JP3589601B2 - Thick large-sized cast steel products and their molds - Google Patents

Description

【００１３】
なお、本発明では、大型肉厚鋳鋼品で、その肉厚は２００ｍｍ以上を対象とする。
図１において、鋳型１は、鋳鋼品２の孔３を形成する中子４が、熱的に過酷な部位である。従って、この中子４の部分が、人造ムライト砂型５とされている。中子４以外の他の部分は、通常の砂型６とされている。
前記「熱的に過酷な部分」とは、砂型が１３００℃×６Ｈｒ以上、特に１４００℃×１０Ｈｒ以上に加熱保持されるような部位を指す。
【００１４】
また、前記「通常の砂型６」の成分、粒度、バインダは「表２」に示すとおりである。
【００１５】
【表２】

【００１６】
前記中子４を形成する人造ムライト砂型５は、その骨材として、硅砂より耐火度の高い人造ムライト（３Ａｌ２Ｏ３・２ＳｉＯ２）が１００％使用されており、バインダとして、有機自硬性樹脂が用いられている。
前記有機自硬性樹脂として、例えば、アルカリフェノール樹脂を用いた。なお、前記人造ムライトとして、「セラビーズ」という商品名のものを使用した。
なお、人造ムライトとした理由は、化学成分として、化学的に最も安定な比率で不純物を極力排除でき、高温にて焼成して製造するため、その組織は緻密であり、そのため、耐火性が高く、耐破砕性、耐熱衝撃性にも優れるためであり、又、形状因子として、製造時に表面張力により砂粒が真球状に近いものとなり、粒度分布及び通気度も安定しており、そのため流動性も良好で、砂の充填率を上げやすく、溶鋼の進入を防止する効果があるためである。
【００１７】
前記人造ムライト砂型５の表面には、コーティング材として、塗型が塗布されている。
前記塗型の骨材として、焼着の原因となるＳｉＯ２成分を含まない耐火度の高く、浸透性および熱膨張率が低い性質を持ち備えた高純度のアルミナ（Ａｌ２Ｏ３）が用いられている。骨材中のアルミナ成分は９９％以上の高純度とされている。
前記高純度アルミナとしては、焼結アルミナ、電融アルミナ、焼成アルミナの何れか、又は、それらの組み合わせのものが用いられている。また前記アルミナ粉末の粒度は、３５０メッシュ通過のものとされている。
【００１８】
前記塗型のバインダには、焼着の原因となるＳｉＯ２成分を含まず、作業性に優れ、浸透性の良好で膜厚が確保できるものが用いられている。
例えば、有機のものとして、アクリルバインダ、フェノール樹脂、ビンソール等があり、無機のものとして、酢酸ビニル、リン酸アルミ、尿酸アルミ等がある。そして、これらの組み合わせにより、作業性をよくする組み合わせを適宜選択する。
特に、ヒートクラックが発生しないようなバインダの選定を行う必要がある。熱硬化型の無機性の塗型では、ヒートクラックを緩和させることができないため、有機系樹脂をバインダとして用いている。
【００１９】
前記塗型の溶剤としては、水またはアルコールが用いられる。アルコールとしては、メチルアルコール及びエチルアルコールが用いられ、純エタノールが望ましい。
前記塗型は、下塗りと上塗りの二回塗りされている。塗型厚みとしては、１ｍｍ以上が望ましく、下塗り用塗型の鋳型への浸透深さは，１ｍｍ以上が望ましい。
【００２０】
【実施例】
図１に示す形状の鋳型１を用いて、普通重量鋳造法により、図２，３に示す形状の鋳鋼品２を鋳造した。鋳鋼の成分は、前記「表１」に示すとおりである。
このとき、鋳型１における中子４の砂の種類を「表３」に示すように、硅砂と人造ムライトとの二種類に変えまた、塗型の成分を各種変化させた。そして、各鋳型により鋳造した鋳鋼品の砂焼着率を測定した。
【００２１】
【表３】

【００２２】
前記表３におけるペケ、丸、三角印は、砂焼着率を示す。
ここで、「砂焼着率」とは、鋳型解枠後、砂落とし段階で、鋳鋼製品２の孔３に残存する砂の割合（孔全体の体積）の比率とした。砂が固まって通常の作業（シェイクアウト）では、とれないものを残存した砂とした。
前記表２より、熱的に過酷な部位に、人造ムライト砂型５を部分適用し、そして、その部分の表面に高純度アルミナからなる塗型を塗布することにより、砂の焼着が防止されることが判った。
【００２３】
図４に示すものは、前記中子４を人造ムライト砂型５とし、塗型の骨材及びバインダの成分を種々変更して鋳型１を作成し、そして、各鋳型１により鋳造した鋳鋼品２の砂焼着率を測定した結果を示す。図中、「シリカ分を含むバインダー」は、特公昭６１−４１６５６号公報に記載のものである。
図４によれば、塗型の骨材中のシリカ成分が少ないほど、また、バインダにもシリカ成分を含まないほど、砂焼着率が低くなることが判る。
更に、本発明実施品と比較例１〜４につき、砂焼着率と、原単位を比較した。その結果を表４、５に示す。
【００２４】
【表４】

【００２５】
【表５】

【００２６】
前記各表に示す実験は、前記図１に示す形状の鋳型１を用い、図２，３に示す形状の鋳鋼品２を鋳造した場合のものであり、その鋳鋼品２の成分は、「表１」に示すものである。
本発明実施例では、中子４の砂を人造ムライト１００％とし、そのバインダをアルカリフェノール樹脂とした。下塗り用及び上塗り用塗型の骨材は、アルミが９９％以上の高純度アルミナ粉末を用い、バインダとしてシリカ成分を含まないものとした。
【００２７】
なお、塗型のバインダは、アクリルバインダを用い、溶剤は、下塗り用にはエチルアルコールを用い、上塗り用には水を用いた。また、膜厚は下塗りが０．８〜１．０ｍｍ、上塗りが１〜２ｍｍとした。
その結果、砂焼着率は、ゼロであった。従って、原単位は、砂落とし工程がゼロ時間、グラインダー工程が０．１時間、機械加工が不要となり、手入れ工数もゼロ時間であり、又、製品歩留まり（最終形状重量で鋳込み重量を割ったもの）は、０．６０％向上した。
【００２８】
比較例１は、鋳型として主型と中子を有し、主型の使用砂は、クロマイトサンドで、バインダは、フラン樹脂を用い、中子の使用砂は、セラビーズで、バインダは、アルカリフェノール樹脂を用いた。
下塗り用及び上塗り用塗型の骨材は、アルミナ９５％で、バインダとしてシリカ成分を含有するものを用いた。焼着率は、５０％であった。
その結果、砂落とし作業はできなかった。また、グラインダー作業もできなかった。そのため、機械加工が必要となった。又加工後の手入れ作業は、１時間であった。製品歩留まりは向上しなかった。
【００２９】
比較例２は、前記比較例１と同じ鋳型を用い、下塗り用及び上塗り用塗型の骨材は、アルミナ９９％以上の高純度アルミナで、バインダとしてシリカ成分を含有するものを用いた。焼着率は、２０％であった。
その結果、機械加工は不要であり、手入れ作業は、０時間であった。製品歩留まりの向上は、０．６０％であったが、砂落とし作業に６時間を要し、また、グラインダー作業も４時間を要した。
比較例３は、前記比較例１と同じ鋳型を用い、下塗り用塗型の骨材は、マグネシアとし、バインダとしてシリカ成分を含有しないものを用いた。上塗り用塗型の骨材は、アルミナ９９％以上の高純度アルミナで、バインダとしてシリカ成分を含有しないものを用いた。焼着率は、１５％であった。
【００３０】
その結果、機械加工は不要であり、手入れ作業は、０時間であった。製品歩留まりの向上は、０．６０％であったが、砂落とし作業に４時間を要し、また、グラインダー作業も４時間を要した。
比較例４は、前記比較例１と同じ鋳型を用い、下塗り用塗型の骨材は、マグネシアとし、バインダとしてシリカ成分を含有するものを用いた。上塗り用塗型の骨材は、アルミナ９９％以上の高純度アルミナで、バインダとしてシリカ成分を含有するものを用いた。焼着率は、３０％であった。
【００３１】
その結果、砂落とし作業はできなかった。また、グラインダー作業もできなかった。そのため、機械加工が必要となった。手入れ作業は、１時間であった。製品歩留まりは向上しなかった。
なお、本発明は、前記実施例や実施の形態に示したものに限定されるものではない。即ち、肉厚２００ｍｍ以上の厚肉大型鋳鋼品において、鋳造で形成される孔の大きさは、直径２００ｍｍ以下かつ深さが直径以上となるような孔であれば良く、更に、孔に限らず溝やその他の形状の凹部であっても良く、その凹部は、幅２００ｍｍ以下かつ深さが幅以上であれば、本発明の対象となる。
【００３２】
【発明の効果】
本発明によれば、非常に熱的負荷の激しい部位（形状）のものの鋳出しが可能になり、それにより、機械加工等が不要になるので、大幅なコストダウンが図られる。
【図面の簡単な説明】
【図１】図１は、本発明の実施の形態として示す鋳型の断面図である。
【図２】図には、図１の鋳型により鋳造した鋳鋼品の断面図である。
【図３】図３は、図２の鋳鋼品の底面図である。
【図４】図４は、塗型中の骨材及びバインダーに含まれるシリカ成分の砂焼着への影響を示すグラフである。
【符号の説明】
１ 鋳型
２ 鋳鋼品
４ 中子
５ 人造ムライト砂型[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a thick-walled large-sized cast steel product and a mold thereof.
[0002]
[Prior art]
Thick, large-sized cast steel products cast using a sand mold have a problem of sand baking depending on the mold conditions. The sand baking phenomenon includes physical baking and chemical baking. Physical sintering is based on the penetration of molten steel into a mold, and chemical sintering is based on the formation of a low-melting compound due to the reaction between the FeO component in the molten steel and the SiO2 component in the mold.
In order to prevent physical seizure, it is desirable to select small sand particles in the mold. One measure to prevent chemical seizure is to use a high-temperature stable metal oxide that does not react with molten steel. Was.
[0003]
Further, as a function of reducing FeO causing baking, a mold containing C (see Japanese Patent Application Laid-Open No. 64-1222) and a metal mold containing Al (see Japanese Patent Application Laid-Open No. 56-122). No. 84146, JP-A-49-98722).
In addition, as a general coating type, a zircon coating type (using ZrO2.2SiO2 as an aggregate), a magnesia coating type (using MgO as an aggregate), and an alumina coating type (as an aggregate) , And those using Al2O3.SiO2). As these coating-type binders, those using an organic resin (phenol resin) or an inorganic (aluminum urate, colloidal silica) are known.
[0004]
Further, Japanese Patent Application Laid-Open No. Hei 4-2335 discloses that as a measure for preventing the intrusion of Mn components in molten steel into a silica sand mold for high-Mn cast steel reduced-pressure casting, an MgO-based coat is used as an undercoat and a high-purity coat is used as an overcoat. Using an alumina coating mold is disclosed.
[0005]
[Problems to be solved by the invention]
When casting a thick-walled large-sized cast steel product using the above-described conventional technique, there is still a problem that sand is baked in a complicated and thermally severe shape portion.
That is, when the magnesia coating mold is used in a thermally severely shaped portion, SiO2 and MgO in the mold component react with each other to generate a low-melting compound, thereby causing sand baking.
In addition, when a zircon coating mold was used, Al2O3 in the template component and SiO2 in the zircon reacted with each other to generate a low-melting-point compound, resulting in sand sintering.
[0006]
When a carbon-containing coating mold is used, C has entered the product due to the reaction between carbon and molten steel.
When an Al-containing coating mold is used, the entry of Al into a product becomes a problem due to the reaction between Al and molten steel.
Furthermore, when using a normal alumina coating mold, since natural alumina is used, an SiO2 component is contained in the component, which reacts with molten steel to form a low melting point compound, and the There was a problem that burning occurred.
[0007]
In view of the above, the present invention provides a mold for preventing the occurrence of sand sintering even in a complex and thermally severe shape part when casting a thick-walled large-sized cast steel product, and a sand sinter casting method using the mold. An object of the present invention is to provide a cast steel product that does not cause adhesion.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention has taken the following measures. That is, it is an aspect of the present invention, the main component in the sand molds used to cast the wall thickness 200mm or more thick large steel castings, the core is thermally harsh site, the person forming mullite constituted by artificial mullite sand mold which, in the person forming mullite sand, alumina component is in the point formed by coating a coating-type free was and SiO2 component mainly composed of high-purity alumina with 99% or more. According to the present invention, since SiO2 is not contained in the mold, the formation of a low-melting-point compound is not observed at the time of contact with molten steel during casting, chemical seizure is prevented, and a thick, heavy-weight complex shape is formed. Casting of the part becomes possible.
[0009]
In the artificial mullite sand mold, it is desirable that the aggregate is composed of 100% artificial mullite and the binder is composed of an organic self-hardening resin.
In the coating mold, it is desirable that the aggregate is made of high-purity alumina powder, and water or alcohol is mixed and coated.
The coating aggregate preferably has an alumina component of 99% or more.
It is preferable that the coating mold is applied at least twice, that is, undercoating and overcoating.
A feature of the thick-walled large-sized cast steel product of the present invention is that it is cast with the mold according to the present invention.
[0010]
Then, in a thick large cast steel product having a thickness of 200 mm or more, a hole having a diameter of 200 mm or less and a depth of not less than the diameter, or a recess having a width of 200 mm or less and a depth of not less than the width is formed at the time of casting. Is to do.
According to the present invention, sand is not baked in the cast-out hole or the concave portion, so that the steps of sand removal and care are not required. Conventionally, such holes or recesses are formed by machining. However, since the holes or recesses can be left as cast, the number of machining steps is reduced.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described.
FIG. 1 shows a casting mold 1 according to an embodiment of the present invention, and FIGS. 2 and 3 show a thick large cast steel product 2 cast using the casting mold 1.
This cast steel product 2 is a cylinder having a diameter of 1,000 mm and a height of 500 mm, and a blind hole 3 having a diameter of 70 mm and a depth of 150 mm is formed on one end surface thereof in a circumferential direction on a circumference of 500 mm in diameter. Four places are formed at equal intervals. Its product weight is 3,000 kg. The components of the cast steel product 2 are as shown in Table 1.
[0012]
[Table 1]

[0013]
In the present invention, a large cast steel product having a thickness of 200 mm or more is intended.
In FIG. 1, a mold 1 is a site where a core 4 forming a hole 3 of a cast steel product 2 is thermally severe. Therefore, the core 4 is formed as an artificial mullite sand mold 5. The other parts than the core 4 are ordinary sand molds 6.
The “thermally severe portion” refers to a portion where the sand mold is heated and maintained at 1300 ° C. × 6 Hr or more, particularly 1400 ° C. × 10 Hr or more.
[0014]
The components, particle size and binder of the “ordinary sand mold 6” are as shown in “Table 2”.
[0015]
[Table 2]

[0016]
The artificial mullite sand mold 5 forming the core 4 is made of 100% artificial mullite (3Al2O3 · 2SiO2) having higher fire resistance than silica sand as an aggregate thereof, and an organic self-hardening resin is used as a binder. I have.
As the organic self-hardening resin, for example, an alkali phenol resin was used. As the artificial mullite, one having a trade name of "Celabeads" was used.
The reason for using artificial mullite is that, as a chemical component, impurities can be eliminated as much as possible in the chemically most stable ratio, and since it is manufactured by firing at a high temperature, its structure is dense, and therefore, its fire resistance is high. It is also because of excellent crush resistance and thermal shock resistance, and as a shape factor, sand particles become almost spherical due to surface tension at the time of manufacture, particle size distribution and air permeability are stable, and therefore flowability is also This is because it is favorable and it is easy to increase the sand filling rate, and has an effect of preventing the intrusion of molten steel.
[0017]
A coating mold is applied to the surface of the artificial mullite sand mold 5 as a coating material.
As the coating aggregate, high-purity alumina (Al2O3) having high fire resistance, low permeability and low coefficient of thermal expansion, which does not contain a SiO2 component that causes baking, is used. The alumina component in the aggregate has a high purity of 99% or more.
As the high-purity alumina, any one of sintered alumina, fused alumina, and calcined alumina, or a combination thereof is used. The alumina powder has a particle size of 350 mesh.
[0018]
As the binder of the coating mold, a binder that does not include a SiO2 component that causes baking, has excellent workability, has good permeability, and can secure a film thickness is used.
For example, organic materials include acrylic binder, phenol resin, and vinsol, and inorganic materials include vinyl acetate, aluminum phosphate, and aluminum urate. And the combination which improves workability is suitably selected by these combinations.
In particular, it is necessary to select a binder that does not cause heat cracks. In a thermosetting inorganic coating mold, an organic resin is used as a binder because heat cracks cannot be reduced.
[0019]
Water or alcohol is used as the solvent for the coating. As the alcohol, methyl alcohol and ethyl alcohol are used, and pure ethanol is desirable.
The coating mold is applied twice: an undercoat and an overcoat. The coating thickness is desirably 1 mm or more, and the penetration depth of the undercoating mold into the mold is desirably 1 mm or more.
[0020]
【Example】
Using a mold 1 having the shape shown in FIG. 1, a cast steel product 2 having the shape shown in FIGS. The components of the cast steel are as shown in Table 1 above.
At this time, as shown in Table 3, the type of sand of the core 4 in the mold 1 was changed to two types of silica sand and artificial mullite, and the components of the mold were variously changed. Then, the sand deposition rate of the cast steel product cast by each mold was measured.
[0021]
[Table 3]

[0022]
Peke, circles, and triangles in Table 3 indicate the sand deposition rate.
Here, the “sand baking rate” is defined as the ratio of the ratio of the sand remaining in the holes 3 of the cast steel product 2 (the volume of the entire holes) at the sand removal stage after the mold is released. When the sand hardened and could not be removed by normal work (shake-out), the remaining sand was used.
According to Table 2, the artificial mullite sand mold 5 is partially applied to thermally severe portions, and a coating mold made of high-purity alumina is applied to the surface of the portions, thereby preventing the sand from burning. It turns out.
[0023]
In FIG. 4, the core 4 is an artificial mullite sand mold 5, the molds 1 are prepared by variously changing the components of the coating aggregate and the binder, and the cast steel product 2 cast by each mold 1 is prepared. The result of measuring the sand deposition rate is shown. In the figure, "binder containing silica" is that described in JP-B-61-41656.
According to FIG. 4, it can be seen that the smaller the silica component in the coating aggregate and the less the silica component is contained in the binder, the lower the sand deposition rate.
Furthermore, the sand deposition rate and the basic unit were compared for the product of the present invention and Comparative Examples 1 to 4. The results are shown in Tables 4 and 5.
[0024]
[Table 4]

[0025]
[Table 5]

[0026]
The experiment shown in each of the above tables is a case in which a casting 1 having the shape shown in FIGS. 2 and 3 is cast using the mold 1 having the shape shown in FIG. 1 ".
In the embodiment of the present invention, the sand of the core 4 is made of artificial mullite 100%, and the binder is made of an alkali phenol resin. The undercoating and overcoating aggregates were made of high-purity alumina powder having 99% or more aluminum and containing no silica component as a binder.
[0027]
Note that an acrylic binder was used as a coating mold binder, ethyl alcohol was used as a solvent for undercoating, and water was used for an overcoating. The thickness of the undercoat was 0.8 to 1.0 mm, and the thickness of the overcoat was 1 to 2 mm.
As a result, the sand deposition rate was zero. Therefore, the basic unit is as follows: the sand removal process is zero time, the grinder process is 0.1 hour, machining is not required, the maintenance man-hour is zero time, and the product yield (the casting weight divided by the final shape weight divided by the casting weight) ) Improved by 0.60%.
[0028]
Comparative Example 1 had a main mold and a core as molds, the sand used for the main mold was chromite sand, the binder used was furan resin, the sand used for the core was celabeads, and the binder was alkali phenol. Resin was used.
The aggregates for the undercoating and topcoating coatings used were composed of 95% alumina and containing a silica component as a binder. The baking rate was 50%.
As a result, sand removal was not possible. Also, I could not grinder. Therefore, machining was required. The maintenance work after processing was 1 hour. Product yield did not improve.
[0029]
In Comparative Example 2, the same mold as that of Comparative Example 1 was used, and the aggregate for the undercoating and topcoating molds was high-purity alumina of 99% or more alumina and containing a silica component as a binder. The baking rate was 20%.
As a result, no machining was required and the maintenance work was 0 hours. Although the improvement in product yield was 0.60%, the sand removal operation required 6 hours, and the grinder operation also required 4 hours.
In Comparative Example 3, the same mold as that of Comparative Example 1 was used. Magnesia was used as the undercoating aggregate, and a binder containing no silica component was used. The aggregate used for the top coat was a high-purity alumina of 99% or more alumina, which did not contain a silica component as a binder. The baking rate was 15%.
[0030]
As a result, no machining was required and the maintenance work was 0 hours. Although the improvement in the product yield was 0.60%, the sand removal operation required 4 hours, and the grinder operation also required 4 hours.
In Comparative Example 4, the same mold as in Comparative Example 1 was used, and the aggregate of the undercoating mold was magnesia, and a binder containing a silica component was used as a binder. The aggregate used for the top coat was a high-purity alumina of 99% or more alumina containing a silica component as a binder. The baking rate was 30%.
[0031]
As a result, sand removal was not possible. Also, I could not grinder. Therefore, machining was required. The care work was one hour. Product yield did not improve.
The present invention is not limited to the examples and the embodiments described above. That is, in a large-sized cast steel product having a thickness of 200 mm or more, the size of the hole formed by casting may be a hole having a diameter of 200 mm or less and a depth of not less than the diameter, and is not limited to the hole. The recess may be a groove or a recess having another shape, and the recess is an object of the present invention as long as the width is 200 mm or less and the depth is greater than the width.
[0032]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, casting of the part (shape) with a very severe thermal load is attained, and since a machining etc. become unnecessary, drastic cost reduction is achieved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a mold shown as an embodiment of the present invention.
FIG. 2 is a sectional view of a cast steel product cast by the mold of FIG. 1;
FIG. 3 is a bottom view of the cast steel product of FIG. 2;
FIG. 4 is a graph showing the effect of the silica component contained in the aggregate and the binder during coating on sand baking.
[Explanation of symbols]
Reference Signs List 1 mold 2 cast steel product 4 core 5 artificial mullite sand mold

Claims (6)

In sand molds used to cast the wall thickness 200mm or more thick large steel castings, the core is thermally harsh site, composed of a synthetic mullite sand composed mainly of human forming mullite, the person forming mullite A mold for a heavy-walled large-sized cast steel product, comprising a sand mold and a coating mold containing high-purity aluminum having an alumina component of 99% or more as a main component and containing no SiO2 component. 2. The mold for a heavy-walled large-sized cast steel product according to claim 1, wherein the artificial mullite sand mold has an aggregate made of 100% artificial mullite and a binder made of an organic self-hardening resin. 3. The mold according to claim 1, wherein in the coating mold, the aggregate is made of high-purity alumina powder, and water or alcohol is mixed and coated. The mold for a heavy-walled large-sized cast steel product according to any one of claims 1 to 3, wherein the coating mold is applied at least twice: an undercoat and an overcoat . A thick, large-sized cast steel product cast using the mold according to any one of claims 1 to 4 . It is a thick large-sized cast steel product having a wall thickness of 200 mm or more, and has a hole having a diameter of 200 mm or less and a depth of not less than a diameter, or a concave portion having a width of 200 mm or less and a depth of not less than a width. The thick large cast steel product according to claim 5 .

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