JP3589797B2

JP3589797B2 - Wear resistant high Mn cast steel

Info

Publication number: JP3589797B2
Application number: JP18124196A
Authority: JP
Inventors: 昌吾村上; 博幸内田; 耕児皆川; 健増本; 寿直中井
Original assignee: Kobe Steel Ltd
Current assignee: Kobe Steel Ltd
Priority date: 1996-06-21
Filing date: 1996-06-21
Publication date: 2004-11-17
Anticipated expiration: 2016-06-21
Also published as: JPH108210A

Description

【０００１】
【発明の属する技術分野】
本発明は、重衝撃を受ける耐摩耗部材、特に岩石を破砕するコーンクラッシャやジョークラッシャ等の破砕機のライナー材に用いられ、優れた耐摩耗性を有する高Ｍｎ鋳鋼に関するものである。
【０００２】
【従来の技術】
高Ｍｎ鋳鋼は、本来良好な加工硬化特性と靭性を合わせ持った材料であり、その特性を利用してこれまでにも重衝撃を受ける耐摩耗部材、例えば岩石を破砕するコーンクラッシャやジョークラッシャ等の破砕機のライナー材として多用されてきた。ところが近年、破砕機等に対し、特に産業廃棄物や岩石用の破砕機等に対して処理能力の向上が求められるようになり、破砕機等の大型化，高破砕比化が進められている。これに伴い、破砕機等に使用される耐摩耗部材の摩耗状況は今後一層過酷になる傾向にあり、より耐摩耗性に優れた高Ｍｎ鋼の開発が急がれている。
【０００３】
これまでにも、高Ｍｎ鋳鋼の耐摩耗性を改善しようとする試みが種々なされてきた。例えば、特公昭５７−１７９３７号，特公昭６３−８１８１号，特公昭１−１４３０３号，特開昭６２−１３９８５５号，特開平１−１４２０５８号公報には、ＪＩＳ規格の高Ｍｎ鋼組成よりＣ濃度を高めて耐摩耗性を向上させた合金例が記載されている。
【０００４】
【発明が解決しようとする課題】
しかし、上記の各公報に記載の合金材料で肉厚の大きい破砕機のライナー材を実際に製作し使用した場合、延性の低下が予想以上に著しいため、耐摩耗性を高めるはずである「Ｃ濃度の増加」という手段を直ちに採用できず、現在に至っている。本発明者等も、Ｃ濃度を高くすることによって、耐摩耗性を顕著に向上できる点に着目する一方、上記の延性低下の現象にも着目し、その延性低下の原因を見極めれば、「Ｃ濃度を高める」手段が真に耐摩耗性の向上にとって有効な手段となりうるはずとの考えに立ち、そのような延性低下の原因の究明を目指して実験を開始し、以下の知見を得ることができた。
【０００５】
通常、高Ｍｎ鋳鋼はスクラップを配合して溶製されるため、また溶解原料であるフェロマンガンに数１／１０％のＰが含まれていることもあって、現在使用されている高Ｍｎ鋳鋼はＰを０．０２〜０．０７％程度含んでおり、このＰが、溶製時にデンドライトアーム間、特に結晶粒界に偏析し、その後の水靭処理時に溶体化温度域で図１に示すようなＦｅ−Ｃ−Ｐの共晶化合物を形成し、これが延性を低下させる原因であることが判明した。次に、本発明者等は、そのようなＦｅ−Ｃ−Ｐの共晶化合物の生成を避けるために水靭処理時の溶体化温度をその共晶化合物の生成温度以下に設定して実験したところ、今度は炭化物（Ｍ_３Ｃ）を固溶しきれずに、この炭化物の存在により同じく延性が低下することも判明した。そこで、本発明者等は、Ｆｅ−Ｃ−Ｐの共晶化合物の生成因子の一つであるＰ濃度が大きく影響していることを予想し、Ｐ濃度そのものやＰ濃度とＣ濃度との相関関係が延性に及ぼす影響を見極めることに解決の糸口があるはずとの考えに到達した。
【０００６】
本発明は、こうした状況の下になされたものであって、その目的は、高Ｍｎ鋳鋼の耐摩耗性を向上させ、より長寿命の耐摩耗部材を提供することにある。
【０００７】
【課題を解決するための手段】
上記目的を達成し得た本発明のうち、請求項１記載の発明は、重量％でＣ：１．３〜１．７％，Ｓｉ：０．３〜１．０％，Ｍｎ１０〜３５％，Ｃｒ：０〜５％，Ｍｏ：０〜２％，不純物元素であるＰ濃度が０．０１％以下で且つ〔％Ｃ〕・〔％Ｐ〕≦０．０１５とし、残部がＦｅおよび不可避不純物であることを特徴とする耐摩耗高Ｍｎ鋳鋼である。また、請求項２記載の発明は、上記構成元素に加えて、Ｔｉ，Ａｌのいずれか一方又は両方を０．０１〜０．６％含有する耐摩耗高Ｍｎ鋳鋼であり、また、請求項３記載の発明は、その上さらにＶ，Ｎｂ，Ｂ，Ｔａ，Ｚｒのうち１種又は２種以上を合計で０．０１〜３．０％含有する耐摩耗高Ｍｎ鋳鋼である。
【０００８】
本発明は、以下に詳細に述べるように全く新たな知見に基づいてなされたものである。即ち、従来、Ｐは不純物元素であり、少ない方が好ましいとはされているものの、特公平２−１５６２３号公報や鉄鋼便覧（１９６２）Ｐ１４５６等に記載されているように、高Ｍｎ鋳鋼においてはＰ濃度が０．０７％を超えなければ延性は確保できるとされていた。このため、製造上のコストを上昇させてまでＰ濃度を大きく低減させようとする試みはほとんどなされていない。特に本発明のように、Ｐ濃度を０．０１％より低い範囲に抑えて延性，耐摩耗性との関係で一定の技術上の効果を発揮させようとする試みについては、全く検討されてこなかった。
【０００９】
これまでにも、機械的性質に及ぼすＰ濃度の影響については、２，３の研究報告例が存在する。例えば、ＴｒａｎｓＩｎｔＣｏｎｆＳｔｒｕｃｔＭｅｃｈＲｅａｃｔＴｅｃｈｎｏｌ，１１ｔｈ，Ｇ２（１９９１）Ｐ９３〜９８，ＩｚｖＶｙｓｓｈＵｃｈｅｂｎＺａｖｅｄＣｈｅｒｎＭｅｔａｌｌ，３（１９８９）Ｐ１０９〜１１３，ＬｉｔｅｊｎｏｅＰｒｏｉｚｖｏｄ，１１（１９８８）Ｐ８〜９に記載がある。しかし、これらの記載例でも、Ｐ濃度が０．０２％以上の範囲についてのみ言及されているにすぎない。そこで、本発明者等は、Ｐ濃度０．０２％以下の範囲も含めて延性に及ぼすＰ濃度の影響を明らかにすべく、さらに実験研究を進めてきた。その結果、Ｐ濃度を０．０１％以下にすると共に、その条件を満たしつつさらにＣ濃度に対するＰ濃度（相対的濃度）を一定範囲に収まるようにすることによって、延性が飛躍的に向上し、耐摩耗性に優れた高Ｍｎ鋳鋼が実現できることを見い出し、本発明を完成したものである。
【００１０】
即ち、不純物であるＰの濃度を０．０１％以下でかつ〔％Ｃ〕・〔％Ｐ〕≦０．０１５とすることによって、肉厚が１００ｍｍを超えるライナー材に対して、Ｃ濃度が１．３％以上であっても高い延性を確保でき、Ｃ濃度を現用高Ｍｎ鋳鋼の１．０〜１．３％から最大１．７％まで増加させることが可能となり、耐摩耗性を飛躍的に向上させることに成功したものである。そこで、まず、本発明の高Ｍｎ鋳鋼の成分範囲限定理由を説明する。
【００１１】
（イ）Ｃ：１．３〜１．７％
Ｃ濃度が１．３％未満では、従来の高Ｍｎ鋼材と同等の耐摩耗性しか得られず、一方Ｃ濃度が１．７％を超えると、Ｐ濃度を０．０１％に抑えても延性，靭性が低下し、耐摩耗性部材の製造時又は使用時に割れを生じる。従って、Ｃ濃度は１．３〜１．７％の範囲に限定した。
【００１２】
（ロ）Ｓｉ：０．３％〜１．０％
溶解時の溶湯の脱酸及び流動性確保のために、Ｓｉを０．３％以上添加する必要があるが、１％を超えると、炭化物の結晶粒界への析出が促進され、靭性が低下する。
【００１３】
（ハ）Ｍｎ：１０〜３５％
Ｍｎはオーステナイト組織を得るために必要な元素であり、またＣの固溶限を増大させて水靭処理の冷却過程での炭化物析出を抑制して延性向上に寄与する。そのためにはＭｎを１０％以上添加する必要があるが、Ｍｎが３５％を超えると、鋳放し状態での炭化物析出量が多くなり、鋳造時の割れ発生の原因となる。
【００１４】
（ニ）Ｃｒ：０〜５％
Ｃｒは加工硬化特性を向上させる有効な元素であるが、５％を超えると、鋳造時及び水靭処理の冷却過程での炭化物析出が顕著となり、延性が低下する。よって、０〜５％の範囲で必要に応じて添加する。
【００１５】
（ホ）Ｍｏ：０〜２％
Ｍｏは水靭処理冷却過程の炭化物析出を抑制し延性を向上させる効果を有するが、２％を超えて添加すると、その効果が失われる。
【００１６】
（ヘ）不純物元素であるＰ濃度が０．０１％以下で且つ〔％Ｃ〕・〔％Ｐ〕≦０．０１５
不純物であるＰの濃度を０．０１％以下でかつ〔％Ｃ〕・〔％Ｐ〕≦０．０１５とすることによって、肉厚が１００ｍｍを超えるライナー材に対して、Ｃ濃度が１．３％以上であっても高い延性を確保でき、Ｃ濃度を現用高Ｍｎ鋳鋼の１．０〜１．３％から最大１．７％まで増加させることが可能となり、耐摩耗性を飛躍的に向上させることができる。一方、Ｐ濃度が０．０１％を超えるか、〔％Ｃ〕・〔％Ｐ〕が０．１５を超える条件では、Ｆｅ−Ｃ−Ｐの共晶化合物の生成が促進され、延性が低下する。
【００１７】
本発明の高Ｍｎ鋳鋼は、Ｃ，Ｓｉ，Ｍｎ，Ｃｒ，Ｍｏを基本成分とし、不純物元素であるＰ濃度が０．０１％以下で且つ〔％Ｃ〕・〔％Ｐ〕≦０．０１５とし、残部がＦｅおよび不可避不純物よりなるものであるが、必要によってＴｉ，Ａｌ，Ｖ，Ｎｂ，Ｂ，Ｔａ，Ｚｒの元素を所定量含有させても良い。これらの元素を含有させるときの成分範囲限定理由は下記の通りである。
【００１８】
Ｔｉ，Ａｌ：いずれか一方又は両方で０．０１〜０．６％
Ｔｉ及びＡｌの添加は、酸化物又は窒化物を溶湯中に形成し、結晶粒を微細化するのに有効である。Ｔｉ，Ａｌのいずれか一方又は両方の添加量が０．０１以上で効果があり、０．６％を超えると、粗大な介在物を生成するため、延性，靭性が低下する。また、大気溶解において、Ａｌは脱酸材として添加する。また、Ｍｏと同様にＴｉの添加は、水靭処理冷却過程の炭化物析出を抑制する効果を有する。
【００１９】
Ｖ，Ｎｂ，Ｂ，Ｔａ，Ｚｒ：これらのうち１種又は２種以上の合計で０．０１〜３．０％
Ｖ，Ｎｂ，Ｂ，Ｔａ，Ｚｒは炭化物析出により、加工硬化特性の向上及び結晶粒の微細化に寄与するが、０．０１％以上の添加量で効果があり、添加量が３．０％を超えると、延性，靭性が低下する。
【００２０】
ところで、本発明に係る高Ｍｎ鋳鋼を得るためには、現在使用されている高Ｍｎ鋳鋼中のＰ濃度（０．０２〜０．０７％程度）を低下させる、即ち、脱Ｐする必要があるが、その具体的方法としては、主に以下（１）〜（３）の３つの方法を挙げることができる。
（１）精錬時にＢａ０系及びＮａ_４Ｓｉ０_４系フラックスを使用して酸化脱Ｐする。
（２）精錬時にＣａＣ_２−ＣａＦ_２系フラックスを使用して還元脱Ｐする。
（３）溶解原料としてフェロマンガンを使用せず、Ｍｎを含有しない溶鋼に金属Ｍｎを添加する。
特にＰ濃度を０．０１％以下にするには、フェロマンガンの使用をなるべく減らすことが不可欠である。
【００２１】
【実施例】
表１に示す化学組成の高Ｍｎ鋳鋼を高周波誘導加熱溶解炉を用いて溶製した。
【００２２】
【表１】

【００２３】
図２に示す鋳塊形状の砂型で、実際のライナー材を想定して鋳塊肉厚を約１００ｍｍとした。鋳込温度は、各組成における液相線温度より１００±５°Ｃ高い温度とした。溶製した鋳塊は、１１００°Ｃ×６ｈの溶体化処理後水冷する水靭処理を施した。水靭処理後、引張試験によって延性評価を行うと共に、圧縮試験によって加工硬化の特性評価を行った。いずれの場合も試験片は、鋳塊の肉厚（約１００ｍｍ）に対して中央部から試験片を採取し、以下の各試験条件で行った（図２参照）。
（１）引張試験：ＪＩＳ４号Ａ型の試験片を１０^−３／ｓのひずみ速度で行い、破断時の伸びから延性を評価した。
（２）圧縮試験：８φ×１２ｈｍｍの試験片を１０^−３／ｓのひずみ速度で行い、ひずみ５０％時の変形抵抗から加工硬化量を評価した。
【００２４】
なお、高Ｍｎ鋼は、加工硬化をすることによって優れた耐摩耗性を示す材質であるため、また、図３に示すように、加工硬化量と実機ライナーの摩耗寿命との間には良い相関が得られることがわかっているので、加工硬化の程度を調べることで、耐摩耗性，摩耗寿命といった特性の良否を知ることができるのである。試験結果を表２に示し、さらにＰ濃度と伸び（延性）との関係を図４に示す。なお、右肩に＊印を添えた数字のＮｏ．が本発明の要件を満足する実施例であり、評価は、伸び＞２０％で加工硬化量＞３５０ｋｇｆ／ｍｍ^２のものを合格（○）とした。
【００２５】
【表２】

【００２６】
表１，表２によれば、Ｐ濃度が低くなるほど、伸び（延性）及び加工硬化量（耐摩耗性）が向上する傾向があるが、特にＰ濃度が０．０１％以下になると、伸びが顕著に向上していることが分かる（実施例Ｎｏ．２^＊，３^＊，４^＊，６^＊，７^＊，８^＊，９^＊，１３^＊，１４^＊，１５^＊，１７^＊，１８^＊）。Ｃ濃度が高い場合には、特にＰ濃度を下げる必要があり（比較例Ｎｏ．１９）、逆にＣ濃度が低い場合には、Ｐ濃度が高くても延性は良いが、加工硬化量が小さく摩耗寿命に問題がある（比較例Ｎｏ．１）。また、伸びが約１０％以下になると、圧縮試験において高ひずみで割れが発生し、加工硬化量が顕著に低下する（比較例Ｎｏ．１０，１１，１２，１６，１９，２０）。上記結果から、Ｐ濃度を０．０１％以下で且つ〔％Ｃ〕・〔％Ｐ〕≦０．０１５とすることによって、鋳塊肉厚が１００ｍｍ以上でも必要な延性を確保しつつ、加工硬化量を向上させ、耐摩耗性を画期的に向上させることが可能となることが理解できる。
【００２７】
また、延性の向上にはＴｉ及びＭｏの添加が有効であり（実施例Ｎｏ．７^＊，１３^＊，１４^＊）、加工硬化量の向上にはＴｉ及び炭化物形成元素（Ｖ，Ｎｂ，Ｔａ，Ｂ）の添加が有効である（実施例Ｎｏ．７^＊，１５^＊）。この加工硬化量の向上は、主に結晶粒の微細化効果によるものである。但し、炭化物形成元素が３％を超えると、多量の炭化物の析出によって延性低下を招く（比較例Ｎｏ．１６）。
【００２８】
【発明の効果】
以上説明したように、本発明のうち請求項１記載の発明は、重量％でＣ：１．３〜１．７％，Ｓｉ：０．３〜１．０％，Ｍｎ：１０〜３５％，Ｃｒ：０〜５％，Ｍｏ：０〜２％，不純物元素であるＰ濃度が０．０１％以下で且つ〔％Ｃ〕・〔％Ｐ〕≦０．０１５とし、残部がＦｅおよび不可避不純物であることを特徴とする耐摩耗高Ｍｎ鋳鋼である。特に、Ｐ濃度を０．０１％以下で且つ〔％Ｃ〕・〔％Ｐ〕≦０．０１５とすることによって、延性が向上し、肉厚が１００ｍｍ前後、あるいはそれ以上の部材に対してもＣ濃度を１．３％以上にして加工硬化特性を向上させることができ、高Ｍｎ鋼製耐摩耗ライナー材の摩耗寿命を画期的に向上させることが可能となった。
【００２９】
また、請求項２記載の発明は、請求項１記載の発明の構成に、Ｔｉ，Ａｌのいずれか一方又は両方を０．０１〜０．６％加えたものであり、請求項１記載の発明の効果に加えて、さらに延性の面で優れた高Ｍｎ鋳鋼を提供することができる。さらに、請求項３記載の発明は、請求項２記載の発明の構成に、Ｖ，Ｎｂ，Ｂ，Ｔａ，Ｚｒのうち１種又は２種以上を合計で０．０１〜３．０％加えたものであり、請求項２記載の発明の効果に加えて、さらに加工硬化特性（耐摩耗性）の面で優れた高Ｍｎ鋳鋼を提供することができる。
【図面の簡単な説明】
【図１】水靭処理後の現用高Ｍｎ鋼の結晶粒界に形成されるＦｅ−Ｃ−Ｐの共晶化合物を示す顕微鏡写真である。
【図２】実施例に供した鋳塊の形状，肉厚と引張試験片及び圧縮試験片の採取位置との関係を示す図である。
【図３】加工硬化量と実機コーンクラッシャライナー材寿命との関係を示す図である。
【図４】Ｐ濃度と伸び（延性）との関係を示す図である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a high-Mn cast steel having excellent wear resistance, which is used as a liner material for a crusher such as a cone crusher or a jaw crusher for crushing rock, which is used for crushing rocks.
[0002]
[Prior art]
High-Mn cast steel is a material that originally has good work hardening characteristics and toughness. By utilizing these characteristics, wear-resistant members that have been subjected to heavy impacts so far, such as cone crushers and jaw crushers that crush rocks, etc. Has been widely used as a liner material for crushers. However, in recent years, it has been required to improve the processing capacity of crushers and the like, especially for industrial waste and rocks, and the size of crushers and the crushing ratio have been increased. . Accordingly, the wear of wear-resistant members used in crushers and the like tends to become more severe in the future, and the development of high Mn steels having more excellent wear resistance is urgently required.
[0003]
Until now, various attempts have been made to improve the wear resistance of high Mn cast steel. For example, JP-B-57-17937, JP-B-63-8181, JP-B-1-14303, JP-A-62-139855, and JP-A-1-142058 disclose a Cn steel having a high Mn steel composition based on JIS. Examples of alloys in which the concentration is increased to improve wear resistance are described.
[0004]
[Problems to be solved by the invention]
However, when a liner material for a crusher having a large thickness is actually manufactured and used with the alloy material described in each of the above-mentioned publications, the wear resistance should be increased because the decrease in ductility is more remarkable than expected. The means of "increase in concentration" could not be adopted immediately, and it is up to the present. The present inventors have also focused on the fact that the wear resistance can be significantly improved by increasing the C concentration. On the other hand, focusing on the phenomenon of the ductility decrease described above and examining the cause of the ductility decrease, “C Based on the belief that the `` enhancing concentration '' means could be truly an effective means for improving abrasion resistance, we started experiments aiming to find the cause of such a decrease in ductility and obtained the following findings. did it.
[0005]
Normally, high Mn cast steel is melted by mixing scraps, and since ferromanganese, which is a melting raw material, contains several 1/10% of P, currently used high Mn cast steel is used. Contains about 0.02 to 0.07% of P, and this P segregates between the dendrite arms during melting, particularly at the crystal grain boundaries, and is shown in FIG. It was found that such a eutectic compound of Fe-CP was formed, and this was the cause of lowering ductility. Next, the present inventors conducted experiments by setting the solution temperature during the toughening treatment to be equal to or lower than the formation temperature of the eutectic compound in order to avoid the formation of such a eutectic compound of Fe-CP. However, this time, it was also found that the carbide (M ₃ C) could not be completely dissolved, and the ductility was similarly reduced by the presence of the carbide. Therefore, the present inventors anticipate that the P concentration, which is one of the factors for forming the eutectic compound of Fe-CP, has a large influence, and have considered the P concentration itself and the correlation between the P concentration and the C concentration. We arrived at the idea that there should be a clue to finding out the effects of relationships on ductility.
[0006]
The present invention has been made under such circumstances, and an object of the present invention is to improve the wear resistance of high Mn cast steel and provide a wear-resistant member having a longer life.
[0007]
[Means for Solving the Problems]
Of the present invention that has achieved the above object, the invention according to claim 1 is characterized in that C: 1.3 to 1.7%, Si: 0.3 to 1.0%, Mn 10 to 35%, Cr: 0 to 5% , Mo: 0 to 2% , P concentration as an impurity element is 0.01% or less, and [% C] · [% P] ≦ 0.015, and the balance is Fe and unavoidable impurities. It is a wear-resistant high Mn cast steel characterized by the following. The invention according to claim 2 is a wear-resistant high Mn cast steel containing 0.01 to 0.6% of one or both of Ti and Al in addition to the above constituent elements. The described invention is a wear-resistant high Mn cast steel further containing 0.01 to 3.0% in total of one or more of V, Nb, B, Ta, and Zr.
[0008]
The present invention has been made based on completely new findings as described in detail below. That is, conventionally, P is an impurity element, and although it is said that a smaller amount is preferable, as described in Japanese Patent Publication No. 15623/1992 and Handbook of Iron and Steel (1962) P1456, in high Mn cast steel, It was considered that ductility could be ensured unless the P concentration exceeded 0.07%. For this reason, almost no attempt has been made to significantly reduce the P concentration until the manufacturing cost is increased. In particular, no attempt has been made at all to attempt to achieve a certain technical effect in relation to ductility and abrasion resistance by suppressing the P concentration to a range lower than 0.01% as in the present invention. Was.
[0009]
There have been a few research reports on the effect of P concentration on mechanical properties. For example, Trans Int Conf Struct Mech React Technol, 11th, G2 (1991) P93-98, Izv Vishsh Uchbn Saved Chen Metall, 3 (1989) P109-113, Litejne Proiz, 88; However, even in these descriptions, only the range where the P concentration is 0.02% or more is mentioned. Thus, the present inventors have further conducted experimental studies to clarify the effect of P concentration on ductility, including the range of P concentration of 0.02% or less. As a result, the P concentration is set to 0.01% or less, and the P concentration (relative concentration) with respect to the C concentration falls within a certain range while satisfying the condition, whereby the ductility is dramatically improved. It has been found that a high Mn cast steel having excellent wear resistance can be realized, and the present invention has been completed.
[0010]
That is, by setting the concentration of P as an impurity to 0.01% or less and [% C] · [% P] ≦ 0.015, the C concentration becomes 1 with respect to the liner material having a thickness of more than 100 mm. High ductility can be ensured even at 0.3% or more, and the C concentration can be increased from 1.0 to 1.3% of the currently used high Mn cast steel to a maximum of 1.7%, and the wear resistance is dramatically improved. It has been successfully improved. Therefore, first, the reasons for limiting the component range of the high Mn cast steel of the present invention will be described.
[0011]
(A) C: 1.3 to 1.7%
If the C concentration is less than 1.3%, only the same abrasion resistance as the conventional high Mn steel material can be obtained, while if the C concentration exceeds 1.7%, the ductility is suppressed even if the P concentration is suppressed to 0.01%. , The toughness is reduced, and cracks occur during the manufacture or use of the wear-resistant member. Therefore, the C concentration was limited to the range of 1.3 to 1.7%.
[0012]
(B) Si: 0.3% to 1.0%
It is necessary to add 0.3% or more of Si in order to deoxidize the molten metal at the time of melting and to ensure fluidity. However, if it exceeds 1%, precipitation of carbides at crystal grain boundaries is promoted, and toughness is reduced. I do.
[0013]
(C) Mn: 10 to 35%
Mn is an element necessary for obtaining an austenite structure, and also increases the solid solubility limit of C to suppress carbide precipitation in the cooling process of the water toughness treatment, thereby contributing to improvement in ductility. For this purpose, Mn must be added in an amount of 10% or more. However, if Mn exceeds 35%, the amount of carbide precipitation in an as-cast state increases, which causes cracking during casting.
[0014]
(D) Cr: 0 to 5%
Cr is an effective element for improving the work hardening characteristics. However, if it exceeds 5%, carbide precipitation during casting and during the cooling process of the water toughness treatment becomes remarkable, and the ductility decreases. Therefore, it is added as needed in the range of 0 to 5% .
[0015]
(E) Mo: 0 to 2%
Mo has the effect of suppressing the precipitation of carbides in the cooling process of the water toughness treatment and improving the ductility. However, if it exceeds 2%, the effect is lost.
[0016]
(F) The concentration of P as an impurity element is 0.01% or less and [% C] · [% P] ≦ 0.015
By setting the concentration of P, which is an impurity, to 0.01% or less and [% C] · [% P] ≦ 0.015, the C concentration is 1.3 for a liner material having a thickness exceeding 100 mm. % Or more, high ductility can be ensured, and the C concentration can be increased from 1.0 to 1.3% of the currently used high Mn cast steel to a maximum of 1.7%, and the wear resistance is dramatically improved. Can be done. On the other hand, when the P concentration exceeds 0.01% or [% C] · [% P] exceeds 0.15, the formation of the eutectic compound of Fe—CP is promoted, and the ductility is reduced. .
[0017]
The high Mn cast steel of the present invention contains C, Si, Mn, Cr, and Mo as basic components, and has a P concentration of an impurity element of 0.01% or less and [% C] · [% P] ≦ 0.015. The remainder is composed of Fe and unavoidable impurities. If necessary, a predetermined amount of elements of Ti, Al, V, Nb, B, Ta, and Zr may be contained. The reasons for limiting the component ranges when these elements are contained are as follows.
[0018]
Ti, Al: 0.01 to 0.6% in either or both
The addition of Ti and Al is effective for forming oxides or nitrides in the molten metal and refining crystal grains. When one or both of Ti and Al are added in an amount of 0.01 or more, there is an effect, and when it exceeds 0.6%, coarse inclusions are generated, so that ductility and toughness decrease. In addition, in dissolving in the air, Al is added as a deoxidizer. Further, similarly to Mo, the addition of Ti has an effect of suppressing carbide precipitation in the cooling process of the water toughness treatment.
[0019]
V, Nb, B, Ta, Zr: 0.01 to 3.0% in total of one or more of these.
V, Nb, B, Ta, and Zr contribute to the improvement of work hardening characteristics and the refinement of crystal grains due to precipitation of carbides, but are effective at an addition amount of 0.01% or more, and the addition amount is 3.0%. If it exceeds, ductility and toughness decrease.
[0020]
Incidentally, in order to obtain the high Mn cast steel according to the present invention, it is necessary to lower the P concentration (about 0.02 to 0.07%) in the currently used high Mn cast steel, that is, to remove P. However, the specific methods mainly include the following three methods (1) to (3).
(1) oxidative de P using Ba0 system and _Na 4 Si0 ₄ based flux during refining.
(2) reduction to de-P using the _CaC ₂ -CaF 2-based flux at the time of refining.
(3) Ferromanganese is not used as a raw material for melting, and metal Mn is added to molten steel containing no Mn.
In particular, in order to reduce the P concentration to 0.01% or less, it is essential to reduce the use of ferromanganese as much as possible.
[0021]
【Example】
High Mn cast steel having the chemical composition shown in Table 1 was melted using a high frequency induction heating melting furnace.
[0022]
[Table 1]

[0023]
In the ingot-shaped sand mold shown in FIG. 2, the ingot thickness was set to about 100 mm assuming an actual liner material. The casting temperature was 100 ± 5 ° C. higher than the liquidus temperature for each composition. The ingot thus melted was subjected to a solution toughness treatment at 1100 ° C. × 6 h, followed by a water toughness treatment of water cooling. After the water toughness treatment, ductility was evaluated by a tensile test, and work hardening characteristics were evaluated by a compression test. In each case, the test piece was collected from the center with respect to the thickness of the ingot (about 100 mm), and the test was performed under the following test conditions (see FIG. 2).
(1) Tensile test: JIS No. 4 type A test piece was performed at a strain rate of 10 ⁻³ / s, and ductility was evaluated from elongation at break.
(2) Compression test: A test piece of 8φ × 12 hmm was performed at a strain rate of 10 ⁻³ / s, and the amount of work hardening was evaluated from the deformation resistance at a strain of 50%.
[0024]
Since high-Mn steel is a material that exhibits excellent wear resistance due to work hardening, as shown in FIG. 3, there is a good correlation between the amount of work hardening and the wear life of the actual machine liner. Therefore, by examining the degree of work hardening, it is possible to know whether or not characteristics such as wear resistance and wear life are good. The test results are shown in Table 2, and the relationship between P concentration and elongation (ductility) is shown in FIG. In addition, the number of the number which attached * mark to the right shoulder. Is an example that satisfies the requirements of the present invention. In the evaluation, those having elongation> 20% and work hardening amount> 350 kgf / mm ² were judged as acceptable (○).
[0025]
[Table 2]

[0026]
According to Tables 1 and 2, as the P concentration decreases, the elongation (ductility) and the amount of work hardening (abrasion resistance) tend to improve, but particularly when the P concentration is 0.01% or less, the elongation increases. It can be seen that it is significantly improved (

Example Nos

^. 2 ^* , 3 ^* , 4 ^* , 6 ^* , 7 ^* , 8 ^* , 9 ^* , 13 ^* , 14 ^* , 15 ^* , 17 ^* , 18 ^* ). . When the C concentration is high, it is particularly necessary to lower the P concentration (Comparative Example No. 19). Conversely, when the C concentration is low, the ductility is good even when the P concentration is high, but the work hardening amount is small. There is a problem in wear life (Comparative Example No. 1). Further, when the elongation is about 10% or less, cracks occur with high strain in the compression test, and the amount of work hardening is remarkably reduced (Comparative Examples Nos. 10, 11, 12, 16, 19, and 20). From the above results, by setting the P concentration to be 0.01% or less and [% C] · [% P] ≦ 0.015, work hardening can be achieved while ensuring necessary ductility even when the ingot thickness is 100 mm or more. It can be understood that the amount can be improved and the wear resistance can be remarkably improved.
[0027]
Further, addition of Ti and Mo is effective for improving ductility (Examples No. 7 ^* , 13 ^* , 14 ^* ), and for improving the amount of work hardening, Ti and carbide forming elements (V, Nb, Ta, B) is effective (Examples No. 7 ^* , 15 ^* ). This improvement in the amount of work hardening is mainly due to the effect of refining crystal grains. However, when the carbide forming element exceeds 3%, a large amount of carbide precipitates to cause a decrease in ductility (Comparative Example No. 16).
[0028]
【The invention's effect】
As described above, the invention according to claim 1 of the present invention is as follows: C: 1.3 to 1.7%, Si: 0.3 to 1.0%, Mn: 10 to 35%, Cr: 0 to 5% , Mo: 0 to 2% , P concentration as an impurity element is 0.01% or less and [% C] · [% P] ≦ 0.015, and the balance is Fe and unavoidable impurities. It is a wear-resistant high Mn cast steel characterized by the following. In particular, by setting the P concentration to 0.01% or less and [% C] · [% P] ≦ 0.015, ductility is improved, and even for members having a thickness of about 100 mm or more. The work hardening characteristics can be improved by setting the C concentration to 1.3% or more, and the wear life of the wear-resistant liner material made of high Mn steel can be significantly improved.
[0029]
According to a second aspect of the invention, one or both of Ti and Al are added to the configuration of the first aspect of the invention in an amount of 0.01 to 0.6%. In addition to the effects described above, it is possible to provide a high Mn cast steel which is more excellent in ductility. Further, in the invention of claim 3, one or more of V, Nb, B, Ta, and Zr are added to the constitution of the invention of claim 2 in a total amount of 0.01 to 3.0%. Thus, in addition to the effects of the invention described in claim 2, a high Mn cast steel excellent in work hardening characteristics (wear resistance) can be provided.
[Brief description of the drawings]
FIG. 1 is a micrograph showing a Fe-CP eutectic compound formed at a crystal grain boundary of a working high Mn steel after a water toughening treatment.
FIG. 2 is a diagram showing the relationship between the shape and thickness of an ingot used in Examples and the positions at which tensile test pieces and compression test pieces are sampled.
FIG. 3 is a graph showing the relationship between the amount of work hardening and the life of the actual cone crusher liner material.
FIG. 4 is a diagram showing a relationship between P concentration and elongation (ductility).

Claims

C: 1.3 to 1.7% by weight, Si: 0.3 to 1.0%, Mn: 10 to 35%, Cr: 0 to 5% , Mo: 0 to 2% , and are impurity elements. A wear-resistant high Mn cast steel having a P concentration of 0.01% or less and [% C] · [% P] ≦ 0.015, with the balance being Fe and unavoidable impurities.

The wear-resistant high Mn cast steel according to claim 1, further comprising one or both of Ti and Al in an amount of 0.01 to 0.6%.

The wear-resistant high Mn cast steel according to claim 2, further comprising one or more of V, Nb, B, Ta, and Zr in a total amount of 0.01 to 3.0%.