HU192537B - Additive and method for controlling the emptying strength remaining after casting at water-glass bound mouldings and/or cores - Google Patents

Abstract

Additives to control the post-casting release properties of casting moulds and cores made with water glass binder are prepd. in a closed mixer by introducing 65 wt.% powdered iron-oxide, adding with slow stirring at 30 revolutions per minute 10-20 wt.%, pref. 15 wt.% dry powdered ammonium-ligno-sulphonate and homogenising the mixt. for 5 minutes. To this mixt. is added 20-25 wt.% pref. 20 wt.% powdered boric-acid and the mixt. is homogenised for 20 minutes. The homogenised prod. is packed in evacuated containers for storage or transport.

Description

The present invention relates to an additive and a method for controlling the discharge strength of a mold and / or core material remaining in a cast glass bonded mold and / or core after casting.

By using the additive according to the invention, molds and cores can be manufactured with higher productivity, better surface quality, and the emptying strength generated and retained by casting heat can be reduced in a manner that can be controlled over a wide range of temperatures.

As a result, the time and energy required for sand casting and cleaning of castings can be significantly reduced and sandburns reduced. the occurrence of cold and hot cracks, molds and cores made using the additive are of high quality, non-hygroscopic, and can be stored indefinitely. Another benefit of using the additive is that it does not produce smoke or toxic flue gas during casting that is harmful to the human body and worsens the health and environmental conditions of the foundry.

It is known that there is once again considerable industrial interest in the use of water glass - CO _{2 in} foundries. However, this new boom in interest is not only explained by the economic and technical benefits, but also by the improved hygiene and environmental conditions that the process provides.

It is a fact that, in addition to the above advantages of the water glass - CO ₂ process, there is a specific application technology problem well known to the casting industry. Notably, the water-glass bonded molds and cores of the process develop high residual strengths after casting, which makes it extremely difficult to remove the mold and core parts from the castings. Bounce strength often takes on such dimensions. that the water-glass shape or core, by virtue of its high breaking strength, limits the metal's shrinkage work while the casting cools. If the magnitude of the fracture strength exceeds the yield strength or plastic extensibility of the hardening metal, heat cracking occurs, or stresses are exerted at critical points on the solidified casting, often resulting in cold cracking in external influences such as mechanical discharge of the casting.

In accordance with the technical significance of the known problem, numerous attempts have been made to reduce the residual strength of the molding and core of the water-glass mixture, and to improve the removability of the molding and core parts.

For example, L. Petrzels, for example, found the use of carbon powder, graphite, quartz flour, clay, bentonite, chamotte flour, sodium carbonate as a laxative in water glass mixtures. (Fondrie Beíge 1957, No. 9, pp. 220-222, and Fondrie, 1958, No. 155, pp. 549-553). It only recommends clay as an additive to improve emptying in steel castings. For water-bonded forms of iron castings, it is suggested to use 9 to 7% carbon dust, 1 to 3% refractory clay or kaolinite. It also states that calcium carbonate, magnesite and sugar additives are unsuitable for solving a technical problem. (Slévarenstvi. 1958, Vol. 6, No. 5, pp. 142-149).

It recommends that the emptying additive be coadministered with 1 ° of powdered naphthalene and 2-3% of carbon powder, but this has the disadvantage that the naphthalene component emits very odorous smoke when casting. E. Hlavsa uses a starch solution containing sodium hydroxide to improve the emptying ability of Al castings and copper alloys. (Slévárenstvi. 11, No. 12, 1963, pp. 526-529).

Ή. Gumienny uses 4% carbon powder and 4 * '' coke powder for water glass mixtures and adds 1 ° o asphalt, which he says further improves the emptying capacity of water glass mixtures. (Przeglad Odlewnictva, 1967, Vol. 7, No. 6, pp. 161-165).

According to Z. Wertz, the use of limestone flour and molasses known as loosening agents, especially at temperatures above 800 ° C, does not reduce the residual strength.

No. 162,798. The solution according to the Hungarian patent application uses powdered sugar, iron oxide, magnesium oxide and chalk powder for loosening water glass mixtures.

However, the known additives, although their use in many cases increases the hardness of the molds, cannot satisfactorily reduce the residual strength after casting, since the temperature ranges used are not suitable for the chemical composition, viscosity, eutectic melting temperature and they have a positive influence on the closely related physical and chemical properties. The addition of sugar or molasses also increases the hygroscopicity of the molds, increasing the tendency of water-glass mixtures to stick, thereby reducing productivity, deteriorating the quality of molds, and increasing waste.

For water-glass bonded molds, the residual strength is particularly high for steel, iron and aluminum castings. This phenomenon can be explained that the shapes in the preparation of refractory particles in a heterogeneous distribution of different thickness waterglass trains are formed within the technological blends depending on the shape and particle size and vizüvegoldat viscosity and the mixing conditions of the surface of the particles from which the treatment of CO ₂ result, also the different thicknesses

192,537 silica gels are precipitated, and in the case of larger layers, gel formation is likely to occur only at shallow depths, since the permeability of the gel to CO ₂ gas decreases rapidly with increasing film thickness. In this way, particles of different chemical compositions are formed on the surface of the granules, which melt under the influence of the molding heat and form a high strength Na ₂ O high melting glass melt between the granules, which after curing has a high residual solidity several times higher than the original strength. lends shape and increases the incidence of sandblasting.

It is likely that these adverse szilikátolvadékok casting technologically unfavorable behavior of acidic and basic oxidoik molar ratio in the melt, and the high Na ₂ O content of the glass Ikeda ^v ezőtlen physical and chemical properties of these substances. It is thus obvious that the adverse properties cannot be altered without altering or modifying the chemical composition of the water glass solution used in the technological mixture.

Based on the above, the inventors investigated the metal castings mold forms and to ensure the additive is to eliminate the technical problems related to water glass CO used in preparing the _two process containing a chemically active substance cores which is capable of chemical in the water glass can react with the mold cores in the preparation or during casting and waterglass physical -Chemical properties in a favorable direction. In this way, it is possible to reduce the residual strength after casting, to reduce the incidence of sandblasting and to eliminate hot and cold fractures.

The present invention is based on the discovery that the above objectives can be achieved by providing a chemically active compound or a compound cabinet for water glass solutions and / or water glass foundry molding and / or seed mixtures. is used as a powder additive, which is compatible with the water glass solution, soluble in the water glass, suspended or emulsified and, according to its properties, undergoes appropriate physical and chemical reactions with the water glass solution to select a homogeneous silica gel solution. At the same time, at all points in the mixture system, they provide a homogeneous distribution of beneficial by-products and compounds that reduce or eliminate or reverse or reverse the adverse effects on the original properties of the water glass solution or water glass mixture.

These compounds achieve their objective properties by altering the chemical composition of the water glass solution and the silicate compounds in the process mixtures, and the molds and cores, and modifying the physical properties of the molten silicate molten materials in proportion to the amount used.

FIELD OF THE INVENTION The present invention relates to an additive for controlling the residual strength of water-glass bonded molds and / or cores, which is 60-70% by weight of iron oxide powder in the form of a homogeneous powder mixture and 10-20% by weight, preferably 15% -25 <t ° <>, preferably 20 contains n ^ü bórvegyülebet.

The invention further relates to a process for the preparation of water glass bonded molds and / or cores, wherein 0.01 to 3.0% by weight of an additive according to the invention is mixed with refractory granules, homogenized for 2-3 minutes, preferably 3.5 to 7.0% by weight. 1%, max. 1.6 g'ro ³ density max. 3-module Na water glass solution and homogenize for up to 1.5 minutes, optionally with max. 5% by weight homogenization and bond retardant additive, the resulting mixture is incorporated into the desired form and / or core cabinet immediately, but no more than 70 minutes, and preferably solidified by treatment with CO ₂ .

A preferred endpoint combination of the additive of the present invention consists of ammonium lignosulfonate, boric acid, and iron oxide. When used in a water glass molding or seed mixture, the ammonium lignosulfonate first reacts chemically with the sodium ions of the water glass solution and then, at a slower reaction rate, the boric acid reacts with the sodium ion ion. The quantity of silica gel chemically equivalent to the amount of the chemically active compound combination employed will be precipitated from the water glass solution in the mixture, thereby resulting in a slow, spontaneous solidification of the resulting mold or core, regardless of CO ₂ treatment. Meanwhile, the compounds are homogeneously distributed in the mixtures to form sodium lignosulfonate or sodium tetraborate. The latter binds crystal water, thereby further increasing the rate of solidification. The sodium lignosulfonate formed has a beneficial effect on process mixtures, molds and cores by reducing the sodium concentration and also the surface tension and viscosity of the water glass solution. Thus, during the preparation and processing of the mixtures, the surface of the refractory particles is well wetted, thus contributing to the formation of a homogeneous, uniform film thickness of water glass. It also ensures the homogeneous distribution of the beneficial boron compounds in the blends, molds and cores, reduces the friction of the blends, increases the bulking capacity, the formability, eliminates the adhesion, the adhesion of the blends,

-3192 537 ensures productive machinability of frogs on a firing machine and the production of uniform, high quality molds and cores.

Boron compounds favorably modify the chemical composition of the water glass solution and the silicate molten compounds by improving the proportion of acidic oxides and by increasing the amount of B ₂ O ₃ used. In this way, the physico-chemical properties of the silicate melt formed by the molding heat are favorably influenced. In water-glass bonded molds and cores, boron compounds have a beneficial effect by reducing the viscosity of silicate molten materials, lowering the eutectic melting temperature, favorably decreasing its thermal expansion and elasticity, and enhancing its oxide solubility.

In water glass bonded molds and cores, the formation of high residual discharge strengths due to the elasticity of the Na ₂ O component present in the melt is believed to be controlled by increasing the proportion of acidic oxides in the silica to the proportion of the basic oxides. As a result, the elasticity of the solidified melt and hence its strength are reduced. In addition, the breaking strength is reduced by providing, throughout the homogeneous distribution, fault-prone sites of crystalline systems that are prone to fracture failure in the silicate layers that hold the grain system together.

The chemically modified silicate molten boron compounds thus exhibit much lower fracture resistance to the work of shrinking the die casting and to the homogenization of the casting, thereby eliminating the causes of cold and hot cracks and significantly removing the mold and core parts from the castings. And because of their oxide dissolving effect, they significantly reduce sandblasting, thereby facilitating the cleaning of castings and improving the surface quality of castings.

The chemically active compounds, compound combinations according to the process, furthermore, have a favorable effect on the productivity of water-glass bonded molds and cores by initiating pre-gelation in the water glass solution and in homogeneous distribution of the molds at each point. As a result, molds and cores achieve the technological strength required for deformation-free extraction with less CO ₂ input and shorter gas treatment operations, evenly hardening everywhere in less time. The advantage of this is particularly advantageous in the production of six large-sized molds, cores, for which, for reasons already well-known, CO ₂ treatment is difficult or not feasible at all. Since the water-glass bonded molding and core mixture systems of this process exhibit slow self-solidification depending on temperature and the amount of compound or compound combinations used, they must be processed within 70 minutes. If the spontaneous hardening reaction is too fast, the water glass solution is diluted with 0.5 to 1.5% water, thereby increasing the processing time of the mixtures.

The additive and process of the present invention will now be described by way of example only.

Example 1

The additive of the present invention is prepared in a closed system mixer suitable for mixing, homogenizing fine powder dispersions, and mixing with 65% by weight iron oxide powder, followed by 15% dry ammonium lignosulfonate in powder form at 30 rpm. and the mixture is homogenized for 5 minutes, then 20% porous boric acid is added to the mixture, and the mixture is homogenized for 20 minutes, and the homogenized mixture combination is then added to an aeration unit for storage, transport or further processing in a manner known per se.

The dry powder mixture thus produced was mixed with 1 ° C of refractory granulate, homogenized for 2 minutes, and then blended to a density of 1.58 g'cm ^{1 with a} max. After mixing with a 3.0 Module 5 Na water glass solution, the mixture is homogenized at 30 rpm for no more than 1.5 minutes, then immediately incorporated into molds, core cabinets, and subsequently the molds, cores, are solidified by CO ₂ treatment.

The process of the present invention will now be illustrated by examples of application technology.

Example 2

The composition of the core sand mixtures used to make the inner water-glass cores of 24.8 kg Raba-molded oil sump Al-castings was as follows.

- K4 sand (average particle size 45 »m) 94.4 t = ^U ₀ - additive of Example 1 was 0.6 ° _(t - Na water glass solution M - 2.41 Density = 1.5 g 5 CNA ( 20 ° C) 5.0 t ^{( µ ,} total: 100.0 t ⁿ (l

The above blends were solidified by CO ₂ treatment and the cores were used to produce 110kg Al wafers, 116kg and 200kg Al wound housing castings. Increasing the productivity of seed production 4192,537 allowed a 25% reduction in standard time. The waterglass sand blend composition of the present invention allows for the production of finer surface finishes that are more accurate and easy to clean.

Example 3

Rába trucks have a weight of 72 kg. 22. The composition of the core sand mixture used for water glass cores of iron castings was as follows.

- S 038 sand (average particle size - 40-55 µm) - 93.65% by weight - Additive according to Example 1 = 0.85% by weight - Na glass solution M = 2.45, density = 1.56 g / om ¹ , 20 ° C = 5.5% total: 100.0%

The seeds were solidified with a CO ₂ treatment agent and denatured with a refractory coating of denatured alcohol - graphite. We put it in raw form, cast it. After the castings had cooled, the water-glass cores were easily removed from the castings. The surface of the castings in contact with the water-glass core was, after a single shot of steel and crushed, of good surface quality, metal-free and free of burns.

Example 4 tons weight kóbillamagot was prepared having the following composition maghomokkeverékből water glass, CO ₂ -szilárdítással.

- K4 sand (average particle size - 45 / nm) = 90.1%

- Additive according to Example 1 = 1.2% by weight, 4: 1 solution of soybean lecithin: gas oil 3.5% by weight - Na - water glass solution M = 2.47 density = 1.9 g / cm 2, 20 ° C = 5.2% total: 100.0%

The cores were used to produce 9.75 tons of 200 mm thick die casting castings. After cooling, the castings were 170 atm. pressurized waterbed cleaning to remove the seeds. The core contact surface of the kdkill cast was burn-free.

EXAMPLE 5 For the production of various steel castings weighing from 1 kg to 480 kg, water-glass core sand mixtures and cores of the following composition were used:

- K3 sand (average particle size = 45 / an) -

94.15-93.35% by weight - Additive of Example 1 -

0.85-1.15% by weight - Na glass solution M - 2.43 density: = = 1.52 g cm ', ° C = 5.00-5.50%

Total: 100.0%

The water glass cores prepared according to the above technological composition were hardened by CO ₂ treatment with graphite, alcoholic or zirconium refractory coating and then cast in raw form.

after casting, the water glass cores can be easily removed from the steel castings. The cracks in the gas castings were closed. No burns occurred.

The water-glass cores according to the process are particularly advantageous for the manufacture of valve moldings which are prone to cracking, or for pipe fittings.

Example 6

Water-glass core sand blends of various types of iron and malleable iron compounds were prepared according to the following composition, and the mixture was machine-fired to form different weight cores.

- K4 sand = 92.1% - 65% Fe ₂ O ₃ , 15% ammonium lignosulfonate, 291% B ₂ O ₃ powder combination 0.75 t ° / ₀ - 1: 1 glycerol / water 1.65 t % - Na - water glass solution M = 2.41 Density: = 1.51 g / cm ¹ (20 ° C) 5.5% Total: 100.0%

The seeds were solidified with CO ₂ treatment and coated with a graphite-alcohol refractory coating.

We put it in raw form and then cast it.

The cores were easily removed from the gg-iron and tempervas castings. The surface of the castings was easily sandblasted.

no cast cracks were formed.

Example 7

The following composition of water glass core sand mixture was used to prepare the castings of Example 4.

- sand marked K4 - 93.25% by weight - 65't% Fe ₂ O ₃ + 15% + 101% aminóniumlignoszulfönát B ₂ O ₃ + wt% ammonium chloride 0.75% - Na vízüvegoldait M = 2, 41 fs. 20 ° C

Density: = 1.5 kg'm ¹ 5.5 t% - Water 0.5 t% Total: 100.0 t ^{0 /} u

The water glass sand mixture was processed by a firing machine into various types of fitting cores and solidified with CO ₂ treatment, blackened with graphite alcoholic refractory coating and poured into raw mold with itempervasis. The core castings were easily removable, and the castings were easily sandblasted.

Example 8

For the production of water glass cores of bronze and brass castings, a mixture system of the following composition was used:

- K4 sand 93.65 wt% - Additive of Example 1 0.85 wt% - Na glass solution M = 2.44 ° C, 1.52 g / cm @ ¹ 5.5 wt% total: 100.0 wt% overall, the tests and casting tests already in place have clearly demonstrated that the target has been met. Proven weight of 18-480 kg ac. In the case of castings, when using the additive, the water-glass core sand mixtures did not stick or stick. Seeds production5

They can produce 192 537 more fluidly, using less CO2. During the shaping, the plasticity of the mixture was better, which provided better edge formation and contouring possibilities. During the tests, however, it was found that the cores were more easily removed from the castings.

Claims (5)

An additive for reducing the residual strength of cast glass-bonded molds and / or cores after casting in a controllable manner, characterized in that from 60 to 70% by weight of iron oxide powder in the form of a homogeneous powder mixture and from 10 to 20% by weight as chemically active agent. % ammonium lignosulfonate and 20-25% by weight, preferably It contains 20% by weight of boron compound, preferably boric acid. 2. An additive according to claim 1, wherein the chemically active boron-containing active ingredient is boron trioxide. 25 3. A method of water glass-bonded molds and / or cores thereof, characterized in that the amount of 0.01 to 3 t ₀ °, a first or second additive according to claim refractory granules are mixed, homogenized, and then added 3.5 to 7.0 t%, preferably 5.0 t% max. 1.6 g / cm ^: Density and max. 2.6 Module Na water glass solution and, if appropriate, a total of max. 5% by weight of a known additive to aid homogenisation and / or binder retardation, the resulting mixture is homogenized and then manually or mechanically incorporated into a mold and / or core cabinet and preferably solidified by CO-'treatment;' uk. 4. The process of claim 3, wherein the curing agent is a max. 1.5% water or max. 2% glycerol or a mixture thereof in any ratio. 5. A process according to claim 3, wherein the homogenization additive is a max. 5% by weight vegetable lecithin, petroleum, gas oil or any mixture thereof.