JP2015009266A - Lost foam pattern, material for lost foam pattern, casting process for lost foam pattern - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lost foam pattern, a material for the lost foam pattern, and a casting process for the lost foam pattern which can excellently suppress the generation of a casting defect caused by a gas or residues resultant from the pyrolysis of the lost foam pattern.SOLUTION: The lost foam pattern is constituted of a foamed plastic containing an iron oxide in a dispersed state. Non heat build-up FeOcan be used as the iron oxide, and foamed polystyrene can be used as the foamed plastic. The proportion of polystyrene to FeOcan be adjusted to FeO: 0.005 - 0.30 pts.wt. with respect to polystyrene: 99.995 - 99.70 pts.wt. Further, a material for the lost foam pattern can be made of a foamed plastic bead containing the iron oxide. Furthermore, the casting process for the lost foam pattern comprises casting by a casting mold using the lost foam pattern.

Description

  The present invention relates to a vanishing model used for casting, a material for a vanishing model used for manufacturing the vanishing model, and a vanishing model casting method using the vanishing model.

The vanishing model casting method is a casting method also called a full mold method. This casting method is a casting method in which a model molded from foamed plastic is embedded in foundry sand, and the model disappears by heat by casting molten metal, and the cast is cast in the lost model space. It is.
This vanishing model casting method has an advantage that a product having a complicated shape can be easily manufactured with a short delivery time.
On the other hand, there is a drawback that casting defects are likely to occur due to gas and residue generated when the foamed plastic model is thermally decomposed.

As techniques for improving the disappearance model casting method, the following patent documents 1 to 3 disclose techniques relating to the resin itself used for the material for the disappearance model.
That is, Patent Document 1 discloses a technique for forming a disappearance model using a thermoplastic resin having a small oxygen index as a material for the disappearance model.
Patent Document 2 discloses a technique that uses a foamed resin impregnated with a resin obtained by polymerizing styrene and methacrylic acid ester as a foaming resin that is a material for disappearance model.
Patent Document 3 discloses a technique in which polyethylene or polypropylene, which is more easily thermally decomposed than polystyrene, is used as a part of the disappearance model as a material for the disappearance model.
Further, as other improvement methods of the disappearance model casting method, the following Patent Documents 4 to 7 disclose techniques relating to a coating agent applied to the surface of the disappearance model.
That is, Patent Document 4 discloses a technique of a coating agent composition in which organic particulate matter is contained in a refractory aggregate.
Patent Document 5 discloses a technique in which a heat generating agent is used on a disappearance model, mainly on the surface of the disappearance model.
Patent Document 6 discloses a coating agent containing ore called perlite such as pearlite, obsidian, pine stone, pyroxene, diopside, rasbite, rose pyroxene, muscovite, orthoclase, syenite, and the like. ing.
Patent Document 7 discloses a coating agent containing a refractory aggregate and foamed synthetic resin granules.
Further, as still another improved method of the disappearance model casting method, the following Patent Documents 8 and 9 disclose a technique in which an additive is added to the disappearance model material.
That is, Patent Document 8 discloses a technique in which an antioxidant is added to a disappearance model material.
Patent Document 9 discloses a technique in which a metal or an alloy that generates heat upon contact with a molten metal is added to a disappearance model material as a heat generating agent.

JP-A-8-1273 JP-A-10-76347 JP 2000-140994 A Japanese Patent Laid-Open No. 2001-1104 JP 2001-347343 A JP 2003-290869 A JP 2009-214126 A Japanese Patent Laid-Open No. 11-244993 JP 2002-307135 A

The inventions in Patent Documents 1 to 3 are inventions related to the foamed resin itself used for the disappearance model material, but problems remain in terms of material price and manufacturing cost.
The inventions of Patent Documents 4 to 7 are mainly inventions of disappearance model coating agents. And especially in patent document 5, it is disclosed that a heat generating agent is contained in the model, and it is disclosed that combustion of the residue attached to the casting surface by this heat generation is promoted. However, the effect of reducing casting defects was limited.
The inventions in Patent Documents 8 and 9 are inventions in which an additive material is included in the disappearance model material. And especially in patent document 9, the disappearance model material which added the exothermic metal is disclosed, and it is disclosed that the thermal decomposition of the disappearance model is promoted by suppressing the temperature drop of the molten metal by this heat generation. However, there is a problem of disappearance residue and gas entrainment due to a local radical reaction due to heat generation, and further, a problem of damage of the disappearance model and its mold.

  Therefore, the present invention can solve the problems in the disappearance model casting method that cannot be sufficiently solved by the conventional technique, and can satisfactorily suppress the occurrence of casting defects due to gas and residue resulting from the thermal decomposition of the disappearance model. It is an object to provide a vanishing model, a vanishing model material used for manufacturing the vanishing model, and a vanishing model casting method using the vanishing model.

As a result of repeating various experiments to investigate and investigate the cause in order to eliminate the defects in the conventional disappearance model casting method, the present inventor has found that the cause of the above defects in the disappearance model casting method is the heat insulation of the disappearance model foam plastic. It turned out to be deeply related to sex.
That is, in the disappearance model casting method, the molten metal is poured from a sprue, passed through a runner, a weir, etc. Casting is performed by replacing with molten metal while disassembling and disappearing.
At this time, since the foamed plastic as the disappearance model has high heat insulating properties, only the local area in contact with the molten metal tends to be rapidly heated. For this reason, the decomposition reaction of the disappearance model proceeds rapidly in the contact area, and a large amount of gas and residue are rapidly generated. Moreover, since a rapid high gas pressure situation occurs in the contact area, the flowing molten metal flow tends to be turbulent in the contact area.
Under such circumstances, casting defects increase as a result of the enormous amount of gas and residue generated in the turbulent molten metal flow being entrained one after another in each contact area.

  As a result of further repeated experiments and examinations based on the above-described investigation of the cause, the present inventor reduced the heat dissipation of the disappearance model by reducing the heat insulation property of the disappearance model, while reducing the temperature unevenness and the disappearance of the disappearance model. It is possible to ensure a uniform temperature rise over a wide range of the model, which makes it possible to reduce the pyrolysis residue of the disappeared model and the entrainment of the generated gas into the molten metal flow. It has been found that it is possible to move to the residue reservoir / pushing hot water portion in an orderly manner and to provide a casting with few casting defects, and the present invention has been completed.

That is, the disappearance model of the present invention based on the above knowledge is a disappearance model used in the disappearance model casting method, and has a first feature that it is composed of a foamed plastic containing iron oxide in a dispersed state.
In addition to the first feature, the disappearance model of the present invention has a second feature that the iron oxide is Fe ₂ O _3, which is non-exothermic iron oxide.
Further, in the disappearance model of the present invention, in addition to the second feature, the foamed plastic is made of expanded polystyrene, and the ratio of polystyrene to Fe ₂ O ₃ is 99.995 to 99.70 parts by weight of polystyrene. Fe ₂ O ₃ : The third characteristic is that it is adjusted to 0.005 to 0.30 parts by weight.
The disappearance model material of the present invention is an disappearance model material used for manufacturing the disappearance model according to any one of the first to third features, and kneads foam plastic beads and iron oxide powder. The fourth feature is that it is a foam block body.
Further, the disappearance model material of the present invention is an disappearance model material used for manufacturing the disappearance model according to any one of the first to third features, in which iron oxide is dispersed in advance in foamed plastic beads. The fifth feature is that it is contained in the above.
The vanishing model casting method of the present invention uses the vanishing model according to any one of the first to third features, and embeds it in a casting sand as a mold and casts an iron-based molten metal into the mold. Thus, the sixth feature is to obtain a casting while eliminating the disappearance model.

According to the disappearance model of claim 1, since it is made of foamed plastic containing iron oxide in a dispersed state,
The thermal conductivity of the disappearance model is improved, and it is possible to reduce the extreme decomposition reaction in the contact area with the melt of the disappearance model and the entrainment of the disappearance model residue and gas into the melt.
In addition, since the thermal conductivity of the disappearance model is improved, a gentle temperature gradient is ensured by the entire disappearance model, and a wider and homogeneous decomposition reaction is gently and orderly advanced from upstream to downstream of molten metal intrusion. be able to. As a result, the disappearance model residue and the entanglement of the gas into the molten metal are reduced, and the generated disappearance model residue can be reliably moved to the end portion of the hot water around the residue reservoir and the hot water portion. This can also provide a casting with sufficiently few defects.
Of course, since local mass generation of gas due to local radical reaction can be avoided, degassing by diffusion of gas into foundry sand becomes good. Moreover, since the turbulent flow of the molten metal can be prevented, not only the disappearance model residue but also the entrainment of the coating agent and the foundry sand can be sufficiently reduced.
Furthermore, since the additive to the disappearance model is iron oxide, unlike the metal itself, it can be eliminated as slag without worrying about melting in the molten metal. In particular, iron-based castings can be easily removed as oxide slag floating on the molten metal without causing problems as impurities.

Further, according to the disappearance model of claim 2, in addition to the function and effect of the configuration of claim 1, the iron oxide is Fe ₂ O ₃ which is non-exothermic iron oxide.
Even in the contact area of the disappearance model that comes into contact with the molten metal that has entered, since Fe ₂ O ₃ does not generate heat due to contact with the molten metal, further increase in temperature at the contact area, associated excess reaction, excess residue, Generation of excess gas and turbulence of the molten metal can be prevented. On the other hand, the heat from the molten metal can be conducted in a wide range and quickly from the contact local area to the surrounding area by the presence of Fe ₂ O ₃ , and can be soaked into a gentle thermal gradient. For this reason, the entire disappearance model can be dissipated more gently and in a broader range from the upstream to the downstream of the molten metal flow, and a good casting with few defects can be obtained.

Further, according to the disappearance model of claim 3, in addition to the function and effect of the configuration of claim 2, the foamed plastic is made of foamed polystyrene, and the ratio of polystyrene to Fe ₂ O ₃ is polystyrene: 99.995 ~99.70 _Fe 2 _O 3 by weight parts: 0.005 to 0.30 because it is adjusted to parts by weight,
Even when using an extinguishing model made of expanded polystyrene, which is cheap and easy to handle, the entire disappearing model is quickly heated with a gentle temperature gradient during pouring, and the heat of the disappearing model from the upstream side to the downstream side is poured. Decomposition proceeds in an orderly fashion, and the generated gas spreads over the entire area, not locally, allowing it to escape into the mold sand space, and the molten metal can be gently filled into the disappearing model space without any turbulence in the flow. . Further, the residue can be well lifted to the residue reservoir / push-up portion at the end portion and removed from the casting.
Fe ₂ O ₃ to be to 0.005 part by weight or more, it is possible to actually achieve the effects of the above. Also by the _Fe 2 _{O 3} and 0.30 part by weight, _Fe 2 _{O 3} in the casting can be prevented from remaining as a defect. In addition, when it exceeds 0.30 weight part, consumption of the cutter used at the time of manufacture of a vanishing model will become intense.

Further, according to the disappearance model material according to claim 4, the disappearance model material used for manufacturing the disappearance model according to any one of the first to third features, wherein the foamed plastic beads and the iron oxide are used. Since it is kneaded with powder as a foam block body,
By using commercially available foamed plastic beads and iron oxide powder, it is possible to easily obtain a foam block body containing dispersed iron oxide at low cost, and from the foam block body, containing iron oxide easily. Disappeared model can be obtained.

Further, according to the material for disappearance model according to claim 5, the material for disappearance model used for manufacturing the disappearance model according to any one of the first to third features, the foamed plastic Since iron oxide is contained in a dispersed state,
By creating a disappearance model using the foamed plastic beads, a disappearance model made of foamed plastic containing iron oxide in a dispersed state can be obtained. Therefore, a good casting with few defects can be obtained by performing disappearance model casting using the disappearance model in which this iron oxide is contained in a dispersed state.

According to the vanishing model casting method of claim 6, the vanishing model according to any one of the first to third features is used, and the cast is embedded in foundry sand as a mold. By casting the molten metal, we are trying to obtain a casting while eliminating the disappearance model.
There are few residues and gas entrainment accompanying the disappearance of the disappearance model, and in addition, iron oxide dispersed in the disappearance model can be easily eliminated as slag, thus obtaining a good cast iron casting such as a cast iron casting with less impurities be able to.

  The vanishing model, vanishing model material, and vanishing model casting method of the present invention will be described below with respect to the embodiments thereof.

In the disappearance model material according to the embodiment of the present invention, foamed plastic beads contain at least iron oxide in a dispersed state.
The foamed plastic beads may be any resin that is thermally decomposed and disappears when heated to a high temperature and can be foamed.
Examples of such resins include polystyrene resins, poly (meth) acrylic ester resins, vinylidene chloride resins, and polyolefin resins.
In practice, depending on the cast metal and alloy to be cast, foamed plastic that is successfully pyrolyzed and disappears at the casting temperature of the molten metal is used. In the case of cast iron casting, expanded polystyrene is often used.
The resin to be used is foamed by containing a foaming agent to obtain beads. A known foaming agent can be used as the foaming agent.
After forming the block into a block body using the foamed plastic beads, the disappeared model can be obtained by processing the predetermined model by cutting or the like. Further, a disappearance model can be obtained by molding using the beads.

As the iron oxide, Fe ₂ O ₃ which is a trivalent iron oxide referred to as a valve is used.
Fe ₂ O ₃ is non-exothermic and does not generate heat due to contact with molten metal. Therefore, there is no fear of promoting reaction intensification due to heat generation even at the contact interface of the disappearance model that comes into contact with the molten metal.
Iron oxide is used in powder form. By adding iron oxide powder in the foamed plastic bead manufacturing process, foamed plastic beads containing iron oxide in a uniform dispersed state can be obtained.
The particle size of the iron oxide powder is not particularly limited, but is preferably small. For example, when using a petite as iron oxide, a particle diameter of 1 to 300 μm can be used. Preferably, a 10-50 micrometers thing is used.

The amount of iron oxide contained in the foamed plastic is not particularly limited. The amount of the foamed plastic used, the degree of foaming, and the disappearance model should be as small as possible and improve the necessary heat conduction. Depending on the size and shape, the ratio can be obtained in advance by experiments.
As foam plastic to be used, with expanded polystyrene, in the case of using _Fe 2 _{O 3} as iron oxide, 99.995 to 99.70 parts by weight of expanded polystyrene, the _Fe 2 _{O 3 0.005~0.30} parts The ratio of
When the Fe ₂ O ₃ is less than 0.005 parts by weight, an effective effect cannot be obtained. On the other hand, if the amount exceeds 0.30 parts by weight, the blade may be consumed at the time of processing the model, and iron oxide may remain as a defect.
The content ratio between the expanded polystyrene and Fe ₂ O ₃ is preferably 0.01 to 0.20 parts by weight of Fe ₂ O _{3 and} 99.99 for expanded polystyrene with respect to 99.99 to 99.80 parts by weight of expanded polystyrene. Fe ₂ O ₃ is more preferably 0.01 to 0.10 parts by weight with respect to ˜99.90 parts by weight.

  The material constituting the foamed plastic beads may include a plastic material, iron oxide, a foaming agent, an auxiliary agent, and other materials.

The disappearance model of the present invention uses the above-mentioned foamed plastic beads in which iron oxide is dispersed in advance. As described above, the beads are molded into a block body and then processed into a predetermined shape by cutting or the like. Can be obtained at Further, the disappearance model can be obtained by directly molding using the beads.
The surface of the vanishing model can be finished by applying a coating agent to prevent seizure and for other purposes.

  The disappearance model of the present invention is a foamed block body obtained by kneading the foamed plastic beads not containing iron oxide and the iron oxide powder at the above ratio and then forming a foam block body. It can also be configured as a disappearance model by cutting or the like. Even in this case, a disappearance model in which iron oxide is contained in a dispersed state can be obtained.

The vanishing model casting method according to the embodiment of the present invention uses the vanishing model described above, and after applying the coating agent, arranges the weir, runner, gate, and other necessary members so as to be down-cast. By burying this in the foundry sand, if necessary, placing the residue reservoir and pusher at the end filled with the molten metal, thereby forming a casting mold, and casting the molten metal into this mold, This is a method of obtaining a casting in the disappearance model space while disappearing the disappearance model.
The molten metal is gray cast iron, cast iron melt including spheroidal graphite cast iron, and other iron-based melts.

The cast molten metal passes through the gate, runner, and weir and fills the model from the bottom to the top. The disappearance model disappears when the molten metal enters, and is replaced with molten metal.
In the case of casting using the conventional disappearance model, a large amount of disappearance model residue and gas are generated in the contact area of the disappearance model that comes into contact with the molten metal, and the gas pressure increases partially, against the gas pressure. The coating agent, sand, and the like caught in the flowing molten metal gather near the final filling portion of the disappearance model, and casting defects are likely to occur in that portion.
On the other hand, in the disappearance model casting according to the embodiment of the present invention, when the cast molten metal reaches the disappearance model, the iron oxide powder of the entire model is heated, and the thermal decomposition of the entire disappearance model is promptly promoted. The As a result, the gas pressure applied to the disappearance model becomes almost uniform, and there is little disturbance of the cast molten metal flow, and the filling of the molten metal proceeds gently.

As described above, since the iron oxide powder itself is not a heat generating agent, no thermal decomposition occurs explosively. Further, there is no phenomenon that the gas pressure only in the vicinity of the molten metal flow rapidly increases, so that the peeling of the coating agent or the entrainment of foundry sand due to the molten metal flow is less likely to occur.
In the case of vanishing model casting according to the embodiment of the present invention, the gas pressure is applied over a relatively wide range, so that it easily escapes in the direction of the sand mold. Thereby, the deterioration of the casting surface by gas can be prevented.
In addition, for the residual defects peculiar to the disappearance model casting method, the cast molten metal will fill the mold gently, so that it will float well in the residue reservoir / push-up part installed on the upper mold surface in advance. become

  As described above, according to the vanishing model casting method according to the embodiment of the present invention, it becomes close to the manufacturing state when the molten metal is cast into the mold formed using the wooden mold, and the casting unique to the vanishing model casting method. Defects can be prevented.

Using an iron oxide powder (valve) of Fe ₂ O ₃ , foam polystyrene blocks having different contents were produced, and these foam polystyrene blocks were processed into a predetermined shape. The disappearance model of Example 7 was produced. As a comparative example, a disappearance model of expanded polystyrene not containing iron oxide was prepared.
Using each disappearance model of Examples 1 to 7 and the comparative example, a coating agent was applied under the same conditions, and after placing a weir, a runner, and a gate, it was buried in foundry sand and A mold was prepared.
Using the FCD800 equivalent material as the molten metal for casting, actual casting was performed to obtain a casting. Casting conditions such as dissolution conditions, graphite spheroidization conditions, and casting temperature conditions were the same for each of Examples 1 to 7 and Comparative Example.
Evaluation is based on iron oxide powder content, dispersion status, disappearance model workability, casting speed, product appearance, and the surface of the casting upper mold where defects are likely to occur. It was performed by observing, analyzing, measuring, etc.
The results are shown in Table 1.

In Table 1,
* Note 1: The content (% by weight) of iron oxide (Fe ₂ O ₃ ) powder with respect to expanded polystyrene.
* 2: Indicates the state of dispersion of iron oxide (Fe ₂ O ₃ ) powder dispersed in the disappearance model, where ◯ indicates good and Δ indicates unevenness but generally acceptable.
・ Note 3: The workability at the time of making the disappearance model is indicated by the state of wear of the blade, ◎ indicates that the wear is low and excellent, ○ indicates that it is good, and △ indicates that wear is possible but generally acceptable.
・ Note 4: Shows the time until the cast molten metal is filled with the disappearance model. As the disappearance model is thermally decomposed and gas is generated locally, the generated gas pressure becomes higher, the casting speed becomes lower, and the disappearance model residue and the gas are more involved. The faster the casting speed, the better.
・ Note 5: Shows the surface condition of the manufactured castings, ◎ indicates that there are no surface defects, is excellent, ○ indicates that there are defects such as poor casting skin, but is generally acceptable, and × indicates that many defects are not possible.
・ Note 6: ◎ indicates excellent without defects, ○ indicates good, △ indicates defects are generally acceptable, but × indicates many defects.

From Table 1 above, in the case of the comparative example not containing iron oxide, there are many defects on the appearance evaluation and product casting upper die processing surface, which is impossible.
On the other hand, in Example 1 to Example 7 (the content of Fe ₂ O ₃ powder is 0.005 to 0.30% by weight), the appearance evaluation and the evaluation on the product casting upper die processed surface are improved. I understand.
In Examples 2 to 6 (the content of Fe ₂ O ₃ powder is 0.01 to 0.20 wt%), the appearance evaluation and the evaluation on the product casting upper die processing surface are further improved. I understand that.
Furthermore, in Examples 2 to 5 (the content of Fe ₂ O ₃ powder is 0.01 to 0.10% by weight), the appearance evaluation and the evaluation on the product casting upper die processed surface are ○ (good) to ◎ ( It can be seen that the processability of the disappearance model is also ◯ (good) to ◎ (excellent).

Claims (6)

  A vanishing model for use in a vanishing model casting method, comprising a foamed plastic containing iron oxide in a dispersed state. The disappearance model according to claim 1, wherein the iron oxide is Fe ₂ O ₃ which is non-exothermic iron oxide. The foamed plastic is made of expanded polystyrene, and the ratio of polystyrene and Fe ₂ O ₃ is adjusted to Fe ₂ O ₃ : 0.005 to 0.30 parts by weight with respect to polystyrene: 99.995 to 99.70 parts by weight. The disappearance model according to claim 2, wherein   It is the material for disappearance models used for manufacture of the disappearance model in any one of Claims 1-3, Comprising: The bead of foamed plastic and iron oxide powder are knead | mixed, It is characterized by the above-mentioned. Material for disappearance model.   The disappearance model material used for the production of the disappearance model according to any one of claims 1 to 3, wherein iron oxide is previously contained in a dispersed state in foamed plastic beads. Materials.   Using the disappearance model according to any one of claims 1 to 3, a casting is obtained while erasing the disappearance model by embedding it in casting sand to form a casting mold and casting an iron-based molten metal into the casting mold. The disappearing model casting method characterized by this.