JP2004011022A - Spherical graphite cast-iron excellent in weathering resistance and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spherical graphite cast-iron, excellent in weathering resistance, capable of suppressing a degradation of mechanical properties giving influences to mechanical workability such as cutting, and further capable of recycling a returned material as an ordinary cast-iron raw material, and to provide its production method. <P>SOLUTION: The production method of the spherical graphite cast-iron excellent in weathering resistance is composed of a first process (P1) of melting the spherical graphite cast-iron and adding Cu of 0.2-1.0%, Ni of 0.1-1.0% and Cr of 0.1-0.3% by mass% to this iron material, and a second process (P2) of adding Mo of 0.025-0.175% by mass% further. <P>COPYRIGHT: (C)2004,JPO

Description

【０００７】
表中、参考例１は日本工業規格（以下、「ＪＩＳ」ともいう。）ＦＣＤ４５０に相当する球状黒鉛鋳鉄である。また参考例２〜７は、参考例１の球状黒鉛鋳鉄を溶解し、これに各合金元素を所定量添加して溶製した、耐候性球状黒鉛鋳鉄である。添加量の単位は、用いる参考例１のＦＣＤ４５０相当球状黒鉛鋳鉄の質量を１００％とした質量％である（以下、単に「％」と表記する場合は、「質量％」の意である。）。また耐候性は、Ｚ２３７１（ＪＩＳ）による環境サイクル試験によって生じる腐食の量に基づき評価している。具体的には、ＦＣＤ４５０相当球状黒鉛鋳鉄（参考例１）における腐食量を１とした場合の相対数値で示している。
【０００８】
表に示されるように、Ｃｕ、ＣｒあるいはＮｉの添加量を多くすることによって腐食率は低くなり耐候性は向上するが、同時に硬さが増加し、機械加工性が低下する。添加量がＣｕ０．２０％、Ｎｉ及びＣｒともに０．１０％である参考例２が、合金元素添加の参考例中では最も硬さの増大が抑制されているが、腐食率は０．８３にとどまり、耐候性は不充分である。したがって、硬さの増大がより少なく、さらにはチル発生や他の機械的性質劣化もより少なく、かつ腐食率もより低い耐候性球状黒鉛鋳鉄が求められていた。
【０００９】
他方、材料再利用の観点からは、従来の耐候性鋳鉄はこれを戻り材として利用する場合、製造された鋳鉄の機械的性質が劣化してしまい、再利用は困難であった。したがって、耐候性鋳鉄のリサイクル性を高めるとともに球状黒鉛鋳鉄の製造コスト削減を図るためには、戻り材を通常の鋳鉄の原材料として再利用できるような耐候性鋳鉄製造技術の確立が求められていた。
【００１０】
本発明の課題は、このような従来技術の欠点を解決して、耐候性を有するとともに切削性等の機械加工性に影響を与える機械的性質の劣化を抑制した球状黒鉛鋳鉄及びその製造方法を提供することである。
【００１１】
また本発明の課題は、戻り材を通常の鋳鉄の原材料として再利用することができる耐候性球状黒鉛鋳鉄及びその製造方法を提供することである。
【００１２】
【課題を解決するための手段】
上記課題を解決するため本願発明者が鋭意検討した結果、Ｍｏを微量二次添加することにより、上記課題を解決できることを見出し、本発明に至った。すなわち、本願において特許請求される発明は以下のとおりである。
【００１３】
（１）質量％で、Ｃｕ：０．２〜２．０％、Ｎｉ：０．１〜２．０％、Ｃｒ：０．１〜１．０％、及びＭｏ：０．０１〜０．２％を含むことを特徴とする、耐候性球状黒鉛鋳鉄。
【００１４】
（２）質量％で、Ｃｕ：０．２〜１．０％、Ｎｉ：０．１〜１．０％、Ｃｒ：０．１〜０．３％、及びＭｏ：０．０２５〜０．１７５％を含むことを特徴とする、耐候性球状黒鉛鋳鉄。
【００１５】
（３）質量％でＣ：２．５〜４．０％、Ｃｕ：０．２〜０．４％、Ｎｉ：０．１〜１．０％、Ｃｒ０．１〜０．３％、及びＭｏ：０．０２５〜０．１７５％を含み、残部が実質的にＦｅ及び不可避的不純物元素からなることを特徴とする、耐候性球状黒鉛鋳鉄。
【００１６】
（４）日本工業規格Ｚ２３７１による環境サイクル試験における腐食量が、日本工業規格ＦＣＤ４５０に相当する球状黒鉛鋳鉄を１とした場合に、０．７以下であることを特徴とする、（１）ないし（３）のいずれかの耐候性球状黒鉛鋳鉄。
【００１７】
（５）ブリネル硬さが２３０ＨＢ以下、かつチル長さが３０ｍｍ以下であることを特徴とする、（１）ないし（４）のいずれかの耐候性球状黒鉛鋳鉄。
【００１８】
（６）日本工業規格Ｇ５５０２による引張強さが４５０Ｎ／ｍｍ^２以上、かつ伸びが１０％以上であることを特徴とする、（１）ないし（５）のいずれかの耐候性球状黒鉛鋳鉄。
【００１９】
（７）球状黒鉛鋳鉄を溶解して、これに質量％でＣｕ：０．２〜１．０％、Ｎｉ：０．１〜１．０％、Ｃｒ：０．１〜０．３％を添加する第１工程と、さらにこれに、質量％でＭｏ：０．０２５〜０．１７５％を添加する第２工程とを経て耐候性球状黒鉛鋳鉄を得る、耐候性球状黒鉛鋳鉄の製造方法。
【００２０】
すなわち本発明は、Ｃｕ、Ｎｉ、及びＣｒを微量添加配合する従来技術の耐候性向上手段に加えて、Ｍｏを微量添加することにより、硬さの増大やチル発生等の機械的性質の劣化を抑制して、耐候性鋳鉄における切削性等の機械加工性を改善するものである。
【００２１】
上述のように、従来の耐候性鋳鉄において機械的性質劣化を抑制するためにはＣｕ、Ｎｉ、及びＣｒの添加配合量を低くすることが効果的であるが、それのみでは耐候性を向上させる効果には限界がある。本発明の耐候性球状黒鉛鋳鉄及びその製造方法においては、このようなＣｕ、Ｎｉ、及びＣｒの添加配合量を低くすることによる耐候性の低下を、Ｍｏ微量添加によって防止し、さらに機械的性質をも改善することができる。また、本発明の耐候性球状黒鉛鋳鉄を戻り材として通常の鋳鉄の原材料として球状黒鉛鋳鉄を製造する場合、製品の機械的性質の劣化が抑制される。したがって、本発明の耐候性球状黒鉛鋳鉄は何ら問題なく再利用することができる。
【００２２】
【発明の実施の形態】
以下、本発明をより詳細に説明する。
本発明の耐候性球状黒鉛鋳鉄は、球状黒鉛鋳鉄中に、質量％でＣｕ：０．２〜２．０％、Ｎｉ：０．１〜２．０％、Ｃｒ：０．１〜１．０％、及びＭｏ：０．０１〜０．２％をそれぞれ含むことを主たる構成とする（請求項１）。球状黒鉛鋳鉄の種類としては特に限定されずあらゆるものを含むことができ、本発明の特徴である各合金元素が添加含有される点を除けば、引張強さ４５０Ｎ／ｍｍ^２以上その他の機械的性質を有するＦＣＤ４５０（ＪＩＳ規格　２種球状黒鉛鋳鉄）に相当する球状黒鉛鋳鉄も該当する。この点は、以下の各発明においても同様である。
【００２３】
Ｃｕ、Ｎｉ、及びＣｒはいずれも鋳鉄に耐候性を付与することのできる合金元素であり、Ｃｕは鋳鉄中に０．２〜２．０％含有させることにより偏析を抑制しつつ耐候性を向上させ、ＣｒはＣｕやＮｉの存在下で０．１〜１．０％含有させることにより白鉄化傾向を抑制しつつ耐候性効果を奏し、Ｎｉは０．１〜２．０％含有させることによりコスト上合理的な範囲内でＣｒ偏析の低減と錆層安定化の効果を奏することが知られている（特開平３−２９１３５４号公報）。Ｍｏもまた耐食性元素であり、その添加により、耐候性元素であるＣｕやＣｒの添加による機械的性質の劣化を抑制しつつ耐候性を付与することができる。
【００２４】
本発明の耐候性球状黒鉛鋳鉄は、球状黒鉛鋳鉄中に添加、含有させる各合金元素の含有量範囲を、望ましくは質量％でＣｕ：０．２〜１．０％（より望ましくは、Ｃｕ：０．２〜０．４％）、Ｎｉ：０．１〜１．０％、Ｃｒ：０．１〜０．３％、及びＭｏ：０．０２５〜０．１７５％をそれぞれ含む構成とすることができる（請求項２）。上述のとおり、従来の耐候性鋳鉄において機械的性質劣化を抑制するためには、Ｃｕ、Ｎｉ、及びＣｒの添加配合量を低くすることが効果的であり、従来用いられていた含有量範囲を機械的性質劣化抑制の効果がより一層得られる範囲に設定したものである。すなわち、含有させるＣｕ、Ｎｉ、Ｃｒを上記範囲とすることにより、硬さの増大やチル発生をより抑制した耐候性球状黒鉛鋳鉄とすることができる。
【００２５】
しかしながらそれのみでは腐食率を抑制できず耐候性を向上させる効果には限界がある。そこでこのようなＣｕ、Ｎｉ、及びＣｒの含有量を低くすることによる耐候性の低下を、Ｍｏを０．０２５〜０．１７５％（より望ましくは、０．０５％〜０．１５％）添加、含有させることによって防止することができる。Ｍｏを０．０２５％以上含有させることにより、腐食率は一層低下し、また、上限を０．１７５％とすることにより、チル発生を一層抑制することができる。
【００２６】
本発明の耐候性球状黒鉛鋳鉄は上述のとおりＦＣＤ４５０（ＪＩＳ規格　２種球状黒鉛鋳鉄）に相当する球状黒鉛鋳鉄もこれに該当するため、質量％で、Ｃ：２．５〜４．０％、Ｃｕ：０．２〜０．４％、Ｎｉ：０．１〜１．０％、Ｃｒ：０．１〜０．３％、及びＭｏ：０．０２５〜０．１７５％を含み、残部が実質的にＦｅ及びＳｉ、Ｍｎ、Ｐ、Ｓといった不可避的不純物元素からなる構成とすることができる（請求項３）。
【００２７】
本発明の耐候性球状黒鉛鋳鉄は、上述のような元素組成を有することにより、ＪＩＳ規格Ｚ２３７１による環境サイクル試験における腐食量を、前記ＦＣＤ４５０に相当する球状黒鉛鋳鉄を１とした場合に０．７６以下、さらには０．７以下とすることができ、充分な耐候性を示すものである（請求項４）。
【００２８】
本発明の耐候性球状黒鉛鋳鉄は、上述のような元素組成を有することにより、ブリネル硬さを２３０ＨＢ以下（さらには２２０ＨＢ以下）、かつチル長さを３０ｍｍ以下（さらには２０ｍｍ以下）とすることができ、耐候性元素Ｃｕ等を添加することによる機械的性質の劣化を抑制することができる（請求項５）。これらの物性値上限値は、切削性等の機械加工性を確保する上で求められるものであり、本発明の耐候性球状黒鉛鋳鉄はこれら望ましい機械的性質を備える。
【００２９】
また本発明の耐候性球状黒鉛鋳鉄は、上述のような元素組成を有することにより、ＪＩＳ規格Ｇ５５０２による引張強さを４５０Ｎ／ｍｍ^２以上、かつ伸びを１０％以上とすることができる（請求項６）。これらの物性値下限値は、ＪＩＳ規格２種球状黒鉛鋳鉄の機械的性質を確保する上で求められるものであり、本発明の耐候性球状黒鉛鋳鉄はこれら望ましい機械的性質を備える。
【００３０】
図１は、本発明の耐候性球状黒鉛鋳鉄の製造方法を示すフロー図である。図において本方法では、球状黒鉛鋳鉄１を溶解して、これに質量％でＣｕ：０．２〜１．０％、Ｎｉ：０．１〜１．０％、Ｃｒ：０．１〜０．３％を添加する第１工程Ｐ１と、さらにこれに、質量％でＭｏ：０．０２５〜０．１７５％を添加する第２工程Ｐ２とを経て、耐候性球状黒鉛鋳鉄２を得る。図中、第１工程Ｐ１で添加する合金元素の添加量は、より望ましくは質量％でＣｕ：０．２〜０．４％、Ｎｉ：０．１〜１．０％、Ｃｒ：０．１〜０．３％とし、また第２工程Ｐ２で添加するＭｏの量は、より望ましくは、０．０５％〜０．１５％とすることができる。本発明の耐候性球状黒鉛鋳鉄製造方法では、このような簡便な手順により、機械的性質の劣化を抑制した耐候性球状黒鉛鋳鉄を得ることができる。
【００３１】
【実施例】
以下、本発明を実施例によりさらに具体的に説明するが、本発明はこれらの実施例に限定されるものではない。
＜供試材＞
供試材として、溶解実験により組成の異なる球状黒鉛鋳鉄を製作した。ＪＩＳ規格ＦＣＤ４５０に相当する球状黒鉛鋳鉄を母材として、これに所定量のＣｕ、Ｎｉ、及びＣｒを添加し、さらに所定量のＭｏを二次添加した。
【００３２】
＜耐候性の評価方法＞
製作した各供試材を試料とし、耐候性（耐食性）関連項目として、ＪＩＳ規格Ｚ２３７１による環境サイクル試験を行った。すなわち、浸漬複合腐食試験機を用い、所定の温度−湿度条件、及び塩水噴霧−乾燥−湿潤のサイクルにより、２週間の環境サイクル試験を実施した。評価はＦＣＤ４５０における腐食量（ｍｇ／ｃｍ^２）を１とした場合の相対値で比較した。なお試験片には、その一部をチル試験及び硬さ試験にも用いる階段状試験片を用いた。仕様は幅７０ｍｍ、長さ５０ｍｍの段が５段からなり、最小高さ３ｍｍ、最大高さ３０ｍｍである。
【００３３】
＜機械的性質の評価方法＞
製作した各供試材を試料とし、機械的性質関連項目としてブリネル硬さ試験、チル試験、強度試験等を行った。チル試験及び硬さ試験には、前記階段状試験片を用いた。なお試験片には、その一部をチル試験及び硬さ試験にも用いる階段状試験片を用いた。強度試験にはＹブロックＡ号試験片を用い、ＪＩＳ規格Ｇ５５０２による引張強さ、及び伸びを測定した。
【００３４】
＜耐候性―腐食率の改善＞
表２に、本発明の各実施例及び比較例について添加元素組成と腐食率測定結果を示す。表中、比較例１はＦＣＤ４５０に各耐候性元素を添加しなかったもの、比較例２はＣｕ、Ｎｉ、及びＣｒのみを添加し、Ｍｏは添加しなかったものである。各実施例はＣｕ、Ｎｉ、及びＣｒの添加量を一定とし、Ｍｏの添加量をそれぞれ変えた。
【００３５】
【表２】

【００３６】
表に示されるように、機械的性質劣化を抑制するためにＣｕ、Ｎｉ、及びＣｒの添加量をそれぞれ０．２０％、０．１０％、０．１０％にとどめても、Ｍｏを０．０２５％以上添加することにより、腐食率を０．７６以下とすることができた。さらに実施例２〜６でＭｏ添加量を０．０５％以上とすることにより、腐食率を０．７１以下とすることができた。特に実施例３（Ｍｏ：０．１０％）、実施例５（Ｍｏ：０．１７５％）等では、腐食率を０．６程度にまで改善することができた。
【００３７】
＜ブリネル硬さ＞
表３に、表２に示した本発明の各実施例及び比較例についてのブリネル硬さ測定結果を示す。
【００３８】
【表３】

【００３９】
表に示されるように、各実施例とも、Ｍｏ添加のない比較例２と同等程度の硬さ２０１〜２１５を示し、本発明の耐候性球状黒鉛鋳鉄は良好な機械的性質を維持しつつ耐候性を高められる（表２）ことが示された。
【００４０】
＜チル長さ＞
表４に、表２に示した本発明の各実施例及び比較例についてのチル長さ測定結果を示す。
【００４１】
【表４】

【００４２】
表に示されるように、実施例１〜４ではチル長さがいずれも２０ｍｍ以下であり、良好な機械的性質が得られた。実施例５及び６ではチル長さが３０ｍｍを超えており、したがってチル発生抑制の観点からは、Ｍｏ添加量上限は０．１７５％とすることがより望ましいと考えられた。
【００４３】
＜引張強さ＞
表５に、表２に示した本発明の各実施例及び比較例についての引張強さ測定結果を示す。
【００４４】
【表５】

【００４５】
表に示されるように、実施例１〜６のいずれも引張強さは４５０Ｎ／ｍｍ^２以上であり、良好な機械的性質が得られた。
【００４６】
＜伸び＞
表６に、表２に示した本発明の各実施例、及び比較例についての伸び測定結果を示す。表中、比較例３は比較例２同様Ｃｕ、Ｎｉ、及びＣｒのみを添加しＭｏを添加しないものであるが、Ｃｕ等の添加量を比較例２よりも少なくした点が異なる。
【００４７】
【表６】

【００４８】
表に示されるように、実施例１〜６のいずれも伸びは１０％以上であり、良好な機械的性質が得られた。
【００４９】
＜戻り材使用＞
本発明により製造した耐候性球状黒鉛鋳鉄の戻り材について、これを再利用して球状黒鉛鋳鉄を製造した場合の機械的性質を検討した。３０％の通常配合と、８０％の大量配合により実験した。
表７に、本発明の実施例及び比較例について、戻り材を使用して鋳鉄を製造した例の成分表を示す。表中、比較例４〜６及び実施例７は、戻り材３０％使用による球状黒鉛鋳鉄、比較例７〜９及び実施例８は、戻り材８０％使用による球状黒鉛鋳鉄である。また、比較例４及び７は実質的に耐候性元素無添加であり、機械的性質の評価上ＦＣＤ４５０球状黒鉛鋳鉄と同等である。比較例５、６、８、及び９はＣｕ、Ｎｉ、及びＣｒ添加、Ｍｏ無添加である。
【００５０】
【表７】

【００５１】
表８に、表７に示した各実施例及び比較例についての機械的性質各関連項目の測定結果を示す。
【００５２】
【表８】

【００５３】
表に示されるように、戻り材３０％配合の通常配合では、硬さ、引張強さ、伸びとも、Ｍｏを添加した本発明の実施例７が比較例５及び６よりも、より耐候性元素無添加のＦＣＤ４５０（比較例４）の機械的性質に近く、ほぼ同等の機械的性質を示した。また８０％の大量配合の場合でも、硬さ、引張強さ、伸びとも、Ｍｏを添加した本発明の実施例８が比較例８及び９よりも、より耐候性元素無添加のＦＣＤ４５０（比較例７）の機械的性質に近く、ＦＣＤ４５０規格内の機械的性質を示した。したがって、戻り剤３０％の場合はもちろん、３０％の大量配合の場合にも、本発明の耐候性球状黒鉛鋳鉄は、機械的性質の劣化を抑制した再利用が可能であることが示された。
【００５４】
【発明の効果】
本発明の耐候性球状黒鉛鋳鉄及びその製造方法は上述のように構成されているため、球状黒鉛鋳鉄において、充分な耐候性を有しつつ、硬さの増大、チル発生その他の機械的性質劣化を抑制することができ、したがって切削性等の機械加工性を良好に維持することができる。
【００５５】
また本発明による耐候性球状黒鉛鋳鉄は、戻り材を通常の鋳鉄の原材料として再利用する場合にも機械的性質の劣化を抑制することができ、耐候性鋳鉄のリサイクル性を高めるとともに球状黒鉛鋳鉄の製造コストを削減することができる。
【図面の簡単な説明】
【図１】本発明の耐候性球状黒鉛鋳鉄の製造方法を示すフロー図である。
【符号の説明】
１…球状黒鉛鋳鉄、　２…耐候性球状黒鉛鋳鉄、　Ｐ１…第１工程、　Ｐ２…第２工程[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a spheroidal graphite cast iron having excellent weather resistance and a method for producing the same, and more particularly to a novel improvement having excellent weather resistance, improved cutting properties and suppressed deterioration of mechanical properties.
[0002]
[Prior art]
In recent years, landscape castings, which are cast iron, have been increasingly used as landscape materials. For example, architectural members such as design panels and balcony castings, landscape materials such as outdoor lights, fences, monuments, and the like are expected to increase in demand in the future. However, cast iron for such applications is left outdoors and is exposed to the outside air, so that it is required to have higher weather resistance. There are also research examples on the improvement of the quality of landscape castings, and techniques for improving weather resistance have been proposed. At present, cast iron containing a large amount of Cu or Cr is widely used as weather-resistant cast iron.
[0003]
Japanese Unexamined Patent Publication No. Hei 3-291354 discloses that, by adding a small amount of Cu, Ni, Cr, and other alloy elements, cast iron for building and structural / design members excellent in weather resistance in the atmosphere can be obtained. Is disclosed.
[0004]
[Problems to be solved by the invention]
However, conventional weather-resistant cast irons to which Cu, Cr, etc. are added have problems in terms of deterioration of mechanical properties and reusability. The material cannot be easily manufactured. That is, in conventional weather-resistant cast iron, mechanical properties such as chill generation and an increase in hardness, which affect machinability such as machinability, are likely to occur, and heat treatment equipment that requires considerable cost to prevent this is likely to occur. Etc. are required. Therefore, there has been a demand for a method of easily manufacturing weatherable cast iron while suppressing costs without making such new capital investment.
[0005]
Table 1 shows examples of the weather resistance and mechanical properties of the conventional weather-resistant cast iron depending on the alloying element addition conditions.
[0006]
[Table 1]

[0007]
In the table, Reference Example 1 is spheroidal graphite cast iron corresponding to Japanese Industrial Standard (hereinafter, also referred to as “JIS”) FCD450. Reference Examples 2 to 7 are weatherable spheroidal graphite cast irons obtained by melting the spheroidal graphite cast iron of Reference Example 1 and adding a predetermined amount of each alloy element thereto. The unit of the addition amount is% by mass with the mass of the spheroidal graphite cast iron equivalent to FCD450 of Reference Example 1 used being 100% (hereinafter, when simply expressed as “%”, it means “% by mass”). . The weather resistance is evaluated based on the amount of corrosion generated by an environmental cycle test according to Z2371 (JIS). Specifically, it is shown as a relative numerical value when the amount of corrosion in the spheroidal graphite cast iron equivalent to FCD450 (Reference Example 1) is set to 1.
[0008]
As shown in the table, by increasing the amount of Cu, Cr or Ni added, the corrosion rate decreases and the weather resistance improves, but at the same time, the hardness increases and the machinability decreases. In Reference Example 2 in which the addition amount is Cu 0.20% and Ni and Cr are both 0.10%, the increase in hardness is most suppressed in the reference example in which the alloy element is added, but the corrosion rate is 0.83. The weather resistance is insufficient. Accordingly, there has been a need for a weather-resistant spheroidal graphite cast iron with less increase in hardness, less chilling and other deterioration in mechanical properties, and a lower corrosion rate.
[0009]
On the other hand, from the viewpoint of material reuse, when the conventional weather-resistant cast iron is used as a return material, the mechanical properties of the manufactured cast iron are deteriorated, and it is difficult to reuse the cast iron. Therefore, in order to increase the recyclability of the weather-resistant cast iron and reduce the production cost of the spheroidal graphite cast iron, it was required to establish a weather-resistant cast iron manufacturing technology capable of reusing the returned material as a raw material for ordinary cast iron. .
[0010]
An object of the present invention is to solve the drawbacks of the prior art and to provide a spheroidal graphite cast iron having weather resistance and suppressing deterioration of mechanical properties that affect machinability such as machinability, and a method for producing the same. To provide.
[0011]
Another object of the present invention is to provide a weather-resistant spheroidal graphite cast iron in which a returned material can be reused as a raw material of ordinary cast iron, and a method for producing the same.
[0012]
[Means for Solving the Problems]
As a result of intensive studies by the present inventor to solve the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by adding a small amount of Mo, and have reached the present invention. That is, the invention claimed in the present application is as follows.
[0013]
(1) In mass%, Cu: 0.2 to 2.0%, Ni: 0.1 to 2.0%, Cr: 0.1 to 1.0%, and Mo: 0.01 to 0.2. % Weather-resistant spheroidal graphite cast iron.
[0014]
(2) By mass%, Cu: 0.2 to 1.0%, Ni: 0.1 to 1.0%, Cr: 0.1 to 0.3%, and Mo: 0.025 to 0.175. % Weather-resistant spheroidal graphite cast iron.
[0015]
(3) C: 2.5 to 4.0%, Cu: 0.2 to 0.4%, Ni: 0.1 to 1.0%, Cr 0.1 to 0.3%, and Mo by mass% : A weatherable spheroidal graphite cast iron containing 0.025 to 0.175%, with the balance substantially consisting of Fe and inevitable impurity elements.
[0016]
(4) The amount of corrosion in an environmental cycle test according to Japanese Industrial Standard Z2371 is 0.7 or less when the spheroidal graphite cast iron corresponding to Japanese Industrial Standard FCD450 is 1, 3) The weatherable spheroidal graphite cast iron according to any of 3).
[0017]
(5) The weatherable spheroidal graphite cast iron according to any one of (1) to (4), having a Brinell hardness of 230 HB or less and a chill length of 30 mm or less.
[0018]
(6) The weatherable spheroidal graphite cast iron according to any one of (1) to (5), which has a tensile strength according to Japanese Industrial Standard G5502 of 450 N / mm ² or more and an elongation of 10% or more.
[0019]
(7) Spheroidal graphite cast iron is melted, and Cu: 0.2-1.0%, Ni: 0.1-1.0%, Cr: 0.1-0.3% are added by mass%. A method for producing a weather-resistant spheroidal graphite cast iron through a first step of adding Mo: 0.025 to 0.175% by mass to the second step of obtaining a weather-resistant spheroidal graphite cast iron.
[0020]
That is, in the present invention, in addition to the conventional technique for improving the weather resistance in which trace amounts of Cu, Ni, and Cr are added and blended, by adding a trace amount of Mo, mechanical properties such as increase in hardness and generation of chill can be prevented. It is intended to improve the machinability, such as the machinability, of the weather-resistant cast iron by suppressing it.
[0021]
As described above, in order to suppress the deterioration of mechanical properties in the conventional weather-resistant cast iron, it is effective to lower the additive compounding amount of Cu, Ni, and Cr, but it alone improves the weather resistance. The effect is limited. In the weather-resistant spheroidal graphite cast iron of the present invention and the method for producing the same, the decrease in weather resistance due to the lower addition of Cu, Ni, and Cr is prevented by adding a trace amount of Mo, and the mechanical properties are further reduced. Can also be improved. Further, when the spheroidal graphite cast iron of the present invention is used as a raw material of ordinary cast iron by using the spheroidal graphite cast iron of the present invention as a return material, deterioration of mechanical properties of the product is suppressed. Therefore, the weather-resistant spheroidal graphite cast iron of the present invention can be reused without any problem.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in more detail.
The weatherable spheroidal graphite cast iron of the present invention is obtained by adding, in mass%, Cu: 0.2 to 2.0%, Ni: 0.1 to 2.0%, and Cr: 0.1 to 1.0 in mass%. %, And Mo: 0.01 to 0.2%, respectively. The type of the spheroidal graphite cast iron is not particularly limited, and can include any type. Except that each alloy element which is a feature of the present invention is added and contained, the tensile strength is 450 N / mm ² or more. A spheroidal graphite cast iron corresponding to FCD450 (JIS type 2 spheroidal graphite cast iron) having properties also applies. This applies to the following inventions.
[0023]
Cu, Ni, and Cr are all alloying elements capable of imparting weather resistance to cast iron, and Cu is included in the cast iron in an amount of 0.2 to 2.0% to improve segregation while suppressing segregation. The Cr content is 0.1 to 1.0% in the presence of Cu or Ni to provide a weathering effect while suppressing the tendency to white iron, and the Ni content is 0.1 to 2.0%. It is known that the effect of reducing the segregation of Cr and stabilizing the rust layer can be achieved within a reasonable range in terms of cost (JP-A-3-291354). Mo is also a corrosion-resistant element, and its addition can provide weather resistance while suppressing deterioration of mechanical properties due to addition of the weather-resistant elements Cu and Cr.
[0024]
The weather-resistant spheroidal graphite cast iron of the present invention is characterized in that the content range of each alloying element to be added and contained in the spheroidal graphite cast iron is preferably Cu: 0.2 to 1.0% by mass% (more desirably, Cu: 0.2 to 0.4%), Ni: 0.1 to 1.0%, Cr: 0.1 to 0.3%, and Mo: 0.025 to 0.175%. (Claim 2). As described above, in order to suppress the mechanical property deterioration in the conventional weatherable cast iron, it is effective to reduce the additive compounding amount of Cu, Ni, and Cr, and the content range conventionally used is reduced. The range is set so that the effect of suppressing mechanical property deterioration can be further obtained. That is, by setting Cu, Ni, and Cr to be in the above ranges, it is possible to obtain a weather-resistant spheroidal graphite cast iron in which increase in hardness and generation of chill are further suppressed.
[0025]
However, this alone cannot suppress the corrosion rate, and there is a limit to the effect of improving the weather resistance. Therefore, the decrease in the weather resistance due to the reduction of the contents of Cu, Ni, and Cr is explained by adding Mo in an amount of 0.025 to 0.175% (more desirably, 0.05% to 0.15%). , Can be prevented. By containing Mo in an amount of 0.025% or more, the corrosion rate is further reduced, and by setting the upper limit to 0.175%, chill generation can be further suppressed.
[0026]
As described above, the weather-resistant spheroidal graphite cast iron of the present invention also corresponds to the spheroidal graphite cast iron corresponding to FCD450 (JIS standard type 2 spheroidal graphite cast iron). Therefore, in mass%, C: 2.5 to 4.0%, Cu: 0.2 to 0.4%, Ni: 0.1 to 1.0%, Cr: 0.1 to 0.3%, and Mo: 0.025 to 0.175%, with the balance being substantial In addition, it is possible to adopt a configuration composed of unavoidable impurity elements such as Fe and Si, Mn, P, and S (claim 3).
[0027]
The weatherable spheroidal graphite cast iron of the present invention has an elemental composition as described above, so that the amount of corrosion in an environmental cycle test according to JIS standard Z2371 is 0.76 when the spheroidal graphite cast iron corresponding to the FCD450 is set to 1. Hereinafter, it can be set to 0.7 or less, which shows sufficient weather resistance (claim 4).
[0028]
The weathering spheroidal graphite cast iron of the present invention has a Brinell hardness of 230 HB or less (furthermore, 220 HB or less) and a chill length of 30 mm or less (furthermore, 20 mm or less) by having the above element composition. And deterioration of mechanical properties due to the addition of the weathering element Cu or the like can be suppressed (claim 5). These physical property upper limits are required in order to ensure machinability such as machinability, and the weatherable spheroidal graphite cast iron of the present invention has these desirable mechanical properties.
[0029]
In addition, the weather-resistant spheroidal graphite cast iron of the present invention can have a tensile strength of 450 N / mm ² or more and an elongation of 10% or more according to JIS G5502 by having the above element composition. 6). These physical property lower limits are required to secure the mechanical properties of JIS standard type 2 spheroidal graphite cast iron, and the weatherable spheroidal graphite cast iron of the present invention has these desirable mechanical properties.
[0030]
FIG. 1 is a flowchart showing a method for producing a weather-resistant spheroidal graphite cast iron of the present invention. In the figure, in the present method, the spheroidal graphite cast iron 1 is melted, and Cu: 0.2 to 1.0%, Ni: 0.1 to 1.0%, Cr: 0.1 to 0. A first step P1 in which 3% is added, and a second step P2 in which Mo: 0.025 to 0.175% is added by mass% to obtain a weather-resistant spheroidal graphite cast iron 2. In the figure, the addition amount of the alloy element added in the first step P1 is more desirably in mass%: Cu: 0.2 to 0.4%, Ni: 0.1 to 1.0%, Cr: 0.1 To 0.3%, and the amount of Mo added in the second step P2 can be more desirably 0.05% to 0.15%. According to the method for manufacturing a weather-resistant spheroidal graphite cast iron of the present invention, it is possible to obtain a weather-resistant spheroidal graphite cast iron in which deterioration of mechanical properties is suppressed by such a simple procedure.
[0031]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.
<Test material>
As test materials, spheroidal graphite cast irons having different compositions were manufactured by melting experiments. A spheroidal graphite cast iron corresponding to JIS standard FCD450 was used as a base material, to which a predetermined amount of Cu, Ni, and Cr was added, and further, a predetermined amount of Mo was secondarily added.
[0032]
<Weather resistance evaluation method>
Each of the manufactured test materials was used as a sample, and an environmental cycle test according to JIS standard Z2371 was performed as an item related to weather resistance (corrosion resistance). That is, a two-week environmental cycle test was performed using a immersion composite corrosion tester under predetermined temperature-humidity conditions and a salt spray-dry-wet cycle. The evaluation was made based on a relative value when the corrosion amount (mg / cm ² ) in FCD450 was set to 1. As the test piece, a step-like test piece, a part of which is also used for the chill test and the hardness test, was used. The specification consists of five steps of 70 mm in width and 50 mm in length, with a minimum height of 3 mm and a maximum height of 30 mm.
[0033]
<Evaluation method of mechanical properties>
Each of the manufactured test materials was used as a sample, and a Brinell hardness test, a chill test, a strength test, and the like were performed as mechanical property-related items. For the chill test and the hardness test, the step-like test piece was used. As the test piece, a step-like test piece, a part of which is also used for the chill test and the hardness test, was used. In the strength test, a Y-block No. A test piece was used to measure the tensile strength and elongation according to JIS standard G5502.
[0034]
<Weather resistance-improvement of corrosion rate>
Table 2 shows the results of measurement of the additive element composition and the corrosion rate for each example and comparative example of the present invention. In the table, Comparative Example 1 was obtained by adding no weather-resistant element to FCD450, and Comparative Example 2 was obtained by adding only Cu, Ni, and Cr and not adding Mo. In each example, the added amounts of Cu, Ni, and Cr were fixed, and the added amounts of Mo were changed.
[0035]
[Table 2]

[0036]
As shown in the table, even when the addition amounts of Cu, Ni, and Cr are limited to 0.20%, 0.10%, and 0.10%, respectively, in order to suppress the deterioration of mechanical properties, the Mo content is reduced to 0.1%. By adding 025% or more, the corrosion rate could be reduced to 0.76 or less. Further, in Examples 2 to 6, the corrosion rate could be reduced to 0.71 or less by setting the amount of Mo added to 0.05% or more. In particular, in Example 3 (Mo: 0.10%) and Example 5 (Mo: 0.175%), the corrosion rate could be improved to about 0.6.
[0037]
<Brinell hardness>
Table 3 shows the Brinell hardness measurement results for each of the examples and comparative examples of the present invention shown in Table 2.
[0038]
[Table 3]

[0039]
As shown in the table, each of Examples shows the same hardness 201 to 215 as that of Comparative Example 2 without Mo addition, and the weatherable spheroidal graphite cast iron of the present invention has good weatherability while maintaining good mechanical properties. (Table 2).
[0040]
<Chill length>
Table 4 shows the chill length measurement results for each of the examples and comparative examples of the present invention shown in Table 2.
[0041]
[Table 4]

[0042]
As shown in the table, in Examples 1 to 4, the chill length was all 20 mm or less, and good mechanical properties were obtained. In Examples 5 and 6, the chill length exceeded 30 mm. Therefore, from the viewpoint of suppressing chill generation, it was considered that the upper limit of the amount of Mo added was more preferably 0.175%.
[0043]
<Tensile strength>
Table 5 shows the results of measuring the tensile strength of the examples and comparative examples of the present invention shown in Table 2.
[0044]
[Table 5]

[0045]
As shown in the table, in all of Examples 1 to 6, the tensile strength was 450 N / mm ² or more, and good mechanical properties were obtained.
[0046]
<Elongation>
Table 6 shows the elongation measurement results for the examples of the present invention and the comparative examples shown in Table 2. In the table, Comparative Example 3 is similar to Comparative Example 2 except that only Cu, Ni, and Cr are added and Mo is not added, except that the added amount of Cu and the like is smaller than Comparative Example 2.
[0047]
[Table 6]

[0048]
As shown in the table, in all of Examples 1 to 6, the elongation was 10% or more, and good mechanical properties were obtained.
[0049]
<Use of return material>
The mechanical properties of the recycle material of the weather-resistant spheroidal graphite cast iron manufactured according to the present invention were examined when the spheroidal graphite cast iron was manufactured by reusing it. Experiments were performed with a 30% normal formulation and a 80% large formulation.
Table 7 shows a composition table of an example in which cast iron was manufactured using a return material for Examples and Comparative Examples of the present invention. In the table, Comparative Examples 4 to 6 and Example 7 are spheroidal graphite cast irons using 30% of returned material, and Comparative Examples 7 to 9 and Example 8 are spheroidal graphite cast irons using 80% of the returned material. Comparative Examples 4 and 7 were substantially free of a weather-resistant element, and were equivalent to FCD450 spheroidal graphite cast iron in evaluation of mechanical properties. In Comparative Examples 5, 6, 8, and 9, Cu, Ni, and Cr were added, and Mo was not added.
[0050]
[Table 7]

[0051]
Table 8 shows the measurement results of the relevant items of the mechanical properties for each of the examples and comparative examples shown in Table 7.
[0052]
[Table 8]

[0053]
As shown in the table, in the normal blend of the 30% return material blend, the hardness, tensile strength, and elongation of Example 7 of the present invention to which Mo was added were higher than those of Comparative Examples 5 and 6 in comparison with Comparative Examples 5 and 6. The mechanical properties were close to those of FCD450 (Comparative Example 4) to which no additive was added, and exhibited almost the same mechanical properties. In addition, even in the case of a large amount blend of 80%, Example 8 of the present invention to which Mo was added was compared with Comparative Examples 8 and 9 in terms of hardness, tensile strength, and elongation. It was close to the mechanical property of 7) and showed mechanical properties within the FCD450 standard. Therefore, it was shown that the weatherable spheroidal graphite cast iron of the present invention can be reused while suppressing the deterioration of the mechanical properties, not only in the case of the reversion agent of 30% but also in the case of a large amount of 30%. .
[0054]
【The invention's effect】
Since the weatherable spheroidal graphite cast iron of the present invention and the method for producing the same are configured as described above, the spheroidal graphite cast iron has sufficient weather resistance, increases hardness, generates chill, and deteriorates other mechanical properties. Therefore, the machinability such as the machinability can be favorably maintained.
[0055]
Further, the weather-resistant spheroidal graphite cast iron according to the present invention can suppress the deterioration of the mechanical properties even when the returned material is reused as a raw material of ordinary cast iron. Manufacturing cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a flowchart showing a method for producing a weather-resistant spheroidal graphite cast iron of the present invention.
[Explanation of symbols]
1: Spheroidal graphite cast iron, 2: Weather resistant spheroidal graphite cast iron, P1: First step, P2: Second step

Claims (7)

In mass%, Cu: 0.2 to 2.0%, Ni: 0.1 to 2.0%, Cr: 0.1 to 1.0%, and Mo: 0.01 to 0.2% A weather-resistant spheroidal graphite cast iron, characterized in that: In mass%, Cu: 0.2 to 1.0%, Ni: 0.1 to 1.0%, Cr: 0.1 to 0.3%, and Mo: 0.025 to 0.175% A weatherable spheroidal graphite cast iron, characterized in that: C: 2.5-4.0%, Cu: 0.2-1.0%, Ni: 0.1-1.0%, Cr 0.1-0.3%, and Mo: 0. A weatherable spheroidal graphite cast iron containing 025 to 0.175%, with the balance substantially consisting of Fe and unavoidable impurity elements. 4. The amount of corrosion in an environmental cycle test according to Japanese Industrial Standard Z2371 is 0.7 or less when a spheroidal graphite cast iron corresponding to Japanese Industrial Standard FCD450 is set to 1. 2. The weather-resistant spheroidal graphite cast iron according to 1. The weatherable spheroidal graphite cast iron according to any one of claims 1 to 4, wherein the Brinell hardness is 230HB or less and the chill length is 30mm or less. JIS G5502 by a tensile strength of 450 N / mm ² or more, and wherein the elongation is 10% or more, the weather resistance spheroidal graphite cast iron according to any one of claims 1 to 5. The spheroidal graphite cast iron is melted, and Cu: 0.2 to 1.0%, Ni: 0.1 to 1.0%, and Cr: 0.1 to 0.3% are added by mass%. A method for producing a weather-resistant spheroidal graphite cast iron, which includes one step and a second step of further adding Mo: 0.025 to 0.175% by mass to the weather-resistant spheroidal graphite cast iron.

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