JPS59130644A - Mold coating material for furan resin casting mold - Google Patents

Abstract

PURPOSE:To prevent carburization and sulfurization of an alloy casting and to obtain a good casting surface by incorporating the slag formed in the reduction period of a steel making stage at a specific ratio in the entire aggregate as an aggregate constituting component of a mold coating material for a furan resin casting mold. CONSTITUTION:The slag formed in the reduction period of a steel making stage is added at 5-40% in the entire aggregate as an aggregate constituting component for a commercially marketed zircon mold coating material used for a furan resin casting mold, and the aggregate is adjusted to about 60 Be<-> in I.P.A. The slag is formed in the reduction period in melting a stainless steel, heat resisting steel or carbon steel and consists of about 15-40% SiO2, 40-60% CaO, <=10% MgO, <=3% FeO and others and the basicity thereof is in a range of about 1.2- 3.8. The above-mentioned mold coating material is coated on a self-curing casting mold of furan and after the mold is dried with a burner, a desired corrosion and heat resistant alloy is cast therein. The carburization and sulfurization of the alloy casting are thus effectively prevented and the good casting surface is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coating material for furan resin molds used in the production of alloy castings. The present invention relates to a coating material for furan resin molds that can prevent the above problems.

Furan resin molds, in which furan resin and a sulfonic acid curing agent are generally used as a bond, have been widely used in recent years because they have excellent productivity characteristics such as high productivity and easy recovery and recycling of old sand. ing.

However, when the Furanjuha 17 mold is poured, the resin and curing agent are thermally decomposed and C-based IS-based gases such as Go + 002 + CH4 or 5O2TH2S are generated. There was a problem that abnormal layers were formed due to carburization and sulfurization.

The presence of this abnormal layer in alloy castings is not only harmful from the standpoint of its intended use, but also harmful as it causes defects such as cracks during the manufacturing of castings. .

As a measure to prevent the occurrence of this abnormal layer, that is, carburization and sulfurization, there are conventionally known methods such as the following1)'
&Jj A method of using chromite sand as material sand.

(2) A method of adding Fe2O3 to foundry sand.

(3) Fe2O3 or N1. A method of adding various oxides, such as the hexamethod.

(4) 2CaO-8102 and GaGo as coating molds
A method using a mixture of (3) or (Ea,
Method of adding Go3.

(5) Methods of operation management (87M ratio, L, O, ■, limits on the amount of resin and curing agent added, etc.) (General Foundry Center: Examples of casting defects in organic self-hardening molds and their countermeasures 1962) March P-/?).

However, these methods have the following problems:
It is not necessarily common and its effects are insufficient.

That is, according to method (1), chromite sand is expensive, chromite sand has a high specific gravity, and mixing silica sand with chromite sand causes generation of phosphorus (for example, Meiki et al.; Casting vol.

yri (/def, 2) JIG Otsu P, 7g, P, /
? ), etc., when converting foundry sand into expensive chromite sand, the specific gravity of chromite sand is high, so in some cases it may be necessary to change equipment, and it may also be necessary to set new operating conditions. leading to increased costs. In addition, when using chromite sand only for skin sand,
Equipment for separating chromite sand from other sands is required for sand regeneration.

According to method (2), the casting strength deteriorates due to the addition of F'5203, so it is not necessarily practical. -1) March 1981 □・P, g-
9).

According to method (3), as will be described later, if the amount added is small, there is no effect of preventing carburization and sulfurization, and if the amount added is too large, the cast surface appearance will be poor.

According to method (4), the effect of preventing carburization and sulfurization is not necessarily sufficient (Tsuda et al.; Casting r/(/qtt)q
,! ;/9 and Tsuda et al.; Casting 53 (/light/),! +
12-27).

The present invention provides a coating material that can effectively prevent carburization and sulfurization of alloy castings when using furan resin molds without causing the problems of conventional methods as described above. The purpose is to

In other words, the present invention uses slag produced during the reduction stage of the steelmaking process as a constituent component of the aggregate in the coating material for furan resin molds used in the production of alloy casting products. The present invention relates to a coating material for furan resin molds, characterized in that it contains 9 to aO%.

The mold coating material of the present invention does not require changes to existing operating methods such as changing the molding sand or changing the molding method, unlike conventional methods, when producing alloy castings using furan resin molds. This can be easily done by simply adding slag to the coating material as described above, and this can more effectively prevent carburization and sulfurization caused by the use of furan resin molds than ever before. .

The main function of the coating mold is normal f1. The objective is to obtain a cast surface appearance, and the above-mentioned functions are completely achieved even when using the mold coating material of the present invention, and this point also differs from conventional mold coating materials and methods.

The present invention will be explained in detail below.

The casting humidity (9) of alloy castings is /! ;gO~/6θθ°C
This relatively high temperature makes it easy for the bath water to penetrate between the sand grains and for the amount of phosphorus in the sand grains to reach the casting surface. Therefore, it has a cast surface appearance.

Coating molds are required from the standpoint of casting quality. Therefore, if carburization and sulfurization can be prevented using only the coating mold, normal castings can be manufactured without changing the existing casting manufacturing method.

Therefore, we first added known additives that are known to have a Uj-stopping effect during carburizing and bamboo soaking to a heavy zircon-based coating material, and conducted a casting test to actually evaluate the performance of these additives. This test was conducted under the casting conditions shown in Table 1, and the results are shown in Table 2.

Table 1 Mold; flan self-hardening mold molding sand; recycled sand (mixed sand of zircon sand and silica sand) casting fl
HfAk; JIS G5/, 2/ A test piece coating material; various additives were added to a commercially available zircon coating material; 1. P
, A to approximately t, o B- Adjustment coating application; Brush coating, burner dry casting MUlf; SC8/, y (Molten metal composition C: 0
．． OA%.

S20, θo4t%) Casting temperature; /sgo -1too℃ Table 2 Notes: Content weight (%) of additives in the coating aggregate 0:
The content is unknown because it was not analyzed.15 The commercially available zircon-based coating material uses zircon flour as an aggregate, an organic binder, an organic compatibilizer, and 1. It consists of P and A (isopropyl alcohol), and the amounts of various additives added to the painted □ mold material were such that the content in the painted mold aggregate was the value (%) shown in Table 1. Carburization or sulfurization is observed even when additives (either singly or in combination) are added, and the appearance of the cast surface is impaired, and the carburization and sulfurization prevention effect is insufficient, and the coating material It is clear that it has lost its original function.

That is, in the furan resin mold, the resin curing agent is thermally decomposed by pouring, so the inside of the mold becomes a reducing atmosphere. Therefore, the addition of Fe2O2, which is an oxygen supply source, is effective in making the atmosphere oxidizing, and in fact, in this test, the oxide scale was lower than when a commercially available zircon coating (without additives) was applied. An increase was observed in the number of spawned shellfish. However, when the amount of addition is small as shown in Table □, it is not possible to increase the O potential to the inside of the casting surface scale, and the mold atmosphere has a high C2S potential to begin with, resulting in carburizing and oxidation. The effect of preventing sulfur is not sufficiently recognized. On the other hand, if the amount of Fe2O2 added is too large, the appearance of the casting surface will be poor as shown in the same table, and from this point of view it cannot be applied to actual production.

Furthermore, when other additives, such as CaO+CaCO3 or a combination thereof with Fe2O2, are added, the effect of preventing carburization and sulfurization is insufficient, or the appearance and quality of the cast surface are insufficient, so that they cannot be applied to actual production. Therefore,
With the aim of developing a coating material that can sufficiently prevent carburization and sulfurization on stainless steel #4, we investigated various new effective coating additives and found that they are formed during the reduction stage of the steelmaking process. It has been found that slurry is effective in sufficiently preventing carburization and sulfurization. In addition, we investigated the performance of mold coating materials with this slag added to other casting products, such as heat-resistant steel, corrosion-resistant heat-resistant alloys, etc., and found that, like stainless steel, it effectively prevents carburization and sulfurization, and provides a good cast surface appearance. It has been confirmed that it can be obtained.

In order to further clarify the contents of the mold coating material of the present invention, some of the test results conducted in 1-- will be explained below.

Table 3 shows the casting conditions, and Table 9 shows the component analysis values of the slag used in the test.

Table 3 Mold: Furan self-hardening mold Molding sand; recycled sand, zircon sand, silica sand.

Chromite sand mold shape: JIS Cr5i21A test piece coating Mold material: Slag was added to a commercially available zircon-based mold material.1. P, A
Adjusted to approx. 6° 8 stones at 100 yen; Brush-coated cast steel fg: SO8s (o, o, 5'%G r
0-ttub 7゜(component, @/rigo -/goo
'C) Suitable temperature) SC8/, O (o, o□C, 0,001
1%S.

isgθ-/A00℃) SCH/, 3(o,, yo%G, o, oot%s.

l left 10-/riti, o℃) Hastelloy C (o, oq%c, o,ooq%S.

/gso℃) 14Eq The slag with λ/~7 in the table is stainless steel,
It is produced during the reduction period of melting heat-resistant steel or carbon steel, that is, during the reduction period of the steelmaking process, and its composition is approximately 5102/j
~lIO%, CaO/1. θ~60%, MgO10
%below.

Consisting of less than FeOJ% and others, basicity is low ~ JJ
is within the range of This Ag slag is produced during N1 refining and was used for comparison.

These slags were mixed with a commercially available zircon-based coating material (Zirconofuran is the aggregate and contains an organic binder and an organic compatibilizer.
A is used as a solvent), and then P and A are added to make about b
o After moisturizing to B≦, it was applied to a furan self-hardening mold, and after drying with a burner, various alloys were cast. Table 5 shows the results.
The results of analysis and appearance evaluation of the cut surface of various alloy castings when various contents of slag A/~g in Table 1I are added to the skeleton of the coating material are shown.

Table 5: When the cislag content is 3%, the component of the cast surface is C.
is 0.10% or more, and S is more than 0.02θ%, which shows that they increase due to carburizing and sulfurizing. A microscopic photograph of the cross section of the casting surface of this sample is shown in FIG.

According to the SO8/3 standard, S is 0.0% or less, but when Si increases as in this sample due to sulfurization, sulfide is concentrated on one side of the skin. It will be done. When TIG welding is performed on such a cast surface, HAZ cracking or vertical bead cracking may occur. Therefore, cj: sulfurization is recognized in terms of analytical values, but S is 0.020%, where concentrated sulfides are not actually recognized microscopically.
The following range was determined to be a cast surface in which sulfurization was prevented. Ike's alloy relics were also evaluated using the same method.

Regarding carburization (rl, S' In the case of SC8/3, the normal microscopic structure (co-phase structure of austenite and δ ferrite) disappears on the casting surface and becomes a single phase of austenite, and the thickness of that layer is Q. , 2 myh or more, and where point-like carbides were partially observed, C was 0 in this test.
0.010% or more, the cast surface analysis value was 0.1.
The range below 0% was determined to be a cast surface in which carburization was prevented. When the slag content is 3%, the quality of the cast surface surface deteriorates due to carburization and 4-sulfurization, while when the slag content is 5%, both carburization and sulfurization are lower than the above analytical values, and the quality of the cast surface surface is lower than the above analysis value. The appearance was also good. Therefore, the lower limit of the slag content in the present invention is set to 5%.

Next, if the slag content is Otsu 5%, SO8 shown in Table 5
/,? It was found that the cast surface appearance deteriorated as in the case of
On the other hand, if the slag content is lIO%, carburization is performed.

Both sulfurization values are lower than the above analysis values, and the cast surface appearance is good, so the upper limit of the slag content is set at tio%.

In view of the above, in the mold coating material of the present invention, when the mold coating material aggregate content is 5 to θ% in the total aggregate, carburization and sulfurization can be effectively prevented and a good casting surface appearance can be obtained.

Regarding the types of slag, Table 5 shows that there are 2 types of slag.
All of the slags A/ to 7 had good results in the first analysis of the casting surface and the evaluation of the appearance of the casting surface, and fully satisfied the function of the mold coating material of the present invention.

Incidentally, the reducing slag obtained by the 1'IT1 refining of ilag has no effect of preventing carburization and sulfurization.

Next, the particle size of the slag was tested and the results are shown in Table 6. The casting conditions are the same as in Table 3 (only the molten metal composition differs).

/ From the results in Table 4, it can be seen that finely packed slag with a particle size of 10θ mesh or more is sufficiently effective as an aggregate for the mold coating material of the present invention.

The above has described the study results for the mold coating material of the present invention. Conventionally, it has been thought that the aggregate for the mold coating material needs to have sufficient fire resistance from the viewpoint of preventing poor casting surface appearance, such as by preventing the amount of phosphorus. was.

On the other hand, the mold coating material of the present invention uses slag produced during the reduction stage of the steelmaking process, which has a relatively low fire resistance, as the aggregate g acid component of the mold coating material, without impairing the original function of the mold coating material, and by carburizing using a furan resin mold. - Sulfurization can be prevented like never before.

Next, examples of the mold coating material of the present invention will be described.

Example 1 A commercially available zircon coating material and a coating material of the present invention (no. 9 Mix the slag and zircon coating material in the ratio of /:9,
5%, 0.3%, and 3% of organic binder, surfactant, anti-settling agent, etc. were added to the aggregate, and the mixture was adjusted to θB with water and applied separately. ζSUS 32q
J is equivalent to the casting temperature of molten stainless steel it, oo℃
It was cast in The microscopic structure (etched with Murakami's reagent) of each part of the casting surface of the obtained casting is shown in Figures 2 (a) and 2 (b). Figure 2 (a) shows the casting surface of the part coated with the coating material of the present invention, which shows the normal structure of this steel, and microscopically, no carburization or sulfurization was observed. (Note that some black parts are in the σ phase).

On the other hand, Figure 2 (b) shows the casting surface of a part coated with a commercially available zircon coating material. Due to the carburization from the 7-run resin mold, the structure has changed and the base is austenite C (white part). The ratio of ferrite and austenite is reversed. Carbide due to carburization is observed in the reduced ferrite, which appears pale black in the photo.

The dark black areas are groove-like grooves formed by etching of sulfides produced during sulfurization.

As described above, an abnormal layer was observed up to a depth of approximately 5 ann on the casting surface coated with a commercially available zircon coating material.

Example 2 SC81.3 ball valves were cast using furan resin molds (zircon sand) with different coatings. For the furan resin mold, as a coating material of the present invention, chromite powder g, s part, slag (Table 1) / 0 parts and organic binder + organic compatibilizer (7, 5 parts) were added. Mix chromite powder Nislag-g9. evening: lo, s),
As a mold coating material according to the conventional method, an equal amount of Caco 3 was added and mixed in place of the slag in the above formulation, and 1
．． P: * was used which was adjusted to bo B6. The microscopic structure (electrolytically etched with 70% oxalic acid) of the cross section of each cast ball valve flange (flange thickness, 2 parts mi) is shown in FIGS. 3(a) and 3(b). (A) is made of a mold coated with the mold coating material of the present invention, and SC
It has become a normal tissue of 8I3. On the other hand, (b)
is made from a mold that has been coated using the conventional method, and fA jJJ! is made by carburizing. The surface is a single phase of approximately O1 taryu austenite (δ7 elite has disappeared), and dotted sulfides (black) due to sulfurization are also observed.

As is clear from the comparison with the mold coating material made by the conventional method shown in the above examples, it can be seen that the mold coating material of the present invention is less effective in preventing carburization and sulfurization than the mold coating material made by the conventional method.

The effects of the present invention are summarized as follows.

(1) By using the mold coating material of the present invention as a mold coating material for furan resin molds, carburization and sulfurization can be more effectively prevented than in conventional mold coating materials, and a good casting surface appearance can still be obtained.

(2) Casting defects caused by carburizing and sulfurizing with furan resin molds are eliminated.

(3) Since there is no carburized or sulfurized layer on the casting surface of PJJ products, the quality of the cast products improves.

(4) There is no need to remove carburized and sulfurized layers on the casting surface of fQj products, reducing machining man-hours and improving yield.

(5) Since the slag used in the present invention is industrial waste generated in the steel manufacturing process, it can be used effectively.

The mold coating material of the present invention is intended to prevent carburization and sulfurization of alloy castings, but it is also effective for cast steel in general or cast iron, where the casting temperature in furan resin molds is close to that of alloy castings. It goes without saying that there is.

[Brief explanation of the drawing]

Figure 1 shows the cross-section of the casting surface when SC81,y was casted by adding an insufficient amount (3%) of slag A/ to the furan resin mold. Micrograph (not etched) showing dust, Figure 2 (A)
, (b) is SUS,? Photographs showing the microscopic structure of each section of the casting surface l'I'iI when a stainless steel casting equivalent to Kowa J was manufactured using a furan resin mold. (A)
(b) is the structure of the cross section of the casting surface in the part to which the mold coating material of the present invention was applied, and (b) is the structure of the casting surface cross section in the part to which the mold coating material according to the conventional method was applied. Figure 3 (a) and (b) are
5 by furan resin molds with different coatings.
The photographs show the 7-flange cross-section of each cast C8I30 ball valve (not shown). This is the case of a mold coated with a conventional method. Patent applicant Nippon Yakin Kogyo Co., Ltd. Representative Patent Attorney Mura 1) Politics Figure 1 Figure 2 (a)

Claims (1)

[Claims] 1. In the coating material for furan resin molds used in the production of alloy casting products, 5-xi-
A coating material for furan resin molds, characterized by containing o% gold.