KR20150006024A - Method for producing moulds and cores for metal casting and moulds and cores produced according to this method - Google Patents

Abstract

The present invention is as a mold material mixture for the above-mentioned production method preferably may be cured by at least one refractory material, and CO ₂ comprises a binder based on water glass relates to a process for the preparation of casting molds and casting simhyeong CO ₂ And is then cured by flushing with the second gas. The present invention also relates to a casting mold and a casting mold manufactured by the above-described manufacturing method.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a casting mold and a casting mold for metal casting, and a casting mold and a casting mold manufactured according to the above-

The present invention relates to a casting mold and a method for producing a casting mold wherein a mold material mixture comprising at least one refractory material and a binder capable of being cured with CO ₂ comprising or consisting of water glass, ₂ or CO ₂ and is cured by flushing with a second gas which does not contain CO ₂ but contains at least a small amount of CO ₂ . The present invention also relates to casting molds and casting cores produced according to this method.

Generally, refractory mold materials are provided in a fluid form, so that materials, such as quartz and suitable binders, are used to make cast molds and casting molds. The refractory mold material is preferably a mixture composed of a mold material and a binder, the so-called mold material mixture is filled into a suitable hollow mold and can be concentrated and cured therein. Since the bonding agent forms a tight bond between the particles of the mold material, the cast mold and the casting mold obtain the necessary mechanical stability.

During casting, the casting mold forms the outer wall for the casting, and the casting core is used when a hollow mold is required in the casting. The casting mold and the casting core need not necessarily consist of the same material. For example, at the time of chill casting, the outer mold shape of the casting is implemented with a metallic permanent mold. It is also possible to combine casting molds and casting cores produced in different ways. What has been described in connection with the casting cores is similarly applicable to castings (cast molds) produced by the same method and vice versa.

In order to produce the casting cores, an organic binder as well as an inorganic binder may be used, and the curing of the binder may be carried out by a low-temperature method or a high-temperature method, respectively. The low-temperature method generally refers to a method in which the molding apparatus used for the manufacture of the casting cores is carried out at room temperature, which is not heated.

The curing is carried out mostly through a chemical reaction, which is induced, for example, by penetration of the mixture of the moldings in which the gas is to be cured. In the case of high temperature processes, for example, to initiate a chemical reaction which releases the solvent contained in the binder and / or cures through, for example, cross-linking the binder, the mold material mixture may be heated by a molding device Lt; / RTI >

Curing of waterglass-based binders via CO2 is known, for example, from GB 654817. 50s and 60s of the 20th century, water glass -CO ₂ - How was widespread. One of the weaknesses of this method is that the casting cores manufactured in this way are relatively less robust immediately after being manufactured. Long gas treatment times, including CO ₂ , ensure high initial robustness, but at the same time, after 1-2 days in the storage depot, the robustness is weakened. With the relatively low initial rigidity and endurance robustness, the waterglass-CO ₂ -method only allows slow production to intermediate production speeds.

Thus, conventional CO ₂ -curing has been proposed to combine with the so-called "hot air procesess ", which is known in YAOwusu (YA Owusu, Ph.D.-Dissertation" Sodium Silicate Bonding in Foundry Sands ", Pennsylvania State University, May 1, 1980, pp. 88-102-103 and AFS Transactions, Vo. 89, 1981, pp. 47-54). The hot air process can be understood as oven curing associated with CO2 gas treatment. This has been demonstrated in YA Owusu's doctoral dissertation. This method has the disadvantage that it provides better strength than pure CO2-curing in at least some water glass binders, but takes a few seconds to several minutes to make the casting cores.

DE 102011010548-A1 discloses a process for curing a mixture of molding materials in combination with water glass, wherein an air penetration and a carbon dioxide gas-penetration combination are used. At this time, it has been confirmed that the mold material mixture must first be purged with air, and then with CO ₂ or air-carbon dioxide gas mixture. Also, a great significance of this invention is that the alkali silicate solution used has a weight ratio of SiO ₂ to metal oxide in the range of 1.5: 1 to 2.0: 1.

Another publication WO 80/01254 A1 discloses the method described above. This document discloses a method of curing a mixture of molding materials containing water glass, wherein the molding material mixture is heated at a temperature of 110 to 180 占 폚 and simultaneously penetrates through the CO ₂ and CO ₂ -air-mixture.

PL 129359 B2 discloses a binder for the production of casting molds for metal casting, the binder being composed of water glass and urea resin. Curing is carried out by flushing the mold material mixture with a CO ₂ -air-mixture. Preferably, the gas is heated to 60 to 200 占 폚. Another publication, CN 94111187 A, discloses the use of CO2-air-mixtures.

EP 2014392 B1 is known, and the use of spherical amorphous SiO ₂ in the said sphere is in the form of amorphous SiO ₂ is provided with more than two particle size classes (particle size class). EP 2014392 B1 does not disclose the use of a second gas stream and is provided with SiO ₂ in a dilute suspension and has disadvantages with respect to the (initial) strength of the mold body produced by the process according to the invention due to the increased water uptake.

As is now highly demanded, excellent strength over short curing times is required to ensure the processing of thin walled cast molds that become increasingly complex and at the same time ensure high productivity. Thus, the organic binder, in particular a so-called Ashland- polyurethane cold box - the introduction of the process based on how the water glass -CO ₂ - that is how quickly lose their meaning is not surprising.

All organic binder materials have the disadvantage that they can be thermally decomposed during casting and expose substances such as benzene, toluene or xylene which are hazardous. In addition, many organic binder systems are used as curing catalysts to release solvent or odor-causing gases when manufacturing and storing casting cores. Different measures have been taken to suppress all these emissions, but in the case of organic binders, these measures are useless.

For this reason, efforts to develop binders that are entirely based on inorganic binders, or that contain low proportions of inorganic binders, have increased in recent years. In order to achieve high strength in a short period of time, for example, a method has been proposed in which curing is carried out in a hot device and, in some cases, further hot air passes through the casting mold mixture, It is intended to discharge completely. Such systems are known, for example, from EP 1802409 B1 (US 7770629). However, this method has a disadvantage in that the apparatus must be heated, and since heating causes additional energy consumption, this method has a considerable cost burden.

It is an object of the present invention to provide a method by which a casting mold and a casting core can be produced in an unheated device using a binder which can be cured with CO2 based on an inorganic substance, The strength after removal from the apparatus is higher than the strength cured with the known CO2 until now without further heat treatment.

The above object of the present invention is solved by the features of claim 1. Preferred embodiments of the method according to the invention are subject of the dependent claims or are described below.

The surprising fact is that a casting core of excellent strength is obtained due to the combination of CO ₂ -curing, which includes flushing of the mixture of the moldings with the first gas and the second gas to be marked with flushing gas in the following. The first gas and the second gas may be provided before the second gas and vice versa, the order may be arbitrary, and the provision of the first gas and / or the second gas multiple times may be considered none. Preferably, the first gas is preferentially injected into the casting mold, preferentially and irrespective of the second gas.

In the following, the first gas indicated by CO ₂ - gas has a gas temperature during the gas treatment of 15 ° C to 120 ° C, preferably 15 ° C to 100 ° C, particularly preferably 25 ° C to 80 ° C. The gas temperature is related to the temperature at which the gas is introduced into the molding apparatus as in another description according to the present invention. The second gas is preferably 15 ° C to 120 ° C, particularly preferably 15 ° C to 100 ° C, and even more preferably 25 ° C to 80 ° C, but higher temperatures can often shorten the flushing time. There is no upper limit based on the curing mechanism. In practice, the temperature is between 40 ° C and 25 ° C, preferably between 50 ° C and 250 ° C, depending on the size of the casting mold and the casting core or casting mold. As the cost of high-power heaters required for high temperatures rises and the cost of efficient line shut-off is very high, contrary to the application of very high temperatures, financial reasons must first be addressed. For example, the temperature of the first gas Is approximately equal to the temperature of the second gas. Preferably, the temperature of the second gas is higher than the temperature of the first gas.

This measure has the advantage of acting inversely through the temperature regulation of the two gas streams with respect to cooling of the mixture of molding materials which can be observed in the gas treatment.

In the case of the known process, the use of a conventional heatable molding device is by no means impossible, and the process according to the invention can be used to cool the device cold, i. E. Between ambient and room temperature, It is possible to use it at a temperature lower than the service temperature, that is, at a temperature lower than 200 deg. C or 120 deg. C or lower than 100 deg. C, and a suitable device which can not be heated in particular can be used. Such a device can not be heated and can be heated through a thermally regulated inflow gas, although it does not itself have any heater device such as, for example, an electric heater. The process according to the invention does not preclude subsequent further heat treatment of the casting core and the casting mold.

The method according to the present invention comprises the following steps:

Manufacture of a mold material mixture consisting of at least one refractory mold material and preferably a bonding agent capable of being cured with CO ₂ based on water glass

- Manufacture of mold material mixture

- CO ₂ - penetrating mold material mixture into gas

- In some cases, alternating with CO ₂ - gas and flushing gas,

- the second gas (flushing gas) passes through the mold material mixture.

In the production of the mold material mixture, the refractory mold material is generally provided, and the binder is provided so as to be stirred. The binder is continuously stirred until it is uniformly distributed in the mold material.

The mold material mixture is then provided as a desired casting mold. Conventional methods are applied for mold shapes. For example, the molding material mixture can be shot into a molding device using a core-shooting device using compressed air. Subsequently, (in particular) curing is first carried out by passing the CO ₂ - gas through a device filled with the molding material mixture, and then flushing is carried out with the second gas. It is obvious to a person skilled in the art that the possibility of different embodiments for such a process exists.

For example, it is by no means absolute that pure CO ₂ (often desirable) is used as the CO ₂ - gas for the pre-curing. If possible, in order to achieve a short cure time, preferably CO ₂ - containing gas is at least 50% by volume of CO _2, preferably at least 80% by volume of CO _2.

Conversely, it is not absolute that the second gas does not completely contain CO ₂ , such as, for example, synthetic air or nitrogen. Air is preferred for cost reasons. 10% by volume, particularly preferably 5% by volume, particularly preferably 2% by volume or not more than 1% by volume of CO ₂ may be added to the flushing gas.

The transition from the CO ₂ -gas to the second gas should not be carried out in one step, and a stepwise or flexible transition may be possible. In addition, only one of the two gases, or only two of the gases, can be modulated to penetrate the molding compound mixture.

Another modification is that first, a portion of the water present in the casting material mixture is removed as a flushing gas by a brief gas treatment comprising a gas with low CO ₂ , then the binder is cured with CO ₂ - gas and, And the casting core is once again treated with a gas with low CO ₂ for drying.

The addition of CO ₂ is determined CO ₂ for CO ₂ gas may be carried out by controlling the flow or by a set gas pressure treatment. Whether or not the possibilities of the two possibilities can be applied in practice depends on several factors such as the geometry and size of the casting mold, the rigidity of the molding device, the gas inflow to the gas discharge, the gas penetration of the mold material, Diameter, binder content, desired gas treatment time, and the like. In order to optimize the characteristics, the gas treatment parameters can be adjusted according to the general knowledge according to the requirements of the person skilled in the art and the geometrical composition of the casting cores or the geometrical composition of the casting mold selected within the scope of the present invention. In general, the CO ₂ flow is selected from 0.5 L / min to 600 L / min, preferably 0.5 L / min to 300 L / min, particularly preferably 0.5 L / min to 100 L / min (standard liters each) do. According to another embodiment, the CO ₂ flow is from 0.5 L / min to 30 L / min, preferably from 0.5 L / min to 25 L / min, particularly preferably from 0.5 L / min to 20 L / min. This embodiment is particularly preferred at low gas temperatures of 15 [deg.] C to 40 [deg.] C for gases containing CO ₂ or CO ₂ .

For pressure control, the pressure of the CO ₂ gas is generally from 0.5 to 10 bar, preferably from 0.5 bar to 8 bar, particularly preferably from 0.5 bar to 6 bar.

In the case of air as flushing gas, the pressure present in the casting plant for practical reasons represents the upper limit for the gas treatment, since the gas can generally be drawn from a compressed air net present in the casting plant. The lower limit for effective gas treatment, including air, is about 0.5 bar. At low pressures, the gas treatment time becomes very long, which is associated with a loss of productivity.

Unless otherwise stated, the overall pressure substrate is each associated with an overpressure, i.e., a pressure that is less than the ambient pressure.

In the case of the ratio between the gas treatment of the first gas (CO ₂ -gas) and the second gas (flushing gas), the ratio is, for example, 2:98 to 90:10, preferably 2:98 to 20:80 , Particularly preferably from 5:95 to 30:70. The gas treatment time of CO ₂ should preferably not exceed 60%, particularly preferably 50% of the total gas treatment time, since it is also the object of the present application to keep the consumption of CO ₂ as low as possible with the improvement in strength do.

Through the appropriate choice of the gas treatment parameters and layout of the device, in the case of large cast cores, the production time corresponds to the production time of the organic binder, for example less than 3 minutes, preferably less than 2.5 minutes, particularly preferably 1 Min. Such optimization may be performed through computer simulation as the case may be.

The curing of the mold material according to the invention can be modified by providing a known method, for example a vacuum. In addition, the original curing process may be followed by another known procedure, such as heating in a microwave oven or oven.

Conventional materials as the refractory mold material can be used for cast mold production. Suitable materials include, for example, quartz sand, zircon sand or chrome light sand, olivine, vermiculite, borgite and sharp. It is not necessary to use only new sand. In the sense of reducing resource conservation and processing costs, it is desirable to use as high a percentage of the old sand as possible.

Suitable sand is for example known from WO 2008/101668 (= US 2010/173767 A1). At the same time, regenerated sand obtained through washing and subsequent drying is suitable. Recycled sand obtained through mechanical treatment may be used, but is not preferred. Generally, the regenerated sand may be replaced by at least about 70% by weight, preferably at least about 80% by weight, particularly preferably at least about 90% by weight of the new sand.

An artificial mold material can also be used as the refractory mold material, for example, a glass bead, a glass granule, a ceramic mold material in the form of spheres known under the name of "Cerabeads" or "Carboaccucast" Such quartz aluminum hollow microspheres are sold under the name "Omerga-Spheres " by Omega Minerals Germany GmbH with different qualities, for example with different contents of aluminum oxide. As a corresponding product PQ Corporation (USA) company's "Extendospheres".

The average diameter of the mold material is generally 100 탆 to 600 탆, preferably 120 탆 to 550 탆, particularly preferably 150 탆 to 500 탆. The particle size is determined, for example, by sieve analysis in accordance with DIN ISO 3310.

In aluminum casting experiments, it has been found that the use of artificial mold materials such as glass beads, glass granules or microspheres, among other things, makes the mold sand less sticky to the metal surface than the pure quartz sand after casting. Thus, the use of artificial casting materials allows for the production of a smooth casting surface and does not require, or at least a very small amount of, post-treatment with cost generating beams.

It is not necessary to form the entire mold material from the artificial mold material.

The preferred proportion of said artificial mold material is at least about 3% by weight, preferably at least 5% by weight, particularly preferably at least 10% by weight, particularly preferably at least about 15% by weight, Even more preferably at least about 20% by weight. Since the refractory mold material is preferably in a fluid state, the mold material mixture according to the present invention can be treated in a core shooter.

As another component, the molding material mixture according to the present invention comprises a binder based on water glass. As the water glass, ordinary water glass can be used, which is the same as that which has hitherto been used as a binder in a molding material mixture.

The water glass is an aqueous solution of an alkali silicate, especially lithium silicate, sodium silicate and potassium silicate, and is used as a binder in other fields, for example in buildings. For example, at a temperature of 1350 ° C to 1500 ° C, and is manufactured industrially in large scale through melting of quartz sand and alkali carbonate. The water glass is initially provided in the form of a large lump of solid glass, which is dissolved in water through temperature and pressure. Another method for producing the water glass is to directly dissolve the quartz sand in sodium hydroxide.

The obtained alkali silicate solution can then be adjusted to the desired molar ratio of SiO ₂ / M ₂ O through alkali hydroxide and / or alkali oxide and hydrate addition as described above. In addition, the alkali silicate solution composition can be controlled through dissolution of the alkali silicate with another composition. Alkali silicates containing water provided in solid form together with the alkali silicate solution are also provided, such as the product family Kasolv, Britesil or Pyramid of PQ Corporation.

The binder can be based on water glass, which contains more than one of the mentioned alkali ions, for example a modified lithium water glass known from DE 2652421 A1 (= GB 1532847). The water glass may also contain ions of multiple valences, for example boron or aluminum (e. G. EP 2305603 A1 (= corresponds to WO 2011/042132 Al).

The water glass preferably has a molar ratio of SiO ₂ / M ₂ O of 1.6 to 4.0, particularly preferably 2.0 to less than 3.5, and M represents lithium, sodium or potassium.

 The water glass preferably has a solids content of greater than or equal to 30% by weight, particularly preferably greater than or equal to 33% by weight, particularly preferably greater than or equal to 36% by weight. The upper limit for the solids content of the water glass is preferably less than or equal to 65% by weight, particularly preferably less than or equal to 60% by weight, particularly preferably less than or equal to 55% by weight. The solids ratio is determined on a Satorius MA30 Moisture Analyzer, and about 3-4 g of binder is heated to a constant weight at 140 DEG C in an aluminum dish (diameter = 10 cm, height = 0.7 cm).

In addition, the water glass has a calculated solids content as M ₂ O and SiO ₂ in the range of 25 to 65 wt.%, Preferably 30 to 60 wt.%. The solids ratio calculated as SiO ₂ and M ₂ O is related to the amount of alkali silicate contained in the water glass.

0.5 to 5% by weight, preferably 0.75 to 4% by weight, particularly preferably 1 to 3.5% by weight of the binder based on water glass, depending on the use and the desired strength level, Is used. The substrate is associated with a water glass containing a solid ratio as described above, and the diluent comprises water together.

With respect to the amount of alkali silicate calculated as M ₂ O and SiO ₂ added with the inorganic binder for the mold material according to the present invention which does not take diluent into consideration, the amount of binder used for the mold material is 0.2 to 2.5 wt% , Preferably 0.3 to 2% by weight, and M ₂ O has the above-mentioned meanings.

Preferably, the molding material mixture comprises a metal oxide in the form of a particulate, the metal oxide being selected from the group consisting of silicon dioxide, aluminum dioxide, titanium dioxide and zinc oxide and mixtures or mixed oxides of the foregoing, in particular silicon oxides, And / or an alumosilicate. The particle size of such a metal oxide is preferably 300 [mu] m, particularly preferably 200 [mu] m, more preferably less than 100 [mu] m and has a primary particle size of, for example, 0.05 [mu] m to 10 [

Particle size can be determined through sieve analysis. Particularly preferably, the sieve residue in the sieve of 63 mu m mesh size is less than 10% by weight, preferably less than 8% by weight. Particularly preferably, silicon dioxide is used as the metal oxide in the form of particles, and the amorphous silicon dioxide synthesized here is particularly preferred.

Precipitated silica and / or pyrogenic silica is preferably used as the silicon dioxide in particle form.

Optionally, the molding material mixture may comprise amorphous SiO ₂ . It is believed that the addition of amorphous SiO ₂ to the mold material mixture has a positive effect in the case of CO ₂ -gas and flushing gas according to the invention as well as in the case of thermosetting known in EP 1802409 B1 (= US 7770629) The facts were confirmed. For the initial strength, the increase in strength is significantly higher than when the binder content is increased in the same amount, while in the case of the final section strength, the higher binder content has a favorable effect and can be selected according to the desired effect.

The amorphous SiO ₂ preferably used according to the invention has a water content of less than 15% by weight, particularly preferably less than 5% by weight, particularly preferably less than 1% by weight. In particular, the amorphous SiO ₂ is used as a powder.

Natural silicate as well as silicate synthesized as the amorphous SiO ₂ may be used. The latter is known, for example, from DE 102007045649, which is not preferred because it contains a low crystallinity and is thus classified as a carcinogen.

Synthesis is understood as non-naturally occurring amorphous SiO ₂ , the preparation of which involves chemical reactions, for example silica sol from ionic exchange from an alkali silicate solution, precipitation from an alkali silicate solution, Flame hydrolysis of silicon, or synthesis of coke and quartz sand in an electric furnace during the production of ferrosilicon and silicon. The amorphous SiO ₂ prepared according to the last two methods is named pyrogenic SiO ₂ .

Sometimes, synthetic amorphous SiO ₂ can be understood as precipitated silica (CAS-Nr. 112926-00-8) and SiO ₂ (pyrogenic silica, Fumed Silica, CAS / Nr. 112945-52-5) , Whereas only the materials produced in the manufacture of ferrosilicon and silicon are referred to as amorphous SiO ₂ (Silica Fume, Microsilica, CAS-Nr. 69012-64-12). For purposes of the present invention, the materials produced in the production of ferrosilicon and silicon can also be understood as synthetic amorphous SiO ₂ .

Preferably, the precipitated silica and the exothermic SiO ₂ produced in flame hydrolysis or electrospray are used. Preferably, (see DE 102012020510) (see DE 102012020509) an amorphous SiO ₂ produced by thermal decomposition of ZrSiO ₄ and SiO ₂ produced a gas containing oxygen through the oxidation of the metallic Si as means is used . Preferably, quartz sand powders (mainly amorphous SiO ₂ ) produced through melting and rapid re-cooling from crystalline quartz are used so that the particles are provided spherically and are not provided with debris (see DE 102012020511). The average particle size of the synthetic amorphous silicon dioxide is 0.05 탆 to 10 탆, preferably 0.1 탆 to 5 탆, particularly preferably 0.1 탆 to 2 탆. Particle size was determined using a Horiba LA 950 nanoparticle analyzer and was tested by electron microscopy of the Nova NanoSEM 230 from the FEI company. In addition, the REM-photographing can be used to identify the particle morphology in detail up to 0.01 mu m. The SiO ₂ sample is dispersed in distilled water for REM measurement and then provided in an aluminum holder bonded with a copper band before water evaporates.

In addition, the specific surface of the synthetic amorphous silicon dioxide is determined through the measurement of the gas adsorption action (BET-scheme) according to DIN 66131. The synthetic amorphous SiO ₂ is preferably 1 to 200 m ² / g, particularly preferably 1 to 50 m ² / g, even more preferably 1 to 30 m ² / g. Optionally, the resulting material may be mixed to obtain the desired mixture having a defined particle size distribution.

The amorphous SiO ₂ type described above forms a slightly larger aggregate due to agglomeration. It is important for the uniform distribution of the amorphous SiO ₂ in the mold material mixture that when blended, the aggregate partially breaks back into smaller units or does not exceed a predetermined size from the beginning. Preferably, when penetrating through a sieve having a mesh size of 45 μm, the remainder - to describe the degree of agglomeration - is preferably less than about 10% by weight, particularly preferably less than about 5% by weight, By weight is less than about 2% by weight.

Depending on the manner of manufacture and the manufacturer, the purity of the amorphous SiO ₂ can vary widely. Preferably at least 85% by weight, particularly preferably at least 90% by weight, particularly preferably at least 95% by weight.

Used and according to the desired power level, preferably 0.1% to 2% by weight of the particles form amorphous SiO _2, especially preferably from 0.1% to 1.8% by weight, still more preferably 0.1 with respect to the casting mold form By weight to 1.5% by weight.

The ratio of the water glass binder to the amorphous SiO ₂ can be varied within other limits. This has the advantage that the initial strength of the casting core, that is, the strength immediately after being removed from the molding apparatus is improved, does not affect the strength of the end portion. Above all, this shows considerable interest in light metal casting. On the other hand, a high initial strength is required to carry the casting cores without problems after their manufacture, or to combine them into full coarse corrugated packets, and on the other hand, the ending strength should not be high to suppress the difficulty of breaking the casting cores after casting .

With respect to the weight of the binder, the amorphous SiO ₂ preferably has a proportion of from 2 to 60% by weight, particularly preferably from 3 to 55% by weight, particularly preferably from 4 to 50% by weight, The solid content ratio of water glass to amorphous SiO ₂ is 10: 1 to 1: 1.2 (parts by weight).

The addition of the amorphous SiO ₂ is carried out not only before and after the addition of the binder to the refractory material according to EP 1802409 B1, but also with at least binder or sodium hydroxide, as known in EP 1884300 A1 (= US 2008/029240 A1) A premix of SiO ₂ may be prepared, and then such premix may be added to the refractory material. Optionally, the binder and binder ratios that are still present but not used for the premix may be added to the refractory material before or after the addition of the premix, or may be added to the refractory material together with the premix . Preferably, the amorphous SiO ₂ is added directly to the refractory material prior to addition of the binder.

Without limiting the foregoing, the inventors believe that a strong alkaline water glass can react with a silanol group arranged on the surface of the amorphous silicon dioxide, and when the water evaporates, a strong bond between the silicon dioxide and the hard water glass Can be formed.

In yet another embodiment, barium sulfate may be added to the casting material mixture to improve the casting surface, particularly in light metal casting, such as aluminum casting. The barium sulfate may be natural barium sulfate as well as synthesized barium sulfate, and may be added in the form of a mineral including barium sulfate such as barite or barite. These or other features of a suitable blend of barium sulphate and barium sulphate are described in detail in DE 102012104934, the disclosure of which is hereby incorporated by reference into the present disclosure.

With respect to the total mold material mixture, the barium sulphate is preferably added in an amount of 0.02% by weight, particularly preferably 0.05 to 0.99% by weight, particularly preferably 0.1 to 2.0% by weight.

According to yet another embodiment, the mold material mixture according to the invention can be added with another material, characterized in that the material is less wetted with molten aluminum, such as boron nitride.

Such a mixture of less wetted materials comprising barium sulphate as the less wetted media can likewise form a smooth, sand-free casting surface. With respect to the total amount of undiluted / less wetted material, the content of barium sulphate should be greater than 5 wt%, preferably greater than 10 wt%, particularly preferably greater than 20 wt% or greater than 60 wt%.

The upper limit represents pure barium sulphate, in which case the content of barium sulphate in the non-wetted medium is 100% by weight. Mixtures of undiluted material / wetted material, in particular barium sulfate, are preferably present in an amount of 0.02 to 5.0% by weight, particularly preferably 0.05 to 3.0% by weight, particularly preferably 0.1 to 5% by weight, 2.0% by weight or 0.3 to 0.99% by weight is added.

In yet another embodiment, the additive component of the molding material mixture according to the present invention may comprise a particulate metal oxide or mixed particulate metal oxide of aluminum or the above-mentioned metal oxide of aluminum and zirconium, which is described in DE 102012113073 or DE 102012113074. With such additives it is possible to obtain castings consisting of iron or steel after metal casting, in particular of iron or steel with very high surface quality, so that only a small post-treatment of the casting surface after casting mold removal may be required, or post- .

The particulate metal oxide or mixed particulate metal oxide does not react at all or at least very little reaction affinity with the inorganic binder, especially alkaline water glass, at room temperature.

The particulate metal oxide comprises or consists of at least one aluminum and / or silicon mixed oxide, in particular in the alpha-phase, excluding aluminum / silicon mixed oxides having at least one aluminum oxide and / or a layered silicate. The particulate metal oxide comprising at least one aluminum and / or silicon mixed oxide other than aluminum / silicon mixed oxide having at least one aluminum oxide and / or a layered silicate in the alpha-stage means pure aluminum oxide or pure alumosilicate Or a mixture of the aforementioned metal oxide and another oxide, for example zirconium, as well as the particulate metal oxide composed of aluminosilicate, and the zirconium may be an aluminum / silicon-mixed oxide or a mixture of several different And in particular, said mixed material consists of at least two of the two above-mentioned solids and phases: solids containing aluminum oxide and solids and / or solids and / or aluminum / silicon oxides containing phase.

Preferably, the particulate metal oxide is selected from the group consisting of zirconium oxide + zirconium dioxide, zirconium mullite, zirconium oxide and alumium silicate (excluding those having a layered silicate structure) + zirconium dioxide, Lt; / RTI >

Aluminum / silicon-metal oxides having a layered structure are not suitable as additives for the binder, for example, meta kaolin, kaolin and aged silica. Also, exothermic amorphous aluminum oxide is not suitable.

The particulate mixed metal oxide is at least a particulate mixture of particulate mixed oxides or at least two oxides, or is provided as a mixed oxide which is at least particulate mixed together with at least another particulate oxide, and comprises at least zirconium oxide.

The metal oxide mixed with the aluminum oxide and the zirconium oxide in the form of particles in combination with each other can be understood not only as pure aluminum oxide and zirconium oxide but also as a mixed oxide and can be exemplified by aluminum silicate and zirconium oxide Or a plurality of phases. In particular, the mixed material is composed of a solid and a phase containing one or more aluminum oxide and zirconium oxide.

Preferably, the particulate mixed metal oxide according to the present invention is at least one selected from the group of a) grit + zirconium oxide, b) mullite zirconium, c) zirconium zirconium and d) aluminosilicate + zirconium oxide And may also include other metal oxides as the case may be.

Aluminum silicate can be understood not only as an alumosilicate but also as an aluminosilicate.

It is preferably a partial silicate, as well as an aluminum / silicon-mixed oxide, when the aluminum silicate is not atypical (i. E., Provided by crystallinity or particle determination). In the case of partial silicates, the SiO 4 units (tetrahedrons) contained in the structure are not provided in direct bonding with each other (they are not Si-O-Si bonds) and instead tetrahedral SiO ₄ units contain one or more Al- (Si-O-Al). The Al-atom is coordinated with oxygen atoms of 4.5 and / or 6.

Typical of these partial silicates ( Systematic der minerale For example, mullite (molten mullite and sintered mullite are here considered to be the same as mullite containing ZrO ₂ ) and silylmanite and silymarinite groups (for example, according to nach Strunz , 9 Auflage) , Kyanite or Hongyu), and from this silylmanite group, particularly preferably, Kyanite is used.

Silicon atoms and aluminum atoms in an amount of more than 50 atomic% with respect to the total of aluminum atoms, and in some cases, zirconium / zirconium oxide or zirconium oxide is produced as a by-product in the manufacture of zirconium oxide, Particularly preferred are amorphous aluminum silicates (excluding the layered silicate structure) comprising dust containing aluminum.

Other characteristics of aluminum or of a suitable particulate metal oxide or of a particulate mixed metal oxide of aluminum and zirconium are described in detail in DE 102012113073 and DE 102012113074, the disclosures of which are also incorporated herein by reference.

The particulate amorphous silicon dioxide added to the mold material mixture for increasing the strength may be added as part of the metal oxide mixed in the particle form or may be added separately.

In this case, the description for the concentration of the particulate mixed metal oxide and the particulate amorphous silicon dioxide can be understood to be different from each other. It is doubtful that a component can be derived from the foregoing.

In yet another embodiment, the additive component of the molding material mixture according to the present invention may comprise a compound containing phosphoric acid. Such addition is desirable in the case of very thin wall sections of the casting mold and in particular in the case of casting cores because it can increase the thermal stability of the thin wall section of the casting mold and the casting mold in this way. This is particularly important when the liquid metal abuts the inclined surface during casting and there is a strong erosion action due to the high metallostatic pressure described above or in particular where deformation of the thin wall cross section of the casting mold can be caused . Suitable phosphoric acid compounds do not affect or significantly affect the processing time of the molding compound mixture according to the invention. Suitable representatives and amounts added are described in detail in WO 2008/046653 A1, which is also incorporated herein by reference.

Binders containing water have poor flowability compared to binders based on organic solvents. This means that a molding device with a narrow passage and multiple redirection points can not be filled well. As a result, the cast core may have a cross-section with sealing defects, which may cause casting defects again in casting. According to a preferred embodiment, the mold material mixture according to the invention comprises a part of a flaky lubricant, in particular graphite or MoS ₂ . Surprisingly, it has been found that such lubricants, particularly composite casting molds with thin wall cross sections upon graphite addition, can be produced and that the casting molds are always uniformly high in density and strength, to be. The amount of the plate lubricant, particularly graphite, added is preferably 0.05 wt% to 1 wt% with respect to the mold material.

Surfactants, especially surfactants, can be used at the plate lubricant point, and the surfactant improves the flowability of the molding material mixture. Representative of such compounds are known, for example, in WO 2009/056320 (= US 2010/0326620 Al). Surfactants which include in particular sulfuric acid groups or sulfonic acid groups are mentioned here.

The mold material mixture according to the invention together with the above-mentioned ingredients may comprise further additives. For example, an internal release agent may be added, which facilitates separating the casting mold from the molding apparatus. Suitable internal mold release agents include, for example, calcium stearate, fatty acid esters, waxes, natural resins or special alkyd resins.

What is surprising is the fact that the addition of organic additive improves the quality of the casting surface, especially in aluminum casting. The mechanism of action of the organic additive is not described. Without being bound by this rationale, the inventor believes that during the casting process, a portion of the organic additive is burnt, wherein a thin gas cushion is created between the liquid metal and the mold material forming the walls of the casting mold, and between the liquid metal and the mold material Can be suppressed. The inventor can also assume that a portion of the organic additive forms a thin layer of the aforementioned anthracite material composition under a reducing atmosphere during the course of casting and the anthracite- . As another preferred effect, the increase in the strength of the casting mold after curing can be achieved through the addition of the organic additive.

Surprisingly, the quality improvement of the casting surface can be achieved with very different organic additive. Suitable organic additive additives include, for example, phenol-formaldehyde resins such as novolak, epoxy resins such as bisphenol-A-epoxy resins, bisphenol-F-epoxy resins or epoxidized novolaks, polyols such as polyethylene glycol or polypropylene glycol , Glycerol or polyglycerol, polyolefins such as polyethylene or polypropylene, copolymers composed of olefins such as ethylene or propylene and other comonomers such as vinyl acetate or styrene and / or diene monomers, polyamides such as polyamide-6, Polyamide-12 or polyamide-6,6, natural resins such as balsamic resin, fatty acid esters such as cetyl palmitate, fatty acid amides such as ethylenediamine bisstearamide, carbohydrates such as dextrin and metal soaps such as stearates, Oleic acid of a trivalent metal have. The organic additive may be contained as a pure substance or may be included as a mixture of different organic compounds.

The organic additive preferably comprises 0.01 to 1% by weight or 0.1 to 1.0% by weight, particularly preferably 0.05 to 0.5% by weight, particularly preferably 0.1 to 0.2% by weight, relative to the solid .

-아미노프로필-트리메톡시실레인, 3-우레이도프로필트리톡시실레인,

-메르캅토프로필트리메톡시실레인,

-글리시독시프로필트리메톡시실레인, β-(3,4-에폭시시클로헥실)트리메톡시실레인 및 N-β(아미노에틸))-

-아미노프로필트리메톡시실레인이 있다. 결합제와 관련하여 일반적으로 0.1 내지 2 중량%, 바람직하게는 0.1 내지 1 중량%의 실레인이 사용된다.Silane may also be added to the mold material mixture according to the present invention to increase the strength of the cast mold and the cast core against high humidity and / or water-based mold material coatings. According to another preferred embodiment, the molding material mixture according to the invention comprises at least one part of silane. Suitable silanes are, for example, amino silanes, epoxysilanes, mercaptosilanes, hydroxysilanes and ureidosilanes. An example of a suitable silane is

-Aminopropyl-trimethoxysilane, 3-ureidopropyltriethoxysilane,

- mercaptopropyltrimethoxysilane,

(Glycidoxypropyltrimethoxysilane,? - (3,4-epoxycyclohexyl) trimethoxysilane and N -? (Aminoethyl)) -

-Aminopropyltrimethoxysilane. ≪ / RTI > In relation to the binder, generally from 0.1 to 2% by weight, preferably from 0.1 to 1% by weight, of silane is used.

Another suitable additive is an alkali metal silicone, such as potassium methysilicon, with 0.5 to 15% by weight, preferably 1 to 10% by weight, particularly preferably 1 to 5% by weight, with respect to the binder have. If the molding material mixture comprises an organic additive, the addition of the organic binder may itself be carried out at any time for preparing the molding compound mixture. The addition of the organic binder may be used in the form of a substance or solution. When the organic additive is soluble in the binder and stably stored for several months without decomposition in the binder, the organic additive may be dissolved in the binder and added to the mold material together with the binder. The water-insoluble additive may be used in the form of a dispersion or a paste. The dispersion or paste preferably comprises water as a liquid medium.

If the casting material mixture comprises silanes and / or alkaline methylsilanes, the addition of these is carried out in such a way that the silanes and / or alkaline methylsilanes are mixed into the preferential binder. The silane and / or alkali methyl silane may be added to the casting material as a separate component.

Mineral additives can also positively influence the properties of the casting cores produced by the process according to the invention. For example, AFS Transactions, Vol. 88, pp 601-608 (1980), or Vol. 89, pp 47 - 54 (1981) raise the moisture resistance of the casting cores when storing the casting cores, while the phosphate compounds known in WO 2008/046653 (= CA 2666760 A1) Increases heat resistance.

In manufacturing the mold material mixture, the refractory mold material is provided to the mixer, and then preferably the liquid component is added and mixed with the refractory mold material until a uniform layer of binder is formed on the particles of the refractory mold material do. The mixing time is selected so as to effect intimate mixing of the refractory mold material and the liquid component. The mixing time depends on the amount of the molding material mixture to be produced and the mixing apparatus used. Preferably, the mixing time is selected between 1 minute and 5 minutes. For another preferred stirring of the mixture, the solid component is added in the form of a particulate mixed metal oxide, and optionally in the form of amorphous silicon dioxide, barium sulphate or another powdery solid, followed by continued mixing. Also, the mixing time here depends on the amount of the molding material mixture to be produced and the mixing apparatus used. Preferably, the mixing time is selected between 1 minute and 5 minutes. In the case of a liquid component, it can be understood as a whole of all the individual liquid components as well as the mixing of different liquid components, the latter being added together or sequentially to the molding material mixture. According to another embodiment, a solid component may first be added to the refractory mold material, and then a liquid component may be supplied to the mixture.

The mold material mixture is then provided in a desired casting mold. At this time, the conventional method is applied for the mold shape. For example, the mold material mixture can be shot into a molding apparatus using a core shooting apparatus using compressed air. Another possibility is to allow the mold material mixture to flow freely from the mixer to the molding device and to seal the mold material mixture by vibration, stamping or pressing in a molding device.

The process according to the invention is itself suitable for the manufacture of all common casting molds, for example casting cores and casting molds, for metal casting.

Notwithstanding the high strength that can be achieved with the method according to the invention, the casting cores made from the casting material mixture according to the invention exhibit good separation after casting, especially in aluminum casting. The use of a mold body made of a mold material mixture according to the present invention is not limited to light metal casting. Casting molds are generally suitable for metal casting. Such metals include, for example, non-ferrous metals such as brass, bronze, and ferrous metals.

The present invention is described in more detail as follows in the following non-limiting examples.

Example

1. Preparation of mold material mixture

1.1. No addition of amorphous SiO ₂

Silica H32, corresponding to 5 kg each of Quarzwerke Frechen GmbH, Hobart (Modell HSM 10). The binder was then added with stirring and mixed intensively with the sand for one minute. Each addition amount was recorded in each experiment.

1.2. Amorphous SiO ₂ addition

0.5 GT amorphous SiO ₂ was added to the sand and added to the sand for one minute before adding the binder as in 1.1. The form of addition was recorded in each experiment.

2. Manufacturing and Testing of Test Specimens

Parts of the mold material mixture prepared according to 1.1 and 1.2 are described in Fa. Roeperwerke AG, the company's core shooter, H1. The remainder of the casting material mixture was kept in a carefully closed container to protect it from being dried until refilled in the core shooting apparatus and to prevent premature reaction with CO ₂ present in the air. The mold material mixture is supplied from the reservoir with compressed air (4 bar) and is provided with two concave grooves for a round casting mold having a diameter of 50 mm and a height of 50 mm, . Following the above, the test casting core was cured. Details of this were recorded in each experiment. After curing, the specimen was separated from the molding device by spun and the pressure strength of the specimen was measured immediately after storage for up to 15 seconds, 24 hours after separation, with a Zwick Universal prism panel (Modell Z 010). The values in the table refer to the median value of each of the eight casting cores. To avoid possible climate change effects, all specimens used for strength measurements for 24 hours were stored in a temperature control room provided with a temperature of 23 ° C and a humidity of 50%.

In the case of Examples 4.01 to 4.07, The heating tubes of the Hillesheim GmbH company (Modell HT42-13) are available from La. Laempe & Moessner GmbH, the company's core shooter, L1. To test the mold material mixture, a rectangular test bar having dimensions of 150 mm x 22.36 mm x 22.36 mm was produced (so-called Georg-Fischer-Riegel). The three-part molding device used allows four square test bars to be manufactured simultaneously. A part of the mold material mixture prepared according to 1.2 was transferred to the reservoir of the core shooting apparatus and the molding apparatus of the core shooting apparatus was not electrically heated. The remainder of each casting material mixture was kept in a carefully closed container to protect it from being dried until it was refilled in the core shooting device and to prevent premature reaction with CO2 present in the air. The mold material mixture was inserted into the molding apparatus from the reservoir using compressed air (4 bar) and flushed with hot Co2 and hot air. Another description of flushing time and gas temperature of compressed air and CO2 is given in Table 6. After curing, the molding apparatus was opened and the test bar removed.

To measure the bending strength, a force was applied to a Georg-Fischer-strength measuring instrument equipped with a 3-point-bending device, and the force at which the test bar was broken was measured. The bending strength was measured directly after removal (initial strength), not only for up to 15 minutes, but also for about 24 hours after manufacture (end strength).

The strength test results are shown in Table 4. The values described here correspond to the median value of at least four casting cores measured several times.

3. Curing with CO ₂

3.1. A mold material mixture consisting of quartz sand H32, 2.0 GT (GT = parts by weight), 2.5 GT or 3.25 GT of sodium water glass having a molecular weight of about 2.33 and a solids content of about 40% by weight was used for the preparation of the test piece. CO ₂ (manufacturer and purity respectively: Linde AG, at least 99.5% by volume CO ₂ ) penetrated the molding material mixture for curing. The temperature of the gas when it was introduced into the molding device was between 22 and 25 ° C. Table 1 lists the gas treatment times, CO 2 -flow and compressive strength found under these conditions (Examples, 1.01 to 1.21 and 1.29 to 1.41).

3.2. Part of the experiment corresponding to 3.1. Was repeated with the difference that 0.5 GT irregular silicon dioxide was mixed in the form of powder in the mold material mixture before the binder addition. The results are likewise described in Table 1 (for example, 1.22 to 1.28).

In Table 1 (see Appendix):

Atypical SiO _{2 Not} added:

The strength depends on the amount of CO ₂ used for curing, the initial strength increases with the increased amount of CO ₂ , while the strength after 24 hours storage due to the known excess gas treatment effect is reduced (Example 1.01 To 1.21), the excess gas treatment effect occurs later as expected in the case of higher binder ratios.

In the case of a uniform absolute CO ₂ amount, low CO ₂ flow affects very early strengths very positively, whereas high CO ₂ flows positively affect end strength (Examples 1.03 / 1.08, 1.04 / 1.09 / 1.15, 1.05 / 1.16, 1.06 / 1.11 / 1.17, 1.07 / 1.12 / 1.18, 1.14 / 1.20).

Atypical SiO ₂ addition:

The addition of amorphous SiO ₂ is affected, but the curing of the same gas treatment parameters, increased strength for casting simhyeong which does not include the amorphous SiO ₂ (see Example 1.22 to 1.28 as compared to the embodiment 1.08 to 1.14).

After storage for 24 hours with excess gas treatment, the strength loss is reduced through the irregular SiO ₂ (see Examples 1.22 to 1.28 in comparison with Examples 1.08 to 1.14).

In addition to the long gas treatment time, the addition of amorphous SiO ₂ results in a stronger initial strength increase than when the binder content is increased by the same amount. On the contrary, when the binder content is increased, the strength of the end zone is strongly increased, but when the gas treatment time is prolonged, it strongly decreases again due to the effect of excess gas treatment (see Examples 1.22 to 1.28 in comparison with Examples 1.29 to 1.35) .

Also, for a uniform solids content, the mixture consisting of a water glass binder and atypical SiO2 has advantages in terms of initial strength as compared to the amount of amorphous SiO2-free binder besides the long gas treatment time. In the case of the end strength, the amount of binder increased inversely affects strongly, and in the case of a long gas treatment time due to excess gas treatment, the strength again decreases strongly (see Examples 1.22 to 1.28 in comparison with Examples 1.36 to 1.42) .

4. Air hardening

4.1. A mixture of molding materials consisting of quartz sand H32, 2.0 GT, 2.5 GT or 3.25 GT of sodium water glass having a particle size of about 2.33 and a solids content of about 40% by weight was used for the preparation of the test piece. Compressed air penetrated the mold material mixture for curing. The temperature of the compressed air when entering the molding apparatus was 22 to 25 占 폚. Table 2 lists the gas treatment time, the gas treatment pressure and the compressive strength found under these conditions (Examples, 2.01 to 2.03 and 2.07 to 2.06).

 4.2. Part of the experiment corresponding to 4.1 was repeated with the difference that 0.5 GT irregular silicon dioxide was mixed in powder form in the mold material mixture before the binder addition. Similarly, the results are shown in Table 2 (for example, 2.04 to 2.06).

Table 2 (see Appendix):

Atypical SiO _{2 Not} added:

The strength is dependent on the amount of air penetrated, and the initial strength increases strongly with the increased air content than the end strength (see Examples 2.01 to 2.03 and 2.07 to 2.12).

The increased amount of binder inevitably produced no better strength. As a guess, this can be explained by the good sealing power and the increased amount of water in the mold material mixture (see Examples 2.01 to 2.03 in comparison with Examples 2.07 to 2.12).

Atypical SiO ₂ addition:

The addition of amorphous SiO ₂ have been cured in the same gas treatment parameters affect the strength increased for the casting simhyeong which does not include the amorphous SiO _2, the early strength of the end game strength (example 2.01 to Example 2.04 as compared to 2.03 0.0 > 2.06). ≪ / RTI >

The increase in strength due to atypical SiO ₂ is greater than when the binder content is increased by the same amount (see Examples 2.07 to 2.09 in comparison with Examples 2.04 to 2.06).

The increase in strength due to atypical SiO ₂ is greater than when the binder content is increased to the same solids content (see Examples 2.10 to 2.12 compared to Examples 2.04 to 2.06).

5. Hardening through air bonding with CO ₂

5.1. A mixture of molding materials consisting of quartz sand H32, 2.0 GT, 2.5 GT or 3.25 GT of water glass with a particle size of about 2.33 and a solids content of about 40% by weight was used for the preparation of the test piece. For curing, CO ₂ and then compressed air penetrated the mold material mixture. The temperature of the two gases when introduced into the molding apparatus was between 22 and 25 ° C.

Table 3 shows the gas treatment times of CO ₂ and air, CO ₂ flow, gas treatment pressure (air) and the compressive strength found under these conditions (Examples, 3.01 to 3.09, 3.19 to 3.27, 3.37 to 3.45) ).

5.2. Part of the experiment corresponding to 5.1 was repeated with the difference that 0.5 GT irregular silicon dioxide was mixed into the mold material mixture in powder form before the binder addition. Similarly, the results are shown in Table 3 (see Examples 3.10 to 3.18, 3.28 to 3.36 and 3.46 to 3.48).

5.3. A portion of the experiment corresponding to 5.1 was repeated with the difference being heated to a temperature of approximately 100 캜 measured when the compressed air passing through the molding material mixture was introduced into the molding apparatus. The results are likewise described in Table 3 (see Examples 3.49 to 3.51).

5.4. Part of the experiment corresponding to 5.2 was repeated with the difference being heated to a temperature of approximately 100 캜 measured when the compressed air passing through the molding material mixture was introduced into the molding apparatus. The results are likewise described in Table 3 (see Examples 3.52 to 3.54).

In Table 3 (see Appendix):

Atypical SiO _{2 Not} added:

Combined CO ₂ / air gas treatments generally result in better strength than when gas treated with CO ₂ or air alone (see Examples 3.01 to 3.09 compared to Examples 1.01 to 1.21 and 2.01 to 2.03).

Increasing the pressure during gas treatment with air causes another increase in strength (see Examples 3.43 to 3.45 in comparison with Examples 3.04 to 3.06).

Heating of the gas treated air affects an increase in the end zone strength (see Examples 3.49 to 3.51 compared to Examples 3.04 to 3.06). The failure of the initial strength to exhibit the same effect can be explained as the initial strength was heated at the time of the strength test.

Prolonging the gas treatment time with CO ₂ does not positively affect all cases of strength depending on the effect of the excess gas treatment (see Examples 3.01 to 3.09 and 3.19 to 3.27).

The increased binder content affects high end strengths and does not inevitably affect high initial strengths. The latter can be expected to be explained by an increased amount of water in the mold material mixture (see Examples 3.37 to 3.42 in comparison with Examples 3.04 to 3.06).

Atypical SiO ₂ addition:

The addition of atypical SiO ₂ cures to the same gas treatment parameters, but affects the strength increase for casting cores without amorphous SiO _2, and the initial strength is strongly influenced by the end strength. In the case of high CO ₂ flow and / or long CO ₂ gas treatment times, the end strength is partially reduced by the effect of excess gas treatment (see Examples 3.10 to 3.18 and Examples 3.19 to 3.27 See Examples 3.28 to 3.36).

The addition of atypical SiO ₂ results in a stronger initial strength increase than when the binder content is increased by the same amount. In the case of the end strength, the increased amount of binder is strongly influenced, on the contrary (see Examples 3.13 to 3.15 in comparison with Examples 3.37 to 3.39).

Also, for a uniform solid content, the mixture composed of a water glass binder and atypical SiO ₂ has advantages in terms of initial strength as compared to an increased amount of corresponding binder without amorphous SiO ₂ . In the case of end strength, the increased amount of binder has the strongest adverse effect (see Examples 3.13 to 3.15 in comparison with Examples 3.40 to 3.42).

Increasing the pressure during gas-gas treatment causes another increase in strength (see Examples 3.46 to 3.48 in comparison with Examples 3.13 to 3.15).

6. hardening through the binding of CO _2, air having a CO2, air and gas temperature from 115 to 90 ℃

6.1. A mixture of molding materials consisting of quartz sand H32, 2.0 GT, 2.5 GT or 3.25 GT of water glass with a particle size of about 2.33 and a solids content of about 40% by weight was used for the preparation of the test piece. Also, 0.5 GT amorphous silicon dioxide was mixed into the mold material mixture in powder form before the binder was added. For curing, first CO ₂ and then compressed air passed through the molding material mixture. The temperature of both gases was heated to 120 ° C through a heating tube. The temperature of the two gases was 115 캜 in the early stage when they were introduced into the molding apparatus and decreased to 90 캜 with the gas treatment proceeding for 35 seconds. This temperature reduction may be retrained by the fact that the heating tube can not maintain the gas temperature continuously during the processing of the gas.

Immediately prior to the start of the experiment, the 4.04 test was first repeated approximately 80 times over 50 minutes, so that the molding apparatus reached the required operating temperature of about 60 ° C.

Table 4 shows the gas treatment times of CO ₂ and air, CO ₂ flow, gas pressure (air) and bending strengths found under these conditions (see Examples 4.01 to 3.07).

In Table 4 (see Appendix):

The strength values clearly demonstrate that the combination of CO ₂ gas treatment and air gas treatment is significantly superior to single gas treatment with air or CO ₂ . In particular, Examples 4.01 to 4.03, in which the cure was only carried out with CO ₂ only, had significantly lower initial strengths, except for Example 4.01 - and ending strengths compared to Examples 4.05 to 4.07 of the process according to the invention.

The strength of Example 4.04, which represents only a single gas treated value with air only, is also significantly lower than the strength of CO ₂ - air gas treatment combined according to the present invention. Examples 4.05 to 4.07 The end strengths of 10-60 N / cm ² exceeded those of Example 4.04, while the initial strengths of 50-60 N / cm ² were high. Thus, the significantly higher initial strengths of Examples 4.05 to 4.07 show the effect according to the invention at an increased gas temperature of 115 to 90 캜 for CO ₂ or air. Examples 4.05 to 4.07 are not only insignificant but allow for minor differences.

Not according to the invention Experiment number
Binder mass
[GT]
Amorphous SiO ₂
[GT]
CO ₂ - flow
[L / min.]

Storage time of specimen
Examples / Pressure Strength [N / cm ² ] and thereafter 10s
CO ₂ 15s
CO ₂ 20s
CO ₂ 30s
CO ₂ 45s
CO ₂ 60s
CO ₂ 90s
CO ₂ 3.1 1.01 1.02 1.03 1.04 1.05 1.06 1.07 2
(a) 2 15s
24h 7
76 15
53 19
50 26
31 31
29 38
31 40
25 3.1 1.08 1.09 1.10 1.11 1.12 1.13 1.14 2
(a) 4 15s
24h 12
64 20
57 24
51 35
44 40
46 42
45 43
38 3.1 1.15 1.16 1.17 1.18 1.19 1.20 1.21 2
(a) 6 15s
24h 15
60 24
62 23
49 35
46 40
39 42
35 45
36 3.2 1.22 1.23 1.24 1.25 1.26 1.27 1.28 2
(a) 0.5
(b) 4 15s
24h 31
74 36
71 46
68 49
64 57
60 55
59 52
50 3.1 1.29 1.30 1.31 1.32 1.33 1.34 1.35 2.5
(a), (c) 4 15s
24h 9
153 12
144 19
126 31
98 45
74 52
60 59
57 3.1 1.36 1.37 1.38 1.39 1.40 1.41 1.42 3.25
(a), (d) 4 15s
24h 10
140 17
173 29
165 42
86 59
88 67
67 77
68

(a) sodium water glass, molar ratio of about 2.33 (mol), solid about 40%

(b) Elkem 971 U, additive as dried powder

(c) The additive corresponds to the amount of binder + amorphous SiO ₂ in Experiments 1.22 to 1.28.

(d) Solids (1.3 GT = 2 GT x 40% + 0.5) correspond to Experiments 1.22 to 1.28 estimated from binder amorphous SiO ₂ .

h = time, s = seconds

Not according to the invention Experiment number

Binder mass
[GT]
Amorphous SiO ₂
[GT]
Air pressure
[bar]
Storage time of specimen
Examples / Pressure Strength [N / cm ² ] and thereafter 30s
air 45s
air 60s
air 4.1 2.01 2.02 2.03 2
(a) 2 15s
24h 27
75 71
93 101
104 4.2 2.04 2.05 2.06 2
(a) 0.5
(b) 2 15s
24h 60
175 126
200 161
214 4.1 2.07 2.08 2.09 2.5
(a), (c) 2 15s
24h 16
86 35
102 78
134 4.1 2.10 2.11 2.12 3.25
(a), (d) 2 15s
24h 8
96 31
115 68
126

(a) sodium physic, molar ratio about 2.33 (mol), solid about 40%

(b) Elkem 971 U, additive as dried powder

(c) The additive corresponds to the amount of binder + amorphous SiO ₂ in Experiments 2.04 to 2.06.

(d) Solids (1.3 GT = 2 GT x 40% + 0.5) correspond to the solids of Experiments 2.4 to 2.6, calculated from binder amorphous SiO ₂ .

h = time, s = seconds

Experiment number Binder mass
[GT] Amorphous SiO ₂
[GT] CO ₂ - flow
[L / min] CO ₂ - time
[s] Air pressure [bar] Storage time of specimen Examples / Pressure Strength [N / cm ² ] and thereafter 30s
air 45s
air 60s
air 5.1 3.01 3.02 3.03 2
(a) 2 2 2 15 s
24 h 20
212 52 211 90
230 5.1 3.04 3.05 3.06 2
(a) 2 6 2 15 s
24 h 28
236 67 233 177
238 5.1 3.07 3.08 3.09 2
(a) 2 10 2 15 s
24 h 32
211 70
194 134
183 5.2 3.10 3.11 3.12 2
(a) 0.5
(b) 2 2 2 15 s
24 h 99
296 192
293 233
295 5.2 3.13 3.14 3.15 2
(a) 0.5
(b) 2 6 2 15 s
24 h 92
277 200
238 229
233 5.2 3.16 3.17 3.18 2
(a) 0.5
(b) 2 10 2 15 s
24 h 80
211 154
165 182
139 5.1 3.19 3.20 3.21 2
(a) 6 2 2 15 s
24 h 44
181 95
181 133
205 5.1 3.22 3.23 3.24 2
(a) 6 6 2 15 s
24 h 46
216 117
225 152
220 5.1 3.25 3.26 3.27 2
(a) 6 10 2 15 s
24 h 41
187 114
189 165
182 5.2 3.28 3.29 3.30 2
(a) 0.5
(b) 6 2 2 15 s
24 h 105
311 190
317 234
322 5.2 3.31 3.32 3.33 2
(a) 0.5
(b) 6 6 2 15 s
24 h 91
306 192
270 229
262 5.2 3.34 3.35 3.36 2
(a) 0.5
(b) 6 10 2 15 s
24 h 76
205 145
178 168
160 5.1 3.37 3.38 3.39 2.5
(a), (c) 2 6 2 15 s
24 h 28
364 79
383 140
394 5.1 3.40 3.41 3.42 3.25
(a), (d) 2 6 2 15 s
24 h 9
424 32
414 83
414 5.1 3.43 3.44 3.45 2
(a) 2 6 4 15 s
24 h 101
255 158
280 196
271 5.2 3.46 3.47 3.48 2
(a) 0.5
(b) 2 6 4 15 s
24 h 194
334 245
309 290
304 5.3 3.49 3.50 3.51 2
(a) 2 6 2
(e) 15 s
24 h 18
258 53
289 112
301 5.4 3.52 3.53 3.54 2
(a) 0.5
(b) 2 6 2
(e) 15 s
24 h 31
294 78
276 151
263

(a) sodium water glass, molar ratio of about 2.33 (mol), solid about 40%

(b) Elkem 971 U, additive as dried powder

(c) The additive corresponds to the amount of binder + amorphous SiO ₂ in Experiments 1.22 to 1.28.

(d) Solids (1.3 GT = 2 GT x 40% + 0.5) correspond to the solids of Experiments 1.22 to 1.28 estimated from the binder atypical SiO ₂ .

(e) The air is preheated to 100 ° C (measured at the time of introduction into the molding apparatus) (i) and no complete curing takes place.

h = time, s = seconds

Experiment number Binder content
[GT] Amorphous SiO ₂
[GT] CO ₂ hour
[s] Air pressure
[bar] Air time
[s] Storage time of specimen Example / Bending Strength [N / cm ² ] After 10 L / min 200 L / min 450 L / min 6.1 4.01 4.02 4.03 2
(a) 0.5
(b) 35 4 0 15 s
24 h 10
360 15
44 28
33 6.2 4.04
2
(a) 0.5
(b) 0 4 35 15 s
24 h 83
338 6.3 4.05 4.06 4.07 2
(a) 0.5
(b) One 4 35 15 s
24 h 145
375 138
350 135
400

(a) sodium water glass, molar ratio about 2.33 (mol), solid about 40%

(b) Additive as dried powder, Microsilica POS B-W 90 LD, from Possehl Erzkontor GmbH.

Claims (19)

- preparing a mold material mixture comprising at least one refractory mold material and an inorganic binder;
Inserting said molding material mixture into a casting mold; And
- the mold in the molding material mixture a) or gaseous CO ₂ or the first gas-gas containing CO _2, and b) by flowing the casting mold a second gas containing less CO ₂ than the first gas And curing the material mixture. ≪ Desc / Clms Page number 20 > The method according to claim 1,
Wherein the casting material mixture is introduced into the casting mold using a core shooting apparatus using compressed air, the casting mold is a molding tool, and the first gas and the second gas flow into the molding apparatus . 3. The method according to claim 1 or 2,
Characterized in that the casting mold can not be heated or is heated to a temperature of less than 70 占 폚, preferably less than 60 占 폚, particularly preferably less than 40 占 폚. 4. The method according to any one of claims 1 to 3,
Characterized in that the binder is water glass and in particular the water glass has a molar ratio of SiO ₂ / M ₂ O of 1.6 to 4.0, preferably 2.0 to 3.5, and M represents lithium, sodium and / or potassium Way. 5. The method according to any one of claims 1 to 4,
Characterized in that the mixture of molding materials comprises not more than 1% by weight, preferably not more than 0.5% by weight, particularly preferably not more than 0.2% by weight of organic compounds. 6. The method according to any one of claims 1 to 5,
Wherein the second gas comprises less than 10% by volume, in particular less than 2% by volume of CO ₂ , and is air, nitrogen or a mixture thereof. 7. The method according to any one of claims 1 to 6,
The first gas may comprise at least 25 mol%, in particular at least 50 mol%, preferably at least 80 mol% CO _{2. &} Lt; / _RTI > 8. The method according to any one of claims 1 to 7,
The gas flow rate of the first gas and / or the second gas is 0.5 L / min to 600 L / min, preferably 0.5 L / min to 300 L / min, particularly preferably 0.5 L / min to 100 L / L / min. ≪ / RTI > 9. The method according to any one of claims 1 to 8,
When the first gas and / or the second gas is used at a temperature of from 15 to 40 캜, the gas flow rate of the first gas and / or the second gas is preferably 0.5 L / min to 30 L / min, Is from 0.5 L / min to 25 L / min, and particularly preferably from 0.5 L / min to 20 L / min. 10. The method according to any one of claims 1 to 9,
Characterized in that the filling pressure in relation to the form of the first gas and / or the second gas is from 0.5 to 10 bar, preferably from 0.5 to 8 bar, particularly preferably from 0.5 to 6 bar. 11. The method according to any one of claims 1 to 10,
The ratio of the gas treatment time of the first gas to the gas treatment time of the second gas is 2:98 to 90:10, preferably 2:98 to 20:80, particularly preferably 5:95 to 30:70, Wherein the gas treatment time of the first gas is not more than 60% of the total gas treatment time of the first gas and the second gas. 12. The method according to any one of claims 1 to 11,
The refractory mold material is characterized by having an average particle diameter of 100 to 600 mu m, preferably 150 to 500 mu m, including quartz sand, zircon yarn, chromium light sand, olivine stone, vermiculite, borgite and / . 13. The method according to any one of claims 1 to 12,
The binder, in particular water glass, is present in an amount of from 0.5 to 5% by weight, preferably from 1 to 3.5% by weight, based on the molding material, and the water glass has a solids content of from 25 to 65% by weight, preferably from 30 to 60% . 14. The method according to any one of claims 1 to 13,
Atypical SiO ₂ , in particular synthetic atypical SiO _2, is used, and the amorphous SiO ₂ preferably has an intermediate primary particle size of from 0.05 μm to 10 μm, particularly preferably from 0.1 μm to 5 μm, particularly preferably from 0.1 μm to 2 μm Characterized in that the BET surface area of said intermediate primary particle size is independently from 1 to 200 m ² / g, especially from 1 to 50 m ² / g, particularly preferably from 1 to 30 m ² / g. . 15. The method according to any one of claims 1 to 14,
The amorphous SiO2 is used in an amount of 0.1 to 2% by weight, preferably 0.1 to 1.5% by weight, based on the casting material, independently from 2 to 60% by weight, particularly preferably 4 to 50% %. ≪ / RTI > 16. The method according to any one of claims 1 to 15,
The first gas is introduced into the casting mold at a temperature of from 15 to 120 캜, preferably from 15 to 100 캜, particularly preferably from 25 to 80 캜, and independently of the above, the second gas is the same Temperature or a temperature of 40 to 250 DEG C, and preferably the temperature of the second gas is higher than the temperature of the first gas when entering the casting mold. 17. The method according to any one of claims 1 to 16,
Characterized in that the amorphous SiO ₂ used has a water content of less than 15% by weight, in particular less than 5% by weight, particularly preferably less than 1% by weight, or independently used as a powder. 18. The method according to any one of claims 1 to 17,
The first gas and the second gas are introduced into the casting mold in at least a predetermined time interval and in accordance with any order and the number of inflow processes, and preferably the second gas is finally passed through the casting mold, Characterized in that the first gas first passes only once and then the second gas passes. 18. A casting mold or a casting core which can be produced according to any one of claims 1 to 18.