JPS60238058A - Casting method and mold coating material used therein - Google Patents

Abstract

PURPOSE:To suppress effectively carburization and sulfurization by allowing oxides consisting of iron oxide and manganese oxide to exist in a casting mold. CONSTITUTION:The oxides consisting of the iron oxide and manganese oxide are allowed to exist in the casting mold in the stage of using the org. self-curable furan resin mold obtd. by using an org. binder of an acid curing type consisting of a furan resin and a sulfonic acid curing catalyst in executing casting. The carburization and sulfurization occuring in the carburizing material such as carbon and sulfurizing material such as sulfur generated in the stage of pouring a molten metal into the furan resin mold are thus suppressed and prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a casting method and a coating mold used therein, and more particularly, the present invention relates to a casting method and a coating mold used therein. The carburizing and sulfurizing phenomena caused by sulfurizing substances such as sulfur (S) can be suppressed and prevented by the presence of specific oxides in the mold, and the various carburizing and sulfurizing phenomena caused by the carburizing and sulfurizing phenomena can be suppressed and prevented. The present invention relates to a method for preventing carburization and sulfurization that solves the problems, and a coating mold that is advantageously used for this method.

2. Description of the Related Art It is well known that a cast product having a desired shape can be manufactured by pouring various molten metals into a sand mold or a metal mold.

Furthermore, there are various types of sand molds used as the molds, such as green molds, oil sand molds, shell molds, etc., and they are used appropriately depending on the purpose. Recently, special binders and hardeners have been added to sand to facilitate molding operations and sand recycling;
The mold has come into widespread use.

Among organic self-hardening molds, molds made from foundry sand using an acid-curing organic binder and a sulfonic acid-based curing catalyst have rapid hardening and high mold strength. Since the sulfonic acid decomposes and disappears due to the high heat during casting, there are advantages such as the ability to reuse the foundry sand. More specifically, examples of this type of organic self-hardening mold include foundry sand such as silica sand, zircon sand, chromite sand, etc., and furan resin, resol type phenolic resin, urea resin, or furan modified with urea resin or phenol resin. After adding and mixing an acid-curing type organic binder such as a resin and a sulfonic acid curing catalyst (curing agent or curing accelerator) such as para-1 toluenesulfonic acid or xylene sulfonic acid,
A predetermined U-shape is obtained by molding the mixed material and then heating and curing it at room temperature or a relatively low temperature.

By the way, among the various organic self-hardening molds mentioned above, when casting is performed using a furan resin mold molded using an organic binder made of furan resin and a sulfonic acid curing catalyst, carbon ( A phenomenon in which C) and sulfur (S) are concentrated is observed. This enrichment of carbon and sulfur may promote hot cracking in castings,
It is known that various problems occur, such as a decrease in corrosion resistance and further deterioration of its mechanical properties.

Therefore, the inventors of the present application conducted intensive studies to solve this problem, and found that the organic binder of the furan resin contained in the mold was heated due to the high heat when pouring molten metal into the new type of furan resin. It decomposes to produce carbon (C) and its compounds (carburizable substances), which infiltrate into the molten metal and cause a carburizing phenomenon that concentrates carbon (C), especially in the surface layer of the molten metal, causing the above-mentioned disadvantages. I discovered what led to this. In other words, the carburization phenomenon is most noticeable among organic self-hardening molds in hot water molds using furan resin molds.
) The contained components thermally decompose to generate Cα, CIT, etc.
This can be done by decomposing at the high-temperature part of the surface of the casting, producing carburizing substances such as carbon, and causing the carburizing phenomenon described above.

Similarly, when pouring into a new type of furan resin, the high heat applied to the mold causes the sulfonic acid curing catalyst to thermally decompose, producing sulfur (S) and its compounds (sulfurizable substances), which infiltrate into the molten metal. And melt? It has been found that O[O] causes a sulfurization phenomenon that concentrates sulfur (S) in the surface layer, causing the above-mentioned disadvantages. In other words, the sulfurization phenomenon is observed among organic self-hardening molds only when a sulfonic acid-based curing catalyst is used, and since the furan resin th type uses the sulfonic acid-based curing catalyst, this Sulfur (S)-containing components such as sulfonic acid groups contained in sulfonic acid-based curing catalysts are thermally decomposed by injection of high-temperature molten metal and generate SO2, etc., which are further decomposed at the high temperature part of the casting surface. It produces sulfurizable substances such as sulfur and is contaminated with substances that cause the sulfur phenomenon.

-4= The method for preventing carburization and sulfurization of cast products according to the present invention was completed as a result of various studies on countermeasures based on such knowledge, and the gist of the method is as follows. When casting is performed using a mold containing a material that generates carburizing substances and sulfurizing substances when pouring molten metal, iron oxide such as Fe3O4 and M n 20 :l are contained in the mold.
The present invention is characterized in that a specific oxide such as manganese oxide such as MnO2 or MnO2 is present, thereby suppressing the carburizing phenomenon and sulfurizing phenomenon caused by the carburizing substance and sulfurizing substance.

In addition, when carrying out the method for preventing carburization and sulfurization of cast products, oxides consisting of iron oxide and manganese oxide are
A coating mold containing up to 60% can be suitably used.

As described above, the present invention attempts to effectively suppress the carburizing phenomenon and the sulfurizing phenomenon by making each oxide consisting of iron oxide and manganese oxide exist in the mold. The principle of preventing oxidation and sulfurization has not yet been clarified. When estimating this carburization and sulfurization prevention mechanism, two types of methods can be considered: a physical method and a chemical method. In other words, as a physical method, a low melting material or sintered layer is formed between the mold and the molten metal in the presence of oxides to block the decomposition gas generated during casting, thereby preventing carburizing and sulfurizing phenomena. It is presumed that this can be prevented. Furthermore, as a chemical method, it is presumed that the carburizing phenomenon can be alleviated by releasing oxygen (◯) and oxidizing the carburizing gas.

According to the present invention, carburizable substances such as carbon (C) and sulfurizable substances such as sulfur (S) are used to identify iron oxides, manganese oxides, etc. during the process of pouring, solidifying, and mold balun. Due to reasons such as being converted into non-carburizing substances and non-sulfurizing substances by oxides of
It is presumed that carburizing and sulfurizing phenomena on the surface of the casting are effectively suppressed.

In addition, according to the present invention, iron oxide such as Feff04 and M
There are various methods for making a specific oxide such as manganese oxide such as n2O3 or MnO2 exist in the mold. For example, when making a mold, the Fe3O4 is added to the foundry sand.
By mixing and using oxides such as oxides, it is possible to uniformly disperse the oxides inside the main mold, core, etc., or to form a layer inside them (near the surface layer) with a large amount of oxides. This can be done by forming a layer, or by coating the surface of a mold, or by coating the surface of a material such as a film or block that forms the mold. Among these, iron oxides such as Fe-04 and Mn20a and MnO7 are generally used in mold coatings.
It is desirable to make the specific oxide present on the surface of the mold by mixing a specific oxide such as manganese oxide. The amount of the specific oxide present in the mold in this way varies depending on the form in which it exists in the mold, and although it cannot be strictly limited, it is generally about 20% by weight or less. It is preferable that it be present in the mold coating agent in a ratio of 2 to 2, and the upper limit thereof is preferably about 60% by weight when it is present in the mold coating agent.

Preferred embodiments of the method for preventing carburization and sulfurization according to the present invention are shown below, but it goes without saying that the present invention is not limited in any way by the description of these embodiments. In the examples, all percentages and parts are based on weight unless otherwise specified.

Example 1 Foundry sand 98.4 made of silica sand was used to cast a hollow valve casting product having the shape shown in FIGS. 1(a) to (c).
and furan resin as an acid-curable organic binder.
0 parts and 0.0 parts of para-toluenesulfonic acid as a curing catalyst.
A predetermined furan resin mold was made using a mixture of 6 parts and 6 parts, and the following mold coating agent according to the present invention was applied to the inner surface of the mold. This mold coating agent contains an oxide made by blending iron oxide of Fes○4 and manganese oxide of M n 20 s in a blending ratio of 67:33 (approximately 2:1), with an aggregate content of 208- to 60%. Contained. The coating method is two-layered coating, in which the above-mentioned coating agent is applied as the undercoat, and the topcoat is coated with a zircon-based alcohol-based coating agent (for example, Okazaki Mineral Co., Ltd.) to provide resistance to scorching with the molten metal. The product (trade name: Sairiki Super 800) manufactured by Mono Co., Ltd. was used.

Ethanol was used to adjust the density of the undercoat mold, and the paint mold was dried using a burner. In order to improve the casting surface, zircon flour was added. However, if it is only for the purpose of preventing carburization and sulfurization, alumina flour, chamotte flour, mullite flour, chromium 1-flower, silica flour, magnesia flour, etc. are also suitably used.

Next, the molten metal was poured into each of the molds to produce a desired cast product. After removing scale by sand blasting the surface of the test material, that is, the plate-shaped cast product, in each part shown in A to E in FIGS. 1(a) to (c) from the surface layer of the test material, Dried powder was collected in three stages: 0 to 0.5 mm, 0.5-1 mm, Oiwn and ], O-1, and 5 mm, and subjected to carbon (C) and sulfur (S) analysis. The results of this analysis are shown in FIG. 2 as the relationship between the distance from the surface of the cast product and the carbon (C) and sulfur (S) contents of the sample material. However, in Fig. 2, No. 1 indicates a coating mold containing no oxide for comparison, and No. 1 indicates a coating mold containing no oxide.
50. No. 3 is a coating mold containing 20% of an oxide made by blending iron oxide of t and manganese oxide of Mn20+ at a blending ratio of about 2:1, No. 3 is a coating mold containing 30% of the oxide,
No. 4 indicates a coating mold containing 40% oxide, and No. 5 indicates a coating mold containing 50% oxide.

When using a mold coated with a mold coating agent containing an oxide, as shown in Nos. 2 to 5 in Figure 2, 0% and 8% of the surface layer of the cast product related to the sample material, There is almost no difference between 0% and 8% in the deep part of the cast product (center side). On the other hand, in a mold using a coating agent that does not contain oxides, as shown in No. 1 in Figure 2, 0% and 8% of the surface layer of the cast product are 0% and 8% of the deep layer. It showed an extremely high value compared to 8%. From the facts of Kofit et al., conventional iron oxide of Fe3O4 and M n 203
Due to carbon concentration and sulfurization caused by the carburization phenomenon in the surface layer of a cast product obtained using an oxide-free furan resin mold containing manganese oxide in a blending ratio of about 2:1. It is clear that the problem of S enrichment can be effectively solved by the method and mold according to the invention.

In addition, when the above experiment was repeated using other manganese oxides such as M n O2 in place of M n 202 manganese oxide as the specific oxide that has the effect of preventing carburization and sulfurization according to the present invention, it was found that a certain degree of Although there were differences, it was observed that similar results could be obtained.

[Brief explanation of the drawing]

Figures 1 (a) to (c) are cross-sectional views of hollow valve castings related to test materials, and Figure 2 shows carbon (C) and sulfur (S) ) is a graph showing the relationship between contents. Patent applicant: Daido Steel Co., Ltd. FI ((a) (C) (b)

Claims (6)

[Claims] (1) When performing casting using a mold containing a material that generates carburizing substances and sulfurizing substances when pouring molten metal, each oxide of iron oxide and manganese oxide is made to exist in the mold, thereby causing the A Mt manufacturing method characterized by suppressing carburizing and sulfurizing phenomena caused by carburizing substances and sulfurizing substances. (2) The casting according to claim 1, wherein the mold is an organic self-hardening furan resin mold obtained using an acid-curing organic binder made of a furan resin and a sulfonic acid curing catalyst. Correct method. (3) The casting method according to claim 1, wherein the iron oxide is Fe5r4. (4) The manganese oxide is Mn2O3 or MnO2
A casting method according to claim 1. (5) Oxide consisting of iron oxide and manganese oxide
A coating mold containing ~60%. (6) The coating mold according to claim 5, wherein the mixing ratio of iron oxide and manganese oxide in the oxide is about 2:1.