JP2004255401A

JP2004255401A - Cemented carbide double layer hot rolling roll having outer ring member made of wear-resistant cemented carbide exhibiting excellent high temperature hardness and strength

Info

Publication number: JP2004255401A
Application number: JP2003047590A
Authority: JP
Inventors: Teruyoshi Tanase; 照義棚瀬; Hiroki Kawase; 広樹河瀬; Katsu Yamamoto; 克山本
Original assignee: Mitsubishi Materials Corp
Current assignee: Mitsubishi Materials Corp
Priority date: 2003-02-25
Filing date: 2003-02-25
Publication date: 2004-09-16

Abstract

<P>PROBLEM TO BE SOLVED: To provide a double-layer hot rolling roll made of cemented carbide having the outer ring member made of a wear-resistant cemented carbide exhibiting excellent hardness and strength at high temperatures. <P>SOLUTION: The outer ring member of the double-layer hot rolling roll is made of the wear-resistant cemented carbide, has structure in which the outer ring member made of the wear resistant cemented carbide and an inner ring member made of high toughness cemented carbide are integrally joined, and is composed of: the cemented carbide having a composition, by mass, of 5 to 10% Co, 1 to 6% Ni and 0.4 to 1% Cr as a binder phase component; 5 to 15% composite carbo-nitride of Ti and W which satisfies a compositional formula: (Ti<SB>1-X</SB>W<SB>X</SB>)(C<SB>1-Y</SB>N<SB>Y</SB>)<SB>Z</SB>, ( where, in atomic ratio, X is 0.1 to 0.4, Y is 0.1 to 0.4 and Z is 0.95 to 1.05) as dispersed phase forming component; and the balance composition of tungsten carbide with inevitable impurities as a dispersed phase forming component. The cemented carbide has three phase structure consisting of a binder phase, the composite carbo-nitride phase of Ti and W, and the tungsten carbide phase. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
この発明は、構成部材である耐摩耗性超硬合金製外側リング部材が、すぐれた高温硬さと高温強度を有し、したがって線材や棒鋼などの熱間圧延加工において、苛酷な加工条件下でも長期に亘ってすぐれた性能を発揮する超硬合金製２層熱間圧延ロールリング（以下、２層圧延リングという）に関するものである。
【０００２】
【従来の技術】
従来、一般に、線材や棒鋼などが熱間圧延加工によって製造され、例えば線材の熱間圧延加工に用いられるブロックミルが、耐摩耗性を有する超硬合金製外側リング部材（以下、外側リング部材という）と、主にＣｏやＮｉなどで構成された結合相形成成分の含有割合を前記外側リング部材に比して高くして（相対含有割合で１．０５〜１．３０）、強靭性を具備せしめた超硬合金製内側リング部材（以下、内側リング部材という）が一体接合した構造を有し、前記外側リング部材の外周面に沿って圧延加工溝が形成された２層圧延リング２本を一対とし、前記２層圧延リングがそれぞれシャフトの先端部にテーパースリーブを介して固定された構造を有し、前記相互圧延加工溝によって形成された穴型を線材素材が通過することにより線材に成形されるものである（例えば、特許文献１参照）。
したがって、特に上記２層圧延リングの外側リング部材には、常にテーパースリーブによる内側圧力と加工線材による外側圧力がかかり、かつその表面部は高温加熱の線材素材によって高温加熱され、自体の温度上昇を防止する目的で水冷された条件で操業されるため、大きな機械的熱的内部応力が存在するものである。
また、上記の２層圧延リングの外側リング部材や内側リング部材として各種の超硬合金が提案されている（例えば、特許文献２参照）。
【０００３】
【特許文献１】
特開昭４９−１０５７４９号公報
【特許文献２】
特開昭４９−６６５１０号公報
【０００４】
【発明が解決しようとする課題】
一方、近年の熱間圧延装置の高性能化および高出力化はめざましく、また熱間圧延加工の省力化および省エネ化に対する要求も強く、これに伴い、熱間圧延加工は高速化および高圧下率化の傾向にあるが、従来２層圧延リングにおいては、これを高速および高圧下率条件で用いると、特にこれの構成部材である外側リング部材の高温硬さおよび高温強度不足が原因で、特に圧延加工中に前記外側リング部材に割れが生じたり、これの摩耗進行が著しく促進したりして、比較的短時間で使用寿命に至るのが現状である。
【０００５】
【課題を解決するための手段】
そこで、本発明者等は、上述のような観点から、特に２層圧延リングの外側リング部材の高温硬さおよび高温強度の向上を図るべく、研究を行った結果、
２層圧延リングの外側リング部材を、いずれも質量％で（以下、％は質量％を示す）、結合相形成成分として、
Ｃｏ：５〜１０％、
Ｎｉ：１〜６％、
Ｃｒ：０．４〜１％、
を含有し、分散相形成成分として、
組成式：（Ｔｉ_１−ＸＷ_Ｘ）（Ｃ_１−ＹＮ_Ｙ）_Ｚ、
（ただし、原子比で、Ｘ：０．１〜０．４、Ｙ：０．１〜０．４、Ｚ：０．９５〜１．０５）を満足するＴｉとＷの複合炭窒化物［以下、（Ｔｉ，Ｗ）ＣＮで示す］：５〜１５％、
を含有し、残りが分散相形成成分としてのＷＣと不可避不純物からなる組成を有する超硬合金で構成すると、前記（Ｔｉ，Ｗ）ＣＮは、それ自体ですぐれた高温硬さと高温強度を有し、かつ超硬合金の高温硬さと高温強度を著しく向上させる作用を有することから、外側リング部材をこの超硬合金で構成した２層圧延リングは、高速および高圧下率条件で用いても、圧延加工溝に割れの発生なく、すぐれた耐摩耗性を長期に亘って発揮するようになる、という研究結果を得たのである。
【０００６】
この発明は、上記の研究結果に基づいてなされたものであって、外側リング部材と内側リング部材が一体接合した構造の２層圧延ロールの前記外側リング部材を、結合相形成成分として、
Ｃｏ：５〜１０％、
Ｎｉ：１〜６％、
Ｃｒ：０．４〜１％、
を含有し、分散相形成成分として、
組成式：（Ｔｉ_１−ＸＷ_Ｘ）（Ｃ_１−ＹＮ_Ｙ）_Ｚ、
（ただし、原子比で、Ｘ：０．１〜０．４、Ｙ：０．１〜０．４、Ｚ：０．９５〜１．０５）を満足する（Ｔｉ，Ｗ）ＣＮ：５〜１５％、
を含有し、残りが分散相形成成分としてのＷＣと不可避不純物からなる組成、並びに結合相、（Ｔｉ，Ｗ）ＣＮ相、およびＷＣ相の３相組織を有する超硬合金で構成してなる、外側リング部材がすぐれた高温硬さおよび高温強度を有する２層圧延ロールに特徴を有するものである。
【０００７】
つぎに、この発明の２層圧延ロールにおいて、これの外側リング部材を構成する超硬合金の組成を上記の通りに限定した理由を説明する。
（ａ）Ｃｏ
Ｃｏ成分には、焼結性を向上させると共に、結合相を形成して常温強度を向上させる作用があるが、その含有量が５％未満では所望の常温強度を確保することができず、一方その含有量がが１０％を越えると耐摩耗性が急激に低下するようになることから、その含有量を５〜１０％と定めた。
【０００８】
（ｂ）Ｎｉ
Ｎｉ成分には、Ｃｏと共存して結合相を形成し、合金成分である（Ｔｉ，Ｗ）ＣＮの焼結時の分解を抑制する作用があるが、その含有量が１％未満では前記作用に所望の向上効果が得られず、一方その含有量が６％を越えると高温強度が急激に低下するようになることから、その含有量を１〜６％と定めた。
【０００９】
（ｃ）Ｃｒ
Ｃｒ成分には、結合相に固溶して常温強度を向上させるほか、結合相の耐酸化性を向上させる作用があるが、その含有量が０．４％未満では前記作用に所望の向上効果が得られず、一方その含有量がが１％を越えると、Ｃｒの複炭化物を形成し、これが高温強度低下の原因となることから、その含有量を０．４〜１％と定めた。
【００１０】
（ｄ）（Ｔｉ，Ｗ）ＣＮ
（Ｔｉ，Ｗ）ＣＮ成分は、高硬度を有するＴｉＣにＷ成分を固溶含有させて耐熱性を向上させ、かつＮ成分を含有させて炭窒化物として強度を向上させ、もってすぐれた高温硬さと高温強度を有するものとし、かつこれを超硬合金に含有させることによって超硬合金の高温硬さと高温強度を著しく向上させる作用があるが、その含有量が５％未満では前記作用に所望の向上効果が得られず、一方その含有量がが１５％を越えると焼結性が低下し、強度低下が避けられなくなることから、その含有量を５〜１５％と定めた。
また、上記の通りＷ成分には、耐熱性を向上させ、もって高温特性（高温硬さと高温強度）を向上させる作用があるが、組成式において、その含有割合を示すＸ値が、Ｔｉとの合量に占める割合で、かつ原子比（以下同じ）で、０．１未満では所望の高温特性向上効果が得られず、一方同Ｘ値が同じくＴｉとの合量に占める割合で、０．４を越えると、高温強度が低下するようになることから、Ｘ値を０．１〜０．４と定めた。
Ｎ成分には、強度を向上させ、かつＷ成分との共存含有において高温強度を向上させる作用があるが、同じくＮ成分の含有割合を示すＹ値がＣとの合量に占める割合で、０．１未満では所望の高温強度向上効果が得られず、一方同Ｙ値が同じくＣとの合量に占める割合で、０．４を越えると、高温強度が低下するようになることから、Ｙ値を０．１〜０．４と定めた。
さらに、同じく、上記の組成式において、ＴｉとＷ成分の合量に対するＣとＮ成分の合量の割合を示すＺ値が０．９５未満でも、１．０５を越えても高温硬さおよび高温強度に低下傾向が現れるようになることから、Ｚ値を０．９５〜１．０５と定めた。
【００１１】
【発明の実施の形態】
つぎに、この発明の２層圧延ロールを実施例により具体的に説明する。
原料粉末として、表１に示される平均粒径をもったＷＣ粉末、同１．３μｍのＣｏ粉末、同１．５μｍのＮｉ粉末、同１．６μｍのＣｒ粉末、さらに同じく表１に示される組成および平均粒径を有する（Ｔｉ，Ｗ）ＣＮ粉末を用意し、これら原料粉末を表１に示される配合組成に配合し、アルコール中、ボールミルで５時間湿式混合し、乾燥した後、１００ＭＰａの圧力で外側リング部材用成形体にプレス成形し、また、上記原料粉末を用い、ＷＣ粉末としては平均粒径：５μｍのものを用い、配合組成を、Ｃｏ：１３％、Ｃｒ：０．７％、ＷＣ：残りとする以外は同一の条件で内側リング部材用成形体をプレス成形し、この時高温強度を評価する目的で高温抗折力測定用試験片の成形体もプレス成形し、これら外側リング部材用成形体と内側リング部材用成形体を嵌合した状態で、真空中、１３６０〜１４００℃の範囲内の所定の温度に１時間保持の条件で焼結した後、研磨加工することにより、外径：１６６ｍｍ×内径：１２６ｍｍ×長さ：７２ｍｍの寸法をもった内側リング部材と一体に焼結結合され、かつ外径：２１２ｍｍ×内径：１６６ｍｍ×長さ：７２ｍｍの寸法をもち、外周面にそって半円形圧延加工溝が２本形成された本発明２層圧延ロール１〜５、および外側リング部材が従来２層圧延ロールの外側リング部材を構成する超硬合金に相当する組成をもった超硬合金からなる従来２層圧延ロール１〜５、さらに縦：４ｍｍ×横：８ｍｍ×長さ：２４ｍｍの寸法をもった高温抗折力測定用試験片を製造した。
【００１２】
この結果得られた各種２層圧延ロールの外側リング部材（高温抗折力測定用試験片）を構成するそれぞれの超硬合金について、その組成をオージェ分光分析装置を用いて測定したところ、実質的に配合組成と同じ組成を示し、また、その組織を光学顕微鏡を用いて観察したところ、本発明２層圧延ロールの外側リング部材は、いずれも、実質的に結合相、（Ｔｉ，Ｗ）ＣＮ相、およびＷＣ相からなる３相組織を示し、また従来２層圧延ロールの外側リング部材は、いずれも、実質的に結合相とＷＣ相からなる２相組織を示した。
【００１３】
ついで、上記の本発明２層圧延ロール１〜５および従来２層圧延ロール１〜５をそれぞれ一対として仕上げ寸法の異なる熱間圧延機の仕上げ段に組み込み、
表２に示される条件で、かつ、
線材素材：約９００℃に加熱された軟鋼材、
圧下率：約１５％、
とした条件で熱間圧延加工試験を行い、一穴型（カリバー）当りの寿命までの圧延量を調べた。寿命は線材の寸法と仕上げ面状態で判断したが、これらはロールの摩耗とカリバー内のクラック発生状態によって支配される。また、上記の高温抗折力測定用試験片を用いて、６００℃での高温抗折力およびビッカース硬さを測定し、高温強度および高温硬さを評価した。これらの測定結果を表２に示した。
【００１４】
【表１】

【００１５】
【表２】

【００１６】
【発明の効果】
表１，２に示される結果から、本発明２層圧延ロール１〜５は、いずれも外側リング部材を構成する超硬合金が（Ｔｉ，Ｗ）ＣＮを含有することによって高温強度と高温硬さを具備するようになり、熱間圧延加工を行なっても圧延加工溝に割れの発生なく、かつすぐれた耐摩耗性を発揮するのに対して、外側リング部材が（Ｔｉ，Ｗ）ＣＮを含有しない超硬合金で構成された従来２層圧延ロール１〜５においては、いずれも外側リング部材の圧延加工溝に割れが発生し、さらに摩耗進行も速いことと相俟って、比較的早期に使用寿命に至ることが明らかである。
上述のように、この発明の２層圧延ロールは、熱間圧延加工を行なっても割れの発生なく、すぐれた耐摩耗性を示すものであるから、熱間圧延装置の高性能化および高出力化、さらに熱間圧延加工の省力化および省エネ化にも十分満足に対応できるものである。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides an outer ring member made of a wear-resistant cemented carbide having excellent high-temperature hardness and high-temperature strength, and therefore, can be used for a long time even under severe processing conditions in hot rolling of a wire rod or a steel bar. The present invention relates to a two-layer hot-rolled roll ring (hereinafter, referred to as a two-layer roll ring) made of cemented carbide that exhibits excellent performance over a wide range.
[0002]
[Prior art]
Conventionally, in general, a wire rod or a steel bar is manufactured by hot rolling, and for example, a block mill used for hot rolling of a wire is formed of a wear-resistant cemented carbide outer ring member (hereinafter, referred to as an outer ring member). ) And the content ratio of the binder phase forming component mainly composed of Co, Ni, or the like is made higher than that of the outer ring member (relative content ratio is 1.05 to 1.30) to provide toughness. A two-layer rolled ring having a structure in which a cemented carbide inner ring member (hereinafter referred to as an inner ring member) integrally joined and having a rolling groove formed along the outer peripheral surface of the outer ring member is used. The two-layer rolling ring is a pair, and has a structure in which each of the two-layer rolling rings is fixed to a tip portion of a shaft via a tapered sleeve, and the wire material passes through a hole formed by the mutual rolling grooves. It is intended to be formed (e.g., see Patent Document 1).
Therefore, in particular, the outer ring member of the two-layer rolling ring is always subjected to the inner pressure by the tapered sleeve and the outer pressure by the processing wire, and its surface is heated at a high temperature by the high-temperature heating wire material, and the temperature rise of itself is suppressed. Since the operation is performed under water-cooled conditions for the purpose of prevention, there is a large mechanical and thermal internal stress.
Also, various cemented carbides have been proposed as the outer ring member and the inner ring member of the above two-layer rolled ring (for example, see Patent Document 2).
[0003]
[Patent Document 1]
JP-A-49-105549 [Patent Document 2]
JP-A-49-66510
[Problems to be solved by the invention]
On the other hand, in recent years, high performance and high output of hot rolling equipment have been remarkable, and there is also a strong demand for labor saving and energy saving of hot rolling processing. In the conventional two-layer rolled ring, when it is used under high-speed and high-pressure reduction conditions, particularly due to the lack of high-temperature hardness and high-temperature strength of the outer ring member, which is a component thereof, At present, the outer ring member is cracked during the rolling process, and the wear progress of the outer ring member is remarkably accelerated.
[0005]
[Means for Solving the Problems]
In view of the above, the present inventors have conducted research in order to improve the high-temperature hardness and high-temperature strength of the outer ring member of the two-layer rolled ring, in particular, as a result,
The outer ring members of the two-layer rolling ring are each expressed by mass% (hereinafter,% indicates mass%) as a binding phase forming component,
Co: 5 to 10%,
Ni: 1 to 6%,
Cr: 0.4-1%,
Containing, as a dispersed phase forming component,
_{_{_{Formula: (Ti 1-X W X}}} ) (C 1-Y N Y) Z,
(However, in terms of atomic ratio, X: 0.1 to 0.4, Y: 0.1 to 0.4, Z: 0.95 to 1.05) , (Ti, W) CN]: 5 to 15%,
(Ti, W) CN itself has excellent high-temperature hardness and high-temperature strength when it is composed of a cemented carbide having the composition of WC as a dispersed phase forming component and unavoidable impurities. , And has the effect of remarkably improving the high-temperature hardness and high-temperature strength of the cemented carbide, so that the two-layer rolling ring in which the outer ring member is made of this cemented carbide can be rolled even when used under high-speed and high-pressure reduction conditions. Research results have shown that excellent wear resistance can be exhibited over a long period of time without cracks in the machined grooves.
[0006]
The present invention has been made based on the above research results, wherein the outer ring member of the two-layer rolling roll having a structure in which the outer ring member and the inner ring member are integrally joined, as a bonding phase forming component,
Co: 5 to 10%,
Ni: 1 to 6%,
Cr: 0.4-1%,
Containing, as a dispersed phase forming component,
_{_{_{Formula: (Ti 1-X W X}}} ) (C 1-Y N Y) Z,
(However, in atomic ratio, X: 0.1 to 0.4, Y: 0.1 to 0.4, Z: 0.95 to 1.05) (Ti, W) CN: 5 to 15 %,
And a balance consisting of WC as a dispersed phase forming component and inevitable impurities, and a cemented carbide having a three-phase structure of a binder phase, a (Ti, W) CN phase, and a WC phase. The outer ring member is characterized by a two-layer roll having excellent high-temperature hardness and high-temperature strength.
[0007]
Next, the reason why the composition of the cemented carbide constituting the outer ring member of the two-layer rolling roll of the present invention is limited as described above will be described.
(A) Co
The Co component has an effect of improving sinterability and forming a binder phase to improve room temperature strength. However, if its content is less than 5%, a desired room temperature strength cannot be secured. If the content exceeds 10%, the abrasion resistance rapidly decreases, so the content is set to 5 to 10%.
[0008]
(B) Ni
The Ni component has a function of forming a binder phase in coexistence with Co and suppressing the decomposition of the alloy component (Ti, W) CN at the time of sintering. However, when the content exceeds 6%, the high-temperature strength rapidly decreases. Therefore, the content is set to 1 to 6%.
[0009]
(C) Cr
The Cr component has a function of improving the room-temperature strength by dissolving in the binder phase and improving the oxidation resistance of the binder phase. If the content is less than 0.4%, the above effect is desired. When the content exceeds 1%, on the other hand, if the content exceeds 1%, a double carbide of Cr is formed, which causes a decrease in high-temperature strength. Therefore, the content was determined to be 0.4 to 1%.
[0010]
(D) (Ti, W) CN
The (Ti, W) CN component is a high-hardness alloy having a high hardness by improving the heat resistance by adding a W component to TiC having a high hardness to improve heat resistance, and by adding an N component to improve the strength as a carbonitride. And has the effect of significantly improving the high-temperature hardness and the high-temperature strength of the cemented carbide by containing it in the cemented carbide. If no improvement effect is obtained, on the other hand, if the content exceeds 15%, the sinterability decreases, and a reduction in strength cannot be avoided. Therefore, the content is set to 5 to 15%.
In addition, as described above, the W component has an effect of improving heat resistance and thereby improving high-temperature characteristics (high-temperature hardness and high-temperature strength). If the ratio is less than 0.1 in the total amount and the atomic ratio (the same applies hereinafter), the desired high-temperature property improving effect cannot be obtained, while the same X value in the same amount in the total amount with Ti is not more than 0.1. If it exceeds 4, the high-temperature strength will decrease, so the X value is set to 0.1 to 0.4.
The N component has the effect of improving the strength and improving the high-temperature strength in the co-presence of the W component. However, the Y value indicating the content ratio of the N component is 0% in the total amount with the C component. If the value is less than 0.1, the desired high temperature strength improving effect cannot be obtained, while if the Y value exceeds 0.4 in the total amount of the total amount with C, the high temperature strength decreases. The value was defined as 0.1-0.4.
Further, similarly, in the above composition formula, even if the Z value indicating the ratio of the total amount of the C and N components to the total amount of the Ti and W components is less than 0.95 or exceeds 1.05, the high-temperature hardness and the high-temperature Since the strength tends to decrease, the Z value is set to 0.95 to 1.05.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, the two-layer rolling roll of the present invention will be specifically described with reference to examples.
As raw material powders, WC powder having the average particle diameter shown in Table 1, Co powder of 1.3 μm, Ni powder of 1.5 μm, Cr powder of 1.6 μm, and composition shown in Table 1 And (Ti, W) CN powders having an average particle size are prepared, and these raw material powders are blended in the blending composition shown in Table 1, wet-mixed in an alcohol in a ball mill for 5 hours, dried, and then dried under a pressure of 100 MPa. Press molding into a molded product for an outer ring member, using the above raw material powder, WC powder having an average particle size of 5 μm, and using a composition of 13% Co, 0.7% Cr, WC: Press-molding the molded body for the inner ring member under the same conditions except for the remaining, and then, for the purpose of evaluating the high-temperature strength, also molded the molded body of the test piece for measuring the high-temperature bending strength, Molded parts for members and inside After sintering in a vacuum at a predetermined temperature in the range of 1360 to 1400 ° C. for 1 hour in a state in which the molded body for a grinding member is fitted, the outer diameter is 166 mm × inner diameter by polishing. : 126 mm x length: 72 mm, sintered integrally with the inner ring member, having an outer diameter of 212 mm x inner diameter: 166 mm x length: 72 mm, and semicircular rolling along the outer peripheral surface The two-layer rolling rolls 1 to 5 of the present invention in which two processing grooves are formed, and the outer ring member is made of a cemented carbide having a composition corresponding to the cemented carbide constituting the outer ring member of the conventional two-layer rolling roll. Conventional two-layer rolling rolls 1 to 5, and a test piece for measuring high-temperature bending strength having dimensions of 4 mm in length, 8 mm in width, and 24 mm in length were manufactured.
[0012]
The composition of each of the cemented carbides constituting the outer ring members (test pieces for measuring high-temperature bending strength) of the various two-layer rolls obtained as a result was measured using an Auger spectroscopic analyzer. The composition of the outer ring member of the two-layer roll of the present invention was substantially the same as the binder phase (Ti, W) CN when the composition was observed with an optical microscope. Phase and a three-phase structure composed of a WC phase, and the outer ring member of the conventional two-layer roll exhibited a two-phase structure substantially composed of a binder phase and a WC phase.
[0013]
Then, the above-described two-layer rolling rolls 1 to 5 of the present invention and the conventional two-layer rolling rolls 1 to 5 are respectively incorporated as a pair into finishing stages of hot rolling mills having different finishing dimensions,
Under the conditions shown in Table 2, and
Wire material: Mild steel material heated to about 900 ° C,
Reduction rate: about 15%,
A hot rolling test was performed under the conditions described above, and the rolling amount up to the service life per one-hole die (calibur) was examined. The service life was determined by the dimensions of the wire and the condition of the finished surface, but these are governed by the wear of the rolls and the state of cracks in the caliber. Further, using the test specimen for measuring high-temperature bending strength, high-temperature bending strength at 600 ° C. and Vickers hardness were measured to evaluate high-temperature strength and high-temperature hardness. Table 2 shows the measurement results.
[0014]
[Table 1]

[0015]
[Table 2]

[0016]
【The invention's effect】
From the results shown in Tables 1 and 2, the two-layer rolling rolls 1 to 5 of the present invention show that the cemented carbide constituting the outer ring member contains (Ti, W) CN and has high-temperature strength and high-temperature hardness. The outer ring member contains (Ti, W) CN, while exhibiting excellent wear resistance without cracks in the rolled grooves even when hot rolling is performed. In the conventional two-layer rolling rolls 1 to 5 made of a cemented carbide, the cracks are generated in the rolling grooves of the outer ring member, and the wear progresses quickly. It is clear that the service life will be reached.
As described above, the two-layer rolling roll of the present invention does not crack even when subjected to hot rolling and exhibits excellent wear resistance. Therefore, it is possible to sufficiently satisfactorily cope with the reduction of labor and energy consumption of hot rolling.

Claims

In a cemented carbide two-layer hot rolling roll having a structure in which an outer ring member made of wear-resistant cemented carbide and an inner ring member made of tough cemented carbide are integrally joined,
The above wear-resistant cemented carbide outer ring members are all in mass%,
As a binding phase forming component,
Co: 5 to 10%,
Ni: 1 to 6%,
Cr: 0.4-1%,
Containing, as a dispersed phase forming component,
_{_{_{Formula: (Ti 1-X W X}}} ) (C 1-Y N Y) Z,
(However, a complex carbonitride of Ti and W satisfying X: 0.1 to 0.4, Y: 0.1 to 0.4, Z: 0.95 to 1.05 in atomic ratio): 5 ~ 15%,
And a balance consisting of tungsten carbide and inevitable impurities as a dispersed phase forming component, and a cemented carbide having a three-phase structure of a binder phase, a composite carbonitride phase of Ti and W, and a tungsten carbide phase. A two-layer hot-rolled roll made of cemented carbide, wherein the outer ring member made of wear-resistant cemented carbide has excellent high-temperature hardness and high-temperature strength.