JP4679718B2

JP4679718B2 - Recycling of recovered foundry sand

Info

Publication number: JP4679718B2
Application number: JP2000381606A
Authority: JP
Inventors: 幸一藤江; 裕之大門; 正勝岡本; 茂夫仲井
Original assignee: Toyohashi University of Technology NUC
Current assignee: Toyohashi University of Technology NUC
Priority date: 2000-12-15
Filing date: 2000-12-15
Publication date: 2011-04-27
Anticipated expiration: 2020-12-15
Also published as: JP2002178100A

Description

【０００１】
【発明の属する技術分野】
本発明は回収鋳物砂の再生方法に関する。
【０００２】
【従来の技術】
有機自硬性バインダーが使用された回収鋳物砂の再生方法として、鋳物砂に振動、衝撃を与えてブロック状のものを粉砕した後、さらに砂粒子同士または砥石などとの摩擦によって機械的に表面の不純物を取り除く方法が一般的である。このような方法に用いる装置として、例えば特開平７−３１４０８２号に記載されたような鋳物砂再生装置が提案されている。
【０００３】
しかしながら、このような機械的な方法では、不純物の除去を十分行うことが困難であり、砂の破砕、細粒化などによる歩留まりの低下や、鋳型強度低下が生じてしまう。
【０００４】
【発明が解決しようとする課題】
本発明は、従来技術の問題点を解決するものであり、不純物の除去率が高く鋳物品質及び鋳型強度が向上できる回収鋳物砂の再生方法を提供することを目的とする。更に本発明は、砂の破砕や細粒化が起こらず歩留まりが向上する回収鋳物砂の再生方法を提供することを目的とする。
【０００５】
【課題を解決するための手段】
本発明は、回収鋳物砂を１００℃以上に加熱された水（以下、高温水という）と接触させる工程を有する回収鋳物砂の再生方法に関する。
【０００６】
回収鋳物砂と高温水とを接触させる方法としては、高温水発生器で発生させた高温水を回収鋳物砂洗浄器に導いて接触させてもよいし、回収鋳物砂と水とを耐圧密閉容器中で加熱することで高温水を発生させて接触させてもよい。設備が簡便である点から、後者の方法が好ましい。
【０００７】
【発明の実施の形態】
本発明に用いられる回収鋳物砂は、ケイ砂、ジルコン砂、クロマイト砂、合成ムライト砂などの鋳物砂に、バインダーを使用して造型した後、解枠（型ばらし）して得られた回収砂ないし余剰砂である。本発明の再生方法は、特に有機自硬性バインダーで造型された鋳型から回収された鋳物砂に好適である。ここで、有機自硬性バインダーとは、フラン、アルカリフェノール、フェノールウレタン等の自硬性樹脂である。
【０００８】
本発明では、１００℃以上、好ましくは１５０℃〜５５０℃、特に好ましくは２５０℃〜４５０℃に加熱された水を用いる。なお、回収鋳物砂に接触させる水の量は、加熱前の重量比で、水／回収鋳物砂＝１／１〜５０／１、更に２／１〜３０／１、特に５／１〜２０／１で用いることが好ましい。また、耐圧密閉容器中で両者を接触させる場合、その容器は限定されないが、加熱中、すなわち回収鋳物砂と高温水との接触中に内部が５０ＭＰａの圧力となっても耐え得るような材質、構成のものが好ましい。また、回収鋳物砂と水は、加熱前の耐圧密閉容器の空間容積率が９０％以下、更に１〜８０％、特に５〜７５％となるように、容器に投入することが好ましい。また、高温水発生器と回収鋳物砂洗浄器とを用いる場合、高温水発生器は、高温水を調製するための加圧器、加熱器を有し、洗浄器は、回収鋳物砂を出し入れできる洗浄室と、この洗浄室に前記高温水を導入する導入口と、この洗浄室から排出弁を介して液体を排出する排出口とを有していればよい。
【０００９】
本発明の再生方法の一例を図１により説明する。図１において、１は回収鋳物砂、２は水、３は耐圧密閉容器（反応容器）、４は塩浴（ソルトバス）、５は圧力計である。反応容器３に所定量の回収鋳物砂１と水２とを入れる。その際、上記の通り、水／回収鋳物砂の重量比、空間容積率を調整することが好ましい。なお、空間容積率は、図１の反応容器３容積のうち、水２の上方にできる空間の体積が占める割合である。その後、ソルトバス４に反応容器３を浸漬し加熱を行う。その際、上記の通り、加熱温度、容器内圧力を調整することが好ましい。加熱時間（加熱温度の保持時間）は限定しないが、５分〜２時間、更に１５分〜１時間を目安とするのが好ましい。なお、加熱温度は、一定でも変動させてもよい。
【００１０】
本発明の好ましい実施条件として、耐圧密閉容器を用いる方法において、加熱前の水と回収鋳物砂の重量比を水／鋳物回収砂＝５／１〜２５／１とし、空間容積率を５〜８０％とし、加熱温度を１５０〜４５０℃とし、加熱時間（加熱温度の保持時間）を３０〜６０時間とする方法が挙げられる。この場合、耐圧密閉容器内部の圧力は１０〜４５ＭＰａが好ましい。
【００１１】
本発明の再生方法は、水の存在下で、回収鋳物砂を高温、高圧処理するため、共存する水が蒸気ないし臨界状態となり、その一方で有機自硬性バインダーの分解が進行し、水への溶解や低分子化合物への分解が相乗的に進行し、効率的にバインダー成分を除去できるものと考えられる。このため、本発明では、水の臨界温度（３７４℃）以上の温度並びに水の臨界圧力（２２１気圧≒２２４０００ｈＰａ）以上の圧力で、回収鋳物砂を処理することがより好ましい。
【００１２】
本発明のより具体的に好ましい態様としては、有機自硬性バインダーが付着した回収鋳物砂を、１００℃以上に加熱された水と、接触、好ましくは耐圧密閉容器中で接触させて、前記バインダーを除去する再生方法が挙げられる。
【００１３】
【実施例】
尿素変成フラン樹脂又は水溶性アルカリフェノール樹脂を粘結剤に使用したケイ砂回収鋳物砂と水とを、図１に示す反応装置に投入し、加熱処理した。そのときの処理条件（水／回収鋳物砂重量比、空間容積率、加熱温度、加熱時間）を表１、２に示す。なお、加熱時間は、表１、２の加熱温度を保持した時間である。
【００１４】
加熱処理後の砂について、鋳型強度、強熱減量、残留窒素分及び残留硫黄分（尿素変成フラン樹脂のみ）、並びに歩留まりを以下の方法で測定した。結果を表１、２に示す。
【００１５】
（１）鋳型強度
ＪＩＳＺ２６０４−１９７６により測定した。ただし、尿素変成フラン樹脂を用いた回収鋳物砂については２５℃×６０％ＲＨ条件下で、花王ライトナーＣ−１４（スルホン酸系硬化剤、花王クエーカー（株）製）を回収鋳物砂（ケイ砂再生砂）に対し０．３２重量％添加し混連後、花王ライトナー３４０Ｂ（尿素変成フラン樹脂、花王クエーカー（株）製）をケイ砂再生砂に対し０．８重量％添加し混練後、直ちに直径５０ｍｍ×高さ５０ｍｍのテストピースに充填し２４Ｈｒ後、圧縮強度（ＭＰa）を測定した。また、水溶性アルカリフェノール樹脂を用いた回収鋳物砂については花王ステップＱＸ−１４０（エステル系硬化剤、花王クエーカー（株）製）を回収鋳物砂（ケイ砂再生砂）に対し０．３重量％添加し混練後、花王ステップＳ−６６０（水溶性アルカリフェノール樹脂、花王クエーカー（株）製）をケイ砂再生砂に対し１．２重量％添加し混連後、直ちに直径５０ｍｍ×高さ５０ｍｍのテストピースに充填し２４Ｈｒ後、圧縮強度（ＭＰa）を測定した。
【００１６】
（２）強熱減量
不純物の除去率を示すものであり、ＪＩＳＺ２６０４により測定した。
【００１７】
（３）残留窒素分
残留窒素は鋳物のガス欠陥を誘発する元素であり、ＪＩＳＭ８８１３−１９９４７．２ケルダール法で測定した。残留量が少ない事が望ましい。
【００１８】
（４）残留硫黄分
残留硫黄はダクタイル鋳鉄において鋳物表層部の黒鉛球状化を阻害する元素であり、ＪＩＳＭ８８１３−１９９４５．３高温燃焼法で測定した。残留量が少ない事が望ましい。
（５）歩留まり
再生処理前後での回収砂重量％で求めた。
【００１９】
【表１】

【００２０】
＊試験Ｎｏ．４は、通常の機械的処理を想定したものであり、ロータリーリクレーマ（日本鋳造（株）製）のＢ再生条件（弱条件）により１パス処理した。
【００２１】
【表２】

【００２２】
**試験Ｎｏ．８は、通常の機械的処理を想定したものであり、ロータリーリクレーマ（日本鋳造（株）製）のＡ再生条件（強条件）により４パス処理した。
【００２３】
【発明の効果】
本発明では、回収鋳物砂を高温水で処理する事により、従来の機械的に砂表面を処理する方法に較べ、歩留まりを落とすことなく効率よく不純物を除去できる。また、本発明によって再生された鋳物砂は、鋳物品質及び鋳型強度に優れる。
【００２４】
例えば、尿素変成フラン樹脂を使用する造型法では、鋳型強度が向上し安定した鋳型の製造が可能となり、残留窒素の低減によりガス欠陥の軽減、更に残留硫黄の低減によりダクタイル鋳鉄において鋳物表層部の黒鉛球状化阻害の軽減が可能となる。また、水溶性アルカリフェノール樹脂を使用する造型法では、従来の機械的再生法では安定した鋳型強度を維持するため強力な再生条件が必要で、その結果歩留まりが大幅に低下するという問題がある。しかし、本発明により歩留まりを低下すること無く、強度の安定した鋳型の製造が可能となる。
【図面の簡単な説明】
【図１】本発明の実施態様の一例を示す概略図
【符号の説明】
１回収鋳物砂
２水
３耐圧密閉容器
４ソルトバス
５圧力計[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for reclaiming recovered foundry sand.
[0002]
[Prior art]
As a method of reclaiming recovered foundry sand using an organic self-hardening binder, the cast sand is vibrated and impacted to pulverize the block-shaped one, and then mechanically the surface is rubbed by friction between sand particles or a grindstone. A method of removing impurities is common. As an apparatus used for such a method, for example, a foundry sand recycling apparatus as described in JP-A-7-314082 has been proposed.
[0003]
However, with such a mechanical method, it is difficult to sufficiently remove impurities, resulting in a decrease in yield due to sand crushing and fine graining and a decrease in mold strength.
[0004]
[Problems to be solved by the invention]
An object of the present invention is to solve the problems of the prior art, and to provide a method for reclaiming recovered foundry sand that has a high impurity removal rate and can improve casting quality and mold strength. A further object of the present invention is to provide a method for reclaiming recovered foundry sand that does not cause sand crushing or fine graining and improves yield.
[0005]
[Means for Solving the Problems]
The present invention relates to a method for reclaiming recovered foundry sand having a step of bringing recovered foundry sand into contact with water heated to 100 ° C. or higher (hereinafter referred to as high temperature water).
[0006]
As a method of bringing the recovered foundry sand into contact with the high temperature water, the high temperature water generated by the high temperature water generator may be brought into contact with the recovered foundry sand washing device, or the recovered foundry sand and water may be brought into pressure-resistant sealed containers. You may make it contact by generating high temperature water by heating in. The latter method is preferable because the facilities are simple.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The recovered foundry sand used in the present invention is recovered sand obtained by forming a cast sand such as silica sand, zircon sand, chromite sand, and synthetic mullite sand using a binder, and then releasing the frame. Or surplus sand. The regeneration method of the present invention is particularly suitable for foundry sand recovered from a mold formed with an organic self-hardening binder. Here, the organic self-hardening binder is a self-hardening resin such as furan, alkali phenol, or phenolurethane.
[0008]
In the present invention, water heated to 100 ° C. or higher, preferably 150 ° C. to 550 ° C., particularly preferably 250 ° C. to 450 ° C. is used. In addition, the amount of water brought into contact with the recovered foundry sand is, by weight ratio before heating, water / recovered foundry sand = 1/1 to 50/1, further 2/1 to 30/1, particularly 5/1 to 20 /. 1 is preferable. In addition, when both are brought into contact in a pressure-resistant sealed container, the container is not limited, but a material that can withstand even when the pressure is 50 MPa during heating, that is, during contact between recovered foundry sand and high-temperature water, A configuration is preferred. The recovered foundry sand and water are preferably introduced into the container so that the space volume ratio of the pressure-tight airtight container before heating is 90% or less, further 1 to 80%, particularly 5 to 75%. In addition, when using a high-temperature water generator and a recovered foundry sand washer, the high-temperature water generator has a pressurizer and a heater for preparing high-temperature water, and the washer is capable of taking in and out the recovered foundry sand. It is only necessary to have a chamber, an inlet for introducing the high-temperature water into the cleaning chamber, and a discharge port for discharging the liquid from the cleaning chamber via a discharge valve.
[0009]
An example of the reproducing method of the present invention will be described with reference to FIG. In FIG. 1, 1 is recovered foundry sand, 2 is water, 3 is a pressure-resistant sealed container (reaction vessel), 4 is a salt bath (salt bath), and 5 is a pressure gauge. A predetermined amount of recovered foundry sand 1 and water 2 are placed in a reaction vessel 3. At that time, as described above, it is preferable to adjust the weight ratio of water / recovered foundry sand and the space volume ratio. The space volume ratio is the ratio of the volume of the space formed above the water 2 to the volume of the reaction container 3 in FIG. Thereafter, the reaction vessel 3 is immersed in the salt bath 4 and heated. At that time, as described above, it is preferable to adjust the heating temperature and the pressure in the container. The heating time (heating temperature holding time) is not limited, but is preferably 5 minutes to 2 hours, and more preferably 15 minutes to 1 hour. Note that the heating temperature may be constant or variable.
[0010]
As a preferred implementation condition of the present invention, in the method using a pressure-resistant airtight container, the weight ratio of water before heating and recovered foundry sand is water / cast recovered sand = 5/1 to 25/1, and the space volume ratio is 5 to 80. %, Heating temperature is 150 to 450 ° C., and heating time (heating temperature holding time) is 30 to 60 hours. In this case, the pressure inside the pressure tight sealed container is preferably 10 to 45 MPa.
[0011]
In the recycling method of the present invention, the recovered foundry sand is treated at a high temperature and high pressure in the presence of water, so that the coexisting water is in a vapor or critical state, while the decomposition of the organic self-hardening binder proceeds, and the water is converted into water. It is considered that dissolution and decomposition into low molecular weight compounds proceed synergistically and the binder component can be efficiently removed. Therefore, in the present invention, it is more preferable to treat the recovered foundry sand at a temperature equal to or higher than the critical temperature of water (374 ° C.) and a pressure equal to or higher than the critical pressure of water (221 atm≈224000 hPa).
[0012]
As a more specifically preferred embodiment of the present invention, the recovered foundry sand to which the organic self-hardening binder is attached is brought into contact with water heated to 100 ° C. or higher, preferably in a pressure-tight airtight container, and the binder is used. Examples of the regeneration method include removal.
[0013]
【Example】
Silica sand recovered foundry sand and water using urea-modified furan resin or water-soluble alkali phenol resin as a binder were put into the reaction apparatus shown in FIG. 1 and heat-treated. The processing conditions (water / recovered foundry sand weight ratio, space volume ratio, heating temperature, heating time) at that time are shown in Tables 1 and 2. The heating time is the time for which the heating temperatures in Tables 1 and 2 are maintained.
[0014]
For the sand after the heat treatment, the mold strength, loss on ignition, residual nitrogen content and residual sulfur content (urea modified furan resin only), and yield were measured by the following methods. The results are shown in Tables 1 and 2.
[0015]
(1) Mold strength Measured according to JIS Z 2604-1976. However, for recovered foundry sand using urea-modified furan resin, Kao Lightner C-14 (sulfonic acid curing agent, manufactured by Kao Quaker Co., Ltd.) was recovered under the conditions of 25 ° C. × 60% RH (silica sand). After adding 0.32% by weight to the regenerated sand), Kao Lightner 340B (urea modified franc resin, manufactured by Kao Quaker Co., Ltd.) is added 0.8% by weight to the regenerated sand of sand and immediately after kneading. A test piece having a diameter of 50 mm and a height of 50 mm was filled, and after 24 hours, the compressive strength (MPa) was measured. For recovered foundry sand using water-soluble alkali phenol resin, Kao Step QX-140 (ester hardener, manufactured by Kao Quaker Co., Ltd.) is 0.3% by weight with respect to recovered foundry sand (silica sand recycled sand). After adding and kneading, Kao Step S-660 (water-soluble alkali phenol resin, manufactured by Kao Quaker Co., Ltd.) is added by 1.2% by weight to the regenerated sand of silica sand, and immediately after mixing, the diameter is 50 mm × height is 50 mm. After filling the test piece and 24 hours, the compressive strength (MPa) was measured.
[0016]
(2) Shows the removal rate of ignition loss impurities, measured according to JIS Z 2604.
[0017]
(3) Residual nitrogen content Residual nitrogen is an element that induces gas defects in castings, and was measured by the JIS M 8813-1994 7.2 Kjeldahl method. It is desirable that the residual amount is small.
[0018]
(4) Residual Sulfur Content Residual sulfur is an element that inhibits graphite spheroidization of the casting surface layer in ductile cast iron, and was measured by JIS M 8813-1994 5.3 high temperature combustion method. It is desirable that the residual amount is small.
(5) Obtained by weight% of collected sand before and after the yield regeneration treatment.
[0019]
[Table 1]

[0020]
* Test No. No. 4 was assumed to be a normal mechanical treatment, and was subjected to one pass treatment under the B regeneration condition (weak condition) of a rotary reclaimer (manufactured by Nippon Casting Co., Ltd.).
[0021]
[Table 2]

[0022]
** Test No. No. 8 was assumed to be a normal mechanical treatment, and was subjected to a 4-pass treatment under A regeneration conditions (strong conditions) of a rotary reclaimer (manufactured by Nippon Casting Co., Ltd.).
[0023]
【The invention's effect】
In the present invention, by treating the recovered foundry sand with high-temperature water, impurities can be efficiently removed without lowering the yield as compared with the conventional method of mechanically treating the sand surface. Moreover, the foundry sand regenerated by the present invention is excellent in casting quality and mold strength.
[0024]
For example, in the molding method using urea-modified furan resin, the mold strength is improved, and a stable mold can be produced. Reduction of residual nitrogen reduces gas defects, and reduction of residual sulfur further reduces the casting surface layer of ductile cast iron. It is possible to reduce inhibition of graphite spheroidization. In addition, the molding method using a water-soluble alkali phenol resin has a problem that the conventional mechanical regeneration method requires strong regeneration conditions in order to maintain a stable mold strength, resulting in a significant decrease in yield. However, the present invention makes it possible to produce a mold having a stable strength without reducing the yield.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an example of an embodiment of the present invention.
1 recovered sand 2 water 3 pressure-resistant sealed container 4 salt bath 5 pressure gauge

Claims

A method for reclaiming recovered foundry sand, comprising a step of bringing the recovered foundry sand into contact with water heated to 250 ° C to 450 ° C in a pressure-resistant sealed container .

The weight ratio of water before being heated and recovered foundry sand, water / recovered foundry sand = 1 / 1-50 / 1 at which claim 1 Symbol mounting playback method.

The regeneration method according to claim 1 or 2 , wherein the recovered foundry sand and water are put into the pressure-tight container and the water is heated thereafter so that the space volume ratio of the pressure-tight container is 90% or less.

The recycling method according to any one of claims 1 to 3 , wherein the recovered foundry sand is recovered from a mold formed with an organic self-hardening binder.

The regeneration method according to claim 4, wherein the organic self-hardening binder is a urea-modified furan resin or a water-soluble alkali phenol resin.