DE2519309A1 - METHOD FOR MAKING MOLDS - Google Patents

Description

The invention relates to an improved method for producing molds (casting molds), in which a refractory material on a Model is applied in layers.

A known method for producing shell molds (molded masks) with a layered structure consists in applying a slurry of a fine powdery refractory or heat-resistant material and a binding agent (such as sodium silicate, colloidal silicic acid or ethyl silicate) to a model, the coated model after sanding with powdery refractory material
dries and repeats the entire process six to ten times.
However, the complete build-up of the layer and the wax removal require a considerable period of about up to 4 days in this process. According to another mold making method used for

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Reduction of the time required for coating application has been proposed, the slurry is chemically gelled rather than hardened by drying; the However, the shapes obtained do not have satisfactory mechanical strength.

To overcome the aforementioned deficiency, the so-called "Rapid process" proposed in which the model is coated alternately with two different types of slurry, each of which contains a refractory material and a binder and a gelling effect on the other slurry exercises. A variant of this process is e.g. in the Japanese Patent Publication No. 45-1505. At this Method are alternately a slurry of a solution of hydrolyzed ethyl silicate and a refractory on the model Material and a further slurry of an aqueous sodium silicate solution containing ammonium or an amine and applied to a refractory material, sanding being carried out in between. This is how the refractory material becomes Applied to the model in the shape of a shaft. However, the method has the disadvantages that the fire resistance of the generated Shape is small due to the sodium silicate used as a binder and the shape is therefore only suitable for potting relatively low-melting metals and that the water resistance of the shape leaves something to be desired and therefore difficult is to remove wax using the hot water or autoclave method and the like. Another disadvantage of this method is that it is easy to delaminate as well as formation comes from bubbles or cracks or cracks.

Another method is to alternate the model with a positively charged colloidal silica containing one Coated slurry and a negatively charged colloidal silica containing slurry, with therebetween sanding is carried out. This method also has the disadvantages that the fire resistance of the shape obtained is insufficient is and that for wax removal neither the hot water nor

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the autoclave method, only the shock heating method can be applied.

In Japanese Patent Laid-Open No. 49-20025, there is an improved one Variant of the rapid process described in which the Model alternating with a slurry of a finely powdered refractory material and an alkyl silicate hydrolyzate as well as one Slurry of a finely powdered refractory material and a quaternary Ammonium silica with a content of alkali hydroxide or alkali silicate at a molar ratio (expressed as SiOp / MpO, where M represents an alkali metal atom) from 4: 1 to 20: 1. While this method achieves better fire resistance can and, inter alia, the delamination as well as the formation of bubbles and cracks are prevented, affects the defective Stability of the slurry its practical application. on the other hand reached metal oxide sols, such as zirconium oxide, titanium oxide or aluminum oxide sol, regardless of their excellent binder properties not used, as these binders easily dissolve again even after hardening and it is not possible to use a to produce a sufficiently hardened coating on the model.

It is the object of the invention to provide a new, improved method for the production of molds according to the rapid process. In particular, there is the object of the invention is to provide a method of making molds by the rapid process in which the slurries used have excellent stability, the shape obtained has an increased vitrification or sintering temperature, improved strength possesses both that for wax removal at elevated temperatures and better fire resistance and water resistance Hot water process and the autoclave process can be used without cracking, the wall thickness without impairing the high strength of the shell mold can be reduced and the mold is easy to break open after the casting process. In the end is to be created by the invention a new, improved method for the production of molds, which the requirements of the metal casting and the temperatures used

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have grown particularly well.

The inventive method for producing molds is characterized in that a mold model or pattern alternately or simultaneously with a metal oxide sol which is dispersed in water and / or a hydrophilic organic solvent and contains an organic paste resin, or by adding a refractory or heat-resistant material to said sol produced slurry (hereinafter simply referred to as "liquid A") and another liquid, "in which a gelling agent for the colloidal metal oxide and / or organic paste resin contained in the liquid A in water and / or a hydrophilic organic solvent, or a slurry produced by adding a refractory material to said liquid (hereinafter referred to simply as "Liquid B").

A preferred embodiment of the mold making process according to the invention consists in using a liquid B containing a gelling agent exhibiting sine properties and in turn is caused to gel by the liquid A. The liquids A and B used according to the invention are each relatively stable and under no circumstances undergell under any circumstances Formation of a hardened layer coating on the mold model, but rather only when they are brought into contact with one another.

The following detailed description will clarify the present invention Objectives and features as well as the advantages that can be achieved with the aid of the invention.

Due to extensive research in the field of composite Binder has been found that certain such agents, which contain metal oxide sols and organic resin pastes, for the production of hardened, shaft-shaped structures Coatings on the models are well suited.

According to the invention, the main component of the liquid A, i.

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the metal oxide sol, with the aid of a suitable gelling agent for Gelling brought and, in the dried and hardened state, serves as a binding agent for the fine powdery refractory material. That Metal oxide sol can, for example, be zirconium oxide, titanium oxide, iron oxide, magnesium oxide, aluminum oxide, acidic or alkaline Silica, chromium (III) oxide, zirconium oxychloride, basic Aluminum chloride, basic organic aluminate or aluminum hydrogen phosphate sol, a colloidal dispersion of alumina powder or any other suitable colloidal dispersion of a metal oxide powder. The dispersion medium for such oxide sols is usually water, hydrophilic organic solvents or mixtures thereof. Examples of hydrophilic organic solvents are alcohols such as methanol, ethanol and isopropanol or glycerine, amines such as methylamine or ethanolamine, acetone, tetrahydrofuran and dimethylformamide. Examples of preferred Metal oxide sols are aqueous zirconium oxide sol, aqueous-ethanolic zirconium oxide sol, aqueous aluminum oxide sol, aqueous-methanolic Alumina sol, an aqueous colloidal dispersion of alumina powder, aqueous titania sol, aqueous acidic or alkaline silica sol and aqueous-ethanolic silica sol.

Preferred acidic silica sols are those in which the molar ratio SiOg / MgO (where M represents an alkali metal atom) is greater than 50: 1 and the SiO ₂ content is in the range from about 10 to 60% by weight. Snowtex-0 (commercial product of Nissan Chemical Industries, Ltd.) is an example of an acidic aqueous silica sol which has a ρττ value of 2 to 4 and contains 20% by weight of SiOp and 0.03% by weight of Na ₂ O . Further examples of acidic silicon dioxide sols which can be used according to the invention are those which, after adding a small amount of water, have Pjr values of about 3, such as methanolic silicon dioxide sol or aqueous isopropanolic silicon dioxide sol, as well as silicon dioxide sols containing methanol, ethanol, ethylene glycol, an organic acid, such as acetic or formic acid, or an inorganic acid such as hydrochloric, phosphoric or nitric acid.

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Preferred alkaline silica sols which are commercial products include those containing 10 to 60 wt. $ SiOp and whose molar ratio SiOp / MpO (M is an alkali metal atom) is in the range from 5: 1 to about 300 ϊ 1. One can also use other silica sols such as amines, quaternary ammonium hydroxides, guanidine, morpholine, piperidine or barium hydroxide and have p "values greater than 7.

A typical example of alkaline silica sols is Snowtex-30 (commercial product of Nissan Chemical Industries, Ltd.), which has a pjj value of 8.5 to 10.5 and is 30 wt .- $ SiOp and 0.4 wt .- ^ Contains Na _{2 O.} Various hydrophilic organic solvents, such as monohydric or polyhydric alcohols, for example methanol, ethanol, isopropanol, glycerine or glycol, as well as dimethylformamide, are suitable as a dispersion medium for the alkaline silicon dioxide sols.

The preferred metal oxide content of the metal oxide sols is usually 5 wt .- ^ or above. You can of course also mix it of 2 or more metal oxide sols if they are stable.

The organic paste resin used in the present invention usually lies as a dispersion in liquid A. It is generally in the form of a powder or a solution, or emulsion Fine particle dispersion and the like having a concentration of 0.1% by weight or above are used. The organic paste resin serves as an auxiliary binder for the metal oxide sol. It ensures Improved adhesion of the individual layers to one another and prevents the coating from "sagging" when wet or when it is wet. when moistening. The paste resin acts as a binder for the refractory powder material. It must be stable in liquid A. Be dispersible and is expediently caused to gel by the gelling agent contained in the liquid B. if if the organic paste resin is used in the form of a dispersion, the dispersion medium customarily used for metal oxide sols can be used Use the dispersing agent used. Particularly advantageous

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It is liable to the metal oxide sols emulsions of organic polymers to add. Particular suitability "are, for example, aqueous emulsions of homo- or copolymers of vinyl acetate or acrylic esters, such as polyvinyl acetate, ethylene / vinyl acetate copolymers, polymethyl acrylate, Polybutyl acrylate, styrene / butyl acrylate copolymers, aqueous emulsions of epoxy resins and other neutral or alkaline aqueous synthetic resin emulsions and synthetic rubber latices. Further examples of organic paste resin dispersions which can be used according to the invention are aqueous dispersions of alginic acid or its salts, aqueous dispersions of Xanthomonas colloid, aqueous Solutions of urea / formaldehyde resins and aqueous solutions of polyacrylic acid salts with alkali metals, such as sodium, potassium or Lithium. The liquid B is used according to the invention for the gelling of the liquid A and therefore contains a gelling agent for the metal oxide sol and / or the dispersed organic paste resin in the liquid A. If either the metal oxide or the organic paste resin in the liquid A is caused to gel by the gelling agent, the liquid is gelled A in its entirety; it is therefore not necessary for both components to be caused to gel.

However, since an insufficient effect of the gelling agent leads to incomplete gelling of the liquid A and hence none allows rapid formation of a homogeneous, hardened coating layer, it is preferable to use a gelling agent which has a has sufficient gelling effect or is capable of doing so, both the dispersed organic paste resin and the metal oxide sol to gel in the liquid A. The liquid B can contain two or more gelling agents without any adverse effect, provided they are stably dispersible and a sufficient gelling effect can be achieved. The liquid B can thus include a gelling agent for the dispersed organic paste resin and another gelling agent for the metal oxide sol. Water, a hydrophilic organic solvent or a mixture thereof can serve as the dispersion medium for the liquid B.

Table I shows typical gelling agents that, together with the various

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different organic paste resins used in the liquid A. _are applicable.

Table I.

organic paste resin gelling agent in the liquid A liquid B

1 acrylic resin emulsion alcoholic (e.g. methanolic or

ethanolic) melamine / formaldehyde -Harζ solution

2 epoxy resin solution amine, e.g. diethylenetriamine or

ß-phenylenediamine

3 polyvinyl acetate emulsion aqueous alkaline silica sol

4 Xanthomonas colloid aqueous zirconium oxychloride solution Dispersion

5 Aqueous urea / aqueous formic acid, such as hydrochloric acid or aldehyde resin solution, aqueous ammonium chloride solution

6 aqueous sodium polyalcohol, e.g. methanol, ethanol and acrylate solution isopropanol, acetone

Table I shows that the dispersion medium in Liquid B at times serves as a gelling agent; silica sol, alumina sol, zirconia sol and the like can also be used as the gelling agent.

Examples of gelling agents for the colloidal metal oxide in liquid A are amine silicates, alkaline and acidic silicon dioxide sols, Potassium silicate, sodium silicate, lithium silicate, alkali hydroxides, inorganic and organic acids such as phosphorus, Sulfuric, nitric, fluosilicic, acetic and formic acid, inorganic acid salts such as aluminum phosphate and aluminum chloride, acid salts of the aforementioned organic acids, basic inorganic salts and emulsions of immiscible synthetic resins, such as polyacrylate and rubber latex.

In the process according to the invention, the conventional ones can be used to produce the shape refractory materials used are used. They can be in powder, solid or fibrous form. As a rule, those substances are suitable which are the main

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constituent e.g. aluminum oxide, silicon dioxide, magnesium oxide, zirconium oxide, titanium oxide, calcium oxide or graphite. For practical reasons, preference is given to materials with grain sizes corresponding to about 20 to 500 meshes; this grain size range however, this is not a mandatory restriction.

If liquid A does not contain any colloidal metal oxide, i.e. if only the organic paste resin is used as a binder, undergoes the shape during the after the production of the hardened schistiform Wax removal performed on the model and firing process, including deformation, bubble formation and layer splitting (interlaminar separation). Furthermore, it is not only impossible to achieve a shape with sufficient strength, but the shape almost inevitably also loses its original shape. On the other hand, if a liquid A is used which only contains the colloidal metal oxide as a binder without the additive contains an organic paste resin, it often occurs because the gelation does not achieve sufficient binding capacity so-called "running" caused by the softening of the coating layers when the alternate coating process with liquid A and liquid B above that produced by the contact of liquid B with liquid A Layer structure is repeated. As a result, the shape cannot develop properly. If against it the liquid A prepared according to the invention, which contains both the colloidal metal oxide and the organic paste resin contains, is used, the gelled coating produced by the contact of the liquid A with the liquid B has sufficient binding capacity. The coating layers can then dry while maintaining a sufficient coating strength, without "running" in the work process. The finished form is therefore free of any defects, i.e. it comes during the wax removal neither for delamination nor for bubbles or Cracking. Furthermore, the shape produced in this way has satisfactory fire resistance and strength. When the liquid A containing the colloidal metal oxide and the organic paste resin comes into contact with the liquid B

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is brought, there is no exclusive sedimentation of the metal oxide or the organic paste resin after deposition of the relevant component from the dispersion, but the two components gel together and uniformly, and it forms independently of the evaporation or drying of the dispersion medium a gelled coating with sufficient strength. When the dispersion medium subsequently dries away, it arises a cured coating layer with satisfactory green strength. The combined use of colloidal metal oxide and organic Paste resin thus has the advantage that the two components not only ensure mutual binding capacity, but also result in the formation of an excellent gelled layered coating on the model.

The reason for this is probably that the gelling and adhesive properties of the organic paste resin, regardless of whether or not gelation of the colloidal metal oxide takes place, exert a homogeneous gelation effect on the liquid A.

According to the invention, shapes with excellent properties can be produced produce when a liquid B is used, which contains a .Gelling agent, which has binding properties and in turn is caused to gel by the respective liquid A. Namely, if the gelling agent contained in the liquid B. a colloidal metal oxide or organic paste resin other than the colloidal metal oxide contained in the liquid A. and / or represents organic paste resin and is gellable by the liquid A, the liquid B gels similarly to that Liquid A, and a favorable gelled coating layer is formed. Similar results can be obtained then achieve when the colloidal metal oxide and / or the organic paste resin in the liquid B the other colloidal metal oxide and / or organic paste resin does not gel in liquid A, provided that it is colloidal Metal oxide and / or organic paste resin capable of stable coexistence with the other added gelling agent in the liquid B. and through the liquid.A is (are) gellable. Takes place analogously

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in the liquid B an interaction of the colloidal metal oxide and the organic paste resin to form a composite binder by means of which the invention Goal is achieved. If the colloidal metal oxide and organic paste resin contained in liquid B are insufficient To exert gelling effects on the liquid A, an additional gelling agent can be used. However, it is preferred to use an organic paste resin with the necessary gelling effect. Used in the mold making process of the present invention in particular liquids A and B, which on contact gel within 10 minutes to such an extent that the one formed on the model Plating does not flow.

Favorable results can be achieved according to the invention if a liquid A, which is an aqueous emulsion with a ρττ range from 8 to 12, for example an aqueous emulsion as an organic paste resin Emulsion of polyacrylate or an acrylic ester copolymer, synthetic rubber latex or an aqueous emulsion of ethylene-vinyl acetate copolymer, and as the colloidal metal oxide sol, one dispersed in water and / or a hydrophilic organic solvent Contains silica sol having a p ^ value of 7 or above, and a liquid B which, as a gelling agent with binding ability a silica sol dispersed in water and / or a hydrophilic organic solvent with a powert of less than 6 and an aqueous emulsion of polyvinyl acetate or vinyl acetate Copolymer with a p ^ range from 2 to 6 is used.

The refractory or heat-resistant material used according to the invention forms the aggregate in the hardened material produced on the model Layer coating that gives the desired strength and shape Confers fire resistance. The following embodiments are suitable for actually carrying out the coating process according to the invention:

1) First, the liquid containing no refractory material becomes A is applied, followed by sanding with the refractory material and then the application of the no refractory material

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containing liquid B; the whole process is under consideration sufficient standing time between operations;

2) first becomes the refractory-containing liquid A and then the liquid containing no refractory material B applied; the entire process is repeated if there is sufficient standing time between the operations;

3) first becomes the refractory-containing liquid A and then the refractory-containing liquid B applied; the entire process is repeated if there is sufficient standing time between the operations;

4) First, the liquid containing no refractory material becomes A and then the refractory material-containing liquid B applied; the whole process will if sufficient Repeated standing time between operations; and

5) with one of the methods 2) to 4), at appropriate times between sanded with refractory material during the coating process. According to another coating method the liquids A and B and the refractory material are applied to the model at the same time, for example with the help of a Spray gun, and repeat the process at appropriate time intervals. If necessary, liquids A and B can be mixed with the refractory Material to be premixed.

The liquids A and B used according to the invention can contain further additives as required, provided that the liquids according to the invention are Realize goals sufficiently. Examples of these additives are surface-active agents for improving wettability of the model with liquid A, antifoam agent to remove bubbles formed during the coating process, viscosity modifier to adjust the liquids to a viscosity suitable for the application and thixotropy modifier to improve the flow properties of the liquids. The liquid A containing the necessary additives or B can be easily made in a mixer such as that used in the conventional lost wax process.

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Any conventional mold models are suitable as mold models for the method according to the invention, i.e. those made of wax, Synthetic resins and wood. The coating is applied, for example, by placing the model in a liquid immersed and removed again or the liquid spreads or splashes onto the model.

The refractory material is quickly applied to the model according to the method according to the invention, since the gelation of each coating layer takes place fairly quickly and completely without "running" of the coating, regardless of whether sanding is carried out or not. When wax is removed, there is neither crack nor Blistering, so that you get a satisfactory shape with excellent Maintains fire resistance, water resistance and mechanical strength. In addition, those produced according to the invention can be used Shapes break away after the metal casting has been carried out without difficulty. The shapes produced according to the invention are therefore suitable also for the vacuum casting process and especially for the casting of refractory metals. With the help of the various The types of colloidal metal oxide used can ultimately be shaped with different shapes to match those to be cast Manufacture metals with appropriate degrees of fire resistance.

The following examples are intended to illustrate the mold making process of the present invention explain in more detail. However, they are not to be construed in a limiting sense, as there are numerous other modifications and variants are feasible which are within the scope of the invention.

Table II shows the kinds of the metal oxide sol and the used in Examples 1 to 4 and Comparative Examples 1 and 2 organic paste resin dispersion.

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Table II

Kinds of the metal oxide sol and the organic paste resin dispersion

StNr "designation Aluminum oxi d s ο 1 Art Solids content dispersion medium
(Wt .- $) (state of dispersion) , 2 Water (sol) 1 alkaline
Silica sol Al ₂ O ₃ 9 , 0 Water (sol) 2 Zirconia sol SiO ₂ 28 , 0 Water (sol) 3 Zirconia sol ZrO ₂ 23 , 0 Water / ethanol ge
mixed (weight diff
ratio 1: 1) (Sol) 4th Titanium oxide sol ZrO ₂ 23 , 0 Water (sol) 5 TiOo 15th

Aluminum-

bipho sphat solution 'AIpO -,

Amine silicate

Vinyl acetate emulsion

Acrylic ester emulsion

SiO,

25.0 'water (sol solution)

28.0 water / ethylene glycol (Weight ratio 19: 1) (sol solution)

Polyvinyl acetate

Polymethyl acrylate

50.0

50.0

10 urea resin- urea / 20.0 solution formaldehyde

-Condensate resin

Water (emulsion) water (emulsion) water (solution)

-H-

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Tabel

III

Compositions of liquids A and B

CD -v. CD CO

* \ ^ Designation
Components \ v example 1 A. B. 2 A. B. 3 A. B. 4th A. B. Comparative example A. B. 2 A. B. Type of metal oxide sol *)
amount used (kg)
A.rt of organic
Paste resin dispersion *)
amount used (kg)
Type of
Dispersion medium
krt of the gelling agent *)
amount used (kg)
Ethyl siliconate **) (g)
Zircon flour ***) (kg)
fused quartz
powder ****) ■ (kg) (D
3.5
(8th)
0.5
Vasser
20th
13.8 water
(2)
4.0
16.5 (3)
3.7
(9)
0.3
water
20th
9.3 Yasser /
Ethanol
(4)
4.0
9.0 (2)
3.2
(10)
0.2
water
12.5 water
(6)
3.6
15.2 (5)
3.5
(8th)
0.2
Water/
Ethanol
12.6 water
(7)
3.8
20th
15.2 1 (D
4.0
water
20th
13.8 water
(2)
4.0
16.5 (3)
3.7
(9)
0.3
water
20th
9.3 water
(3)
4.0
9.0

*) Liquid numbers in Table II **) Pronon 201 antifoam agent (Nippon Yushi Co., Ltd.) ***) Grain size corresponding to 300 meshes and below ****) Grain size corresponding to 325 meshes and below

(The term "meshes" here and elsewhere means "meshes".)

cn

CD CO CD CO

example 1

A) Preparation of a liquid A (slurry)

According to the recipe given in Table III, a 6 liter stainless beaker equipped with a stirrer is charged Steel while stirring in this order with the metal oxide sol, the organic paste resin dispersion, the methyl siliconate and the refractory powder material and continue stirring for 3 hours at room temperature at 60 rpm. The desired liquid is obtained in this way A (slurry).

B) Preparation of a liquid B (slurry)

Using the recipe given in Table III, one makes analogous to A) produce a liquid B (slurry), i.e. an aqueous silicon dioxide sol is mixed as a gelling agent with stirring with the refractory powder material.

G) Manufacture and testing of the molds

The shapes are as follows using those in the above Liquids A and B and refractory material in a temperature of 20+ 3 ° C and a relative humidity of 60 $ room. The wax models are immersed in the liquid A or B, according to sanded with the refractory material after removal and finally left to stand for a predetermined period of time. This work process is repeated in compliance with the coating sequence shown in Table IV.

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Table IV Coating Sequence

Coating no. Liquid refractory material service life, min

1 A zircon sand No. 80 (mesh) 40

2 B zircon sand No. 80 (") 60

Fireclay sand with a particle diameter of about 3

3 A. 4th B. VJl A. 6th B.

Fireclay sand with a particle diameter of about 0.6 mm 60

Fireclay sand with a particle diameter of about 1 mm

After the sixth coat has been applied, the model is left as is in the room for 24 hours and dried. Repeat the manufacturing process and create a total of six dried molds. Three of these forms are given with directed downward uncoated side in an electric furnace and about 7Minuten to 1000 ⁰ C heated, thereby eliminating the wax model. After the wax has been removed, no layer splitting or the formation of bubbles or cracks can be found anywhere on any of the three shapes. If molten alloy N-155 at 1600 ^° C. is poured into the aforementioned molds, no irregularity occurs; Fire resistance and strength of the three forms are thus satisfactory. The remaining three dried molds are heated to 160 ° C. in an autoclave for 20 minutes to remove wax and then left to stand at room temperature for 24 hours. Even with these forms, no delamination or the formation of bubbles or cracks are observed. If you pour molten alloy N-155 at 1600 ⁰ C into the molds, no irregularity can be found; Fire resistance and strength of the molds are therefore satisfactory.

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Example 2

Liquids A and B are prepared analogously to Example 1 using the recipes listed in Table III, which contain the metal oxide sol, the organic paste resin, the gelling agent and a different refractory material than that of Example 1. A total of six molds freed from wax are produced according to Example 1, ie three molds are freed from wax in an electric oven and the remaining three molds are freed from wax in an autoclave. Subsequently, according to Example 1, alloy SCS 14, melted at 165O ⁰ C, is poured into the respective three molds. None of the shapes show any irregularity.

Comparative example 1

Prepare fluids A and B using the table in the table III, analogous to Example 1, but without the addition of an organic paste resin. The coating application is made according to Example 1. In two of the three forms, the applied layers "run" during the dip method application of the fourth coating. In the third form, a corresponding "running" occurs during the after the application of the fifth coating taking place by the immersion method. It is therefore not possible to have a hardened layered one To produce a coating with satisfactory properties on the models. The desired shapes cannot therefore be produced.

Comparative example 2

In example 2, the liquid B in a water / ethanol mixture contains dispersed zirconia sol, the ethanol serving as a gelling agent. Comparative example 2 uses one Liquid B, which contains an ethanol-free aqueous zirconia sol. Liquids A and B are analogous to Example 1 prepared using the recipes listed in Table III. Using these fluids A and B are total six dried forms according to Example 1 produced. In each case three forms are made according to Example 1 in the electric furnace or in the Wax removed from the autoclave. The molds obtained show cracks of considerable size and are not suitable for casting purposes.

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Example 3

Forms are made analogously to Example 1 using liquids A and B with the compositions shown in Table III. All the shapes obtained have excellent properties. In the casting tests carried out according to Example 1, no irregularity was found established.

Example 4

It is prepared analogously to Example 1 using liquids A and B with the compositions shown in Table III Make molds and subject them to the casting tests described above. The shapes have excellent properties Test results are also satisfactory.

Table V illustrates further examples in which the liquid B contains both a silica sol and an organic paste resin as the required gelling agent.

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IO

Tabel

example

lceit

Silica sol organic
Paste resin

refractory
Powder material

further components

A (pH 9.2)

Snowtex-30 (30 io SiO ₉ ; pH 10.1), 4 ig Mowinyl DM
60 ²⁾ , 0.8 kg

Zircon flour,
16.5 kg

A forget-ex.

Sodium silicate solution (molar ratio SiO ₉ / Na ₉ O 2.7: 1; 22Yo SiO ₂ ), 5 kg zircon flour,
18 kg

B (pH 9.5)

Snowtex-0 (10 ^ SiO ₉ ; pH 3.1), 4 kg Mowinyl DV
kg

Zircon flour,
18.5 kg

Newrex TAB, 4 g; Pronon 2 g

A (pH 11.8)

aqueous silica sol φίοΐ ratio SiO ₉ / Na ₉ O 12: 1; ^ά 5fo SiO ₂ ), 4.5 kg Groslene-1.2 kg

fused quartz,
13.5 kg

Bentonite, 16 g

B (pH 2.1)

methanolic silicon dioxide sol (30 $ SiO ₉ ), 4.3 kg alcoholic phenolic resin dispersion
(30 $ solids content), 0.7 kgj aqueous aluminum nitrate solution (30pro-;
cent), 0.2 kg

melted
zener
Quartz,
12 kg

A pH 0.9)

Aqueous silicon dioxide sol (molar ratio Si0 ₉ / Na ₉ 0 20: 1; 22 # SiO ₂ ), 4.7 kg

Malcabond 0.3 kg chamotte,
12 kg

Newrex TAB, 3.5 g

B pH 1.1)

Aqueous silicon dioxide sol (molar ratio Si0 ₉ / Na ₉ 0

10: 1; ολ30 <fo SiO ₂ ) ^o; , 7.8 kg

50 percent H ₂ SO ₄ , 0.15 kg

A pH 2.1)

Snowtex-30 (30 io SiO ₂ ; molar ratio SiO ₉ / Na ₉ O 110: 1), 3.5 kg Malcabond EZ
402 ⁵⁾ , 1.5 kg

Zircon flour,
16.2 kg

B pH 3.4)

Snowtex-0 (20 io SiO ₉ ; pH 3.2), ^ά 4 kg

Polyvinylacetatτ emulsion (50 $ solids content) 1 kg zircon flour,
17.5 kg

Newrex TAB,

2.8 g; Pronone 201,

1.9 g; Poüyä & ylene oxide powder,

2 g

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1) aqueous polyvinyl acetate emulsion with a pesticide content of

JV TOf

2) aqueous emulsion of a styrene / acrylic ester copolymer with a Solids content of 50 #;

3) synthetic rubber latex with a pesticide content of 30 fi (Takeda Yakuhin Co., Ltd.);

4) Acrylic polymer emulsion having a solid content "· of 50 <fo (Maruban Kagaku Co., Ltd.) J

5) aqueous emulsion of an ethylene / vinyl acetate copolymer with a pesticide content of $ 50 (Maruban Kagaku Co., Ltd.) »

6) surfactant (Nippon Yushi Co., Ltd.);

7) Antifoam Agent (Nissei Sangyo Co., Ltd.);

8) added together with the sulfuric acid to achieve a Pjr value of 1.1.

Example 5

A) Preparation of liquids A and B.

The slurries are prepared using the ingredients shown in Table V in the amounts indicated. A cylindrical 10 liter vessel equipped with a stirrer is first charged with the silicon dioxide sol and then the organic paste resin is added together with the surface-active agent and the antifoam agent (if necessary) with stirring at 60 rpm. Finally, the refractory powder material _/ has an average particle diameter corresponding to 250 mesh, is added. After stirring for 30 minutes, the mixture is left to stand for 24 hours and then stirred again. In this way, the desired slurries are obtained.

B) Making the molds

A 5-liter wide-neck polyethylene jar equipped with a stirrer is used with slow stirring (60 rpm) with the from Table V (Example 5) apparent liquids A and B charged. Then four wax models are immersed in liquid A for impregnation a, sand it with zircon sand No. 80 after removal, leave it to stand for 3 minutes, immerse it in the liquid for impregnation

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ity B, sand it again after removal with zircon sand No. 80, leaves it for 3 minutes, dips it again Applying a third coating to the liquid A, sanding it with sand with aluminum oxide scrapers after removal a particle diameter of about 0.5 mm, leave it to stand for 3 minutes, then immerse it again to apply a fourth coating into the liquid B, sanded it after removal as after the application of the third coating, dips it for application a fifth coating again in the liquid A, sand it again after removal with sand rich in aluminum oxide a particle diameter of about 1 mm, leave it to stand for 3 minutes, then immerse it again to apply a sixth coating into liquid B and after removal, without sanding it, dries it for 24 hours at room temperature. on in this way the desired molded shells are obtained.

On the other hand, shell molds are produced by the same method, but using the liquid shown in Table V (Example 5) A of the comparative example is used.

The two according to the invention as well as both of the comparative example shell molds produced are given with uncoated downwardly directed sides in a heated at 900 ⁰ C electric furnace, and maintained there for about 5 minutes to wax removal in this. Examination of the shells freed from wax shows that the molded shells produced according to the invention show no cracks or bubbles, while the molded shells of the comparative example have bubbles on the surface from which the wax has been removed and layer splits in three places.

The remaining two shell molds each of the two examples are in an autoclave at 15O ⁰ C and 7 kg / cm ² pressure with hot water freed from the wax. The wax removal process does not cause any softening or cracking of the molded shells produced according to the invention. In contrast to this, the molded shells produced according to the comparative example show a considerable degree of softening or slackening and, although no cracking occurs,

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follows, such a strong deformation that it is, not as Casting molds are suitable.

Although the mold shells produced according to the invention have a very high degree of green or Have raw strength, they can easily break apart after the metal casting.

Example 6

The wax models are coated analogously to Example 5 using liquids A and B listed in Table V (Example 6). Each of the coatings formed with one liquid becomes effective and rapid through the coating of the other liquid brought to gel without the coating "running" on the surface of the models when they are immersed in the liquids immersed and sanded after removal. Furthermore, the wax removal results are as satisfactory as achieved in Example 5. The molded shells obtained thus have excellent properties.

Example 7

The wax models are made analogously to Example 5 using the liquids A and B shown in Table V (Example 7) coated. A feature of the shell molds produced according to this example is that the liquid B is not a refractory powder material and also contains 0.15 kg of 50 percent HpSO as a gelling agent instead of the organic paste resin. Each of the coatings will Gelled effectively and quickly without the coating "running" on the model surface. In the case of wax removal, the results are just as satisfactory as in Example 5 scored. Excellent molded shells are thus obtained.

Example 8

Each of the liquids listed in Table V (Example 8) A and B is poured into a separate spray gun. Then you inject liquids A and B at the same time in a strength of each 200 g / m 2 on a previously coated with a release agent Wooden model of the type commonly used in the Shaw method

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on. Then sand the model with zirconium flour No. 80 and let it stand on it for 5 minutes. The entire process is repeated twice. In the second and third operations, however, the thickness of the coating from liquids A and B is increased to 800 g / m, while for the second sanding, alumina-rich sand with a particle diameter of about 0.5 mm and for the third sanding, alumina-rich sand with a Particle diameter of about 1 mm is used. The coated surface obtained is further coated with water glass, silicon dioxide and ferrosilicon powder to a thickness of about 50 mm. This gives an inverted shape. The molds obtained have excellent properties, since they show no cracks even after removal from the models and even after firing at 80O ^{0 C for an hour.}

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Claims (4)

Patent claims marriage 1. A method for producing long forms, characterized that one repeats a porm model with a liquid A and a liquid B alternately or coated at the same time, the liquid A being a solvent in water and / or a hydrophilic organic solvent dispersed and an organic paste resin containing metal oxide sol or one by adding a refractory material slurry produced for said sol and the liquid B is a liquid in which a gelling agent for the in the liquid A contained colloidal metal oxide and / or organic paste resin in water and / or a hydrophilic organic Solvent is dispersed, or one produced by adding a refractory material to said liquid Represents slurry. 2. The method according to claim 1, characterized in that the metal oxide sol of liquid A zirconium oxide sol, titanium oxide sol, iron oxide sol, magnesium oxide sol, aluminum oxide sol, silicon dioxide sol, Chromium (III) oxide sol or a mixture of two or more this brine is. 3. The method according to claim 2, characterized in that the gelling agent in the liquid B a metal oxide sol in the form of zirconium oxide oil, titanium oxide sol, iron oxide sol, magnesium oxide sol, Aluminum oxide sol, silicon dioxide sol, chromium (III) oxide sol or a mixture of two or more of these sols and / or one represents organic paste resin. 4. The method according to claim 3 »characterized in that the liquid A is a silicon dioxide sol dispersed in water and / or a hydrophilic organic solvent, which has a ρ value of more than 7 and contains a stable, miscible organic paste resin, or one by addition of a refractory material to said sol - 25 - 509846/0822 and is capable of gelling liquid B,
and that the liquid B is a silica sol dispersed in water and / or a hydrophilic organic solvent, which has a ρττ value of less than 6 and a stable, miscible organic paste resin, or a
is slurry produced by adding a refractory material to said sol and is capable of gelation of liquid A. - 26 - 509846/0822