JP3426159B2 - Vanishing model casting - Google Patents

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 vanishing model which burns and disappears into a casting during casting in a vanishing model casting method which is a method for casting molten metal, and more particularly, The present invention relates to a casting method for reducing carbon absorption in a casting by efficient combustion.

[0002]

2. Description of the Related Art In the disappearance model casting method, a model having a desired shape is manufactured by using expanded polystyrene (EPS), which is a foam of an organic substance, or expanded polymethacrylic acid ester (EPMMA) having an improved decomposition ability. Embed the foam model in molding sand (self-hardening sand) that contains a binder such as water glass or furan resin, or molding sand that does not contain a binder or shot (fine iron particles) (hereinafter referred to as mold material) A casting method in which molten steel is poured as it is without removing the model, and the heat decomposes and replaces the model to obtain a cast product of the desired shape.

The vanishing model casting method is an extremely highly efficient casting method because it does not require a core for forming a cavity of a cast product and does not require assembly thereof. Since this casting method can cast products of several gr to several Ton, it has an advantage that there is no limitation in weight and size of the cast product.

On the other hand, the reprecast CS method (for example, J
ACT NEWS No. 332, 4th edition mold making method)
In place of the precision casting wax model, the precision casting mud (slurry) is applied over the foam model for vanishing model casting, and solidified and dried. Next, the entire model coated with the slurry is put into a firing furnace at about 1000 ° C., and at the same time as the slurry is burned, the foam model is burned out and extinguished to produce a thin ceramic shell with a hollow interior. The sand fork is a casting method in which the sand is embedded in a shot to form a mold and then cast.

The characteristic of this replicast CS method is that the foam model is burnt and lost before the casting,
This is because it is possible to prevent the carbon content from entering the product due to the decomposition of the foam model. This replicast CS method is also capable of casting low-carbon stainless steel, whose carbon content is strictly limited, without any problem. However, this method is basically a precision casting method, and although precise small pieces can be cast, it cannot be applied to relatively large castings because of the strength of thin ceramic cells.

[0006]

Although the general disappearance model casting method has an advantage that there is no limitation in weight and size,
Injecting molten metal, for example, the foam model directly by the heat of the molten steel, causes the decomposition of the foam model to be burned out. Absorption is inevitable.

Therefore, in the completed cast product, an unstable carbon content rise of 0.05 to 0.45 wt% with respect to the original molten steel occurs. Therefore, the molten steel originally contains a large amount of carbon, and is often used in cast iron (generally C = 2.5 to 3.5 wt%) in which the infiltration of carbon components due to the decomposition of the foam model does not pose a problem. However, the carbon content of the molten steel is small, and the carbon content increases due to the decomposition of the organic foam model. Therefore, it is not applicable to cast steel where problems such as non-uniform structure and hardness variation occur. Examples of such cast steel include carbon steel cast steel products (J
IS G 5101), cast steel products for welding 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 cast steel products (JIS G 5
122), high-manganese steel cast steel products (JIS G513
1), high temperature and high pressure cast steel products (JIS G 5151), low temperature and high pressure cast steel products (JIS G 5152) and the like.

Further, in the general vanishing model casting method, gas blow defects often occur due to absorption of hydrogen, oxygen, and nitrogen components other than carbon, which is a constituent element of the foam model, into molten steel and gas discharge during solidification.

In order to prevent and reduce the occurrence of carbon infiltration and 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 acid ester of the model used. A study such as Japanese Patent Laid-Open No. 10-76347, which discusses the relationship with the above, is disclosed, but it has not been completely solved yet. This is because these methods are basically trying to decompose and disappear the foam model directly by the heat of the molten metal.

In the conventional Replicast CS method, since a foam model having strength is burnt and disappeared, a ceramic cell having a thickness of 2 to 3 mm is fired at the same time to form a buried mold in a molding sand or shot, The thin brittleness of 2 to 3 mm must be transported and embedded in the shell, and there is a risk of breakage, and the size must be such that it can enter the firing furnace, and large objects cannot be cast. As can be seen in the above-mentioned literature, it is up to about 100 kg.

In order to solve the carbon absorption in the molten metal, the foam model may be burnt and extinguished before casting, but the vanishing model coated with a normal coating material is supplied with air and oxygen from the gate or the like before casting. However, if it is burnt out, the coating material layer for preventing the reaction between the molten metal and the mold aggregate and guaranteeing the quality of the casting product is not fixed at all on the mold aggregate side, so it loses its support. Easily destroyed by thermal stress during combustion,
It falls and accumulates in the mold space.

Further, in the vanishing model casting method using the non-binding agent molding sand, the mold space is destroyed and the product shape cannot be maintained. Even if a molten metal 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 present inventors have conducted extensive studies in order to solve the above-mentioned conventional problems. As a result, by using a fiber-reinforced coating mold in which a fiber-reinforced material such as glass fiber is mixed with a commercially available die-casting model casting material, a strong coating material layer is formed in a dry state 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 etc. to burn off the disappeared model,
After that, it was found that even if it was left to stand and the temperature was lowered to room temperature, and even if heating and cooling were repeated two to three times, the shape could be sufficiently maintained without being destroyed by thermal stress.

Further, when the model buried in the mold material is burnt out, an oxygen supply port and an agitation air supply port are separately provided, and one oxygen is supplied from a weir communicating with the mold gate. However, by further supplying the stirring air from the other frying part so as to blow it into the mold, it was found that it is possible to completely combust every corner of the model.

Further, it has been found that, at the time of ignition, the ignition can be safely performed without causing an explosion phenomenon by igniting at the outlet of the ventilation port on the downstream side.

The present invention was made based on the above findings. A first aspect of the invention is a vanishing model casting method including the following steps. (A) A step of applying a coating mold in which a fiber reinforcing material is mixed in advance to a disappearing model, and drying and solidifying or self-hardening and then drying, and (b) embedding the dried model in a mold material to prepare a mold. A step of: (c) supplying oxygen and agitation air to burn the vanishing model in the mold to burn the vanishing model;
(D) A step of injecting molten metal into the space formed by the combustion and casting.

In a second aspect of the invention, an oxygen supply port and an agitation air supply port are separately provided, and oxygen is supplied from a weir part communicating from the mold gate, and stirring air is supplied from the frying part into the mold. The extinguished model casting method is characterized in that the extinguished model is burned by igniting the model while supplying the extinguished model. An oxygen supply port and a stirring air supply port are provided separately, and oxygen is supplied from the weir part communicating from the mold gate,
By supplying the agitating air so that it is blown into the mold from the frying part, it is possible to completely burn every corner of the model.

In a third aspect of the 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, The vanishing model casting method is characterized in that the heat generation and the oxygen supply in the space are made uniform.

A fourth aspect of the present invention further includes the vanishing model casting method characterized in that the stirring air is supplied so that the exhaust gas generated by combustion in the space is promptly discharged from the space. Is.

In a fifth aspect of the 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 in a downstream range of the vanishing model near the vent outlet. It is a vanishing model casting method characterized by igniting so as to stably burn a gas mixture of unburned gas and air around it.

In a sixth aspect of the 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 flow of the oxygen or the mixed gas of oxygen and air is performed. With regard to the above, the vanishing model casting method is characterized by igniting at the outlet of the vent on the downstream side.

Another aspect of the present invention is a vanishing model casting method including the following steps. (A) A step of applying a coating mold in which a fiber reinforcing material is mixed in advance to a disappearing model, and drying and solidifying or self-hardening and then drying, and (b) embedding the dried model in a mold material to prepare a mold. A step, (c) a step of burning the vanishing model in the mold, and (d) a step of injecting and casting molten metal into the space formed by the burning. In the present invention, since the fiber reinforcement is mixed in the coating mold, even if the vanishing model is burned before the molten metal is injected, the coating mold itself forms a strong shell and is not damaged. Therefore, 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 kinds of metal fibers, natural asbestos, glass fibers, silica fibers, carbon fibers, alumina fibers and silicon carbide fibers. The vanishing model casting method is characterized in that the fiber reinforcing material has 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 the dried mold material when the model is burned, retain its shape, and are also damaged during subsequent casting. There is no. In addition, after burning, the binder in the mold fixing material for fixing the fibers is weakened. Therefore, the longer the reinforcing fiber is, the stronger the strength can be obtained, but it is 5 mm or more in casting work and kneading work. It is desirable and usually 50 mm or less is suitable.

Another aspect of the present invention is a vanishing model casting method, wherein the vanishing model is a model made of a foaming resin. The foamable resin burns easily and is suitable as a model.

Another aspect of the present invention is a disappearance model casting method, wherein the foamable resin is either polystyrene (EPS) or polymethacrylic acid ester (EPMMA) with improved decomposition ability. is there. Since the foamable resin is usually commercially available, it is suitable as the model material according to the present invention.

Another aspect of the present invention is a vanishing model casting method, wherein the mold is a sand mold or a shot mold. The present invention can be applied to ordinary sand mold materials and shot molds.

Another aspect of the present invention is a vanishing model casting method, wherein the vanishing model is burned by igniting the model while supplying air and / or oxygen into the model. is there. In order to burn the vanishing model sufficiently so that carbon content does not remain, it is preferable to provide a pipe for auxiliary fuel in the model to supply air or oxygen, especially for a small and simple shape.

Another aspect of the present invention is the vanishing model casting method, wherein the molten metal is cast iron or cast steel having a specified carbon content. INDUSTRIAL APPLICABILITY The present invention can be applied to any of the molten metals cast using the vanishing model, but is particularly suitable for cast iron and cast steel in which the amount of carbon is specified by standards etc. from the viewpoint of not giving carbon to the molten metal. Applicable to

According to another aspect of the present invention, a vent is provided in the model, and oxygen or a mixed gas of oxygen and air is supplied from the vent, and a downstream side of the flow of oxygen or a mixed gas of oxygen and air is provided. It is a vanishing model casting method characterized by igniting at the outlet of the air vent. By igniting at the outlet of the vent on the downstream side, when the model embedded in the mold is burned, it is possible to safely ignite without causing an explosion phenomenon.

Particularly, in the case of an extremely small and simple shape, the model may be directly heated and burned by a gas burner or the like from the opening of the feeder.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is basically a vanishing model casting method including the following steps. (A) A step of applying a coating mold in which a fiber reinforcing material is mixed in advance to a disappearing model, and drying and solidifying or self-hardening and then drying, and (b) embedding the dried model in a mold material to prepare a mold. A step of: (c) supplying oxygen and agitation air to burn the vanishing model in the mold to burn the vanishing model;
(D) A step of injecting molten metal into the space formed by the combustion and casting. Further, in the case of a large and complicated shape, in the vanishing model casting method of the present invention, an oxygen supply port and a stirring air supply port are separately provided, and oxygen is supplied from a weir part communicating with the mold gate. The model is ignited while the stirring air is supplied so as to be blown into the mold from the frying unit to burn the vanishing model.

Further, in the vanishing model casting method of 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. Then, 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 further supplied so that the 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. Considering the combustion state of the model embedded in the mold in consideration of the three factors of heat (combustion temperature), combustibles and oxygen, it is as follows. Regarding the combustion temperature which is the first condition, according to the research by the inventor, at the time when the foamable resin is burning in the mold, the maximum temperature in the outermost coating mold part which is considered to be the lowest is about 1000.
℃, the lowest temperature is 550 ℃, in the inner part,
It is estimated that the temperature is even higher. Therefore, it can be confirmed that the temperature has reached a temperature at which the organic matter such as the foamable resin can be burned sufficiently.

The combustible substance, which is the second condition, is sufficiently present, judging from the fact that the foamable resin which is the combustible substance is burned. With respect to the oxygen of the third condition, since the model that is a combustible material burns as much as oxygen is supplied, there is no limitation on the combustion time, that is, the oxygen supply time, and the absolute value of oxygen is sufficient. As is clear from the above, when viewed as a mold as a whole, basically the three elements of combustion are satisfied, and complete combustion of the model should be performed.

However, in reality, incomplete combustion may occur, leaving soot and tar-like condensate. That is,
For example, in the case of a large product having a complicated shape, sufficient oxygen may not be obtained and combustion may be deteriorated in a portion such as a corner or a recess where it is difficult for the air flow of the oxygen-containing gas to reach. . As a result, soot around the upper mold surface corners in the mold cavity formed after the combustion disappeared, model soot and tar-like condensate around the lower mold surface corners, and tar on the entire lower mold surface. -Like condensate may accumulate.

The first cause of the soot and tar-like condensate remaining is that these phenomena are due to gaseous oxygen and gaseous combustible in the space formed by the mold wall and the model combustion surface. It is considered that this is because the distribution of the material becomes non-uniform, and as a result, the distribution of heat in the space also becomes non-uniform and the combustion becomes non-uniform. The second reason is considered to be that, at the final point of combustion, the individual combustion parts are individually divided, and the heat decreases, resulting in tar-like formation, and the evaporation of heat and combustibles is insufficient.

Therefore, first of all, it is important to make the distribution of oxygen and gaseous combustibles uniform and to evenly generate heat in the space. Next, it is important to supply oxygen uniformly while simultaneously supplying uniform heat to the model combustion surface with combustibles by the uniform heat thus generated. Further, it is important to quickly discharge the exhaust gas generated by combustion outside the space without partially retaining it. Therefore, while satisfying 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 final point of combustion, due to the decrease in heat, the evaporation of combustibles is also decreased and the combustion conditions are deteriorated. Therefore, it is necessary to increase the amount of oxygen.
It is necessary to satisfy this condition. That is, by gradually reducing the air amount and increasing the oxygen amount, the heat removal from the combustion part by the agitation air is reduced, and by supplying a large amount of oxygen, the corners, recesses, and other bad combustion conditions can be completely removed. Can be burned to.

Specifically, the oxygen supply port and the air supply port are separately provided, oxygen is supplied from the weir portion, and the agitation air is used in the mold when the molten metal is poured into the mold. Supplied from a frying unit provided to expel air quickly. A large amount of high-velocity air with a main purpose of stirring is blown into the mold in the opposite direction from the frying part, so that the heat in the space formed by the mold wall and the model combustion surface formed by combustion, combustibles, Oxygen can be made uniform.

At the same time, the large amount of agitation air blown in allows the exhaust gas generated by the combustion to be quickly discharged to the outside of the mold to raise the concentration of oxygen existing in the space as a whole. As a result, the condensate that drops like raindrops from the combustion surface on the upper mold surface side can also be completely combusted.

The agitating air has a function of lowering the exhaust gas temperature in the mold due to its heat absorbing effect and a function of lowering the thermal stress applied to the fiber-reinforced coating wall exposed to the flame. The probability of peeling, dropping, or deformation is reduced.

At the final stage of combustion, by gradually reducing the agitation air and filling the space inside the mold with a high concentration of oxygen, it is possible to completely combust every corner of the model,
It is possible to make the inside of the mold sufficiently good after the combustion disappears.

According to the combustion method of the present invention, even in the case of a large-sized complex shape, soot and condensate do not remain in the corners and recesses after combustion, and at the same time the tar is dropped and deposited on the lower mold surface. The condensate is also lost. As a result, especially in small and simple shaped objects, it is not necessary to use pure oxygen supply piping that supplies oxygen in advance to promote combustion, especially in areas where combustion is considered to be incomplete, and work complexity is reduced. can do.

Further, in the vanishing model casting method 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 to mix the oxygen or the oxygen and air. With respect to the flow of gas, it ignites at the vent outlet on the downstream side. As a result, it is possible to stably burn the mixed gas of the unburned gas and the air around it in the downstream region of the vanishing model near the vent outlet.

The ignition method for burning the model will be described below. When igniting on the inlet side of the vent for introducing oxygen or a mixed gas of oxygen and air into the model, that is, on the upstream side with respect to the flow of the air flow, especially in the case of a large mold, oxygen or a mixed gas of oxygen and air immediately after ignition. Explosion phenomenon occurs at the outlet side part opposite to the inlet side of
May generate loud noise, destroy surrounding objects, or scatter. The above-described explosion phenomenon occurs because the combustion of the mixed gas portion of the unburned gas in the downstream range and the air around it is unstable.

Therefore, it is considered that the problem can be solved by stabilizing the combustion in the downstream region. For this reason, it is generally considered to install an afterburner that provides stable combustion in the downstream range, but this method is not a sufficient solution because the burner installation and its ignition timing are complicated. .

FIG. 10 is a diagram for explaining the principle of the ignition method of the present invention. 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 204 of oxygen and air is made to flow from one end. After that, with respect to the outlet portion 216 of the vent, that is, with respect to the flow of oxygen or the mixed gas 204 of oxygen and air, the ignition burner 217 ignites on the downstream side.

FIG. 10B is a diagram showing the situation immediately after ignition. As shown in FIG. 10B, when ignition is performed on the vent outlet side, in the downstream range 214, three elements, heat of ignition, combustion of combustible material of model and oxygen 213 in the air, are constituted to generate flame 219. And burns stably. This state is similar to the state where an afterburner is installed, and an explosion phenomenon does not occur, and stable and safe combustion is performed. This stable combustion continues until the entire combustion is almost completed and a part of the "fire" is left.

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

At this time, oxygen is insufficient in the once-burned portion 220 of the middle-flow range 210, and the combustion does not spread in the lateral direction of the vent, that is, in the wall surface direction. FIG. 10C is a diagram showing a situation in which the overall stable combustion state after ignition is entered. Figure 1
As indicated by C of 0, the flame spreads to the most upstream side of the upstream range 208, and the upstream range actively burns. At the same time, in the midstream range 210, combustion becomes unstable due to lack of oxygen. Within about 1 to 2 minutes after ignition, a small explosion 221 is generated in the small space of the ventilation port, and a "pompon" sound is generated. However, there is nothing unsafe because it is a small explosion in a small space inside the vent in the model.

Combustion center 2 centered on the upstream region 208
22 then moves to the midstream range 210 on the downstream side. At this point, less oxygen is consumed in the upstream range, sufficient oxygen is available in the midstream range, and no explosion occurs. Even at this point in time, the flame 219 in the downstream range 214 continues to burn stably due to the stable supply of oxygen 213 in the atmosphere, and continues to function as an afterburner. Through such a combustion process, combustion is finally completed in the slightly downstream side of the midstream range. This is because the model surface 223 (combustible material) around the vent port outlet on the most downstream side is oxygen in the atmosphere, and thus gradually burns to the upstream side.

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

Further, another aspect of the present invention is a vanishing model casting method including the following steps. (A) a step of applying a coating mold in which a fiber reinforcing material is mixed in advance to a disappearing model, and drying and solidifying or self-hardening and then drying; and (b) a step of embedding the dried model in a mold material to form a mold And (c) burning the vanishing model in the mold, and (d) injecting molten metal into the space formed by the burning and casting. In the present invention, since the fiber reinforcement is mixed in the mold, it does not break because it forms a strong shell even if the fugitive model is burned at the stage before injecting the molten metal, and thus a good casting Can be cast.

As the above-mentioned fiber reinforcing material, metal fibers, natural asbestos, glass fibers, silica fibers such as silica 95% by weight, silica fibers such as silica 99.8% by weight quartz fibers,
Carbon fiber, alumina fiber having a purity of 70 to 99.5 wt%,
A mixed fiber of one or more kinds of silicon carbide fibers is desirable, and its length is at least 5 mm or more, and preferably within 50 mm at maximum. The length of the fiber used is basically determined by the adhesive force of the binder in the mold coating material to the fiber and the aggregate, but the adhesive force of the binder once heated is weak, and if it is as long as possible. If it is less than 5 mm, the holding force of the coating mold is weak, and if it exceeds 50 mm, handling is inconvenient. As mentioned above, inorganic fibers are desirable. Since the organic fibers are not burned and remain when the model is burned, the strength of the layer of the mold coating material is lowered and the layer of the mold coating material is destroyed, which is not desirable.

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

The extinguishing model need only be a material that burns easily and does not have to be foamable, but a model made of a foaming resin is suitable as a model because it burns easily. Examples of such a foamable resin include polystyrene (EPS), polymethacrylic acid ester (EPMMA) having improved decomposition ability, and the like. Since the foamable resin is usually commercially available, it is suitable as the model material according to the present invention.

The mold may be a sand mold, a shot mold or any other commonly used mold.

In particular, in the case of a small-sized and simple-shaped object, in order to completely burn the model, air or oxygen is supplied from the auxiliary combustion piping to the weir part and a part of the inside which communicate with the mold gate, for example. While supplying, the ignition device provided on the model side ignites. In order to burn the vanishing model sufficiently so that carbon content does not remain, it is desirable to provide a pipe for auxiliary fuel to the part where the combustion condition is not good to supply air or oxygen. In the case of an extremely small and simple shape, the model is directly heated with a gas burner etc. from the opening of the riser etc.
It may be burned.

The present invention can be applied to both ferrous and non-ferrous molten metals that are cast using the vanishing model. However, from the viewpoint that carbon is not given to the molten metals, at least the carbon amount range is more than the standard. Various prescribed cast iron and cast steel,
For example, it is preferably applied to cast iron and cast steel defined by JIS, ASTM, DIN and other standards.

Specifically, carbon steel cast steel products (JIS G
5101), cast steel products for welding structure (JIS G 510
2), structural high-strength carbon steel and low alloy steel cast steel products (JI
S G5111), cast stainless steel products (JIS G
5121), heat-resistant cast steel products (JIS G 5122),
It is preferably applied to high manganese cast steel products (JIS G 5131), high temperature and high pressure cast steel products (JIS G 5151), low temperature and high pressure cast steel products (JIS G 5152), and the like.

Further, various cast irons (JIS G 550) specified in JIS Handbook (1998 version)
1, 5502, 5503, 5504, 5510, 551
1, 5526, 5527, 5528, 5702, 570
3, 5704). The above is merely an example, and can be applied to all cast irons and cast steels for which the carbon content is regulated.

As described above, according to the present invention, when the 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 the general vanishing model casting method. It can be transported and sand-filled without any size restrictions.

Furthermore, even if the foam model to which the mold coating layer has adhered in the mold before the injection of the molten steel is burnt out and the carbon component is removed, the mold coating layer remains at the time of burning burnout and thereafter. Since it can sufficiently withstand the thermal stress at the time of cooling and the injection of the molten metal, a large mold space similar to that of the disappearance model casting method can be secured. Therefore, the problem of carbon absorption, which is a drawback of the disappearance model casting method, can be solved at the same time.

That is, in a general model for vanishing model casting without weight limitation, a fiber-reinforced coating material is applied and dried, and the model is cast by an ordinary vanishing model casting method free from dimensional restrictions and handling restrictions, and molten steel is injected. If the foam model is burnt out in the previous step, the 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 the shell of the dry and strong mold coating material layer is formed, and then when molten metal is injected, unstable carbon, hydrogen, and nitrogen from the foam model, which is an organic substance, are generated.
Since absorption of oxygen and the like does not occur, a sound cast product can be obtained.

[0065]

EXAMPLES The present invention will be described in more detail by way of examples. Example 1 FIGS. 7 to 9 are views for explaining a combustion method according to the present invention, particularly a combustion method in a large model having a complicated shape. FIG. 7 shows a state in which a model coated with the fiber-reinforced coating mold is molded in the mold, a piping state of oxygen and stirring air, a supply state of oxygen and stirring air, and ignition.

Styrofoam model (900
(Width × 900 length × 400 thickness) 117 was prepared, and a vent hole 103 was provided in the model in accordance with the position where the weir 102 is to be installed thereafter. Fiber diameter 14μm, 50 in this model
0 pieces / yarn, sizing agent Adhesion rate 1.2 wt% Silicon carbide fiber cut to a length of 6 mm (trade name: Nicalon Chop NCF-06) disappeared Model coating agent (trade name: S- 98F) with 1% by volume mixed with fiber reinforced coating 11
8 was prepared and applied. After coating, it was dried for about 8 hours to prepare a model for molding.

While the model is provided with a weir 102 having an inner diameter of 50 mm, a runner 101, and hoisting members 121 and 122 for supplying agitation air 119 and 120, an embedded mold is formed in a molding sand 124 in a molding flask 123. did. At this time, the ventilation hole 103 and the stirrer 121 so that the stirrer air flows,
A drill hole 125 having a diameter of 10 mm was formed between the 122 and the ceramic pipe to connect them. In this way, a mold was prepared by molding so that the runner 101, the frying 121, 122 and the upper surface of the open riser and its vent port outlet 126 were exposed on the upper surface of the mold.

In addition to this, pipes 127, 12 having an inner diameter of 10 mm
8 and 129 were fitted and sealed with clay 130, 131 and 132, and piping was provided so that pure oxygen 133 and stirring air 119 and 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
1 through 500L / min of pure oxygen 123 and stirring frying 1
Air 119 for stirring of 900 L / min through 21, 122,
While flowing 120, the burner 137 for ignition is supplied from the vent opening 126 on the riser side which is the outlet for these oxygen and air.
It ignited at. Combustion after ignition does not proceed sequentially from the ignited riser side, but immediately reaches the weir portion 102, and the combustion is started with that portion as the first main combustion portion.

The direction of the ceramic pipes of the frying 121, 122 is set to 45 ° downward, and a large amount of agitating air 11 is provided on the lower mold surface side.
The reason why 9 and 120 hit is that-generally, it is advantageous in casting that the casting position of the casting is a complicated surface on the lower mold surface of the mold cavity, so the combustion condition is not good on the lower mold surface side. Corner,
This is because a large number of concave portions are generated and the combustion conditions on the lower mold surface side are deteriorated, so that they are compensated for.

The jetting direction of these stirring air in the horizontal plane is arranged 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, by rotating the air flow as a whole, combustion proceeds more smoothly.

FIG. 8 is a diagram showing the slightly latter half of the state in which combustion is vigorous after ignition. As shown in FIG. 8, in the space 140 formed by the mold wall 138 and the model combustion surface 139, heat, combustibles, and oxygen are uniformly distributed by the stirring airflow in which the stirring air and oxygen are mixed in a turbulent flow 141. Combustion proceeds promptly because it is stirred. In such a combustion state, the condensate does not drop from the combustion surface 142 on the upper surface side of the model, and therefore the condensate burns without being deposited on the lower surface side of the mold cavity.

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

At the final point, the agitating air is set to 100
Reduced to liters / minute, open lid surface 145 with lid 14
6 was carried out to increase the oxygen concentration in the mold and completely burn the tar-like condensates that were individually divided and burned.

FIG. 9 shows 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 soot and drop-deposited tar-like condensate-free mold cavity 144 retained 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, 50 mm to 80 mm from the bottom of the rectangular PMMA model 224 of 500 width × 1700 length × 250 thickness.
A 30 × 30 mm square vent hole 225 was opened in the mm portion, and a hot water 226 with an outer diameter of 200 mm × 200 mm height with a vent hole having an inner diameter of 50 mm opened at one end was used as a model. Fiber reinforced coating type 2 in which 1 vol% of silicon carbide fiber is mixed in this model
27 was applied to prepare a model for molding. A porcelain weir 228 having a diameter of 30 mm was provided on one end of this model, and the mold was filled with sand 230 in the molding sand 229 before the combustion to complete. At this time, in order to observe the burning condition of the model in the mold by utilizing the fact that the mold sand was heated by the heat of combustion of the model and smoked, the thickness of the sand on the upper surface side of the mold was reduced to about 50 mm.

A ceramic pipe 23 connected to the weir 228 is added to the above mold.
2 was passed through a pipe 233 of φ10 mm, and the circumference thereof was sealed with a clay seal 234, and about 100 L / min of oxygen 235 was made to flow, and ignition was performed by a burner 217 for ignition from a downstream hot water 226. After the ignition, the flame 219 immediately traces back inside the rectangular ventilation port and spreads to the upstream weir 228. In this way, in the midstream range, the combustion does not spread in the lateral direction, that is, the wall direction inside the vent hole, and the flame spreads immediately to the weir part made of ceramics because the tip 218 on the upstream side of the inner surface part of the vent hole is burning. The three elements of combustion, heat, combustibles, and oxygen, are fully filled, and the combustion is most active in that area. It is thought that this is because the gas is a mixture of the above and the combustion is suppressed due to lack of oxygen. When the fire spreads to the most upstream part, there is a weir 228 made of a ceramic pipe beyond that, and there is no combustible material, and the fire stops.

FIG. 11B is a diagram showing the situation after the fire has spread to the weir section at the most upstream side. When the fire spreads to the most upstream part, it burns vigorously around the upstream range 208, forming a combustion center 222. This situation can be observed from outside the mold by the generation of smoke 236. Immediately after that, middle range 2
Two or three small explosions 221 occur within 10 models. At this point, the portion of the most downstream portion open to the atmosphere is sufficiently supplied with the heat of the unburned gas combustible material and the combustion exhaust gas, the heat of combustion of this portion, and the oxygen 213 in the atmosphere. The flame 219 is formed and burned. At this time, the model surface 223 around the outlet of the ventilation port burns to the inside (upstream side), but its speed is the combustion center 222 on the upstream side.
Is slower than the downstream speed.

FIG. 11C is a diagram showing a situation in the final stage after the combustion in the most upstream portion is started. Looking at the movement of the combustion center as a whole, the oxygen moves from the upstream range where oxygen is the most to the downstream range. This is determined by observing the downstream movement 237 of the smoke producing portion. At the end of combustion, the lower die surface side from the slightly downstream side in the middle flow range finally burns, and the entire combustion ends. In this situation, at this point, the amount of unburned gas also decreases, the momentum of the flame in the downstream range also decreases, and then the state of "fire" occurs, so that the final combustion part 238 and its part from the riser part. It is observed by observing the flame 239 of the final combustion part formed in FIG.

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

As described above, in the process of burning and extinguishing the model while supplying oxygen or the 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 of the model, that is, to the atmosphere. By igniting at the exit of the, it is possible to safely ignite without causing a large explosion phenomenon. Example 3 One of the other aspects of the present invention will be described by way of example.
FIG. 1 to FIG. 6 are views showing an example using a particularly small carbon absorption test piece. As the coating type, a commercially available coating type material containing an inorganic or organic binder with 50 to 90% of aggregate fine particles of 60 μm under was used. About 100 m of single glass fibers with a fiber diameter of 13 μm and a fiber length of 13 mm are coated with an alkali-resistant fiber, and a width of about 1 m
A strip-shaped material having a thickness of m and a thickness of about 0.05 mm was used as a reinforcing material.

As for the fibers mixed in as described above, fibers having a certain degree of rigidity are better dispersed and kneaded in the coating mold without causing entanglement during stirring. Model materials are EPS and EPMM
Two types of A were used and each was compared.

FIG. 1 shows an example in which a test piece for carbon absorption test was cast. In an example of casting a test piece for carbon absorption test in which a 326 mm square and 40 mm thick plate was attached to a 100 mm square 710 mm long prism, application of a mold coating material, auxiliary combustion piping, a vent, and an electric type It shows an ignition device. Two types of model materials, EPS and EPMMA, were used.

200 mm in diameter and 200 m in height at the upper end of the prism.
m of riser 1 was attached, and a model 4 for vanishing model was opened with a ventilation hole 3 penetrating about 25 mmφ from the weir 2 at the lower end to the top of the riser 1.
And dried 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 was attached to the lower end, and an auxiliary combustion drilling hole 7 was opened in one corner of each plate-shaped part, and an auxiliary combustion pipe made of a steel pipe of about 10 mmφ and a vinyl pipe. 8 was attached.

It is not good to use a commercially available combustion type feeder sleeve in the feeder section in order to extinguish the combustion while supplying air and oxygen because the feeder sleeve burns. As shown in this embodiment, it is better to manufacture the riser part with a foam model.

After the preparation of the model was completed, as shown in FIG. 2, an embedded mold was made in the mold sand 9. In this case, it is necessary that the gate 10 for supplying air and oxygen, the weir 2, and the vent 3 are communicated with each other before the ignition, and it is preferable to partially fill them for the sake of molding. Absent.

After the molding, a pipe 11 for supplying oxygen and air and a tank 12 were connected to the sprue 10 and the auxiliary combustion pipe 8 communicating with the weir 2, and compressed air of 6.0 kgf / square centimeter and 150 kgf / 150 cmgf / cm 2 respectively. Oxygen from a compressed oxygen cylinder of square centimeter was piped, and while adjusting the flow rates of the air 13, 15 and oxygen 14, 16, the electric ignition device 6 was energized and the model 4 was ignited from the weir 2.

After the ignition, while watching the combustion state, the adjusting valves 17, 18, 19, 20 are used at appropriate times, and the air 13, 15 is used.
And the amounts of oxygen 14 and 16 were adjusted, and the model 4 was burned.
After that, it was confirmed that the flame and the smoke 21 had disappeared and the combustion disappearance was completely completed. In addition, the combustion disappearance time of the model is EP
The S model was about 17 minutes, and the EPMMA model was about 10 minutes.

As shown in FIG. 3, air and oxygen piping 1
1, 17, 18, 13, 14 and 8, 12, 19, 20,
Remove 15 and 16 and add C = 0.22wt% to the sprue 10.
The nozzle portion 24 of the ladle 23 filled with the molten steel 22 was matched, the stopper 25 was opened, and the molten steel 22 was injected into the mold cavity portion 26 held by the mold coating material layer 5 to perform casting. In addition, the same model for comparison is a normal disappearance model casting method,
That is, the same molten steel was cast from the 40 mmφ weir at the lower end without burning before injecting the molten metal. The same molten steel was cast using an EPS model and an EPMMA model of the same type, and for comparison, a normal vanishing model casting method was also used. A total of 2 pieces made of EPS and 2 pieces made of EPMMA were cast.

FIG. 4 shows the position where the carbon amount was measured by cutting out the sample from each position (A to D, 1 to 4) of the test piece for carbon absorption test. Table 1 shown as FIG. 5 shows the results by the EPS model, and Table 2 shown as FIG. 6 shows the results by the EPMMA model.

The carbon analysis results of the EPS model shown in Table 1 are as follows. In the conventional method, the test piece central portions A, B,
The carbon analysis values of C and D and the end portions 1, 2, 3, 4 increase toward the upper part, and particularly in the end portion 1, 0.42 wt%, which is 0.20 wt% with respect to the original component. Also, when focusing on the bulkiness, the central portion is 0.03 wt% and the end portions are 0.17.
wt%.

Such variations in the carbon content make it difficult to manufacture cast steel products by the conventional vanishing model casting method.
On the other hand, the values according to the present invention do not show a clear change in the carbon component due to the vertical position as in the conventional method. Focusing on the bulkiness, the central portion is 0.01 wt% and the end portions are 0.01 wt%, which is not a measurement error.

The carbon analysis results of the EPMMA model shown in Table 2 are as follows. In the conventional method, the carbon analysis values increase as the upper portions of the central portions A, B, C, D and the end portions 1, 2, 3, 4 of the test piece increase, and the variation thereof is 0.
It is 04 wt% and the edge portion is 0.02 wt%. It is recognized that carbon infiltration into molten steel occurs even in the EPMMA model whose decomposition performance is further improved. The value according to the invention is
Similar to the EPS model results, no change in the carbon component depending on the vertical position is observed. If you pay attention to the barracchi, the central part is 0.
The amount is 01 wt% and the edge portion is 0.00 wt%, which is similar to the result of EPS, and there is little difference in measurement.

As described above, since the vanishing model is burned out and removed before the injection of the molten metal, the vanishing model casting method according to the present invention has the greatest drawback of the conventional carbon, regardless of the material of the vanishing model. It can solve the minute absorption problem. In the case of the casting weight of about 250 kg shown in this embodiment, it is sufficient that the fibers mixed in the mold coating material have heat resistance as high as glass fibers.

[0095]

The effects of the present invention are as follows. (1) It is possible to eliminate the total carbon absorption and local uneven distribution of cast iron and cast steel products by the conventional vanishing model casting method. (2) Since a large cast product of several Ton can be cast, there is no limitation on the size of the cast product. (3) Cast iron and cast steel products with specified carbon content can be manufactured by the disappearance model casting method. (4) High-grade castings including low-carbon stainless steel castings can also be cast by the disappearance model casting method. (5) It is possible to manufacture a precision cast product similar to the Replicast CS method without the size limitation of the cast product. (6) The infiltration of hydrogen contained in the organic foam model into the molten metal can be prevented. (7) It is possible to solve the gas blow problem of a cast product generated by absorption of oxygen gas, carbon dioxide gas, and nitrogen gas, which is a drawback of the conventional disappearance model method. (8) If the model material is one that basically burns and disappears,
The presence or absence of foaming or the type of material does not matter. Further, the following effects can be obtained. (9) When the model embedded in the mold is burned, the model can be sufficiently burned out to the corners and recesses. (10) It is possible to prevent deposition of tar-like model condensate on the lower surface side of the mold cavity. (11) It is possible to easily perform molding without installing an oxygen supply pipe that partially supplies oxygen for promoting combustion in a portion where combustion is feared in advance. Further, the following effects can be obtained. (12) When burning the model embedded in the mold,
Can ignite safely without causing an explosion phenomenon.

[Brief description of drawings]

FIG. 1 is a diagram showing a coating state of a coating mold in the casting of a test piece for a carbon absorption test, an arrangement of auxiliary combustion pipes, a vent, and an electric ignition device.

FIG. 2 is a diagram showing a state in which a test piece for a carbon absorption test is molded in foundry sand, and a model is burned and disappeared before casting.

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

FIG. 4 is a diagram showing analysis positions of carbon components in a cast carbon absorption test specimen.

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

FIG. 6 is a table showing carbon distribution in a casting in casting using an EPMMA model as Table 2.

FIG. 7 is a diagram explaining a combustion method of the present invention.

[Fig. 8] Fig. 8 is a diagram showing a slightly latter half of a state where combustion is actively performed after ignition.

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

FIG. 10 is a diagram for explaining the principle of the ignition method of the present invention.

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

[Explanation of symbols] 1 riser 2 weir 3 vents 4 disappearance model 5 Coating material layer 6 Electric ignition device 7 Drill holes for auxiliary combustion 8 Auxiliary combustion piping 9 Mold sand 10 gate 11 piping 12 tanks 13,15 air 14,16 oxygen 17,18,19,20 Regulator valve 21 Flame and smoke 22 Molten steel 23 ladle 24 nozzle 25 stopper 26 Mold cavity

Claims (5)

(57) [Claims] 1. A vanishing model casting method comprising the following steps. (A) a step of applying a coating mold in which a fiber reinforcing material is mixed in advance to a disappearing model and drying and solidifying; and (b) a step of embedding the dried model in a mold material to create a mold, (c) ) The disappearance model in the mold is provided with an oxygen supply port,
A separate supply port for stirring air is provided, oxygen is supplied from the weir part communicating from the mold spout, while stirring air is supplied so as to be blown into the mold from the frying part, the model is ignited,
Burning the vanishing model to vanish, and (d) injecting molten metal into the space formed by the burning and casting. 2. A vanishing model casting method comprising the following steps. (A) a step of applying a coating mold in which a fiber reinforcing material is mixed in advance to a disappearing model and drying and solidifying; and (b) a step of embedding the dried model in a mold material to create a mold, (c) ) Oxygen and stirring air are supplied to the vanishing model in the mold, and when the stirring air is supplied, the oxygen-containing gas supplied to the space formed by the mold wall and the model combustion surface is supplied to the space. Stir well in the space to evenly generate heat and supply oxygen in the space,
A step of burning and disappearing; and (d) a step of injecting molten metal into the space formed by the burning and casting. 3. The disappearance according to claim 1, wherein the stirring air is further supplied so that exhaust gas generated by combustion in the space is quickly discharged from the space. Model casting method. 4. A vent is provided in the vanishing model, oxygen or a mixed gas of oxygen and air is supplied from the vent, and unburned gas in the downstream region of the vanishing model near the vent outlet and its surroundings. The vanishing model casting method according to any one of claims 1 to 3, characterized in that the mixed gas with the air is ignited so as to be stably burned. 5. A vent hole is provided in the vanishing model, oxygen or a mixed gas of oxygen and air is supplied from the vent hole, and ventilation is provided on the downstream side with respect to the flow of the oxygen or the mixed gas of oxygen and air. The vanishing model casting method according to any one of claims 1 to 3, wherein ignition is performed at a mouth outlet.