JP2007154295A - Wear resistant cast steel and its production method - Google Patents

Wear resistant cast steel and its production method Download PDF

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JP2007154295A
JP2007154295A JP2005355011A JP2005355011A JP2007154295A JP 2007154295 A JP2007154295 A JP 2007154295A JP 2005355011 A JP2005355011 A JP 2005355011A JP 2005355011 A JP2005355011 A JP 2005355011A JP 2007154295 A JP2007154295 A JP 2007154295A
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cast steel
wear
martensite
resistant
work hardening
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Masaki Hamaguchi
Hideo Hatake
Hitoshi Ishida
Hirotomo Takanami
正記 浜口
英雄 畠
斉 石田
裕智 高浪
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Earth Technica:Kk
Kobe Steel Ltd
株式会社アーステクニカ
株式会社神戸製鋼所
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<P>PROBLEM TO BE SOLVED: To provide a wear resistant high Mn cast steel having excellent wear resistance and toughness, and to provide its production method. <P>SOLUTION: A low-carbon wear resistant cast steel having a specified martensite index, having a chemical componential composition for obtaining a composition in which δferrite is crystallized out as primary crystals and austenite is crystallized out at a peritectic temperature or below, and having a cast steel structure in which the volume fraction of low carbon martensite is 40 to 95%, and the balance retained austenite is obtained by reheating the cast steel under specified conditions, so as to be homogenized, and thereafter subjected the cast steel to quenching treatment under specified conditions. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

本発明は、耐摩耗性及び靱性に優れており、岩石を破砕するコーンクラッシャ、ジョークラッシャなどの破砕機の耐摩耗部材に用いて好適な耐摩耗性鋳鋼およびその製造方法に関するものである。   The present invention relates to a wear-resistant cast steel that is excellent in wear resistance and toughness, and that is suitable for use as a wear-resistant member of a crusher such as a cone crusher or a jaw crusher for crushing rocks, and a method for producing the same.

従来、破砕機などに用いられる耐摩耗部材には、耐摩耗性と靭性を合わせ持つ高Mn鋳鋼(JISG5131相当)が多用されてきた。高Mn鋳鋼は、そのマトリックスがオーステナイトで靭性が良く、また塑性変形を受けると、双晶変形あるいは積層欠陥により加工硬化が生じて、該塑性変形を受けた表面部の硬さが高くなるという特性を有している。このため、破砕機のライナー部材など衝撃を受ける耐摩耗部材では、衝撃を受けた部分の硬さが高くなり衝撃面の耐摩耗性が向上する。   Conventionally, high-Mn cast steel (corresponding to JIS G5131) having both wear resistance and toughness has been frequently used for wear-resistant members used in crushers and the like. High Mn cast steel has a characteristic that its matrix is austenite and has good toughness, and when subjected to plastic deformation, work hardening occurs due to twin deformation or stacking fault, and the hardness of the surface portion subjected to plastic deformation increases. have. For this reason, in a wear resistant member that receives an impact, such as a liner member of a crusher, the hardness of the impacted portion is increased and the wear resistance of the impact surface is improved.

ところで近年、この破砕機の処理能力の向上が求められ、破砕機の大型化、破砕圧力の高圧化が進められている。このため、このような使用条件の過酷化に対応できる耐摩耗性に優れた耐摩耗鋳鋼が強く要望されている。   By the way, in recent years, improvement of the processing capacity of the crusher has been demanded, and the crusher has been increased in size and crushing pressure has been increased. For this reason, there is a strong demand for wear-resistant cast steel with excellent wear resistance that can cope with such severe use conditions.

従来から、高Mn鋳鋼の耐摩耗性向上のために、種々の技術が提案されてきた(特許文献1、2、3、4、5、6参照)。
特開平8−260099号公報 特開平9−202941号公報 特開平10−8210号公報 特開平11−61339号公報 特開平11−343543号公報 特開2001−140039号公報
Conventionally, various techniques have been proposed to improve the wear resistance of high-Mn cast steel (see Patent Documents 1, 2, 3, 4, 5, and 6).
Japanese Patent Laid-Open No. 8-26099 Japanese Patent Laid-Open No. 9-202941 Japanese Patent Laid-Open No. 10-8210 JP 11-61339 A JP-A-11-343543 JP 2001-140039 A

しかし、これら高Mn鋳鋼は、靱性はシャルピー衝撃値で50J/cm2 程度と高いものの、その硬度は600Hv未満程度と低い。このため、特に、硬い岩石の破砕などでは磨耗が大きく、上記した破砕機の処理能力の向上に十分対応できていない。 However, these high Mn cast steels have high toughness of about 50 J / cm 2 in terms of Charpy impact value, but their hardness is as low as less than about 600 Hv. For this reason, wear is large especially in the crushing of hard rocks, etc., and the above-mentioned crushing machine cannot sufficiently improve the processing capacity.

また、この高Mn鋳鋼に代わって、高Cr鋳鋼を使用することも考えられる。しかし、これら高Cr鋳鋼は、その硬度は700Hv以上と高いものの、反対に靱性がシャルピー衝撃値で5J/cm2 未満程度と低い。このため、コーンクラッシャ、ジョークラッシャなどの破砕機の、大きな衝撃を受ける耐摩耗部材には使用できない。また、初期硬度が高いために、鋳鋼から破砕機の耐摩耗部材への機械加工が特に困難となる問題もある。 It is also conceivable to use high Cr cast steel instead of this high Mn cast steel. However, although these high Cr cast steels have a high hardness of 700 Hv or more, on the contrary, their toughness is as low as about 5 J / cm 2 in Charpy impact value. For this reason, it cannot be used for a wear-resistant member that receives a large impact of a crusher such as a cone crusher or a jaw crusher. In addition, since the initial hardness is high, there is a problem that machining from the cast steel to the wear-resistant member of the crusher becomes particularly difficult.

更に、SUS304等のステンレスなどの高合金鋼を使用することも考えられるが、これら高合金鋼も、マルテンサイト組織により、その硬度は600Hv程度と高いものの、やはり、靱性がシャルピー衝撃値で5J/cm2 未満程度と低い。このため、高Cr鋳鋼と同様の理由で、コーンクラッシャ、ジョークラッシャなどの破砕機の、大きな衝撃を受け、機械加工により製造されるような、耐摩耗部材には使用できない。 Furthermore, although it is conceivable to use high alloy steels such as stainless steel such as SUS304, the hardness of these high alloy steels is as high as about 600 Hv due to the martensite structure. It is as low as less than about cm 2 . For this reason, for the same reason as high Cr cast steel, it cannot be used for wear-resistant members that are produced by machining due to the great impact of crushers such as cone crushers and jaw crushers.

本発明は、かかる問題に鑑みなされたもので、耐摩耗性及び靱性に優れた耐摩耗性高Mn鋳鋼およびその製造方法を提供することを目的とする。   The present invention has been made in view of such problems, and an object thereof is to provide a wear-resistant high Mn cast steel excellent in wear resistance and toughness and a method for producing the same.

この目的を達成するために、本発明の耐摩耗性鋳鋼の要旨は、質量%で、C:0.1〜0.3%、Si:0.3〜1.0%、Mn:5〜15%、Cr:5〜15%、N:0.05〜0.2%、を含有するとともに、これら各元素の含有量が、95≧460−〔480×(%C)−21×(%Si)−8×(%Mn)−14(%Cr)−480×(%N)〕>50の関係を満たし、残部がFe及び不可避的不純物からなり、鋳鋼組織におけるマルテンサイトの体積分率が40%以上95%以下であり、残部が残留オーステナイトであることとする。   In order to achieve this object, the gist of the wear-resistant cast steel of the present invention is mass%, C: 0.1 to 0.3%, Si: 0.3 to 1.0%, Mn: 5 to 15 %, Cr: 5 to 15%, N: 0.05 to 0.2%, and the content of each of these elements is 95 ≧ 460− [480 × (% C) −21 × (% Si ) −8 × (% Mn) −14 (% Cr) −480 × (% N)]> 50, the balance is made of Fe and inevitable impurities, and the volume fraction of martensite in the cast steel structure is 40 % To 95%, and the balance is retained austenite.

また、上記目的を達成するために、本発明の耐摩耗性鋳鋼の製造方法の要旨は、上記要旨または後述する好ましい態様の耐摩耗性鋳鋼を製造する方法であって、上記または後述する化学成分組成を有する鋳鋼を鋳造した後に、この鋳鋼を再加熱して900〜1200℃の温度範囲で1〜50時間保持し、その後500℃以下の温度まで1℃/s以上の平均冷却速度で冷却する焼入れ処理し、鋳鋼組織におけるマルテンサイトの体積分率を40%以上95%以下、残部が残留オーステナイトとすることである。   In order to achieve the above object, the gist of the method for producing a wear-resistant cast steel of the present invention is a method for producing a wear-resistant cast steel of the above gist or a preferred embodiment described later, and the chemical components described above or below. After casting the cast steel having the composition, the cast steel is reheated and held in the temperature range of 900 to 1200 ° C. for 1 to 50 hours, and then cooled to a temperature of 500 ° C. or lower at an average cooling rate of 1 ° C./s or higher. It is a quenching treatment, and the volume fraction of martensite in the cast steel structure is 40% or more and 95% or less, and the balance is retained austenite.

本発明では、本発明高Mn鋳鋼を耐摩耗部材に機械加工する際の、マルテンサイトの加工硬化と、残留オーステナイトの加工誘起変態による硬化によって、機械加工硬化後の硬さ(耐磨耗性)を確保する。このために、成分組成としては非常に低い炭素量とし、この低炭素鋳鋼の焼入れ処理(水靱処理)によって、高Mn鋳鋼組織を、低炭素マルテンサイトを主体とした、残留オーステナイトと低炭素マルテンサイトの複合組織とする。   In the present invention, the hardness after work hardening (wear resistance) by work hardening of martensite and hardening by work-induced transformation of retained austenite when machining the high Mn cast steel of the present invention into a wear resistant member. Secure. Therefore, the component composition is very low carbon content, and by quenching treatment (water toughening treatment) of this low carbon cast steel, the high Mn cast steel structure is composed of residual austenite and low carbon martensite mainly composed of low carbon martensite. A complex organization of sites.

このような残留オーステナイトと低炭素マルテンサイト複合組織は、硬さと延性、靱性のバランスに優れ、加工硬化特性(加工硬化量、加工硬化能)に優れている。低炭素マルテンサイトは、加工硬化後の硬さはオーステナイトには劣るが、非常に延性に富む性質を持つ。本発明では、このような低炭素マルテンサイトと、加工誘起変態によりマルテンサイトに変態し、更に加工硬化により非常な硬さとなる残留オーステナイトの複合組織とする。   Such a retained austenite and low carbon martensite composite structure is excellent in balance between hardness, ductility, and toughness, and is excellent in work hardening characteristics (work hardening amount, work hardening ability). Low carbon martensite has a very ductile property, although the hardness after work hardening is inferior to austenite. In the present invention, a composite structure of such low carbon martensite and residual austenite that is transformed into martensite by work-induced transformation and becomes extremely hard by work hardening is obtained.

これによって、耐摩耗部材への機械加工前の鋳鋼の硬度(初期硬度)は比較的低く、靱性が高くなる。このため機械加工を容易にする。また、機械加工および耐摩耗材料として使用中に受ける衝撃力による、低炭素マルテンサイトの加工硬化と、残留オーステナイトの加工誘起変態による硬化によって、耐摩耗部材の硬度が非常に高くなる。また、延性も保持されるために、耐摩耗部材としての使用中に割れることが無く、優れた耐摩耗性を発揮する。   Thereby, the hardness (initial hardness) of the cast steel before machining into the wear-resistant member is relatively low and the toughness is increased. This facilitates machining. In addition, the hardness of the wear-resistant member becomes very high due to the work hardening of low carbon martensite due to the impact force applied during machining and wear-resistant materials and the hardening due to work-induced transformation of residual austenite. Moreover, since ductility is also maintained, it does not crack during use as a wear-resistant member, and exhibits excellent wear resistance.

このような残留オーステナイトと低炭素マルテンサイト組織との複合組織と、その加工硬化特性とを、本発明では、低炭素化、Cr含有量とN含有量の増加、および高Mn化によるNの固溶限増大と、焼き入れ処理などにより達成する。併せて、低炭素化と、高Mn化による炭素の固溶限増大とにより、Cr含有量増加によるCr炭化物生成を抑制して、靱性の低下を防止する。   In the present invention, the composite structure of such retained austenite and low carbon martensite structure and its work hardening characteristics are determined in the present invention by reducing the carbon content, increasing the Cr content and the N content, and increasing the Mn content. Achieved by increasing the solubility limit and quenching. At the same time, by reducing carbon and increasing the solid solubility limit of carbon by increasing Mn, the formation of Cr carbide due to the increase in Cr content is suppressed, and the deterioration of toughness is prevented.

この結果、高Mn鋳鋼製の耐摩耗部材あるいはコーンクラッシャ、ジョークラッシャなどの破砕機の岩石の破砕性能や高寿命を保障する。   As a result, the wear resistance member made of high Mn cast steel or the rock crushing performance and long life of crushers such as cone crusher and jaw crusher are ensured.

なお、従来でも、加工硬化を伴う機械加工として、自由鍛造、型鍛造などの塑性変形を伴う加工を鋳鋼に対して行い、耐摩耗部材とする。この機械加工の際には、当然、鋳鋼が加工硬化して、硬度が上昇する。しかし、従来の高Mn鋳鋼では、オーステナイト単相、マルテンサイト単相、あるいはオーステナイトとマルテンサイトとの複合などの、いずれの組織としても、本発明鋳鋼に比して、CやCr含有量などの化学成分組成の違いがあり、上記機械加工および耐摩耗材料として使用中に受ける衝撃力による、その加工硬化量は著しく小さい。   Conventionally, as machining with work hardening, machining with plastic deformation such as free forging and die forging is performed on cast steel to obtain a wear resistant member. In this machining, the cast steel is naturally work-hardened and the hardness is increased. However, in the conventional high Mn cast steel, any structure such as an austenite single phase, a martensite single phase, or a composite of austenite and martensite has a C or Cr content as compared with the cast steel of the present invention. There are differences in chemical composition, and the amount of work hardening due to the impact force applied during use as the above-mentioned machining and wear-resistant material is extremely small.

また、例えば、前記特許文献6などでも、高Mn鋳鋼の加工硬化特性を向上させて、耐摩耗部材の硬度を高め、耐摩耗性を向上させようとしている。しかし、この特許文献6で意図している加工硬化は、本発明のような、高Mn鋳鋼を耐摩耗部材に機械加工する際の加工硬化ではなく、耐摩耗部材使用時の岩石破砕の衝撃による塑性変形時に、加工誘起マルテンサイト変態を生じさせる意味での加工硬化である。即ち、特許文献6では、高Mn鋳鋼の組織をオーステナイトとマルテンサイトとの複合組織にした上で、耐摩耗部材使用時の岩石破砕の衝撃による塑性変形によって、オーステナイトに加工誘起マルテンサイト変態を生じさせ、これによって組織のマルテンサイトと前記塑性変形時の加工誘起マルテンサイトとにより、部材摩耗面の硬さを高め、耐摩耗性を得ようとする。   Further, for example, in Patent Document 6 and the like, the work hardening characteristics of high-Mn cast steel are improved, the hardness of the wear-resistant member is increased, and the wear resistance is improved. However, the work hardening intended in Patent Document 6 is not the work hardening when machining high-Mn cast steel into a wear-resistant member as in the present invention, but by the impact of rock crushing when using the wear-resistant member. This is work hardening in the sense of causing work-induced martensitic transformation during plastic deformation. That is, in Patent Document 6, the structure of high-Mn cast steel is made into a composite structure of austenite and martensite, and then processing-induced martensite transformation occurs in austenite due to plastic deformation due to the impact of rock fracture when using wear-resistant members. Thus, the hardness of the member wear surface is increased by the martensite of the structure and the work-induced martensite at the time of plastic deformation, thereby obtaining wear resistance.

しかし、このようなオーステナイトとマルテンサイトとの複合組織からなる高Mn鋳鋼では、低炭素マルテンサイト組織からなる本発明鋳鋼に比して、Cr含有量などの化学成分組成の違いも含め、機械加工における、その加工硬化量は著しく小さい。言い換えると、特許文献6は、前記した従来技術のように、機械加工における加工硬化量が小さいがゆえに、上記耐摩耗部材使用時の岩石破砕の衝撃による加工硬化塑性変形に、その加工硬化を頼らざるを得ないと言える。   However, high Mn cast steel composed of a composite structure of austenite and martensite, including the difference in chemical composition, such as Cr content, compared to the cast steel of the present invention composed of low carbon martensite structure. The amount of work hardening in is extremely small. In other words, Patent Document 6 relies on work hardening plastic deformation due to the impact of rock crushing when using the wear-resistant member because the work hardening amount in machining is small as in the above-described conventional technology. It can't be helped.

これに対して、本発明鋳鋼は、耐磨耗部材への常法による機械加工方法や加工量などの条件で、大きな加工硬化特性(加工硬化量)を得ることができる。即ち、大きな加工硬化特性を得るための、特別な加工方法や大きな加工量などの特別な条件は、全く不要である。   On the other hand, the cast steel of the present invention can obtain a large work hardening characteristic (work hardening amount) under conditions such as a conventional machining method and a processing amount for the wear resistant member. That is, special conditions such as a special processing method and a large processing amount for obtaining a large work-hardening property are completely unnecessary.

(鋳鋼の組成)
本発明の高Mn鋳鋼の化学成分組成(単位は全て質量%)について、各元素の限定理由を含めて、以下に説明する。
(Cast steel composition)
The chemical composition of the high Mn cast steel of the present invention (all units are mass%) will be described below, including the reasons for limiting each element.

本発明高Mn鋳鋼の化学成分組成は、残留オーステナイトとマルテンサイト複合組織を、鋳造時の凝固偏析を利用して得るために決定される。より具体的には、初晶でδフェライトが晶出し、包晶温度以下でオーステナイトが晶出する組成にする。このための基本的な化学成分組成は、C:0.1〜0.3%、Si:0.3〜1.0%、Mn:5〜15%、Cr:5〜15%、N:0.05〜0.2%、を含有するとともに、これら各元素の含有量が、95≧460−〔480×(%C)−21×(%Si)−8×(%Mn)−14(%Cr)−480×(%N)〕>50の関係を満たし、残部がFe及び不可避的不純物からなるものとする。   The chemical component composition of the high Mn cast steel of the present invention is determined in order to obtain the retained austenite and martensite composite structure by utilizing solidification segregation during casting. More specifically, the composition is such that δ ferrite crystallizes in the primary crystal and austenite crystallizes below the peritectic temperature. The basic chemical composition for this is as follows: C: 0.1-0.3%, Si: 0.3-1.0%, Mn: 5-15%, Cr: 5-15%, N: 0 0.05 to 0.2%, and the content of each of these elements is 95 ≧ 460− [480 × (% C) −21 × (% Si) −8 × (% Mn) −14 (% Cr) −480 × (% N)]> 50, and the balance is made of Fe and inevitable impurities.

本発明では、高Mn鋳鋼の耐摩耗性を高めるために、必要により、上記成分組成に対して、更に、耐摩耗性を高める元素を含有することを許容する。具体的には、Ni:0.3〜5.0%、Mo:0.3〜2.0%の1種または2種、および/またはTi、Nb、Zrの内の1種または2種以上を合計で0.1〜1.5%、選択的に含有させても良い。   In the present invention, in order to increase the wear resistance of the high Mn cast steel, it is allowed to contain an element that further increases the wear resistance, if necessary, with respect to the above component composition. Specifically, one or more of Ni: 0.3 to 5.0%, Mo: 0.3 to 2.0%, and / or one or more of Ti, Nb, and Zr May be selectively contained in a total of 0.1 to 1.5%.

C:0.1〜0.3%。
Cは、鋳鋼の焼入れ処理(水靱処理)によって、残留オーステナイトを含むマルテンサイト組織を得るための焼入れ性を確保する。また、鋳鋼の前記した加工硬化量を増すのに有効な元素である。
C: 0.1 to 0.3%.
C ensures the hardenability for obtaining the martensitic structure containing a retained austenite by quenching treatment (water toughening treatment) of cast steel. Further, it is an element effective for increasing the amount of work hardening of cast steel.

本発明では低C量であるにも関わらず、本発明組成範囲では、鋳造によって、Cが凝固偏析して、部分的に見かけ上Cが濃化している部位が生じる。このため、焼入れ時に、多くの部分は、延性や靱性に優れるマルテンサイト変態するものの、前記Cが濃化している部位が、比較的硬いオーステナイトとして残留することにより、残留オーステナイトを含む低炭素マルテンサイト組織となる。   In the present invention, in spite of the low C amount, in the composition range of the present invention, C is solidified and segregated by casting, resulting in a portion where C is apparently concentrated. For this reason, at the time of quenching, many parts undergo martensite transformation excellent in ductility and toughness, but the portion where the C is concentrated remains as relatively hard austenite, so that low carbon martensite containing residual austenite is contained. Become an organization.

これらの効果を発揮させるためには、Cは0.1%以上の含有量が必要である。一方、C含有量が0.3%を超えると、Cr7 3 などのCr炭化物がオーステナイト粒界沿いに析出しやすくなり、靱性が低下する。したがって、Cは0.1〜0.3%の範囲で含有させる。 In order to exert these effects, the C content needs to be 0.1% or more. On the other hand, if the C content exceeds 0.3%, Cr carbide such as Cr 7 C 3 tends to precipitate along the austenite grain boundaries, and the toughness decreases. Therefore, C is contained in the range of 0.1 to 0.3%.

従来において、高Mn鋳鋼に対し、Crを含有させる場合でも5%以下としていたのは、正に、このCr炭化物析出による靱性低下が予想されたからである。これに対して、本発明では、前記低炭素化により、Cr含有量増加によるCr炭化物生成を抑制して、靱性の低下を防止する。   In the past, the reason why the Cr content was 5% or less even when Cr was contained in the high-Mn cast steel was exactly because a decrease in toughness due to this Cr carbide precipitation was expected. On the other hand, in the present invention, by reducing the carbon content, the formation of Cr carbide due to the increase in Cr content is suppressed, thereby preventing a decrease in toughness.

Mn:5〜15%。
Mnは、Cの固溶限を大きくして、靱性を劣化させるCr炭化物の生成を抑制する。また、Nの固溶限を大きくして固溶N量を増大させ、鋳鋼の前記した加工硬化量を増す。これらの効果を発揮させるためには、5%以上の含有量が必要である。一方、Mn含有量が15%を超えると、却って靱性が低下する。したがって、Mnは5〜15%の範囲で含有させる。
Mn: 5 to 15%.
Mn increases the solid solubility limit of C and suppresses the formation of Cr carbides that degrade toughness. Further, the solid solubility limit of N is increased to increase the amount of solid solution N, and the amount of work hardening of the cast steel is increased. In order to exert these effects, a content of 5% or more is necessary. On the other hand, if the Mn content exceeds 15%, the toughness is lowered. Therefore, Mn is contained in the range of 5 to 15%.

Si:0.3〜1.0%。
Siは鋳造時の溶湯の流動性を確保し、また、溶解・精錬時の脱酸のために、0.3%以上の含有量が必要である。一方、含有量が1.0%を超えると炭化物の結晶粒界への析出を促進させて靭性低下を招く。したがって、Si含有量は0.3〜1.0%の範囲とする。
Si: 0.3-1.0%.
Si needs to have a content of 0.3% or more for ensuring fluidity of the molten metal during casting and for deoxidation during melting and refining. On the other hand, if the content exceeds 1.0%, precipitation of carbides at grain boundaries is promoted, resulting in a decrease in toughness. Therefore, the Si content is in the range of 0.3 to 1.0%.

Cr:5〜15%。
Crは、鋳鋼の前記した加工硬化特性を向上させて耐摩耗性を高める。また、Nの固溶限を大きくして固溶N量を増大させ、前記加工硬化量を増す。本発明では、前記した通り、粒界炭化物の析出を促進させて靱性の低下を招く恐れが無いので、これらの効果を発揮させるために、Crを5%以上含有させる。一方、Cr含有量が15%を超えると、窒化物などを形成して靱性が低下する。したがって、Crは5〜15%の範囲で含有させる。
Cr: 5 to 15%.
Cr improves the above-mentioned work hardening characteristics of cast steel and enhances wear resistance. Further, the solid solubility limit of N is increased to increase the amount of solid solution N, thereby increasing the work hardening amount. In the present invention, as described above, since precipitation of grain boundary carbides is promoted and there is no fear of lowering toughness, 5% or more of Cr is contained in order to exert these effects. On the other hand, if the Cr content exceeds 15%, nitrides and the like are formed and the toughness is lowered. Therefore, Cr is contained in a range of 5 to 15%.

N:0.05〜0.2%。
Nは、衝撃値を低くする晶出物、析出物を生成させることなく、鋳鋼の前記した加工硬化特性(加工硬化指数)を向上させて耐摩耗性を高める効果がある。この効果を発揮させるためには、Nを0.05%以上含有させる必要がある。一方、N含有量が0.2%を超えると、窒化物などを形成して靱性が低下する。したがって、Nは0.05〜0.2%の範囲で含有させる。
N: 0.05-0.2%.
N has the effect of improving the above-mentioned work hardening characteristics (work hardening index) of cast steel and improving the wear resistance without generating crystallized substances and precipitates that lower the impact value. In order to exhibit this effect, it is necessary to contain N 0.05% or more. On the other hand, if the N content exceeds 0.2%, nitrides are formed and the toughness is lowered. Therefore, N is contained in the range of 0.05 to 0.2%.

(マルテンサイト指数)
本発明では、更に、各元素が各々の含有量範囲を満たした上で、上記したC、Si、Mn、Cr、Nの各元素の含有量が、95≧460−〔480×(%C)−21×(%Si)−8×(%Mn)−14(%Cr)−480×(%N)〕>50の関係(以下、マルテンサイト指数と言う)を満たすものとする。
(Martensite index)
In the present invention, the content of each element of C, Si, Mn, Cr, and N is 95 ≧ 460− [480 × (% C) after each element satisfies the content range. −21 × (% Si) −8 × (% Mn) -14 (% Cr) −480 × (% N)]> 50 (hereinafter referred to as the martensite index).

本発明では、加工硬化後の硬さ(耐磨耗性)を確保するために、鋳鋼の焼入れ処理(水靱処理)によって、低炭素マルテンサイトを40%以上95%以下含み残部が残留オーステナイトとなる、マルテンサイト主体の残留オーステナイトとの複合組織とする。上記マルテンサイト指数(式)は、このための規定であって、上記マルテンサイト指数が50を超えた場合に、上記低炭素マルテンサイト組織が得られ、好ましくは70以上で上記低炭素マルテンサイト組織が安定的に得られる。上記マルテンサイト指数が50以下では、鋳鋼の焼入れ処理によっても、40%以上の上記低炭素マルテンサイト組織が得られない。   In the present invention, in order to ensure the hardness after work hardening (abrasion resistance), low carbon martensite is contained at 40% or more and 95% or less by the quenching treatment (water toughening treatment) of cast steel, and the balance is retained austenite. And a composite structure with retained austenite mainly composed of martensite. The martensite index (formula) is a rule for this, and when the martensite index exceeds 50, the low-carbon martensite structure is obtained, and preferably the low-carbon martensite structure is 70 or more. Can be obtained stably. When the martensite index is 50 or less, the low-carbon martensite structure of 40% or more cannot be obtained even by quenching the cast steel.

一方、上記マルテンサイト指数が95を超えた場合は、残留オーステナイトが不足して、残留オーステナイトの加工誘起変態による硬化が期待できなくなる。したがって、マルテンサイト指数の上限は95とし、上記マルテンサイト指数の範囲は、50を超えて95以下とする。   On the other hand, when the martensite index exceeds 95, the retained austenite is insufficient, and it cannot be expected that the retained austenite will be hardened by processing-induced transformation. Therefore, the upper limit of the martensite index is 95, and the range of the martensite index is more than 50 and 95 or less.

Ni:0.3〜5.0%。
Niは、Mn、Crと同様に加工硬化量を増し、耐摩耗性を高める効果がある。この効果を発揮させるために選択的に含有させる場合には、0.3%以上の含有量とする。一方、Ni含有量が5.0%を超えると、オーステナイトが安定化され過ぎて、残留オーステナイトの加工誘起変態が生じなくなる。このため耐摩耗性が低下する。したがって、選択的に含有させる場合のNiは0.3〜5.0%の範囲とする。
Ni: 0.3-5.0%.
Ni, like Mn and Cr, has the effect of increasing the work hardening amount and enhancing the wear resistance. In order to make this effect exhibited selectively, the content is made 0.3% or more. On the other hand, if the Ni content exceeds 5.0%, the austenite is overstabilized and the processing-induced transformation of residual austenite does not occur. For this reason, abrasion resistance falls. Therefore, Ni in the case of containing selectively is made into 0.3 to 5.0% of range.

Mo:0.3〜2.0%。
Moは、鋳鋼の焼入れ処理(水靱処理)過程での、粒界への炭化物の生成を抑制し、延性を向上させ、耐摩耗性を高める効果がある。Moのこの効果を得るためには、0.3%以上選択的に含有させる。一方、2.0%を超えると、却ってその効果が失われる。したがって、選択的に含有させる場合のMo量は0.3〜2.0%の範囲とする。
Mo: 0.3-2.0%.
Mo has the effect of suppressing the formation of carbides at the grain boundaries in the quenching process (water toughening process) of cast steel, improving the ductility, and increasing the wear resistance. In order to obtain this effect of Mo, 0.3% or more is selectively contained. On the other hand, if it exceeds 2.0%, the effect is lost. Therefore, the Mo amount in the case of selective inclusion is set in the range of 0.3 to 2.0%.

Ti、Nb、Zrを合計で0.1〜1.5%以下。
Ti、Nb、Zrは、炭化物を形成して析出することにより、鋳鋼の前記した加工硬化特性を向上させ、耐摩耗性を高める効果がある。また、結晶粒を微細化させて、加工硬化特性や靱性を向上させる効果もある。しかし、炭化物には、前記した通り、鋳鋼の焼入れ処理過程で粒界へ生成したり、窒化物を形成したりして、靱性や延性を低下させる作用もある。したがって、これらの元素の1種または2種以上を選択的に含有させる場合は、下限は合計の含有量で0.1%以上とし、その上限は合計の含有量で1.5%以下とする。
Ti, Nb, Zr is 0.1 to 1.5% or less in total.
Ti, Nb, and Zr have the effect of improving the above-mentioned work hardening characteristics of cast steel and increasing the wear resistance by forming carbides and precipitating. In addition, there is an effect of improving the work hardening characteristics and toughness by refining crystal grains. However, as described above, carbides also have an effect of reducing toughness and ductility by forming at grain boundaries or forming nitrides during the quenching process of cast steel. Accordingly, when one or more of these elements are selectively contained, the lower limit is 0.1% or more in terms of the total content, and the upper limit is 1.5% or less in terms of the total content. .

(鋳鋼組織)
本発明の鋳鋼組織は、高Mn鋳鋼を耐摩耗部材に機械加工および耐摩耗部材として試用中に受ける衝撃力によるマルテンサイトの加工硬化と、残留オーステナイトの加工誘起変態による硬化によって、耐摩耗部材として使用中の硬さ(耐磨耗性)を確保するために、鋳鋼の焼入れ処理(水靱処理)によって、残留オーステナイトと低炭素マルテンサイトとの複合組織とする。
(Cast steel structure)
The cast steel structure of the present invention is made into a wear-resistant member by machining hardened high-Mn cast steel to a wear-resistant member and by work hardening of martensite due to impact force received during trial use as a wear-resistant member and by processing-induced transformation of residual austenite. In order to ensure hardness (wear resistance) during use, a composite structure of retained austenite and low carbon martensite is formed by quenching treatment (water toughening treatment) of cast steel.

本発明で言う残留オーステナイトと低炭素マルテンサイトとの複合組織とは、図1に示す通り、低炭素マルテンサイト中に残留オーステナイトが分散した組織である。図1は、後述する実施例における発明例(マルテンサイトの体積分率が40%以上95%以下)の100倍程度の光学顕微鏡による組織観察写真(図面代用写真)である(測定方法は段落0051に記載)。図1において、黒い部分が主相の低炭素マルテンサイト、白い部分が残留オーステナイトである。   The composite structure of retained austenite and low carbon martensite in the present invention is a structure in which retained austenite is dispersed in low carbon martensite, as shown in FIG. FIG. 1 is a structure observation photograph (photograph substituted for drawing) with an optical microscope of about 100 times that of an invention example (a martensite volume fraction of 40% or more and 95% or less) in Examples described later (measurement method is paragraph 0051). Described in). In FIG. 1, the black part is the low-carbon martensite of the main phase, and the white part is the retained austenite.

この複合組織におけるオーステナイトは、結晶構造が面心立方晶であり、その熱力学的な性質により、体心立方晶であるマルテンサイトに比べて、C、Si、Mn、Cr、Nが多く分配されて高濃度になっている。このため、この複合組織におけるオーステナイトは、マルテンサイトよりも、加工誘起変態と合わせて摩耗条件での(摩耗部材としての使用中の)加工硬化量が大きく、より高い硬さとなる。   The austenite in this composite structure has a face-centered cubic crystal structure, and due to its thermodynamic properties, C, Si, Mn, Cr, and N are more distributed than martensite, which is a body-centered cubic crystal. The concentration is high. For this reason, the austenite in this composite structure has a higher work hardening amount under wear conditions (during use as a wear member) and higher hardness than martensite in combination with work-induced transformation.

一方、マルテンサイトが無いオーステナイト単一相にした場合、加工誘起変態と合わせて摩耗条件での加工硬化量が大きく、非常に高い硬さとなる。しかし、同時に靱性が低下するために、耐摩耗部材としての使用中に割れが生じる。これに対して、本発明の残留オーステナイトを含む低炭素マルテンサイト複合組織とすれば、低炭素マルテンサイト部分が延性を示し、靱性が確保されるために、耐摩耗部材としての使用中に割れることが無い。   On the other hand, when an austenite single phase without martensite is used, the work hardening amount under wear conditions is large together with the work-induced transformation, resulting in a very high hardness. However, since the toughness is lowered at the same time, cracking occurs during use as a wear-resistant member. On the other hand, if the low carbon martensite composite structure containing retained austenite of the present invention is used, the low carbon martensite portion exhibits ductility and toughness is ensured, so that it cracks during use as a wear resistant member. There is no.

低炭素マルテンサイトの本発明の鋳鋼組織に占める割合が40%未満では、言い換えると、他の残留オーステナイトなどが60%を超えた場合には、延性や靱性が低下する。このため、機械加工が困難となり、耐摩耗部材としての靱性や耐摩耗性も低下する。したがって、低炭素マルテンサイトの本発明の鋳鋼組織に占める割合は40%以上とする。好ましくは、その割合は50%以上、より好ましくは60%以上とする。また、反対に低炭素マルテンサイトの本発明の鋳鋼組織に占める割合が95%を超える場合には、残留オーステナイトの量が少なくなりすぎて、残留オーステナイトの効果が有効に発揮されなくなるため、その割合は95%以下とする。好ましくは、その割合は90%以下、より好ましくは85%以下とする。   When the proportion of low carbon martensite in the cast steel structure of the present invention is less than 40%, in other words, when other residual austenite exceeds 60%, ductility and toughness are lowered. For this reason, machining becomes difficult, and the toughness and wear resistance of the wear-resistant member also deteriorate. Accordingly, the proportion of low carbon martensite in the cast steel structure of the present invention is 40% or more. Preferably, the ratio is 50% or more, more preferably 60% or more. On the other hand, if the proportion of low carbon martensite in the cast steel structure of the present invention exceeds 95%, the amount of retained austenite becomes too small, and the effect of retained austenite cannot be exhibited effectively. Is 95% or less. Preferably, the ratio is 90% or less, more preferably 85% or less.

(製造方法)
本発明鋳鋼の好ましい製造条件について以下に説明する。本発明鋳鋼は、前記した化学成分組成を有する鋳鋼を鋳造した後に、室温まで一旦冷却する。その後、この鋳鋼を室温から再加熱して900〜1200℃の温度範囲で1〜50時間保持する均質化処理を行った後に、500℃以下の温度まで1℃/s以上の平均冷却速度で冷却する焼入れ処理(水靱処理)を水冷などによって行い、鋳鋼組織におけるマルテンサイトの体積分率を40%以上95%以下、残部を残留オーステナイトとする。
(Production method)
Preferred production conditions for the cast steel of the present invention will be described below. The cast steel of the present invention is once cooled to room temperature after casting the cast steel having the chemical composition described above. Thereafter, this cast steel is reheated from room temperature and subjected to a homogenization treatment in which the cast steel is maintained in a temperature range of 900 to 1200 ° C. for 1 to 50 hours, and then cooled to a temperature of 500 ° C. or less at an average cooling rate of 1 ° C./s or more. The quenching treatment (water toughening treatment) is performed by water cooling or the like, so that the martensite volume fraction in the cast steel structure is 40% or more and 95% or less, and the balance is retained austenite.

本発明の残留オーステナイトを含む低炭素マルテンサイト複合組織は、鋳造時の凝固偏析を利用して得る。このため、鋳造ままの鋼塊では、低炭素マルテンサイトとオーステナイトとの界面での含有元素の濃度勾配が比較的大きくなる(急となる)。このため、耐摩耗材としての使用中に加工硬化した場合に割れやすくなる。これを防止するためにも、上記濃度勾配を緩和する、上記条件での均質化処理が必要となる。   The low carbon martensite composite structure containing the retained austenite of the present invention is obtained by utilizing solidification segregation during casting. For this reason, in the as-cast steel ingot, the concentration gradient of contained elements at the interface between the low carbon martensite and austenite becomes relatively large (steep). For this reason, it becomes easy to crack when it is work-hardened during use as a wear-resistant material. In order to prevent this, it is necessary to perform a homogenization treatment under the above-mentioned conditions for relaxing the above-mentioned concentration gradient.

均質化処理温度については、900℃以下では上記濃度勾配を緩和することができない可能性が高い。一方、1200℃を超えると、均質化が進み過ぎて、鋳造時の凝固偏析を利用できなくなり、本発明の残留オーステナイトを含む低炭素マルテンサイト複合組織が得られない。   Regarding the homogenization temperature, it is highly possible that the concentration gradient cannot be relaxed at 900 ° C. or lower. On the other hand, when it exceeds 1200 ° C., homogenization proceeds too much, so that solidification segregation during casting cannot be used, and the low carbon martensite composite structure containing retained austenite of the present invention cannot be obtained.

均熱化処理時間については、上記濃度勾配を緩和するためには、少なくとも1時間以上が必要であり、一方、50時間を超えると均質化が進み過ぎて、鋳造時の凝固偏析を利用できなくなり、本発明の残留オーステナイトを含む低炭素マルテンサイト複合組織が得られない。   As for the soaking time, at least one hour or more is necessary to alleviate the above-mentioned concentration gradient. On the other hand, if it exceeds 50 hours, homogenization proceeds too much and solidification segregation during casting cannot be used. The low carbon martensite composite structure containing the retained austenite of the present invention cannot be obtained.

均熱化処理後の水冷などによる焼入れ処理は、残留オーステナイトを分散させた低炭素マルテンサイト主体の組織を得るために重要である。このような組織を得るために、また、結晶粒界への炭化物の析出を防止乃至抑制するためにも、鋳鋼の焼入れ処理時の冷却速度はできるだけ大きい方が望ましい。   Quenching treatment such as water cooling after soaking treatment is important for obtaining a structure mainly composed of low carbon martensite in which retained austenite is dispersed. In order to obtain such a structure and to prevent or suppress the precipitation of carbides at the grain boundaries, it is desirable that the cooling rate during the quenching treatment of the cast steel be as large as possible.

焼入れ処理後の鋳鋼は、加工硬化を伴う機械加工を施されて、耐磨耗部材とされる。この際の加工硬化を伴う機械加工とは、自由鍛造、型鍛造などの、常法による塑性変形を伴う加工である。即ち、本発明鋳鋼は、前記した通り、耐磨耗部材への常法による機械加工方法や加工量などの条件で、大きな加工硬化特性(加工硬化量)を得ることができ、特別な加工方法や大きな加工量などの特別な条件は一切不要である。これが、本発明の大きな利点でもある。この際、耐摩耗部材への機械加工前の高Mn鋳鋼の硬度(初期硬度)は比較的低いので、機械加工を容易にすることは、前記した通りである。   The cast steel after the quenching treatment is subjected to machining with work hardening to be a wear resistant member. The machining with work hardening at this time is a process with plastic deformation by a conventional method such as free forging or die forging. That is, as described above, the cast steel of the present invention can obtain a large work hardening characteristic (work hardening amount) under conditions such as a conventional machining method and a processing amount for wear-resistant members. There is no need for special conditions such as large machining amount. This is also a great advantage of the present invention. At this time, since the hardness (initial hardness) of the high Mn cast steel before machining on the wear resistant member is relatively low, the machining is facilitated as described above.

以下に本発明の実施例を説明する。成分組成、組織を種々変えた高Mn鋳鋼を得て、その硬度、加工硬化能、靱性、耐摩耗性などを各々評価した。   Examples of the present invention will be described below. High Mn cast steels with various composition and structure were obtained, and their hardness, work hardening ability, toughness, wear resistance, etc. were evaluated.

即ち、下記表1(発明例)、表2(比較例)に示す1〜4039の各組成の高Mn鋳鋼を高周波誘導溶解炉で、20kgの鋳鋼を各々溶製した。これら室温まで冷却した鋳鋼を、共通して、1100℃の温度に加熱して6時間保持する均質化処理を行い、しかる後に、水冷によって、500℃までを2℃/s平均冷却速度で焼入れ処理(水靱処理)し、室温まで冷却した。   That is, 20 kg of cast steel was melted in a high frequency induction melting furnace with high-Mn cast steel having the compositions 1 to 4039 shown in Table 1 (Invention Example) and Table 2 (Comparative Example) below. These cast steels cooled to room temperature are commonly heated to a temperature of 1100 ° C. and held for 6 hours, and then quenched by water cooling to 500 ° C. at an average cooling rate of 2 ° C./s. (Water toughening treatment) and cooled to room temperature.

これらの得られた各鋳鋼の中心部分より試験片をそれぞれ採取し、組織、硬度、加工硬化能、靱性、耐摩耗性などを各々評価した。これらの結果を表3(発明例)、表4(比較例)に示す。   Test pieces were sampled from the central portions of the obtained cast steels, and the structure, hardness, work hardening ability, toughness, wear resistance, etc. were evaluated. These results are shown in Table 3 (Invention Example) and Table 4 (Comparative Example).

組織:各試験片のマルテンサイト分率は、各試験片を鏡面研磨した後に、ナイタール溶液で腐食して、100倍の光学顕微鏡を用いて3視野測定した。これを画像解析ソフト(MEDIA CYBERNETICSTM社製Image-Pro Prus)で画像解析した。この画像解析では、内部に微細組織が見られない平滑な部分(前記図1の白い部分)を残留オーステナイト組織、それ以外の部分(前記図1の黒い部分)がマルテンサイト組織であるとし、前記視野内におけるマルテンサイト組織の合計測定面積を算出した。そして測定視野面積に対する、マルテンサイトの合計面積の割合から、マルテンサイトの分率(%)を算出し、3視野の結果を平均化し、マルテンサイトの体積分率とし、残部を残留オーステナイトの体積分率とした。   Tissue: The martensite fraction of each test piece was measured by three fields of view using a 100 × optical microscope after each test piece was mirror-polished and then corroded with a nital solution. This was image-analyzed with image analysis software (Image-Pro Prus made by MEDIA CYBERNETICSTM). In this image analysis, it is assumed that a smooth portion (white portion in FIG. 1) in which no fine structure is seen is a retained austenite structure, and the other portion (black portion in FIG. 1) is a martensite structure, The total measurement area of the martensite structure in the visual field was calculated. Then, the martensite fraction (%) is calculated from the ratio of the total area of martensite to the measured visual field area, the results of the three visual fields are averaged to obtain the volume fraction of martensite, and the remainder is the volume fraction of residual austenite. Rate.

硬度:ビッカース硬度計を用い、荷重を30kgとして、各試験片の表面硬度(Hv)を5点測定し、平均化したものを加工前の硬度とした。そして、加工硬化を伴う実際の機械加工および耐摩耗材として使用時に受ける衝撃力を模擬して、各試験片(Φ60mm×120mml)を、歪み速度10-3m/sで、50%圧縮加工した後の、各試験片の表面硬度(Hv)を5点測定し、平均化したものを加工後の硬度とした。そして、これら加工前と加工後との硬度差(ΔHv)を求めた。 Hardness: Using a Vickers hardness meter, the load was 30 kg, the surface hardness (Hv) of each test piece was measured at five points, and the averaged hardness was defined as the hardness before processing. Then, after simulating the actual machining with work hardening and the impact force received during use as a wear resistant material, each test piece (Φ60 mm × 120 mml) was subjected to 50% compression processing at a strain rate of 10 −3 m / s. The surface hardness (Hv) of each test piece was measured at five points, and the averaged hardness was taken as the hardness after processing. And the hardness difference ((DELTA) Hv) before and after these processes was calculated | required.

衝撃値:シャルピー衝撃試験により、2mmのUノッチのJIS3号試験片を用いて、ハンマー荷重:294.2N(30kgf)、試験温度:室温にて行った。なお、シャルピー衝撃値(J)は吸収エネルギーを試験片断面積で除して、J/cm2 として求めた。シャルピー衝撃値が70J/cm2 以上を合格と評価した。 Impact value: A Charpy impact test was performed using a 2 mm U-notch JIS No. 3 test piece at a hammer load of 294.2 N (30 kgf) and a test temperature of room temperature. The Charpy impact value (J) was determined as J / cm 2 by dividing the absorbed energy by the cross-sectional area of the test piece. A Charpy impact value of 70 J / cm 2 or higher was evaluated as acceptable.

耐磨耗性試験:コーンクラッシャーなどの実機破砕機を模擬して、耐磨耗性を評価した。即ち、各鋳鋼から6×25×75mmの板材を切り出し、耐磨耗性試験材とした。これらの試験材の耐磨耗性を図2に示す試験機によって評価した。具体的には、図2に示す試験機の固定された円筒状外容器内中心部の回転軸部に、試験材を回転軸とともに回転可能に装着、固定した。そして、円筒状外容器内に、SiO2 を75%含有する石英粗面岩塊を多数収容した上で、試験材を回転軸とともに反時計回りに、回転速度60rpmで420分間回転させ、石英粗面岩塊との衝突を繰り返させた。 Abrasion resistance test: Abrasion resistance was evaluated by simulating an actual machine crusher such as a cone crusher. That is, a plate material of 6 × 25 × 75 mm was cut out from each cast steel and used as an abrasion resistance test material. The abrasion resistance of these test materials was evaluated by a testing machine shown in FIG. Specifically, the test material was rotatably mounted and fixed together with the rotation shaft on the rotation shaft portion in the central portion of the cylindrical outer container to which the test machine shown in FIG. 2 was fixed. Then, after accommodating a large number of quartz rough rock blocks containing 75% SiO 2 in a cylindrical outer container, the test material was rotated counterclockwise with a rotating shaft at a rotational speed of 60 rpm for 420 minutes to obtain a coarse quartz The collision with the surface rock mass was repeated.

そして、試験前後での試験材の重量減少量から比摩耗量を算出した。比摩耗量(%)=〔(重量減少量:g)/(試験前重量:kg)〕×100。各例とも3個の試験材について行い、比摩耗量はこの平均値とした。そして、比摩耗量が0.4g/kg以下を合格(○)とし、それを越えるものを不合格(×)と評価した。   Then, the specific wear amount was calculated from the weight reduction amount of the test material before and after the test. Specific wear amount (%) = [(weight loss: g) / (weight before test: kg)] × 100. Each example was performed on three test materials, and the specific wear amount was the average value. And the specific abrasion loss made 0.4 g / kg or less into the pass ((circle)), and the thing exceeding it was evaluated as the disqualification (x).

この際、試験後の試験材の割れ発生の有無を観察し、1個でも割れが発生したものを割れ有り、3個とも割れが発生しなかったものを割れ無しと評価した。   At this time, the presence or absence of occurrence of cracks in the test material after the test was observed, and the case where even one crack occurred was evaluated as cracked, and the case where no crack occurred in all three was evaluated as not cracked.

表1、3から明らかな通り、発明例1〜24の鋳鋼は、本発明化学成分組成範囲内からなり、かつ、鋳鋼組織におけるマルテンサイトの体積分率が40%以上95%以下である。   As is apparent from Tables 1 and 3, the cast steels of Invention Examples 1 to 24 are within the chemical component composition range of the present invention, and the martensite volume fraction in the cast steel structure is 40% or more and 95% or less.

この結果、発明例1〜24の鋳鋼は、前記加工後の硬度や加工硬化能が高く、シャルピー衝撃値が70J/cm2 以上である。また、コーンクラッシャーなどの実機破砕機としての耐磨耗性部材としての耐磨耗性も良好である。 As a result, the cast steels of Invention Examples 1 to 24 have high hardness and work hardening ability after the processing, and have a Charpy impact value of 70 J / cm 2 or more. Moreover, the wear resistance as a wear-resistant member as an actual machine crusher such as a cone crusher is also good.

これに対して、表2、4から明らかな通り、比較例25〜37の鋳鋼は、本発明化学成分組成範囲から外れている。このため、好ましい製造条件で製造されながらも、鋳鋼組織条件が外れるか、鋳鋼組織条件を満足しても、前記加工後の硬度や加工硬化能、シャルピー衝撃値、耐磨耗性のいずれかが、発明例に比して著しく劣る。この結果、比較例は、コーンクラッシャーなどの実機破砕機での耐磨耗性部材として不適である。   On the other hand, as is clear from Tables 2 and 4, the cast steels of Comparative Examples 25 to 37 are out of the chemical composition range of the present invention. For this reason, any of the hardness, work hardenability, Charpy impact value, and wear resistance after the above processing can be achieved even if the cast steel structure condition is not satisfied or the cast steel structure condition is satisfied, even though it is manufactured under preferable manufacturing conditions. It is remarkably inferior to the inventive examples. As a result, the comparative example is not suitable as a wear-resistant member in an actual machine crusher such as a cone crusher.

比較例25はCが低過ぎるため、加工硬化量が低く、比摩耗量が大きい。
比較例26はCが高過ぎるため、初期靱性が低く、耐摩耗試験中に折損した。
比較例27はNが低過ぎるため、加工硬化量が低く、比摩耗量が大きい。
比較例28はNが高過ぎるため、鋳造時にブローホールが発生し、試験できなかった。
比較例29はMnが低過ぎるため、マルテンサイト量が過多となり、残留オーステナイトと量が少なくなっている。このため、初期靱性が低く、耐摩耗試験中に割れが発生した。
比較例30はMnが高過ぎるため、炭化物が生成している。このため、初期靱性が低く、耐摩耗試験中に割れが発生した。
比較例31はCrが低過ぎるため、加工硬化量が低く、比摩耗量が大きい。
比較例32はCrが高過ぎるため、初期靱性が低く、耐摩耗試験中に割れが発生した。
比較例33は、マルテンサイト指数が下限以下で低過ぎ、初期靱性は高いが、加工硬化により延性が不足し、耐摩耗試験中に割れが発生した。
比較例34は、マルテンサイト指数が上限を越えて高過ぎ、低炭素マルテンサイト中の残留オーステナイトが不足している(観察されない)。このため、加工硬化量が低く、比摩耗量が大きい。
比較例35は、Siが高過ぎるため、初期靱性が低く、耐摩耗試験中に割れが発生した。
比較例36は、Niが高過ぎるため、加工硬化量が低く、比摩耗量が大きい。
比較例37は、Ti、Nb、Zrの合計量が高過ぎるため、初期靱性が低く、耐摩耗試験中に割れが発生した。
In Comparative Example 25, since C is too low, the work hardening amount is low and the specific wear amount is large.
In Comparative Example 26, C was too high, so the initial toughness was low, and it broke during the wear resistance test.
In Comparative Example 27, since N is too low, the work hardening amount is low and the specific wear amount is large.
In Comparative Example 28, since N was too high, blowholes were generated during casting and could not be tested.
In Comparative Example 29, since Mn is too low, the amount of martensite is excessive, and the amount of retained austenite is small. For this reason, the initial toughness was low, and cracking occurred during the wear resistance test.
Since the comparative example 30 has too high Mn, the carbide | carbonized_material has produced | generated. For this reason, the initial toughness was low, and cracking occurred during the wear resistance test.
Since Comparative Example 31 has too low Cr, the work hardening amount is low and the specific wear amount is large.
In Comparative Example 32, Cr was too high, so the initial toughness was low, and cracking occurred during the wear resistance test.
In Comparative Example 33, the martensite index was too low below the lower limit and the initial toughness was high, but the ductility was insufficient due to work hardening, and cracking occurred during the wear resistance test.
In Comparative Example 34, the martensite index exceeds the upper limit and is too high, and the residual austenite in the low carbon martensite is insufficient (not observed). For this reason, the work hardening amount is low and the specific wear amount is large.
In Comparative Example 35, since Si was too high, the initial toughness was low, and cracking occurred during the wear resistance test.
In Comparative Example 36, since Ni is too high, the work hardening amount is low and the specific wear amount is large.
In Comparative Example 37, the total amount of Ti, Nb, and Zr was too high, so the initial toughness was low, and cracking occurred during the wear resistance test.

以上の結果から、本発明高Mn鋳鋼の化学成分組成と組織規定の持つ意義が裏付けられる。   From the above results, the significance of the chemical composition of the high-Mn cast steel of the present invention and the structure definition is supported.

次ぎに、表1の発明例1の高Mn鋳鋼を、表5に示す、種々の条件で均質化処理、焼入れ処理を行い、室温まで冷却した。そして、これらの高Mn鋳鋼の硬度、加工硬化能、靱性、耐摩耗性などを、前記実施例と同様に各々評価した。これらの結果を表5に示す。   Next, the high Mn cast steel of Invention Example 1 in Table 1 was subjected to homogenization treatment and quenching treatment under various conditions shown in Table 5 and cooled to room temperature. The hardness, work hardening ability, toughness, wear resistance, etc. of these high Mn cast steels were evaluated in the same manner as in the above examples. These results are shown in Table 5.

表5から明らかな通り、発明例38〜45の鋳鋼は、好ましい製造条件範囲内で製造されており、鋳鋼組織におけるマルテンサイトの体積分率が40%以上95%以下である。この結果、前記加工後の硬度や加工硬化能が高く、シャルピー衝撃値が70J/cm2 以上である。また、コーンクラッシャーなどの実機破砕機としての耐磨耗性部材としての耐磨耗性も良好である。 As is apparent from Table 5, the cast steels of Invention Examples 38 to 45 are manufactured within a preferable range of manufacturing conditions, and the martensite volume fraction in the cast steel structure is 40% or more and 95% or less. As a result, the hardness and work hardening ability after the processing are high, and the Charpy impact value is 70 J / cm 2 or more. Moreover, the wear resistance as a wear-resistant member as an actual machine crusher such as a cone crusher is also good.

これに対して、比較例46〜48の鋳鋼は、好ましい製造条件範囲から外れている。このため、本発明化学成分組成範囲であるにもかかわらず、前記加工後の硬度や加工硬化能、シャルピー衝撃値、耐磨耗性のいずれかが、発明例に比して著しく劣る。この結果、比較例46〜48は、コーンクラッシャーなどの実機破砕機での耐磨耗性部材として不適である。   On the other hand, the cast steels of Comparative Examples 46 to 48 are out of the preferable production condition range. For this reason, in spite of being within the chemical component composition range of the present invention, any one of the hardness, work hardening ability, Charpy impact value, and abrasion resistance after processing is significantly inferior to the inventive examples. As a result, Comparative Examples 46 to 48 are unsuitable as wear-resistant members in actual machine crushers such as cone crushers.

比較例46は、均質化処理における加熱温度が低過ぎる。このため、耐摩耗試験中に割れが発生した。
比較例47は、均質化処理における加熱温度が高過ぎる。このため、均質化が進み過ぎ、残留オーステナイトが不足している。このため、加工硬化量が低く、比摩耗量が大きい。
比較例48は、焼入れ処理における平均冷却速度が小さ過ぎる。このため、初期靱性が低く、耐摩耗試験中に折損した。
In Comparative Example 46, the heating temperature in the homogenization treatment is too low. For this reason, cracks occurred during the wear resistance test.
In Comparative Example 47, the heating temperature in the homogenization treatment is too high. For this reason, homogenization progresses too much and the residual austenite is insufficient. For this reason, the work hardening amount is low and the specific wear amount is large.
In Comparative Example 48, the average cooling rate in the quenching process is too small. For this reason, the initial toughness was low and it broke during the wear resistance test.

以上の結果から、本発明高Mn鋳鋼の製造方法の規定する製造条件の意義が裏付けられる。   From the above results, the significance of the production conditions defined by the production method of the high Mn cast steel of the present invention is supported.

以上説明したように、本発明によれば、耐摩耗性及び靱性に優れた耐摩耗性高Mn鋳鋼およびその製造方法を提供することができる。このため、岩石を破砕するコーンクラッシャ、ジョークラッシャなどの破砕機の耐摩耗部材に用いられて好適である。   As described above, according to the present invention, it is possible to provide a wear-resistant high-Mn cast steel excellent in wear resistance and toughness and a method for producing the same. For this reason, it is suitable for being used as a wear-resistant member of a crusher such as a cone crusher or a jaw crusher for crushing rocks.

本発明耐摩耗性鋳鋼の組織を示す顕微鏡写真(図面代用写真)である。It is a microscope picture (drawing substitute photograph) which shows the structure | tissue of this invention abrasion-resistant cast steel. 実施例に用いた耐磨耗性試験機を示す断面図である。It is sectional drawing which shows the abrasion resistance tester used for the Example.

Claims (3)

  1. 質量%で、C:0.1〜0.3%、Si:0.3〜1.0%、Mn:5〜15%、Cr:5〜15%、N:0.05〜0.2%、を含有するとともに、これら各元素の含有量が、95≧460−〔480×(%C)−21×(%Si)−8×(%Mn)−14(%Cr)−480×(%N)〕>50の関係を満たし、残部がFe及び不可避的不純物からなり、鋳鋼組織におけるマルテンサイトの体積分率が40%以上95%以下であり、残部が残留オーステナイトからなることを特徴とする耐摩耗性鋳鋼。   In mass%, C: 0.1 to 0.3%, Si: 0.3 to 1.0%, Mn: 5 to 15%, Cr: 5 to 15%, N: 0.05 to 0.2% , And the content of each of these elements is 95 ≧ 460− [480 × (% C) −21 × (% Si) −8 × (% Mn) −14 (% Cr) −480 × (% N)]> 50, the balance is made of Fe and inevitable impurities, the martensite volume fraction in the cast steel structure is 40% to 95%, and the balance is made of residual austenite. Wear resistant cast steel.
  2. 前記鋳鋼が、更に、Ni:0.3〜5.0%、Mo:0.3〜2.0%の1種または2種、および/またはTi、Nb、Zrの内の1種または2種以上を合計で0.1〜1.5%含む請求項1に記載の耐摩耗性鋳鋼。   The cast steel further includes one or two of Ni: 0.3 to 5.0% and Mo: 0.3 to 2.0%, and / or one or two of Ti, Nb, and Zr. The wear-resistant cast steel according to claim 1, comprising 0.1 to 1.5% in total.
  3. 請求項1または2の耐摩耗性鋳鋼を製造する方法であって、請求項1または2の化学成分組成を有する鋳鋼を鋳造した後に、この鋳鋼を再加熱して900〜1200℃の温度範囲で1〜50時間保持し、その後500℃以下の温度まで1℃/s以上の平均冷却速度で冷却する焼入れ処理し、鋳鋼組織におけるマルテンサイトの体積分率を40%以上95%以下、残部が残留オーステナイトとすることを特徴とする耐摩耗性鋳鋼の製造方法。   A method for producing the wear-resistant cast steel according to claim 1 or 2, wherein after casting the cast steel having the chemical composition of claim 1 or 2, the cast steel is reheated in a temperature range of 900 to 1200 ° C. Hold for 1 to 50 hours, and then quench by cooling at an average cooling rate of 1 ° C./s or higher to a temperature of 500 ° C. or less, the martensite volume fraction in the cast steel structure is 40% or more and 95% or less, and the remainder remains A method for producing a wear-resistant cast steel, characterized in that it is austenite.
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Publication number Priority date Publication date Assignee Title
JP2014181360A (en) * 2013-03-18 2014-09-29 Kurimoto Ltd High-temperature wear-resistant material
JPWO2013108417A1 (en) * 2012-01-16 2015-05-11 新東工業株式会社 Crushing device and metal roll for grit production
CN104884655A (en) * 2012-12-27 2015-09-02 Posco公司 High-manganese wear resistant steel having excellent weldability and method for manufacturing same
CN105039655A (en) * 2015-07-31 2015-11-11 共享铸钢有限公司 Thermal treatment method suitable for cone crusher casting
WO2020054553A1 (en) * 2018-09-12 2020-03-19 Jfeスチール株式会社 Steel material and production method therefor

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Publication number Priority date Publication date Assignee Title
JPWO2013108417A1 (en) * 2012-01-16 2015-05-11 新東工業株式会社 Crushing device and metal roll for grit production
CN104884655A (en) * 2012-12-27 2015-09-02 Posco公司 High-manganese wear resistant steel having excellent weldability and method for manufacturing same
EP2940171A4 (en) * 2012-12-27 2015-12-30 Posco High-manganese wear resistant steel having excellent weldability and method for manufacturing same
JP2016508184A (en) * 2012-12-27 2016-03-17 ポスコ High manganese wear resistant steel with excellent weldability and method for producing the same
US9945014B2 (en) 2012-12-27 2018-04-17 Posco High-manganese wear resistant steel having excellent weldability and method for manufacturing same
JP2014181360A (en) * 2013-03-18 2014-09-29 Kurimoto Ltd High-temperature wear-resistant material
CN105039655A (en) * 2015-07-31 2015-11-11 共享铸钢有限公司 Thermal treatment method suitable for cone crusher casting
CN105039655B (en) * 2015-07-31 2017-06-16 共享铸钢有限公司 A kind of heat treatment method suitable for gyratory crusher casting
WO2020054553A1 (en) * 2018-09-12 2020-03-19 Jfeスチール株式会社 Steel material and production method therefor

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