JP2001071094A - Filler for lost foam pattern mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the structural defect caused by the expansion of a filler and to obtain the excellent dimensional precision by using the filler for a mold, consisting essentially of a forsterite or a protoenstatite or the mixture thereof obtained from molten slag of nickel ore slag and containing at least MgO and SiO2 and having the spherical shape of not more than a specified granular shape coefficient. SOLUTION: This filler for a lost foam pattern mold is composed of the molten slag having <=1.2 granular shape coefficient and containing 1:2-2:1 wt. ratio of MgO and SiO2. The molten slag is desirably the one executing a blast granulating treatment. To the whole filler, it is desirable to contain by wt.% of 67-50 MgO and 33-50 SiO2, and for improving the refractoriness, it is desirable to add Al2O3 so that MgO+SiO2:Al2O3 becomes 90-80:10-20 by wt.%. Molten metal is poured into the pattern made of polystyrene, etc., which can be lost with the molten metal, to form a casting.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filler for a disappearing model mold (hereinafter simply referred to as a filler). More particularly, the present invention relates to a filler having very ideal properties.

[0002]

2. Description of the Related Art Various methods have been proposed for producing castings. Among them, there is a vanishing model casting method called a full mold method.

In this method, a casting (product) desired to be cast is used.
Is modeled with a resin such as styrene foam, and the model is embedded in a filler in a casting flask, and is subjected to normal pressure or reduced pressure (−5).
This method is a method in which a molten metal is poured under a pressure of 0 to -200 mmHg to remove a model and replace it with a metal to form a casting.

[0004] Fillers used in the vanishing model casting method include:
Generally, self-hardening sand like natural silica sand is used,
If necessary, an organic binder such as a furan resin or a phenol resin or an inorganic binder such as sodium silicate is added. The binder plays a role of improving the shape retention of the self-hardening sand.

[0005]

Here, natural silica sand, which is generally used as a filler, expands when molten metal is poured, so that the dimensional accuracy of the obtained casting is limited.

The filling of the filler into the flask is performed around the model placed in the flask while vibrating the flask. The filler needs to be uniformly and firmly filled.
However, natural silica sand has poor flowability due to its polygonal grain shape, and it has been particularly difficult to fill the horizontal holes and the convex portions on the lower surface of the model with respect to the vibration direction.

[0007] Furthermore, natural silica sand has a problem in that the particle shape is polygonal, so that the air permeability is not sufficient. If the air permeability is poor, the gas generated when the model disappears cannot be quickly discharged to the outside. As a result, "soot" derived from the gas may remain in the casting, resulting in a defective product. . As another problem, when casting while reducing the pressure,
If the air permeability is poor, it is necessary to further increase the degree of pressure reduction. As a result, there is a problem that a molten metal flows between the fillers (insertion phenomenon) and the casting surface of the casting becomes rough.

Further, from the viewpoint of improving the working environment and reducing the amount of industrial waste, which have been of increasing interest in recent years,
Since natural silica sand has a polygonal shape, there is a risk that, when a casting is formed and a filler is collected after the formation, thermal cracks are generated and sand is brought into contact with each other to cause breakage and dust.
As a result, the working environment may be degraded, or the recovery efficiency may be degraded due to damage, and a large amount of industrial waste may be generated.

[0009]

Thus, according to the present invention, a forsterite or protoenstatite obtained from a molten slag of nickel slag and containing at least MgO and SiO ₂ or a mixture thereof is used as a main component. A filler characterized by having a spherical shape having a shape factor of 1.2 or less is provided.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION

[0011] The filler of the present invention comprises a natural nickel ore.
Is the molten slag generated as a by-product melted in an electric furnace?
Can be obtained from The filler is at least MgO and S
iO _TwoForsterite or protoenste containing
Tight or a mixture thereof is a main component. This
Since the coefficient of thermal expansion is extremely low, a highly accurate casting is formed.
Can be achieved. Also, it is hard to cause thermal crack
The filler itself is less likely to be damaged, and the recovery rate is improved.
Can be improved. As a result, the generation of industrial waste
The amount can be reduced. The main component is 50% by weight or less.
Above, preferably means 60% by weight or more.

Here, forsterite is 2MgO · S
It is represented by iO ₂ , while protoenstatite is MgO
It is represented by SiO ₂ . In addition, forsterite is 160
It is about 0 ° C, while protoenstatite has a fire resistance of about 1450 ° C. Therefore, it is preferable to use a molten slag containing forsterite as a main component for a metal such as stainless steel which requires a high temperature for casting.

However, even when the obtained molten slag contains protoenstatite as a main component, the MgO component is added to make the composition of MgO and SiO ₂ 2: 1 (weight ratio).
, Similar fire resistance can be obtained. M
gO can be added to the filler melted by an electric furnace or the like in the form of magnesia clinker, seawater magnesia, or the like.

The filler is made of SiO ₂ as a whole.
May be contained twice or more as much as MgO. The composition ratio of MgO and SiO _{2 in} the entire filler is 67 to 50% by weight.
And preferably in the range of 33 to 50% by weight. Mg
As components other than O and SiO ₂ , components derived from nickel ore and / or components mixed during refining (for example, Fe
₂ O ₃ , Al ₂ O ₃ , CaO, etc.).

Further, in order to increase the fire resistance, Al ₂
O ₃ may be added. For example, when Al ₂ O ₃ is added to a molten slag containing forsterite as a main component, the fire resistance can be improved by about 100 ° C. In particular, Al ₂ O ₃
Is preferably contained in the filler in an amount of less than 20% by weight. The content of Al ₂ O ₃ is more preferably from 10 to 20% by weight, and even more preferably from 10 to 15% by weight. As a raw material of Al ₂ O ₃ , industrially,
Examples include fused alumina, sintered alumina, mullite, dice bore, and bauxite. These raw materials are Al
_{Since 2} O ₃ is contained at an arbitrary ratio of about 50 to 99.3% by weight, it is preferable to add it to the molten filler while adjusting the content so as to be in the preferable range described above. More specific filler the overall composition, the total content of MgO and SiO _2: Al ₂ O ₃ is 90 to 80 wt%: 10 to 20 wt%
It is preferable that

The filler has a particle size coefficient of 1.2 or less, preferably 1.1 or less. When it is 1.2 or less, the filling rate is improved, and the air permeability of the mold is improved. Further, since the shape is close to a sphere, it is possible to prevent the generation of dust at the time of collection due to contact between the fillers.

The above-mentioned particle size coefficient means a value calculated using a sand surface area measuring device (manufactured by George Fisher). That is, the grain shape coefficient means a value obtained by dividing the actual surface area of the sand particles per gram by the theoretical surface area. The theoretical surface area refers to the surface area assuming that all sand particles are spherical. Therefore, the closer the grain shape coefficient is to 1, the closer to a sphere.

The filler of the present invention preferably has a particle size distribution of 30 to 850 μm, more preferably 53 to 590 μm. When the diameter is smaller than 30 μm, the air permeability decreases, which is not preferable. When the diameter is larger than 850 μm, the surface of the casting is unfavorably roughened.

Here, the particle size distribution in the present invention is determined by JI
It refers to the value measured according to the particle size test method (Z2601) of the molding sand of S. When this method is schematically described, for example, a 850 μm sieve is placed on a sieve having a nominal size of 30 μm, and the raw material is placed on the 850 μm sieve.
Using a sieving machine such as a low tap sieving machine, the residue between the two sieves is reduced to a particle size distribution of 30-8.
It is referred to as a 50 μm filler.

Further, the filler of the present invention may optionally contain a binder for maintaining the shape at the time of casting. However, the amount of the binder is preferably as small as possible because it has the effect of preventing the filling of the filler and causing soot defects by remaining during casting. Specifically, it differs depending on the type of the binder, but based on the total amount of the filler,
It is preferable to use an amount of 1.0% by weight or less. In addition,
Examples of the binder include an organic binder such as a phenol resin and a furan resin, and an inorganic binder such as sodium silicate. The binder may contain a known curing agent (for example, organic acids such as oxalic acid, formic acid, and acetic acid, and amine compounds such as hexamethylenetetramine and trimethylamine).

The filler of the present invention can be obtained by subjecting molten slag to air blasting. The blasting process, in the blaster,
In this process, the slag is rapidly cooled by the wind sent by the blower to make it into a fine sphere. This air crushing treatment is not special, and for example, an atomizing method generally used as a method for producing glass spheres and shot spheres can be used.

After the above-mentioned air crushing treatment, a grinding treatment may be further performed. For the grinding treatment, any of the known dry method and wet method can be used.

In the dry method, the raw material is raised in the apparatus by a high-speed air flow and collides with an impingement plate, so that the raw material is pulverized by the impact and friction between the raw materials. A high-speed rotating scrubber device that puts raw materials on the top and performs grinding processing by collision and friction between the projected sand generated by centrifugal force and falling sand, and an agitator mill that performs grinding processing using friction between sand particles And the like using a high-speed stirrer.

On the other hand, the wet method includes a method using a grinding machine such as a trough type in which a grinding process is performed by friction between sand grains in a trough in which blades are rotated. It is preferable to use a wet method among these grinding processes. This is because sand smaller than the desired particle size can be simultaneously removed by the water washing during the grinding processing. However, even in the dry method, the same level of filler as in the wet method can be obtained by installing a water washing device.

The filler of the present invention is used in a vanishing model casting method. This method is briefly described as follows. First, a model having a shape desired to be cast is prepared from a material that can be lost by a molten metal, and the model is placed in a flask, and a filler is charged while vibrating the flask. After that, the molten metal is dropped and injected by push-up or horizontal casting, thereby removing the model and replacing the position with the molten metal to obtain a casting having a desired shape.

Examples of the material which can be eliminated by the molten metal include polystyrene, polymethyl methacrylate, a copolymer of both, and a foam of a mixture of both. A coating film for maintaining the shape may be formed on the surface of the model. The coating may use a material referred to in the art as a ceramic shell.

Next, the filler is charged while the flask is vibrated. With the filler of the present invention, the filling rate after vibration is 1.7.
g / cm ³ or more. This is a high value as compared with that of conventional natural silica sand of about 1.6 g / cm ³ . When the filling rate is high, the surface of the obtained casting can be made smoother. More specifically, J
A surface roughness of 1 was measured by a measurement method according to IS B 0651.
It can be less than 4.0 μm.

Further, the molten metal is not particularly limited, and examples thereof include molten materials such as aluminum, iron, and stainless steel. The model disappears due to the molten metal, but when the model disappears, a gas which causes soot defects is generated. In order to discharge this gas out of the flask, it is desired that the filler has a predetermined air permeability at the time of filling. In the present invention, JIS Z 2
With a measurement method based on 601, an air permeability of 1360 cc / min or more can be obtained. In addition, in natural silica sand,
Generally, it is 800 cc / min or less. The molten metal is injected at room temperature or under reduced pressure (−100 to −300 m).
mHg).

After forming the casting of the desired shape, the used filler can be easily reprocessed in the present invention. The method for reprocessing is not particularly limited, and any known method can be used. The filler of the present invention,
The particle shape coefficient is close to a sphere of 1.2 or less, and MgO and SiO ₂
Since it is made of a specific crystal composition containing the compound, damage or thermal crack due to contact between the fillers is unlikely to occur, so that the initial characteristics can be maintained. Therefore, reprocessing is easy. Specifically, even if the casting and reprocessing are repeated 10 times, 99% by weight or more can be reused.

[0030]

Embodiments of the present invention will be described below. Note that the present invention is not limited to the following embodiments.

Production Example After drying a natural nickel ore (from New Caledonia) with a dryer, anthracite and limestone were added in a rotary kiln, and the resulting mixture was scoured in an electric furnace. The molten slag generated in the nickel refining step was subjected to air-milling to obtain a filler for a disappearing model mold of the present invention. Table 1 shows the chemical composition of the obtained filler. Table 1 also shows the chemical composition of natural silica sand (from Mikawa) for comparison.

[0032]

[Table 1]

The fire resistance of the filler of the present invention is about 145.
It was 0 ° C.

Example 1 A 50 mmφ × 50 mm cylinder was naturally filled with the filler of the present invention and natural silica sand, and then the cylinder was vibrated under certain conditions. The filling rate was determined by measuring the height of the filler of the present invention and natural silica sand after vibration. Table 2 shows the results.

[0035]

[Table 2]

Table 2 shows that the filler of the present invention has an extremely high filling rate.

Example 2 A binder made of a phenolic resin (Kao Step: manufactured by Kao Quaker) and an organic ester (manufactured by Kao Quaker), which is generally used in the full molding method, was used as a filler of the present invention. Mixed with natural silica sand. Using these fillers, the mold strength (compression strength) was examined. The strength of the mold was measured after standing for 24 hours according to the JACT test method. The amount of the resin added was 0.5% by weight, 0.7%
% And 1.0% by weight, and the organic ester was used in a ratio of 25% by weight to the resin. Table 3 shows the results. Table 3 also shows, for comparison, the mold strength when natural silica sand and recycled silica sand (regenerated sand of natural silica sand from the full molding method) were used instead of the filler of the present invention.

[0038]

[Table 3]

Table 3 shows that the filler of the present invention has higher mold strength than natural silica sand and recycled silica sand, and can reduce the amount of resin added when it is desired to obtain the same mold strength. Specifically, in the case of the full mold method, it is said that a mold strength of about 10 to 15 kg / cm ² is sufficient. Looking at Table 3 from this perspective,
In the case of recycled silica sand, 0.7% by weight of the resin is required, but in the filler of the present invention, 0.5% by weight or more provides a higher strength. Moreover, 1000 when the resin is 0.7% by weight.
The coefficient of thermal expansion at ℃ was measured. The coefficient of thermal expansion was measured using a differential thermal expansion meter (TMA8140, manufactured by Rigaku Corporation). Table 4 shows the results.

[0040]

[Table 4]

From Table 4, it can be seen that silica sand has a coefficient of thermal expansion of 1.2 to 1.5, whereas the filler of the present invention has a coefficient of thermal expansion of 0, and does not expand or contract. It has been found that a template can be provided.

Example 3 The filler and the natural silica sand of the present invention were used for casting by the full molding method as described below, and the casting surface of the obtained product was observed. A styrofoam model of 50 cm × 50 cm × 50 cm was used, placed in a flask, and filled with the filler of the present invention and natural silica sand while vibrating the flask. To the filler and the natural silica sand of the present invention, 0.5% by weight of a phenol resin and 25% by weight of an organic ester based on the resin were added. A cast iron melt conforming to JIS standard FC250 was cast into this mold at 1470 ° C., cooled, taken out of the mold, and examined for a casting surface on the product surface. The cast surface was evaluated based on the average surface roughness. The average surface roughness was measured using a surface roughness measuring device (Mitutoyo Surf Test 301) according to JIS.
Performed according to B0651. Table 5 shows the results.

[0043]

[Table 5]

From Table 5, it was found that the filler of the present invention had a smaller surface roughness of the casting surface than natural silica sand and had a good casting surface. Furthermore, 10 cm of the upper surface of the obtained product
The number of soot defects (pinhole defects) in the range of × 10 cm × 10 cm was measured. Table 6 shows the results.

[0045]

[Table 6]

From Table 6, it was found that the filler of the present invention did not have any soot defects, and the surface condition of the product was more preferable. This is considered to be due to the influence of the air permeability of the mold evaluated in Example 4 below.

Example 4 In the full mold method, if the gas generated by the disappearance of the model at the time of casting cannot escape to the outside through the mold, the gas remaining in the mold remains as soot defects in the product. Sex is important. In the following, a mold (50 mmφ ×
50 mm), and its air permeability is determined according to JIS Z 260
1 was measured. The filler and the natural silica sand of the present invention were added with a phenol resin at 0.7% by weight and an organic ester at 25% by weight / resin. Table 7 shows the results.

[0048]

[Table 7]

From Table 7, it can be seen that the mold using the filler of the present invention had good air permeability, and showed about 1.5 times or more the air permeability as compared with polygonal natural quartz sand. Therefore, it was found that the gas remaining in the mold can be reduced, and as a result, soot defects can be prevented.

Embodiment 5 In recent years, it has been desired to improve the generation of dust due to collection, a reduction in collection efficiency due to chipping and cracking of the filler at the time of collection, and the generation of industrial waste. From these perspectives,
The collection efficiency of the filler and the natural silica sand of the present invention was evaluated by the following method. (1) The filler and the natural silica sand of the present invention are put into a pulverizer (a table-top ball mill manufactured by Irie Shosha) and pulverized for 20 minutes.
The crushing rate after repeating the measurement was measured (based on the JACT method). The crushing rate was obtained by measuring the particle size distribution before crushing and the particle size distribution after crushing according to the AFS standard, and expressed as a percentage of the particle size distribution after crushing with respect to the particle size distribution before crushing. In addition, 1000 ° C
The crushing ratio was measured for those fired in the above and those not fired. Table 8 shows the results.

[0051]

[Table 8]

From Table 8, it was found that the filler of the present invention caused less crushing wear and less thermal deterioration than natural silica sand. (2) A model made of styrofoam of 50 cm × 50 cm × 50 cm is placed in a flask, and while the flask is vibrated,
1000 kg of the filler of the present invention containing 0.5% by weight of a phenol resin and natural silica sand were each filled. Next, a cast iron melt conforming to JIS standard FC250
The product was cast at 0 ° C., and after cooling, the product was taken out. Thereafter, the used filler of the present invention and the natural silica sand were passed through a commercially available collector (Kinki Casting Co., Ltd., Sand Fresher) and used again as a mold. The above process was repeated 10 times, and the recovery rate was measured each time. Table 9 shows the results.

[0053]

[Table 9]

From Table 9, it was found that 99% of the filler of the present invention could be recovered by repeating the casting 10 times, but only 87% of the natural silica sand could be recovered. From Example 5 described above, it was found that the filler of the present invention had little dust at the time of collection, had good collection efficiency, and had little industrial waste.

Example 6 A comparison between the filler of the present invention and a commercially available filler is made as follows. Cerabeads (manufactured by Naigai Ceramics Co., Ltd.), which is a mullite ceramic, was used as a commercially available filler. This filler is composed of 61% by weight of Al ₂ O ₃ and 35% by weight of Si.
Mainly containing the chemical component of O ₂ , a grain shape factor of 1.05,
It had a particle size distribution of 210-410 μm.

Electron micrographs of the filler of the present invention and a commercially available filler were taken. As a result, the surface of the filler of the present invention was extremely smooth, but the commercially available filler had fine irregularities. The difference between the two is that the filler of the present invention is obtained by subjecting the melt of the raw material to air crushing, whereas the commercially available filler is obtained by spray drying the raw material in a semi-molten state. Is considered to be the cause.

Further, using the filler of the present invention and a commercially available filler, the amount of residual resin when casting was repeated was measured as follows. First, 0.5% by weight of a phenol resin and 25% by weight of an organic ester based on the phenol resin were added to the filler of the present invention and a commercially available filler, respectively. A model made of styrene foam of 50 cm × 50 cm × 50 cm was placed in a flask, and the filler was filled with 1000 kg while vibrating the flask. Then
1470 ° C of cast iron melt conforming to JIS standard FC250
And the product was taken out after cooling. Thereafter, the used filler and the natural silica sand of the present invention were regenerated with a commercially available rotary reclaimer (manufactured by Nippon Casting Co., Ltd.) and used again as a mold. The above process was repeated five times, and the residual resin amount was measured each time. Table 10 shows the results. The amount of residual resin is LOI
%.

[0058]

[Table 10]

From Table 10, it was found that the filler of the present invention had less residual resin than the commercially available filler. This is because the surface of the filler of the present invention is much smoother than a commercially available filler, so that the resin adhered to the filler after casting is easily peeled off at the time of regeneration, and the resin does not remain on the surface of the filler. On the other hand, commercially available fillers have fine irregularities on the surface, so the resin adhered after casting has digged into the irregularities,
It remains in an adhered state and is hardly peeled off during reproduction, so that the amount of residual resin increases. When the amount of the residual resin increases, the strength of the mold composed of the regenerated filler deteriorates, and the residual resin at the time of casting is decomposed to generate a gas that generates a casting defect. Next, in the same manner as in Example 2, the mold strength of a commercially available filler was measured. Table 11 shows the results together with the mold strength of the filler of the present invention.

[0060]

[Table 11]

From Table 11, it can be seen that the filler of the present invention has a low resin content and a large mold strength as compared with a commercially available filler. This is believed to be due to the smooth surface of the filler of the present invention.

[0062]

The filler for a vanishing model mold of the present invention has a low expansion property, so that casting defects (vaning and mold cracking) due to the expansion of the filler in the cast product are prevented, and the dimensional accuracy is further improved. be able to. Further, since the gas permeability is good, a defect (soot defect) due to the gas remaining during casting can be prevented. Furthermore, since it is substantially spherical, the amount of the pressure-sensitive adhesive can be further reduced, so that not only is it economical, but also the disintegration of the mold after casting is good.

Further, since the raw material is spherical and hard, it is not crushed at the time of recovery and regeneration, so that the recovery rate is high and the amount of dust can be reduced. Therefore, the working environment can be improved, the generation of industrial waste is small,
It is a very industrial valued filler that meets the needs of the times.

Claims (5)

[Claims] 1. A method comprising: obtaining from a molten slag of nickel slag;
What is claimed is: 1. A filler for a vanishing model mold, which is mainly composed of forsterite or protoenstatite containing at least MgO and SiO ₂ or a mixture thereof, and has a spherical shape with a grain shape coefficient of 1.2 or less. _2. The weight ratio of MgO to SiO ₂ is 1: 2 to 2.
The filler according to claim 1, wherein the ratio is 2: 1. 3. The filler according to claim 1, further comprising MgO, Al ₂ O _3, or both. 4. The filler according to any one of claims 1 to 3, wherein the filler for the disappearing model mold is obtained by subjecting a molten slag to a pulverization treatment. 5. The filler according to claim 4, wherein the filler for the disappearing model mold is obtained by subjecting the molten slag to a pulverization treatment and then a dry or wet grinding treatment.