JP2000343180A - Evaporative pattern casting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an evaporative pattern casting method for reducing carbon absorption into a casting by effectively burning the evaporative pattern. SOLUTION: This method comprises a step for applying mold coating, to which a fiber reinforcing material is mixed in advance, on an evaporative pattern so as to perform dry-solidification or drying after self-hardening, a step for submerging the dried pattern in a casting mold material so as to form a casting mold, a step for burning and evaporating the evaporative pattern in the casting mold while supplying oxygen and the mixing air, and a step for injecting the molten metal into a space formed by combustion so as to perform casting.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a casting method for reducing carbon absorption from a disappearing model that burns and disappears to a casting during casting in a disappearing model casting method for casting a molten metal. The present invention relates to a casting method for reducing carbon absorption into a casting by efficient combustion.

[0002]

2. Description of the Related Art In a vanishing model casting method, a model having a desired shape is manufactured from expanded polystyrene (EPS), which is an organic foam, or expanded polymethacrylate (EPMMA) having an improved decomposability. The foam model is embedded in molding sand (self-hardening sand) to which a binder such as water glass or furan resin has been added, or in molding sand or shot (fine iron particles) without a binder (hereinafter referred to as mold material). This is a casting method in which molten steel is poured as it is without removing the model, and the model is disassembled and replaced by the heat to obtain a cast product having a desired shape.

[0003] The vanishing model casting method is an extremely efficient casting method because a core for forming a cavity of a cast product is not required and its assembly is not required. This casting method has an advantage that there is no limitation in the weight and dimensions of the cast product because products from several gr to several Ton can be cast.

[0004] On the other hand, the Replicast CS method (for example, J
ACT NEWS No. 332, 4th edition mold making method)
In this method, a slurry for precision casting (slurry) is applied over a foam model for vanishing model casting instead of a wax model for precision casting, and solidified and dried. Next, the whole model coated with the slurry was placed in a firing furnace at about 1000 ° C., and the slurry was fired and the foam model was burned and disappeared at the same time, and a thin ceramic shell having a hollow inside was manufactured. The sand fork is a casting method of filling in a shot, forming a mold, and casting.

[0005] The feature of this Replicast CS method is that the foam model is burned and disappeared before casting.
The point is that carbon can be prevented from entering the product due to decomposition of the foam model. This replicast CS method is capable of casting low-carbon stainless steel, whose carbon content is severely restricted, without any problem. However, this method is basically a precision casting method and can cast a precise small object, but cannot be applied to a relatively large cast product due to the strength of a thin ceramic cell.

[0006]

The general vanishing model casting method has an advantage that there is no limitation in weight and dimensions.
Injected molten metal, for example, the foam model is burned directly by the heat of the molten steel, so carbon and other gas components enter the molten steel from the decomposition gas generated in the process of burning and disappearing, if viewed from the molten steel side Absorption is inevitable.

[0007] Therefore, in the completed casting, an unstable carbon content of 0.05 to 0.45 wt% with respect to the original molten steel occurs. Therefore, the carbon content of the molten steel is originally large, and it is often used for cast iron (generally C = 2.5 to 3.5 wt%) in which penetration of the carbon component by decomposition of the foam model does not pose a problem. However, the carbon content of molten steel is small, and the carbon content increases due to decomposition of the organic foam model. Therefore, the method is not applied to cast steel in which unevenness of the structure, unevenness in hardness and the like pose problems. As such a cast steel, for example, a carbon steel cast steel product (J
IS G 5101), cast steel products for welded structures (JIS G
5102), structural high-tensile carbon steel and low alloy steel cast steel (JIS G 5111), stainless steel cast steel (J
IS G 5121), heat-resistant steel castings (JIS G 5
122), high manganese steel castings (JIS G513)
1), a cast steel product for high temperature and high pressure (JIS G5151), a cast steel product for low temperature and high pressure (JIS G5152), and the like.

Further, in the general vanishing model casting method, there are many occurrences of gas blow defects due to absorption of hydrogen, oxygen, and nitrogen components other than carbon, which are constituent elements of the foam model, into molten steel and discharge of gas during solidification.

In order to prevent and reduce the occurrence of carbon infiltration and the occurrence of gas blow defects, the ratio of the product volume to the surface area (the ratio of the gas generation amount to the gas discharge area) and the polymerization ratio of the foamed styrene / methacrylic ester of the model used Japanese Patent Application Laid-Open No. 10-76347, which discusses the relationship, has been disclosed, but has not been completely solved yet. These methods are basically intended to directly decompose and disappear the foam model by the heat of the molten metal.

In the conventional Replicast CS method, a ceramic foam having a thickness of 2 to 3 mm is fired at the same time as a foam model having strength is burned out, and the ceramic cell is refilled in molding sand or shot to form a mold. The thin and fragile shell having a thickness of 2 to 3 mm must be transported and embedded, and there is a risk of breakage. As can be seen from the above-mentioned literature, it is up to about 100 kg.

[0011] In order to solve the carbon absorption into the molten metal, the foam model may be burned and disappeared before casting, but air and oxygen are supplied from a gate, etc. at the stage before casting the lost model coated with a normal mold material. If it burns and disappears, the coating material layer for preventing the reaction between the molten metal and the mold aggregate and assuring the quality of the casting product is not fixed at all on the mold aggregate side, losing support Easily destroyed by thermal stress during combustion,
It falls and accumulates in the mold space.

Further, in the vanishing model casting method using non-binding agent molding sand, the mold space is destroyed and the product shape cannot be maintained. Even if a molten product is cast into a mold in such a state to obtain a cast product, a satisfactory product cannot be obtained.

[0013]

Means for Solving the Problems The inventors have conducted intensive studies in order to solve the above-mentioned conventional problems. As a result, if a fiber reinforced coating mold in which a fiber reinforcing material such as glass fiber is mixed with a commercially available vanishing model casting molding material is used, a strong mold material layer in a dry state is formed on the outer surface of the vanishing model. It is possible to heat the model coated with this fiber reinforced coating mold with a gas burner or the like, burn off the disappearance model,
After that, it was found that even if the temperature was lowered to room temperature by standing, even if heating and cooling were further repeated two or three times, the shape could be sufficiently maintained without being destroyed by thermal stress.

Further, when the model buried in the mold material is burned out, the oxygen supply port and the stirring air supply port are separately provided, and one of the oxygen is supplied from a weir communicating with the mold gate. Further, it has been found that the model can be completely burned to every corner of the model by supplying the stirring air from the other frying part into the mold.

Further, it has been found that, at the time of ignition, by igniting at the vent outlet on the downstream side, it is possible to ignite safely without causing an explosion phenomenon.

The present invention has been made based on the above findings. A first aspect of the present invention is a vanishing model casting method including the following steps. (A) a step of applying a coating mold premixed with a fiber reinforcing material to the disappearing model, drying and solidifying or self-hardening and then drying; and (b) embedding the dried model in a mold material to form a mold. (C) supplying oxygen and air for stirring to burn off the disappearance model in the mold, and burning off the disappearance model;
(D) a step of casting by casting molten metal into the space formed by the combustion;

According to a second aspect of the present invention, a supply port for oxygen and a supply port for air for stirring are separately provided, oxygen is supplied from a weir communicating with a mold gate, and air for stirring is supplied from the fry to the inside of the mold. The vanishing model casting method is characterized in that the vanishing model is ignited while burning the vanishing model while supplying the gas to be blown into the mold. A supply port for oxygen and a supply port for stirring air are separately provided, and oxygen is supplied from a weir communicating with the mold gate,
By supplying the stirring air so as to blow it into the mold from the fry portion, the model can be completely burned to every corner.

According to a third aspect of the present invention, in the supply of the stirring air, the oxygen-containing gas supplied into the space formed by the mold wall and the model combustion surface is sufficiently stirred in the space, A vanishing model casting method characterized in that generation of heat and supply of oxygen in the space are made uniform.

According to a fourth aspect of the present invention, there is further provided a vanishing model casting method characterized in that the stirring air is supplied so that exhaust gas generated by combustion in the space is promptly discharged from the space. It is.

According to a fifth aspect of the present invention, a vent is provided in the vanishing model, and oxygen or a mixed gas of oxygen and air is supplied from the vent, and a downstream area of the vanishing model near the vent outlet is provided. This is a vanishing model casting method characterized by igniting so as to stably burn a gas mixture of unburned gas and surrounding air.

In a sixth aspect of the present invention, a vent is provided in the vanishing model, and oxygen or a mixed gas of oxygen and air is supplied from the vent, and a flow of the mixed gas of oxygen or oxygen and air is provided. The present invention relates to a vanishing model casting method, wherein ignition is performed at a downstream vent outlet.

Another embodiment of the present invention is a vanishing model casting method including the following steps. (A) a step of applying a coating mold premixed with a fiber reinforcing material to the disappearing model, drying and solidifying or self-hardening and then drying; and (b) embedding the dried model in a mold material to form a mold. (C) burning the vanishing model in the mold; and (d) casting molten metal into the space formed by the burning and casting. In the present invention, since the fiber reinforcement is mixed into the mold, even if the vanishing model is burned before the molten metal is injected, the mold itself forms a strong shell. And a good casting can be cast.

In another aspect of the present invention, the fiber reinforcing material is one or a mixture of two or more of metal fibers, natural asbestos, glass fibers, silica fibers, carbon fibers, alumina fibers, and silicon carbide fibers. And a fiber reinforcing material having a length of 5 mm or more. Metal fibers, natural asbestos, glass fibers, silica fibers, carbon fibers, alumina fibers, and silicon carbide fibers give strength to dried coating materials when the model is burned, retain their shape, and can be damaged in subsequent casting. There is no. Further, after burning, the binder in the coating material for fixing the fibers is weak, and therefore, the longer the reinforcing fibers, the stronger the strength is obtained, but the reinforcing fibers may be at least 5 mm in casting and kneading operations. Desirably, usually 50 mm or less is appropriate.

Another embodiment of the present invention is a vanishing model casting method, wherein the vanishing model is a model made of a foamable resin. Since the foamable resin easily burns, it is suitable as a model.

Another aspect of the present invention is a vanishing model casting method, characterized in that the foamable resin is either polystyrene (EPS) or polymethacrylate (EPMMA) having improved decomposition ability. is there. Since the foamable resin is generally commercially available, it is suitable as a model material according to the present invention.

Another embodiment of the present invention is a vanishing model casting method, wherein the mold is a sand mold or a shot mold. The present invention is applicable to ordinary sand molds and shot molds.

Another aspect of the present invention is a vanishing model casting method, characterized in that the burning of the vanishing model is performed by igniting the model while supplying air and / or oxygen into the model. is there. In order to sufficiently burn the disappearing model so that no carbon content remains, it is desirable to supply air or oxygen by providing a pipe for auxiliary fuel in the model, particularly in a small and simple shape.

Another embodiment of the present invention is a vanishing model casting method, wherein the molten metal is cast iron or cast steel having a prescribed carbon content. The present invention can be applied to any of the molten metal cast using the disappearance model, but in view of not giving carbon to the molten metal, the amount of carbon is particularly suitable for cast iron and cast steel in which the amount of carbon is specified by standards and the like. Applicable to

According to another aspect of the present invention, a vent is provided in the model, oxygen or a mixed gas of oxygen and air is supplied from the vent, and the flow of the oxygen or the mixed gas of oxygen and air is downstream. Ignited at the outlet of the vent. By igniting at the downstream vent outlet, it is possible to safely ignite the model buried in the mold without causing an explosion phenomenon.

In particular, in the case of an extremely small and simple-shaped object, for example, the model may be directly heated and burned by a gas burner or the like from the feeder opening.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is basically a vanishing model casting method having the following steps. (A) a step of applying a coating mold premixed with a fiber reinforcing material to the disappearing model, drying and solidifying or self-hardening and then drying; and (b) embedding the dried model in a mold material to form a mold. (C) supplying oxygen and air for stirring to burn off the disappearance model in the mold, and burning off the disappearance model;
(D) a step of casting by casting molten metal into the space formed by the combustion; Furthermore, in a large-sized and complicated-shaped object, in the vanishing model casting method of the present invention, a supply port for oxygen and a supply port for air for stirring are separately provided, and oxygen is supplied from a weir communicating with a mold gate, The model is ignited while the stirring air is supplied so as to be blown into the mold from the fry portion, and the disappearing model is burned.

Further, in the vanishing model casting method according to the present invention, when the stirring air is supplied, the oxygen-containing gas supplied into the space formed by the mold wall and the model combustion surface is sufficiently stirred in the space. Thus, the generation of heat and the supply of oxygen in the space are made uniform. Further, in the vanishing model casting method of the present invention, the stirring air is supplied so that exhaust gas generated by combustion in the space is quickly discharged from the space.

Further, the efficient combustion of the model will be described in detail below. The following is a description of the combustion state of the model buried in the mold based on three factors: heat (combustion temperature), combustible matter, and oxygen combustion. Regarding the combustion temperature, which is the first condition, according to the study of the inventor, at the time when the foamable resin is burning in the mold, the highest temperature in the outermost coating part considered to be the lowest is about 1000.
℃, even at the lowest temperature is 550 ℃, inside the part,
It is estimated that the temperature is higher. Therefore, it can be confirmed that the temperature has sufficiently reached the temperature at which organic substances such as foamable resin can be burned.

The second condition, that is, the combustible material is sufficiently present, judging from the fact that the combustible foamable resin is being burned. Regarding the oxygen of the third condition, the combustible material burns as much as the supplied oxygen, so the burning time, that is, the supply time of oxygen is not limited, and the absolute value of oxygen is sufficiently present. As is clear from the above, from the viewpoint of the mold as a whole, the three elements of combustion are basically satisfied, and the model should be completely burned.

However, in practice, incomplete combustion may occur, leaving soot and tar-like condensate. That is,
For example, in the case of a large-sized product having a complicated shape, sufficient oxygen may not be obtained in portions where the gas flow of the oxygen-containing gas is difficult to reach, such as corners and recesses, and combustion may be deteriorated. . As a result, soot around the upper mold surface corner in the mold cavity formed after the disappearance of combustion, model soot and tar-like condensate around the lower mold surface corner, and tar over the entire lower mold surface Condensate may accumulate.

The first cause of the above-mentioned soot and tar-like condensate remains is that these phenomena are caused by gaseous oxygen and gaseous combustible in the space formed by the mold wall and the model combustion surface. It is considered that the distribution of the objects becomes uneven, and as a result, the distribution of heat in the space also becomes uneven, and the combustion becomes uneven. The second cause is considered to be that at the end of the combustion, the individual combustion parts are individually divided, and the heat is reduced, resulting in a tar-like state, and insufficient evaporation of heat and combustibles.

Therefore, first, it is important to make the distribution of oxygen and gaseous combustibles uniform and to generate heat uniformly in the space. Next, it is important to supply oxygen uniformly while supplying uniform heat to the model combustion surface having combustibles by the generated uniform heat. Furthermore, it is important that the exhaust gas generated by the combustion be quickly discharged out of the space without being partially retained. Therefore, while establishing the above situation,
By sequentially expanding and burning the model combustion surface from the ignition surface, soot and tar-like condensate can be prevented from remaining.

Secondly, at the end of the combustion, the evaporation of combustibles is also reduced due to the decrease in heat, and the combustion conditions are deteriorated.
It is necessary to satisfy this condition. That is, by gradually decreasing the amount of air and increasing the amount of oxygen, the heat loss from the combustion section by the stirring air is reduced, and by supplying a large amount of oxygen, the poorly burned parts such as corners and recesses are completely removed. Can be burned.

Specifically, an oxygen supply port and an air supply port are separately provided separately, oxygen is supplied from a weir section, and stirring air is supplied to the inside of the mold when the molten metal is poured into the mold. Air is supplied from a fry portion provided to quickly discharge air. By blowing a large amount of air with a high flow velocity mainly for agitation into the mold from the frying part in the opposite direction, heat in the space formed by the mold wall formed by combustion and the model combustion surface, combustible matter, Oxygen can be made uniform.

At the same time, the large amount of agitating air blown allows the waste generated by the combustion to be quickly discharged out of the mold, thereby increasing the concentration of oxygen existing in the space as a whole. As a result, the condensate falling like raindrops from the combustion surface on the upper mold surface side can also be completely burned.

The stirring air has a function of lowering the temperature of the exhaust gas in the mold due to the heat removal effect and also lowering the thermal stress applied to the fiber-reinforced coating wall exposed to the flame. The probability of peeling, falling, and deformation occurring is reduced.

At the end of the combustion, the model can be completely burned to every corner by gradually reducing the stirring air and filling the mold space with a high concentration of oxygen.
The interior of the mold after the burning has disappeared can be made in a sufficiently favorable state.

According to the combustion method of the present invention, in particular, even in the case of a large-sized and complicated-shaped product, there is no soot or condensate left in the corners and recesses after the combustion, and at the same time, the tar which drops and deposits on the lower mold surface. No condensate is present. As a result, a pure oxygen supply pipe that supplies oxygen in advance to promote combustion is also unnecessary, especially in parts where combustion is considered to be incomplete in small simple shapes, reducing the complexity of work. can do.

Further, in the vanishing model casting method according to the present invention, a vent is provided in the vanishing model, and oxygen or a mixed gas of oxygen and air is supplied from the vent, and the mixed gas of oxygen or oxygen and air is supplied. Regarding the flow of gas, it is ignited at the downstream vent outlet. This makes it possible to stably burn the unburned gas and the mixed gas with the surrounding air in the downstream area of the vanishing model near the vent outlet.

Further, an ignition method for burning a model will be described below. When ignited on the inlet side of the vent that introduces oxygen or a gaseous mixture of oxygen and air into the model, that is, on the upstream side with respect to the flow of the airflow, especially in the case of large molds, the gaseous mixture of oxygen or oxygen and air immediately after ignition Explosion occurred at the exit side opposite to the entrance side of
Loud noise, destruction or scattering of surrounding objects may occur. The above-described explosion phenomenon occurs because the combustion of the mixed gas portion of the unburned gas in the downstream range and the surrounding air is unstable.

Therefore, it is considered that the problem can be solved by stabilizing the combustion in the downstream range. For this reason, it is generally conceivable to attach an afterburner that provides stable combustion in the downstream range. However, this method does not provide a sufficient solution because the installation of the burner and the ignition timing thereof are complicated. .

FIG. 10 is a diagram for explaining the principle of the ignition method according to the present invention. FIG. 10A is a diagram showing a situation at the time of ignition. A vent 202 is provided in the center of the model 201, and oxygen or a mixed gas of oxygen and air 204 flows from one end. Thereafter, the ignition burner 217 ignites the outlet portion 216 of the vent, that is, the flow of the oxygen or the mixed gas 204 of oxygen and air, on the downstream side.

FIG. 10B is a diagram showing a situation immediately after the ignition. As shown in FIG. 10B, when the vent exit side is ignited, a flame 219 is generated in the downstream area 214 by heat of the ignition and combustion of the model combustibles and oxygen 213 in the air. And burns stably. This state is the same as the state where the afterburner is installed, and the combustion does not occur explosively and stably and safely. This stable combustion is continued until the entire combustion is almost completed and a part of "burning" combustion is left.

The flame generated by igniting the ignited portion immediately spreads in the ventilation hole to the upstream side, and the tip portion 218 on the upstream side spreads from the ignited portion by oxygen or oxygen by the mixed gas 204 of oxygen and air. Since the three elements of heat and combustion of combustibles around the vent are sufficiently satisfied, the fuel burns violently, immediately spreads the fire to the weir portion made of the ceramic tube 203, and stops there.

At this time, oxygen is deficient in the once-burned portion 220 of the middle flow range 210, and the combustion does not spread in the lateral direction of the ventilation hole, that is, in the wall direction. FIG. 10C is a diagram showing a situation in which the whole stable combustion state after ignition is entered. FIG.
As shown at C of 0, the flame spreads to the most upstream side of the upstream region 208, and the upstream region actively burns. At the same time, in the middle flow range 210, combustion becomes unstable due to lack of oxygen. Within about 1 to 2 minutes after the ignition, a small explosion 221 is generated in the small space of the vent, and a “pong” sound is generated. However, it is a small explosion in a small space inside the ventilation hole in the model, and there is no unsafe thing.

The center 2 of combustion centering on the upstream region 208
22 then moves sequentially to the downstream midstream area 210. At this point, less oxygen is consumed in the upstream area, and oxygen in the middle area is also sufficient to prevent an explosion. Even at this time, the flame 219 in the downstream range 214 continues to burn stably due to the stable supply of the oxygen 213 in the atmosphere, and continues to function as an afterburner. Through such a combustion process, the combustion is finally completed slightly downstream of the middle flow range. This is because the model surface 223 (combustible material) near the outlet at the most downstream side of the vent port gradually burns upstream due to oxygen in the atmosphere.

As described above, according to the ignition method of the present invention, it is possible to safely ignite a model buried in a mold.

Still another embodiment of the present invention is a vanishing model casting method including the following steps. (A) applying a coating mold premixed with a fiber reinforcing material to the disappearing model, drying and solidifying or self-hardening and then drying; and (b) embedding the dried model in a mold material to form a mold. (C) a step of burning the vanishing model in the mold; and (d) a step of injecting and casting a molten metal into a space formed by the burning. In the present invention, since a fibrous reinforcing material is mixed into the coating mold, a solid shell is formed even when the vanishing model is burned at a stage before the molten metal is injected, so that the mold is not broken, and a good casting is obtained. Can be cast.

Examples of the fiber reinforcing material include metal fibers, natural asbestos, glass fibers, silica fibers such as silica fiber of 95% by weight of silica, and silica fiber of 99.8% by weight of silica;
Carbon fiber, alumina fiber having a purity of 70 to 99.5 wt%,
Desirably, one or a mixture of two or more types of silicon carbide fibers is used, and the length is at least 5 mm or more and at most 50 mm or less. The length of the fibers used is basically determined by the adhesive strength of the binder in the coating material to the fibers and the aggregate, but the adhesive strength of the binder once heated is weak, and should be as long as possible. If it is less than 5 mm, the holding power of the coating mold is weak, and if it exceeds 50 mm, handling is inconvenient. As mentioned above, inorganic fibers are desirable. Organic fibers do not burn and remain when the model is burned, so that the strength of the layer of the coating material is reduced and the layer of the coating material is broken, which is not desirable.

As the coating, any commercially available coating material can be used, but Yamashiro Coat S-98F (trade name) or the like is preferable in view of the familiarity with the above fibers.

The vanishing model may be any material that can be easily burned, and may not be foamable. However, a model made of a foamable resin is suitable as a model because it burns easily. Examples of such a foamable resin include polystyrene (EPS) and polymethacrylate (EPMMA) having improved decomposition ability. Since the foamable resin is generally commercially available, it is suitable as a model material according to the present invention.

The mold may be any commonly used mold such as a sand mold or a shot mold.

In particular, in the case of a small, simple-shaped object, in order to completely burn the model, air or oxygen is supplied from the auxiliary combustion piping into the weir portion and a part of the inside of the model, for example, from the mold gate. While igniting by an ignition device provided on the model side. In order to sufficiently burn the disappearance model so that no carbon content remains, it is preferable to supply air or oxygen by providing a pipe for auxiliary fuel particularly in a portion where combustion is not good. In the case of extremely small and simple shapes, the model is directly heated by a gas burner etc. from the opening of the hot water, etc.
It may be burned.

The present invention can be applied to both ferrous and non-ferrous molten metals which are cast by using the disappearance model. Various prescribed cast iron and cast steel,
For example, it is preferably applied to cast iron and cast steel specified in standards such as JIS, ASTM, and DIN.

Specifically, a carbon steel casting (JIS G
5101), a cast steel product for a welded structure (JIS G 510)
2) Structural high tensile carbon steel and low alloy steel cast steel products (JI
SG5111), cast stainless steel (JIS G
5121), heat-resistant steel castings (JIS G 5122),
It is preferably applied to a high manganese steel casting (JIS G 5131), a high temperature and high pressure casting steel (JIS G 5151), a low temperature and high pressure casting steel (JIS G 5152), and the like.

Further, various cast irons (JIS G550) specified in the JIS Handbook (1998 edition)
1, 5502, 5503, 5504, 5510, 551
1, 5526, 5527, 5528, 5702, 570
3, 5704). The above is merely an example, and the present invention can be applied to all cast irons and cast steels having a prescribed carbon content.

As described above, according to the present invention, when a fiber reinforced coating mold is used in the vanishing model casting method, the layer of the fiber reinforced coating material in a dry state is strong, and the weight is the same as in a general vanishing model casting method. It can be transported and sanded without any size restrictions.

Further, even if the foam model on which the coating material layer is adhered is burned and disappeared in the mold before the injection of the molten steel, and the carbon component is removed, the coating material layer is removed at the time of burning and after that. Can sufficiently withstand the thermal stress during the cooling and the injection of the molten metal, so that a large mold space similar to that of the vanishing model casting method can be secured. Thus, the problem of carbon absorption, which is a disadvantage of the vanishing model casting method, can be solved at the same time.

That is, in a general vanishing model casting model having no weight limitation, a fiber-reinforced coating material is applied and dried, molded by a normal vanishing model casting method having no dimensional or handling restrictions, and molten steel is injected. When the foam model is burned and eliminated in the stage before the above, carbon, hydrogen, nitrogen, and oxygen contained in the foam model can be removed from the inside of the mold. In this way, a mold space surrounded by a shell of a dry and strong coating material layer is formed, and then, when molten metal is injected, unstable carbon, hydrogen, nitrogen,
Since no absorption of oxygen or the like occurs, a sound cast product can be obtained.

[0065]

The present invention will be described in more detail with reference to examples. Example 1 FIGS. 7 to 9 are diagrams illustrating a combustion method according to the present invention, particularly a large-sized and complicated-shaped model. FIG. 7 shows a state in which the model on which the fiber-reinforced coating mold is applied is formed in a mold, a piping state of oxygen and stirring air, a supply state of oxygen and stirring air, and ignition.

A styrofoam model (900
A width × 900 length × 400 thickness) 117 was prepared, and a vent 103 was provided in the model at a position where the weir 102 was to be installed. A fiber diameter of 14μm, 50
0 / yarn, sizing agent Adhesion rate 1.2wt% silicon carbide fiber cut to 6mm length (trade name: Nicalon Chop NCF-06) 98F) 1% by volume of fiber-reinforced coating mold 11
8 was prepared and applied. After the application, it was dried for about 8 hours to obtain a model for molding.

While the model is provided with a ceramic weir 102 having an inner diameter of 50 mm, a runner 101, and lifts 121 and 122 for supplying stirring air 119 and 120, the mold is buried in the casting sand 124 in the casting frame 123 to form a mold. did. At this time, the vent 103 and the stir fry 121 so that the stir air flows,
A drill hole 125 having a diameter of 10 mm was formed and connected to the ceramic tube portion 122. In this way, the mold was formed on the upper surface of the mold so that the upper surface of the runner 101, the lifts 121 and 122, the upper surface of the opener and the vent outlet 126 thereof were exposed, and a mold was prepared.

In addition, pipes 127 and 12 having an inner diameter of 10 mm
8, 129 were fitted, sealed with clay 130, 131, 132, and piped so that pure oxygen 133 and stirring air 119, 120 could be supplied. These pipes are connected to oxygen cylinders and industrial air pipes through valves 134, 135, 136 and a flow meter (not shown).

In the mold thus prepared, the runner 10
500 L / min of pure oxygen 123 and frying for stirring 1
Air for stirring 119 L / min through 21, 122;
While flowing, the ignition burner 137 from the vent outlet 126 on the feeder side, which is the outlet for these oxygen and air.
I ignited. Note that the combustion after ignition does not proceed sequentially from the ignited feeder side, but immediately reaches the weir portion 102, and starts burning with that portion as the first main combustion portion.

The direction of the pottery tubes of the fry 121 and 122 is set downward at 45 °, and a lot of stirring air 11
9 and 120 are applied because the casting posture of the casting is generally advantageous in terms of casting when a complicated surface is set on the lower mold surface of the mold cavity, so that the combustion state is not good on the lower mold surface side. Corner,
This is because a large number of recesses are generated, and the combustion conditions on the lower mold surface side are deteriorated.

The direction of jetting of the stirring air on the horizontal plane is arranged on the top so that the air flow as a whole rotates in the space formed by the mold wall and the combustion surface of the model. In this way, the combustion proceeds more smoothly by rotating the air flow as a whole.

FIG. 8 is a diagram showing the latter half of a situation in which active combustion is performed after ignition. As shown in FIG. 8, in a space 140 formed by the mold wall 138 and the model combustion surface 139, heat, combustibles, and oxygen are uniformly distributed by a stirring airflow in which stirring air and oxygen are mixed together in a turbulent flow 141. The combustion proceeds promptly due to the stirring. In such a combustion state, there is no drop of the condensate from the combustion surface 142 on the upper surface side of the model, and thus the condensate burns without depositing on the lower surface side of the mold cavity.

In the latter half of the combustion, the space 140 formed by the mold wall 138 and the combustion surface 139 of the model sequentially expands,
The oxygen-enriched stirring air 143 sufficiently mixed with pure oxygen supplied from the weir by the turbulent flow can move freely and reach every corner. Therefore, the oxygen spreads to every corner of the complex shape, and as a result, burns out to every corner.

At the final time point, stirring air was
Liters / minute, and the lid 14
Step 6 was carried out to increase the oxygen concentration in the mold and completely burn the individually separated and burning tar-like condensate.

FIG. 9 is a view showing the inside of the mold cavity held by the fiber-reinforced coating mold after burning. As shown in FIG. 9, the combustion is complete, resulting in a mold cavity 144 free of soot and falling and depositing tar-like condensate held by the fiber reinforced mold 118.

Embodiment 2 FIG. 11 is a diagram showing details of the ignition method of the present invention. As shown in FIG. 11A, a rectangular PMMA model 224 of 500 width × 1700 length × 250 thickness has a height of 50 mm to 80 mm from the lower part.
A 30 × 30 mm square vent 225 was opened in the mm portion, and a pusher 226 having an outer diameter of 200 mm × 200 mm and a vent having an inner diameter of 50 mm was opened at one end to make a model. Fiber reinforced coating 2 with 1% by volume of silicon carbide fiber mixed into this model
27 was applied to form a model for molding. One end of this model was provided with a weir 228 made of ceramic pipe having a diameter of 30 mm, and buried in casting sand 230 in a casting flask 229 to complete a mold before combustion. At this time, the thickness of the sand on the upper surface side of the mold was reduced to about 50 mm in order to observe the combustion state of the model in the mold using the fact that the mold sand was heated by the heat of combustion of the model to emit smoke.

In the above mold, the ceramic tube 23 connected to the weir 228
2 was passed through a pipe 233 having a diameter of 10 mm, and the area around the pipe 233 was sealed with a clay seal 234. Then, the fuel was ignited from a downstream hot water 226 by an ignition burner 217 while flowing oxygen 235 at about 100 L / min. The flame 219 after the ignition immediately went up in the square vent, and spread to the upstream weir 228. As described above, in order to spread the fire immediately to the porcelain weir without spreading in the lateral direction, that is, in the wall direction in the vent, in the middle flow range, the tip 218 on the upstream side of the inner surface of the burning vent is required. The three elements of combustion, heat, combustibles, and oxygen, are sufficiently filled, and the combustion is most active in that part. This is probably because oxygen is insufficient and combustion is suppressed. When the fire spreads to the most upstream part, the further part is the weir 228 made of a ceramic tube, and there is no combustible material, and the fire spread stops.

FIG. 11B is a view showing the situation after the fire has spread to the uppermost weir. When the fire spreads to the most upstream portion, it burns vigorously centering on the portion of the upstream range 208 to form a combustion center 222. This situation can be observed from outside the mold due to the generation of smoke 236. Immediately after that, the midstream area 2
Two to three small explosions 221 occur in 10 models. At this point, the portion that is open to the atmosphere at the most downstream portion is sufficiently supplied with the combustible material that is unburned gas, the heat generated by the combustion exhaust gas, the combustion heat of the portion, and the oxygen 213 in the atmosphere. Flames 219 are formed and burnt. At this time, the model surface 223 around the vent outlet portion burns inward (upstream side), but the speed is reduced by the combustion center 222 on the upstream side.
Is slower than the speed going downstream.

FIG. 11C is a diagram showing the situation at the end stage after the combustion of the uppermost stream has started. Looking at the movement of the combustion center as a whole, it moves sequentially from the upstream range where oxygen is most present to the downstream range. This is determined by observing the movement 237 of the smoke generating section to the downstream side. At the end of the combustion, the lower mold side, which is slightly downstream from the middle flow range, finally burns, and the entire combustion ends. In this situation, at this point, the amount of unburned gas is also reduced, and the momentum of the flame in the downstream range is also reduced. Observed by looking at the flame 239 of the final combustion section formed by

When a similar model is burned by ignition from the upstream side, a large amount of unburned gas, that is, combustible gas is generated,
A large explosion phenomenon may occur by mixing with oxygen in the air at the opening of the hot water which is the outlet of the vent on the most downstream side.

As described above, in the process of burning and disappearing the model while supplying oxygen or a mixed gas of oxygen and air to the model in the mold, oxygen or the mixed gas of oxygen and air to the downstream side, that is, the atmosphere. By igniting at the exit of the vehicle, it is possible to safely ignite without generating a large explosion phenomenon. Embodiment 3 Another embodiment of the present invention will be described with reference to an embodiment.
FIG. 1 to FIG. 6 are views showing an embodiment using a particularly small test piece for carbon absorption test. As a mold, a commercially available mold material composed of an inorganic or organic binder with 50 to 90% of aggregate fine particles under 60 μm was used. As the fibers, about 100 single fibers of glass having a fiber diameter of 13 μm and a fiber length of 13 mm are bundled and coated with an alkali-resistant, and the width is about 1 m
A band having a thickness of about 0.05 mm and a thickness of about 0.05 mm was used as a reinforcing material, and 10 g of this was added and mixed with 1 kg of the coating mold to obtain a coating material for this experiment.

As described above, the fibers having a certain degree of rigidity are well dispersed and kneaded during coating without causing entanglement during stirring. Model material is EPS and EPMM
Two types of A were used and each was compared.

FIG. 1 shows an embodiment in which a test piece for carbon absorption test is cast. This is an example of casting a carbon absorption test specimen in which a 326 mm square, 40 mm thick plate is attached to a 100 mm square, 710 mm long prism, in which a coating material is applied, an auxiliary combustion pipe, a vent, and an electric type. Fig. 3 shows an ignition device. The model material was used for two types of EPS and EPMMA.

The upper end of the prism has a diameter of 200 mm and a height of 200 m.
m is applied to the model 4 for the disappearing model with a ventilation hole 3 of about 25 mmφ opened from the lower end weir 2 to the upper surface of the feeder 1 with a brush.
For 8 hours to form a coating material layer 5. At this time, the coating material layer 5 had a thickness of 1 to 5 mm in a dry state. After drying, an electric ignition device 6 is attached to the lower end, and a drill hole 7 for auxiliary combustion is formed at one corner of each plate-like portion, and an auxiliary combustion pipe made of a steel pipe and a vinyl pipe of about 10 mmφ. 8 was attached.

It is not good to use a commercially available combustion type feeder sleeve in the feeder section to burn out while supplying air and oxygen because the feeder sleeve burns. As shown in the present embodiment, it is preferable that the riser part is also made of a foam model.

After the preparation of the model was completed, as shown in FIG. In this case, it is necessary that the gate 10 for supplying air and oxygen, the weir portion 2 and the vent 3 communicate with each other at a stage before ignition, and it is often difficult to partially fill the material for the sake of molding. Absent.

After molding, a pipe 11 for supplying oxygen and air and a tank 12 are connected to a sprue 10 and an auxiliary combustion pipe 8 leading to the weir section 2, and compressed air of 6.0 kgf / cm 2 and 150 kgf / cm 2, respectively. Oxygen from a compressed oxygen cylinder having a square centimeter was piped, and the electric ignition device 6 was energized while adjusting the flow rates of the airs 13 and 15 and the oxygens 14 and 16 to ignite the model 4 from the weir portion 2.

After the ignition, while watching the combustion state, use the time-adjusting valves 17, 18, 19, and 20 to adjust the air 13, 15.
The amount of oxygen and the amounts of oxygen 14 and 16 were adjusted, and model 4 was burned.
After that, it was confirmed that the flame and the smoke 21 disappeared and that the combustion and disappearance were completely completed. The burn-out time of the model is EP
It took about 17 minutes for the S model and about 10 minutes for the EPMMA model.

As shown in FIG. 3, a pipe 1 for air and oxygen
1, 17, 18, 13, 14 and 8, 12, 19, 20,
Remove 15 and 16 and add C = 0.22 wt% to the gate 10
The nozzle 24 of the ladle 23 filled with the molten steel 22 was aligned, the stopper 25 was opened, and the molten steel 22 was poured into the mold cavity 26 held by the coating material layer 5 and cast. In addition, the same model for comparison is a normal vanishing model casting method,
That is, the same molten steel was cast from the lower end 40 mmφ weir without burning before the molten metal injection. The same molten steel was cast using an EPS model and an EPMMA model of the same type, and also cast by a normal vanishing model casting method for comparison. A total of four casts, two made of EPS and two made of EPMMA, were cast.

FIG. 4 shows the positions where the samples were cut out from the respective positions (A to D, 1 to 4) of the test piece for carbon absorption test and the carbon content was measured. Table 1 shown in FIG. 5 shows the results by the EPS model, and Table 2 shown in FIG. 6 shows the results by the EPMMA model.

The results of the carbon analysis of the EPS model shown in Table 1 are as follows. In the conventional method, the central parts A, B,
The carbon analysis values of C, D, and ends 1, 2, 3, and 4 increase toward the top, especially at end 1, which is 0.42 wt%, which is 0.20 wt% higher than the original component. When attention is paid to the variac, the central part is 0.03 wt% and the end part is 0.17 wt%.
wt%.

[0092] Such dispersion of carbon components makes it difficult to produce cast steel products by the conventional vanishing model casting method.
On the other hand, in the value according to the present invention, no change in the carbon component due to a clear vertical position as in the conventional method is observed. Paying attention to the variation, the center portion is 0.01 wt% and the end portion is 0.01 wt%, and there is only a measurement error.

The results of carbon analysis of the EPMMA model shown in Table 2 are as follows. According to the conventional method, the carbon analysis value increases toward the upper portion of the test pieces at the center portions A, B, C, and D and at the end portions 1, 2, 3, and 4, and the variation of the carbon analysis value is 0.
It is 04 wt% and the end portion is 0.02 wt%. It is also recognized that infiltration of carbon into molten steel has occurred in the EPMMA model with further improved decomposition performance. The value according to the invention is
As in the case of the EPS model, no change in the carbon component depending on the vertical position is observed. If you pay attention to Baracki, the center is 0.
It is 0.01 wt% and the end portion is 0.00 wt%, and there is only a measurement error similar to the result of the EPS.

As described above, since the vanishing model is burned and removed before the injection of the molten metal, the vanishing model casting method according to the present invention has the biggest drawback of the prior art, regardless of the material of the vanishing model. Can solve the problem of absorption of minutes. In the case of the casting weight of about 250 kg shown in the present embodiment, it is sufficient that the fiber mixed into the coating material has heat resistance of about glass fiber.

[0095]

The effects of the present invention are as follows. (1) Overall carbon absorption and local uneven distribution of cast iron and cast steel products by the conventional vanishing model casting method can be eliminated. (2) Since a large cast product as many as several tons can be cast, the size limitation of the cast product is eliminated. (3) Cast iron and cast steel products with specified carbon content can be manufactured by the vanishing model casting method. (4) High-grade castings including low carbon stainless steel castings can also be cast by the vanishing model casting method. (5) It is possible to manufacture a precision cast product similar to the Replicast CS method without any dimensional restrictions on the cast product. (6) Infiltration of hydrogen contained in the organic foam model into the molten metal can be prevented. (7) The problem of gas blow of a cast product caused by absorption of oxygen gas, carbon dioxide gas and nitrogen gas, which is a drawback of the conventional vanishing model method, can be solved. (8) If the model material is basically one that burns out,
The presence or absence of foaming or the type of material is not limited. Further, the following effects can be obtained. (9) When the model buried in the mold is burned, the model can be sufficiently burned and eliminated up to the corners and the concave portions. (10) It is possible to prevent the accumulation of the condensate of the tar-like model on the lower surface side of the mold cavity. (11) Molding can be easily performed without installing an oxygen supply pipe that partially supplies oxygen for promoting combustion in a portion where combustion is concerned in advance. Further, the following effects can be obtained. (12) When burning a model buried in a mold,
Safe ignition without explosion.

[Brief description of the drawings]

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a view showing a coating state of a coating mold in casting of a test piece for a carbon absorption test, an arrangement of an auxiliary combustion pipe, a vent, and an electric ignition device.

FIG. 2 is a view showing a situation in which a test piece for carbon absorption test is molded in molding sand, and a model is burnt and disappeared at a stage before casting.

FIG. 3 is a view showing a casting state after combustion disappearance.

FIG. 4 is a diagram showing an analysis position of a carbon component in a cast carbon absorption test specimen.

FIG. 5 is a diagram showing, as Table 1, carbon distribution of a casting in casting using a model made of EPS.

FIG. 6 is a diagram showing, as Table 2, carbon distribution in a casting in casting using a model made of EPMMA.

FIG. 7 is a diagram illustrating a combustion method according to the present invention.

FIG. 8 is a diagram illustrating a slightly latter half of a situation in which active combustion is performed after ignition.

FIG. 9 is a view showing the inside of a mold cavity held by a fiber-reinforced coating mold after burning.

FIG. 10 is a diagram illustrating the principle of the ignition method according to the present invention.

FIG. 11 is a diagram showing details of the ignition method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Feeder 2 Weir part 3 Vent 4 Disappearance model 5 Coating material layer 6 Electric ignition device 7 Drill hole for auxiliary combustion 8 Piping for auxiliary combustion 9 Mold sand 10 Gate 11 Pipe 12 Tank 13,15 Air 14,16 Oxygen 17 , 18, 19, 20 Adjustment valve 21 Flame and smoke 22 Molten steel 23 Ladle 24 Nozzle part 25 Stopper 26 Mold cavity

Claims (6)

[Claims] 1. A vanishing model casting method comprising the following steps. (A) a step of applying a coating mold premixed with a fiber reinforcing material to the disappearing model, drying and solidifying or self-hardening and then drying; and (b) embedding the dried model in a mold material to form a mold. (C) supplying oxygen and air for stirring to burn off the disappearance model in the mold, and burning off the disappearance model;
(D) a step of casting by casting molten metal into the space formed by the combustion; 2. An oxygen supply port and a stirring air supply port are separately provided. Oxygen is supplied from a weir section communicating with a mold gate, and stirring air is supplied from a fry section to be blown into the mold. The vanishing model casting method according to claim 1, wherein the vanishing model is ignited to burn the vanishing model. 3. When the stirring air is supplied, the oxygen-containing gas supplied into the space formed by the mold wall and the model combustion surface is sufficiently stirred in the space to generate heat in the space. The method according to claim 1, wherein generation and supply of oxygen are made uniform. 4. The vanishing model casting according to claim 3, wherein the stirring air is supplied so that exhaust gas generated by combustion in the space is quickly discharged from the space. Law. 5. An air vent is provided in said vanishing model, and oxygen or a mixed gas of oxygen and air is supplied from said vent, and unburned gas and its surroundings in the downstream area of said vanishing model near said vent outlet are provided. The vanishing model casting method according to any one of claims 1 to 4, wherein the mixture is ignited so as to stably burn a mixed gas with air. 6. A ventilation port is provided in the vanishing model, and oxygen or a mixed gas of oxygen and air is supplied from the ventilation port, and ventilation of the oxygen or the mixed gas of oxygen and air is performed on a downstream side. The vanishing model casting method according to any one of claims 1 to 4, wherein ignition is performed at a mouth exit.