JP2014136245A - Casting mold for casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a gas defect of a casting caused by moisture, by surely removing the moisture included in an inside area of a sand mold.SOLUTION: Panel materials 28a-28j composed of an adsorbent such as zeolite or ALC are laid on an inner surface of casting frames 14 and 18, and are also fixed on a floor surface F. The sand molds 16 and 18 composed of casting sand are arranged inside these panel materials, and an outside surface of the sand molds 16 and 18 contacts with the panel materials. Cavities c1 and c2 are formed inside the sand molds 16 and 18, and cores 20 and 22 are arranged in the center of the cavities c1 and c2. A reinforcement-inserted adsorbent 36 is embedded in a sand mold 34 forming the core 20. The moisture included in the sand molds 16, 18 and 34 is adsorbed by the panel materials 28a-28j and the adsorbent 36.

Description

  The present invention relates to a casting mold capable of preventing a gas defect among surface defects generated in a manufactured casting.

  In a cast product manufactured using a sand mold formed from cast sand, surface defects may occur during casting. When surface defects occur, a great deal of labor and cost are required for repair work. One of the surface defects is a gas defect. One of the causes of gas defects is due to moisture contained in the sand mold. This is because moisture is vaporized by the heat of the molten metal and this remains as bubbles in the cast product, resulting in a cavity.

As a countermeasure, there is a method in which hot air is sent into a molten metal injection cavity formed in a sand mold to dry the sand mold facing the cavity. This method will be described with reference to FIG.
In FIG. 6, a casting mold 100 is disposed on the floor surface F. The casting mold 100 is composed of an upper mold 102 and a lower mold 104 formed separately. The upper mold 102 and the lower mold 104 are filled with sand molds 106 and 108 formed of cast sand, respectively. In the sand molds 106 and 108, cavities c1 and c2 are formed, respectively.

  Cores 110 and 112 are arranged at the centers of the cavities c1 and c2, respectively. The surfaces of the sand molds 106 and 108 and the surfaces of the cores 110 and 112 form cavities c1 and c2. A cored bar 114 is embedded in the core 112 for reinforcement. Casting work is performed by injecting molten metal into the cavities c1 and c2, but before that, hot air h is supplied from the hot air dryer 116 to the cavities c1 and c2 via the hose 118. The sand molds 106 and 108 are dried by the hot air h, the water contained in the sand molds 106 and 108 is evaporated, and the sand molds 106 and 108 are dried.

When performing hot air drying, it is necessary to dry the water without vaporizing the binder that binds the cast sand, so the temperature of the sand mold surface layer is set to about 100 ° C. Therefore, when the sand mold is thick, only the surface layer of the sand mold reaches the drying temperature, and the moisture evaporates only from the surface layer, and the region inside about 100 mm from the surface layer may not be sufficiently dried.
Further, as shown in FIG. 7A, the moisture near the surface layer s of the sand molds 106 and 108 is pushed to the inner area by the wind pressure of the hot air h, and tends to move to the inner area as indicated by the arrows. .

  As a result, the moisture that has not evaporated and moved to the inner region returns to the vicinity of the surface layer simultaneously with the completion of the hot air drying, and this moisture causes gas defects. Usually, hot air drying is performed until just before the casting operation. However, after the hot air drying is completed, it is necessary to remove a hose for feeding the hot air into the sand mold or prepare a dam. Therefore, it takes about one hour from the end of hot air drying to the start of casting operation, and during that time, the moisture in the inner region returns to the vicinity of the surface layer s, as indicated by the arrow in FIG. Therefore, there still remains a problem that moisture remains on the surface of the sand mold and this moisture causes gas defects.

  The thickness of the sand mold varies depending on the shape of the cast product and the mold strength, and is determined from the viewpoint of preventing damage to the casting frame and preventing leakage of molten metal. When the casting is 10 tons or more, a sand mold thickness of 200 mm or more is often required. Moreover, since the thickness of the sand mold that forms the core is determined by the cast product, the thickness of the sand mold cannot always be 100 mm or less.

  There is a method of applying a coating material such as zircon or black smoke powder to the inner surface of the sand mold in order to smooth the casting surface of the cast product and prevent seizure or penetration of the molten metal into the sand mold. In this case, due to the heat of the molten metal at the time of casting, moisture and the like contained in the coating material are decomposed to generate decomposition gas, which causes oxidation of the casting surface, decarburization of the sand mold surface layer, hydrogen embrittlement, etc. May occur. In Patent Document 1, in order to prevent this, a gas absorption getter material made of a single metal such as Zr, Ti, or Hf or an alloy thereof is applied to the surface of the sand mold together with a coating material, and the gas absorption getter material decomposes the gas. A casting mold is disclosed which absorbs the above.

Japanese Patent Laid-Open No. 02-11243

  With the means disclosed in Patent Document 1, it is possible to absorb the cracked gas generated from the coating material with the gas absorption getter material, but it is not possible to remove the water intervening in the inner region of the sand mold. Therefore, the problem cannot be solved.

  The present invention has been made in view of the problems of the prior art, and it is an object of the present invention to reliably remove moisture contained in the inner region of the sand mold and thereby prevent gas defects caused by this moisture.

  To achieve this object, a casting mold according to the present invention includes a casting frame that forms a casting space therein, and a sand mold that is filled in the casting space and has a cavity in which molten metal is injected into an inner portion. Porous adsorption that is attached to the inner surface of the casting mold and placed between the casting mold and the sand mold so as to surround the sand mold from the outside, and in contact with the sand mold throughout the outer surface of the sand mold. The sand mold is formed with a thickness capable of adsorbing moisture contained in the sand mold by the adsorbent over the entire thickness direction of the sand mold.

Thus, the adsorbent is interposed so as to be in contact with the entire outer surface of the sand mold, and moisture existing in the back area of the sand mold away from the surface layer is adsorbed by the adsorbent. As a result, moisture contained in the sand mold can be removed, so that gas defects caused by this moisture can be prevented.
Moreover, the moisture contained in the sand mold can be removed in the entire thickness direction of the sand mold by forming the thickness of the sand mold so that the moisture contained in the sand mold can be adsorbed throughout the thickness direction by the adsorbent. .
As the adsorbent, for example, zeolite, ALC (lightweight foamed concrete material), or the like can be used. These adsorbents have a large number of pores and can adsorb moisture to the pores.

  According to the present invention, the gas defects of the cast product can be reduced, so that the yield of the cast product can be improved, and the work for repairing the gas defect generated in the cast product can be reduced. Moreover, mold | die intensity | strength can be raised by adhere | attaching an adsorbent on the inner surface of a casting frame. Therefore, since the compressive strength of the casting frame can be increased with respect to the static pressure of the molten metal applied to the casting frame when the molten metal is poured, the dimensional accuracy of the cast product can be improved. In addition, since the thickness of the sand mold can be reduced while preventing mold damage and hot water leakage, the amount of casting sand used can be reduced, and the manufacturing cost of the cast product can be reduced.

  In the present invention, it is preferable to use an adsorbent having heat resistance with respect to a temperature of 700 ° C. or lower, such as zeolite or ALC. As a result, the sand mold thickness can be reduced as described above. Therefore, it becomes easy to adsorb moisture contained in the entire thickness direction of the sand mold, and the amount of casting sand used can be reduced, and the cost can be reduced.

  The adsorbent used in the present invention is preferably an adsorbent having a pore diameter of 1 nm or more and 20 nm or less. According to the verification by the present inventors, it has been found that the adsorption performance of the adsorbent having a pore diameter exceeding 20 nm is lowered by the heat of the molten metal. On the other hand, it has been found that an adsorbent having a pore diameter of 1 nm or more and 20 nm or less can maintain the moisture adsorption performance of the adsorbent at a high level even when exposed to the heat of the molten metal, and prevent gas defects.

  The thickness of the sand mold may be not less than the thickness at which the temperature transmitted from the molten metal poured into the cavity to the adsorbent through the sand mold is not more than the heat resistant upper limit temperature of the adsorbent and 120 mm or less. For example, both zeolite and ALC used as adsorbents have good heat resistance, and in the case of zeolite, they have good heat resistance for temperatures of 700 ° C. or lower. For this reason, even if the sand mold thickness is reduced, the heat of the molten metal does not cause deterioration or burning, so the sand mold thickness can be reduced. This facilitates the adsorption of moisture contained in the entire thickness direction of the sand mold, reduces the amount of casting sand used, and reduces the cost.

  In addition, if the sand mold thickness is 120 mm, the temperature of heat transferred from the molten metal to the adsorbent is equal to or lower than the heat-resistant upper limit temperature of a normal adsorbent that can be used in the present invention, so 120 mm is the upper limit of the sand mold thickness. be able to. For example, when the adsorbent is zeolite or ALC, the sand mold thickness can be 80 to 120 mm.

The present invention can also be applied to a mold in which a core is disposed in a casting space. In this case, the core is composed of a sand mold formed of cast sand, an adsorbent embedded in the sand mold, and a reinforcing bar embedded in the adsorbent. And the thickness of the sand mold which forms a core is formed in the thickness which can adsorb | suck the water | moisture content contained in a sand mold by the adsorbent over the whole thickness direction of a sand mold.
Accordingly, moisture contained in the sand mold can be removed in the entire thickness direction of the sand mold, and the strength of the adsorbent can be improved by embedding a reinforcing bar in the adsorbent.

  In addition, the thickness of the sand mold forming the core is not less than the thickness at which the temperature transmitted from the molten metal injected into the cavity to the adsorbent through the sand mold is equal to or lower than the heat-resistant upper limit temperature of the adsorbent. And 120 mm or less. For this reason, even if the sand mold thickness is reduced, the heat of the molten metal does not cause deterioration or burning, so the sand mold thickness can be reduced. This facilitates the adsorption of moisture contained in the entire thickness direction of the sand mold, reduces the amount of casting sand used, and reduces the cost.

  In the present invention, the reinforcing bars used for forming the core may be made of a material having corrosion resistance, or may be subjected to a treatment imparted with corrosion resistance. For example, the reinforcing bar is made of stainless steel, or the surface of the reinforcing bar is coated with a corrosion resistant alloy or a corrosion resistant paint. As a result, the life of the reinforcing bars can be prolonged, so that the adsorbent embedded in the core can be reused and the cost can be reduced.

  According to the present invention, since the gas defects of the cast product can be reduced, the yield of the cast product can be improved, and the work for repairing the gas defect generated in the cast product can be reduced. In addition, by applying an adsorbent to the inner surface of the casting frame, the mold strength can be increased, so that the dimensional accuracy of the cast product can be improved, and the sand mold thickness can be prevented while preventing mold damage and preventing hot water leakage. Therefore, the amount of casting sand used can be reduced, and the manufacturing cost of the cast product can be reduced.

It is a front view sectional view of the casting mold concerning one embodiment of the present invention. It is a perspective view of the reinforcing material containing a reinforcing bar used for the casting mold. (A) shows the component of the zeolite used by the said embodiment, (B) is a chart which similarly shows the characteristic of a zeolite. (A) shows the components of ALC used in the embodiment, and (B) is a chart showing the characteristics of ALC. It is a figure which shows the crystal structure which the said ALC expanded. It is sectional drawing seen from the front which shows the conventional casting mold. In the conventional casting mold, the behavior of moisture contained in the sand mold is shown, (A) is a hot air drying, (B) is a front sectional view showing the behavior after hot air drying.

  Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in this embodiment are not intended to limit the scope of the present invention to that unless otherwise specified.

  An embodiment of the present invention will be described with reference to FIGS. In FIG. 1, a casting mold 10 is disposed on the floor surface F. The casting mold 10 includes an upper mold 12 and a lower mold 14 that are formed separately from each other. Inside the upper mold 12 and the lower mold 14, sand molds 16 and 18 formed using cast sand are arranged. The sand molds 16 and 18 have cavities c1 and c2 formed therein, respectively.

  Cores 20 and 22 are arranged at the centers of the cavities c1 and c2, respectively, and the inner surfaces of the sand molds 16 and 18 and the outer surfaces of the cores 20 and 22 form cavities c1 and c2. Panel members 28 a and 28 b made of a porous adsorbent are provided between the inner surface of the upper mold 12 and the sand mold 16. As a method for attaching the panel members 28a and 28b, first, long bolts 30 are welded to the inner surface of the upper mold 12. A through hole corresponding to the diameter of the long bolt 30 is formed in the panel members 28 a and 28 b, the long bolt 30 is passed through the through hole, and the panel members 28 a and 28 b are applied to the inner surface of the upper mold 12. In this state, the panel members 28 a and 28 b are fixed with the nuts 32.

  In the same manner, the panel members 28c, 28d, 28e, and 28f are attached to the inner surface of the lower mold 14 using the long bolt 30 and the nut 32. Next, the panel material 28g is arranged and fixed on the floor surface F between the panel material 28d and the panel material 28f, and the panel material 28i having a length shorter than the panel material 28g and the panel material 28g on the end side of the upper surface of the panel material 28g. 28k is placed. The panel members 28i and 28k are fixed in a state where the end surface of the panel material 28i is applied to the surface of the panel material 28d and the end surface of the panel material 28k is applied to the surface of the panel material 28f. The sum of the length of the panel material 28i and the length of the panel material 28k is shorter than the length of the panel material 28g. Therefore, a sand filling space can be formed between the end surface of the panel material 28i and the end surface of the panel material 28k.

  Further, a panel material 28h having a length shorter than that of the panel material 28i is placed on the end of the upper surface of the panel material 28i, and a panel material 28j having a length shorter than that of the panel material 28k is placed on the end of the upper surface of the panel material 28k. Place. The panel members 28h and 28j are fixed in a state where the end surface of the panel member 28h hits the surface of the panel member 28d and the end surface of the panel member 28j contacts the surface of the panel member 28f. Thereby, a sand-type filling space can be formed between the end surface of the panel material 28h and the end surface of the panel material 28j.

  The sand mold 16 is formed inside the panel members 28 a and 28 b attached to the upper mold 12, and the sand mold 18 is formed inside the panel members 28 c to 28 j fixed to the lower mold 14. The sand molds 16 and 18 and the panel members are in direct contact with each other. Each panel material is composed of zeolite or ALC having pores. The thickness A of the sand molds 16 and 18 is formed to be about 100 mm throughout the sand mold. The core 20 is composed of a sand mold formed using cast sand. The core 22 is composed of a sand mold 34 formed using cast sand and a reinforcing bar-containing adsorbent 36 embedded in the sand mold 34. The thickness B of the sand mold 34 from the surface of the sand mold 34 to the surface of the adsorbent 36 is also formed to be about 100 mm.

In FIG. 2, the structure of the adsorbent 36 with a reinforcing bar is shown. A large number of reinforcing bars 38 having a small diameter are embedded in the reinforcing material containing reinforcing bars 36. The reinforcing bar 38 is made of stainless steel.
FIG. 3 shows the components and characteristics of zeolite used as the adsorbent in the present embodiment, and FIG. 4 shows the components and characteristics of ALC used as the adsorbent in the present embodiment. FIG. 5 shows an enlarged crystal structure of ALC (magnification 150,000 times). As shown in FIG. 3, the zeolite used in the present embodiment has a pore diameter of 0.55 to 0.8 nm and has stable heat resistance at 700 ° C. Moreover, as shown in FIG. 4, ALC used by this embodiment has a 1-10 nm pore diameter, and has the heat resistance stabilized at 1000 degreeC.

  In such a configuration, a casting operation is performed by injecting molten metal into the cavities c1 and c2. Before that, hot air h is supplied from the hot air dryer 24 to the cavities c1 and c2 via the hose 26. The surface layers of the sand molds 16 and 18 are dried by the hot air h, the water contained in the surface layers is evaporated, and the sand molds 16 and 18 are dried. However, the moisture remaining in the back regions of the sand molds 16 and 18 cannot be removed by hot air drying.

  In the present embodiment, moisture remaining in the entire thickness direction of the sand molds 16 and 18 can be adsorbed by the panel members 28a to 28j, and the moisture can be removed in the entire thickness direction of the sand molds 16 and 18. Therefore, since the gas defects of the cast product generated by the moisture can be reduced, the yield of the cast product can be improved and the work for repairing the gas defects generated in the cast product can be reduced. Moreover, the mold strength can be increased by attaching each panel material to the inner surfaces of the casting frames 12 and 14. As a result, the compressive strength of the casting frames 12 and 14 can be increased with respect to the static pressure of the molten metal applied to the casting frame at the time of pouring the molten metal, so that the dimensional accuracy of the cast product can be improved. In addition, since the thickness of the sand mold can be reduced while preventing mold damage and hot water leakage, the amount of casting sand used can be reduced, and the manufacturing cost of the cast product can be reduced.

  In addition, by setting the thickness of the sand molds 16 and 18 and the sand mold 34 of the core 22 to about 100 mm over the entire area, moisture contained in the sand mold can be removed in the entire thickness direction of the sand mold. At the same time, since the heat of the molten metal transmitted to each panel material can be set to 700 ° C. or less, the adsorbent constituting each panel material is not deteriorated or burned out. Furthermore, since the thickness of the sand mold 16 can be reduced to about 100 mm, the adsorption of moisture contained in the entire thickness direction of the sand mold can be facilitated, and the amount of cast sand used can be reduced and the cost can be reduced.

If the diameter of the pores of zeolite or ALC used as the adsorbent is 1 to 20 nm, the present inventors can maintain the adsorbent moisture adsorption performance even when exposed to the heat of the molten metal, and prevent gas defects. I verified that I can do it. Therefore, in this embodiment, the moisture adsorption performance of each panel material can be maintained high.
Further, since the adsorbent 36 having the reinforcing bar 38 is embedded in the core 22, the strength of the adsorbent 36 can be improved, and the reinforcing bar 38 is made of stainless steel having good corrosion resistance, so the life is prolonged. Therefore, the adsorbent 36 can be reused and the cost can be reduced.

  According to the present invention, it is possible to realize a casting mold capable of reliably removing moisture contained in the sand mold and preventing gas defects.

10,100 Casting mold 12,102 Upper mold 14,104 Lower mold 16,18,34,106,108 Sand mold 20,22,110,112 Core 24,116 Hot air dryer 26,118 Hose 28a-28j Panel material 30 Long bolt 32 Nut 36 Adsorbent 38 Reinforcing bar 114 Core bar F Floor h Hot air c1, c2 Cavity

Claims (6)

In a casting mold having a casting frame that forms a casting space inside, and a sand mold that is filled in the casting space and in which a cavity for injecting molten metal is formed in an inner part,
It is attached to the inner surface of the casting frame, and is disposed between the casting frame and the sand mold so as to surround the sand mold from the outside, and is disposed so as to contact the surface of the sand mold over the entire outer surface of the sand mold. A porous adsorbent,
The casting mold according to claim 1, wherein the sand mold is formed with a thickness capable of adsorbing moisture contained in the sand mold over the entire thickness direction of the sand mold by the adsorbent.   2. The casting mold according to claim 1, wherein the adsorbent has heat resistance with respect to a temperature of 700 ° C. or less and has pores of 1 nm or more and 20 nm or less.   The sand mold has a thickness that is not less than a thickness at which a temperature transmitted from the molten metal poured into the cavity to the adsorbent through the sand mold is not more than a heat resistant upper limit temperature of the adsorbent, and has a thickness of 120 mm or less. The casting mold according to claim 1, wherein the casting mold has a casting mold. A core is disposed in the casting space;
The core is composed of a sand mold formed of cast sand, the adsorbent embedded in the sand mold, and a reinforcing bar embedded in the adsorbent,
The sand mold forming the core is formed to have a thickness capable of adsorbing moisture contained in the sand mold by the adsorbent throughout the entire thickness direction of the sand mold. Casting mold.   The sand mold that forms the core has a thickness that is not less than a thickness at which a temperature transmitted from the molten metal poured into the cavity to the adsorbent is not more than a heat resistant upper limit temperature of the adsorbent, and has a thickness of 120 mm or less. The casting mold according to claim 4, comprising: a casting mold.   6. The casting mold according to claim 4, wherein the reinforcing bars are made of a material having corrosion resistance, or are subjected to a treatment imparting corrosion resistance.