阅读说明：本技术 制备用于制造铸造模具和型芯的粒状耐火组合物的方法、相应的用途以及用于热处理的再生混合物 (Method for producing a granulated refractory composition for producing casting molds and cores, corresponding use and regeneration mixture for heat treatment ) 是由 李鑫 克里斯蒂安·卢斯蒂格 米尔科·赖诺尔德 玛丽亚·施魏因艾福斯 尼古拉斯·埃格勒 于 2019-09-06 设计创作，主要内容包括：描述了从由耐火材料和含有水玻璃的粘结剂形成的废铸造模具或型芯制备用于制造铸造模具和型芯的粒状耐火组合物的方法,所述方法包括以下步骤：由废铸造模具或型芯提供破碎的材料或者从废铸造模具或型芯制备破碎的材料,其中破碎的材料包含在其表面上具有硬化的水玻璃粘结剂的耐火材料的颗粒和/或颗粒的聚集体,将破碎的材料与基于粒状无定形氧化物的总量以85重量％或更多的量包含二氧化硅的粒状无定形氧化物混合以得到混合物,以及使混合物在400℃或更高的温度下经受热处理。还描述了相应的用途、再生混合物、以及制造铸造模具或型芯的方法。(A method is described for preparing a granular refractory composition for the manufacture of casting moulds and cores from spent casting moulds or cores formed from refractory material and a binder comprising water glass, the method comprising the steps of: providing a crushed material from or preparing a crushed material from a waste casting mold or core, wherein the crushed material comprises particles and/or aggregates of particles of a refractory material having a hardened water glass binder on a surface thereof, mixing the crushed material with a particulate amorphous oxide comprising silica in an amount of 85 wt% or more based on the total amount of the particulate amorphous oxide to obtain a mixture, and subjecting the mixture to a heat treatment at a temperature of 400 ℃ or more. Corresponding uses, regenerative mixtures, and methods of manufacturing casting molds or cores are also described.)

1. A process for preparing a granular refractory composition for use in the manufacture of foundry moulds and cores from spent foundry moulds or cores formed from refractory material and a binder comprising water glass,

the method comprises the following steps:

-providing crushed material from or preparing crushed material from waste casting moulds or cores, wherein the crushed material comprises particles and/or aggregates of particles of a refractory material having a hardened water glass binder on its surface,

-mixing the crushed material with a particulate amorphous oxide comprising silica in an amount of 85 wt% or more based on the total amount of particulate amorphous oxide to obtain a mixture,

and

-subjecting the mixture to a heat treatment at a temperature of 400 ℃ or more.

2. The method of claim 1, wherein the heat treatment

Is at a temperature in the range of 400 ℃ to 750 ℃, preferably in the range of 570 ℃ to 730 ℃, more preferably in the range of 630 ℃ to 730 ℃, most preferably in the range of 670 ℃ to 730 ℃

And/or

In a fluidized bed or hot sand reclamation unit, wherein dust and/or fines and/or solid matter containing alkali ions are preferably removed simultaneously with or after the heat treatment in the fluidized bed or the hot sand reclamation unit.

3. The method according to claim 1 or 2, wherein the step of preparing a crushed material from waste casting moulds or cores comprises subjecting material from waste casting moulds or cores comprising refractory material and a binder comprising water glass to a mechanical treatment such that the material is crushed, wherein the crushed material comprises particles and/or aggregates of particles of refractory material having a hardened water glass binder on its surface,

wherein preferably

-the crushed material comprises particles of a refractory material having a hardened water glass binder on its surface

And/or

-said mechanical treatment comprises two or more successive crushing steps to convert said material coming from a waste casting mould or core comprising a refractory material and a binder containing water glass into particles and/or aggregates of particles of refractory material having a hardened water glass binder on its surface.

4. A method according to any preceding claim, wherein the method comprises

-the step of mixing the crushed material with the particulate amorphous oxide is carried out in the presence of a liquid phase,

preferably in the presence of an aqueous liquid phase,

more preferably in the presence of an aqueous liquid phase comprising water in an amount of 80% by weight or more based on the total amount of said liquid phase,

wherein the mixing step is preferably carried out in the presence of one or more organic compounds that are constituents of the aqueous liquid phase,

and/or

-in the step of mixing the crushed material with the particulate amorphous oxide, mixing the crushed material with a suspension of the particulate amorphous oxide in liquid phase,

wherein preferably, the liquid phase is an aqueous liquid phase,

wherein more preferably, the liquid phase is an aqueous liquid phase comprising water in an amount of 80 wt% or more based on the total amount of the liquid phase,

wherein preferably the aqueous liquid phase comprises one or more organic compounds.

5. The method of any preceding claim, wherein the crushed material is further mixed simultaneously or sequentially with one or more materials selected from:

-a phyllosilicate, preferably selected from the group consisting of kaolinite, metakaolin, montmorillonite, halloysite, hectorite, smectite, muscovite, pyrophyllite, synthetic phyllosilicates and mixtures thereof, wherein preferably the phyllosilicate is partially or fully calcined,

preferably as a pre-mix with the particulate amorphous oxide,

more preferably as a premixed suspension in the liquid phase also comprising the particulate amorphous oxide,

wherein preferably, the liquid phase is an aqueous liquid phase,

wherein more preferably, the liquid phase is an aqueous liquid phase comprising water in an amount of 80 wt% or more based on the total amount of the liquid phase,

wherein preferably the aqueous liquid phase comprises one or more organic compounds,

-a suspending agent, preferably illite-containing clay, smectite and/or attapulgite,

-a wetting agent,

-a dispersing agent,

-an anti-settling agent which is,

-a dye,

-a pigment, the pigment being selected from the group consisting of,

an antimicrobial agent, preferably a fungicide,

-a zeolite, and

-aluminium hydroxide.

6. The process of any preceding claim, wherein the particulate amorphous oxide comprising silica in an amount of 85 wt% or more based on the total amount of the particulate amorphous oxide comprises one or more substances selected from the group consisting of:

-a silica fume of the type having a silica fume,

preferably selected from:

silicon dioxide obtained by oxidizing metal silicon with an oxygen-containing gas, and

by mixing ZrSiO₄By thermal decomposition to ZrO₂And SiO₂The silicon dioxide obtained in this way is,

-an amorphous silica, which is,

-precipitating the silicic acid,

-pyrogenic silicic acid, and

-silica obtained by atomizing a silica melt and subsequently solidifying.

7. A method according to any preceding claim, preferably claim 3, having the following steps in the preparation of crushed material from waste casting moulds or cores:

-producing a moulding mixture comprising a refractory material and a binder comprising water glass and particulate amorphous silica,

-shaping the shaping mixture,

-solidifying the moulding mixture to obtain a solidified casting mould or core,

-using the solidified casting mould or core in a metal casting process to produce a waste casting mould or core.

8. The method of claim 7, wherein the binder further comprises one or more compounds selected from the group consisting of:

-a phosphorus-containing compound, preferably selected from sodium metaphosphate, sodium polyphosphate and mixtures thereof,

-a carbohydrate compound, the carbohydrate compound being selected from the group consisting of,

-a surfactant, preferably an anionic surfactant, more preferably with a sulphate, sulphonate, or phosphate group,

-barium sulfate, and

-an oxidized boron compound, preferably selected from the group consisting of borates, borophosphates, borophosphosilicates and mixtures thereof.

9. The process of any preceding claim, wherein the total amount of particulate amorphous oxide comprising silica in an amount of 85 wt% or more, based on the total amount of particulate amorphous oxide, is,

-in the range of 0.01 to 3.0 wt. -%, preferably in the range of 0.03 to 0.9 wt. -%, more preferably in the range of 0.04 to 0.8 wt. -%, most preferably in the range of 0.06 to 0.4 wt. -%, based on the total weight of the crushed material,

and/or

-in the range of 10 to 60 wt. -%, preferably in the range of 13 to 50 wt. -%, more preferably in the range of 20 to 40 wt. -%, most preferably in the range of 25 to 35 wt. -%, based on the total weight of hardened water glass binder on the surface of the particles and/or aggregates of the particles of refractory material in the crushed material.

10. A method according to any preceding claim, wherein the method comprises

D of the particulate amorphous oxide containing silica in an amount of 85 wt% or more based on the total amount of the particulate amorphous oxide₉₀Less than 100 μm, preferably less than 45 μm, more preferably less than 25 μm, most preferably less than 5 μmμm，

And/or

The particle size of the crushed material is in the range of 100 μm to 600 μm, preferably in the range of 120 μm to 550 μm, more preferably in the range of 150 μm to 500 μm,

and/or

Said D of said particulate amorphous oxide comprising silica in an amount of 85 wt% or more based on the total amount of said particulate amorphous oxide₉₀The ratio to the size of the particles and/or aggregates of the particles of refractory material in the crushed material is less than 1:1, preferably less than 1:10, more preferably less than 1:20, most preferably less than 1: 120.

11. A method of preparing a granulated refractory composition for use in the manufacture of casting moulds and cores from spent casting moulds or cores formed from refractory material and a binder comprising water glass, preferably a method according to any preceding claim,

the method comprises the following steps:

-providing crushed material from or preparing crushed material from waste casting moulds or cores, wherein the crushed material comprises particles and/or aggregates of particles of a refractory material having a hardened water glass binder on its surface,

-mixing the crushed material with a particulate amorphous oxide comprising silica in an amount of 85 wt% or more based on the total amount of the particulate amorphous oxide in the presence of an aqueous liquid phase to obtain a mixture

And

-subjecting the mixture to a heat treatment at a temperature in the range of 400 ℃ to 750 ℃, preferably in the range of 570 ℃ to 730 ℃, more preferably in the range of 630 ℃ to 730 ℃, most preferably in the range of 670 ℃ to 730 ℃, wherein the heat treatment is carried out in a fluidized bed.

12. Use of an aqueous suspension comprising:

an aqueous liquid phase comprising water in an amount of 80 wt% or more based on the total amount of the liquid phase,

and

-a particulate amorphous oxide comprising silica in an amount of 85 wt% or more based on the total amount of particulate amorphous oxide,

as a component of a regeneration mixture comprising crushed material from a waste casting mould or core, wherein the crushed material comprises particles and/or aggregates of particles of a refractory material having a hardened water glass binder on a surface thereof.

13. A regeneration mixture for use in thermal processing, the regeneration mixture comprising:

(i) crushed material from a waste casting mould or core, wherein the crushed material comprises particles and/or aggregates of particles of a refractory material having a hardened water glass binder on a surface thereof, and

(ii) an aqueous suspension comprising:

an aqueous liquid phase comprising water in an amount of 80 wt.% or more, based on the total amount of the liquid phase, and

-a particulate amorphous oxide comprising silica in an amount of 85 wt% or more based on the total amount of particulate amorphous oxide.

14. A method of manufacturing a casting mould or core comprising the steps of:

-preparing a granular refractory composition according to the process as defined in any one of claims 1 to 11,

-mixing the granular refractory composition with a binder, preferably a water glass binder,

shaping the resulting mixture, and

-allowing the binder to cure in the shaped mixture.

Example (b):

example 1: preparation and composition of an aqueous suspension for use as a constituent of a regeneration mixture for heat treatment.

An aqueous suspension ("suspension a") was prepared.

Suspension A was 25% by weight silica fume SIF-A-T (Yingkou Imerys Astron Chemicals Co., Ltd; CAS number: 69012-64-2; SiO₂Content 95 wt%) and 25 wt% of the layered silicate(calcined kaolinite from BASF Catalysts LLC 0.02% residue by sieving through 325 mesh; average Stokes equivalent particle size 1.4 μm) in water. The weight% of silica fume and the weight% of the layer silicate are both based on the total amount of the suspension. D of the silica fume used₅₀Is 1 μm to 2 μm. D of the silica fume used₉₀4.485 μm.

Suspension a was prepared using procedures known in the art. This involves mixing the ingredients (water, silica fume, layered silicate). The important properties of suspension a are summarized in table 1.

TABLE 1

Example 2: pilot plant testing.

Pilot plant experiments were conducted in a "Single Axis ignition flash" (chinese yun foundation Material co. ltd) mechanical processing machine and an "energy efficient countercurrent furnace SX2-5-12 (chinese yun foundation Material co. ltd) fluidized bed. Both of these devices were built and placed in its Tianjin plant by CHIN YING FOUNDRY MATERIAL CO. Pilot experiments were performed as follows:

example 2.1: preparation of crushed material from waste foundry cores, preparation of reclaimed mixtures, and preparation of granular refractory A composition is provided.

I) The spent casting cores (previously used for aluminum casting) formed by the following are mechanically treated (i.e. crushed) by performing a single or two successive crushing steps: refractory material (calcined quartz SAND from LIANXIN SAND GROUP; AFS value 50 to 55; clay content less than 0.1%) and a binder system comprising water glass (from Huttenes-Albertus Chemische Werke GmbH Co., Ltd.)8593) And granular amorphous silica (from Huttenes-Albertus Chemische Werke GmbH Co., Ltd.)8610 based on8610, containing particulate amorphous silica in an amount of 65 to 70 wt%). Here, the material from the spent casting core is converted into a crushed material comprising particles and/or aggregates of particles of refractory material having a hardened water glass binder on its surface.

a. In the first crushing step, a total of 1000kg of the waste casting sand from the waste casting cores was crushed by a general casting crusher. The resulting crushed material was then labeled "sample a".

b. In a second successive disruption step, a total of 750kg of "sample A" was further mechanically treated (disrupted) with a "single-axis loss flasher" mechanical device. Single axis loss flashers are discrete devices. The second successive crushing step was carried out in three batches of 250kg each. All three batches were treated by applying a power of 15kW, a rotation speed of 1800 r/min and a treatment duration of 20 minutes. The resulting crushed material was then labeled "sample B".

c. The resulting samples a and B, both comprising particles and/or aggregates of particles of refractory material having a hardened water glass binder on their surface, were collected for further use.

II) according to "example 1: preparation and composition of aqueous suspensions used as constituents of the regeneration mixture for the thermal treatment "preparation of aqueous suspension a.

III) the fragmented material of sample B was treated in two different ways: (a) without suspension a and (b) with suspension a:

a. 300kg of sample B was fed to an "energy saving countercurrent furnace SX 2-5-12" fluidized bed preheated to 730 ℃. There, sample B was subjected to a heat treatment at 730 ℃ for 1 hour, followed by smoldering without heating for 4 hours and then cooling. The resulting granular refractory composition was then labeled "sample C".

b. Another 300kg of sample B was mixed with 3kg of suspension a to obtain a homogeneous mixture of sample B and suspension a, i.e. the regeneration mixture for the heat treatment according to the invention. The resulting regeneration mixture for heat treatment is then subjected to the same (thermal) treatment as described in step III) a. The resulting granular refractory composition prepared by the process according to the invention was then labeled "sample D".

Example 2.2: crushed material from waste casting cores and preparation according to example 2.1Granular refractory composition of Acid consumption, conductivity and optical analysis of the sand surface of the material.

Acid Consumption (COA) and electrical conductivity were measured and determined for sample a, sample B, sample C, sample D, and for the new granular refractory composition (i.e., calcined quartz SAND from LIANXIN SAND GROUP). COA is a value used in inorganic analytical chemistry (involving acid-base titration of a sample) to determine the base content of a sample. The conductivity value was measured to determine the content of the conductive substance in the sample. Both values are directly related to the "cleanliness" of the sample. Low values for both COA and conductivity indicate high sample cleanliness. High cleanliness granular refractory compositions are preferred because cleaning materials generally show better properties when used to make casting molds and cores. The cleanliness of the samples was further evaluated by analyzing the grit surface of each sample by means of an optical microscope.

Determination of acid Consumption (COA):

means for determining the COA:

analytical balance (accuracy:. + -. 0.01 g);

-a 250mL laboratory bottle with a lid;

-a magnetic stirrer;

-a cylindrical magnetic stirring bar of PTFE (about 50mm x 8 mm);

-a burette;

-a 50mL pipette;

300mL Erlenmeyer flask (wide neck);

-a filter funnel;

-filter paper;

-a filter holder.

Reagents for determination of COA:

-hydrochloric acid (0.1 mol/L);

-sodium hydroxide solution (0.1 mol/L);

bromothymol blue (0.1% by weight in ethanol);

-ultrapure water.

To determine acid consumption, 50g ± 0.01 of the samples (sample a, sample B, sample C, sample D and new granular refractory composition) were weighed into a 250mL laboratory bottle comprising a magnetic stir bar. Subsequently, 50mL of ultrapure water and 50mL of 0.1mol/L hydrochloric acid were injected into the laboratory bottle by using a 50mL pipette. After the vial was closed with a cap, the resulting suspension was first stirred with a magnetic stirrer for 5 minutes and then left for 1 hour. Blind suspensions (i.e. samples without 50g ± 0.01) were prepared in the same way.

Next, the suspension obtained was filtered into a erlenmeyer flask by using a filter system. The solid residue (filter cake) was then washed 5 times each with about 10 ml of ultrapure water, whereby washing water was added to the filtrate. After addition of 4 to 5 drops of bromothymol blue indicator, the filtrate (together with the wash water) was titrated from yellow to blue with 0.1mol/L sodium hydroxide solution.

COA was calculated as follows:

wherein the content of the first and second substances,

V_{blind person}Consumption volume (mL) of 0.1mol/L sodium hydroxide solution for blind suspension, and

V_{sample (I)}Is the consumption volume (mL) of 0.1mol/L sodium hydroxide solution for a corresponding suspension of sample A, sample B, sample C, sample D, or a new particulate refractory composition.

Determination of the conductivity:

means for determining conductivity:

-a laboratory balance (accuracy ═ 0.01 g);

-250mL beaker;

-a cylindrical magnetic stirring bar of PTFE (about 50mm x 8 mm);

-a conductivity meter;

-a measuring cylinder;

-a heating plate.

Reagents for determining conductivity:

-ultrapure water.

To determine the conductivity, 50 g. + -. 0.01g of sample (sample A, sample B, sample C, sample D or the new granular refractory composition) and about 100mL of ultrapure water were poured into a beaker. The resulting suspension was placed on a hot plate and allowed to boil. After boiling for 5 minutes, the suspension was cooled to room temperature, followed by measuring the conductivity by using a conductivity meter.

Analysis of the surface of the grit by means of an optical microscope

Analysis of the sand surface of the samples (sample a, sample B, sample C, sample D and the new granular refractory composition) was performed by photographing the sand surface using a light microscope (VHX550/1000D, Keyence). The evaluation of cleanliness by means of optical microscopy analysis is based on a scale from "1" to "5", where 1 stands for "very clean" (no or almost no impurities-such as residual hardened waterglass-are visible on the surface of the inspected particles) and 5 stands for "very dirty" (i.e. a large amount of impurities-such as residual hardened waterglass-are visible on the surface of the inspected particles).

The results regarding the determination of the acid Consumption (COA), the determination of the electrical conductivity, and the analysis of the sand grain surface by means of an optical microscope are summarized in table 2.

[ Table 2]

As can be seen from table 2, the values of acid Consumption (COA), electrical conductivity and cleanliness by means of optical microscopy for "sample D" (i.e. the regenerated granular refractory composition prepared by the process according to the invention) are close to the ideal values represented by the reference sample "new granular refractory composition". When comparing "sample D" with "sample a" and "sample B" (i.e. the crushed material from the used casting cores prepared by mechanical treatment without additional heat treatment in the fluidized bed), it should be noted that the values of COA, electrical conductivity and cleanliness by means of optical microscopy are significantly improved by the method according to the invention (sample D). Furthermore, a direct comparison of "sample D" with "sample C" (i.e. the regenerated particulate refractory composition in which the crushed material used to prepare the particulate refractory composition was not mixed with the particulate amorphous oxide and the layered silicate prior to the heat treatment) shows that "sample D" shows better values in terms of COA, electrical conductivity and cleanliness by means of optical microscopy analysis.

In summary, the results listed in Table 2 above show that the process according to the invention results in the preparation of a granular refractory composition (from spent casting cores) having extraordinary properties, which is not feasible with the processes generally used in the art.

Further investigations have also shown that the use of an aqueous suspension of silica fume SIF-a-T in water at 50 wt. -%, based on the total amount of the suspension (i.e. using a suspension not comprising layered silicate) also leads to a particulate refractory composition having outstanding properties according to the process of the present invention, wherein the measured values with respect to COA, electrical conductivity and cleanliness by means of optical microscopy for the (regenerated) particulate refractory composition prepared from said suspension are almost as good as those of "sample D" and better than those of "sample a", "sample B" or "sample C".

Example 3: casting cores for casting tests were manufactured.

Example 3.1: by using the compositions prepared according to example 2.1 in combination with "sample A", "sample B", "sample C" (not according to Inventive) and "sample D" (according to the invention) were used to make casting cores.

Samples representing casting cores (bent bars, dimensions: 22.4 mm. times.22.4 mm. times.178.0 mm) were made using "sample A", "sample B", "sample C", "sample D" and the new granular refractory composition (i.e., calcined quartz SAND from LIANXIN SAND GROUP).

Before the casting core was manufactured, the AFS values of the materials corresponding to "sample a", "sample B", "sample C" and "sample D" and the "AFS value" of the new granular refractory composition were determined based on the determination method described in "VDG Merkblatt P27". According to "VDG Merblatt R202", the AFS value is a parameter characterizing the grain size as defined by the American Foundry Society (AFS). In this regard, the AFS value represents the number of meshes per inch of a screen through which the inspected material will pass if the inspected material has a uniform particle size. To determine the AFS value, 100 g. + -. 0.01g of the respective sample are weighed on a sieve column (sieve group comprising sieves with mesh openings: 1.000mm, 0.710mm, 0.500mm, 0.355mm, 0.250mm, 0.180mm, 0.125mm, 0.090mm, 0.063 mm). The sieve tower was operated at an amplitude of 1.0mm for 5 minutes while setting the interval to 0 second, and after the sieving was completed, the contents of each sieve were weighed and an AFS value was calculated by using the following equation:

wherein g is the total mass, g_iMass of single grain species (i.e., 1000mm to 0.710mm), and M3_iMultiplication factor for a single grain species (as listed in "VDG Merkblatt P27").

For the production of casting cores (bending bars), 2.2 parts by weight of a binder containing water glass (from Huttenes-Albertus Chemische Werke GmbH)8593, i.e. water glass binder) and 1.3 parts by weight of additives (based on8610 Total amount of particulate amorphous silica from Huttenes-Albertus Chemische Werke GmbH in an amount of 65 to 70 wt%8610) Homogenized (mixed) with 100 parts by weight (3500g) "sample a", "sample B", "sample C", "sample D" or a new granulated refractory composition. Then, shooting (shooting) is performed by using "Universal Core Shooter (LUT)" from Morek multiserv corporationCasting cores are produced from the resulting mixture. Firing of the casting cores involves shaping the respective mixtures and curing the binder in the shaped mixtures. The parameters for the shooting of the casting cores are listed in table 3.

TABLE 3

Pressure of shooting	4.5 bar
		Duration of the shot	3 seconds
Curing time	30 seconds
		Core box temperature	180℃
Gas (es)	Air (a)
		Time of air blowing	30 seconds
Temperature of gas	180℃

Ten casting cores (bent rods) for each sample ("sample a", "sample B", "sample C", "sample D" and new granular refractory composition) were manufactured by the method described above. The resulting casting cores (bent rods) were used for core strength testing as well as for casting tests.

The core strength of the casting core (bent rod) was tested in the warm state (i.e., 15 seconds after shot) and in the cold state (i.e., 1 hour after shot). Each test for core strength was repeated three times for each casting core composition. An average is then calculated from each of the three measurements. The laboratory, in which the core strength test was carried out, was air conditioned at a temperature of 21 ℃ to 22 ℃ and a relative humidity of 44% to 45%. A sufficiently high core strength is a prerequisite for the use of casting moulds or cores for casting purposes.

In addition, seven bent rods of each casting core composition were weighed in a cold state to obtain an average weight of the casting cores. The average weight of the casting cores represents the ease with which each core is compacted. The lower the average weight of the casting core, the easier it is to compact the casting core. A high average weight of the casting cores corresponds to a high degree of compaction and generally means that the individual casting cores also show improved values with regard to strength and moisture resistance.

The results regarding the core strength and core weight of the casting cores and the AFS values of the materials used to make the casting cores are summarized in table 4. The core strength values listed in table 4 represent the average of three measurements taken.

TABLE 4

As can be seen from table 4, the core strength of the casting cores made by using "sample a", "sample B", "sample C" or "sample D" was close to (or even higher than) the core strength of the casting cores made by using the new granular refractory composition. Further, in addition to "sample a", the samples had an average core weight that was higher than the average core weight of foundry cores made by using the new granular refractory composition. The broken materials from "sample a", "sample B", "sample C" and "sample D" typically have an AFS value that is less than (but in the same area as) the AFS value of the new granular refractory composition.

Example 3.2: casting tests by using casting cores made according to example 3.1

Three casting cores (bent bars) of each casting core composition (A, B, C, D, new) were cast with aluminum alloy. Details on the casting conditions are listed in table 5.

TABLE 5

Casting temperature	710℃
		Pouring time	13 seconds to 15 seconds
Name of casting	Daihatsu Tianjin Plant

Details on the composition of the aluminium alloy used are listed in table 6.

TABLE 6

After casting, the obtained casting was evaluated for the grade of casting surface quality. The evaluation of the grade of the surface quality of the casting was made based on the grades "1" to "4" (where "1" represents that the surface quality of the obtained casting is very good and "4" represents that the surface quality of the obtained casting is very poor).

The results regarding the grade of the casting surface quality of the obtained castings are summarized in table 7. The resulting grades of the surface quality of the castings represent an overall evaluation of all casting cores of the same composition in each case.

TABLE 7

Sample (I)	Grade of surface quality of casting＊
		A	4
B	4
		C	2
D	1
		Novel granular refractory composition	3

With respect to the grade of the surface quality of the castings, the best results were shown for the castings produced by using the casting cores made from "sample D" (i.e. made from the granular refractory composition prepared by the method according to the present invention). The casting surface quality of such castings is significantly better than the grades of casting surface quality of castings produced by using casting cores made from "sample a" and "sample B" (i.e., made from crushed material), and also better than the grades of casting surface quality of castings made from "sample C" (i.e., made from reclaimed granular refractory composition in which the crushed material used to prepare the granular refractory composition is not mixed with the granular amorphous oxide and layered silicate prior to heat treatment) or made from new granular refractory compositions.

Castings with excellent casting surface quality grades can also be obtained by casting cores made from the reclaimed mixture prepared by the method according to the invention, wherein the crushed material used is mixed with an aqueous suspension of silica fume SIF-a-T in water in an amount of 50 wt.%, based on the total amount of the suspension, prior to heat treatment.

Example 4: example 2.1 through implementation was repeated by using different waste foundry core compositions as starting materials Example 3.2.

The above examples 2.1 to 3.2 are generally repeated. However, the spent foundry cores (which are used to prepare crushed material comprising granules and/or aggregates of granules of refractory material having a hardened water glass binder on their surface) are made of refractory material different from the refractory material used in example 2.1 (in particular, in example 4 Mongolia quartz Sand from Ma' an Shenzhou Sand Corporation), a binder containing water glass (from Huttenes-Albertus Chemische Werke GmbH company)8593) And additives (from Huttenes-Albertus Chemische Werke GmbH)8610) And (4) forming.

The determination of COA, electrical conductivity, core strength, average core weight and AFS value, as well as the evaluation of cleanliness by means of optical microscope analysis and the evaluation of the casting surface quality grade were carried out in the same manner as described above. The corresponding results are summarized in table 8. Similar to "sample a", "sample B", "sample C", and "sample D", respectively, "sample a.2", "sample b.2", "sample c.2", and "sample d.2" were obtained. The reference sample "new granular refractory composition" of table 8 corresponds to a sample made by using a new refractory material (i.e., Mongolia quartz Sand from Ma' anshan Shenzhou Sand Corporation).

TABLE 8

As can be seen from table 8, the refractory composition prepared by the method according to the invention ("sample d.2") also shows, in comparison with the corresponding reference samples ("sample a.2", "sample b.2" and "sample c.2"): in this case, values regarding COA, conductivity, evaluation of cleanliness by optical microscope analysis, and grade of the casting are optimum. The method according to the invention thus provides particularly advantageous properties (irrespective of the composition of the used waste casting mould or core) compared to the methods known from the prior art.