小さいと靭性への寄与が得られ難く、また、１０μｍより大きいと硬さ、耐熱衝撃性の低下を招く。
【００２４】
さらに、本発明では焼結体の相対密度としては９９％以上であるが、９９％未満では、Ｔｉ１−ＸＨｆＸＢ２固溶体相粒子の分散による焼結体中への残留応力の付与が不十分であるため好ましくない。
【００２５】
炭化珪素（ＳｉＣ）は共有結合性の強い物質であり単味では焼結が困難であるため、緻密化に際しては種々の添加物を加えてもかまわない。
【００２６】
焼結助剤としては炭化硼素、金属硼素、炭素、窒化アルミニウム、酸化アルミニウム、希土類酸化物等を用いることができる。
【００２７】
焼結方法としては、少なくとも無加圧焼結法を用い、更にガス圧焼結法、熱間静水圧プレス焼結法、ホットプレス法の一種もしくは複数の焼結法を組み合わせることも可能である。
【００２８】
無加圧焼結は真空中にて行うと緻密な焼結体が得られやすい。複雑形状品であるガイドローラーにおいて高密度を達成するためには、無加圧焼結後、さらにアルゴンガス雰囲気中にて熱間静水圧プレス焼結を行うことが好ましい。
【００２９】
焼結温度の範囲としては、１９５０〜２２００℃であることが好ましく、保持時間は４時間以上であることが望ましい。１９５０℃未満では充分高い密度が得られずＴｉ１−ＸＨｆＸＢ２固溶体相粒子近傍に高い残留応力を発生させることが困難で高い靭性が得られない。また、２２００℃より高い温度では、ＳｉＣが昇華・分解する。
【００３０】
焼結時の保持時間としては、原料として用いたＴｉＢ２粉末とＨｆＢ２粉末が反応し安定なＴｉ１−ＸＨｆＸＢ２固溶体相を生成するのに上記焼結温度の範囲にて４時間以上の保持が必要である。
【００３１】
【作用】
本発明の粒子分散炭化珪素質焼結体からなる線材圧延ガイドローラーは、炭化珪素（ＳｉＣ）焼結体中に平均径１〜１０μｍのＴｉ１−ＸＨｆＸＢ２（Ｘの範囲０．０２〜０．２５）で表せる硼化チタン硼化ハフニウム固溶体粒子が体積分率２０〜７０％の範囲で分散した相対密度９９％以上の粒子分散炭化珪素質焼結体からなるが、これらの組み合わせにより、得られたガイドローラーは、高硬度、高靭性、高耐熱衝撃性を有し、耐摩耗性、耐欠損性が高く、長時間信頼性が高い。
【００３２】
次に本発明の実施例を比較例と共に説明する。
【００３３】
【実施例】
炭化珪素（ＳｉＣ）粉末（β型、平均粒径０．３μｍ）に、硼化チタン（ＴｉＢ２）粉末（平均粒径１μｍ）、硼化ハフニウム（ＨｆＢ２）粉末（平均粒径２μｍ）、炭化硼素（Ｂ４Ｃ）粉末（平均粒径０．８μｍ）、及び炭素（Ｃ）粉末（平均粒径０．０５μｍ）を第１表に示す所定量（重量％）添加し、溶媒としてアセトンを用いて炭化珪素製ボールミルで２４時間混練した。
【００３４】
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、外径φ７０ｍｍ、穴径φ３０ｍｍ、厚さ３５ｍｍのドーナツ状成形体を得た。
【００３５】
焼結としては、真空中にて、第１表中に示す温度で４時間保持の無加圧焼結後、同じく第１表中に示す温度、高圧アルゴンガス雰囲気中にて２時間保持の熱間静水圧プレス焼結を行った。
【００３６】
得られた焼結体から、外径約φ５６ｍｍ、内径約φ２８ｍｍ、厚さ約２５ｍｍ、カリバー面角度１４２度、内側に外径φ３５ｍｍのボールベアリングを２個配置可能な所定の形状のガイドローラーを研削加工し、圧延試験に供した。
【００３７】
得られた焼結体から各種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１０ｋｇにてビッカース硬さとして測定した。
【００３８】
靭性についてはＪＩＳ Ｒ１６０７のＳＥＰＢ法により室温にて破壊靭性値ＫＩＣを測定した。また、耐熱衝撃性としては、曲げ試験片を大気中にて所定の温度に加熱後、水中急冷し、抗折強さの劣化がはじまる急冷温度差ΔＴで評価した。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。
【００３９】
Ｔｉ―Ｈｆ―Ｂ固溶体粒の粒径および体積分率は、焼結体の鏡面研磨面を撮影した光学顕微鏡像（拡大率５００倍）より３０個以上の粒子径および撮影面中の粒子面積分率として測定し、その平均値として表した。
【００４０】
また、Ｔｉ１−ＸＨｆＸＢ２（ｈｃｐ構造）のＸ値はＸ線回折法を用いて、固溶体相の格子定数、ＴｉＢ２（ｈｃｐ構造）の格子定数（ａ＝３．０２６Å、ｃ＝３．２１３Å）、およびＨｆＢ２（ｈｃｐ構造）の格子定数（ａ＝３．１４１Å、ｃ＝３．４７０Å）の値の比から算出した。
【００４１】
得られた各焼結体の諸特性を焼結助剤の添加量、焼結条件、焼結体密度、Ｔｉ―Ｈｆ―Ｂ固溶体の粒径、体積分率、Ｘ値と共に第１表に示す。
【００４２】
圧延試験としては、被圧延材として普通鋼を用い、初期ビレット形状約１２０ｍｍ角・長さ約１８ｍ・重さ約２トン、圧延後線材形状φ５．５ｍｍ・長さ約１１ｋｍ、圧延時線材温度約１０００℃、通材速度約６０ｍ／ｓｅｃの条件にて最終圧延ロール手前のガイドローラーとして各材種ごとに２個一組を配置し、合計１６０トン（ビレット８０本）を通材させた後、ローラーカリバー部に発生した摩耗痕の深さｈを表面粗さ計にて測定した。
【００４３】
また摩耗痕周囲の損傷有無、チッピング深さ、および割れ深さを蛍光探傷法および断面研磨面の光学顕微鏡観察により評価した。
【００４４】
再利用に当たってのローラーカリバー面の必要研削量は、摩耗痕周囲に割れ・チッピングの損傷が観察されない場合は摩耗痕深さｈの１．２倍、チッピングが生じている場合はチッピング深さの１．２倍、そして割れが発生している場合は割れの深さの１．２倍として第１表中に示した。
【００４５】
比較例として、Ｔｉ―Ｈｆ―Ｂ固溶体粒子を添加していない炭化珪素製ローラー、および超硬合金製ローラーの結果も併せて第１表に示す。
【００４６】
第１表に示すように、本発明の実施例によるものは、摩耗痕深さが何れも線材１６０トン通材後で８０μｍ以下と少なくかつ摩耗痕周囲には割れ・チッピングの欠損が何れの場合も認められず、耐摩耗性、耐欠損性共に優れるが、比較例に該当するローラーでは本発明の実施例と比べて、摩耗痕深さが大きいか、もしくは少なくとも割れ、チッピングの何れかが発生しており、耐摩耗性、耐欠損性の両立が図られていないことが確認された。
【００４７】
また、ガイドローラーを繰返し再利用するに当たってのカリバー面の必要研削量も、本発明によるものは１００μｍ未満と小さいのに対し、比較例に該当するローラーでは発生した割れ・チッピング領域の除去のために必要研削量が１８０μｍ以上と大きく、再研削時の加工費、繰返し利用を含めた製品の総寿命を考慮すると経済的に不利であることが確認された。
【００４８】
【表１】
【表２】
【発明の効果】
本発明によれば、本発明により得られた粒子分散炭化珪素質焼結体からなる線材圧延ガイドローラーは、高硬度、高靭性、高耐熱衝撃性を有し、上記の如く高い耐摩耗性を維持しつつ、耐欠損性をより優れたものとすることが可能となった。
【００５１】
このことにより長時間信頼性の非常に優れた線材圧延ガイドローラーの作製が可能となり、その工業的有用性は非常に大きい。
【図面の簡単な説明】
【図１】本発明の実施例による線材圧延ガイドローラーの側面図である。
【符号の説明】
１ 線材圧延ガイドローラー
２ 被圧延線材
３ ローラーカリバー部摩耗痕
４ チッピング
５ 割れ[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a guide roller having excellent abrasion resistance and fracture resistance used when a metal wire such as iron is manufactured by hot rolling.
[0002]
[Prior art]
A hot wire rolling line is a process in which a thick prismatic billet generally heated to a high temperature of 1000 ° C. or higher is continuously passed between a number of roll stands to reduce the surface area and finish to a predetermined shape and dimensions. Many guide members are used between the rolling rolls to guide the wire being rolled to a predetermined position on the rolling roll.
[0003]
This guide member is usually a rotatable roller in order to realize a high-temperature and high-speed wire guide. In the rolling line, particularly, the guide roller used on the entrance side of the finishing mill, which is the final stand, has a high threading speed of 60 m / sec or more in accordance with the reduction in the surface area of the wire rod, and also has an inductive property of the wire rod. The use environment is extremely severe, for example, it is required to use a roller having a small diameter because of the necessity of approaching a rolling roll in order to increase the pressure.
[0004]
Conventionally, as a guide roller of a rolling machine for metal wires such as iron, a roller made of high-hardness carbon steel or a cemented carbide such as tungsten carbide (WC) has been used.
[0005]
Rollers made of cemented carbide are less likely to react with the material to be rolled hot and have higher abrasion resistance than those made of high-hardness carbon steel. On the other hand, WC grains may fall off, chipping, macroscopic cracks, etc. may occur at the roller caliber that comes in contact with the wire, and the surface of the wire, which is the material to be rolled, has a rough surface or abrasions. Was the cause.
[0006]
In addition, the dropped WC-containing hard particles are attached and pressed into the surface of the wire during rolling, which may cause disconnection when the wire is further drawn and thinned in a subsequent process.
[0007]
The guide roller is usually reused by grinding the worn area. However, since the remaining cracks cause chipping at the time of reuse, it is necessary to completely remove the area where chipping and cracking occur.
[0008]
When chipping or cracking occurs, the grinding amount is generally required to be about three times the abrasion depth including the crack depth, which increases the additional work cost and shortens the life of repeated use as a roller. It was disadvantageous in terms of economy.
[0009]
In addition, cemented carbides such as WC generally have a high specific gravity and a heavy weight of the roller, so they undergo severe abrasion before the rotation of the roller during acceleration is accelerated, and the original high wear resistance is sufficiently exhibited. There was no case.
[0010]
On the other hand, attempts have been made to apply silicon carbide ceramics, which are expected to have improved wear resistance due to their lower specific gravity and higher hardness as compared with cemented carbides, as guide rollers, and Japanese Patent Application Laid-Open No. 01-130807 discloses a technique. Attempts have been made to improve the wear resistance and the surface properties of the wire by forming the portion in contact with the wire with silicon carbide ceramics.
[0011]
[Problems to be solved by the invention]
However, conventional silicon carbide ceramics guide rollers have sufficient functions in terms of reducing the weight of the rollers and have relatively high abrasion resistance, but macro chipping and cracking are observed around worn parts, Since the fracture resistance has not been improved dramatically while maintaining the wear resistance almost the same as that of cemented carbide rollers, high-temperature rolled steel at extremely high speeds, such as at the entrance to the final rolling mill in the rolling line, has not been developed. There is a problem of lack of reliability under a severe use environment such as passing.
[0012]
The present invention has been made to solve the above problems. An object of the present invention is to provide a wire rolling guide roller that achieves both high wear resistance and chipping resistance.
[0013]
[Means for Solving the Problems]
The wire rod guide roller of the present invention is as follows.
(1) consisting of at least pressureless sintering to become silicon carbide (SiC) boric titanium boride, hafnium solid solution particles in the sintered body is distributed a relative density of 99% or more of the particles dispersed silicon carbide sintered body A wire rod rolling guide roller characterized by the above-mentioned .
(2) the titanium boride boride, hafnium solid solution particles is represented by Ti 1-x Hf x B 2 ( range x 0.02 to 0.25) (1) wire rolling guide rollers according.
(3) The wire rod rolling guide roller according to (1), wherein the solid solution particles have an average diameter of 1 to 10 μm.
(4) The wire rod guide roller according to (1), wherein a volume fraction of the solid solution particles is in a range of 20 to 70%.
(5) The wire rod guide roller according to (1), wherein the particle-dispersed silicon carbide sintered body has a Vickers hardness (HV10) of 3100 or more.
(6) The wire rod guide roller according to (1), wherein the particle-dispersed silicon carbide sintered body has a thermal shock temperature difference (ΔT) of 850 ° C. or more.
(7) The wire rod guide roller according to (1), wherein the pressureless sintering is performed in a vacuum.
(8) The wire rod guide roller according to (1), further comprising hot isostatic press sintering in an argon gas atmosphere after pressureless sintering.
[0014]
As a result of various studies, the present inventors have found that the wear of the ceramic wire rod guide roller is caused by sliding with the wire passing at high speed, and the chipping and cracking around the worn portion is mainly caused by the loss of the tip of the wire. The mechanical shock when entering the roller, and the heat generated by contact with a high-temperature wire rod of 1000 to 1200 ° C and the thermal shock caused by water cooling from the surroundings, are generated and propagated. It was found to be remarkable in the case of low hardness, low toughness, and low thermal shock resistance.
[0015]
Therefore, in order to simultaneously improve the wear resistance and the fracture resistance and achieve the object, it is essential to increase the hardness, toughness and thermal shock resistance of the roller material.
[0016]
As a method of simultaneously improving these properties, it is effective to disperse hard particles in a sufficiently dense sintered body, and particularly by dispersing hard Ti—Hf—B solid solution particles in silicon carbide. It has been found that, compared to a conventional monolithic silicon carbide guide roller, it is possible to impart an effect of significantly improving chipping resistance, cracking resistance, and other chipping resistance while improving wear resistance.
[0017]
The Ti—Hf—B solid solution is a hard high-melting compound having an hcp structure, remains as dispersed particles in the silicon carbide sintered body after sintering, and has an effect of improving the hardness of the entire sintered body.
[0018]
And, due to the difference in thermal expansion coefficient between the silicon carbide phase and the solid solution phase, the difference in Young's modulus, etc., a residual stress is generated in the vicinity of the dispersed particles, and has the effect of improving the breaking energy at the time of breaking, while significantly improving the toughness. Has the function of improving thermal shock resistance.
[0019]
Ti-Hf-B solid solution used in the guide rollers of the present invention, Ti 1-X Hf can be represented by X B 2, as the range of X, is preferably 0.02 to 0.25.
[0020]
Can be significantly improved hardness as compared with the case when the predetermined amount of solid solution of HfB 2 phases TiB 2 phase of TiB 2 phase alone, if X is less than 0.02, sufficiently high hardness is the If it exceeds 0.25, it is difficult to obtain a relative density of 99% or more when sintering the composite material with silicon carbide.
[0021]
Although the sintered body of the present invention containing Ti 1-X Hf X B 2 solid solution phase 20 to 70% by volume, can not be obtained oxidation resistance is lowered and sufficient toughness at high temperatures is added more than 70 vol% The fracture resistance decreases.
[0022]
On the other hand, if it is less than 20% by volume, sufficient contribution to improvement in hardness, toughness and thermal shock resistance cannot be recognized. As the particle size of the Ti 1-X Hf X B 2 solid solution phase to be dispersed, the range of the average crystal grain size is preferably 1 to 10 [mu] m.
[0023]
If it is less than 1 μm, it is difficult to contribute to toughness, and if it is more than 10 μm, hardness and thermal shock resistance are reduced.
[0024]
Further, in the present invention, the relative density of the sintered body is not less than 99%, but if the relative density is less than 99%, the residual stress in the sintered body due to the dispersion of the Ti 1-X Hf X B 2 solid solution phase particles may not be provided. It is not preferable because it is insufficient.
[0025]
Since silicon carbide (SiC) is a substance having a strong covalent bond and is difficult to sinter simply, various additives may be added at the time of densification.
[0026]
As the sintering aid, boron carbide, metallic boron, carbon, aluminum nitride, aluminum oxide, rare earth oxide, and the like can be used.
[0027]
As a sintering method, have use at least pressureless sintering method, further gas pressure sintering method, a hot isostatic pressing sintering method, it is also possible to combine one or more sintering method of hot pressing is there.
[0028]
When pressureless sintering is performed in a vacuum, a dense sintered body is easily obtained. In order to achieve high density in the guide roller having a complicated shape, it is preferable to perform hot isostatic press sintering in an argon gas atmosphere after sintering without pressure.
[0029]
The sintering temperature is preferably in the range of 1950 to 2200 ° C., and the holding time is preferably 4 hours or more. Not obtained difficult and high toughness that sufficiently high density to generate a high residual stresses in the vicinity of Ti 1-X Hf X B 2 solid solution phase particles not obtained at less than 1950 ° C.. At a temperature higher than 2200 ° C., sublimation and decomposition of SiC occur.
[0030]
The holding time during sintering, 4 hours range the sintering temperature to TiB 2 powder and HfB 2 powder used as the raw material react to produce stable Ti 1-X Hf X B 2 solid solution phase The above holding is necessary.
[0031]
[Action]
Wire rolling guide rollers consisting of particles dispersed silicon carbide sintered body of the present invention, Ti 1-X Hf
[0032]
Next, examples of the present invention will be described together with comparative examples.
[0033]
【Example】
Silicon carbide (SiC) powder (β type, average particle size 0.3 μm), titanium boride (TiB 2 ) powder (
[0034]
Next, the obtained mixed powder was sintered after molding. The molding conditions were pressurization by cold isostatic pressure of 150 MPa, and a donut shaped body having an outer diameter of 70 mm, a hole diameter of 30 mm, and a thickness of 35 mm was obtained.
[0035]
The sintering was performed under pressure-free sintering at a temperature shown in Table 1 for 4 hours in a vacuum, and then for 2 hours at a temperature shown in Table 1 in a high-pressure argon gas atmosphere. Isostatic press sintering was performed.
[0036]
From the obtained sintered body, a guide roller of a predetermined shape capable of arranging two ball bearings having an outer diameter of about 56 mm, an inner diameter of about 28 mm, a thickness of about 25 mm, a caliber surface angle of 142 degrees, and an inner diameter of 35 mm inside is ground. It was processed and subjected to a rolling test.
[0037]
Test pieces of various shapes were cut out from the obtained sintered body, and the mechanical properties were evaluated. Hardness was measured as Vickers hardness at an indentation load of 10 kg.
[0038]
Regarding toughness, the fracture toughness value K IC was measured at room temperature by the SEPB method of JIS R1607. The thermal shock resistance was evaluated by a quenching temperature difference ΔT at which the bending test piece was heated to a predetermined temperature in the atmosphere, then rapidly cooled in water, and the bending strength began to deteriorate. The sintered body density was measured as a relative density by the Archimedes method.
[0039]
The particle diameter and the volume fraction of the Ti—Hf—B solid solution particles were determined by using an optical microscope image (magnification: 500 times) of a mirror-polished surface of the sintered body, with a particle diameter of 30 or more and a particle area in the photographed surface. The ratio was measured and expressed as the average value.
[0040]
Further, Ti 1-X X value of Hf X B 2 (hcp structure) using X-ray diffraction method, the lattice constant of the solid solution phase, TiB 2 lattice constant of (hcp structure) (a = 3.026Å, c = 3.213 °) and the lattice constant (a = 3.141 °, c = 3.470 °) of HfB 2 (hcp structure).
[0041]
Table 1 shows the characteristics of each of the obtained sintered bodies together with the amount of the sintering aid added, the sintering conditions, the sintered body density, the particle diameter of the Ti—Hf—B solid solution, the volume fraction, and the X value. .
[0042]
As the rolling test, ordinary steel was used as the material to be rolled, the initial billet shape was about 120 mm square, the length was about 18 m, the weight was about 2 tons, the wire shape after rolling was 5.5 mm, the length was about 11 km, and the wire temperature during rolling was about 11 km. At a temperature of 1000 ° C. and a threading speed of about 60 m / sec, a pair of two rollers is arranged for each material as a guide roller before the final rolling roll, and a total of 160 tons (80 billets) are passed. The depth h of the wear mark generated in the roller caliber was measured by a surface roughness meter.
[0043]
The presence or absence of damage around the wear mark, the chipping depth, and the crack depth were evaluated by fluorescence inspection and optical microscope observation of the polished surface of the cross section.
[0044]
The required amount of grinding of the roller caliber surface during reuse is 1.2 times the depth h of the wear mark when no cracking or chipping damage is observed around the wear mark, and 1 times the chipping depth when chipping occurs. The results are shown in Table 1 as .2 times, and 1.2 times the crack depth when cracks occurred.
[0045]
As a comparative example, Table 1 also shows the results of a roller made of silicon carbide and a roller made of cemented carbide to which Ti-Hf-B solid solution particles were not added.
[0046]
As shown in Table 1, in the case of the embodiment of the present invention, the wear scar depth was as small as 80 μm or less after passing 160 tons of wire and the cracks and chipping defects were lost around the wear scar. No wear was observed, and both abrasion resistance and chipping resistance were excellent.However, in the roller corresponding to the comparative example, as compared with the example of the present invention, the wear scar depth was large, or at least one of cracking and chipping occurred. It was confirmed that both abrasion resistance and chipping resistance were not achieved.
[0047]
In addition, while the required amount of grinding of the caliber surface when repeatedly reusing the guide roller is less than 100 μm according to the present invention, the roller corresponding to the comparative example is used for removing cracks and chipping regions generated. The required grinding amount was as large as 180 μm or more, and it was confirmed that it was economically disadvantageous in consideration of the processing cost at the time of re-grinding and the total life of the product including repeated use.
[0048]
[Table 1]
[Table 2]
【The invention's effect】
According to the present invention, the wire rolling guide roller made of the particle-dispersed silicon carbide-based sintered body obtained by the present invention has high hardness, high toughness, high thermal shock resistance, and has high wear resistance as described above. It has become possible to improve the fracture resistance while maintaining the same.
[0051]
This makes it possible to produce a wire rolling guide roller having extremely excellent long-term reliability, and its industrial utility is very large.
[Brief description of the drawings]
FIG. 1 is a side view of a wire rolling guide roller according to an embodiment of the present invention.
[Explanation of symbols]
1 Wire
Claims (8)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10645196A JP3563870B2 (en) | 1996-04-04 | 1996-04-04 | Wire rod guide roller made of particle-dispersed silicon carbide sintered body |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10645196A JP3563870B2 (en) | 1996-04-04 | 1996-04-04 | Wire rod guide roller made of particle-dispersed silicon carbide sintered body |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH09278523A JPH09278523A (en) | 1997-10-28 |
| JP3563870B2 true JP3563870B2 (en) | 2004-09-08 |
Family
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP10645196A Expired - Lifetime JP3563870B2 (en) | 1996-04-04 | 1996-04-04 | Wire rod guide roller made of particle-dispersed silicon carbide sintered body |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3563870B2 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4690553B2 (en) * | 2001-01-09 | 2011-06-01 | 新日本製鐵株式会社 | Mating ring for shift side guide roll |
| JP5131289B2 (en) * | 2010-01-18 | 2013-01-30 | 新日鐵住金株式会社 | Immersion member for molten metal plating bath |
| JP2019156684A (en) * | 2018-03-14 | 2019-09-19 | 美濃窯業株式会社 | Composite ceramic member and manufacturing method therefor |
-
1996
- 1996-04-04 JP JP10645196A patent/JP3563870B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH09278523A (en) | 1997-10-28 |
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