JPH06154996A - Cast product having cooling hole and casting method thereof - Google Patents

Abstract

PURPOSE:To make filling of sand, etc., in the inner part and taking-out of the sand after casting unnecessary by growing dendritic structure from the cast product surface and tubular worked product surface to the inside, in the cast product having cooling hole produced by insert-casting the tubular worked product in molten metal. CONSTITUTION:This cast product is the one having the cooling hole made by executing the insert casting with the molten metal outside the tubular worked product A formed so as to pass the fluid through the inner part. Both of this tubular worked product A and the molten metal are iron-base alloy and after casting, the both are melted at a part of the interface or the whole surface. Further, the dendritic structure is extended from the cast product surface to the inside of the worked surface after finish-working just under the surface of the cast product and the cooling hole with the dendritic structure extended from the surface of the tubular worked product is obtd. By this method, the product having excellent quality and sufficiently melted with the molten metal can be manufactured and further, this cast product is the excellent one having close casting structure at the circum ferential part of the pipe and finished surface or the just under part thereof and sound quality.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a die for low pressure casting, die casting, etc., and a casting for general use having not only a die but also a cooling hole through which a cooling medium flows, and a casting thereof. The present invention relates to a manufacturing method.

[0002]

2. Description of the Related Art A cooling hole through which a cooling medium flows is provided in a die, and the die is cooled while being used for die casting, low pressure casting, etc., to prevent coarsening of the structure of the cast product or prevention of strength reduction. Various methods have been studied so far.
Taking low-pressure casting as an example, it is as follows. Low-pressure casting is a device in which an upper and lower opening / closing mechanism is provided on a closed type heat-retaining furnace that houses molten metal, a mold is attached to this, and the mold cavity and the molten metal are connected by a molten metal supply pipe called stalk. It is a casting method that repeats a casting cycle consisting of mold clamping, molten metal pressure filling, holding and solidification, molten metal pressure release, mold opening, and casting removal. The pressure applied to the molten metal is slightly higher than the atmospheric pressure, and the molten metal contained in the closed heat insulation furnace is filled into the cavity from the die gate through the stalk and the sub-lyzer. However, since the casting cycle is usually about 5 to 7 minutes instead of a short time like die casting, it is likely that the mold, especially the sub-riser, is easily cooled, which may cause defective casting and other casting defects. ing.

On the other hand, regarding the state of holding and solidifying the molten metal during the casting cycle and the state of the molten metal at the sprue at the time when the molten metal pressure is released, the sublizer side is in a molten state, while the mold cavity side (product side) is in a solidified state. Is preferred. However, the sub-riser side is likely to solidify for a relatively long time as described above, and once solidified, the solidification layer may progress from the sub-riser to the stalk, and the casting operation must be interrupted unexpectedly. Occurs. For this reason, generally, the sub-riser portion is heated by a heating means such as a burner, but on the other hand, the heating raises the temperature to the lower die portion constituting the die. Therefore, in the cavity portion in contact with the lower portion, the product structure particularly near the sprue is coarsened, and adverse effects such as strength reduction and toughness deterioration of the cast product occur. Therefore, as a lower cooling means, there is one in which a die is provided with a cooling hole or a cavity for flowing a cooling medium to perform forced air cooling. Also, by providing this cooling hole, it becomes possible to improve the casting cycle.

Conventionally, as means for providing such cooling holes, in addition to the usual method of making holes in a die by machining such as drilling, as disclosed in Japanese Patent Laid-Open No. 53-21041, It is known that the mold is divided into holes, not holes, and cooling holes are formed when the molds are combined. The method of making holes by machining is a very labor-intensive method, and substantially this means cannot be taken when it is desired to arrange cooling holes having a complicated shape. Further, although the method of forming the mold in a divided shape can provide cooling holes having a complicated shape relatively easily, it also requires a large number of steps.

[0005]

An integrated manufacturing method, which is not divided, is a method proposed in Japanese Patent Laid-Open No. 64-2759, that is, a tubular body (hereinafter A pipe-shaped processed product is cast from the outside, and a thermosetting resin is sprinkled inside the pipe in order to prevent deformation such as deformation and melting damage during pipe casting. After filling with sand, it is known to harden the sand to reinforce the pipe. However, with this method, the structure around the pipe is not sufficiently dense, the reinforcing effect of the pipe is small, and if the pipe shape becomes complicated, it is difficult to sufficiently fill the pipe with sand covered with a thermosetting resin. Further, the present inventors have found that the insufficiently filled portion due to this is likely to be deformed or damaged during casting, and it is difficult to remove the hardened sand after casting. The pipe should be provided directly below the work surface of the mold or the like from the viewpoint of effective cooling, but a sufficient distance is required from the viewpoint of strength due to the hollow. If it is possible to form a dense and sound casting structure around the cooling holes,
It is advantageous in both of the above strength and heat conduction. The present invention is
A casting having a cooling hole in which a pipe and its peripheral portion have a dense and sound casting structure, and a method of manufacturing a casting having a cooling hole which solves the drawbacks of the method of filling sand covered with the thermosetting resin The purpose is to provide cast products with excellent quality.

[0006]

As a result of various studies to solve the above-mentioned problems, the inventors of the present invention have found that a suitable cooling medium is provided inside the tubular product for the deformation and breakage of the pipe. By allowing it to flow through and cooling the pipe, it can be avoided by keeping the tubular body processed product at a temperature that can sufficiently withstand the heat-melting action and impact pressure of cast metal, and the pipe periphery is dense and sound. It has been found that it is possible to obtain a good casting structure. That is, first of all, the method invention of the present application has a cooling hole in which a tubular body processed product formed so that a fluid flows through inside is installed in a mold, and the tubular body processed product is cast from the outside by gurgle casting. In the casting method for casting, the tubular body processed product and the molten metal are both iron-based alloys, and a cooling medium is flown through the tubular body processed product at least for a predetermined period after the start of pouring. It is a casting method of a cast product having holes. In the present invention, it is desirable to use gas as the cooling medium, to use mild steel or stainless steel as the material for the tubular body, and to use a chill in combination.

Next, the first cast product according to the present invention is a cast product having a cooling hole which is obtained by casting a molded tubular product from the outside so that a fluid flows through the inside of the cast product. Both the tubular body processed product and the molten metal are iron-based alloys, and after casting, the two are fused at a part or the whole of the interface, and the dendrite-like structure is formed from the surface of the cast product immediately below the finishing work. A cast product having cooling holes, which is characterized in that it has grown to the inside of the working surface of the mold and from the surface of the tubular product processed product. In addition, in the through-flow passage of the cooling medium, a portion whose cross-sectional area is enlarged in the shape of a cavity or a portion branched from the flow passage into a blind alley is often actually required. On the other hand, it is desirable to provide a baffle. That is, the second cast product of the present application is a cast product having a cooling hole formed by casting a molded tubular product from the outside as if the fluid flows through the inside of the cast product. The hole is a cast product having a cooling hole characterized by having a baffle in a part thereof.

[0008]

According to the present invention, the temperature of the tubular body processed product during casting is maintained in an appropriate temperature range by allowing a cooling medium to flow through the inside thereof, thereby maintaining its strength. It promotes the development of dendrites around the body-worked product, and makes the structure dense and healthy. Therefore, there is no need to fill the inside with sand or the like and to take it out after casting, which is also advantageous in terms of strength and heat transfer. The cooling effect during casting by the cooling medium can be indirectly known, for example, by measuring the temperature at the outlet of the cooling medium, which allows the outer surface of the tubular body processed product to be appropriately poured with the pouring metal. It is possible to control the degree of fusion. When gas is used as the cooling medium, the cooling effect is moderately slow, and the cooling effect can be controlled in a wide range by changing the pressure or flow rate. This makes it easier to obtain a cast product in which the outer surface of the tubular body is fused, and the heat resistance during use is small (the cooling effect is large) because it is dense and sound (cooling effect is large), and the cooling hole is also advantageous in strength. Become. Also, it is convenient in terms of work safety.

As a gas that flows through the pipe during casting, an inert gas such as nitrogen or argon is generally used. And
By flowing these gases, the pipe is deformed by the molten metal during casting, and the molten metal flows into the pipe due to pipe damage,
Further, it exerts the effect of preventing the oxidation of the pipe heated by the molten metal. In particular, when the cast product is an article that uses the outer surface such as a mold, install a chill plate having an appropriate weight equal to or greater than the product weight, corresponding to the portion to be the work surface after finishing. It is important to enhance the cooling from the wall surface of the mold. As a result, due to the cooling effect from the tubular body processed product and the cooling effect of this chill, etc.,
By controlling the direction of dendrite growth, it is possible to prevent the occurrence of pit-like defects generated at the intersection of the solidification tips with the progress of solidification, or to control the position thereof.

The present invention will be described in more detail below. The pipe for forming the cooling hole is processed and assembled into a shape in which a desired cooling hole is formed in the mold by combining a straight pipe with means such as bending and welding. Since it is required that the material of the tubular body processed product is less likely to melt after casting, it is advantageous in casting that it is made of mild steel having a high melting point, and if it is made of stainless steel, its chemical It is advantageous in use of cast products because of its stability. The specifications of the route, thickness, wall thickness, etc. are appropriately selected depending on the shape, size, etc. of the mold.

According to the present invention, by allowing the cooling medium to flow through the processed product of the tubular body, the dendrite growth from the processed product is likely to be faster than the dendrite growth from the mold surface.
Therefore, as shown in FIG. 3, pit-like defects generated at the solidified tip crossing portion are likely to occur near the casting surface. Since the normal machining allowance is 3 mm to 5 mm, the finished surface is in the same vicinity as this defect occurrence position, pit-like defects are likely to occur on the working surface of the die after the finishing process, and the defect occurrence position is It is directly under the finished surface, and the service life of the mold is likely to be shortened. In order to prevent these, the casting of the present invention,
It is characterized in that the dendrite-like structure grows from the surface of the cast product to the inside of the mold from the working surface of the mold after finishing. After casting, the surface of the cast product is machined to form the working surface of the mold, and the dendrites from the surface are fully developed to the inner side during casting so that pit defects do not occur in the finished dimension. . For example, as shown in FIG. 4, this means promotes solidification from the mold surface by using a chill which is equivalent to or larger than the product weight, and controls the growth of dendrites to a required size to eliminate this defect. It is possible to enclose the easily generated part inside the working surface of the die after finishing. This method made it possible to produce a sound casting.

[0012]

EXAMPLES The present invention will be described below with reference to production examples of a lower die insert for casting aluminum wheels for automobiles. As shown in FIG. 1, a mild steel pipe is formed into a shape of a vignette having an annular portion 1, a leg-shaped portion 2 extending upward from the annular portion, and a blind alley-like branch 3, and the inside of the pipe is communicated with each other. did.
FIG. 1 shows a cross-sectional view of the blind alley branch 3 part. A baffle 4 is shown at the branch portion 3 in the sectional view. The baffle also sufficiently cools the bottom of the branch 3 by the bypass flow of the cooling medium. In FIG. 1, supply and discharge of the cooling medium are indicated by arrows. As shown in FIG. 2, the molding of the mold using the tubular product A is performed by placing the leg-shaped portion 2 of the tubular product A in a mold composed of an upper mold B and a lower mold C on which a chill D is set. I installed it towards the top and made a model. Then, before pouring,
As shown in FIG. 1, a molten metal serving as a mold material for SKD61 was cast at a casting temperature of 1540 ° C. while flowing N ₂ gas as a cooling medium. 850 ℃ × after disassembling the mold and maintenance
6Hr annealing, 1010 ° C x 1Hr quenching, 6
Each heat treatment of tempering at 40 ° C. × 3 Hr was performed. The tubular product A having the cooling holes was not deformed or the like, and good inserts without defects could be obtained.

FIG. 3 is a schematic view of a cross-sectional macrostructure of the above-described embodiment and FIG. 4 which is the same as the above-described embodiment except that the cooling die D is not mounted. However, the flow rate of the cooling medium gas at the time of casting was set relatively small in the case where the chill D was installed as compared with the case where it was not installed because the cooling load is small. From the comparison between FIG. 3 and FIG. 4, since there is no chiller and the flow rate of the cooling gas medium is relatively large in FIG. 4, the development of the dendrite extending from the mold surface with respect to the dendrite extending from the tubular body processed product A is shown. The crossing part of both dendrites is approaching the planned machining finish line (shown by the chain double-dashed line). However, in the case of FIG. 3, since the cooling metal D can be provided and the flow rate of the cooling medium gas can be relatively reduced, the intersecting portion of the dendrite from the tubular body processed product A and the mold wall is the inner side of the cast product. The machine processing finish line has not been reached. In addition, the outer surface of the tubular body is shown in each of the cast products (indicated by thin broken lines in FIGS. 3 and 4).
Are fused throughout, and the peripheral part of the tubular body is dense and sound with dendrite developed, as can be seen from each drawing, and there is no concern about strength and thermal conductivity. there were.

[0014]

As described above, according to the method invention of the present application, a casting having a cooling hole does not need to be filled and discharged with sand covered with a thermosetting resin, and can be easily and pouring metal. It is possible to reliably produce a product with excellent quality that is well integrated, and the cast product of the present application is a product with a dense and sound casting structure in the peripheral part of the pipe, the finished surface or the part just below it. Yes, both are extremely useful industrially.

[Brief description of drawings]

FIG. 1 is a diagram showing a processed tubular body used in an example of the present invention.

FIG. 2 is a cross-sectional view showing a state in which a processed tubular body is installed in a mold.

FIG. 3 is a schematic diagram showing a macrostructure of a cast product obtained by casting according to FIG.

FIG. 4 is a schematic diagram showing a macrostructure of a cast product obtained without using the chill D as compared with FIG.

[Explanation of symbols]

1 annular part, 2 leg part, 3 blind alley branch, 4 baffle, A tubular processed product, B upper mold, C lower mold, D chill, a dendrite from mold wall, b tubular product processed surface Dendrite, c Machine finishing surface

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kennobu Wakamatsu 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Co., Ltd. (72) Inventor Sadamoto Sakamoto 1, Toyota Town, Aichi Prefecture, Toyota Motor Co., Ltd.

Claims (7)

[Claims] 1. A cast product having a cooling hole, which is formed by casting a tubular product, which has been molded so that a fluid flows through the inside, from outside of the cast product, wherein the tubular product and the molten metal are both iron. After casting, the two are fused at a part or the whole of their respective interfaces after casting, and the dendrite-like structure is from the surface of the cast product to the inside of the work surface immediately after the finishing work immediately below the tubular product and the tubular shape. A cast product having cooling holes, which are characterized by growing from the surface of the body-worked product. 2. A casting having a cooling hole formed by casting a tubular processed product from the outside so that a fluid flows through the inside so that the fluid flows through the inside, and the cooling hole through which the fluid flows is partly formed. A casting having a cooling hole characterized by having a baffle. 3. Casting of a cast product having a cooling hole for forming a tubular product, which is formed so that a fluid flows through the inside, in a mold, and the tubular product is cast from the outside with a molten metal. In the method, the tubular body processed product and the molten metal are both iron-based alloys, and a casting having a cooling hole characterized in that a cooling medium flows through the tubular body processed product at least for a predetermined period after the start of pouring. Casting method. 4. The method for casting a casting having a cooling hole according to claim 3, wherein the cooling medium is a gas body. 5. The method for casting a cast product having a cooling hole according to claim 3, wherein the tubular product is made of mild steel. 6. The method for casting a cast product having a cooling hole according to claim 3, wherein the processed tubular body is made of stainless steel. 7. The method for casting a casting having a cooling hole according to claim 3, 4, 5 or 6, wherein a cooling metal is embedded in a predetermined portion in the mold.