JPH03198943A - Method for molding aggregate using yellow iron oxide - Google Patents

Abstract

PURPOSE:To accurately decide hardening finish of a mold with the timing of change from yellow to red with heating by mixing yellow iron oxide with molding material or applying this on surface of the mold at the time of mixing aggregate of sand, etc., with inorganic or organic binder, molding and forcedly drying to harden this. CONSTITUTION:At the time of manufacturing the mold for casting by using the molding sand or the other aggregate for molding, phenol resin as the binder is added to the aggregate and also FeO(OH).nH2O or Fe2O3.H2O, etc., is mixed as the yellow iron oxide to make the mold. As the other way, after applying facing material mixing the yellow iron oxide on the surface of mold made of the mixed raw material of aggregate and binder, this is forcedly dried, and by deciding the timing, when moisture in the above yellow iron oxide is removed and Fe2O3 is changed to red, as the finishing point of drying, the insufficient dry of the mold or lowering of the mold strength caused by the excess drying and disintegration of the mold are prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for shaping aggregate, and is applicable to, for example, furan resin molds using a furan resin binder and various molds using a phenolic resin as a binder. be done.

Here, aggregate is mainly silica-based sand in the flan molding method and shell molding method, and abrasive grains in the whetstone, but is not limited to these, and includes metal powder, wood chips, etc. It also includes.

(Prior art) For example, the furan molding method uses a furan resin binder whose main raw material is furfuryl alcohol and an acidic catalyst, as is well known in the past. This is a method of manufacturing molds by hardening the silica-based sand.

Then, in order to make the surface of the mold manufactured in this way more resistant to heat, a paint is applied to the surface.

Further, for example, the shell molding method using a phenolic resin as a binder is a method in which the surface of silica-based sand is coated with a phenolic resin, and the coated sand is baked and hardened to produce a mold.

For those using phenolic resin as a binder,
There are various other products, such as manufacturing whetstones by mixing abrasive grains with phenolic resin and baking them, and manufacturing indoor soundproofing materials by mixing metal powder or wood chips with phenolic resin and baking them. is also used.

(Problems to be Solved by the Invention) By the way, the paints used in the furan molding method described above include those using alcoholic solvents and those using aqueous solvents. The raw materials for such paints are appropriately selected from among paint materials such as Graphi (C), silica (SiOz), zircon (Zi), alumina (Al□0.), and each of these materials. It is a mixture of fine powder and a binder such as a phenol resin (other binders that can be used include ordinary paint binders).

For example, in the case of a mold coated with a water-based paint, it is necessary to remove the moisture before use, so the mold coated with a paint film needs to be air-dried or forcedly dried in an oxidizing atmosphere.

In this case, natural drying is not often carried out due to efficiency (economical) considerations such as taking too much time, and forced drying is usually carried out. However, if drying is insufficient at this time, it will immediately lead to product defects, and if drying continues even after the moisture has been removed, the mold itself will collapse and its strength will decrease. There was a problem with doing so.

In addition, we can manufacture molds using the shell mold method described above,
In the production of whetstones or soundproofing materials, it is necessary to heat and harden the mold, but if the heating is insufficient, raw phenol remains, resulting in a decrease in the strength of the product, and when molded using the shell mold method. In the case of molds made using molten metal, there was a problem in that gas harmful to the casting was generated when molten metal was poured into the mold. Moreover, if heated too much, since phenol itself is an organic substance, it may decompose or carbonize, resulting in a reduction in the strength of the product itself. In particular, in the case of shell molding, it no longer functions as a binder.

In this way, when shaping aggregates, regardless of the flan molding method or the shell molding method, heating processes such as forced drying and baking are necessary in all cases, and the heating temperature and heating time at this time must be controlled. As mentioned above, this is an extremely important issue because it directly relates to the quality of the product.

The present invention has been made in view of the above circumstances, and its purpose is to provide a method for shaping aggregates that can extremely easily control the temperature during the forced drying process and the baking process when shaping aggregates. It's about doing.

(Means for Solving the Problems) In order to solve the above problems, the method for shaping aggregates according to the present invention includes adding an inorganic or organic binder to aggregates and kneading them to form a mold. By applying a paint mixed with yellow iron oxide and forcing drying the coated mold, the color of the surface of the paint changes to a reddish color, which is used to determine when the forced drying should end. It is something to do.

In addition, by mixing the aggregate, phenolic resin as a binder, and yellow iron oxide, and baking this mixture, it is baked and solidified when the color of the surface of the baked mold changes to a reddish color. This is the end of the process.

(Function) Yellow iron oxide (F
ed(OH) ・nHzo or pe203 ・HzO)
The mold coated with the paint is then force-dried at a temperature of, for example, around 200°C. The water contained in yellow iron oxide decreases through a chemical change, and when the chemical change is complete, it changes to almost red, which is the color of Fe2O itself, so the color of the surface of the paint changes to a reddish color. This phenomenon is used to determine when forced drying should end. For example, forced drying is ended just before the color starts to change to red.

Further, the aggregate, a phenolic resin as a binder, and yellow iron oxide are mixed, and this mixture is baked and hardened.

In this case as well, for the same reason as above, it can be determined that the baking and hardening has ended when the color of the surface of the baked and hardened mold changes to a reddish color.

(Example) The present invention will be explained in detail below.

In this example, as a typical method for shaping aggregate,
(1) A method for manufacturing a mold using the furan molding method, (2) a method for manufacturing a mold using an inorganic binder molding method, and (3) a method for manufacturing a mold using a shell molding method as examples, and (4) As a binder. As other methods for shaping aggregate using phenolic resin, we will explain a method for manufacturing a grindstone and a method for manufacturing indoor soundproofing material using metal powder, wood chips, etc. However, the method for shaping other aggregates using phenolic resin as a binder is not limited to the above method, and it is of course applicable to various other methods.

(1) Method for manufacturing a mold by Fran molding method.

The manufacturing method of the mold itself using the furan molding method is the same as the conventional one, using a furan resin binder whose main raw material is furfuryl alcohol and an acidic catalyst, and with carefully selected grain shapes, particle sizes, etc. A mold is manufactured by solidifying silica-based sand.

Then, a water-based paint or an alcohol paint is applied to the surface of the mold thus manufactured. However, in this example, a case where a water-based paint is applied is shown. In this case, yellow iron oxide is mixed into the water-based paint.

That is, a water-based paint mixed with yellow iron oxide is applied to the surface of the mold, and the mold coated with the water-based paint is forcedly dried. At this time, the water contained in the water-based paint evaporates due to heating, and along with this, the water in the yellow iron oxide also undergoes chemical changes depending on the temperature. When the water has completely evaporated, only ferric oxide remains in the water-based paint, so the surface of the mold turns red, which is the color of the ferric oxide itself. Therefore, by observing the color change of the surface of the mold coated with this water-based paint, the manufacturer should stop forced drying at the point when the color of the surface starts to change to a reddish color, or just before it starts to change. good. In this case, if the color of the mold surface completely changes to red, it is determined that overdrying has occurred. However, depending on the shape, dimensions, etc. of the mold to be manufactured (for example, a mold that is light in weight, small, and thin), drying may be determined to be complete when the color of the mold surface completely changes to red.

In this way, it is possible to obtain an optimal drying state, and therefore it is possible to reliably prevent a decrease in the strength of the mold due to insufficient drying or excessive drying (particularly excessive drying).

By the way, when casting into a flan mold, countless depressions may occur on the surface of the product (casting). This is thought to be due to harmful gases generated within the mold, but it also appears that casting time, casting temperature, product shape, etc. are also secondary causes. However, the inventor
It was confirmed that by applying a water-based paint containing yellow iron oxide to the surface of the mold as described above, the occurrence of depressions on the product surface was significantly reduced or almost eliminated. This also applies to alcohol paints containing yellow iron oxide.

(2) A mold manufacturing method using an inorganic binder modeling method.

The method of manufacturing the mold itself using the inorganic binder modeling method is the same as the conventional method, and the mold is manufactured using an inorganic binder. Then, a water-based paint or an alcohol paint is applied to the surface of the mold thus manufactured. however,
This example shows a case where a water-based paint is applied.

In this case, yellow iron oxide is mixed into the water-based paint.

That is, a water-based paint mixed with yellow iron oxide is applied to the surface of the mold, and the mold coated with the water-based paint is forcedly dried. At this time, the water contained in the water-based paint evaporates due to heating, and along with this, the water in the yellow iron oxide also undergoes chemical changes depending on the temperature. When the water has completely evaporated, only ferric oxide remains in the water-based paint, so the surface of the mold turns red, which is the color of the ferric oxide itself. Therefore, by observing the change in color of the surface of the mold coated with this water-based paint, the manufacturer can stop forced drying when the color of the surface begins to change to red.

(3) A mold manufacturing method using a shell mold method.

In the method of the present invention, silica-based sand, phenolic resin, and yellow iron oxide are mixed, and the mixture is baked and solidified to produce a mold. The shell machine used for manufacturing the mold is the same as a conventional shell machine equipped with a dump box and a mold, so a description thereof will be omitted here.

At this time, the moisture in the yellow iron oxide undergoes a chemical change depending on the temperature, and as this chemical change progresses, the surface of the mold begins to change to a reddish color, which is the color of ferric oxide itself. Therefore, by observing the change in color on the surface of the mold, the manufacturer only has to finish baking and hardening when the color of the mold changes to red. In this way, the mold can be brought into an optimal baked and hardened state, thereby reliably preventing the generation of gases harmful to the casting due to insufficient heating and the reduction in strength of the mold due to overheating.

(4) Other aggregate modeling methods using phenolic resin as a binder.

■How to manufacture whetstones.

The abrasive grains are mixed with a phenolic resin as a binder, and the mixture is baked and hardened. At this time of hardening,
By observing the change in color of the baked and hardened mold, the manufacturer can finish baking and hardening when the color changes to red.

■A method for manufacturing indoor soundproofing materials using metal powder, wood chips, etc.

Metal powder, wood chips, etc. are mixed with phenolic resin as a binder, and this mixture is baked and hardened. At the time of baking and hardening, the manufacturer observes the change in color of the baked and hardened mold, and when the color changes to a reddish color, the manufacturer just has to finish the baking and hardening.

(Effects of the Invention) According to the method for shaping aggregates according to the present invention, when a mixture of aggregates, an organic binder or an inorganic binder, and yellow iron oxide is mixed, when forced drying or baking, the color of yellow iron oxide is By observing the change, it is possible to accurately determine the end point of forced drying or baking based on the state of the color change. Thereby, it is possible to reliably prevent a decrease in the strength of the product itself, which occurs when drying is insufficient or excessive.

Claims (1)

[Claims] 1) A paint mixed with yellow iron oxide is applied to the surface of a mold formed by adding an inorganic or organic binder to aggregate and kneading these, and a mold coated with the paint in this way. A method for shaping aggregate characterized by determining the end time of forced drying by utilizing the fact that the color of the surface of the paint changes to a reddish color by forced drying. 2) By mixing the aggregate, phenolic resin as a binder, and yellow iron oxide, and baking this mixture, the baked and hardened mold is baked and hardened when the color of the surface of the mold changes to reddish color. A method for shaping aggregate, characterized by: