JP2960496B2 - Cold tool steel - Google Patents
Cold tool steelInfo
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- JP2960496B2 JP2960496B2 JP21099690A JP21099690A JP2960496B2 JP 2960496 B2 JP2960496 B2 JP 2960496B2 JP 21099690 A JP21099690 A JP 21099690A JP 21099690 A JP21099690 A JP 21099690A JP 2960496 B2 JP2960496 B2 JP 2960496B2
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Description
【発明の詳細な説明】 〔産業上の利用分野〕 本発明は、主として冷間で使用される鍛造用金型材料
に適する冷間工具鋼に関するものである。DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a cold tool steel suitable for a forging die material mainly used in a cold state.
従来、冷間鍛造用金型材には、JIS SKD11のような高
C−高Cr鋼が主に用いられてきたが、より耐衝撃性が要
求される用途に対しては高速度工具鋼系の金型材料を使
用することにより、金型寿命の改善ならびに冷間鍛造の
適用拡大が進んできた。高速度工具鋼系の金型材料とし
ては、一般にJIS SKH51が用いられているが、さらに厳
しい用途に対しては特公昭42−20619号、特公昭50−108
08号、特公昭55−49148号、特公昭57−24063号、特公昭
62−8503号、特開平1−159349号に開示されるような低
合金高速度工具鋼が開発、使用されてきた。Conventionally, high C-high Cr steels such as JIS SKD11 have been mainly used for mold materials for cold forging, but for applications requiring more impact resistance, high-speed tool steel The use of mold materials has improved the mold life and expanded the application of cold forging. JIS SKH51 is generally used as a high-speed tool steel-based mold material, but for more severe applications, Japanese Patent Publication No. 42-20609 and Japanese Patent Publication No. 50-108
08, JP-B 55-49148, JP-B 57-24063, JP-B
Low alloy high speed tool steels as disclosed in JP-A-62-28503 and JP-A-1-159349 have been developed and used.
しかしながら、近年被加工材の難加工化や鍛造形状の
複雑化、精密化が進んだ結果、従来の高速度工具鋼系の
材料では十分な金型寿命が得られない場合が多くなって
きた。その主な原因は金型材料の靭性、特に材料鍛伸方
向に平衡な方向(L方向)の靭性に比べ直角な方向(T
方向)の靭性不足による割れ、欠け等であり、これを改
善するためにさらに靭性の高い材料が望まれている。一
方、耐摩耗性、疲労強度を向上させるためには、硬さの
高い材料が必要とされる。However, in recent years, as a result of difficult processing of a work material and complicated and refined forged shapes, a sufficient mold life cannot be obtained with a conventional high-speed tool steel-based material in many cases. The main cause is the toughness of the mold material, especially the direction perpendicular to the direction (T
Direction) due to insufficient toughness, cracking, chipping, and the like. To improve this, a material with higher toughness is desired. On the other hand, to improve wear resistance and fatigue strength, a material having high hardness is required.
本発明の目的は、HRC61〜64の高硬度を有し、かつ従
来鋼よりもL方向およびT方向に関し高靭性を有する冷
間鍛造金型用に最適な冷間工具鋼を提供することであ
る。An object of the present invention is to provide a cold work tool steel having a high hardness of HRC 61 to 64 and having higher toughness in the L direction and the T direction than conventional steel, which is optimal for a cold forging die. .
本発明者らは高硬度、高靭性の材料を得るために、次
のような検討を行なった。The present inventors have conducted the following studies in order to obtain a material having high hardness and high toughness.
まず、靭性向上のためには、巨大一次炭化物の低減、
炭化物の縞状組織の低減、組織微細化等について検討し
た。さらに高靭性でかつ高硬度を得るために各元素の単
独と添加量のみならず各元素間の相互作用についても詳
細に検討した結果、添加元素量を所定の狭い範囲に限定
することにより、従来鋼では得られなかった高硬度域
(HRC61〜64)で高い靭性を有する鋼を得ることが可能
であるとの知見を得、本発明を完成するに至った。First, in order to improve toughness, reduction of huge primary carbides,
The reduction of the stripe structure of the carbide, the refinement of the structure, and the like were studied. Furthermore, in order to obtain high toughness and high hardness, not only the individual and the amount of each element but also the interaction between each element were examined in detail.As a result, by limiting the amount of the added element to a predetermined narrow range, The inventors have found that it is possible to obtain a steel having high toughness in a high hardness region (HRC 61 to 64), which cannot be obtained with steel, and have completed the present invention.
すなわち、本発明のうちの第1発明は、重量%でC 0.
5%以上0.7%未満、Si 0.5〜1.5%、Mn 1.5%以下、Cr
3.5〜6.5%、WおよびMoの1種または2種を1/2W+Moで
2.0〜3.5%、V 0.8〜1.5%、Nb 0.05〜0.20%、残部Fe
および不可避的不純物からなる組成を有し、不可避的不
純物のうち、Nが300ppm以下、Pが0.02%以下であるこ
とを特徴とする冷間工具鋼であり、第2発明は、重量%
でC 0.5%以上0.7%未満、Si 0.6%を越え1.0%以下、M
n 1.5%以下、Cr 3.5〜6.5%、WおよびMoの1種または
2種を1/2W+Moで2.0〜3.5%、V 1.0%を越え1.5%以
下、Nb 0.05%以上0.15%未満、残部Feおよび不可避的
不純物からなる組成を有し、不可避的不純物のうち、N
が300ppm以下、Pが0.02%以下であることを特徴とする
冷間工具鋼であり、第3発明は、Nbが0.05%以上0.1%
未満である第2発明に記載の冷間工具鋼であり、第4発
明は、1.5%以下のNiを含む第1ないし第3発明のいず
れかに記載の冷間工具鋼であり、第5発明は5%以下の
Coを含む第1ないし第4発明のいずれかに記載の冷間工
具鋼であり、第6発明は、不可避的不純物のうちSが0.
005%以下、Oが30ppm以下である第1ないし第5発明の
いずれかに記載の冷間工具鋼である。That is, the first invention of the present invention is C.O.
5% or more and less than 0.7%, Si 0.5-1.5%, Mn 1.5% or less, Cr
3.5-6.5%, one or two of W and Mo at 1 / 2W + Mo
2.0-3.5%, V 0.8-1.5%, Nb 0.05-0.20%, balance Fe
A cold tool steel comprising N and 300 ppm or less of P and 0.02% or less of the inevitable impurities.
With 0.5% or more and less than 0.7% of C, more than 0.6% of Si and less than 1.0%, M
n 1.5% or less, Cr 3.5 to 6.5%, one or two of W and Mo at 1 / 2W + Mo 2.0 to 3.5%, V over 1.0% and 1.5% or less, Nb 0.05% or more and less than 0.15%, balance Fe and It has a composition consisting of unavoidable impurities, and among the unavoidable impurities, N
Is 300 ppm or less, and P is 0.02% or less.
The fourth invention is the cold tool steel according to any one of the first to third inventions, which contains 1.5% or less of Ni, and the fifth invention Is less than 5%
The cold tool steel according to any one of the first to fourth inventions containing Co, wherein the sixth invention is characterized in that S in the inevitable impurities has a content of 0.1%.
The cold tool steel according to any one of the first to fifth inventions, wherein 005% or less and O is 30 ppm or less.
本発明の成分限定理由について述べる。 The reasons for limiting the components of the present invention will be described.
Cは、Cr、W、Mo、V、Nbなどの炭化物形成元素と結
合して硬い一次炭化物を形成し、耐摩耗性を向上させ
る。また、高温焼もどしにおいて、Mo、W、V、Nb等の
2次硬化元素と結びつき、2次炭化物として析出するこ
とにより、高さを増加させる。さらに一部は基地中に固
溶し基地を強化する。HRC61以上の硬さを得るためには
0.5%以上必要であるが、過度に添加すると、炭化物量
が多くなり靭性を低下させる。本発明鋼においては靭性
重視の観点から上限を0.7%未満とした。したがってC
量は0.5%以上で0.7%未満の範囲に限定した。C combines with carbide forming elements such as Cr, W, Mo, V, and Nb to form a hard primary carbide, and improves wear resistance. Further, in high-temperature tempering, the height is increased by combining with secondary hardening elements such as Mo, W, V, and Nb and precipitating as secondary carbide. In addition, a part is dissolved in the base to strengthen the base. To obtain hardness of HRC61 or more
0.5% or more is necessary, but if added excessively, the amount of carbides increases and the toughness decreases. In the steel of the present invention, the upper limit is set to less than 0.7% from the viewpoint of emphasizing toughness. Therefore C
The amount was limited to a range of 0.5% or more and less than 0.7%.
Siは基地中に固溶することにより、基地の硬さを高め
る効果を有するが、過度に添加すると靭性を低下させ
る。HRC60以下の硬度で使用される温熱間型用鋼におい
ては、特開平2−8347号に記載の鋼のように靭性を重視
してSi量が0.6%以下に限定されている。また、一方特
公昭55−49148号、特公昭57−24063号に開示されている
鋼は、Siによる硬さ向上を狙ってSiは概ね1.0%を越
え、1.4〜1.5%を中心にして添加されている。Si has an effect of increasing the hardness of the matrix by forming a solid solution in the matrix, but if added excessively, it lowers the toughness. In a hot working steel used at a hardness of 60 or less in HRC, the amount of Si is limited to 0.6% or less in consideration of toughness as in the steel described in JP-A-2-8347. On the other hand, in the steels disclosed in JP-B-55-49148 and JP-B-57-24063, in order to improve the hardness by Si, Si generally exceeds 1.0% and is added mainly in the range of 1.4 to 1.5%. ing.
本発明の目的とする高硬度高靭性の鋼を得るために
は、他の元素量との関連によりSi量を最適化する必要が
ある。すなわち、後述するように硬さの向上はW,Mo等を
増やすことによる二次効果によっても図れるが、靭性確
保のためにはW,Moの添加は最小限に抑えることが望まし
いので、Siを所定量添加し、基地自体の高さを向上させ
ることが有効である。In order to obtain a steel with high hardness and toughness as an object of the present invention, it is necessary to optimize the amount of Si in relation to the amounts of other elements. That is, as will be described later, the hardness can be improved by the secondary effect of increasing W, Mo, etc., but it is desirable to minimize the addition of W, Mo to secure toughness. It is effective to add a predetermined amount to improve the height of the base itself.
本発明成分範囲においてはHRC61以上の硬さを得るた
めにはSiは0.5%以上必要であるが、1.5%を越えると靭
性が大巾に低下するのでSi量は0.5〜1.5%に限定した。In the component range of the present invention, 0.5% or more of Si is required in order to obtain a hardness of HRC 61 or more, but if it exceeds 1.5%, the toughness is greatly reduced, so the amount of Si is limited to 0.5 to 1.5%.
さらに、詳細な検討の結果によれば、Si量の硬さへの
寄与は1.0%を越えると飽和する傾向にあるので、靭性
を特に考慮する場合にはSi量は0.6%を越え1.0%以下と
するのが望ましい。Further, according to the result of the detailed examination, the contribution of the Si content to the hardness tends to saturate when it exceeds 1.0%. Therefore, when the toughness is particularly considered, the Si content exceeds 0.6% and is 1.0% or less. It is desirable that
Mnは通常脱酸剤として添加されるが、焼入性改善にも
有効な元素である。しかし、過度に添加すると熱間にお
ける加工性を害するため、1.5%以下に限定した。Mn is usually added as a deoxidizing agent, but is also an effective element for improving hardenability. However, excessive addition impairs hot workability, so the content was limited to 1.5% or less.
Crは、焼入性を向上させると共に、Cと結合して炭化
物を形成し、耐摩耗性を向上させる。この効果を得るた
めには3.5%以上必要であるが、6.5%を越えると巨大炭
化物や、炭化物の縞状偏析を生成し、靭性を低下させ
る。したがってCr量は3.5〜6.5%に限定した。Cr improves hardenability and combines with C to form a carbide, thereby improving wear resistance. To obtain this effect, 3.5% or more is required. However, if it exceeds 6.5%, giant carbides and stripe-like segregation of carbides are generated, and the toughness is reduced. Therefore, the Cr content was limited to 3.5-6.5%.
W,Moは単独または複合で添加することができ、Cと結
びついて1次炭化物を形成して耐摩耗性を向上させ、ま
た焼もどし時微細な2次炭化物を析出して強い2次効果
を示す元素である。Wの原子量は、Moの約2倍であるこ
とから、W,Moの1種または2種以上をMo当量(1/2W+M
o)として規定した。Mo当量が2.0%未満では十分な硬さ
が得られず、一方3.5%を越えると炭化物量が過度とな
り、また縞状に分布するため靭性が低下する。したがっ
て、1/2W+Moは2.0〜3.5%の範囲に限定した。W and Mo can be added alone or in combination to form a primary carbide in combination with C to improve wear resistance, and to precipitate a fine secondary carbide during tempering to have a strong secondary effect. Element. Since the atomic weight of W is about twice as large as that of Mo, one or more of W and Mo are converted to Mo equivalent (1 / 2W + M
o). If the Mo equivalent is less than 2.0%, sufficient hardness cannot be obtained, while if it exceeds 3.5%, the amount of carbides becomes excessive and the toughness is reduced due to the distribution in the form of stripes. Therefore, 1 / 2W + Mo is limited to the range of 2.0 to 3.5%.
VはCと結びついて凝固時に1次炭化物を形成し耐摩
耗性を向上させるとともに結晶粒を微細化することによ
り靭性を向上させる。また、2次効果元素であるため、
高温焼もどしによる硬さ増加に有効である。V量は0.8
%未満であると上記効果が得られず、また1.5%を越え
ると炭化物量が過度となり、また縞状に分布するため靭
性が低下する。したがって、V量は0.8〜1.5%の範囲に
限定した。V forms a primary carbide at the time of solidification in combination with C to improve wear resistance and to improve toughness by making crystal grains fine. Also, because it is a secondary effect element,
It is effective for increasing the hardness by high temperature tempering. V amount is 0.8
If it is less than 1.5%, the above effect cannot be obtained, and if it exceeds 1.5%, the amount of carbides becomes excessive, and the toughness is reduced due to the distribution in the form of stripes. Therefore, the amount of V was limited to the range of 0.8 to 1.5%.
また後述するように、Nb添加による過度のNbC形成を
防ぐためには、V量は1.0%を越え1.5%以下が望まし
い。Further, as described later, in order to prevent excessive formation of NbC due to the addition of Nb, the amount of V is desirably more than 1.0% and 1.5% or less.
Nbは本発明における重要な添加元素であり、靭性向上
に大きく寄与する元素である。すなわち、Nbは凝固時に
おける炭化物の晶出形態に影響をおよぼし、微細でかつ
固溶しにくい一次炭化物を形成する。Nb is an important additive element in the present invention, and is an element that greatly contributes to improvement in toughness. That is, Nb affects the crystallization morphology of carbides during solidification, and forms primary carbides that are fine and hardly form a solid solution.
本発明の目的とする高硬度を得るためには焼入加熱温
度を高くする必要があるが、その際、上記炭化物が結晶
粒の粗大化を防止するので、高靭性を得ることができる
のである。In order to obtain the high hardness intended in the present invention, it is necessary to increase the quenching heating temperature. At that time, since the carbide prevents the crystal grains from becoming coarse, high toughness can be obtained. .
しかしながら、Nb単独の一次炭化物(NbC)が多くな
りすぎるとこの炭化物は縞状に分布するために靭性は急
激に低下する。一次炭化物の晶出形態はNb量のみなら
ず、Cおよび他の炭化物形成元素の量によって影響され
るため、Nbの最適添加量は他の元素量と関連させて決定
する必要がある。However, if the primary carbide (NbC) of Nb alone becomes too large, the carbide is distributed in a striped manner, so that the toughness rapidly decreases. Since the crystallization form of the primary carbides is affected not only by the amount of Nb but also by the amounts of C and other carbide-forming elements, the optimum amount of Nb needs to be determined in relation to the amounts of other elements.
すなわち、Cが高目で、かつ炭化物形成元素であるW,
MoおよびVが相対的に低い場合、CとNbが結びついてNb
単独の一次炭化物が縞状にできやすく、靭性を低下させ
る要因となる。例えば、前述の特公昭57−24063号に記
載の鋼においては、V量が低目でかつNb量が高目である
ため、また特開平1−159349号に記載の鋼は、C,Nb量が
高目であるため、どちらもNbCが多くなり縞状に分布し
て靭性を低下させると考えられる。That is, C is a relatively high and carbide forming element W,
When Mo and V are relatively low, C and Nb combine to form Nb
A single primary carbide is likely to be striped, which is a factor in reducing toughness. For example, in the steel described in JP-B-57-24063, since the V content is low and the Nb content is high, the steel described in Japanese Patent Application Laid-Open No. 1-159349 has a low C and Nb content. Is high, it is considered that both increase NbC and are distributed in a striped form, thereby reducing toughness.
本発明の成分範囲においては、Nb添加の上記効果を得
るためには、Nb量は最低0.05%必要であるが、0.20%を
越えるとかえって靭性が低下する。したがってNb量は0.
05〜0.20%に限定した。In the component range of the present invention, in order to obtain the above effect of Nb addition, the amount of Nb must be at least 0.05%, but if it exceeds 0.20%, the toughness is reduced. Therefore, the Nb amount is 0.
Limited to 05-0.20%.
また炭化物形態を最適化し靭性向上効果を得るために
は、Nb量は0.05%以上015%未満の範囲が望ましく、さ
らに望ましくは0.05%以上の0.10%未満である。Also, in order to optimize the carbide form and obtain the effect of improving toughness, the Nb content is desirably in the range of 0.05% or more and less than 015%, and more desirably 0.05% or more and less than 0.10%.
Nは特公昭54−24063号に記載の鋼においては、Cの
添加量を少なくすると共に、オーステナイト結晶粒の粗
大化防止をねらって添加されている。しかしながら、本
発明者の検討によるとN量が増えることにより、凝固時
に晶出するMC型炭化物の晶出温度が高くなるため、MC型
炭化物が粗大化し、これは特にT方向の靭性を低下させ
る傾向がある。したがって、T方向の靭性向上を目的と
する本発明においては、Nを300ppm以下の低いレベルに
規制する必要がある。N is added in the steel described in JP-B-54-24063 in order to reduce the amount of C added and to prevent austenite crystal grains from becoming coarse. However, according to the study of the present inventors, the crystallization temperature of MC-type carbide crystallized at the time of solidification increases due to an increase in the amount of N, so that the MC-type carbide coarsens, which lowers the toughness particularly in the T direction. Tend. Therefore, in the present invention for improving the toughness in the T direction, it is necessary to regulate N to a low level of 300 ppm or less.
Niは基地に固溶し靭性改善の効果を有すると共に、焼
入性を付与する元素である。しかしながら、過度に添加
すると焼なまし硬さが過度に高くなり、加工性を低下さ
せるので添加するとしても1.5%以下とする。Ni is an element that forms a solid solution in the matrix, has an effect of improving toughness, and imparts hardenability. However, if added excessively, the annealing hardness becomes excessively high and the workability is deteriorated.
Coは基地に固溶し耐熱性の向上、耐焼付性の向上に有
効な元素である。しかしながら、過度に添加すると靭性
を低下させるので添加する場合には5%以下に限定し
た。Co is a solid solution in the matrix and is an element effective for improving heat resistance and seizure resistance. However, if added excessively, the toughness is reduced. Therefore, when added, the content is limited to 5% or less.
P,S,Oは、通常不純物元素として微量含有される。P
は結晶粒界に偏析(ミクロ偏析)し、粒界強度を低下さ
せるだけでなく、凝固時の基地偏析(マクロ偏析)を助
長し、材質の方向性の原因となる。P, S, and O are usually contained in trace amounts as impurity elements. P
Segregates at the crystal grain boundaries (micro-segregation), not only lowering the grain boundary strength, but also promotes matrix segregation (macro-segregation) during solidification and causes the directionality of the material.
SやOは主に非金属介在物として鋼中に存在し、疲労
強度等に悪影響を及ぼす。したがって、これらの不純物
元素量を低減することにより、靭性改善がなされる。高
硬度で使用される本発明鋼の場合、P 0.02%以下、S 0.
005%以下、O 30ppm以下を満足する場合に改善効果が得
られたので、この地以下にP,SおよびOを低減すること
が望ましい。S and O mainly exist in steel as nonmetallic inclusions, and adversely affect fatigue strength and the like. Therefore, the toughness is improved by reducing the amounts of these impurity elements. In the case of the steel of the present invention used for high hardness, P 0.02% or less, S 0.
Since an improvement effect was obtained when 005% or less and O 30 ppm or less were satisfied, it is desirable to reduce P, S and O below this level.
以下、本発明を実施例に基づき説明する。 Hereinafter, the present invention will be described based on examples.
供試鋼として第1表に示す成分組成の本発明鋼(No.
1、3〜7)、比較鋼(No.2、8〜11)、および従来鋼
(No.12〜19)を溶製し、鍛伸後所定の焼入、焼もどし
処理(全試料とも1160℃焼入れ、560℃×1hr焼もどしを
2回)を行なって試験に供した。但しNo.7,No.11試料に
ついては第1図に示すように焼入温度を変化させてその
影響を調べた。シャルピー衝撃試験用試料は、鍛伸方向
に平衡な方向(L方向)および直角な方向(T方向)か
ら採取し、10mmR試験片を作製した。As the test steel, the steel of the present invention (No.
1, 3 to 7), comparative steels (No. 2, 8 to 11) and conventional steels (No. 12 to 19) were melted and forged, predetermined quenching and tempering treatments (1160 for all samples) Quenching at 560 ° C. and tempering twice at 560 ° C. for 1 hour). However, as for the samples No. 7 and No. 11, the quenching temperature was changed as shown in FIG. Samples for the Charpy impact test were collected from a direction equilibrium with the forging direction (L direction) and a direction perpendicular to the forging direction (T direction) to prepare a 10 mmR test piece.
第1図は、他の合金成分がほとんど同一でNb量のみ異
なるNo.7とNo.11試料について、焼入温度を変えて、結
晶粒度と硬さを調べ、Nb添加の効果を見たものである。
両試料とも、焼入温度を高くするほど硬さは高くなる。
しかしNb無添加のNo.11試料は、焼入温度の上昇につれ
結晶粒が粗大化し靭性低下を招くため、焼入温度は実質
1140℃以下となり、従って硬さは最大HRC61で使用せざ
るを得ない。一方Nbを添加したNo.7試料は焼入温度を上
げても結晶粒がほとんど粗大化しないので、高硬度の状
態で使用できる。Fig. 1 shows the effect of Nb addition on No. 7 and No. 11 samples, in which other alloy components were almost the same and only the Nb content was different, by examining the crystal grain size and hardness by changing the quenching temperature. It is.
In both samples, the hardness increases as the quenching temperature increases.
However, in the case of No. 11 sample without Nb, the quenching temperature was substantially reduced because the crystal grains became coarse and the toughness decreased as the quenching temperature increased.
The temperature is below 1140 ° C, so the hardness has to be used at maximum HRC61. On the other hand, the No. 7 sample to which Nb was added can be used in a state of high hardness because the crystal grains hardly become coarse even when the quenching temperature is increased.
第2表に、本発明鋼、比較鋼、従来鋼に標準熱処理を
施した時の硬さおよびシャルピー衝撃値を示す。本発明
鋼はいずれもHRC61〜64の高い硬さを有しなおかつ比較
鋼、従来鋼に比べシャルピー衝撃値が高いレベルにあ
る。特にT方向のシャルピー衝撃値のレベルが高いのが
特徴である。これは、本発明鋼の成分バランス、特に
C、W、Mo、V量の適性化により炭化物量の適正化およ
び縞状偏析の低減、Si量の適正化による硬さと靭性のバ
ランスの最適化、Nb添加による結晶粒微細化ならびに不
純物量低下による靭性向上の効果によるものである。 Table 2 shows the hardness and the Charpy impact value of the steel of the present invention, the comparative steel, and the conventional steel when subjected to the standard heat treatment. The steels of the present invention all have a high hardness of HRC 61 to 64, and have a high Charpy impact value as compared with comparative steels and conventional steels. In particular, the characteristic is that the level of the Charpy impact value in the T direction is high. This is because the composition balance of the steel of the present invention, in particular, the optimization of the amount of carbides and the reduction of striped segregation by optimizing the amounts of C, W, Mo and V, the optimization of the balance between hardness and toughness by optimizing the amount of Si, This is due to the effect of refinement of crystal grains by adding Nb and improvement of toughness by reducing the amount of impurities.
本発明鋼(No.1、3〜7)の間で詳細に比較すると、
No.1はNo.3〜6と比較してSi量が高目のため、シャルピ
ー衝撃値はやや低い。したがって、Siの上限値は1.0%
とするのが望ましい。またNo.6は他の試料と比較して、
V量が低目のため前述したようにNbCがやや過多となり
シャルピー衝撃値はやや低く、Vの下限は1.0%を越え
るのがよい。A detailed comparison between the steels of the present invention (No. 1, 3 to 7) shows that
No. 1 has a slightly lower Charpy impact value because of a higher Si content than Nos. 3 to 6. Therefore, the upper limit of Si is 1.0%
It is desirable that In addition, No. 6 compared with other samples,
Since the amount of V is low, NbC is slightly excessive and the Charpy impact value is slightly low as described above, and the lower limit of V is preferably higher than 1.0%.
一方、比較鋼8,9は、N以外は本発明鋼と同一成分で
あるか、N量が多いこと、さらには不純物元素が高いレ
ベルにあるため、特にT方向のシャルピー衝撃値が低下
している。 On the other hand, the comparative steels 8 and 9 have the same components as the steel of the present invention except for N, or have a large amount of N, and have a high level of impurity elements. I have.
比較鋼10は、Si量を低目とし、代わりにMo量を高目と
して本発明鋼と同等の硬さを得ることを狙ったものであ
るが、シャルピー衝撃値は低下しており、前述のように
Mo増加による靭性低下が大きいことを示している。比較
例11はNb無添加材であり、結晶粒粗大化のためシャルピ
ー衝撃値は低い。Comparative steel 10 was intended to obtain a hardness equivalent to that of the steel of the present invention with a lower Si content and a higher Mo content instead, but the Charpy impact value was reduced, like
This indicates that the decrease in toughness due to the increase in Mo is large. Comparative Example 11 is an Nb-free material and has a low Charpy impact value due to coarsening of crystal grains.
従来鋼12(SKH51)および13,14はHRC62以上の硬さを
有するが、L方向、T方向の靭性共に低い。これは、C
量および1/2W+Mo量が高すぎるため過度の炭化物を形成
し、また縞状偏析を生じて靭性低下をまねいたものであ
る。従来鋼15は本発明鋼に近い組成を有するが、硬さは
やや低く、また靭性のレベルが本発明鋼より低い。これ
は第1にSiが高めであるためである。前述のようにSiは
硬さ確保のため必要であるが、過度になると靭性面に悪
影響を及ぼす。第2にVが高すぎる一方、Nbを含まない
ためである。Conventional steels 12 (SKH51) and 13, 14 have a hardness higher than HRC62, but have low toughness in both the L and T directions. This is C
Since the amount and 1 / 2W + Mo amount are too high, excessive carbides are formed and stripe-like segregation is caused, resulting in a decrease in toughness. Conventional steel 15 has a composition close to that of the steel of the present invention, but has a slightly lower hardness and a lower toughness level than the steel of the present invention. This is firstly because Si is relatively high. As described above, Si is necessary to secure hardness, but if it is excessive, it adversely affects toughness. Second, V is too high and does not contain Nb.
従来鋼16も本発明鋼に近い組成を有するが、C量がや
や低目であるため硬さがやや低く、またV量が低目でNb
量が高目であるため、NbCが過度となり合わせてNを必
須元素として含有しているため、特にT方向の靭性値が
低い。Conventional steel 16 also has a composition close to that of the steel of the present invention, but has a slightly lower hardness due to a slightly lower C content, and has a lower V
Since the amount is relatively high, NbC becomes excessive and N is contained as an essential element, so that the toughness value in the T direction is particularly low.
従来鋼17,18は本発明鋼より主としてC量が高いた
め、靭性は低いレベルにある。The conventional steels 17 and 18 have a higher C content than the steels of the present invention, and thus have a low level of toughness.
従来鋼19は、温熱間型用であり、本発明鋼とは用途が
やや異なっているが比較のため記載した。この鋼はSi量
を低くしており、靭性レベルは高いが硬さが本発明鋼よ
り大巾に低い。The conventional steel 19 is for a hot-working die and has a slightly different application from the steel of the present invention, but is described for comparison. This steel has a low Si content and has a high toughness level but a much lower hardness than the steel of the present invention.
第3表は焼付性を比較したものである。焼付性は、円
柱状の試料を高速で回転させながらその端面を相手材
(SCM415)に押しつけ、焼付が起こらない最大荷重(焼
付臨界荷重)を求め、SKH51の焼付臨界荷重を100として
指数で示した。本発明鋼はSKH51と同等以上の耐焼付性
を示し、特にCoを添加した試料(No.4,6)の耐焼付性が
大きいことがわかる。Table 3 compares the seizure properties. The seizure resistance is determined by pressing the end face against the counterpart material (SCM415) while rotating a cylindrical sample at high speed, and calculating the maximum load (seizure critical load) at which seizure does not occur. Was. It can be seen that the steel of the present invention exhibits seizure resistance equal to or higher than that of SKH51, and particularly the samples to which Co is added (Nos. 4 and 6) have high seizure resistance.
〔発明の効果〕 以上述べたように、本発明鋼は従来の冷間工具鋼より
も高硬度で、かつ特にT方向の靭性の著しい改善を中心
とする高靭性を兼備しているので、難加工材の冷間鍛造
あるいは複雑形状、精密形状の冷間鍛造における金型、
あるいは他の冷間工具に用いて長寿命を得ることができ
る。 [Effects of the Invention] As described above, the steel of the present invention has a higher hardness than the conventional cold tool steel, and also has a high toughness centering on a remarkable improvement in the toughness particularly in the T direction. Die for cold forging or complex shape, precision shape cold forging of processed material,
Alternatively, it can be used for other cold tools to obtain a long life.
第1図は、Nbを添加した本発明鋼とNb無添加の比較鋼に
ついて、焼入温度を変化させた時の、結晶粒度と硬さの
関係を示す図である。FIG. 1 is a diagram showing the relationship between the grain size and the hardness when the quenching temperature is changed for the steel of the present invention to which Nb is added and the comparative steel to which Nb is not added.
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 昭58−117863(JP,A) 特開 昭61−213349(JP,A) (58)調査した分野(Int.Cl.6,DB名) C22C 38/00 - 38/60 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-58-117863 (JP, A) JP-A-61-213349 (JP, A) (58) Fields investigated (Int. Cl. 6 , DB name) C22C 38/00-38/60
Claims (6)
1.5%、Mn 1.5%以下、Cr 3.5〜6.5%、WおよびMoの1
種または2種を1/2W+Moで2.0〜3.5%、V 0.8〜1.5%、
Nb 0.05〜0.20%、残部Feおよび不可避的不純物からな
る組成を有し、不可避的不純物のうち、Nが300ppm以
下、Pが0.02%以下であることを特徴とする冷間工具
鋼。C. 0.5% to less than 0.7% by weight of Si, 0.5% to less than 0.5% by weight.
1.5%, Mn 1.5% or less, Cr 3.5-6.5%, 1 of W and Mo
Species or 2 types at 1 / 2W + Mo 2.0-3.5%, V 0.8-1.5%,
A cold tool steel having a composition consisting of 0.05 to 0.20% Nb, the balance being Fe and unavoidable impurities, wherein, among the unavoidable impurities, N is 300 ppm or less and P is 0.02% or less.
を越え1.0%以下、Mn 1.5%以下、Cr 3.5〜6.5%、Wお
よびMoの1種または2種を1/2W+Moで2.0〜3.5%、V 1.
0%を越え1.5%以下、Nb 0.05%以上0.15%未満、残部F
eおよび不可避的不純物からなる組成を有し、不可避的
不純物のうち、Nが300ppm以下、Pが0.02%以下である
ことを特徴とする冷間工具鋼。2. A composition in which, by weight%, C is 0.5% or more and less than 0.7%, and Si is 0.6%.
1.0% or less, Mn 1.5% or less, Cr 3.5-6.5%, one or two of W and Mo at 1 / 2W + Mo 2.0-3.5%, V1.
0% to 1.5% or less, Nb 0.05% to less than 0.15%, balance F
A cold tool steel having a composition consisting of e and unavoidable impurities, wherein, among the unavoidable impurities, N is 300 ppm or less and P is 0.02% or less.
に記載の冷間工具鋼。3. The method according to claim 2, wherein Nb is at least 0.05% and less than 0.1%.
A cold tool steel according to claim 1.
いずれかに記載の冷間工具鋼。4. The cold work tool steel according to claim 1, which contains 1.5% or less of Ni.
ずれかに記載の冷間工具鋼。5. The cold work tool steel according to claim 1, comprising 5% or less of Co.
Oが30ppm以下である請求項1ないし5のいずれかに記
載の冷間工具鋼。6. S is 0.005% or less of unavoidable impurities,
The cold tool steel according to any one of claims 1 to 5, wherein O is 30 ppm or less.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP1-322366 | 1989-12-12 | ||
JP32236689 | 1989-12-12 |
Publications (2)
Publication Number | Publication Date |
---|---|
JPH03236445A JPH03236445A (en) | 1991-10-22 |
JP2960496B2 true JP2960496B2 (en) | 1999-10-06 |
Family
ID=18142842
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Application Number | Title | Priority Date | Filing Date |
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JP21099690A Expired - Fee Related JP2960496B2 (en) | 1989-12-12 | 1990-08-09 | Cold tool steel |
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Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN102181787A (en) * | 2011-04-12 | 2011-09-14 | 哈尔滨工业大学 | Refractory corrosion-resisting steel as well as preparation and heat treatment method thereof |
Families Citing this family (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
AT412000B (en) | 2003-04-24 | 2004-08-26 | Boehler Edelstahl Gmbh & Co Kg | Cold-worked steel with greater strength and increased ductility, used for, e.g., pressing tools and forgings, has specified composition |
JP2005206913A (en) * | 2004-01-26 | 2005-08-04 | Daido Steel Co Ltd | Alloy tool steel |
JP6529234B2 (en) * | 2014-09-22 | 2019-06-12 | 山陽特殊製鋼株式会社 | High speed tool steel with high toughness and softening resistance |
JP6654328B2 (en) * | 2015-05-14 | 2020-02-26 | 山陽特殊製鋼株式会社 | High hardness and high toughness cold tool steel |
JP6797465B2 (en) * | 2016-07-08 | 2020-12-09 | 山陽特殊製鋼株式会社 | High hardness matrix highs with excellent toughness and high temperature strength |
-
1990
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Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN102181787A (en) * | 2011-04-12 | 2011-09-14 | 哈尔滨工业大学 | Refractory corrosion-resisting steel as well as preparation and heat treatment method thereof |
CN102181787B (en) * | 2011-04-12 | 2012-11-21 | 哈尔滨工业大学 | Refractory corrosion-resisting steel as well as preparation and heat treatment method thereof |
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