JP3999109B2 - Weather-resistant cast iron and method for producing the same - Google Patents

Description

【００２８】
実施例１、実施例２、参考例１、参考例２、実施例７〜実施例１０に係る試験片は、重量比で、炭素：２．５〜４．３％、シリコン：１．７〜３．０％、マンガン：０．０２〜２．０％、リン：０．９％以下、イオウ：０．９％以下を含む鋳鉄組成をもち、ニッケル：０．５〜４．３％、銅：０．１〜１．５％、モリブデン：０．０５〜１．５％の３種を含む。実施例５、参考例３に係る試験片は、炭素：３．２〜４．３％、シリコン：１．５〜３．５％、マンガン：０．０２〜２．０％、リン：０．９％以下、イオウ：０．９％以下、マグネシウム：０．９０％以下を含む鋳鉄組成をもち、ニッケル：０．５〜４．３％、銅：０．１〜１．５％、モリブデン：０．０５〜１．５％の３種を含む。各実施例の鋳鉄組成にはクロムは積極的元素としては含まれておらず、０．１％未満である。
【００２９】
比較例１に係る試験片、比較例２に係る試験片は、ニッケル、銅、モリブデンを積極的に含んでいない。
【００３０】
そして、各試験片を熱処理炉にそれぞれ装入し、大気雰囲気（酸素を含む雰囲気）において９３０℃の温度領域において５時間加熱保持する熱処理工程を実施した。熱処理後に試験片を熱処理炉から取り出し、炉冷により冷却した。
【００３１】
実施例に係る各試験片についてサンドブラスト処理を行い、実施例に係る各試験片の表面に形成されたスケールである酸化膜を除去したところ、黒錆を主体とする黒色の防錆層が形成されていた。防錆層の平均厚みは０．２〜０．４ｍｍ程度であった。この防錆層は試験片の母材に対する密着性が高かった。
【００３２】
比較例に係る各試験片についてサンドブラスト処理を行ない、表面に形成されたスケールである酸化膜を除去したところ、実施例のような黒錆を主体とする黒色の防錆層はほとんど形成されていなかった。
【００３３】
サンドブラスト処理を行った各試験片について、耐食性試験を実施した。この場合、塩水噴霧試験方法（ＪＩＳ Ｚ２３７１）を２４０時間行った。即ち、塩水を噴霧ノズルにより試験片の表面に噴霧して赤錆（Ｆｅ_２Ｏ_３）を生成させる試験を行った。赤錆は試験片の母材に対する密着性が低いため、母材から脱落し易い性質をもつ。塩水噴霧後、試験片に生成した赤錆をサンドブラスト処理により除去した。サンドブラスト処理では赤錆は除去されるものの、黒色の防錆層は除去されない。そして塩水噴霧前後における試験片の重量の減量を求め、これを腐食減量（％）とした。腐食減量が大きいほど耐食性が悪く、腐食減量が小さいほど耐食性が良好である。
【００３４】
試験結果を図１に示す。図１に示すように、片状黒鉛鋳鉄で形成されている比較例１，球状黒鉛鋳鉄で形成されている比較例２については、黒色の防錆層が形成されておらず、腐食減量が重量比で１．２％を越えており、かなり大きく、耐食性が良好ではなかった。
【００３５】
これに対して、ニッケル、銅、モリブデンの３種が含有されている片状黒鉛鋳鉄で形成されている実施例１、実施例２については、防錆層が良好であり、腐食減量が０．４％以下であり、耐食性が優れていた。ニッケル、モリブデンが含有されている片状黒鉛鋳鉄で形成されている参考例１については、防錆層が良好であり、腐食減量が０．８％以下であり、耐食性が良好であった。銅、ニッケルが含有されている片状黒鉛鋳鉄で形成されている参考例２については、防錆層が良好であり、腐食減量が０．８％以下であり、耐食性が良好であった。
【００３６】
またニッケル、銅、モリブデンが含有されている球状黒鉛鋳鉄で形成されている実施例５については、防錆層が良好であり、腐食減量が０．４％以下であり、耐食性が優れていた。ニッケル、銅が含有されている球状黒鉛鋳鉄で形成されている参考例３については、防錆層が良好であり、腐食減量が０．６％以下であり、耐食性が良好であった。
【００３７】
ニッケル、銅、モリブデンが含有されている片状黒鉛鋳鉄で形成されている実施例７〜実施例１０については、防錆層が良好であり、腐食減量が０．２％以下とかなり小さく、耐食性が優れていた。上記した試験結果から、本実施例に係る防錆層が耐食性に有効であることがわかる。
【００３８】
図２は、実施例１、実施例２、参考例１に係る試験片について、熱処理をしなかった場合と、９３０℃で２時間の熱処理をした場合と、９３０℃で５時間の熱処理をした場合とを比較して示す。図２に示すように、実施例１、実施例２、参考例１といえども、防錆層形成用の熱処理をしなかったときには、腐食減量がかなり大きく、耐食性は悪かった。しかし熱処理すれば、腐食減量が低下し、耐食性が向上する。殊に、熱処理の時間が長くなるにつれて、腐食減量が減少するため、耐食性が向上することがわかる。
【００３９】
実施例２について、試験片の表面部分の組織について光学顕微鏡で確認した。これを図３（倍率１００倍）,図４（倍率２００倍）に示す。図３，図４の組織はナイタル腐食液で腐食されている。図３,図４に示すように、試験片の内部では、パーライトを主体とする鋳鉄本体のマトリックスには多数の片状の黒鉛が分散していた。そして試験片の表面側の黒鉛は脱炭しており、試験片の表面側において防錆層の内側に、フェライトを主要組織として含む脱炭層であるフェライトリッチ層（平均厚み：２００〜５００μｍ）が形成されていた。フェライトリッチ層においてはフェライトの面積率は５０％以上であった。防錆層はフェライトリッチ層の外面側に形成されていた。図３,図４によれば、フェライトリッチ層におけるフェライトは比較的異形のものが多かった。熱処理時における黒鉛の脱炭が寄与しているものと推察される。フェライトの異形性は防錆層とフェライトとの密着性の向上に寄与でき、鋳鉄本体に対する防錆層の密着性の向上に寄与できるものと推察される。防錆層には空孔であるボイドが形成されていた。熱処理時における黒鉛の脱炭によるものと推察される。なおボイドは含油性の向上を期待できる。
【００４０】
（適用例）
図５は、ディスクロータ１００及びキャリパ２００を有するブレーキ装置を示す。この場合にはディスクロータ１００及びキャリパ２００に適用されている。ディスクロータ１００は片状黒鉛が分散した片状黒鉛鋳鉄で形成され、キャリパ２００は球状黒鉛が分散した球状黒鉛鋳鉄で形成されている。これの外壁面には、上記したように形成した黒錆を主体とする防錆層１１０,２１０が形成されている。ディスクロータ１００によれば、多数の片状黒鉛が基地に分散しているため、鋳鉄特有の利点である鋳造性、振動減衰性、熱伝導性等の特性を得ることができる。更に表面に防錆層１１０が形成されているため、耐食性を向上させることができ、ディスクロータ１００の長寿命化を図ることができる。また、ディスクロータ１００の複数のフィン部１２０は、耐食性を考慮して設計段階では厚肉に設定されるのが通常であるが、これらのフィン部１２０は防錆層１１０を有して耐食性が向上しているため、フィン部１２０を薄肉とすることが可能となり、ディスクロータ１００の軽量化も図ることができる。ディスクロータ１００の摩擦摺動面では、防錆層を切削加工で除去している。なおディスクロータ１００及びキャリパ２００に限らず、ブレーキシュー、シリンダブロック、シリンダカバー、キャリパサポート、ベアリングキャップ、デフケース、デフキャリア等の鋳鉄部品にも適用することができる。
【００４１】
（その他）その他、本発明は上記した実施例のみに限定されるものではなく、要旨を逸脱しない範囲内で適宜変更して実施できるものである。上記した記載から次の技術的思想も把握できる。
（付記項１）重量比で、ニッケル：０．５〜４．３％、銅：０．１〜１．５％、モリブデン：０．０５〜１．５％の３種を含む鉄−炭素系の鋳鉄組成をもつと共に内部に黒鉛が分散された耐候性鋳鉄であって、酸素を含む雰囲気において５００〜１２００℃の温度領域に加熱することにより、表面に黒錆を主体とする防錆層が形成されていることを特徴とする耐候性鋳鉄。
（付記項２）各請求項において、前記防錆層の内部には空孔が形成されていることを特徴とする耐候性鋳鉄。
【００４２】
【発明の効果】
本発明に係る耐候性鋳鉄によれば、多数の黒鉛が基地に分散しているため、鋳鉄特有の利点である鋳造性、振動減衰性、熱伝導性等の特性を得ることができる。更に本発明に係る耐候性鋳鉄によれば、表面に防錆層が形成されているため、耐食性を向上させることができ、耐候性鋳鉄の長寿命化や軽量化を図ることができる。
【００４３】
本発明に係る耐候性鋳鉄の製造方法によれば、上記したように鋳鉄特有の利点である鋳造性、振動減衰性、熱伝導性等の特性を有すると共に、耐食性を向上させることができ、長寿命化や軽量化を図ることができる耐候性鋳鉄を製造することができる。
【図面の簡単な説明】
【図１】比較例１，２、各実施例および各参考例に係る試験結果を示すグラフである。
【図２】熱処理時間を変えたときにおける実施例１、実施例２、参考例１に係る試験結果を示すグラフである。
【図３】光学顕微鏡で観察した表面組織を示す写真図である。
【図４】光学顕微鏡で観察した表面組織を示す写真図である。
【図５】ブレーキ装置のディスクロータに適用した適用例を示す斜視図である。
【符号の説明】
図中、１００はディスクロータ、１１０,２１０は防錆層を示す。[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a weather-resistant cast iron and a method for producing the same.
[0002]
[Prior art]
  In Patent Document 1, C: 0.6 to 4.0%, V: 4 to 15%, Cr: 13 to 30%, Ni: 4 to 15%, Si: 0.2 to 4.% by weight. 5%, Mn: 0.2 to 1.5%, P: 0.01 to 0.15%, S: 0.01 to 0.05%, and mainly covalently granular or Stainless steel spherical carbide cast iron obtained by crystallizing spherical V-C carbide is disclosed. According to this, since it is contained in a large amount of Cr: 13-30% and Ni: 4-15%, the corrosion resistance can be improved by the dense chromium-based passive film formed on the surface. .
[0003]
  In Patent Document 2, by weight ratio, C: 0.6 to 6.5%, V: 4 to 15%, Cr: 13 to 30%, Ni: 4 to 15%, Si: 0.2 to 3. 0%, Mn: 0.2-1.0%, P: 0.01-0.15%, S: 0.01-0.05% A tough high-carbon vanadium cementite-based alloy cast iron obtained by crystallizing spherical VC-based carbides and Fe-Cr-based carbides is disclosed. According to this, since it is contained in a large amount of Cr: 13-30% and Ni: 4-15%, the corrosion resistance can be improved by the dense chromium-based passive film formed on the surface. .
[0004]
[Patent Document 1]
  JP 2000-313934 A
[Patent Document 2]
  Japanese Patent Laid-Open No. 11-124651
[0005]
[Problems to be solved by the invention]
  The cast iron according to the above publication contains a large amount of 13 to 30% Cr and 4 to 15% Ni, and the corrosion resistance is improved, but the cost is increased. In addition, the amount of carbide is excessively large, and the toughness is not sufficient, so that it is not a cast iron product. Furthermore, the castability, which is an advantage unique to cast iron, is lowered, and is not suitable for the production of complex shaped products, thin-walled products and the like. In addition, since carbon is not generated as graphite but as carbide, vibration damping and thermal conductivity, which are advantages unique to cast iron, cannot be expected.
[0006]
  The present invention has been made in view of the above circumstances, and provides a weather-resistant cast iron capable of improving the corrosion resistance while obtaining characteristics such as castability and vibration damping, which are unique advantages of cast iron, and a method for producing the same The challenge is to do.
[0007]
[Means for Solving the Problems]
  The present inventor has been diligently developing weatherproof cast iron. And this inventor contains 3 types of nickel: 0.5-4.3%, copper: 0.1-1.5%, molybdenum: 0.05-1.5% by weight ratio.Mud castingWith iron compositionFormed of flake graphite cast iron or spheroidal graphite cast ironIf it is weather-resistant cast iron, the Fe₃O₄It was found that it was easy to produce a rust-preventing layer mainly composed of black rust, and it was confirmed that corrosion resistance could be improved while obtaining characteristics such as castability and vibration damping, which are advantages unique to cast iron. We have developed a weather-resistant cast iron according to the invention. In the present specification, “%” means “% by weight” unless otherwise specified.
[0008]
  In addition, the inventor includes three kinds of nickel: 0.5 to 4.3%, copper: 0.1 to 1.5%, and molybdenum: 0.05 to 1.5% by weight.Mud castingWith iron compositionFormed of flake graphite cast iron or spheroidal graphite cast ironIf the cast iron body is heated to a temperature range of 500 to 1200 ° C. in an oxygen-containing atmosphere and a heat treatment step is performed to form a rust prevention layer mainly composed of black rust on the surface of the cast iron body, the cast iron body On the surface of Fe₃O₄That it can easily generate a rust-preventing layer mainly composed of black rust, and confirmed that it can improve the corrosion resistance while obtaining characteristics such as castability and vibration damping, which are unique advantages of cast iron. The manufacturing method of the weather-resistant cast iron based on this invention was developed.
[0009]
  Aspect 1The weather-resistant cast iron according to the present invention includes three kinds of nickel: 0.5 to 4.3%, copper: 0.1 to 1.5%, and molybdenum: 0.05 to 1.5% by weight ratio.Along with carbon: 2.5-4.3 %, Silicon: 1.7-3.0%, manganese: 0.02-2.0%, phosphorus: 0.9% or less, sulfur: 0.9% or less, the balance being inevitable impurities and iron Formed of flake graphite cast iron withA cast iron body,
  It is comprised by the rust prevention layer which mainly has the black rust formed in the surface of the said cast iron main body.
  The weather-resistant cast iron according to aspect 2 includes three kinds of nickel: 0.5 to 4.3%, copper: 0.1 to 1.5%, and molybdenum: 0.05 to 1.5% by weight ratio. In addition, carbon: 3.2 to 4.3%, silicon: 1.5 to 3.5%, manganese: 0.02 to 2.0%, phosphorus: 0.9% or less, sulfur: 0.9% or less Magnesium: 0.90% or less, a cast iron body formed of spheroidal graphite cast iron having a cast iron composition consisting of inevitable impurities and iron, and
It is comprised by the rust prevention layer which mainly has the black rust formed in the surface of the said cast iron main body.
[0010]
  The antirust layer is a layer mainly composed of black rust formed on the surface of the cast iron body. Black rust is iron trioxide (Fe₃O₄System: magnetite) and it is easy to form a dense film. According to the weather resistant cast iron according to the present invention, the corrosion resistance is improved by the rust preventive layer.
[0011]
  Aspect 3The manufacturing method of the weather-resistant cast iron according to the present invention includes three types of nickel: 0.5 to 4.3%, copper: 0.1 to 1.5%, and molybdenum: 0.05 to 1.5% by weight ratio.In addition, carbon: 2.5-4.3%, silicon: 1.7-3.0%, manganese: 0.02-2.0%, phosphorus: 0.9% or less, sulfur: 0.9% or less , The balance is formed of flake graphite cast iron with cast iron composition consisting of inevitable impurities and ironPreparing a cast iron body,
  The cast iron body is heated to a temperature range of 500 to 1200 ° C. in an atmosphere containing oxygen, and a heat treatment step is performed to form a rust prevention layer mainly composed of black rust on the surface of the cast iron body. It is.
  The production method of the weather-resistant cast iron according to the aspect 4 is 3 by weight ratio of nickel: 0.5 to 4.3%, copper: 0.1 to 1.5%, molybdenum: 0.05 to 1.5%. Including seeds, carbon: 3.2 to 4.3%, silicon: 1.5 to 3.5%, manganese: 0.02 to 2.0%, phosphorus: 0.9% or less, sulfur: 0.0. 9% or less, magnesium: 0.90% or less, a step of preparing a cast iron body formed of spheroidal graphite cast iron having a cast iron composition of inevitable impurities and iron,
The cast iron body is heated to a temperature range of 500 to 1200 ° C. in an atmosphere containing oxygen, and a heat treatment step is performed to form a rust prevention layer mainly composed of black rust on the surface of the cast iron body. It is.
[0012]
  According to the method for producing weatherable cast iron according to the present invention, it is possible to form a weatherproof cast iron whose corrosion resistance is improved by the rust preventive layer.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
  The cast iron body according to the present invention is an iron-carbon based alloy containing three types of nickel: 0.5 to 4.3%, copper: 0.1 to 1.5%, and molybdenum: 0.05 to 1.5%. Has a cast iron composition.
[0014]
  Nickel is an element effective for rust prevention and corrosion resistance even when added alone, and is effective in producing black rust, but if it is too little, the effect is small, and if it is too much, the ratio of martensite in the matrix of the cast iron body Increases the machinability and increases the cost. For this reason, it is set as 0.5 to 4.3% as nickel. In particular, it can be 0.6 to 4.0%, 0.7 to 3.9%, 0.9 to 3.9%, especially 0.8 to 3.5%.
[0015]
  Copper is an element effective for rust prevention and corrosion resistance even when added alone, and is effective in producing black rust.However, if it is too little, its effect is small, and if it is too much, the matrix of the cast iron body is hardened and covered. Reduces machinability and induces cost increase. For this reason, it is 0.1 to 1.5% as copper. In particular, it can be 0.15 to 1.5%, 0.2 to 1.5%, 0.2 to 1.2%, 0.3 to 0.9%, 0.3 to 0.8 %.
[0016]
  Molybdenum is said to have the effect of suppressing the passage of chlorine ions through the rust preventive layer. If the amount is too small, the effect is small. If the amount is too large, the ratio of martensite increases in the matrix of the cast iron body, the ratio of carbide increases, and the machinability is lowered and the cost is increased. For this reason, it is 0.05 to 1.5% as molybdenum. In particular, the content may be 0.1 to 1.0%, 0.2 to 1.0%, particularly 0.2 to 0.8%.
[0017]
  According to the weather-resistant cast iron according to the present invention, a rust prevention layer mainly composed of black rust is formed on the surface of the cast iron body. The average thickness of the anticorrosive layer is 0.05 to 1.2 mm, 0.07 to 1.0 mm, and 0.1 to 0.8 mm, although it varies depending on the degree of heat treatment, the use of weatherproof cast iron, and the like. Can do. However, it is not limited to these. According to the weather-resistant cast iron according to the present invention, the antirust layer may be formed on the entire surface of the weather-resistant cast iron, or may be formed only on the necessary part. When the weather-resistant cast iron has a friction sliding surface, the anti-rust layer can be prevented from being formed on the friction sliding surface by masking or cutting. The matrix of the cast iron body is not particularly limited, and examples thereof include pearlite, ferrite, pearlite-ferrite, martensite, and bainite.
[0018]
  According to a preferred embodiment, ferrite is mainly used on the surface side of the cast iron body.OrganizationA ferrite rich layer which is a decarburized layer included as a rust preventive layer is formed on the outside of the ferrite rich layer. Since the ferrite rich layer contains a large amount of ferrite, it is generally more ductile than the inside of the cast iron body of weatherproof cast iron. The average thickness of the ferrite-rich layer can be selected as appropriate, but is generally 10 to 5000 μm, particularly 50 to 1000 μm. However, it is not limited to this. As the cast iron body, flake graphite cast iron in which flake graphite is dispersed or spheroidal graphite cast iron in which spheroidal graphite is dispersed can be employed.
[0019]
  When the cast iron body is flake graphite cast iron, carbon: 2.5-4.3%, silicon: 1.7-3.0%, manganese: 0.02-2.0%, phosphorus: 0.9 % Or less, sulfur: 0.9% or less,The restInevitable impuritiesAnd made of ironIt can be a cast iron composition. In this case, carbon is effective for forming an appropriate amount of graphite and for strengthening the matrix by solid solution in the matrix. For this reason, the carbon content can be 2.5 to 4.3%, 2.7 to 3.9%, particularly 3.1 to 3.8%.
[0020]
  Silicon affects the carbon equivalent, forms an appropriate amount of graphite, and is effective in strengthening the matrix by dissolving in the matrix. For this reason, as silicon, it can be 1.7-3.0%, especially 1.8-2.8%, 1.9-2.7%. Manganese is effective in strengthening the matrix. Therefore, the manganese content can be 0.02 to 2.0%, particularly 0.1 to 1.5% and 0.2 to 1.5%. Phosphorus and sulfur are generally preferred to be small, but are cast iron, so they are blended from raw materials. Accordingly, phosphorus can be 0.9% or less, particularly 0.6% or less, and sulfur can be 0.9% or less, particularly 0.6% or less. When chromium is contained, carbides are excessive and chill tends to be easily formed. For this reason, chromium can be 0.9% or less, 0.7% or less, and particularly 0.5% or less.
[0021]
  According to a preferred form, the cast iron body can be spheroidal graphite cast iron. In this case, carbon: 3.2 to 4.3%, silicon: 1.5 to 3.5%, manganese: 0.02 to 2.0%, phosphorus: 0.9% or less, sulfur: 0.9% Magnesium: 0.90% or less, balance is inevitableAnd made of ironIt can be a cast iron composition. In this case, carbon is effective for forming an appropriate amount of graphite and for strengthening the matrix by solid solution in the matrix. For this reason, as carbon, it can be set to 3.2 to 4.3%, especially 3.3 to 4.3%, 3.4 to 3.9%. Silicon affects the carbon equivalent, forms an appropriate amount of graphite, and is effective in strengthening the matrix by dissolving in the matrix. For this reason, as silicon, it can be 1.5-3.5%, especially 1.7-3.3%, 1.8-3.0%. Manganese is effective in strengthening the matrix. Manganese can be 0.02 to 2.0%, particularly 0.05 to 1.5%, and 0.06 to 1.2%. Phosphorus and sulfur are generally preferred to be small, but are cast iron, so they are blended from raw materials. Phosphorus can be 0.9% or less, particularly 0.6% or less, and sulfur can be 0.9% or less, particularly 0.6% or less. Magnesium is necessary for spheronization. Magnesium may be 0.70% or less and 0.10% or less. When chromium is contained, carbides are excessive and chill is easily formed. For this reason, chromium can be 0.9% or less, 0.7% or less, and particularly 0.5% or less.
[0022]
  Aspect 3According to the method for producing weatherable cast iron according to the present invention, the weight ratio is 3 for nickel: 0.5 to 4.3%, copper: 0.1 to 1.5%, molybdenum: 0.05 to 1.5%. Including speciesIn addition, carbon: 2.5-4.3%, silicon: 1.7-3.0%, manganese: 0.02-2.0%, phosphorus: 0.9% or less, sulfur: 0.9% or less The balance is made of flake graphite cast iron with cast iron composition consisting of inevitable impurities and ironPrepare a cast iron body.
  Moreover, according to the manufacturing method of the weather-resistant cast iron which concerns on the aspect 4, nickel: 0.5-4.3%, copper: 0.1-1.5%, molybdenum: 0.05-1.5 by weight ratio. %: Carbon: 3.2 to 4.3%, silicon: 1.5 to 3.5%, manganese: 0.02 to 2.0%, phosphorus: 0.9% or less, sulfur Prepared is a cast iron main body formed of spheroidal graphite cast iron having 0.9% or less, magnesium: 0.90% or less, and the balance having inevitable impurities and iron cast iron composition.
  Next, in the manufacturing method according to aspects 3 and 4,A heat treatment process is performed, and the cast iron body is heated to a temperature range of 500 to 1200 ° C. in an oxygen-containing atmosphere to form a rust prevention layer mainly composed of black rust on the surface of the cast iron body. If the temperature of the heat treatment is excessively low, the formation of the rust prevention layer is not stable, and it takes time to form the rust prevention layer. If the temperature of the heat treatment is excessively high, the cast iron body is likely to be deformed, and the scale formed on the outer side of the rust prevention layer together with the rust prevention layer is likely to be excessive. Considering these, the temperature of the heat treatment is set to 500 to 1200 ° C. In particular, 700 to 1100 ° C., particularly 800 to 1000 ° C. can be employed. The heat treatment temperature is A₁The temperature is preferably equal to or higher than the transformation point. Heat treatment temperature is A₁If the temperature is equal to or higher than the transformation point, A₁Transformation by passing through transformation points can be used.
[0023]
  During the heat treatment, decarburization on the surface of the cast iron body can be promoted to reduce or remove graphite on the surface of the cast iron body. If the graphite on the surface of the cast iron body is reduced or removed in this way, a rust-proof layer can be formed on the graphite trace, and the coverage with the rust-proof layer can be improved. If the surface of the cast iron body is decarburized as described above, the ductile ferrite is mainly placed inside the rust prevention layer on the surface side of the cast iron body.OrganizationA ferrite rich layer can be formed. The average thickness of the ferrite-rich layer may be 10 to 5000 μm, 20 to 3000 μm, 50 to 1000 μm, etc., although it varies depending on the degree of heat treatment, etc., but is not limited thereto. In the ferrite rich layer, the area ratio of ferrite can be generally 30% or more, 40% or more, 50% or more, or 60% or more.
[0024]
  An atmosphere containing oxygen is employed as the atmosphere for the heat treatment. In this case, an air atmosphere or a reduced-pressure oxygen-containing atmosphere can be employed. In some cases, an oxygen-containing atmosphere having a pressure higher than atmospheric pressure can be employed. The oxygen concentration in the heat treatment atmosphere may be higher or lower than the oxygen concentration in the atmosphere. The heat treatment time is a time during which a good rust preventive layer can be formed, and differs depending on the oxygen concentration in the heat treatment atmosphere, the heat treatment temperature, the size of the cast iron body, and the like. When the oxygen concentration in the heat treatment atmosphere is low and the heat treatment temperature is low, the heat treatment time is generally longer. When the oxygen concentration in the heat treatment atmosphere is high and the heat treatment temperature is high, the heat treatment time is generally shortened. In consideration of these, a heat treatment time of 10 minutes to 100 hours, particularly 20 minutes to 30 hours, and 1 hour to 10 hours can be employed. If the heat treatment time is excessively short, a sufficient rust preventive layer cannot be obtained.
[0025]
  According to the method of the present invention, a peelable scale may be formed on the cast iron body by the heat treatment process. In this case, it is possible to adopt a form in which the scale generated on the cast iron body is removed while performing a blasting process such as a sand blasting process on the cast iron body after the heat treatment and leaving the rust preventive layer on the surface of the cast iron body. Since the rust prevention layer has high adhesion to the base material of the cast iron body, if the blast treatment is not excessive, even if the scale generated on the cast iron body is removed, the rust prevention layer may remain on the surface of the cast iron body. it can.
[0026]
【Example】
  Examples of the present invention will be described below together with comparative examples. The test pieces according to Example 1, Example 2, Reference Example 1, Reference Example 2, and Comparative Example 1 are made of flake graphite cast iron. The test pieces according to Example 5, Reference Example 3, and Comparative Example 2 are formed of spheroidal graphite cast iron. The test pieces according to Examples 7 to 10 are made of flake graphite cast iron. The size of the test piece was 50 mm × 30 mm × 5 mm. The composition of each test piece is shown in Table 1. In addition, Example 3, Example 4, and Example 6 are missing numbers.
[0027]
[Table 1]

[0028]
  The test pieces according to Example 1, Example 2, Reference Example 1, Reference Example 2, and Examples 7 to 10 are, by weight ratio, carbon: 2.5 to 4.3%, silicon: 1.7 to It has a cast iron composition containing 3.0%, manganese: 0.02-2.0%, phosphorus: 0.9% or less, sulfur: 0.9% or less, nickel: 0.5-4.3%, copper : 0.1-1.5% and molybdenum: 0.05-1.5%. The test pieces according to Example 5 and Reference Example 3 were carbon: 3.2 to 4.3%, silicon: 1.5 to 3.5%, manganese: 0.02 to 2.0%, phosphorus: 0.00. It has a cast iron composition containing 9% or less, sulfur: 0.9% or less, magnesium: 0.90% or less, nickel: 0.5-4.3%, copper: 0.1-1.5%, molybdenum: Three types of 0.05-1.5% are included. The cast iron composition of each example does not contain chromium as an active element and is less than 0.1%.
[0029]
  The test piece according to Comparative Example 1 and the test piece according to Comparative Example 2 do not actively contain nickel, copper, and molybdenum.
[0030]
  Each test piece was charged into a heat treatment furnace, and a heat treatment step was performed in which the test pieces were heated and held in a temperature range of 930 ° C. for 5 hours in an air atmosphere (atmosphere containing oxygen). After the heat treatment, the test piece was taken out from the heat treatment furnace and cooled by furnace cooling.
[0031]
  When each test piece according to the example is subjected to sandblasting and the oxide film, which is a scale formed on the surface of each test piece according to the example, is removed, a black rust prevention layer mainly composed of black rust is formed. It was. The average thickness of the rust preventive layer was about 0.2 to 0.4 mm. This rust preventive layer had high adhesion to the base material of the test piece.
[0032]
  Each test piece according to the comparative example was subjected to sand blasting treatment, and when the oxide film, which was a scale formed on the surface, was removed, the black rust prevention layer mainly composed of black rust as in the example was hardly formed. It was.
[0033]
  A corrosion resistance test was performed on each test piece subjected to the sandblast treatment. In this case, the salt spray test method (JIS Z2371) was performed for 240 hours. That is, salt water is sprayed on the surface of the test piece with a spray nozzle to cause red rust (Fe₂O₃) Was generated. Since red rust has low adhesion to the base material of the test piece, it has the property of easily falling off from the base material. After spraying with salt water, red rust generated on the test piece was removed by sandblasting. Although the red rust is removed by the sandblast treatment, the black rust preventive layer is not removed. And the weight loss of the test piece before and after salt water spraying was calculated | required, and this was made into corrosion weight loss (%). The greater the corrosion weight loss, the worse the corrosion resistance, and the smaller the corrosion weight loss, the better the corrosion resistance.
[0034]
  The test results are shown in FIG. As shown in FIG. 1, in Comparative Example 1 formed of flake graphite cast iron and Comparative Example 2 formed of spheroidal graphite cast iron, the black rust preventive layer is not formed, and the weight loss by corrosion is weight. The ratio exceeded 1.2%, which was quite large and the corrosion resistance was not good.
[0035]
  On the other hand, about Example 1 and Example 2 formed with flake graphite cast iron containing three kinds, nickel, copper, and molybdenum, a rust prevention layer is good and corrosion weight loss is 0. It was 4% or less, and the corrosion resistance was excellent. In Reference Example 1 formed of flake graphite cast iron containing nickel and molybdenum, the rust preventive layer was good, the corrosion weight loss was 0.8% or less, and the corrosion resistance was good. In Reference Example 2 formed of flake graphite cast iron containing copper and nickel, the rust prevention layer was good, the corrosion weight loss was 0.8% or less, and the corrosion resistance was good.
[0036]
  Moreover, about Example 5 formed with the spheroidal graphite cast iron containing nickel, copper, and molybdenum, the rust preventive layer was good, the corrosion weight loss was 0.4% or less, and the corrosion resistance was excellent. In Reference Example 3 formed of spheroidal graphite cast iron containing nickel and copper, the rust preventive layer was good, the corrosion weight loss was 0.6% or less, and the corrosion resistance was good.
[0037]
  For Examples 7 to 10 formed of flake graphite cast iron containing nickel, copper and molybdenum, the rust preventive layer is good, the corrosion weight loss is as small as 0.2% or less, and the corrosion resistance. Was excellent. From the above test results, it can be seen that the rust preventive layer according to the present example is effective in corrosion resistance.
[0038]
  FIG. 2 shows that the test pieces according to Example 1, Example 2, and Reference Example 1 were not heat-treated, heat-treated at 930 ° C. for 2 hours, and heat-treated at 930 ° C. for 5 hours. Shown in comparison with the case. As shown in FIG. 2, even in Example 1, Example 2, and Reference Example 1, when the heat treatment for forming the rust preventive layer was not performed, the corrosion weight loss was considerably large and the corrosion resistance was poor. However, heat treatment reduces the corrosion weight loss and improves the corrosion resistance. In particular, it can be seen that the corrosion resistance is improved because the corrosion weight loss decreases as the heat treatment time becomes longer.
[0039]
  About Example 2, the structure of the surface part of the test piece was confirmed with an optical microscope. This is shown in FIG. 3 (magnification 100 times) and FIG. 4 (magnification 200 times). The structures shown in FIGS. 3 and 4 are corroded with a nightite etchant. As shown in FIGS. 3 and 4, in the test piece, a large number of flake graphite was dispersed in the matrix of the cast iron main body mainly composed of pearlite. And the graphite on the surface side of the test piece is decarburized, and ferrite is mainly used inside the rust prevention layer on the surface side of the test piece.OrganizationAs a result, a ferrite rich layer (average thickness: 200 to 500 μm), which is a decarburized layer, was formed. In the ferrite rich layer, the area ratio of ferrite was 50% or more. The rust preventive layer was formed on the outer surface side of the ferrite rich layer. According to FIG. 3 and FIG. 4, the ferrite in the ferrite rich layer is often relatively irregular. It is inferred that the decarburization of graphite during the heat treatment contributes. It is inferred that the deformed shape of ferrite can contribute to improving the adhesion between the rust-proof layer and ferrite, and can contribute to improving the adhesion of the rust-proof layer to the cast iron body. Voids that are pores were formed in the rust prevention layer. This is probably due to the decarburization of graphite during the heat treatment. Voids can be expected to improve oil content.
[0040]
  (Application example)
  FIG. 5 shows a brake device having a disc rotor 100 and a caliper 200. In this case, it is applied to the disc rotor 100 and the caliper 200. The disk rotor 100 is formed of flake graphite cast iron in which flake graphite is dispersed, and the caliper 200 is formed of spheroidal graphite cast iron in which spheroidal graphite is dispersed. Rust prevention layers 110 and 210 mainly composed of black rust formed as described above are formed on the outer wall surface. According to the disk rotor 100, since many pieces of flake graphite are dispersed in the base, it is possible to obtain characteristics such as castability, vibration damping properties, and thermal conductivity, which are advantages unique to cast iron. Further, since the rust prevention layer 110 is formed on the surface, the corrosion resistance can be improved, and the life of the disk rotor 100 can be extended. In addition, the plurality of fin portions 120 of the disk rotor 100 are usually set to be thick at the design stage in consideration of corrosion resistance. However, these fin portions 120 have a rust prevention layer 110 and are resistant to corrosion. Since it is improved, the fin portion 120 can be made thin, and the weight of the disk rotor 100 can be reduced. On the frictional sliding surface of the disk rotor 100, the rust preventive layer is removed by cutting. The present invention can be applied not only to the disc rotor 100 and the caliper 200 but also to cast iron parts such as a brake shoe, a cylinder block, a cylinder cover, a caliper support, a bearing cap, a differential case, and a differential carrier.
[0041]
  (Others) In addition, the present invention is not limited to the above-described embodiments, and can be appropriately modified and implemented without departing from the scope of the invention. The following technical idea can also be grasped from the above description.
(Additional Item 1) Iron-carbon system including three kinds of nickel: 0.5 to 4.3%, copper: 0.1 to 1.5%, molybdenum: 0.05 to 1.5% by weight ratio A weather-resistant cast iron having a cast iron composition and graphite dispersed therein, and heated to a temperature range of 500 to 1200 ° C. in an oxygen-containing atmosphere, whereby a rust preventive layer mainly composed of black rust is formed on the surface. Weatherproof cast iron characterized by being formed.
(Additional Item 2) A weather-resistant cast iron according to any one of the claims, wherein pores are formed inside the antirust layer.
[0042]
【The invention's effect】
  According to the weather-resistant cast iron according to the present invention, since many graphites are dispersed in the base, it is possible to obtain characteristics such as castability, vibration damping properties, and thermal conductivity, which are advantages unique to cast iron. Furthermore, according to the weather-resistant cast iron according to the present invention, since the rust-proof layer is formed on the surface, the corrosion resistance can be improved, and the life and weight of the weather-resistant cast iron can be increased.
[0043]
  According to the method for producing weatherable cast iron according to the present invention, as described above, it has characteristics such as castability, vibration damping, and thermal conductivity, which are advantages unique to cast iron, and can improve corrosion resistance, It is possible to produce a weather-resistant cast iron that can be reduced in life and weight.
[Brief description of the drawings]
FIG. 1 is a graph showing test results according to comparative examples 1 and 2, each example, and each reference example.
FIG. 2 is a graph showing test results according to Example 1, Example 2, and Reference Example 1 when the heat treatment time is changed.
FIG. 3 is a photograph showing a surface structure observed with an optical microscope.
FIG. 4 is a photograph showing a surface structure observed with an optical microscope.
FIG. 5 is a perspective view showing an application example applied to a disc rotor of a brake device.
[Explanation of symbols]
  In the figure, 100 is a disk rotor, and 110 and 210 are rust prevention layers.

Claims (7)

In a weight ratio, nickel: 0.5 to 4.3%, copper: 0.1 to 1.5%, molybdenum: 0.05 to 1.5%, and carbon: 2.5 to 4 .3%, Silicon: 1.7-3.0%, Manganese: 0.02-2.0%, Phosphorus: 0.9% or less, Sulfur: 0.9% or less, the balance being inevitable impurities and iron A cast iron body formed of flake graphite cast iron having a cast iron composition;
A weatherproof cast iron comprising a rust prevention layer mainly composed of black rust formed on the surface of the cast iron body. It contains three types of nickel: 0.5 to 4.3%, copper: 0.1 to 1.5%, molybdenum: 0.05 to 1.5%, and carbon: 3.2 to 4 by weight ratio. .3%, silicon: 1.5-3.5%, manganese: 0.02-2.0%, phosphorus: 0.9% or less, sulfur: 0.9% or less, magnesium: 0.90% or less, A cast iron body formed of spheroidal graphite cast iron having a cast iron composition of which the balance is inevitable impurities and iron;
A weatherproof cast iron comprising a rust prevention layer mainly composed of black rust formed on the surface of the cast iron body. The ferrite rich layer containing ferrite as a main structure is formed on the surface side of the cast iron main body according to claim 1 or 2, and the rust prevention layer is formed outside the ferrite rich layer. Weatherproof cast iron. In a weight ratio, nickel: 0.5 to 4.3%, copper: 0.1 to 1.5%, molybdenum: 0.05 to 1.5%, and carbon: 2.5 to 4 .3%, Silicon: 1.7-3.0%, Manganese: 0.02-2.0%, Phosphorus: 0.9% or less, Sulfur: 0.9% or less, the balance being inevitable impurities and iron Preparing a cast iron body formed of flake graphite cast iron having a cast iron composition;
A heat treatment step of heating the cast iron main body to a temperature range of 500 to 1200 ° C. in an oxygen-containing atmosphere and forming a rust preventive layer mainly composed of black rust on the surface of the cast iron main body. Method for producing porous cast iron. It contains three types of nickel: 0.5 to 4.3%, copper: 0.1 to 1.5%, molybdenum: 0.05 to 1.5%, and carbon: 3.2 to 4 by weight ratio. .3%, silicon: 1.5-3.5%, manganese: 0.02-2.0%, phosphorus: 0.9% or less, sulfur: 0.9% or less, magnesium: 0.90% or less, Preparing a cast iron body formed of spheroidal graphite cast iron having a cast iron composition consisting of inevitable impurities and iron, and
A heat treatment step of heating the cast iron main body to a temperature range of 500 to 1200 ° C. in an oxygen-containing atmosphere and forming a rust preventive layer mainly composed of black rust on the surface of the cast iron main body. Method for producing porous cast iron. In Claim 4 or 5, in the case of heat processing, the graphite of the surface of the said cast iron main body is decarburized, and the ferrite rich layer which contains a ferrite as a main structure is formed inside the antirust layer in the surface side of the said cast iron main body. A method for producing a weather-resistant cast iron.   7. The outer side of the rust prevention layer of the cast iron body according to claim 4, wherein a blast treatment is performed after the heat treatment step so that the rust prevention layer remains on the surface of the cast iron body. A method for producing a weather-resistant cast iron, characterized by removing the scale formed on the surface.

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