JP4749948B2 - Exothermic molding for casting - Google Patents

Description

The present invention relates to an exothermic shaped article for casting.

  Conventionally, to prevent the hot water temperature from dropping excessively during casting, a heating material is applied in the mold or a shaped product is installed, and this heating material is burned to suppress the lowering of the hot water temperature. Things are done.

Conventionally used casting exothermic shaped articles are mainly made of an easily oxidizable metal powder such as aluminum as a heat source. There are various aluminum raw materials that can be used as described later. Usually , the surface of the metal powder is already more or less thin but already has an oxide film with high heat resistance, that is , an alumina film . As a result, this coating hinders the necessary oxidation reaction (combustion) as a heat generating material. Therefore, the fluorite capable of dissolving the oxide film on the surface of the easily oxidizable metal for the purpose of promoting the oxidation reaction. It is a common technique to mix fluorine compounds such as cryolite and cryolite at the same time.

  For example, Japanese Patent Application Laid-Open No. 2000-17660 (Patent Document 1) states in claim 7 that the “accelerator is any one of cleolite, potassium aluminum tetrafluoride, or potassium aluminum hexafluoride”. It has been shown that the use of fluoride is effective in promoting oxidation, as specified in “The exothermic assembly for casting according to claim 6, which is at least one kind”.

For example , in the exothermic coating agent disclosed in Japanese Patent Application Laid-Open No. 2004-298939 (Patent Document 2), the claim 5 of the claims includes “5 to 15 parts by weight of an oxidation accelerator”. The exothermic coating agent described in any one of 1 to 4 ”is described in the paragraph [0013] of the embodiment of the invention as“ one or more kinds of fluorides such as cryolite and fluorite as the oxidation accelerator ”. Is preferably used. "

  Similarly, the casting heat-generating material disclosed in Japanese Patent Application Laid-Open No. 2003-136201 (Patent Document 3) positively recommends the use of fluoride as an easily oxidizable metal auxiliary agent.

Therefore, considerably so that a large amount of fluorine is detected from the results in forming a exothermic shaped articles cast in this species.
JP 2000-176604 A JP 2004-298939 A Japanese Patent Laid-Open No. 2003-136201

The foundry sand used as a sand mold at the time of casting is usually crushed after the casting is finished, and is screened with a suitable net to remove foreign substances and used repeatedly. Since the exothermic shaped article is used by being embedded in foundry sand, it is inevitable that the remaining material after combustion of the exothermic shaped article using fluoride is mixed into the foundry sand.

  If fluoride is mixed in the foundry sand, it lowers the fire resistance of the foundry sand and leads to worsening of the skin of the foundry. Therefore, it has long been desired to reduce the amount of fluoride used from the viewpoint of recycling the foundry sand. .

Furthermore, since the 2001 environmental notice restricts the soil environmental standards related to fluorine to 0.8 mg or less per liter of test solution, it is necessary to reduce fluoride in industrial waste even in the casting industry. occurs, the development of granulation for exothermic shaped articles castings do not use a fluorine compound is had become desirable even stronger.

However, since the surface of the aluminum particles, which is the main heat source of the heat generating material , is covered with a more or less thin oxide film, that is, an alumina film as described above, it has the property that it is difficult to burn. Therefore, heat generating material is unable to initiate combustion to be raised to a temperature of about 700 to 1000 ° C. which can be alumina the film receives heat from the outside starts burning and disintegration or dissolution As a result, they had to lag slowly. So far, the method of mixing fluoride has been continued as the easiest and effective means for igniting and burning the heat generating material at an early stage.

  In the production of castings, it is required to maintain the heat of the feeder as much as possible without dissipating it. For this reason, it is necessary to control the combustion so that the exothermic shaped article used for the casting hot metal can start combustion as early as possible and maintain a high temperature for a long time.

As a result of various experiments, the inventors of the present invention are able to obtain early combustion and necessary and sufficient heat generation and heat retention without using a fluorine compound, according to a specific exothermic shaped article formed by a wet molding method. I found.

  The present invention was made based on the idea that if the oxide film on the aluminum surface can be disintegrated and dissolved by the combustion heat of magnesium ignited early, the combustion of aluminum, which is the main heat generation source, can continue to be promoted after early ignition. It is a thing.

Therefore, the exothermic molded article for casting according to the present invention comprises 5 to 40% by weight of aluminum heating material, 1 to 30% by weight of magnesium powder having an average particle size of 50 μm to 5 mm , 3 to 30% by weight of oxidizing agent , Containing 0.5 to 20% by weight of fibrous material, 2 to 15% by weight of binder, and 0 to 50% by weight of refractory aggregate as the balance , and formed by a wet molding method (however, each component Is 100% by weight).

Such an exothermic molded article for casting according to the present invention includes, as a preferred embodiment, one that does not substantially contain a fluorine compound.

Examples of those that generate heat early include flammable materials such as organic substances and oils and fats, but even if they burn quickly at low temperatures, they themselves do not reach a high temperature until the refractory film on the surface of aluminum is dissolved. Magnesium that is easy to oxidize and burns instantaneously for a short time and generates heat to a high temperature, so even if it is mixed in a small amount, it becomes locally hot and induces the burning of adjacent aluminum to continuously promote the burning of aluminum. It becomes possible.

In addition, once combustion is started, it is possible to burn early by reducing the particle size of aluminum, which is a heat source, or increasing the amount of iron oxide powder, peroxide, etc. If the refractory coating made of aluminum oxide is present on the surface of aluminum, the particle size of aluminum is reduced or the amount of oxidizing agent such as iron oxide powder or peroxide is increased. I can't even expect.

According to the present invention, while having a conventional wet type same heating performance and shaped pyrogenic shaped articles by molding, the eco-type of the remaining material after use without fluorine is harmful substances press An exothermic shaped product for hot water insulation can be provided.

<Exothermic molding for casting>
The exothermic shaped article for casting according to the present invention is used at the time of casting to suppress and delay the temperature drop of the feeder as much as possible, and its composition is 5 to 40% by weight of the aluminum heating material, and the average particle size is 50 μm to 5 mm. 1 to 30% by weight of magnesium powder, 3 to 30% by weight of oxidizer, 0.5 to 20% by weight of fibrous material, 2 to 15% by weight of binder, and 0% of refractory aggregate It is characterized by containing ˜50% by weight, and it is shaped by a wet molding method, and its product name is called a hot water insulation sleeve, a heat generating core, a heat generating neck down core, a heat generating pad and the like. There are various types of shapes such as a cylindrical shape, a plate shape, and a dome shape depending on the application. There are various types of modeling methods, and they are broadly classified into wet molding that generally models using moisture and dry molding that models without using moisture. The most important difference in the component composition between the two molding methods is that the fibrous material is an essential component in order to obtain a desired exothermic shaped article by drying and solidifying after molding into a predetermined shape in the wet molding method, In the dry molding method, since the fibrous material and other granular materials cannot be blown uniformly, the desired performance cannot be obtained and the fibrous material is usually excluded. The wet molding method implemented in the present application is a molding machine that mixes the above-mentioned various raw materials in water to create a slurry in which the components of the composition are dispersed in water, and permeates water in an appropriate shape according to the shape of the product. The slurry is filled and dehydrated by applying pressure to the slurry, or the molding machine is immersed in the slurry and the molding machine is made negative with a vacuum pump so that the slurry is adsorbed on the molding machine surface and only water is used. It represents a method of obtaining a shaped product of a desired shape by permeating and depositing solid content. The wet molding method can contain a large amount of fiber because the raw material is dispersed in a large amount of water to form a slurry. As a result, the wet shaped product has a small density, is porous, has a high heat retention property, and is a fiber. It is characterized in that high strength can be ensured by the entanglement. Thus, a raw shaped article containing 20 to 40% by weight of moisture and maintaining a predetermined shape by the fiber is dried at 150 to 200 ° C. in a drying furnace to evaporate the moisture and simultaneously solidify the binder. A shaped product having a predetermined strength is obtained. As described above, it is the only modeling method that can use a large amount of fiber, and has been adopted in the hot water insulation industry for more than 30 years. As a result, almost all exothermic shaped products that are currently used by foundry manufacturers in Japan are entirely made of wet-formed products.

<Aluminum heating material>
The content of the aluminum heat generating material, which is the main heat source, is 5 to 40% by weight. Here, aluminum means any of metallic aluminum, aluminum alloys, oxides thereof, and mixtures thereof.

  There are no restrictions on the source, production method, shape, particle size, etc. of the aluminum heating material. For example, slag pulverized powder (aluminum ash) generated during aluminum refining can be used if it does not contain fluorine.

Although this aluminum heat generating material is there is what is oxide film is formed on the surface of the aluminum heat generating material in the present invention has been illustrated as a refractory aggregate in that is capable heat by reaction with oxygen It is distinguished from alumina.

Unlike magnesium, which explosively burns, aluminum can be burned slowly by adjusting the amount of oxidizer such as particle size and iron oxide powder, and it is necessary to maintain as high a temperature as possible. For products, the inclusion of aluminum is an indispensable component. As the content is too small it will not provide sufficient effect as exothermic granulated form products lack the ability to maintain high temperature, whereas the heating power content too many excessively increased to a high temperature in it is difficult to control the heat generation too, so that the further also impair intrinsic thermal effect proceeds sintering exothermic concrete shaped piece too hot. The average particle diameter of the aluminum heating material is 50 μm to 5 mm, preferably 150 μm to 2 mm. Moreover, the shape of the aluminum heating material is arbitrary. For example, a granular shape, a powder shape, a foil shape, or the like can be used. Of these, granular and powder are particularly preferred.

<Magnesium powder>
The content of magnesium powder is 1 to 30% by weight, preferably 3 to 10% by weight. If the content is too small, the effect of promoting oxidation in place of fluoride cannot be exhibited. On the other hand, if the content is too high, the oxidation reaction will be faster. It may be judged dangerous by explosive combustion.

  The source, production method, shape, particle size and the like of the magnesium powder are not restricted, but the average particle diameter of the magnesium powder is 50 μm to 5 mm, preferably 150 μm to 2 mm. Moreover, although the shape of a magnesium granular material is arbitrary, the thing of shapes, such as a granular form, powder form, foil shape, can be used, for example. Of these, granular and powder are particularly preferred.

  Here, magnesium means any of metallic magnesium, magnesium alloys and oxides thereof, and mixtures thereof.

<Oxidizing agent>
The content of the oxidizing agent is 3 to 30% by weight, preferably 5 to 15% by weight. If the content is too low, immediately after the heat of magnesium combustion ignites the aluminum exothermic material, it is insufficient to actively burn the aluminum exothermic material in the thermite reaction. This is not preferable because the fire resistance of the molded article is lowered, and when it is used , thermal cracking and melting of the shaped article are induced.

  As the oxidizing agent of the present invention, for example, iron oxide, bengara, nitrate, manganese dioxide, and potassium permanganate can be used. Among these, iron oxide is particularly preferable from the viewpoints of both effect and cost.

  The oxidizing agent preferably has an average particle size of 50 μm to 2 mm, particularly 15 μm to 0.5 mm. The shape of the oxidizing agent is arbitrary, and for example, a shape such as a granular shape, a powdery shape, or a flat shape can be used. Of these, powder is particularly preferred.

<Fireproof aggregate>
The composition of the refractory aggregate is not essential, but can be mixed as required within a range of up to 50% by weight.

As the refractory aggregate, what has been used when obtaining a conventional exothermic molded article for casting can also be employed in the present invention. Examples of preferable fireproof aggregates in the present invention include alumina, SiO ₂ , ZrO ₂ , MgO, and CaO. Of these, alumina is particularly preferred. Alumina can be produced by the Bayer method, or natural products such as bauxite and band shale can be used. Also, lightweight aggregates such as foamed balloons can be used.

<Fibrous material>
The exothermic shaped article of the present invention uses organic or inorganic materials , or both fibrous materials are used in combination. It is possible to improve the warmth increasingly bulk by mixing the fibrous material. Inorganic fibers are rock wool, alumina silicate fiber, glass fiber, etc., and organic fibers are waste paper, cellulose, cotton, yarn waste, and the like. When mixing, it mixes within the range of 0.5-20 weight%.

<Binder>
In order to impart strength to the exothermic shaped article according to the present invention, a binder is used. An organic or inorganic material is used as the binder, or both binders are used in combination. Examples of the organic binder include dextrin, starch, and phenol resin , and examples of the inorganic binder include clay, bentonite, and sodium silicate . Which binder is used is appropriately determined depending on the performance required of the molded article, but phenolic resins are most commonly used, and the amount added is 2 to 15% by weight.

  In addition, all content of the said component is a thing when the total amount of each component which comprises the exothermic molded article for casting by this invention is set to 100%.

  Hereinafter, the present invention will be described in more detail with reference to examples.

[Examples 1 to 3 and Comparative Examples 1 to 3 ]
In the mixing ratio shown in Table 1 , magnesium cutting powder (magnesium content 95%, particle size 0.5-1.5 mm ), aluminum cutting powder (aluminum content 85%), iron oxide powder (FeO content 90%) ), Alumina (alumina content 98%), fibrous material ( combined use of Al ₂ O ₃ —SiO ₂ fiber and waste paper) and binder (phenol resin) are dispersed in water to form a slurry, which is then formed by wet molding. After shaping into a shape, it was dried at 180 ° C. to obtain an exothermic shaped article for casting of the present invention (Examples 1 to 3 ).

On the other hand, as a comparative example, a shaped article (comparative example 1) using both aluminum cutting powder and cryolite (3 wt%), which has been conventionally used, in the same molding and drying method as in Examples 1 to 3, and the heat generating material are Modeled product that uses only aluminum cutting powder and does not use cryolite or magnesium cutting powder (Comparative Example 2), and Modeled product that uses only magnesium cutting powder and does not use cryolite or aluminum cutting powder (Comparative Example 3) Prepared. The blending ratio of each component is as shown in Table 1.

In general, the longer the burning time, the higher the heat retaining power of the shaped article, which is preferable.
In order to confirm the effect of the exothermic shaped article for casting according to the present invention, a specimen having a thickness of 30 mm × length and width of 45 mm was cut out from the plate-like shaped articles of Examples 1 to 3 and Comparative Examples 1 to 3 in Table 1. Then, it was placed on a heat-resistant refractory brick having a thickness of 15 mm × length 50 mm × width 50 mm and inserted into an elema electric furnace maintained at 1000 ° C. together with the brick, and the ignition time and combustion end time of the specimen were investigated. The ignition time is the time at which some part of the specimen starts to ignite, and the combustion end time is the time at which all surfaces except the surface in contact with the brick of the specimen have been ignited. The combustion time is expressed as a time obtained by subtracting the ignition time from the combustion end time.

Table 2 and FIG. 1 show the relationship between the ignition time and the amount of magnesium added.

As is clear from Table 2 and FIG. 1 , Comparative Example 2 containing neither cryolite nor magnesium takes too much time to ignite aluminum, while Comparative Example 3 using only magnesium without using aluminum. the ignition time, any combustion end time is also completed almost simultaneously explosively burned with the ignition very quickly, once a large amount of gas is generated molten metal boils the shaped article at the time of combustion and is used as a feeder insulation sleeve Ru can be assumed that the scattered become extremely dangerous situation.

Among the products of the present invention, Examples 1 and 2 are equivalent to or superior to Comparative Example 1 in which both the ignition time and the combustion time are conventional products. Further, the combustion time of Example 3 is slightly shorter than that of Comparative Example 1 , but the ignition time is fast, and it is not so fast as to be dangerous for use. Is more preferable than Comparative Example 1 , and the effects of the present invention were confirmed in all cases.

In addition, we fluorine dissolution test for residual material after combustion of the shaped articles of Examples 1-3 and Comparative Examples 1-3. The results are as shown in Table 3 .

Fluorine dissolution test: The method of “Environment Agency Notification No. 13” was followed.

As shown in Table 3, Comparative Example 1, which is a conventional product, had a fluorine elution amount of 30 ppm, but was detected in Examples 1 to 3 and Comparative Examples 2 and 3 that did not use fluoride. Was not.

[Example 4 and Comparative Example 4]
In order to confirm the effect of the present invention, an exothermic shaped article that was actually used at the time of casting, that is, a cylindrical heating sleeve was manufactured and tested in the same manner as in Examples 1 to 3. The raw material composition is as shown in Table 4. Example 4 has the same formulation as Example 1, and Comparative Example 4 is a conventional formulation and the same formulation as Comparative Example 1. The heat generating sleeve has an outer diameter of 240 mm, an inner diameter of 200, a thickness of 20 mm, and a height of 200 mm.

The comparative test was actually used as a feeder sleeve during casting of ductile cast iron, and the appearance and shape of the feeder were investigated by releasing the mold after solidification. As a result, it was confirmed that the shape of the feeder of Example 4 of the present invention and that of Comparative Example 4 which is a conventional product are equivalent, and that the product of the present invention containing no fluorine can be used sufficiently.

From the results of Examples 1 to 4 and Comparative Examples 1 to 4, according to the product of the present invention, while using a specified amount of aluminum and magnesium having a specified particle size without using fluoride, the ignition time is shortened. It was confirmed that the desired combustion time could be ensured and that the hot water was able to close in the same manner as the conventional product using fluoride.

Moreover, as shown in Table 3, fluorine was not detected from the remaining material after combustion of the product of the present invention, and it was confirmed that there was no concern about environmental pollution after use.

<Effect of the invention>
According to the present invention, to provide a eco-type feeder warmth for exothermic shaped articles containing no fluorine is a harmful substance for use surplus material while having a conventional outgoing heat shaped articles and the same heating performance I can do it.

The figure which shows the relationship between the ignition time of an exothermic molded article, and the addition amount of magnesium. The figure which shows the relationship between the ignition time of a heat generating material, and the addition amount of magnesium.

Claims (2)

5-40% by weight of aluminum heating material, 1-30% by weight of magnesium powder with an average particle size of 50 μm-5 mm, 3-30% by weight of oxidizing agent, 0.5-20% by weight of fibrous material , viscosity Exothermic shaped article for casting , containing 2 to 15% by weight of binder and 0 to 50% by weight of refractory aggregate as the balance , and shaped by a wet molding method (however, the total of each component is 100% by weight) To do). The exothermic molded article for casting according to claim 1, which contains substantially no fluorine compound.

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