DE3030991A1 - FOUNDRY ITEMS, PREPARATIONS FOR TREATMENT AND METHOD FOR THE PRODUCTION THEREOF. - Google Patents

Abstract

A preparation for producing or treating casting moulds and similar foundry articles contains at least one silicate component which is a hybrid silicate or a silicyl metaphosphate, mixed with at least one refractory aggregate, as the predominant component; the preparation can contain additives such as surfactants. <IMAGE>

Description

Foundry articles, preparations for treatment and

Process for producing the same The invention relates to foundry articles, in particular forms, as well as preparations and methods for treatment and production such foundry articles. In particular, the invention relates to improved molds and new coatings, impregnates (i.e. impregnation processes or impregnating agents) and Binder preparations, as well as processes for the treatment and creation of casting molds, Press molds, refractory parts of ovens or pouring pans, ceramic mold cores and similar foundry products in one to improve the piercing temperature resistance and the fire resistance of such articles in an appropriate manner.

For the treatment and manufacture of foundry articles such as casting molds, various types of silicate-containing compositions are known, e.g. B. the in U.S. Patents 4,113,499, 4,111,705, 3,961,968, 3,957,715, 3,682,668, 3,576,652, 3,211,560 and 2,842,445 preparations described. For some of the patents in the above Methods described are silicate-containing preparations the molding sand or other crushed refractory material used to make the mold, incorporated as a binder or as an impregnation or coating of one of these Material manufactured form used. The described containing silicate Preparations contain various other components or defined percentages Compositions and are generally effective for their intended purpose. Furthermore, with some of these methods described, the need for heat curing of shapes avoided, d. H. in other words, it can be air-curable or non-fired Forms are obtained.

However, some of the known methods make air curable forms obtained whose molded skin or treated surface has insufficient resistance against certain conditions frequently encountered in foundries. For example With some known preparations, no molded skin is obtained, which is the intensive one Heat and that caused by the movement of the hot turbulent molten metal, which is poured into the mold cavity, withstands erosion caused. Other known Preparations lead to multi-part skin structures which, when heated to a great extent, lead to Tend to crack. Other known preparations allow unwanted penetration of metal in the molding sand or adverse chemical reactions or splitting or breaking open the surface of the mold cavity.

According to the invention, advantages in casting molds, compression molds, refractory parts of furnaces and ladles, ceramic cores and other similar items Foundry products achieved by using a coating that has a specific Contains silicate and refractory aggregate. That in the preparation according to the invention The silicate used is a hybrid silicate or a silicyl metaphosphate and the refractory Aggregate is preferably selected from zirconium, silicon dioxide, aluminum oxide silicates, Graphite, fused silica, alumina, chromite, fibrous alumina silicates and combinations thereof. Also have the refractory aggregates preferably a particle diameter size distribution of between about 10 and 3000 microns.

A particularly suitable one for use for preparations according to the invention Hybrid silicate is described in US Pat. No. 3,961,968, to which particular reference is made here will. The hybrid silicate can be produced according to the following example: Component % By weight (approximation) alkyl silicate (ethyl silicate, type 40) 7-9 acidic silica sol (colloidal Silica) 45-55 water 0.5-1 glycol ether 35-45 sulfuric acid (37%) 0.25 ethanol or isopropanol 5 A reaction vessel was used to produce this hybrid silicate used, which has a cooling device to the 0 reaction mixture at a Maintain temperature between 20 and 27 C. This reaction vessel was with a Premix of 0.25% concentrated sulfuric acid (37%), 0.75% water and 5% isopropanol charged. 40% ethylene glycol monoethyl ether was added with stirring and then 8% ethyl silicate, Type 40 (available from Union Carbide Company) added to the above mixture and mixed for an additional 30 minutes. The resulting mixture was now left to stand for 48 hours and then stabilized with 51% acid Silica solution added, the mixture to temperatures between 20 and 270C was held.

The other silicate, namely the silicyl metaphosphate, can by use of the components specified below and their processing according to the following Process described are produced: component wt.% (approximation) sulfuric acid (37%) 0.25 water (distilled, deionized) 0.99 colloidal silica sol (acidic) 49.05 ethylene glycol monoethyl ether 30.01 phosphoric acid (85%) 11.60 ethyl silicate, Type 40 8.10 In a water-cooled reaction chamber, 0.25% was concentrated Sulfuric acid (37%) combined with 0.99% distilled and deionized water. With stirring, 22.50% Glycoläther.in was added to the reaction chamber and then immediately followed by 8.10% ethyl silicate, type 40 (available from Union Carbide Company) was added.

The mixture was then mixed for 30 min at a carefully between 0-20 and stirred at a temperature maintained at 27 ° C. After 30 minutes, this mixture became 48 hours. kept at 20-27 C, whereupon 49.05% acidic colloidal silica sol slowly in the reaction chamber was inserted. The mixture was then stirred for an additional 2 hours and the temperature of the reaction mixture was kept at 20127 ° C. If those Implementation is almost complete, a mixture of 11.60% becomes more concentrated Phosphoric acid and 7.51 t of glycol ether introduced and the whole thing reacted for 30 minutes. The product finally obtained was allowed to cool to room temperature and stored until the coating preparation is made.

For the production of a silicyl metaphosphate which is suitable for use Suitable in the invention, the following components can be specified in the below Type to be implemented: component wt.% (Approximation) hydrochloric acid (37%) 0.15 ethyl silicate, Type 40 27.42 colloidal silica sol (alkaline or acidic) 10.63 isopropanol (anhydrous) 41.83 phosphoric acid (85%) 19.94 The preparation obtained from these components was worked up as follows: In a reaction vessel equipped with a cooling device 0.15% concentrated hydrochloric acid (37%) was carefully mixed with 10.63% more alkaline colloidal silica mixed. While stirring, 20.92% isopropanol was added to the Reaction vessel fed and stirred for 10 min. Then a premix was made 20.92% isopropanol and 19.94% phosphoric acid were introduced into the reaction vessel and the contents stirred for 30 minutes. The resulting mixture was then 24 hours at a Maintained temperature between 20 and 27 0C. After 24 hours, 27.42% ethyl silicate, Type 40, slowly fed into the reaction vessel, the temperature between 20 and 27 C. The contents of the reaction vessel then became thorough for 1 hour mixed, held between 20 and 27 0C for 24 hours and then used for the production of the coating preparation stored.

The silicyl metaphosphate prepared according to the invention and in particular the product obtained by the two methods described above has the formula in which n = 1, 2, 3 or 4.

For the production of a coating preparation according to one embodiment of the invention is a predetermined amount of the hybrid silicate and any of the above refractory aggregates mentioned or a combination of such aggregates to form a slurry mixed for application to the surface of the mold cavity a casting mold or on the surface part to be treated of a similar foundry article suitable is. The mixture can also contain a predetermined amount of an additive contain to increase the wet strength, z. B. polyvinyl acetate, polyvinyl alcohol or sound. Furthermore, the mixture can contain a surfactant to the aggregates in the Better to wet the preparation of the coating preparation. Suitable surfactants are the usual sodium soaps of fatty acids, carboxymethyl cellulose, sodium sulfates, Sodium tripolyphosphates and synthetic detergents, such as Victawet "from Stauffer Chemical Company, "Wetsit®" from Nopco Chemical Company, and "Lestoil" from Noxell Corporation. Suitable fatty acid surfactants include "Xsetanol" from Clyco Chemicals, Inc., "Surfact" from Casting Supply home, New York, and "V; estasep" from West Chemical Products, Inc. Preferred Synthetic surfactants are those with a straight chain and 10 or more carbon atoms in the chain.

The coating preparation just described can be as follows contain special components and are manufactured in the manner indicated below be: component wt.% (approximation) refractory aggregate 75-90 polyvinyl acetate or Polyvinyl alcohol 0.5 hybrid silicate 10-25 surfactant 0.1 40.9% refractory aggregate were in a reactor vessel, which was provided with a cooling device, around the Keep the reaction mixture below 30 C at all times, with 18.5% hybrid silicate mixed for 15 min, whereupon 0.5% polyvinyl acetate is fed into the reaction vessel became.

The resulting mixture was stirred for 5 minutes, whereupon 0.1 Z surfactant added and mixed for a further 5 min. To this preparation became the refractory Aggregate added as the remaining portion and the aggregate mixture worked through for 15 minutes. After mixing thoroughly, the product was allowed to cool to room temperature.

The coating preparation produced in this way is in Form a slurry and can be in any suitable manner on a certain surface part of the mold to be treated, the core or the like Foundry articles are applied.

The drawing shows an example of a foundry article to be treated a casting mold 10 in the form of a compact made of quartz sand 12 or other comminuted material refractory material, as it is commonly used for foundry technology, shown in a shaped bottle 14. If the foundry article to be treated has a Shape is, at least the surface of the intended to receive the molten metal Mold cavity 16 and optionally all parts of the mold, which the mold cavity surrounded, as well as the mold inlet or sprue channel 18 and main channel 20 with the described Preparation, e.g. B. by brushing, painting, spraying or other application methods, coated. The form coated in this way is then allowed to air dry for about 20 minutes left, creating a shape that has a skin or coating 22 with a Has a thickness of approximately 0.4 to 0.8 mm in the surface parts treated in this way, and those with the hybrid silicate to a depth of about 5 cm to increase the Bond strength of the form is impregnated. Molds treated in this way have one improved surface quality and show considerable resistance to the Penetration of turbulent molten metal into the mold surface and against flaking and erosion. Furthermore, the casting mold treated in this way shows a considerably higher fire resistance than the corresponding untreated mold.

For a coating preparation that is different from the is prepared in the above example illustrated embodiment, the new silicyl metaphosphate according to the invention together with a refractory unit or a combination used by such aggregates to form the coating slurry. the Mixture can further include a predetermined amount or type of additive to increase the Wet strength included, e.g. B. polyvinyl acetate, polyvinyl alcohol or clay. the Mixture can also include a surfactant for better wetting of the aggregates during the Preparation of the coating preparation included. Suitable surfactants are above specified.

The coating just described using silicyl metaphosphate may contain the following specific components and as described below produced: component wt.% (approximation) fire-resistant aggregate 75-90 polyvinyl acetate or polyvinyl alcohol 0.5 silicyl metaphosphate 10-25 surfactant 0.1 in a reactor vessel, which contains a cooling device to keep the reaction mixture below 300C at all times to maintain, with stirring, 40.9% refractory aggregate became 18.5% silicyl metaphosphate given and mixed for 15 minutes. Then the stirring was stopped and 0.5 % Polyvinyl acetate slowly introduced into the vessel. The resulting mixture was Stirred for 5 min and mixed with 0.1% surfactant, whereupon the mixture was stirred for a further 5 min became. Then the remaining portion of the refractory aggregate became the preparation given and the resulting mixture mixed for 15 min. After thorough mixing of the product was allowed to cool to room temperature.

The silicyl metaphosphate prepared in the manner just described The coating formulation containing is in the form of a slurry and can in the same way on the surface or part of the surface of the casting mold, of the core or similar foundry articles to be treated according to the above for the Coating preparation made from hybrid silicate and refractory aggregate methods mentioned are applied. As with the coating method with the The surface is created using a coating preparation made from hybrid silicate and refractory aggregate of the mold cavity and any other surrounding parts of the mold with the preparation from silicyl metaphosphate and refractory aggregate either by brushing, brushing, Spray or coated by another application method. The treated like that The mold or core or a similar foundry article is then turned on for about 20 minutes left to air dry. The foundry article thus obtained shows the same advantageous ones Properties like the one with the preparation based on hybrid silicate and fire solid aggregate treated articles including increased durability against layer separation, cracking, erosion, adverse heat effects as well an impregnation with the silicyl metaphosphate to a depth of about 5 cm, whereby the form or the article shows an increased bond strength. Indeed is the wet or raw strength of casting molds and similar treated in this way Foundry articles three times higher. When the molds treated in this way are heated become, the strength of the form increases to over tenfold and turns out to be Resistant to 0 temperatures of over 1650 C without deformation due to Iloch temperature softening.

The manufactured according to the two embodiments described above Silicyl metaphosphate can also una}) 11.ingic3, d. H. in addition to or instead of the use in combination with an aggregate as a coating also alone as Impregnation agents or impregnation are used that apply to the surface of the Casting mold, the core or a similar foundry article to be treated is applied shall be. The application of the silicyl metaphosphate to the surface to be treated can be as described above for the application of the coating preparations methods or in any other suitable manner.

After application, the silicyl metaphosphate affects the surface of the treated area or the mold cavity in two ways: On the one hand the surface treated in this way is provided with a coating, which is a skin or has a thickness of about 25 to 75 micrometers; in addition, the silicyl metaphosphate penetrates under the treated surface to a depth of about 5 cm. The so treated casting mold or the core or similar foundry article shows after air drying properties similar to those of the coating formulation for about 20 minutes Surface treated with silicyl metaphosphate and refractory aggregate. Another An important aspect of the silicyl metaphosphate is its inert behavior towards Molten steel. It inhibits any adverse chemical reactions between the components of the mold or similar foundry items made with this substance are impregnated and certain components in the molten metal, such as titanium and Aluminum in molten steel, which could oxidize quietly in an undesirable manner. The silicyl metaphosphate also improves the radiographic properties of the casting by reducing it of the flaked part of the molding material that was poured into the casting would be embedded.

Another embodiment of the present invention can be for application a silicyl metaphosphate impregnation on a casting mold, a core or the like Foundry articles are used and are suitable for the manufacture of articles which impregnated all of the properties described above with a silicyl metaphosphate Own item.

This other embodiment is based on a two-step process, to avoid possible disadvantages caused by changes in storage manufactured silicyl metaphosphate impregnant. In this way of working a silicyl metaphosphate is applied to the treated surface simultaneously with the Application of the hybrid silicate applied first to the surface to be treated formed from a mixture of highly concentrated phosphoric acid and alcohol, as indicated below: Component% by weight (approximation) phosphoric acid (85%) 50-90 Ethanol or isopropanol (anhydrous) 10-50 to impregnate the casting mold Worked as follows: The mold was initially filled with a hybrid silicate preparation as mentioned in the first example above by brushing on, spraying on or after one treated with another suitable application method. After this treatment of the surface The mixture of phosphoric acid and isopropanol was then equal to the casting mold Apply it to the mold surface and allow the mold to air dry for about 20 minutes left what it was usable after.

It is understood from the above that the silicyl metaphosphate described herein for the treatment and manufacture of casting molds and similar foundry articles as Binding or impregnating agent used alone and without the addition of refractory aggregates can be. In particular, the silicyl metaphosphate can be used as a binder and as such with the molding sand or other comminuted refractory material when mixing the molding sand when preparing it for compaction to form a Casting mold are used. In this use, the silicyl metaphosphate in in an amount necessary to achieve the desired consistency of the mixture suitable is. A densified form produced with such a binder is shown a higher bond strength and fire resistance than the corresponding not so treated Foundry articles. Furthermore, the treated article shows all the properties of shapes and similar foundry articles made according to the above information using Silicyl metaphosphate has been manufactured or treated, such as more rapid air drying, higher raw strength and resistance to temperatures above 0 1650 C.

The term "egg hybrid silicate" as used herein means a silicate, how it z. B. is prepared according to the information in US Pat. No. 3,961,968. The designation As used herein, "silicate" means either a hybrid silicate or a silicyl metaphosphate. the The term "impregnate" here means a surface treatment or a material for treating or binding forms. The designations predetermined surface " or "surface part" means surface areas on which coatings or impregnates as shown in the figures can be applied and include z. B. the surfaces of the casting cavity 16, the riser cavity 17, of the inlet 18 and the main channel 20 of the form shown in Fig. 1 or the entire surface of the mold or of another treated foundry article.

The term "raw or wet strength" means the degree of hardness that of a moist or non-hardened casting mold or a similar foundry article is achieved to prevent the occurrence of cracking, crumbling or collapse of the fresh form to diminish.

Claims (22)

Claims 1. Preparation to be used for the treatment of foundry articles, in particular molds, characterized in that the preparation, by weight, contains (a) approximately 10-25% silicate, which is a hybrid silicate or a silicyl metaphosphate, and (b) refractory aggregate as the remainder. 2. Preparation according to claim 1, characterized in that the silicate is a mixture of an acidic colloidal silica sol, one with water miscible organic solvents and an alkyl silicate. 3. Preparation according to claim 1, characterized in that the silicate is a reaction product of an acidic colloidal silica, a water-miscible organic solvents and phosphoric acid. 4. Preparation according to one of claims 1-3, characterized in that that the refractory aggregate is chosen from zirconium, silicon dioxide, aluminum oxide silicates, Graphite, fused silica, alumina, chromite, fibrous alumina silicates and mixtures thereof. 5. preparation for use in the treatment of foundry articles, in particular forms, characterized in that the preparation, based on the By weight, contains (a) approximately 10-25% silicate, which is a hybrid silicate or a silicyl metaphosphate (b) up to approximately 3% of an additive which is a polyvinyl acetate, polyvinyl alcohol or clay, and (c) refractory aggregate as the remainder. 6. preparation for use in the treatment of foundry articles, in particular forms, characterized in that the preparation, based on the By weight, contains (a) approximately 10-25% of a silicate which is a hybrid silicate or is a silicyl metaphosphate, (b) up to approximately 3% surfactant, which is a sodium soap of fatty acid or a synthetic detergent, and (c) refractory aggregate as the rest. 7. preparation for use in the treatment of foundry articles, in particular forms, characterized in that the preparation, based on the By weight, contains (a) approximately 10-25% of a silicate which is a hybrid silicate or is a silicyl metaphosphate, (b) up to approximately 3% of an additive comprising a Polyvinyl acetate, polyvinyl alcohol, or clay, (d) up to approximately 3% surfactant, the is a sodium soap of fatty acid or synthetic detergent, and (c) refractory Aggregate as remainder. 8. Preparation for use in the treatment of foundry articles, in particular molds, characterized in that the preparation is the reaction product of the process with the following steps: (a) Mixing approximately 25-40% by weight of glycol ether of the formula (CnH2n + 1) OCH2CH2Oll , in which n = 1, 2, 3 n 2n + 1) OCH2CH2OH or 4, approximately 45-55% by weight of acidic colloidal silica sol containing at least about 30% available SiO2, and approximately 5-20% by weight of a hydrolyzed one organic silicate which contains at least about 40% available SiO2 and is an ethyl polysilicate, ethylene glycol monoethyl ether silicate, propyl silicate or butyl silicate, and (b) reacting approximately 5-25% by weight of phosphoric acid, which has a concentration of approximately 75-85%, with the mixture obtained in step (a) for the formation of silicyl metaphosphate of the formula in which n = 1, 2, 3 or 4. 9. Preparation for the treatment of foundry articles, in particular Forms, characterized in that they are a mixture of a preparation according to Claim 8 and a refractory unit contains. 10. preparation for use in the treatment of foundry articles, in particular forms, characterized in that the preparation is based on weight based, contains (a) approximately 10-25 8 of a preparation according to claim 8, and (b) refractory aggregate as the remainder. 11. Preparation according to claim 10, characterized in that the refractory aggregate is chosen from zirconium, silicon dioxide, aluminum oxide silicates, Graphite, fused silica, alumina, chromite, fibrous alumina silicates and mixtures thereof. 12. A method for producing a foundry mold or the like Article characterized by mixing a crushed refractory material with the preparation according to claim 8 and shaping the resulting mixture to the desired shape in a form. 13. Process for the treatment of foundry molds and similar articles, formed from compacted crushed refractory materials are marked by coating at least a predetermined surface portion of the mold with the Preparation according to claim 1, whereby the surface part with refractory Aggregate is coated and the silicate impregnates the surface part. 14. Processes for the treatment of foundry molds and similar articles, formed from compacted crushed refractory materials are marked by coating at least a predetermined surface portion of the mold with the Preparation according to claim 7, whereby the surface part with the refractory Aggregate is coated to a depth of approximately 0.3 to 0.8 mm and that Silicate impregnated the surface part to a depth of approximately 5 cm. 15. Foundry mold or similar article with a molded compact made of crushed refractory material and at least one predetermined surface part, which is coated with the preparation according to claim 1. 16. Foundry mold or similar article with a molded compact made of crushed refractory material and at least one predetermined surface part, which is coated with the preparation according to claim 4. 17. Foundry mold or similar article with a molded compact made of crushed refractory material and at least one predetermined surface part, which is coated with the preparation according to claim 7. 18. Foundry mold or similar article with a molded compact of crushed refractory material, the refractory material at least bound in the surface part of the pellet with the preparation according to claim 8 is. 19. Foundry mold or similar article with a molded compact made of crushed refractory material, the surface part with the preparation according to claim 8 is impregnated to a depth of about 5 cm. 20. Process for treating foundry molds or the like Articles formed from compacted crushed refractory materials, characterized in that at least a predetermined surface part of the to treated surface coated with a hybrid silicate and that then on the surface treated in this way is a mixture of approximately 10-90% highly concentrated Phosphoric acid and approximately 10-90% alkanol, such as isopropyl alcohol, to form one Silicylmetaphosphates is applied to the surface treated in this way. 21. The method according to claim 20, characterized in that the alkanol of the mixture is ethanol or isopropanol. 22. The foundry mold treated according to the method according to claim 20 or the like article with that formed on the treated surface Silicyl metaphosphate below this surface to a depth of approximately 5 cm extends.