JP2007000881A - Method for producing ductile cast iron - Google Patents

Method for producing ductile cast iron Download PDF

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JP2007000881A
JP2007000881A JP2005181431A JP2005181431A JP2007000881A JP 2007000881 A JP2007000881 A JP 2007000881A JP 2005181431 A JP2005181431 A JP 2005181431A JP 2005181431 A JP2005181431 A JP 2005181431A JP 2007000881 A JP2007000881 A JP 2007000881A
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absorption energy
cast iron
pearlite
impact absorption
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Yoshiaki Yamamoto
義昭 山本
Keiji Maeda
圭史 前田
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Kitagawa Iron Works Co Ltd
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Kitagawa Iron Works Co Ltd
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  • Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing ductile cast iron (spheroidal graphite cast iron) having excellent impact resistance, particularly, at low temperature without performing heat treatment. <P>SOLUTION: In the method for producing ductile cast iron, the content of C is controlled to 3.5 to 3.7 wt.%, the content of Si is controlled to 2.3 to 2.5 wt.%, and the content of Mn is controlled to ≤0.25 wt.%, and the ratio of pearlite is controlled to ≤20%. Further, the addition of an inoculum is performed several times before tapping. In its compositional structure, the number of graphite grains with a diameter of ≥5 μm is controlled to ≥450 pieces/mm<SP>2</SP>. In the blending ratio of the material, pig iron is used by 40%. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

本発明は、低温での耐衝撃性に優れたダクタイル鋳鉄(球状黒鉛鋳鉄)の製造方法に関するものである。   The present invention relates to a method for producing ductile cast iron (spheroidal graphite cast iron) having excellent impact resistance at low temperatures.

従来より、優れた材料特性を示すダクタイル鋳鉄は、ナックルなどの自動車用部品の材料として多く使用されている。
自動車用の材料は、野外の過酷な気象条件下で使用されるので、厳格な材質基準が設定されている。それは、耐力・引張り強さ・伸び・硬さなど多岐にわたり、特に低温環境下での耐衝撃性が強く求められている。
例えば、−40°Cでのシャルピー衝撃試験において、衝撃吸収エネルギが12J(ジュール)以上に求められることがある。
表1に、要求される材質基準の一覧を示す。
Conventionally, ductile cast iron showing excellent material properties has been widely used as a material for automotive parts such as knuckles.
Since materials for automobiles are used under severe weather conditions in the field, strict material standards are set. It has a wide range of proof stress, tensile strength, elongation, hardness, etc., and impact resistance particularly in a low temperature environment is strongly demanded.
For example, in a Charpy impact test at −40 ° C., impact absorption energy may be required to be 12 J (joules) or more.
Table 1 shows a list of required material standards.

Figure 2007000881
Figure 2007000881

本出願人はこれらの要求に応える為、一般的に用いられる表2に示す組成成分のダクタイル鋳鉄を使って各種の実験を行なった。その結果を表3に示す。   In order to meet these demands, the present applicant conducted various experiments using commonly used ductile cast iron having the composition components shown in Table 2. The results are shown in Table 3.

Figure 2007000881
Figure 2007000881

Figure 2007000881
Figure 2007000881

この結果によると、熱処理を行なわない(鋳放し)と要求される材質性能が得られず、熱処理(焼鈍)を行なうことで要求される材質性能が得られることが解かった。   According to this result, it was found that the required material performance cannot be obtained unless heat treatment is performed (as cast), and the required material performance is obtained by performing heat treatment (annealing).

しかしながら、自動車用部品、特にナックルなどの形状が複雑な部品においては、熱処理を部品へ均一に行うには熱管理において微妙なコントロールが困難であり、非常にデリケートな温度調整が必要となって、大変手間のかかる作業となる。
また、熱管理でのコントロールを誤り、材料品質にバラツキが発生すると、要求される材料性能が全て、或いはいくつかが満足できない恐れがある。
さらに、熱処理による変形が発生するため、部品の全てを寸法検査し、部品形状の異常を確認しなければならない。
However, in parts for automobiles, especially parts with complicated shapes such as knuckles, it is difficult to perform delicate control in heat management to perform heat treatment uniformly on the parts, and very delicate temperature adjustment is required, This is a laborious work.
In addition, if control in heat management is mistaken and variations occur in material quality, there is a possibility that all or some of the required material performance cannot be satisfied.
Furthermore, since deformation due to heat treatment occurs, all of the parts must be dimensionally inspected to check for an abnormality in the part shape.

本発明は、上記した従来の問題点を解決し、熱処理を行なうことなく、特に低温での耐衝撃性に優れたダクタイル鋳鉄の製造方法を提供することを目的としている。   An object of the present invention is to solve the above-mentioned conventional problems and to provide a method for producing ductile cast iron having excellent impact resistance particularly at low temperatures without performing heat treatment.

上記した目的を達成するために、本発明のダクタイル鋳鉄の製造方法は、C:3.5〜3.7重量%,Si:2.3〜2.5重量%,Mn:0.25重量%以下,を含有し、パーライト率を20%以下に調整することを要旨としている。
さらには、注湯前に接種材の添加を複数回実施すること、組成組織において直径5μm以上の黒鉛粒数を450個/mm以上に調整すること、材料配合率において、銑鉄を40%使用すること、を要旨としている。
In order to achieve the above-described object, the method for producing a ductile cast iron according to the present invention includes: C: 3.5 to 3.7 wt%, Si: 2.3 to 2.5 wt%, Mn: 0.25 wt% The gist is to adjust the pearlite ratio to 20% or less.
Furthermore, the inoculum is added a plurality of times before pouring, the number of graphite grains having a diameter of 5 μm or more is adjusted to 450 pieces / mm 2 or more in the composition structure, and 40% of pig iron is used in the material mixture ratio. This is the gist.

本発明を実施することにより、低温での耐衝撃性に優れたダクタイル鋳鉄の製造に際して、熱処理を行なう必要が無い。そのため、部品が変形を起こすことなく、安定した品質の部品を安定して供給することが可能となる。また、変形をチェックする検査をする必要が無くなり、作業工程の短縮となる。
さらには、熱処理の際に部品へ付着するスケールを取り除くために行っていたショットでの付着除去工程を行なわなくてもよくなり、工場内での部品の移動を含めた作業時間の短縮、及び設備コストの削減が実現できる。
By carrying out the present invention, it is not necessary to perform heat treatment in the production of ductile cast iron having excellent impact resistance at low temperatures. For this reason, it is possible to stably supply components of stable quality without causing deformation of the components. Further, it is not necessary to perform an inspection for checking the deformation, and the work process is shortened.
Furthermore, it is not necessary to perform the adhesion removal process with the shot that was performed to remove the scale adhering to the parts during the heat treatment, shortening the work time including the movement of the parts in the factory, and the equipment Cost reduction can be realized.

鋳鉄の組成成分において、一般にSiの含有量が多くなると、低温下での衝撃吸収エネルギは大幅に減少することが知られている。
図7で示すグラフでは、Si含有量の違いにおける温度と衝撃吸収エネルギとの相関図を示している。
図7(A)では、Si含有量2.95%の材料における温度と衝撃吸収エネルギとの相関図を示し、図7(B)では、Si含有量2.05%の材料における温度と衝撃吸収エネルギとの相関図を示している。(文献 BCIRA REPORT 1521より)
図7(A)と、図7(B)を比較して解かるように、Siの含有量が多くなると、温度と衝撃吸収エネルギとの相関曲線の変曲点が高温側(図7中右側)へ移動しており、特に−40°C付近での衝撃吸収エネルギの値は大きく異なるものである。
そこで本出願人は、Siの含有量をできるだけ小さくし、低温下での衝撃吸収エネルギを大きくするために、他の要因との相関関係を確認する実験を行った。
It is known that, in the composition component of cast iron, generally, when the Si content is increased, the impact absorption energy at a low temperature is greatly reduced.
The graph shown in FIG. 7 shows a correlation diagram between temperature and impact absorption energy in the difference in Si content.
FIG. 7A shows a correlation diagram between temperature and shock absorption energy in a material having a Si content of 2.95%, and FIG. 7B shows temperature and shock absorption in a material having a Si content of 2.05%. A correlation diagram with energy is shown. (From document BCIRA REPORT 1521)
As can be seen by comparing FIG. 7A and FIG. 7B, when the Si content increases, the inflection point of the correlation curve between temperature and shock absorption energy becomes higher (right side in FIG. 7). In particular, the value of impact absorption energy in the vicinity of −40 ° C. is greatly different.
Therefore, the present applicant conducted an experiment to confirm the correlation with other factors in order to reduce the Si content as much as possible and increase the impact absorption energy at low temperatures.

表4へ実験に用いたダクタイル鋳鉄の元の組成成分を示す。   Table 4 shows the original composition components of the ductile cast iron used in the experiment.

Figure 2007000881
Figure 2007000881

これらの材料を元にSi含有量及び、他の要因条件を変えた多種類の材料を用い、低温下での衝撃吸収エネルギと、他の要因との相関関係を確認した実験を行った。その実験結果を以下のグラフに示す。
図1は、−40°Cでの衝撃吸収エネルギと、Si含有量との相関図である。
図2は、パーライト率と、Si含有量との相関図である。
図3は、−40°Cでの衝撃吸収エネルギと、パーライト率との相関図である。
図4は、パーライト率と、Mn含有量との相関図である。
図5は、−40°Cで衝撃吸収エネルギと、Mn含有量との相関図である。
Based on these materials, various types of materials with different Si contents and other factor conditions were used, and experiments were conducted to confirm the correlation between impact absorption energy at low temperatures and other factors. The experimental results are shown in the following graph.
FIG. 1 is a correlation diagram between impact absorption energy at −40 ° C. and Si content.
FIG. 2 is a correlation diagram between the pearlite ratio and the Si content.
FIG. 3 is a correlation diagram between the impact absorption energy at −40 ° C. and the pearlite ratio.
FIG. 4 is a correlation diagram between the pearlite ratio and the Mn content.
FIG. 5 is a correlation diagram between impact absorption energy and Mn content at −40 ° C.

図1の−40°Cでの衝撃吸収エネルギと、Si含有量との相関関係のグラフでわかるように、Si含有量が2.4%の時に、−40°Cでの衝撃吸収エネルギは最も大きな値を示し、その前後でも高い値を示している。しかし、Siの含有量が2.4%前後の値から外れ、含有量がより大きくなる、或いは小さくなると、−40°Cでの衝撃吸収エネルギの値は小さくなることが解かる。
前記の通り、Siの含有量が多くなると、低温下での衝撃吸収エネルギは大幅に減少することはすでに知られている。したがって、Siの含有量が少なくなった際に低温下での衝撃吸収エネルギが小さくなることについて、他の要因を検討すべく実験を行った。
As can be seen from the graph of the correlation between the shock absorption energy at −40 ° C. in FIG. 1 and the Si content, the shock absorption energy at −40 ° C. is the highest when the Si content is 2.4%. A large value is shown, and a high value is shown before and after. However, it can be seen that when the Si content deviates from the value of around 2.4% and the content becomes larger or smaller, the value of the impact absorption energy at −40 ° C. becomes smaller.
As described above, it is already known that the impact absorption energy at a low temperature significantly decreases as the Si content increases. Therefore, an experiment was conducted to examine other factors about the fact that the impact absorption energy at low temperatures decreases when the Si content decreases.

図2のパーライト率と、Si含有量との相関関係のグラフでは、Siの含有量が小さくなるにつれて、パーライト率が大きくなることが解かる。
ここで、−40°Cでの衝撃吸収エネルギと、パーライト率との相関関係を調べると、図3の−40°Cでの衝撃吸収エネルギと、パーライト率との相関関係のグラフで示されるように、パーライト率が小さくなると−40°Cでの衝撃吸収エネルギの値が大きくなる。
したがって、Si含有量が小さくなると、パーライトが増え、そのため低温下での衝撃吸収エネルギが小さくなるものと考えられる。
In the graph of the correlation between the pearlite ratio and the Si content in FIG. 2, it can be seen that the pearlite ratio increases as the Si content decreases.
Here, when the correlation between the shock absorption energy at −40 ° C. and the pearlite ratio is examined, the correlation between the shock absorption energy at −40 ° C. and the pearlite ratio in FIG. 3 is shown. In addition, when the pearlite ratio decreases, the value of impact absorption energy at −40 ° C. increases.
Therefore, it is considered that when the Si content is reduced, pearlite is increased, and therefore, the impact absorption energy at a low temperature is reduced.

また、低温下での衝撃吸収エネルギの値と、パーライト率との相関関係からパーライトの発生を小さくすると、低温下での衝撃吸収エネルギが大きくなることが予想される。
そこで、パーライトの発生に関与する元素として知られるMnに注目し、パーライト率と、Mn含有量との相関関係を確認した。
図4は、パーライト率と、Mn含有量との相関関係をグラフにしたものである。図4のグラフに示す通り、Mnの含有量が小さくなるにつれて、パーライト率も小さくなっている。
In addition, it is expected that the impact absorption energy at a low temperature increases when the generation of pearlite is reduced from the correlation between the value of the impact absorption energy at a low temperature and the pearlite ratio.
Therefore, attention was paid to Mn known as an element involved in the generation of pearlite, and a correlation between the pearlite ratio and the Mn content was confirmed.
FIG. 4 is a graph showing the correlation between the pearlite ratio and the Mn content. As shown in the graph of FIG. 4, the pearlite ratio decreases as the Mn content decreases.

これにより、低温下での衝撃吸収エネルギの値とパーライト率との相関関係を鑑みると、Mn含有量を小さくすると、パーライトの発生が小さくなり、そのために低温下での衝撃吸収エネルギが大きくなるものと考えられる。
これを実証するための実験を行い、その結果を図5に示す。
図5は、−40°Cで衝撃吸収エネルギと、Mn含有量との相関図である。
図5の相関曲線で示すように、Mn含有量を小さくすると、−40°Cで衝撃吸収エネルギが大きくなっており、先の検証を裏付けることが解かった。
Thus, in view of the correlation between the value of impact absorption energy at low temperature and the pearlite ratio, the generation of pearlite is reduced when the Mn content is reduced, and therefore the impact absorption energy at low temperature is increased. it is conceivable that.
Experiments were performed to verify this, and the results are shown in FIG.
FIG. 5 is a correlation diagram between impact absorption energy and Mn content at −40 ° C.
As shown by the correlation curve in FIG. 5, when the Mn content is decreased, the impact absorption energy is increased at −40 ° C., which proves the previous verification.

以上述べたように、本出願人は、低温下での衝撃吸収エネルギの値に因果関係をもつ3つの要因である、Si含有量と、Mn含有量と、パーライト率を管理することで、低温下での衝撃吸収エネルギの値が得られることの実証を行なった。
前記実験の結果から、Si含有量と、Mn含有量と、パーライト率の数値を各々以下のようにすれば、−40°Cでのシャルピー衝撃試験において、衝撃吸収エネルギが12J(ジュール)以上となる。
As described above, the present applicant manages the Si content, the Mn content, and the pearlite ratio, which are three factors that have a causal relationship to the value of the impact absorption energy at low temperatures, thereby reducing the low temperature. We have demonstrated that the value of impact absorption energy below can be obtained.
From the results of the experiment, when the Si content, the Mn content, and the pearlite ratio are respectively set as follows, in the Charpy impact test at −40 ° C., the impact absorption energy is 12 J (joule) or more. Become.

次に、本実施例のダクタイル鋳鉄における化学組成の限定理由を説明する。
パーライト率:図3の−40°Cでの衝撃吸収エネルギと、パーライト率との相関関係のグラフで示されるように、パーライト率が20%以上となると、低温下での衝撃吸収エネルギが12J(ジュール)以下になり、低温下での衝撃吸収エネルギが低下する。
従って、本実施例ではパーライト率を20%以下としている。
Next, the reason for limiting the chemical composition of the ductile cast iron of this example will be described.
Perlite rate: As shown in the graph of the correlation between the impact absorption energy at −40 ° C. in FIG. 3 and the pearlite rate, when the pearlite rate is 20% or more, the impact absorption energy at a low temperature is 12 J ( Joule) or less, and the impact absorption energy at low temperatures decreases.
Therefore, in this embodiment, the pearlite rate is set to 20% or less.

C:本出願人の行なった実験によると、Cの含有量については、Cの含有量が少ないと、低温下での衝撃吸収エネルギが大きくなることから、本実施例ではCの含有量を3.5〜3.7重量%としている。   C: According to an experiment conducted by the present applicant, the C content is 3 in this example because the impact absorption energy at low temperatures increases when the C content is small. .5 to 3.7% by weight.

Si:図1の−40°Cでの衝撃吸収エネルギと、Si含有量との相関図から−40°Cでの衝撃吸収エネルギが12J(ジュール)以上となるには、Si含有量が2.3〜2.5重量%であればよい。含有量がこれより大きくなる、或いは小さくなると、−40°Cでの衝撃吸収エネルギの値は小さくなる。
従って、本実施例ではSiの含有量を2.3〜2.5重量%としている。
Si: From the correlation between the shock absorption energy at −40 ° C. and the Si content in FIG. 1, the Si content is 2.3 to make the shock absorption energy at −40 ° C. 12 J (joule) or more. It may be 2.5% by weight. When the content is larger or smaller than this, the value of the impact absorption energy at −40 ° C. becomes smaller.
Therefore, in this embodiment, the Si content is set to 2.3 to 2.5% by weight.

Mn:Mnはパーライトの発生を促進するパーライト化促進元素であり、Mnの含有量が多くなりすぎるとパーライト率が上昇し、−40°Cでの衝撃吸収エネルギも小さくなる。図5で示す−40°Cでの衝撃吸収エネルギと、Mn含有量との相関図では、Mn含有量が0.25重量%以上となると、−40°Cでの衝撃吸収エネルギが12J(ジュール)より低下してしまう。
従って、本実施例ではMnの含有量を0.25重量%以下としている。
Mn: Mn is a pearlite-promoting element that promotes the generation of pearlite. If the Mn content is too high, the pearlite rate increases and the impact absorption energy at −40 ° C. also decreases. In the correlation diagram between the impact absorption energy at −40 ° C. shown in FIG. 5 and the Mn content, when the Mn content is 0.25 wt% or more, the impact absorption energy at −40 ° C. is 12 J (joules). ) Will fall more.
Therefore, in this embodiment, the Mn content is 0.25 wt% or less.

また、Mn含有量を0.25重量%以下とするには、使用する材料配合率において、Mnの含有量の少ない銑鉄を通常より多量に用いることが効果的である。
一般に、鋳鉄の溶湯をつくる際には戻り材(方案部と不良品)と、廃材である鉄屑と、前工程で残った湯と、銑鉄を加えて必要な量の溶湯をつくる。加える銑鉄の材料配合率を40%以上とすることで全体のMnの含有量を0.25重量%以下に抑えるようにする。
Moreover, in order to make Mn content 0.25 weight% or less, it is effective to use pig iron with little Mn content more than usual in the material compounding ratio to be used.
In general, when making molten iron of cast iron, a return material (plan part and defective product), scrap iron as waste material, hot water left in the previous process, and pig iron are added to make the required amount of molten metal. The total amount of Mn content is suppressed to 0.25% by weight or less by setting the material mixture ratio of added pig iron to 40% or more.

図6は、−40°Cでの衝撃吸収エネルギと、1mm当たりでの直径5μm以上の黒鉛粒数との相関図である。図6のグラフで示されるように、黒鉛粒数の数が多くなるにつれて、−40°Cでの衝撃吸収エネルギも大きくなる。図6で示すグラフでは、直径5μm以上の黒鉛粒数が450個/mm以上となると、−40°Cでの衝撃吸収エネルギが12J(ジュール)より大きくなる。従って、本実施例では直径5μm以上の黒鉛粒数が450個/mm以上としている。 FIG. 6 is a correlation diagram between the impact absorption energy at −40 ° C. and the number of graphite grains having a diameter of 5 μm or more per 1 mm 2 . As shown in the graph of FIG. 6, as the number of graphite grains increases, the impact absorption energy at −40 ° C. also increases. In the graph shown in FIG. 6, when the number of graphite grains having a diameter of 5 μm or more is 450 particles / mm 2 or more, the impact absorption energy at −40 ° C. is larger than 12 J (joules). Therefore, in this embodiment, the number of graphite grains having a diameter of 5 μm or more is set to 450 pieces / mm 2 or more.

また、鋳鉄の鋳込み作業の際には、注湯前に接種材を添加することが行われている。これは、球状黒鉛の析出を促すために行なうもので、通常1回のみ行なうものであるが、本実験において、接種材の添加を出湯から注湯までの工程の中で複数回行なうことで、球状黒鉛の析出がより強く促進され、黒鉛粒数の数も多く析出される効果がある事が解かった。
特に注湯流接種や鋳型内接種などの溶湯を鋳型へ注湯する直前に接種を行なうと、より大きい効果が得られる。
したがって、注湯前に接種材を複数回添加することでより黒鉛粒数の数が多くなり、低温下での衝撃吸収エネルギを大きくすることができる。
Moreover, in the casting work of cast iron, adding an inoculum before pouring is performed. This is to promote the precipitation of spheroidal graphite and is usually performed only once, but in this experiment, by adding the inoculum several times in the process from pouring to pouring, It was found that the precipitation of spheroidal graphite was promoted more strongly, and the number of graphite particles was increased.
In particular, if the inoculation is performed immediately before pouring the molten metal such as pouring inoculation or inoculation into the mold, a greater effect can be obtained.
Therefore, the number of graphite grains is increased by adding the inoculum a plurality of times before pouring, and the impact absorption energy at low temperatures can be increased.

黒鉛粒数を多くすることは、パーライト率を少なくすることにも効果がある。黒鉛粒数が多いことにより、パーライトの発生を抑制し、パーライト率が低減される。また、前記の接種材の添加による効果の他にも、銑鉄を多く加えることで黒鉛粒数の発生数を多くし、パーライト率を低減することができる。
さらに、溶湯内の不純物を少なくすることで、パーライトの発生を抑えることができる。そのためには、不純物の含有量の少ない銑鉄を多く用いることが効果的であり、鋳鉄の溶湯をつくる際に、加える銑鉄の配合率を高くすることで溶湯内の不純物を少なくし、パーライトの発生を抑えることができる。
また、戻り材に銑鉄を多く用いたものを使うことでも溶湯内の不純物を少なくし、パーライトの発生を抑えることが可能となる。
Increasing the number of graphite grains is also effective in reducing the pearlite rate. When the number of graphite grains is large, the generation of pearlite is suppressed and the pearlite rate is reduced. In addition to the effect obtained by the addition of the inoculum, the number of graphite grains generated can be increased by adding a lot of pig iron to reduce the pearlite rate.
Furthermore, generation of pearlite can be suppressed by reducing impurities in the molten metal. For this purpose, it is effective to use a lot of pig iron with a low content of impurities. When making molten cast iron, increasing the blending ratio of pig iron to reduce the impurities in the melt and generating pearlite Can be suppressed.
Moreover, it is possible to reduce impurities in the molten metal and suppress the occurrence of pearlite by using a material that uses a lot of pig iron as the return material.

−40°Cでの衝撃吸収エネルギと、Si含有量との相関図。Correlation diagram between impact absorption energy at −40 ° C. and Si content. パーライト率と、Si含有量との相関図。The correlation diagram of a pearlite rate and Si content. −40°Cでの衝撃吸収エネルギと、パーライト率との相関図。Correlation diagram between impact absorption energy at −40 ° C. and pearlite rate. パーライト率と、Mn含有量との相関図。The correlation diagram of a pearlite rate and Mn content. −40°Cで衝撃吸収エネルギと、Mn含有量との相関図。Correlation diagram between impact absorption energy and Mn content at -40 ° C. −40°Cでの衝撃吸収エネルギと、1mm当たりでの直径5μm以上の黒鉛粒数との相関図。Correlation diagram between impact absorption energy at −40 ° C. and the number of graphite grains having a diameter of 5 μm or more per 1 mm 2 . Si含有量の違いにおける温度と衝撃吸収エネルギとの相関図。The correlation diagram of the temperature and impact absorption energy in the difference in Si content.

Claims (4)

C:3.5〜3.7重量%,Si:2.3〜2.5重量%,Mn:0.25重量%以下を含有し、パーライト率を20%以下に調整することを特徴とするダクタイル鋳鉄の製造方法。 C: 3.5 to 3.7% by weight, Si: 2.3 to 2.5% by weight, Mn: 0.25% by weight or less, and the pearlite ratio is adjusted to 20% or less. A method for producing ductile cast iron. 注湯前に接種材の添加を複数回実施することを特徴とする請求項1に記載のダクタイル鋳鉄の製造方法。 2. The method for producing ductile cast iron according to claim 1, wherein the inoculum is added a plurality of times before pouring. 組成組織において、直径5μm以上の黒鉛粒数を450個/mm以上に調整することを特徴とする請求項1または2に記載のダクタイル鋳鉄の製造方法。 3. The method for producing ductile cast iron according to claim 1, wherein the number of graphite grains having a diameter of 5 μm or more is adjusted to 450 pieces / mm 2 or more in the composition structure. 材料配合率において、銑鉄を40%使用することを特徴とする請求項1から3に記載のダクタイル鋳鉄の製造方法。
4. The method for producing ductile cast iron according to claim 1, wherein 40% of pig iron is used in a material blending ratio.
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KR100851651B1 (en) * 2005-10-05 2008-08-13 가부시키가이샤 덴소 Annular component fabricating method, die for use in such fabricating method and annular component fabricated thereby
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