JP2018058112A - Shell-mold resin-coated foundry sand, core and main mold using the same, and method for manufacturing shell-mold resin-coated foundry sand - Google Patents
Shell-mold resin-coated foundry sand, core and main mold using the same, and method for manufacturing shell-mold resin-coated foundry sand Download PDFInfo
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本発明は、シェル鋳型用樹脂被覆鋳物砂、それを用いた主型及び中子、並びにシェル鋳型用樹脂被覆鋳物砂の製造方法に係る発明である。 The present invention relates to a resin-coated casting sand for a shell mold, a main mold and a core using the same, and a method for producing a resin-coated casting sand for a shell mold.
上記技術分野に関連する発明が、下記特許文献１に開示されている。特許文献１には、「目標粒度指数で、且つ、少なくともこの目標粒度指数を含む所定の粒度範囲で、粒度の粗い側の鋳物砂の割合が粒度の細かい側の鋳物砂の割合よりも大きく設定された粒度分布を有する」、鋳物砂および当該鋳物砂により造型された中子が開示されている。また、上記のような鋳物砂の製造方法として、「粒度指数が異なる複数種類の鋳物砂を所定の割合で混合することにより、目標粒度指数で、且つ、少なくともこの目標粒度指数を含む所定の粒度範囲で、粒度の粗い側の鋳物砂の割合が粒度の細かい側の鋳物砂の割合よりも大きく設定された粒度分布を有する鋳物砂を得る」、鋳物砂の製造方法が開示されている。
The invention related to the above technical field is disclosed in
そして、かかる特許文献１の鋳物砂により造型された中子によれば、「緻密で平滑な表面部を得ることができ、これらを用いて得られる鋳造品の表面性状も向上させることが可能になる」、と記載されている。
And, according to the core formed from the foundry sand of
鋳造により鋳造製品を製造するため使用する鋳型（主型、中子）の一種である有機鋳型として、粘桔用樹脂を骨材に被覆してなる樹脂被覆鋳物砂で造型されたシェル鋳型が周知である。シェル鋳型は、有機鋳型の中でも強度が高いので、鋳鉄や鋳鋼の鋳造製品の鋳造に幅広く使用されているが、近年、鋳型表面の砂の剥離によって生じる表面欠陥（すくわれ、型壊れ）や平滑性の面で従来水準以上の鋳肌品質の鋳造製品が具現されるとともに、内部に残存するガス欠陥がより抑制された鋳造製品が具現可能なシェル鋳型が求められている。すなわち、シェル鋳型用樹脂被覆鋳物砂（Resin Coated Sand、以下、ＲＣＳという場合がある。）は、骨材である砂の表面に、フェノール樹脂やフラン樹脂などの粘桔用樹脂が被覆されている。そして、このＲＣＳで造型された主型と中子で形成されるキャビティに金属溶湯を注湯すると、高温の金属溶湯に触れた主型や中子のＲＣＳ表面の樹脂は分解してガスが発生する。このガスが注湯された金属溶湯に混入すると、得られた鋳造製品にガス欠陥が残存する場合がある。このため、シェル鋳型には、上記したように発生したガスが、当該シェル鋳型の内部を通じ外部へ充分に排出されるような通気性が求められる。 As an organic mold that is a type of mold (main mold, core) used to produce a cast product by casting, a shell mold made of resin-coated casting sand in which an adhesive resin is coated on an aggregate is well known. It is. Shell molds, which have high strength among organic molds, are widely used for casting cast iron and cast steel products. In recent years, surface defects (scooping, mold breakage) and smoothness caused by peeling of the mold surface from the sand have occurred. Therefore, there is a need for a shell mold that can realize a cast product having a cast surface quality that is higher than the conventional level in terms of performance and that can realize a cast product in which gas defects remaining therein are further suppressed. That is, resin-coated sand for shell mold (Resin Coated Sand, hereinafter sometimes referred to as RCS) is coated with a resin for viscosity such as phenol resin or furan resin on the surface of the sand as an aggregate. . Then, when molten metal is poured into the cavity formed by the main mold and the core formed by the RCS, the resin on the RCS surface of the main mold and the core that touched the high-temperature molten metal is decomposed to generate gas. To do. When this gas is mixed in the molten metal poured, gas defects may remain in the obtained cast product. For this reason, the shell mold is required to have air permeability such that the gas generated as described above is sufficiently discharged to the outside through the inside of the shell mold.
ここで、従来水準並み以上の鋳肌品質とガス欠陥の抑制という２つの要請は、シェル鋳型を形成するＲＣＳの仕様という面からは、相反する要請である。つまり、鋳肌品質を向上するためには鋳造製品が形成されるシェル鋳型の表面を高密度および平滑にする必要があり、より粒度の細かいＲＣＳで高強度のシェル鋳型を形成する方向となる。一方で、シェル鋳型の通気性を高め、発生したガスの排気を改善するためには、より粒度の粗いＲＣＳでシェル鋳型を形成する方向となる。そして、上記２つの要請をともに満たすためには、シェル鋳型の強度および表面平滑性と通気性という面で、ＲＣＳの構成を適正化する必要がある。 Here, the two requirements of the casting surface quality that is equal to or higher than the conventional level and the suppression of gas defects are contradictory requirements from the aspect of the RCS specifications for forming the shell mold. That is, in order to improve the casting surface quality, it is necessary to make the surface of the shell mold on which the cast product is formed high density and smooth, and the direction is to form a high strength shell mold with a finer grain size RCS. On the other hand, in order to improve the air permeability of the shell mold and improve the exhaust of the generated gas, the shell mold is formed with a coarser RCS. In order to satisfy both of the above two requirements, it is necessary to optimize the configuration of the RCS in terms of the strength, surface smoothness and air permeability of the shell mold.
本発明は、従来技術水準以上の鋳肌品質を有する鋳造製品を得ることができ、かつ内在するガス欠陥が抑制された鋳造製品を得ることができるシェル鋳型用樹脂被覆鋳物砂（ＲＣＳ）、それを用いた主型及び中子を提供することを目的としている。また、本発明は、上記ＲＣＳを製造できる好適な製造方法を提供することを目的としている。 The present invention provides a resin-molded molding sand (RCS) for a shell mold, which can obtain a cast product having a casting surface quality higher than that of the prior art and can obtain a cast product in which inherent gas defects are suppressed, The purpose is to provide a main mold and core using Another object of the present invention is to provide a suitable manufacturing method capable of manufacturing the RCS.
上記課題を解決する本発明の一つの実施形態は、JIS Z 8825-1に準拠して粒度分布を測定したときの体積基準の累積分布において、5％累積粒子径(d5)が140〜180μｍ、50％累積粒子径(d50)が220〜280μｍ、95％累積粒子径(d95)が390〜440μｍであり、粒子径300〜400μｍの占める割合が10〜40％、 頻度分布において、前記50％累積粒子径(d50)と95％累積粒子径(d95)の間に最頻値が存在する、シェル鋳型用樹脂被覆鋳物砂である。なお、前記最頻値は250〜300μｍ、その頻度が11〜13％、であることが望ましい。 One embodiment of the present invention that solves the above problems is a volume-based cumulative distribution when measuring the particle size distribution in accordance with JIS Z 8825-1, 5% cumulative particle diameter (d5) is 140-180 μm, 50% cumulative particle size (d50) is 220-280μm, 95% cumulative particle size (d95) is 390-440μm, the proportion of particle size 300-400μm is 10-40%, 50% cumulative in frequency distribution This is a resin-coated cast sand for a shell mold in which a mode value exists between the particle size (d50) and the 95% cumulative particle size (d95). The mode value is preferably 250 to 300 μm and the frequency is 11 to 13%.
本発明の別の実施形態は、前記シェル鋳型用樹脂被覆鋳物砂で造型された主型であり、更に別の実施形態は、当該シェル鋳型用樹脂被覆鋳物砂で造型された中子である。 Another embodiment of the present invention is a main mold made of the above-mentioned resin-coated casting sand for a shell mold, and yet another embodiment is a core formed of the resin-coated casting sand for a shell mold.
さらに、本発明の別の実施形態は、上記シェル鋳型用樹脂被覆鋳物砂の好適な製造方法であり、第１の砂と第２の砂とを混合して混合砂を得る混合工程と、前記混合工程で得られた混合砂にシェル鋳型用樹脂を被覆し、乾燥させる被覆工程と、を有し、前記第１の砂は、5％累積粒子径(d5)が110〜180μｍ、50％累積粒子径(d50)が220〜260μｍ、95％累積粒子径(d95)が360〜420μｍであり、前記第２の砂は、5％累積粒子径(d5)が240〜280μｍ、50％累積粒子径(d50)が330〜390μｍ、95％累積粒子径(d95)が520〜580μｍ、であり、（前記第１の砂の重量／前記第２の砂の重量）が2〜8である、シェル鋳型用樹脂被覆鋳物砂の製造方法である。 Furthermore, another embodiment of the present invention is a preferred method for producing the resin-coated cast sand for the shell mold, wherein the mixing step of mixing the first sand and the second sand to obtain mixed sand, Coating the sand obtained by the mixing step with a resin for shell mold, and drying the coating. The first sand has a 5% cumulative particle diameter (d5) of 110 to 180 μm and a 50% cumulative The particle size (d50) is 220 to 260 μm, the 95% cumulative particle size (d95) is 360 to 420 μm, and the second sand has a 5% cumulative particle size (d5) of 240 to 280 μm and a 50% cumulative particle size. Shell mold in which (d50) is 330 to 390 μm, 95% cumulative particle size (d95) is 520 to 580 μm, and (weight of the first sand / weight of the second sand) is 2 to 8. It is a manufacturing method of resin-coated casting sand for use.
上記した本発明に係るシェル鋳型用樹脂被覆鋳物砂、それを用いた主型及び中子によれば、従来技術水準並みまたはそれ以上の鋳肌品質を有する鋳造製品を得ることができ、かつ内在するガス欠陥が抑制された鋳造製品を得ることができる。また、本発明に係るシェル鋳型用樹脂被覆鋳物砂の製造方法によれば、上記構成のシェル鋳型用樹脂被覆鋳物砂を好適に製造することができる。 According to the above-described resin-coated cast sand for a shell mold according to the present invention, a main mold and a core using the same, a cast product having a casting surface quality equivalent to or higher than that of the prior art can be obtained, and is inherent. A cast product with suppressed gas defects can be obtained. Moreover, according to the manufacturing method of the resin coating casting sand for shell molds concerning this invention, the resin coating casting sand for shell molds of the said structure can be manufactured suitably.
以下、本発明について、より具体的に説明する。なお、本発明は、以下説明する具体的な形態および例に限定されず、同一性の範囲で変形して実施することができる。 Hereinafter, the present invention will be described more specifically. In addition, this invention is not limited to the specific form and example demonstrated below, It can deform | transform and implement in the range of identity.
上記したように本発明に係るシェル鋳型用樹脂被覆鋳物砂（ＲＣＳ）は、シェル鋳型を造型するため粘桔性を有するシェル鋳型用樹脂で骨材が被覆されてなる鋳物砂であり、得られた鋳造製品の鋳肌品質の向上とガス欠陥の抑制という面から、下記詳述するように、その粒度分布が適正化されている。なお、ＲＣＳを構成する骨材は、例えば、けい砂、ジルコン砂やオリビン砂などの天然砂、ムライト系セラミック砂やフェロニッケル鉱滓加工砂などの人工砂、またはそれらの再生砂など、鋳型として求められる強度や耐熱性などの特性に応じ周知の骨材を適宜使用すれば良い。また、この骨材に被覆されるシェル鋳型用樹脂も、常温では粘桔性が低いが加熱により粘桔性を発揮する樹脂であれば特に限定されず、例えばノボラック型やレゾール型のフェノール樹脂など周知のシェル鋳型用樹脂を使用すれば良い。 As described above, the resin-molded molding sand (RCS) for shell mold according to the present invention is a molding sand in which an aggregate is coated with a resin for shell mold having a stickiness to form a shell mold. From the aspect of improving the casting surface quality of the cast products and suppressing gas defects, the particle size distribution is optimized as described in detail below. The aggregate constituting the RCS is found as a mold, for example, natural sand such as silica sand, zircon sand and olivine sand, artificial sand such as mullite ceramic sand and ferronickel mined sand, or regenerated sand thereof. A well-known aggregate may be used as appropriate according to properties such as strength and heat resistance. Also, the resin for the shell mold to be coated on the aggregate is not particularly limited as long as it is a resin that has low viscosity at room temperature but exhibits viscosity by heating, such as a novolak-type or resol-type phenol resin, etc. A known shell mold resin may be used.
そして、本発明に係るＲＣＳは、JIS Z 8825-1に準拠して粒度分布を測定したときの体積基準の累積分布において、
（１）5％累積粒子径（d5）が140〜180μｍ、50％累積粒子径（d50）が220〜280μｍ、95％累積粒子径（d95）が390〜440μｍであり、
（２）粒子径300〜400μｍの占める割合が10〜40％、頻度分布において、50％累積粒子径（d50）と95％累積粒子径（d95）の間に最頻値が存在するＲＣＳである。なお、5％累積粒子径（d5）、50％累積粒子径（d50）および95％累積粒子径（d95）とは、本発明に係るＲＣＳの粒度分布の一例である図１に示すように、JIS Z 8825-1に準拠して測定された粒度分布において、小径側から頻度分布を累積していったときに累積値が全体の5％、50％および95％となる粒子径のことを指す。
The RCS according to the present invention is a volume-based cumulative distribution when the particle size distribution is measured according to JIS Z 8825-1.
(1) 5% cumulative particle size (d5) is 140-180 μm, 50% cumulative particle size (d50) is 220-280 μm, 95% cumulative particle size (d95) is 390-440 μm,
(2) RCS with a particle size of 300 to 400 μm occupying 10 to 40%, and in frequency distribution, there is a mode value between 50% cumulative particle size (d50) and 95% cumulative particle size (d95) . The 5% cumulative particle size (d5), 50% cumulative particle size (d50) and 95% cumulative particle size (d95) are as shown in FIG. 1 which is an example of the RCS particle size distribution according to the present invention. In the particle size distribution measured in accordance with JIS Z 8825-1, this refers to the particle size where the cumulative value is 5%, 50% and 95% of the total when the frequency distribution is accumulated from the small diameter side. .
上記（１）の要件の限定理由を説明する。5％累積粒子径（d5）、50％累積粒子径（d50）および95％累積粒子径（d95）が下限値未満であると、ＲＣＳの粒度が細か過ぎて造型されたシェル鋳型の通気性が低くなり、ガス欠陥が発生する恐れがある。一方で、これらが上限値を超えると、通気性は高いが、造型されたシェル鋳型の表面の平滑性および強度が低くなるので、鋳肌品質が低下する恐れがある。このため、5％累積粒子径（d5）、50％累積粒子径（d50）および95％累積粒子径（d95）は、各々、140〜180μｍ、220〜280μｍ、390〜440μｍの範囲とする。好ましくは、145〜170μｍ、230〜275μｍ、395〜430μｍの範囲である、 The reason for limiting the requirement (1) will be described. If the 5% cumulative particle size (d5), 50% cumulative particle size (d50) and 95% cumulative particle size (d95) are less than the lower limit, the RCS particle size is too fine and the air permeability of the shell mold formed is too small. Lowering may cause gas defects. On the other hand, if these values exceed the upper limit, the air permeability is high, but the smoothness and strength of the surface of the molded shell mold are lowered, so that the casting surface quality may be deteriorated. For this reason, the 5% cumulative particle size (d5), 50% cumulative particle size (d50), and 95% cumulative particle size (d95) are in the ranges of 140 to 180 μm, 220 to 280 μm, and 390 to 440 μm, respectively. Preferably, it is in the range of 145 to 170 μm, 230 to 275 μm, 395 to 430 μm,
ここで、ＲＣＳの粒度分布はJIS Z 8825-1に準拠して測定するが、具体的に、例えば、日機装(株)製マイクロトラック粒度分布測定装置(MT3000)を用いて測定することができる。 Here, the particle size distribution of RCS is measured according to JIS Z 8825-1. Specifically, for example, the particle size distribution can be measured using a Microtrac particle size distribution measuring device (MT3000) manufactured by Nikkiso Co., Ltd.
上記したように本発明に係るＲＣＳは、上記要件（１）の粒度分布を有するが、その一つの特徴は、粒子径300〜400μｍの占める割合が10〜40％であり、頻度分布において、50％累積粒子径（d50）と95％累積粒子径（d95）との間に最頻値が存在する点（要件（２））にある。つまり、本発明に係る鋳物砂は、図１に示すように、95％累積粒子径（d95）の前後の領域の粒子径である300〜400μｍという粒子径がやや粗い砂粒子（以下、中径粒子と言う場合がある。）を上記割合で含有せしめ、当該中径粒子よりも粒子径が細かい小径粒子と、より粗い大径粒子との混合割合を最適化せしめている。そのうえで、50％累積粒子径（d50）と95％累積粒子径（d95）との間に最頻値が存在せしめる、これを言い換えると、本発明に係るＲＣＳでは、その粒度分布を、比較的粒子径が大きい側に偏在せしめている。これにより、このＲＣＳで造型されたシェル鋳型では、主に中径粒子および大径粒子により砂粒子間の間隙が適正化される。そして、この適正化された砂粒子間の間隙に小径粒子が配置されることにより鋳物砂の充填性が高まり、かつ当該間隙により適切な通気性が確保され、その結果、シェル鋳型の表面の平滑性および強度と通気性の両立を図ることができるのである。なお、上記最頻値は250〜300μｍであり、その頻度が11〜13％であることが望ましい。 As described above, the RCS according to the present invention has the particle size distribution of the above requirement (1). One of the characteristics is that the proportion of the particle diameter of 300 to 400 μm is 10 to 40%. A mode value (requirement (2)) exists between the% cumulative particle diameter (d50) and the 95% cumulative particle diameter (d95). That is, as shown in FIG. 1, the foundry sand according to the present invention is a sand particle having a particle diameter of 300 to 400 μm, which is the particle diameter in the region before and after the 95% cumulative particle diameter (d95) (hereinafter referred to as the medium diameter). In this case, the mixing ratio of the small-sized particles having a smaller particle diameter than the medium-sized particles and the coarser large-sized particles is optimized. In addition, a mode value exists between the 50% cumulative particle size (d50) and the 95% cumulative particle size (d95). In other words, in the RCS according to the present invention, the particle size distribution is relatively reduced to the particle size distribution. It is unevenly distributed on the larger diameter side. Thereby, in the shell mold formed by this RCS, the gap between the sand particles is optimized mainly by the medium diameter particles and the large diameter particles. Further, by arranging the small-diameter particles in the gaps between the optimized sand particles, the filling property of the foundry sand is increased, and appropriate air permeability is secured by the gaps. As a result, the surface of the shell mold is smoothed. Therefore, it is possible to achieve both the property and strength and the air permeability. The mode is preferably 250 to 300 μm and the frequency is preferably 11 to 13%.
そして、本発明に係るＲＣＳによれば、上記した要件（１）および（２）を兼ね備えることにより、当該ＲＣＳにより形成されたシェル鋳型（主型、中子）は、その表面の平滑性および強度と通気性とが適正化され、鋳肌品質の向上とガス欠陥の抑制とを両立することが可能となる。なお、上記ＲＣＳを使用してシェル鋳型を造型する場合には、例えば重力落下（ダンプボックス）法、吹き込み法など各種周知の造型方法を適用してシェル鋳型を造型すればよい、 According to the RCS according to the present invention, the shell mold (main mold, core) formed by the RCS has the surface smoothness and strength by combining the above requirements (1) and (2). Therefore, it is possible to achieve both improvement in casting surface quality and suppression of gas defects. In addition, when forming a shell mold using the RCS, for example, a shell mold may be formed by applying various well-known molding methods such as a gravity drop (dump box) method and a blowing method.
上記ＲＣＳの製造方法は特に限定されないが、次に述べる製造方法により好適に製造することができる。すなわち、本発明に係るＲＣＳの製造方法は、第１の砂と第２の砂とを混合して混合砂を得る混合工程と、前記混合工程で得られた混合砂にシェル鋳型用樹脂を被覆し、乾燥させる被覆工程と、を有し、前記第１の砂は、５％累積粒子径（d5）が110〜180μｍ、50％累積粒子径（d50）が220〜260μｍ、95％累積粒子径（d95）が360〜420μｍであり、前記第２の砂は、5％累積粒子径（d5）が240〜280μｍ、50％累積粒子径（d50）が330〜390μｍ、95％累積粒子径（d95）が520〜580μｍ、であり、（前記第１の砂の重量／前記第２の砂の重量）が2〜8である。かかるＲＣＳの製造方法によれば、上記説明した構成のＲＣＳを好適に製造することができる。尚、前記第１の砂は、５％累積粒子径（d5）が120〜170μｍ、50％累積粒子径（d50）が230〜250μｍ、95％累積粒子径（d95）が370〜410μｍであり、前記第２の砂は、5％累積粒子径（d5）が245〜270μｍ、50％累積粒子径（d50）が335〜380μｍ、95％累積粒子径（d95）が530〜570μｍ、であり、（前記第１の砂の重量／前記第２の砂の重量）が2〜7であることが好ましい。 The production method of the RCS is not particularly limited, but can be suitably produced by the production method described below. That is, the RCS manufacturing method according to the present invention includes a mixing step of mixing the first sand and the second sand to obtain mixed sand, and coating the mixed sand obtained in the mixing step with a resin for shell mold. The first sand has a 5% cumulative particle size (d5) of 110 to 180 μm, a 50% cumulative particle size (d50) of 220 to 260 μm, and a 95% cumulative particle size. (D95) is 360-420 μm, and the second sand has a 5% cumulative particle size (d5) of 240-280 μm, a 50% cumulative particle size (d50) of 330-390 μm, and a 95% cumulative particle size (d95 ) Is 520 to 580 μm, and (weight of the first sand / weight of the second sand) is 2 to 8. According to this RCS manufacturing method, the RCS having the above-described configuration can be preferably manufactured. The first sand has a 5% cumulative particle size (d5) of 120 to 170 μm, a 50% cumulative particle size (d50) of 230 to 250 μm, and a 95% cumulative particle size (d95) of 370 to 410 μm, The second sand has a 5% cumulative particle size (d5) of 245 to 270 μm, a 50% cumulative particle size (d50) of 335 to 380 μm, and a 95% cumulative particle size (d95) of 530 to 570 μm. The weight of the first sand / the weight of the second sand) is preferably 2-7.
具体的には、所定温度に加熱した第１の砂および第２の砂をミキサーに投入し混合した後、シェル鋳型用樹脂（フェノール樹脂）を溶融被覆させた後、レゾール樹脂の場合は冷却水、ノボラック樹脂の場合はさらに硬化剤であるヘキサメチレンテトラミン（ヘキサミン）を投入して混練する。そして、冷却が進み、骨材同士の固着が少なくなった時点で、ステアリン酸カルシウム（ステカル）を投入、分散させて自由流動可能な状態にすれば良い。 Specifically, after the first sand and the second sand heated to a predetermined temperature are put into a mixer and mixed, a shell mold resin (phenol resin) is melt-coated, and in the case of a resole resin, cooling water is used. In the case of a novolak resin, hexamethylenetetramine (hexamine) as a curing agent is further added and kneaded. Then, when the cooling progresses and the adhesion between the aggregates decreases, calcium stearate (stekal) may be added and dispersed to make it free flowing.
なお、混合工程で使用する骨材としての第１の砂および第２の砂は特に限定されず、例えば、けい砂、ジルコン砂やオリビン砂などの天然砂、ムライト系セラミック砂やフェロニッケル鉱滓加工砂などの人工砂、またはそれらの再生砂など、鋳型として求められる強度や耐熱性などの特性に応じ周知の骨材を適宜使用すれば良い。また、この被覆工程で骨材に被覆されるシェル鋳型用樹脂も、常温では粘桔性が低いが加熱により粘桔性を発揮する樹脂であれば特に限定されず、例えばノボラック型やレゾール型のフェノール樹脂など周知のシェル鋳型用樹脂を使用すれば良い。 The first sand and the second sand as aggregates used in the mixing step are not particularly limited. For example, natural sand such as silica sand, zircon sand and olivine sand, mullite ceramic sand and ferronickel iron processing A well-known aggregate may be appropriately used according to properties such as strength and heat resistance required as a mold, such as artificial sand such as sand, or recycled sand thereof. Also, the resin for the shell mold that is coated on the aggregate in this coating step is not particularly limited as long as it is a resin that has low viscosity at room temperature but exhibits viscosity by heating. For example, a novolak type or resol type resin is used. A known shell mold resin such as phenol resin may be used.
以下、本発明の具体的実施例について説明する。実施例１〜３および比較例１および２ごとに、表１に示す粒度分布の第１の砂および第２の砂を所定の割合で混合して混合砂を作成し、当該混合砂にシェル鋳型用樹脂としてフェノール樹脂を被覆し、各実施例および比較例ごとに、表２に示す粒度分布（d5、d50、d95、中径粒子割合およびピーク粒径）を有するＲＣＳを得た。なお、骨材である第１の砂および第２の砂としては、ムライト系セラミック砂を使用した。
また、第１の砂、第２の砂、及びＲＣＳの粒径及び粒度分布は日機装(株)製マイクロトラック粒度分布測定装置(MT3000)を用いて測定し、粒度分布から5％累積粒子径（d5）、50％累積粒子径（d50）、95％累積粒子径（d95）、300-400μmの割合、ピーク粒径、ピーク頻度を求めた。
Hereinafter, specific examples of the present invention will be described. For each of Examples 1 to 3 and Comparative Examples 1 and 2, first sand and second sand having a particle size distribution shown in Table 1 are mixed at a predetermined ratio to prepare mixed sand, and a shell mold is formed on the mixed sand. A phenol resin was coated as a resin for use, and an RCS having a particle size distribution (d5, d50, d95, medium diameter particle ratio and peak particle diameter) shown in Table 2 was obtained for each Example and Comparative Example. In addition, mullite ceramic sand was used as the first sand and the second sand which are aggregates.
In addition, the particle size and particle size distribution of the first sand, the second sand, and the RCS were measured using a Nikkiso Co., Ltd. Microtrac particle size distribution measuring device (MT3000), and the 5% cumulative particle size ( d5), 50% cumulative particle size (d50), 95% cumulative particle size (d95), ratio of 300-400 μm, peak particle size, and peak frequency were determined.
上記ＲＣＳを造型し、直径50ｍｍ、長さ50ｍｍの通気度用試験片を製作してＪＩＳZ2601の付属書３の迅速法に基づき、通気度を測定した。
また、縦×横×長さが10ｍｍ×10ｍｍ×60ｍｍの抗折試験片を作成し、ＪＩＳK 6910に基づき抗折力を測定した。各実施例および比較例の通気度および抗折力の測定結果を表３に示す。
The RCS was molded, a test piece for air permeability having a diameter of 50 mm and a length of 50 mm was produced, and the air permeability was measured based on the rapid method in
In addition, a bending test piece having a length × width × length of 10 mm × 10 mm × 60 mm was prepared, and the bending strength was measured based on JIS K 6910. Table 3 shows the measurement results of air permeability and bending strength of each example and comparative example.
次いで、各実施例および比較例ごとに作成されたＲＣＳを造型し、図２に示す、中空状のキャビティ３を有するシェル鋳型２を作成した。なお、符号１はシェル鋳型を保持するための鋳枠であり、符号４は、溶湯を注湯するための湯口である。そして、ＪＩＳG5122のSCH22に相当するステンレス鋳鋼溶湯を1600℃の注湯温度で当該鋳型２のキャビティ３に注湯し、各実施例および比較例ごとに、各6個の鋳造製品を得た。
Subsequently, RCS produced for each Example and Comparative Example was formed, and a
得られた鋳造製品の鋳肌評価の結果を表２に示す。
鋳肌評価において、
×は鋳肌不良率が90％以上、
△は10〜90％（従来水準）、
○は10％未満
であったことを示す。
また、得られた鋳造製品を切断し、シェル鋳型と接触していた部分の表面をグラインダで僅かに研削した後に、浸透探傷試験により単位面積当たりのガス欠陥の発生量を確認した。
直径3.0ｍｍ以上のガス欠陥の単位面積当たりの発生量（個／25cm２）を表３に示す。
Table 2 shows the results of the cast skin evaluation of the obtained cast product.
In casting surface evaluation,
X indicates a casting surface defect rate of 90% or more.
△ is 10-90% (conventional level),
○ indicates that it was less than 10%.
Further, the obtained cast product was cut, and the surface of the portion that had been in contact with the shell mold was slightly ground with a grinder, and then the amount of gas defects generated per unit area was confirmed by a penetration inspection test.
Table 3 shows the generation amount (units / 25 cm 2 ) per unit area of gas defects having a diameter of 3.0 mm or more.
表３に示すように、本発明の範囲である実施例１〜３では、従来水準以上に鋳肌不良率が低くかつガス欠陥の発生量を抑制できることが確認された。一方で、本発明の範囲外である比較例１、３、４ではガス欠陥の発生量が多く、比較例２では鋳肌不良率が高かった。 As shown in Table 3, in Examples 1 to 3, which are the scope of the present invention, it was confirmed that the casting surface defect rate was lower than the conventional level and the amount of gas defects generated could be suppressed. On the other hand, in Comparative Examples 1, 3, and 4, which are outside the scope of the present invention, the amount of gas defects generated was large, and in Comparative Example 2, the casting surface defect rate was high.
１ 鋳枠
２ シェル鋳型
３ キャビティ
４ 湯口
1
Claims (5)
粒子径300〜400μｍの占める割合が10-40％、
頻度分布において、前記50％累積粒子径(d50)と95％累積粒子径(d95)の間に最頻値が存在するシェル鋳型用樹脂被覆鋳物砂。 In the volume-based cumulative distribution when measuring the particle size distribution according to JIS Z 8825-1, 5% cumulative particle size (d5) is 140-180μm, 50% cumulative particle size (d50) is 220-280μm, 95 % Cumulative particle size (d95) is 390-440μm,
10-40% of the particle size is 300-400μm,
Resin-coated casting sand for a shell mold in which a mode value exists between the 50% cumulative particle diameter (d50) and the 95% cumulative particle diameter (d95) in the frequency distribution.
第１の砂と第２の砂とを混合して混合砂を得る混合工程と、
前記混合工程で得られた混合砂にシェル鋳型用樹脂を被覆し、乾燥させる被覆工程と、を有し、
前記第１の砂は、5％累積粒子径(d5)が110-180μｍ、50％累積粒子径(d50)が220-260μｍ、95％累積粒子径(d95)が360-420μｍであり、前記第２の砂は、5％積粒子径(d5)が240-280μｍ、50％累積粒子径(d50)が330-390μｍ、95％累積粒子径(d95)が520-580μｍ、であり、
（前記第１の砂の重量／前記第２の砂の重量）が2-8である、シェル鋳型用樹脂被覆鋳物砂の製造方法。 A method for producing resin-coated casting sand for a shell mold,
A mixing step of mixing the first sand and the second sand to obtain mixed sand;
Covering the mixed sand obtained in the mixing step with a resin for shell mold and drying the coating,
The first sand has a 5% cumulative particle size (d5) of 110-180 μm, a 50% cumulative particle size (d50) of 220-260 μm, and a 95% cumulative particle size (d95) of 360-420 μm, The sand of No. 2 has a 5% particle size (d5) of 240-280 μm, a 50% cumulative particle size (d50) of 330-390 μm, and a 95% cumulative particle size (d95) of 520-580 μm,
A method for producing resin-coated cast sand for a shell mold, wherein (weight of the first sand / weight of the second sand) is 2-8.
A core formed from the resin-coated casting sand for a shell mold according to claim 1 or 2.
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