JP2006159255A - Casting method and casting apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain the improvement of mechanical property in a cast product with the miniaturization of crystal grains constituting the cast product by adopting a low-temperature mold having lower than 0°C mold temperature and promoting the solidification of molten metal. <P>SOLUTION: The mold before pouring molten metal, is cooled at ≤-10°C and also, when the molten metal is poured into the mold, while exhausting gas in the inner part of the mold to the outer part, the molten metal is poured into a product-shaped part formed in the mold and solidified to obtain the cast product. Further, a core set to a portion for forming the thick part of the cast product, is cooled at lower temperature by ≥10°C than the other portion in the mold. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a casting method for crystal refinement of a cast product and a casting apparatus for realizing the casting method.

As casting products manufactured by casting have a smaller secondary DAS (dent light arm spacing), the fatigue strength, impact strength, tensile strength, etc. of the casting products increase and the strength of the casting products improves. It will be. Therefore, conventionally, in order to refine the crystal grains of the cast product in casting, the following method has been implemented.
For example, there is a technique of adding an additive to a casting material to refine crystal grains of a cast product. For example, when the cast product is an aluminum alloy, Ti, TiB, Zr, or the like is used as the additive.
Also, the faster the solidification rate of the casting material, the finer the crystal grains and the smaller the secondary DAS. Therefore, the cooling medium is conducted through the entire mold and the conduit formed in the mold, and the mold is forcibly cooled. There is a technique for forcibly promoting the solidification of the crystal to refine the crystal grains of the cast product.

  On the other hand, when the mold is a sand mold, a technique for improving the strength of the mold by freezing moisture contained in the mold is known. For example, the technique described in Patent Document 1. According to this technique, in a sand mold containing 1 to 12% by weight of water, cold air cooled by a refrigerator is circulated in the mold to freeze the mold, thereby improving the strength. Patent Document 1 discloses, as a conventional technique, a method in which a refrigerant is blown through a pipe or the like, or the inside of a mold is circulated by suction, and the refrigerant is circulated into the mold by suction or blowing, or a liquid nitrogen solution. A method for obtaining a frozen mold by immersing a mold therein is disclosed as a conventional mold cooling method.

JP 11-138235 A

The technique of the freezing mold is applied to a sand mold, the cost for an apparatus for freezing the mold is high, and the work procedure is complicated. However, from the viewpoint of improving the quality of the cast product, not from the viewpoint of improving the strength of the casting mold, in view of the technology of the frozen mold, the type of the mold to be frozen is not limited to the sand mold. It can be a mold or the like.
Therefore, in the present invention, the mechanical properties of the cast product are improved by refining the crystal grains constituting the cast product by adopting a low temperature mold in which the mold has a temperature lower than zero degrees Celsius.

  The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described.

  That is, according to the first aspect of the present invention, in the casting method in which the molten metal is poured into the product shape portion formed in the mold and then the molten metal is solidified to obtain a cast product, the mold before the molten metal pouring is cooled to -10 ° C or lower. is there.

  According to a second aspect of the present invention, in the casting method, when the molten metal is poured, the gas inside the mold is discharged to the outside.

  According to claim 3, in the casting method, the core disposed in the portion of the mold before the molten metal pouring that forms the thick portion of the cast product is at a temperature lower by 10 ° C or more than the temperature of the other portion of the mold. It is to be cooled.

  According to a fourth aspect of the present invention, there is provided a casting apparatus comprising: a mold having a product shape portion formed therein; a cooling means for cooling the mold to −10 ° C. or less; and a melt supply means for supplying molten metal to the product shape portion of the mold. is there.

  According to a fifth aspect of the present invention, the casting apparatus includes gas discharge means for discharging the gas inside the mold when the molten metal is supplied to the product shape portion of the mold.

  As effects of the present invention, the following effects can be obtained.

  In Claim 1, the molten metal with which the product-shaped part of the casting_mold | template was solidified can be solidified more rapidly, and a cast product with high intensity | strength can be manufactured. In addition, the temperature of the mold when the molten metal is poured can be maintained at substantially zero degrees C or less, and it is possible to prevent the occurrence of rough skin, pinholes, molten metal blow-back during pouring, etc. caused by the frosting phenomenon. it can.

  According to the second aspect, by discharging the gas inside the mold, it is possible to prevent the occurrence of shrinkage cavities, bubble mixing, and molten metal in the cast product. In addition, the molten metal should be quickly filled into the product shape part of the mold, the hot water will deteriorate, and hot water will be generated, or the solidification gap of the thick part of the product will become large and shrinkage will occur in the thick part. Can be prevented.

  In claim 3, the solidification of the molten metal in the vicinity of the core is promoted, the directivity is given to the solidification of the molten metal, the solidification delay of the thick wall portion is eliminated, and the occurrence of casting defects such as shrinkage cavities is prevented. Can do.

  In Claim 4, the molten metal with which the product shape part of the casting_mold | template was solidified can be solidified more rapidly, and a cast product with high intensity | strength can be manufactured. In addition, the temperature of the mold when the molten metal is poured can be maintained at substantially zero degrees C or less, and it is possible to prevent the occurrence of rough skin, pinholes, molten metal blow-back during pouring, etc. caused by the frosting phenomenon. it can.

  According to the fifth aspect, by discharging the gas inside the mold, it is possible to prevent the occurrence of shrinkage cavities, bubble mixing, and molten metal in the cast product. In addition, the molten metal should be quickly filled into the product shape part of the mold, the hot water will deteriorate, and hot water will be generated, or the solidification gap of the thick part of the product will become large and shrinkage will occur in the thick part. Can be prevented.

Next, embodiments of the invention will be described.
1 is a diagram showing a schematic configuration of a casting apparatus according to an embodiment of the present invention, FIG. 3 is a plan view showing a schematic configuration of a mold according to an embodiment of the present invention, and FIG. 4 is a schematic configuration of a mold having a cooling circuit. FIG. FIG. 5 is a plan view showing a schematic configuration of a mold having a cooling circuit.
FIG. 6 is a cross-sectional view showing the mold near the cylinder bore.
FIG. 7 is a diagram showing the flow of casting.
FIG. 8 is a diagram showing a strength test result between a cast product using the cooling mold according to the present invention and a conventional cast product, and FIG. 9 is a diagram showing a relationship between the mold cooling temperature and the secondary DAS.

First, a casting apparatus according to an embodiment of the present invention will be described.
As shown in FIG. 1, the casting apparatus 30 includes a mold 10 having a product shape portion 17 formed therein, a cooling means 33 for cooling the mold 10, a gas discharge means 32 for discharging the gas inside the mold 10, and a molten metal ( It comprises a molten metal supply means 31 for supplying a molten metal) to the mold 10.

The structure of the mold 10 will be described.
The mold 10 can be any one of a plaster mold, a mold, and a sand mold having a moisture content of 1% by weight or less. The sand mold may be any of a baking mold, cement mold, fresh sand, oil sand, shell mold, furan resin, and the like. The casting product cast by the mold 10 is an aluminum alloy or a magnesium alloy.
An object of the present invention is to improve the mechanical properties of the cast product by refining the crystal grains constituting the cast product by adopting a low temperature mold in which the mold 10 has a temperature lower than zero degrees Celsius.

FIG. 2 shows a schematic configuration of the casting mold 10. However, this invention is not limited to the structure of the casting_mold | template 10 of a present Example, It can apply to the casting_mold | template 10 of various shapes and forms.
The mold 10 mainly includes an upper mold 11 and a lower mold 12. A product shape portion 17 for forming a product shape is formed in the upper mold 11 and the lower mold 12. A pouring gate 13 through which molten metal first passes among the mold 10, The runner 15 that is a passage through which the molten metal is guided and distributed to the cough 16 from the sprue 13, the cough 16 that is a part that introduces the molten metal into the mold 10 that is branched from the runner 15 and has a product shape, and the product shape portion 17. Thus, hollow portions such as the hot metal holding portions 14, 14... That hold the molten metal that fills the voids generated by condensation when the molten metal solidifies are formed. Further, a cooling metal 19 for accelerating the solidification of the molten metal is disposed in the product shape portion 17. The mold 10 is provided with a mold opening / closing means (not shown) and is closed (closed) to form an internal space such as the product shape portion 17 by combining the upper mold 11 and the lower mold 12, 11 and the lower mold | type 12 can be opened (mold opening), and a cast product can be taken out.
In the mold 10 described above, the molten metal supplied from the gate 13 into the mold 10 is poured into the product shape portion 17 through the runner 15. The product shape portion 17 is filled with the molten metal, cooled to solidify the molten metal, and a cast product is formed.

The gas discharge means 32 is for discharging the gas in the product shape portion 17 out of the mold 10 when the molten metal is poured into the product shape portion 17.
By discharging the gas inside the mold 10 with the gas discharging means 32, it is possible to prevent the occurrence of shrinkage nests, bubble mixing, and molten metal in the cast product.
Further, in the present invention, since the mold 10 at the time of pouring the molten metal is at a low temperature, the fluidity of the molten metal is lowered, the hot water is deteriorated and a molten metal is generated, or there is a difference in solidification of the thick part of the product. There is a risk that shrinkage nests may be generated in the thick wall portion. Therefore, by discharging the gas inside the mold 10 with the gas discharging means 32, the product shape portion 17 can be filled quickly into the product shape portion 17 with the low pressure inside the product shape portion 17.

  When the mold 10 is a sand mold or a gypsum mold, the gas discharge means 32 includes a suction plate 20 that communicates with a gap formed inside the mold 10, a discharge pipe 21 that communicates with the suction plate 20, and the discharge pipe 21. And a suction pump 22 that sucks the gas in the discharge pipe 21 and discharges it to the outside. The suction plate 20 is a porous body and is disposed at the lower part of the lower mold 12. The gas contained in the entire mold 10 passes through holes formed in the suction plate 20, and the gas inside the mold 10 passes through the discharge pipe 21. It is discharged outside.

  When the mold 10 is a mold, the gas discharge means 32 includes an exhaust path (not shown) formed in the upper mold 11 or the lower mold 12 so as to communicate with the product shape portion 17, and the exhaust path The exhaust pipe 21 is connected to the exhaust pipe 21. The suction pump 22 is connected to the exhaust pipe 21 and sucks the gas in the exhaust pipe 21 and discharges the gas to the outside. Then, the gas in the product shape portion 17 is discharged to the outside of the mold 10 through the exhaust path and the discharge pipe 21.

  The cooling means 33 is for cooling the whole or part of the mold 10, and various known cooling means 33 for the mold 10 can be employed.

For example, a freezer can be provided in the casting apparatus 30 as the cooling means 33. In this case, a part or all of the mold 10 is put into a freezer, cooled to a predetermined temperature, taken out from the freezer, and molten metal is poured into the mold 10.
Further, for example, the casting apparatus 30 can be provided with a cooling circuit formed in the mold 10 as the cooling means 33 and a refrigerant conducted to the cooling circuit. In this case, as shown in FIGS. 4 and 5, a cooling circuit 18 is formed by a pipe or the like in the mold 10, and the refrigerant is conducted to the cooling circuit 18. Until the pouring of the molten metal is started, the refrigerant is supplied to the cooling circuit 18, and if the pouring of the molten metal is started, the supply of the refrigerant is stopped in order to promote the hot water around the product shape portion 17. Stop cooling.

In addition, the cooling means 33 includes a solvent and a mold conveying device, the mold 10 is immersed in a liquid refrigerant to cool the mold 10, and the cooling means 33 is a solvent and a solvent ejection device. The mold 10 can be cooled by spraying a coolant on the mold 10.
As said refrigerant | coolant, liquid nitrogen, alcohol frozen liquid, etc. are employable. A liquid or gas cooled by a heat exchanger such as a refrigerator can be used as the refrigerant. In addition, if a refrigerator is used, it is not necessary for an operator to work in a bad environment of 0 ° C. or less, and safety and workability can be ensured.

  The molten metal supply means 31 is for pouring molten metal (molten metal) such as an aluminum alloy or a magnesium alloy from the pouring gate 13 of the mold 10 and supplying it to the product shape portion 17. As the molten metal supply means 31, various known molten metal supply means 31 can be employed.

A casting process using the casting apparatus 30 will be described with reference to the flowchart of FIG.
The casting method of the present invention is characterized by using a low-temperature mold of zero ° C. or lower. Therefore, first, the mold 10 before molten metal injection is cooled to −10 ° C. or lower (S10).

When the low-temperature mold comes into contact with a humid atmosphere, supersaturated water vapor rapidly adheres to the mold. When this frosting phenomenon occurs on the product shape portion 17 side in the mold 10, it appears as a phenomenon such as rough skin, pinholes, and molten metal blowback during pouring. In order to reliably prevent the occurrence of such a frosting phenomenon, the upper limit of the cooling temperature of the mold 10 is set to −10 ° C.
After the mold 10 is cooled to a predetermined temperature to form a low temperature mold, before the molten metal is injected into the mold 10, the mold 10 is moved, connected to an apparatus for supplying the molten metal to the mold 10, etc. Work time is required. During this work time, the temperature of the mold 10 rises. However, if the mold 10 is cooled to −10 ° C. or less, even if the temperature of the mold 10 rises, the temperature can be kept below freezing point. Occurrence of sticking phenomenon can be prevented.

  Further, in addition to the above, the mold 10 is in contact with the atmosphere on the upper surface of the upper mold 11 and the upper surface of the gate 13, and the product shape portion 17 side is almost at the temperature if it is a short time of the above operation time Since there is no change and the temperature is kept at −10 ° C. or lower and there is almost no moisture inside the mold 10, a frosting phenomenon does not occur.

The secondary DAS of the crystal grains has a correlation with the temperature. The lower the temperature, the smaller the secondary DAS and the higher the strength of the product. Therefore, it is not necessary to set the lower limit of the cooling temperature of the mold 10 in particular, and the lower limit of the cooling temperature of the mold 10 is set to absolute zero.
However, due to the relationship between the cooling means 33 and the cooling method, when the alcohol refrigerating liquid is used as a refrigerant, the lower limit of the cooling temperature of the mold 10 is about −75 ° C., and when liquid nitrogen is used as the refrigerant, the lower limit of the cooling temperature of the mold 10. Is about -200 ° C. Since the present invention is not limited to the cooling means 33 or the cooling method of the mold 10, the lower limit of the cooling temperature of the mold 10 can be further lowered.

  In the mold 10 cooled as described above, the gas in the mold 10 is discharged to the outside by the gas discharge mechanism (S11). In a state where the gas discharge is continued, the molten metal is supplied to the mold 10 from the gate 13 (S12). The molten metal filling process is completed as quickly as possible. When the product shape portion 17 of the mold 10 is filled with molten metal and the time (die time) for the molten metal to solidify elapses (S13), the mold is opened and the cast product is taken out (S14), and the one-cycle casting process is completed.

  When the core is provided in the mold 10, the mold 10 and the core can be cooled to substantially the same temperature, but the temperature difference between the core provided in the thick part and the other part of the mold 10 is particularly high. Is preferably provided.

  In the thick part, the solidification of the molten metal tends to be slower than in other parts. If solidification of the molten metal is delayed, casting defects such as shrinkage will occur. Therefore, the core disposed in the thick portion is set to a lower temperature than the other portions of the mold 10, the solidification of the molten metal near the core is promoted, and directivity is given to the solidification of the molten metal. This eliminates the solidification delay and prevents the occurrence of casting defects such as shrinkage. In addition, since the solidification delay of a thick-walled part can be eliminated also by using many cooling gold | metal | money (chill), it is preferable to use together.

  The core having a lower temperature than the other part of the mold 10 has a temperature difference of at least −10 to −20 ° C. from the other part of the mold 10. However, since the directivity increases as the temperature difference between the core and the other part of the mold 10 increases, it is preferable.

  The core is cooled by, for example, cooling the removable core separately from the other parts of the mold 10 and attaching the core to the mold 10 before pouring the molten metal, or forming a cooling circuit in the core. There is a method of conducting a refrigerant having a temperature different from that of the cooling circuit formed in the other part of the mold 10. However, the cooling method of the core is not limited to the present embodiment, and a cooling method of the mold 10 that is widely used in general can be adopted.

  FIG. 6 shows a mold made up of an upper mold 11 and a lower mold 12 of the cylinder bore portion of the cylinder, inserts K · K..., Cores N · N. In order to promote the solidification of the molten metal, a cooling metal 19 is arranged. When many cores NN are assembled to the mold 10 like the cylinder mold 10, the temperature of the mold 10 rises during the work time for assembling the cores NN. Since the frosting phenomenon may occur, it is preferable to cool the mold 10 in a state where the cores N, N.

  8 and 9, the mold 10 is cooled to about −20 ° C. in the freezer, the core provided in the mold 10 is cooled to −40 ° C., and the core is attached to the mold 10. An example of a result obtained by pouring molten metal to produce a cast product is shown.

As shown in the graph of FIG. 9, the secondary DAS of the cast product by the low temperature mold is 20 μm or less as compared with the value (40 to 50 μm) of the secondary DAS of the cast product cast by the normal mold 10. And became much smaller. That is, it can be seen that by using the cooling mold 10 according to the present invention, the refinement of the crystal of the cast product is realized.
Further, as shown in the graph of FIG. 8, the tensile strength of the cast product by the low temperature mold was improved by 25% and the elongation strength was improved by 50% or more as compared with the cast product cast by the normal mold 10. That is, it can be seen that the mechanical properties of the cast product are greatly improved by using the cooling mold 10 according to the present invention.
In order to accelerate the solidification of the molten metal in the thick-walled part, chilled metal was used, but no condensation occurred on the surface of the chilled metal, and casting defects such as blow (blowhole) were also observed. There wasn't. From this, it can be seen that the occurrence of casting defects due to the frosting phenomenon could be prevented.

  As described above, the casting using the low-temperature mold of the present invention greatly improves the mechanical properties of the cast product. Therefore, casting that requires high strength such as a product racing engine, aircraft, military parts, etc. It becomes possible to further improve the strength of the product.

The figure which shows schematic structure of the casting apparatus which concerns on the Example of this invention. Side surface sectional drawing which shows schematic structure of the casting_mold | template which concerns on the Example of this invention. The top view which shows schematic structure of the casting_mold | template which concerns on the Example of this invention. Side surface sectional drawing which shows schematic structure of the casting_mold | template provided with the cooling circuit. The top view which shows schematic structure of the casting_mold | template provided with the cooling circuit. Sectional drawing which shows the casting_mold | template near a cylinder bore part. The figure which shows the flow of casting. The figure which shows the strength test result of the casting product using the cooling mold which concerns on this invention, and the conventional casting product. The figure which shows the relationship between casting_mold | template cooling temperature and secondary DAS.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Mold 11 Upper mold 12 Lower mold 17 Product shape part 18 Cooling circuit 20 Suction plate 21 Discharge pipe 22 Suction pump 30 Casting apparatus 31 Molten metal supply means 32 Gas discharge means 33 Cooling means

Claims (5)

In the casting method to obtain a cast product by pouring the molten metal into the product shape part formed in the mold and then solidifying the molten metal,
A casting method characterized by cooling a mold before molten metal pouring to -10 ° C or lower. In the casting method,
When pouring molten metal, the gas inside the mold is discharged to the outside.
The casting method according to claim 1. In the casting method,
Cooling the core disposed in the part of the casting mold before the molten metal pouring is 10 ° C. or more lower than the temperature of the other part of the casting mold,
The casting method according to claim 1 or 2. A mold with a product shape part formed inside,
Cooling means for cooling the mold to −10 ° C. or lower;
A casting apparatus comprising melt supply means for supplying the melt to the product shape part of the mold. In the casting apparatus,
When supplying the molten metal to the product shape part of the mold, equipped with a gas discharge means for discharging the gas inside the mold,
The casting apparatus according to claim 4.