JP4076541B2 - Casting manufacturing method using chiller - Google Patents

Description

  The present invention relates to a method of manufacturing a casting that prevents shrinkage and densifies the structure by the cooling effect of a cooling metal installed in a mold.

The chiller is often used as one of means for preventing the casting from being pulled, like the hot water. While the hot water replenishes the molten metal that is insufficient as it solidifies to prevent the formation of shrinkage cavities, the chiller removes heat from the high temperature part of the casting to make the cooling rate uniform, Prevent occurrence. In addition, the cooling metal is also used for refining the structure of a cast product. Generally, a material of good heat conductivity such as cast iron, cast steel, copper, and graphite is used as a material for the chill metal, and it is installed in a state where it is in contact with or separated from a thick part of the casting where shrinkage cavities are likely to occur. For example, there are a method of using a cooling metal as a core for the thick part (Patent Document 1) and a method of casting into a sand mold having a direct cooling metal of 30% or more of the casting volume (Patent Document 2).
JP-A-10-263794 JP2002-292453

  However, depending on the casting to be cast, there is a case where a cooling metal having a required size cannot be installed due to restrictions on the shape and the like. For example, in a place such as a core surrounded by a casting, the chiller that can be embedded is inevitably limited in size. In such a case, since the chiller receives more heat than the volume, the temperature rises and the cooling ability as the chiller may decrease. As a result, the effect of the cooling metal that removes heat from the molten metal is weakened, and shrinkage cavities and the like may occur in the casting. In addition, when cast iron, cast steel, copper, or the like is used for the chill metal, the chill metal may even be melted by the heat from the molten metal.

  Therefore, conventionally, some cooling metal is kept air-cooled by passing it outside the mold, or water cooling using water vaporization heat, etc. is used to keep the cooling power high by preventing the temperature rise of the metal. (Japanese Patent Laid-Open No. 2001-179392), all of the effects were insufficient, and the installation and handling of the cooling metal was inconvenient.

  In the present invention, in order to solve the above-mentioned problem, a cooling metal made of a material having a good thermal conductivity having a thermal conductivity of 0.06 cal / cm · s · ° C. or higher is connected to a casting. In order not to warm up until the solidification, keep the heat conduction material block whose thermal conductivity at room temperature is 0.3 to 2 times that of chilled metal so that it does not come into contact with the melt. Connect to both ends of chiller. That is, by extending both ends of the cooling metal into the foundry sand and connecting this end to the heat conduction block for cooling the gold, the amount of heat absorbed by the cooling metal is transferred to the heat conduction material block, and the cooling metal itself Try to prevent the temperature from rising. In addition, since thermal conductivity changes with temperature, the thermal conductivity at normal temperature was used as a reference.

  The reason for connecting the heat conductive material block to both ends of the chill metal is to increase the cooling capacity of the chill metal, but if the heat conductive material block is connected to only one side, the final solidified part where shrinkage nests occur is on the opposite side of the block It was because it was discovered that it was not possible to eliminate the shrinkage nest only by moving to.

  It was also discovered that if the thermal conductivity of the heat conducting material block is too good, the block itself becomes too warm and the effect of cooling the cooling metal is lost. In other words, when the temperature gradient between the block and the chiller disappears, the cooling effect of the chiller decreases rapidly, and the effect of the chiller disappears. For this reason, it discovered that the heat conductivity of the heat conductive material block at normal temperature must be 0.3 to 2 times that of the chill metal.

  The chill metal connected to the casting has better thermal conductivity if it is in direct contact with the molten metal, but there is a problem that the chill metal cannot react with the molten metal and cannot be removed. In order to solve this problem, the material of the cooling metal was graphite or a graphite-based mixture. As a result, the chiller and the molten metal can be directly connected, and thermal diffusion becomes easy. However, a refractory material such as a coating mold may be applied around the metal chiller without using a graphite chiller.

  There is no problem as long as the material of the heat conductive material block connected to both ends of the chiller is graphite, graphite-based mixture, iron-based metal, copper-based metal, or aluminum-based metal. However, if the heat conduction material block is made of pure copper, for example, the heat conductivity is too good and the block warms up too quickly, eliminating the temperature difference between the cooling metal and the block, resulting in the cooling effect of the cooling metal being lost. discovered. As a result of various experiments, it was discovered that the thermal conductivity of the block at room temperature must be 0.3 to 2 times that of chilled gold.

  As a result of investigating the reactivity with the molten metal, workability, and the cooling effect of the heat conduction material block, the effective combination of the cooling metal and the heat conduction material block uses graphite for the cooling metal, and the heat conduction material block is iron-based. It has been found that using metal.

  The cooling metal installed in the vicinity of the casting receives the heat of the molten metal at the time of pouring, and the temperature of the cooling metal itself rises. Therefore, the temperature difference from the casting becomes small with time, and the cooling effect decreases. In particular, when only a small chiller can be connected due to restrictions on the shape of the casting, the cooling ability of the chiller is not sufficient, which may cause shrinkage. Therefore, in such a case, a heat conducting material block that is installed in the same mold at both ends of the cooling metal but is not in direct contact with the molten metal is connected, and the heat received by the cooling metal from the molten metal is transferred to this block. . When the heat conductive material block is in direct contact with the molten metal, the heat of the molten metal heats the block itself, and the effect of cooling the cooling metal is lost. By connecting the block for cooling the chill metal to the chill metal, the cooling ability of the chill metal is maintained and the temperature rise is hindered, so that the densification of the tissue and the occurrence of shrinkage can be prevented.

  For the cooling metal for cooling the casting and the heat conductive material block connected thereto, a material having a thermal conductivity of 0.06 cal / cm · s · ° C. or higher at normal temperature is used. When the heat conductivity of the cooling metal block and the heat conducting material block connected to the cooling metal is 0.06 cal / cm · s · ° C. or less, the amount of heat transferred between the molten metal and the cooling metal, or between the cooling metal and the heat conducting material block. Is too slow. As a result, the cooling metal is warmed, and the cooling effect necessary for preventing the densification of the cast structure and the generation of shrinkage cavities cannot be obtained.

  For the heat conductive material block to be connected to the chiller, a material having a thermal conductivity at room temperature of 0.3 to 2 times that of the chiller is used. If the thermal conductivity of the heat conduction material block is too high, the heat transfer from the chiller is fast, so the temperature of the block rises immediately, there is no temperature difference between the chiller and the block, and the block cools the chiller The effect will be weakened. On the other hand, in the case where the thermal conductivity of the heat conducting material block at room temperature is 0.3 to 2 times that of the chilled metal, the temperature difference between the block and the chilled metal becomes sufficiently large. The effect can last for a long time until the end of solidification. As a result, the cooling effect of the cooling metal is always maintained, and it is possible to prevent the formation of shrinkage cavities in the cast product.

  It is important that the heat conducting material block for the chiller is connected to both ends of the chiller. When the heat conduction material block is connected to only one end of the chill metal, the flow of heat from the chill metal to the block is only in one direction, and the heat quantity of the entire chill metal cannot be smoothly transferred to the heat transfer material block. . On the other hand, when the heat conduction material block is connected to both ends of the chiller, the heat flow from the chiller toward this block is dispersed in two directions, so the heat transfer material connected to the chiller and both ends thereof. The heat transfer between the blocks proceeds smoothly and the cooling effect of the cooling metal is maintained.

  As described above, when the heat conducting material block is connected to both ends of the cooling metal, the flow of heat from the cooling metal toward the heat conducting material block is dispersed in two directions, which has an effect of increasing the cooling efficiency. The feature of the present invention is that not only the cooling efficiency effect but also the effect of preventing the shrinkage nest by dividing the final solidified portion concentrated in one place into two. When the heat conducting material block is connected to only one side of the cooling metal, the final solidified portion only moves in the direction opposite to the block at one end, and the final solidified portion cannot be divided into two. By connecting the blocks to both ends of the chiller, the final solidified part can be divided into two. As a result, shrinkage nests can be prevented from occurring.

  According to the casting method using the cooling metal of the present invention, the amount of heat received by the cooling metal from the molten metal is released to the heat conductive material block, thereby preventing the temperature increase of the cooling metal itself and continuously cooling the casting. Therefore, a good casting without shrinkage can be formed.

  Since the chill metal is continuously cooled by the heat conductive material block, the cooling effect can be sufficiently exhibited even if the chill metal itself is small. For this reason, conventionally, a large cooling metal cannot be installed on the product due to the shape factor of the casting, and even a casting that cannot be sufficiently cooled can be efficiently cooled with a small cooling metal.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on a specific Example, this invention is not limited to these Examples.

  FIG. 1 shows an embodiment of a casting method according to the present invention.

  As shown in FIG. 1, the casting mold 1 has a casting frame 3 filled with casting sand 3, and a space (cavity) 4 having a casting shape is formed in the casting sand 3. A runway 6 from the gate 5 communicates with the cavity 4, and a hole 4 a is formed in the center of the cavity 4 so as to vertically penetrate the thick portion due to the shape of the cast product. In this hole 4a, a cooling metal 7 having a thermal conductivity of 0.06 cal / cm · s · ° C. or more is embedded and connected to the inner wall surface, and heat conductive material blocks 8 and 9 are provided at both ends of the cooling metal 7 respectively. And embedded so as not to be connected to the cavity 4. The heat conductive material blocks 8 and 9 are made of a material whose thermal conductivity at normal temperature is 0.3 to 2 times that of the chilled gold 7. The cavity 4 may be a disappearable model.

  When the molten metal is poured from the spout 5, it passes through the runner 6 and fills the inside of the cavity 4. At this time, on the inner wall surface of the hole 4a in which the cooling metal 7 is installed, the molten metal is cooled by the cooling metal 7 earlier than other portions. However, since the portion of the hole 4a in which the cooling metal 7 is installed is thick, the cooling metal 7 alone is not sufficient in cooling effect and a shrinkage nest is generated. In the present invention, since the heat conductive material blocks 8 and 9 are connected to both ends of the cooling metal 7, the heat of the cooling metal 7 moves to the blocks 8 and 9, and the temperature of the cooling metal 7 raised by pouring is lowered. To do. Therefore, the effect | action in which the cooling metal 7 absorbs the heat of a molten metal continues, and generation | occurrence | production of a shrinkage nest can be prevented by the high cooling effect of the cooling metal 7.

  Next, as a casting experiment up to the present invention, an example of a casting experiment performed by changing the connection method of the cooling metal and the heat conductive material block is shown.

  In the experiment, as shown in FIG. 2, a cavity 4 having a cube of 300 mm on a side and a hole 4 a having a diameter of 50 mm penetrating vertically through the center of the upper and lower surfaces is formed in the mold, and the thermometer 10 is formed in the portion of the hole 4 a. It was installed so that the surface temperature of the cast product could be measured. The cooling metal 7 was a graphite rod having a diameter of 50 mm, and was passed through the hole 4 a so as to protrude by 50 mm from the upper and lower surfaces. Each of the heat conductive material blocks 8 and 9 was cast iron having a weight of about 30 kg, and was installed so as to be connected to one side 7a or both sides 7a and 7b of the cooling metal 7 protruding from the upper and lower surfaces of the cavity 4. In the experiment, a molten alloy ductile was cast into this mold, the temperature transition of the cast product after casting was compared, and the presence or absence of shrinkage cavities generated inside was investigated. In addition, solidification analysis was performed for each experiment together to ensure consistency with the experimental results.

For the combination of chiller and heat conductive material block,
A: When no cooling metal is installed (when there is no 7, 8, 9 in FIG. 2)
B: When only the cooling metal is installed (when there is no 8, 9 in FIG. 2)
C: When the block is connected to only one end of the cooling metal (when there is no 9 in FIG. 2)
D: When a block is connected to both ends of the chiller (shown in FIG. 2)
At this time, the volume of one block connected by C was the same as that of two blocks connected by D.

  The temperature measurement result of the cast product is shown in FIG.

  From FIG. 3, when cooling metal is not used, when A or only cooling metal is installed, when C is combined with a heat conduction material block, both C and D are cooled faster. I understand that. Further, in the combination of the cooling metal and the heat conducting material block, the cooling rate is significantly faster when the block is connected to both ends than when the block is connected to only one end of the cooling metal.

  Table 1 shows the condition of the shrinkage cavity inside the cast product, and FIG. 4 shows the result of solidification analysis.

表１から分かるように、鋳造品内部に引け巣の発生が認められなかったのは、冷やし金の両端にブロックを連結した場合Ｄだけであり、それ以外の場合には引け巣の発生が認められた。これは凝固解析の結果と概ね一致する結果となった。

As can be seen from Table 1, the formation of shrinkage cavities was not observed inside the cast product only when the block was connected to both ends of the cooling metal, and in other cases the formation of shrinkage cavities was observed. It was. This was almost the same as the result of solidification analysis.

  As shown in the solidification analysis result of FIG. 4, when the chiller is not connected (a) or when only the chiller 22 is connected (b), a shrinkage nest is generated near the surface of the hole that is the center of the casting. There is a final coagulation part 21 that When the heat conductive material block 23 is connected to only one end of the chiller 22 (c), the final solidified portion 21 moves to the side where the block is not connected in the height direction, but the change in the lateral direction is slight. And hardly moved from near the surface of the hole. On the other hand, when the heat conductive material block 23 is connected to both ends of the chiller 22 (d), the final solidified portion 21 does not change in the height direction, but changes greatly in the horizontal direction. It moves greatly outward from the vicinity of the surface. In addition, the size of the final solidified portion 21 that has moved is smaller than in other cases (a), (b), and (c), and it can be seen that the possibility of shrinkage nests is extremely small. From this result, it can be seen that when the heat conducting material block 23 is connected to the cooling metal 22 for cooling, it is effective to connect the block 23 to both ends of the cooling metal 22.

  Next, an example of a casting experiment performed by changing the material of the heat conductive material block connected to both ends of the chiller will be described.

  In the experiment, as shown in FIG. 2, a cavity 4 having a cube with a side of 300 mm and a hole 4 a having a diameter of 50 mm penetrating the center of the upper and lower surfaces is formed in the mold, and the thermometer 10 is formed at the portion of the hole 4 a. It was installed so that the surface temperature of the cast product could be measured. The cooling metal 7 was a graphite rod having a diameter of 50 mm, and was passed through the hole 4 a so as to protrude 50 mm from the upper and lower surfaces, and the heat conductive material blocks 8 and 9 were connected to both ends thereof. In the experiment, a molten alloy ductile was cast into this mold, the temperature transition of the cast product after casting was compared, and the presence or absence of shrinkage cavities generated inside was investigated. In addition, solidification analysis was performed for each experiment together to ensure consistency with the experimental results.

The following three types of heat conductive material blocks were connected to both ends of the chiller.
A: Graphite block (room temperature thermal conductivity 0.31 cal / cm · s · ° C., weight
About 8kg / piece)
B: Cast iron block (room temperature thermal conductivity 0.18 cal / cm · s · ° C., weight
About 30kg / piece)
C: Copper block (normal thermal conductivity 0.95 cal / cm · s · ° C, weight approx.
40kg / piece)
At this time, the blocks of each material had the same volume.

  The temperature measurement result of the cast product is shown in FIG.

図５から、鋳鉄製ブロックの場合Ｂが最も温度低下が速く、次いで黒鉛製ブロックＢ、銅製ブロックＣの順になっていることが分かる。また、表２に示したように、冷やし金の両端に銅製ブロックを連結した場合Ｃには引け巣の発生が認められたが、黒鉛製ブロックと鋳鉄製ブロックの場合Ｂ、Ａには引け巣の発生は認められなかった。

FIG. 5 shows that in the case of a cast iron block, B has the fastest temperature drop, followed by graphite block B and copper block C in this order. In addition, as shown in Table 2, when a copper block was connected to both ends of the cooling metal, shrinkage nests were observed in C, but in the case of graphite blocks and cast iron blocks, B and A were shrinkage nests. The occurrence of was not observed.

  Table 3 shows the thermal conductivity of each thermal conductive material block used in the experiment.

各材質の熱伝導率を比べると、銅が０．９５ｃａｌ／ｃｍ・ｓ・℃と最も高く、次いで黒鉛が０．３１ｃａｌ／ｃｍ・ｓ・℃、鋳鉄が０．１８ｃａｌ／ｃｍ・ｓ・℃となっている。

Comparing the thermal conductivity of each material, copper is the highest at 0.95 cal / cm · s · ° C., followed by graphite at 0.31 cal / cm · s · ° C. and cast iron at 0.18 cal / cm · s · ° C. It has become.

  From FIG. 5 and Table 3, it can be seen that the cooling of the cast product becomes slower as the cooling metal is combined with the block having high thermal conductivity. This is because using a block with higher thermal conductivity than chilled metal, the heat transfer from the chilled metal is fast and the block itself warms up quickly, so the ability to cool the chilled metal can only be maintained for a short time. There is.

  The result of the coagulation analysis is shown in FIG.

  From FIG. 6, when the position of the final solidified portion where the shrinkage cavity is generated is compared, the case where the final solidified portion 21 is farthest from the center of the cast product is the case (b) where the cast iron block 23 is used, and then graphite. The order is (a) when the block 24 is used, and (c) when the copper block 25 is used. In particular, when the copper block 25 is used (c), it can be seen that the final solidified portion 21 has hardly moved from the center of the cast product. This result is in good agreement with the result of the casting experiment.

  From FIG. 5 and FIG. 6, the block material connected to both ends of the chiller uses a material having a lower thermal conductivity than the chiller, so that the temperature difference from the chiller is sufficiently large, and the cooling effect of the chiller is solidified It can last for a long time until the end. Thus, it can be seen that the cooling effect of the cooling metal is always maintained, and it is possible to prevent the formation of shrinkage cavities in the cast product. However, the heat conductive material block connected to the chiller does not necessarily need to have a lower thermal conductivity than the chiller, and may be a material whose thermal conductivity at room temperature is 0.3 to 2 times that of the chiller.

It is sectional drawing of the casting_mold | template for enforcing one Embodiment of the manufacturing method of the casting by this invention. It is sectional drawing of the casting_mold | template for the casting experiment until it reaches this invention. It is a graph which shows the experimental result which shows the cooling effect of a heat conductive material block. (A), (b), (c), (d) is sectional drawing of the casting which compares the experimental result using the cooling method in this invention. It is a graph which shows the experimental result conducted by changing the material of the heat conductive material block combined with a chiller. (A), (b), (c) is sectional drawing of the casting which compares the experimental result performed by changing the material of a heat conductive material block in the cooling method in this invention.

Explanation of symbols

1 Mold
2 Cast frame
3 Foundry sand
4 Cast product shape
5 entrance
6 Runway 7 Cooling metal 8, 9 Heat conduction material block 10 Thermometer 21 Final solidification part 22 Cooling metal (graphite)
23 Cast iron block 24 Graphite block 25 Copper block

Claims (5)

  A chiller having a thermal conductivity of 0.06 cal / cm · s · ° C. or more is placed in direct contact with or close to the molten metal in the mold, and heat conduction at normal temperature is performed at both ends of the chiller. A method for producing a casting, characterized in that a heat conductive material block having a rate of 0.3 to 2 times that of the chilling metal is connected so as not to contact the molten metal.   The chiller is made of graphite or a graphite-based mixture, and the heat conductive material block is made of graphite, a graphite-based mixture, an iron-based metal, a copper-based metal, or an aluminum-based metal. A method for producing a casting according to 1.   The casting manufacturing method according to claim 1 or 2, wherein the periphery of the cooling metal is coated with a heat-resistant coating.   The method for producing a casting according to any one of claims 1 to 3, wherein the heat conductive material block is made of any one of an iron-based metal and a graphite-based mixture.   The method for manufacturing a casting according to claim 1, wherein the cooling metal is made of graphite or a graphite-based mixture, and the heat conductive material block is made of an iron-based metal.

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