JP3891419B2 - Roll for rolling - Google Patents
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- JP3891419B2 JP3891419B2 JP2002276623A JP2002276623A JP3891419B2 JP 3891419 B2 JP3891419 B2 JP 3891419B2 JP 2002276623 A JP2002276623 A JP 2002276623A JP 2002276623 A JP2002276623 A JP 2002276623A JP 3891419 B2 JP3891419 B2 JP 3891419B2
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Description
【0001】
【発明の属する技術分野】
本発明は、耐摩耗性、耐クラック性に優れた圧延用ロールに関する。
【0002】
【従来の技術】
圧延用ロールにおいて、圧延材と接触する外層は一般的に耐摩耗性、耐肌荒れ性、耐クラック性(耐事故性)が要求される。この要求に応えることを目論んだロール材として、Cr、Mo、W、Vなどの合金元素を各数%含有させたハイス系材料が用いられている。
【0003】
このハイス系ロール材は、V系炭化物であるMC(Mはメタルをさす)、Mo及びW系炭化物であるM6CやM2Cなどの高硬度炭化物を晶出もしくは析出させ、Feの基地と炭化物の総和としての硬さを高め、Mo、Wにより高温での基地硬さの低下を抑えた材料であり、特に熱間圧延用ロールの外層に適する。
【0004】
ハイス系ロール材として、例えば特許文献1には、外層に金属的に接合した鋼製の軸とからなる耐摩耗複合ロールであって、外層の表面硬さがショアー硬さ70以上であり、外層が重量%でC:1.5〜3.5%、Si:0.3〜3.0%、Mn:0.3〜1.5%、Cr:2.0〜7.0%、Mo:9.0%以下、W:20.0%以下、V:3.0〜15.0%及び残部実質的にFeからなり、さらにNi:5.0%以下、Co:5.0%以下、Nb:5.0%以下のうちいずれか1種以上を含有できることが記載されている。
【0005】
また、特許文献2には、外層の成分が重量%でC:1.5〜3.0%、Si:0.3〜2.5%、Mn:0.3〜1.0%、Cr:2.0〜10.0%、Mo:2.0〜8.0%、W:2.0〜8.0%、V:2.0〜8.0%、Co:3.0〜10.0%、Ni:1.0〜4.0%、Y:1.0〜10.0%及び残部実質的にFeからなり、組織中の硬質の一次炭化物を増加させ、Co、Yの添加により焼戻し時に析出する外層組織中の二次炭化物量を増大させ基地を強化することによって、耐摩耗性、耐クラック性及び低熱膨張率を兼ね備えたことを特徴とする圧延ロールの外層が記載されている。
【0006】
さらに、特許文献3には、外層の成分が重量%でC:1.0〜2.5%、Si:0.2〜2.0%、Mn:0.3〜1.0%、Cr:2.0〜8.0%、Mo:0.5〜6.0%、W:0.5〜8.0%、V:0.5〜8.0%、Co:2.0〜6.0%、Nb:0.1〜5.0%及び残部実質的にFeからなり、かつロール外殻層の700℃における硬度がビッカース硬さで400以上で、圧縮残留応力が30〜50kgf/mm2であることを特徴とする圧延ロールの外層が記載されている。この公報によれば、外層全体の高温硬さを開示しているが、外層の基地硬さおよびこれを高める考えについては開示されていない。
【0007】
【特許文献1】
国際公開第WO88/07594号パンフレット
【特許文献2】
特許第2999472号公報
【特許文献3】
特開平9−78186号公報
【0008】
【発明が解決しようとする課題】
近年、圧延条件が過酷になり、より高い耐摩耗性が要求されるようになった。このため、前記ハイス系外層は、硬質炭化物を増加させた組織からなり、さらに、Co、Nb等を添加することにより外層の耐摩耗性の向上をはかろうとしている。ところが、炭化物の量を増やすと、ロール外層の靭性の低下を招き、耐クラック性が劣化する問題があった。このため、圧延用ロールに優れた耐摩耗性、耐クラック性の両者を具備させることは実際には難しく、圧延用ロールの用途に合わせて耐摩耗性あるいは耐クラック性のいずれかを偏重的に考慮して製造せざるを得なかった。
【0009】
そこで、本発明は上記ハイス系ロール材における問題を解消し、耐摩耗性および耐クラック性に優れた圧延用ロールを提供することを目的とする。
【0010】
【課題を解決するための手段】
本発明者らは鋭意検討を重ねた結果、生成される炭化物の中でも比較的硬さが低く耐摩耗性を劣化させる原因となる、またクラックが粒界に沿って進展して耐クラック性を劣化させる原因となるM7C3やM23C6炭化物を極力抑える必要がある。また、特にCとVとMoとWのバランスを最適な条件にすることにより、耐摩耗性に特に寄与するMC、M4C3、M2C、M6C炭化物を最適な範囲で生成させる必要がある。また、ロール外層表面温度は約600℃の高温に達する。そこで、本発明の最大の特徴として、実際の圧延時において、炭化物のみならず、600℃での外層の基地を強化させることで、耐摩耗性を一層向上させることができると考えた。さらに、耐クラック性を劣化させる原因となるM2C、M6C炭化物を最適な範囲に抑える必要があると考えた。これらの技術的思想により、圧延材と接触するロール表面組織をより一層強化することで、ロール材の耐摩耗性及び耐クラック性を向上できる知見を得て本発明を完成した。
【0011】
すなわち、本発明の圧延用ロールは、圧延材と接触するロール外層表面の硬さがショア硬さ87以上であり、600℃における外層表面の基地硬さがビッカース硬さ350以上であり、外層が重量%で、C:1.0〜2.6%、Cr:4.0〜10.0%、Mo:5.0〜10.0%、W:0〜5.0%、V:3.0〜8.0%を含有し、12.9%≦2Mo+W≦20.0%、2Mo/W≧3.0、0.2%≦C−0.24V≦0.7%を満足するFe基合金であることを特徴とする。
【0012】
【作用】
本発明の圧延用ロールは、ロール外層のショア硬さが87以上及び600℃での外層基地硬さをビッカース硬さで350以上とし、格段に耐摩耗性を向上させることができる。したがって、特に熱間圧延用ロールとして有効に用いることができる。
【0013】
本発明における各成分元素の含有範囲の限定理由について説明する。
【0014】
C:1.0〜2.6%
Cは、耐摩耗性向上のための炭化物の形成と、基地への固溶による焼入れ・焼戻し時の基地硬さの向上に必要である。Cは、耐摩耗性を付与すべきMC、M4C3、M2C、M6C、M7C3などの炭化物を生成する。Cが1.0%未満では炭化物の生成量が不足して耐摩耗性に劣る。Cが2.6%を超えると、耐摩耗性は良好であるが、耐クラック性が低下する。
【0015】
Cr:4.0〜10.0%
Crは、焼入れ性を向上させ、硬さを高くする。Crが4.0%未満ではその効果が小さい。また、10.0%を超えると、常温での残留オーステナイトが多くなるので、焼戻し回数が多くなり不経済となる。さらに、Crは比較的硬さの低いM7C3やM23C6炭化物を形成し、多量の添加はこれらの炭化物が過剰となり耐摩耗性が劣化する。より好ましいCr含有量は、4.5〜7.0%である。
【0016】
Mo:5.0〜10.0%
Moは、焼入れ性の向上と基地の高温硬さを得るために必要である。基地組織中に固溶して焼入れ性の向上をもたらす。また、Cと結合して硬質のM2C、M6C炭化物を生成する。Moが5.0%未満ではその効果が小さい。また、10.0%を超えると、CとVとMoのバランスにおいてM2C、M6C炭化物が多く晶出しすぎ、耐クラック性が低下する。
【0017】
W:0〜5.0%
Wは、Moと同様に焼入れ性の向上と基地の高温硬さを得るために必要である。基地の焼入れ性を上げ、Cと結合して硬質のM2C、M6C炭化物を生成する。Wの下限は0%である。また、5.0%を超えると、M6C炭化物が増加して耐クラック性及び耐肌荒れ性の点で好ましくない。
【0018】
V:3.0〜8.0%
Vは、耐摩耗性の向上に最も寄与する硬質な炭化物であるMC、M4C3を形成する。Vが3.0%未満では炭化物の生成が少なく耐摩耗性が劣化する。Vが8.0%を超えると、本発明のC含有量とのバランスにより、初晶としてMC、M4C3炭化物が晶出する。MC、M4C3が初晶で晶出すれば凝固中に凝集し、圧延用ロールとして使用した場合、硬質炭化物であるMC、M4C3の凝集偏析が被圧延材に転写されるので好ましくない。
【0019】
12.0%≦2Mo+W≦20.0%
Mo、Wは焼入れ性の向上、炭化物形成などでその効果が類似しており、重量比で見た場合、その原子量差からMoはWのほぼ2倍の効果がある。本発明の最も特徴とするものの一つに、Mo、W含有量とショア硬さ、高温硬さの相関がある。2Mo+Wが12.0%以上の場合、焼入れ性の向上が顕著になり、ショア硬さ87以上を安定して確保できるとともに、600℃における基地のビッカース硬さを350以上にすることができる。また、2Mo+Wが20.0%を超えると、M2C、M6Cの炭化物を多く晶出させすぎ耐クラック性が低下するので好ましくない。
【0020】
2Mo/W≧3.0
MoとWは、炭化物形成と高温基地硬さの上昇に関してほぼ同様な効果があるが、Wに対してMoは基地の粘さを向上させる効果を有する。また、炭化物形成においてWはM6C炭化物を晶出させる効果がMoに比べて大きい。Mo、Wが形成する炭化物としてM2C、M6Cがあるが、凝固時に晶出するM2Cに対してM6Cは粗大になりやすい。これらのことより、前述の12.0%≦2Mo+W≦20.0%を満たすにあたり、Wを多く添加すると高温基地硬さは向上するが、粗大M6Cが晶出し、耐クラック性が向上しないのでMoを多く添加したほうがよい。2Mo/W≧3.0とすることで、高温基地硬さを十分に向上させ、粗大M6Cの晶出を防止することにより、耐クラック性を向上させることができる。
【0021】
0.2%≦C−0.24V≦0.7%
Vの含有量が多すぎるとVC炭化物にCをとられるため、基地組織のC含有量が不足して、焼入れ後の硬さが低くなる。Vの含有量が少なすぎるとVC炭化物が不足し硬さが低くなる。そこで、C、Vのバランスを考慮した0.2%≦C−0.24V≦0.7%の条件を満足すれば、ショア硬さ87以上を安定して確保できるとともに、基地のビッカース硬さを600℃で350以上にすることができる。
【0022】
また、本発明のロール材の成分元素として、Siの含有量は0.1〜3.0%が好ましい。Siは、脱酸剤として作用し、またM6C炭化物中に固溶してW、Moなどの元素を置換して含有されるため、W、Moなどの高価な元素の節減を図るために有効である。Siが0.1%未満では脱酸効果が不足して鋳造欠陥を生じやすい。また、3.0%を超えると脆化が生じやすい。
【0023】
また、熱間圧延用ロールの最表面において、圧延材と接触している部分でのピーク温度は約600℃と推定される。600℃における基地のビッカース硬さが350未満であると基地が塑性流動を起こしやすくなり、耐摩耗性、耐肌荒れ性に劣り、さらに、黒皮の帯状剥離や焼付きが発生しやすくなる。したがって、600℃における基地の硬さはビッカース硬さ350以上が好ましく、より好ましくは、ビッカース硬さ400以上である。
【0024】
Mnの含有量は0.1〜3.0%が好ましい。Mnは、Siと同様に脱酸作用がある。また、不純物であるSをMnSとして固定する作用がある。Mnが0.1%未満では脱酸性に乏しい。また、3.0%を超えると残留オーステナイトが生じやすくなり、安定して十分な硬さを維持できない。
【0025】
本発明の圧延用ロールは、遠心鋳造法、鋳掛け肉盛法などにより製造される。なかでも製造コスト的に有利な遠心鋳造法がより好ましい。また、本発明のロール材を外層とし、内層と金属接合させた複合ロールが好ましいが、本発明のロール材で形成される単体ロールにも当然ながら適用できる。
【0026】
【発明の実施の形態】
本発明の圧延用ロール材の実施例について以下に説明する。
【0027】
表1に示す圧延用ロール材の化学組成(重量%)にて、No.1〜4の本発明実施例の各供試材と、No.5〜10の比較例の各供試材を、1500〜1550℃まで加熱、溶解し、直径90mm、高さ90mmの円柱状の鋳型に鋳込んだ。冷却後、インゴットを取りだし、1000〜1200℃で、焼入れを行い、500〜600℃で3回焼戻しを行った。
【0028】
その後、インゴットの中央部から硬さ測定用の試験片を採取した。硬さは各供試材の表面の硬さをショア硬さ計及び高温硬度測定器により測定した。高温硬度は、JIS Z 2252に準じて行った。このとき、試料の予熱時間は10分とした。
【0029】
供試材No.1〜4は、本発明の請求項に掲げたC、Cr、Mo、W、Vの成分範囲内で調整し、さらに本発明の2Mo+W、2Mo/WおよびC−0.24Vの各条件を満足するものである。また、供試材No.5〜11は、本発明の2Mo+W、2Mo/WおよびC−0.24Vのいずれかの条件から外れるものである。
【0030】
【表1】
【0031】
表1から、ショア硬さについては、本発明の実施例である供試材No.1〜4において、2Mo+W、2Mo/WおよびC−0.24Vのいずれの条件も満足しており、ショア硬さ87以上を安定して得られることが確認できた。
【0032】
同様に、表1から、本発明の実施例である供試材No.1〜4において、2Mo+W、2Mo/WおよびC−0.24Vのいずれの条件も満足しており、600℃における基地のビッカース硬さを350以上に安定して得られることが確認できた。
【0033】
また、比較例の供試材No.5〜11では、本発明の特徴である2Mo+W、2Mo/WおよびC−0.24Vのいずれかの条件を外れるため、ショア硬さ87以上、600℃における基地のビッカース硬さが350以上を同時に満足し得なかった。
【0034】
また、遠心鋳造機を用い、本発明実施例である供試材No.1の成分を胴部外層に有する胴径φ600mm、胴長1830mmの熱間圧延用の遠心鋳造製複合ロールを製造した。ロールは胴部表面の硬さがショア硬さ88、600℃における外層表面基地のビッカース硬さが413であった。さらに胴部端部の組織調査、及び超音波非破壊調査を行い、組織、欠陥の調査を行ったうえで、健全なロールであることを確認した。実際の圧延に供したところ従来の遠心鋳造複合ロールより、耐摩耗性に優れ、圧延操業に起因する耐クラック性にも優れることがわかった。
【0035】
【発明の効果】
本発明の圧延用ロールは、圧延材と接触するロール外層表面の硬さがショア硬さ87以上と高硬度であるとともに、600℃における外層基地のビッカース硬さが350以上と高い値を示し、耐摩耗性および耐クラック性に優れ、安定した圧延を行うことができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a roll for rolling excellent in wear resistance and crack resistance.
[0002]
[Prior art]
In the roll for rolling, the outer layer in contact with the rolled material is generally required to have wear resistance, rough skin resistance, and crack resistance (accident resistance). As a roll material intended to meet this requirement, a high-speed material containing several percent of alloy elements such as Cr, Mo, W, and V is used.
[0003]
This high-speed roll material crystallizes or precipitates high-hardness carbides such as MC (M stands for metal), Mo, and W-based carbides such as M 6 C and M 2 C. Is a material in which the total hardness of the carbides is increased and the decrease in the base hardness at high temperatures is suppressed by Mo and W, and is particularly suitable for the outer layer of a hot rolling roll.
[0004]
As a high-speed roll material, for example, Patent Document 1 discloses a wear-resistant composite roll including a steel shaft that is metallically bonded to an outer layer, and the outer layer has a surface hardness of 70 or more and a outer hardness of 70 or more. Is C: 1.5-3.5%, Si: 0.3-3.0%, Mn: 0.3-1.5%, Cr: 2.0-7.0%, Mo: 9.0% or less, W: 20.0% or less, V: 3.0-15.0% and the balance substantially consisting of Fe, Ni: 5.0% or less, Co: 5.0% or less, It is described that any one or more of Nb: 5.0% or less can be contained.
[0005]
In Patent Document 2, the components of the outer layer are C: 1.5 to 3.0%, Si: 0.3 to 2.5%, Mn: 0.3 to 1.0%, Cr: 2.0-10.0%, Mo: 2.0-8.0%, W: 2.0-8.0%, V: 2.0-8.0%, Co: 3.0-10. 0%, Ni: 1.0-4.0%, Y: 1.0-10.0% and the balance substantially consisting of Fe, increasing the hard primary carbide in the structure, by adding Co, Y An outer layer of a rolling roll characterized by combining wear resistance, crack resistance and low thermal expansion coefficient by increasing the amount of secondary carbide in the outer layer structure that precipitates during tempering and strengthening the base is described. .
[0006]
Further, in Patent Document 3, the components of the outer layer are C: 1.0 to 2.5%, Si: 0.2 to 2.0%, Mn: 0.3 to 1.0%, Cr: 2.0-8.0%, Mo: 0.5-6.0%, W: 0.5-8.0%, V: 0.5-8.0%, Co: 2.0-6. 0%, Nb: 0.1 to 5.0% and the balance substantially consisting of Fe, and the hardness of the roll outer shell layer at 700 ° C is 400 or more in terms of Vickers hardness, and the compressive residual stress is 30 to 50 kgf / mm 2 , the outer layer of the rolling roll is described. According to this publication, the high temperature hardness of the entire outer layer is disclosed, but the base hardness of the outer layer and the idea of increasing it are not disclosed.
[0007]
[Patent Document 1]
International Publication No. WO88 / 07594 (Patent Document 2)
Japanese Patent No. 2999472 [Patent Document 3]
Japanese Patent Laid-Open No. 9-78186
[Problems to be solved by the invention]
In recent years, rolling conditions have become severe, and higher wear resistance has been required. For this reason, the high-speed outer layer is composed of a structure in which hard carbides are increased, and further attempts to improve the wear resistance of the outer layer by adding Co, Nb or the like. However, when the amount of the carbide is increased, the toughness of the outer layer of the roll is lowered, and there is a problem that the crack resistance is deteriorated. For this reason, it is actually difficult to have both excellent wear resistance and crack resistance in the roll for rolling, and either wear resistance or crack resistance should be distributed according to the application of the roll for rolling. I had to make it in consideration.
[0009]
Therefore, an object of the present invention is to solve the problems in the high-speed roll material and to provide a rolling roll excellent in wear resistance and crack resistance.
[0010]
[Means for Solving the Problems]
As a result of intensive investigations, the inventors of the present invention have a relatively low hardness among the generated carbides and cause deterioration of wear resistance, and cracks propagate along grain boundaries to deteriorate crack resistance. Therefore, it is necessary to suppress as much as possible M 7 C 3 and M 23 C 6 carbides that cause the generation. In particular, MC, M 4 C 3 , M 2 C, and M 6 C carbides that contribute particularly to wear resistance are generated in an optimal range by making the balance of C, V, Mo, and W optimal. There is a need. Moreover, the roll outer layer surface temperature reaches a high temperature of about 600 ° C. Therefore, it was considered that the greatest feature of the present invention is that the wear resistance can be further improved by strengthening not only carbides but also the outer layer base at 600 ° C. during actual rolling. Furthermore, it was considered necessary to keep M 2 C and M 6 C carbides, which cause crack resistance deterioration, in the optimum range. Based on these technical ideas, the present invention has been completed by obtaining knowledge that the roll surface structure in contact with the rolled material can be further strengthened to improve the wear resistance and crack resistance of the roll material.
[0011]
That is, in the roll for rolling of the present invention, the hardness of the roll outer layer surface in contact with the rolled material is a Shore hardness of 87 or more, the base hardness of the outer layer surface at 600 ° C. is a Vickers hardness of 350 or more, and the outer layer is By weight%, C: 1.0 to 2.6%, Cr: 4.0 to 10.0%, Mo: 5.0 to 10.0%, W: 0 to 5.0%, V: 3. Fe group containing 0 to 8.0% and satisfying 12.9% ≦ 2Mo + W ≦ 20.0%, 2Mo / W ≧ 3.0, 0.2% ≦ C−0.24V ≦ 0.7% It is an alloy .
[0012]
[Action]
In the roll for rolling of the present invention, the Shore hardness of the outer layer of the roll is 87 or more, and the outer layer base hardness at 600 ° C. is 350 or more in terms of Vickers hardness, so that the wear resistance can be remarkably improved. Therefore, it can be effectively used as a roll for hot rolling.
[0013]
The reason for limiting the content range of each component element in the present invention will be described.
[0014]
C: 1.0 to 2.6%
C is necessary for the formation of carbide for improving the wear resistance and the improvement of the hardness of the base during quenching and tempering by solid solution in the base. C produces carbides such as MC, M 4 C 3 , M 2 C, M 6 C, and M 7 C 3 that should be imparted with wear resistance. If C is less than 1.0%, the amount of carbide produced is insufficient and the wear resistance is poor. When C exceeds 2.6%, the wear resistance is good, but the crack resistance is lowered.
[0015]
Cr: 4.0-10.0%
Cr improves hardenability and increases hardness. If Cr is less than 4.0%, the effect is small. On the other hand, if it exceeds 10.0%, the retained austenite at room temperature increases, so that the number of tempering increases and this is not economical. Further, Cr forms M 7 C 3 and M 23 C 6 carbides having relatively low hardness, and if added in a large amount, these carbides become excessive and wear resistance deteriorates. A more preferable Cr content is 4.5 to 7.0%.
[0016]
Mo: 5.0 to 10.0%
Mo is necessary for improving the hardenability and obtaining the high temperature hardness of the base. It dissolves in the base tissue and improves hardenability. Moreover, it combines with C to produce hard M 2 C and M 6 C carbides. If Mo is less than 5.0%, the effect is small. On the other hand, if it exceeds 10.0%, too much M 2 C and M 6 C carbides are crystallized in the balance of C, V and Mo, and the crack resistance is lowered.
[0017]
W: 0 to 5.0%
W is necessary for improving the hardenability and obtaining the high-temperature hardness of the base like Mo. The hardenability of the base is increased and combined with C to form hard M 2 C and M 6 C carbides. The lower limit of W is 0%. On the other hand, if it exceeds 5.0%, M 6 C carbide increases, which is not preferable in terms of crack resistance and rough skin resistance.
[0018]
V: 3.0-8.0%
V forms MC, M 4 C 3 , which is a hard carbide that contributes most to the improvement of wear resistance. When V is less than 3.0%, the generation of carbide is small and the wear resistance is deteriorated. When V exceeds 8.0%, MC and M 4 C 3 carbides are crystallized as primary crystals due to the balance with the C content of the present invention. If MC and M 4 C 3 are crystallized as primary crystals, they aggregate during solidification, and when used as a roll for rolling, the aggregate segregation of MC and M 4 C 3 which are hard carbides is transferred to the material to be rolled. It is not preferable.
[0019]
12.0% ≦ 2Mo + W ≦ 20.0%
Mo and W have similar effects in terms of improving hardenability and carbide formation. When viewed in terms of weight ratio, Mo has an effect approximately twice that of W due to the difference in atomic weight. One of the most characteristic features of the present invention is the correlation between Mo and W content, Shore hardness, and high temperature hardness. When 2Mo + W is 12.0% or more, the hardenability is significantly improved, and a Shore hardness of 87 or more can be stably secured, and the Vickers hardness of the base at 600 ° C. can be set to 350 or more. On the other hand, if 2Mo + W exceeds 20.0%, a large amount of M 2 C and M 6 C carbides are crystallized too much, which is not preferable.
[0020]
2Mo / W ≧ 3.0
Mo and W have substantially the same effect on carbide formation and increase in high-temperature base hardness, but Mo has an effect of improving the base viscosity with respect to W. In addition, W has a larger effect of crystallizing M 6 C carbide in the formation of carbide compared to Mo. There are M 2 C and M 6 C as carbides formed by Mo and W, but M 6 C tends to be coarser than M 2 C crystallized during solidification. From these facts, when the above 12.0% ≦ 2Mo + W ≦ 20.0% is satisfied, if a large amount of W is added, the high-temperature base hardness is improved, but coarse M 6 C is crystallized, and crack resistance is not improved. Therefore, it is better to add more Mo. By setting 2Mo / W ≧ 3.0, the high-temperature base hardness can be sufficiently improved, and crack resistance can be improved by preventing crystallization of coarse M 6 C.
[0021]
0.2% ≦ C−0.24V ≦ 0.7%
When there is too much content of V, since C will be taken by VC carbide | carbonized_material, C content of a base structure will run short, and the hardness after hardening will become low. When there is too little content of V, VC carbide | carbonized_material will run short and hardness will become low. Therefore, if the condition of 0.2% ≦ C−0.24V ≦ 0.7% considering the balance of C and V is satisfied, a Shore hardness of 87 or more can be secured stably and the Vickers hardness of the base Can be made 350 or more at 600 ° C.
[0022]
Further, the content of Si is preferably 0.1 to 3.0% as a component element of the roll material of the present invention. Since Si acts as a deoxidizer and is contained in M 6 C carbide as a solid solution by substituting elements such as W and Mo, in order to save expensive elements such as W and Mo It is valid. If Si is less than 0.1%, the deoxidation effect is insufficient and casting defects are likely to occur. Moreover, when it exceeds 3.0%, embrittlement tends to occur.
[0023]
Moreover, the peak temperature in the part which is in contact with the rolling material on the outermost surface of the roll for hot rolling is estimated to be about 600 ° C. When the Vickers hardness of the base at 600 ° C. is less than 350, the base is liable to cause plastic flow, inferior in wear resistance and rough skin resistance, and further, strip peeling or seizure of the black skin is likely to occur. Therefore, the hardness of the base at 600 ° C. is preferably Vickers hardness of 350 or more, more preferably Vickers hardness of 400 or more.
[0024]
The Mn content is preferably 0.1 to 3.0%. Mn has a deoxidizing action like Si. Moreover, there exists an effect | action which fixes S which is an impurity as MnS. When Mn is less than 0.1%, deacidification is poor. On the other hand, if it exceeds 3.0%, retained austenite tends to be generated, and sufficient hardness cannot be maintained stably.
[0025]
The roll for rolling of the present invention is manufactured by a centrifugal casting method, a casting overlay method, or the like. Among these, a centrifugal casting method that is advantageous in terms of production cost is more preferable. In addition, a composite roll in which the roll material of the present invention is used as an outer layer and is metal-bonded to the inner layer is preferable, but it can be naturally applied to a single roll formed of the roll material of the present invention.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Examples of the rolling material of the present invention will be described below.
[0027]
In the chemical composition (% by weight) of the rolling material shown in Table 1, No. Nos. 1 to 4 according to the inventive examples, Each sample material of Comparative Examples 5 to 10 was heated and melted to 1500 to 1550 ° C., and cast into a cylindrical mold having a diameter of 90 mm and a height of 90 mm. After cooling, the ingot was taken out, quenched at 1000 to 1200 ° C., and tempered three times at 500 to 600 ° C.
[0028]
Then, the test piece for hardness measurement was extract | collected from the center part of the ingot. For the hardness, the hardness of the surface of each test material was measured with a Shore hardness meter and a high temperature hardness meter. The high temperature hardness was measured according to JIS Z2252. At this time, the preheating time of the sample was 10 minutes.
[0029]
Specimen No. 1-4 are adjusted within the component ranges of C, Cr, Mo, W, and V recited in the claims of the present invention, and further satisfy the respective conditions of 2Mo + W, 2Mo / W, and C-0.24V of the present invention. To do. In addition, specimen No. 5 to 11 deviate from any of the conditions of 2Mo + W, 2Mo / W and C-0.24V of the present invention.
[0030]
[Table 1]
[0031]
From Table 1, as for the Shore hardness, the test material No. In 1-4, all conditions of 2Mo + W, 2Mo / W, and C-0.24V were satisfied, and it was confirmed that a Shore hardness of 87 or more could be stably obtained.
[0032]
Similarly, from Table 1, specimen No. which is an example of the present invention. 1-4, all conditions of 2Mo + W, 2Mo / W, and C-0.24V were satisfied, and it was confirmed that the Vickers hardness of the base at 600 ° C. was stably obtained to 350 or more.
[0033]
In addition, the test sample No. 5-11, it is outside the condition of 2Mo + W, 2Mo / W and C-0.24V, which is a feature of the present invention. Therefore, the Shore hardness is 87 or more and the Vickers hardness of the base at 600 ° C is 350 or more at the same time. I was not satisfied.
[0034]
In addition, using a centrifugal casting machine, the test material No. A centrifugally cast composite roll for hot rolling having a body diameter of 600 mm and a body length of 1830 mm having 1 component in the body outer layer was produced. The roll had a shore hardness of 88 and a Vickers hardness of 413 based on the outer layer surface at 600 ° C. Furthermore, after conducting a structure inspection at the end of the body and a non-destructive ultrasonic inspection to investigate the structure and defects, it was confirmed that the roll was healthy. When subjected to actual rolling, it was found that it was superior in wear resistance and crack resistance resulting from rolling operations as compared to conventional centrifugal cast composite rolls.
[0035]
【The invention's effect】
The roll for rolling of the present invention has a high hardness with a Shore hardness of 87 or more and a high hardness of the outer layer base at 600 ° C. with a hardness of 350 or more, and the hardness of the roll outer layer surface in contact with the rolled material is high, Excellent wear resistance and crack resistance, and stable rolling can be performed.
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