JP2007083281A - Anti-sulfur coating agent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sulfur-preventing coating agent for forming a coating layer that reliably prevents a sulfurizing phenomenon in a casting by an acidic gas containing sulfur generated from a mold when cast iron is cast with an organic self-hardening mold. To do.
SOLUTION: The anti-sulfur coating agent of the present invention is composed of an aggregate compound composed of calcium oxide, iron oxide and silica, and has an effect of blocking acidic gas containing sulfur and contains sulfur. It was decided to contain a neutralizing agent that neutralizes the acid gas. By these, the coating layer 12 is formed and the sulfurization from the casting mold 14 is prevented.
[Selection] Figure 1

Description

  In the present invention, when casting with an organic self-hardening mold, a coating that reliably prevents the sulfurization phenomenon of the casting by acid gas containing sulfur generated from sulfuric acid or xylene sulfonic acid added as a curing agent to the foundry sand. The present invention relates to an anti-sulfur coating agent for forming a mold layer.

  In an organic self-hardening mold, furan resin or phenol resin is added as an adhesive, and sulfuric acid or xylene sulfonic acid containing sulfur is added as a curing agent. Organic self-hardening molds are widely used because they are easy to mold and mold after casting, and have a high sand recycling rate.

However, with organic self-hardening molds, sulfuric acid and xylene sulfonic acid added as a hardener to the foundry sand when it is cast thermally decomposes, generating acidic gases containing sulfur such as SOx and H ₂ S that are acidic. The generated acid gas enters the casting and causes a metal structure abnormality. In the cast product, the acid gas containing the generated sulfur and the molten metal come into contact with each other, and in spheroidal graphite cast iron, the spheroidization of the graphite is inhibited and the spheroidization may be poor. As a result, the spheroidal graphite cast iron has a problem that strength and toughness are lowered.

Therefore, as a method for preventing the sulfurization phenomenon occurring in the organic self-hardening mold, there is a method of forming a coating mold with a coating agent containing a combination of a carbonate compound, a metal oxide, a mineral powder, and the like (for example, Patent Document 1), particularly thick casts, has a problem that the effect of preventing the sulfuration phenomenon is insufficient.
JP-A-61-293625

  The present invention has been made in view of the above, and when casting with an organic self-hardening mold, a coating layer that reliably prevents the phenomenon of sulfur sulfidation into the casting caused by acidic gas containing sulfur generated from the mold. It is an object of the present invention to provide an anti-sulfurization coating agent to be formed.

  The anti-sulfur coating agent of the present invention comprises an aggregate composition formed of calcium oxide, iron oxide, and silica, and has an effect of blocking acidic gas containing sulfur, and the acidic gas containing sulfur The neutralizing agent to be neutralized was contained.

The calcium oxide is 10% to 45% by weight of the coating agent aggregate, and the iron oxide is 5% to 85% by weight of the coating agent aggregate, and The silica content was 5% to 60% by weight of the coating agent aggregate. Further, the melting point of the aggregate contained in the anti-sulfur coating agent was set to 1,300 ° C. to 1,400 ° C. Moreover, the said neutralizing agent decided to contain 0.1 to 30 weight% with respect to the said aggregate. The neutralizing agent is sodium silicate. Moreover, the following formula was shown as an example of the chemical reaction.
Na ₂ O.SiO ₂ .H ₂ O + SO ₃ → Na ₂ SO ₄ + H ₂ SiO ₃

  The anti-sulfur coating agent of the present invention is formed of calcium oxide, iron oxide, and silica in which the aggregate composition has an effect of blocking acidic gas containing sulfur, and neutralizes acidic gas containing sulfur. Since the neutralizing agent is contained, when performing casting with an organic self-hardening mold, it is possible to prevent a sulfurization phenomenon caused by an acidic gas containing sulfur generated from the mold.

  In order to enhance the blocking effect, the calcium oxide is 10% to 45% by weight of the coating agent aggregate, and the iron oxide is 5% to 85% of the coating agent aggregate. The silica should be 5% to 60% by weight of the coating material aggregate. By doing so, the melting point of the aggregate becomes 1,400 ° C. or less. When casting is performed and the molten metal is filled in the mold, the aggregated particles are sintered by the heat, so that the acid gas blocking effect is enhanced. On the other hand, if the temperature is lower than 1,300 ° C., a casting surface defect occurs in the casting, which is not preferable. Therefore, by setting the melting point from 1,300 ° C. to 1,400 ° C., it is possible to produce a sound casting that does not cause a sulfurization phenomenon and that does not cause a defective casting surface.

  Hereinafter, embodiments of the anti-sulfur coating agent of the present invention will be described with reference to the drawings.

  FIG. 1 shows a sectional view of an organic self-hardening mold for producing a sample. As shown in FIG. 1, the organic self-hardening mold 10 is formed by molding a casting sand mold 14 inside the casting frame 13 so that a space 11 of 200 mm long × 300 mm wide × 200 mm high is formed. A cast iron melt 17 is poured through the runner 16. At this time, the coating layer 12 is provided between the mold 14 and the space 11. When the casting is cooled and unframed, the center part on the bottom side is cut, and the structure of the casting-coating layer interface is observed to observe the presence or absence of the sulfurization phenomenon. The mold is made by adding 1.5% by weight of furan resin, 1.3% by weight of xylene sulfonic acid and 0.5% of sulfur to the foundry sand. Also, the pouring material is spheroidal graphite cast iron. Table 1 shows data of sample samples of Examples 1 to 4 manufactured by forming a coating layer with the anti-sulfur coating agent of the present invention, and Comparative Examples 1 to 8 manufactured using other coating agents. The data of free samples are shown.

本発明の浸硫防止塗型剤は、有機自硬性鋳型の鋳型より発生する硫黄を含む酸性ガスを遮断する目的として、酸化カルシウムＣａＯと酸化鉄Ｆｅ_２Ｏ_３とシリカＳｉＯ_２との骨材１２ａを含み、硫黄を含む酸性ガスを中和する中和剤として珪酸ソーダＮａ_２Ｏ・ｎＳｉＯ_２・ｍＨ_２Ｏ１２ｂを含有し、水を溶媒とする。表１の実施例１〜４は、それぞれ組成が異なる本発明の浸硫防止塗型剤を使用し、比較例１〜８は、実施例１〜４とそれぞれ組成が異なる塗型剤を使用する。

The anti-sulfur coating agent of the present invention is an aggregate 12a of calcium oxide CaO, iron oxide Fe ₂ O ₃ and silica SiO ₂ for the purpose of blocking acidic gas containing sulfur generated from the mold of the organic self-hardening mold. hints, contain sodium silicate _{Na 2 O · nSiO 2 · mH} 2 O12b as a neutralizing agent to neutralize the acid gases containing sulfur, water as a solvent. Examples 1 to 4 in Table 1 use the anti-sulfur coating agent of the present invention having a different composition, and Comparative Examples 1 to 8 use a coating agent having a composition different from that of Examples 1 to 4, respectively. .

Calcium oxide CaO, iron oxide Fe ₂ O ₃ and silica SiO _{2 in} Table 1 indicate the weight percentage of the aggregate blend, and sodium silicate Na ₂ O.nSiO ₂ .mH ₂ O and water are weights relative to the aggregate. %. Table 1 shows the melting point [° C.] when casting and the data of the depth of immersion [mm] obtained from the metal structure photograph of the sample, and the remarks column shows the metal structure photograph of the sample. Indicates the figure number. 2 shows a metal structure photograph of Example 1, FIG. 3 shows a metal structure photograph of Example 2, FIG. 4 shows a metal structure photograph of Comparative Example 1, and FIG. A metal structure photograph is shown.

As shown in Table 1, the anti-sulfur coating agent of the present invention used in Examples 1 to 4 has a composition having a blocking effect, and sodium silicate Na ₂ O · nSiO ₂ · mH for the aggregate. _It contains 6 wt% ₂ O, 60 wt% water, and has a melting point of 1300 to 1400 ° C. In Examples 1 to 4, the depth of sulfuration is reduced to a problem-free range of 1.5 mm. It has become.

The coating agent used in Comparative Example 1 does not contain the aggregate of calcium oxide CaO and iron oxide Fe ₂ O ₃ and the neutralizing agent sodium silicate Na ₂ O.nSiO ₂ .mH ₂ O. The composition is 40% by weight of silica, 10% by weight of graphite, 5% by weight of clay, 5% by weight of colloidal silica, and 40% by weight of water. Comparative Example 1 shows a considerably large value of the depth of sulfuration of 12 mm. Further, the coating agent for use in Comparative Example 2 is obtained by the 1300-1400 ° C. The melting point and set the same aggregate formulation as in Example 1, adding sodium silicate _{Na 2 O · nSiO 2 · mH} 2 O Although it was not blended, the depth of sulfuration was as large as 5 mm. Further, the coating agent for use in Comparative Examples 4-8, Examples 1-4 and different aggregate formulation set respectively, sodium silicate _{Na 2 O · nSiO 2 · mH} 2 O to aggregate 6 wt% The water content is 60% by weight, the melting point exceeds 1400 ° C., and the depth of sulfuration is a large value of 3.5 to 6 mm.

The depths of sulfuration in Examples 1 to 4 and Comparative Examples 1 to 8 were determined from respective metallographic photographs. In Examples 1 to 4, as can be seen from the metallographic photographs of FIGS. 2 and 3 shown as representatives, the depth of sulfuration is a value with no problem of 1.5 mm. On the other hand, Comparative Examples 1 to 8 show large values of the sulfuration depths of 3.5 and 12 mm, as can be seen from the metallographic photographs of FIGS. When the melting point is lower than 1300 ° C., it causes casting surface roughness. However, when the melting point is higher than 1400 ° C., it is also found that the depth of the sulfurization becomes deep and the effect of preventing the sulfurization is lost. Further, the anti-sulfur coating agent of the present invention is used when the content of the neutralizing agent sodium silicate Na ₂ O.nSiO ₂ .mH ₂ O is less than 0.1% by weight with respect to the aggregate. If the coating mold becomes brittle and exceeds 30% by weight, the coating mold may crack. Therefore, 0.1 to 30% by weight of a neutralizing agent is added to the blocking agent. It is necessary to contain.

  FIG. 6 shows a three-dimensional equilibrium diagram in which data of Examples 1 to 4 and Comparative Examples 1 to 8 are plotted.

As shown in FIG. 6, in Examples 1 to 4, calcium oxide is 10 wt% to 45 wt% of the coating agent aggregate, and iron oxide is 5 wt% of the coating agent aggregate. The silica is in the range of 5% to 60% by weight of the coating material aggregate, and the melting point is in the range of 1300 to 1400 ° C. It can be seen that the depth of sulfur is a value with no problem. On the other hand, it can be seen that Comparative Examples 3 to 8 are in a region outside the paint area where the melting point exceeds 1400 ° C., and the depth of sulfuration is a high value. Comparative Example 2 sets the composition of the aggregate in the same manner as in Example 1 and does not contain sodium silicate Na ₂ O.nSiO ₂ .mH ₂ O, and has a melting point of 1300 to 1400 ° C. the depth of the sulphurized by not containing sodium silicate _{Na 2 O · nSiO 2 · mH} 2 O is seen to show a large value.

  As described above, the anti-sulfurization coating agent of the present invention can reliably prevent the sulfurization phenomenon of the casting caused by the acidic gas containing sulfur generated from the mold when casting with the organic self-hardening mold. Calcium oxide is 10% to 45% by weight of the coating agent aggregate, iron oxide is 5% to 85% by weight of the coating agent aggregate, and silica is The effect of preventing the sulfuration phenomenon is exhibited in the range of 5% to 60% by weight of the coating agent aggregate. On the other hand, if the temperature is lower than 1,300 ° C., a casting surface defect occurs in the casting, which is not preferable. Therefore, by setting the melting point from 1,300 ° C. to 1,400 ° C., it is possible to produce a sound casting that does not cause a sulfurization phenomenon and that does not cause a defective casting surface.

  The anti-sulfur coating agent of the present invention can be applied to all casting processes using an organic self-hardening mold.

  Further, the calcium oxide and silica described in the embodiment of the present invention can be used as calcium silicate, and the same effect can be obtained.

A sectional view of an organic self-hardening mold for producing a sample is shown. 1 shows a metallographic photograph of Example 1 of the sample. The metal structure photograph of Example 2 of a sample is shown. The metal structure photograph of the comparative example 1 of a sample is shown. The metal structure photograph of the comparative example 4 of a sample is shown. The three-dimensional equilibrium diagram which plotted the data of Examples 1-4 of a sample and Comparative Examples 2-8 is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Organic self-hardening mold 11 Space 12 Coating layer 12a Aggregate 12b Sodium silicate 13 Cast frame 14 Mold 15 Cup 16 Runway 17 Molten metal

Claims (5)

  The aggregate composition is formed of calcium oxide, iron oxide, and silica, and has an effect of blocking the acidic gas containing sulfur, and contains a neutralizing agent that neutralizes the acidic gas containing sulfur. Anti-sulfur coating agent for cast iron.   The calcium oxide is 10% to 45% by weight of the coating agent aggregate, and the iron oxide is 5% to 85% by weight of the coating agent aggregate, and the silica. 2. The anti-sulfurizing coating agent for cast iron according to claim 1, wherein 5 to 60% by weight of the coating agent aggregate is included.   The anti-sulfur mold for cast iron according to claim 1, wherein the melting point of the aggregate contained in the anti-sulfur mold is from 1,300 ° C to 1,400 ° C. Agent.   The anti-sulfurization coating for cast iron according to any one of claims 1 to 3, wherein the neutralizing agent contains 0.1 wt% to 30 wt% with respect to the aggregate composition. Mold.   The anti-sulfurizing coating agent for cast iron according to any one of claims 1 to 4, wherein the neutralizing agent is sodium silicate.

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