TWI572427B - Casting the cooling method - Google Patents

Description

Casting cooling method

The present invention relates to: after the molten metal is cast into a mold, by rapidly cooling the molten metal from the inside, even for a molten metal composed of a plurality of metals having a specific gravity difference, it is possible to prevent the influence of gravity The method of casting segregation. Further, there is a method for producing an alloy in which a molten metal is rapidly cooled and solidified, thereby miniaturizing a metal structure to prevent casting defects from occurring inside the casting, and by controlling the molten metal. The method of controlling the metal structure by cooling rate.

The conventional casting method is a method in which the molten metal liquid is cast into the mold and the mold is left as it is, so that the molten metal liquid is naturally cooled. Therefore, if the casting is performed, a plurality of metals having a specific gravity difference are formed. In the alloy, the unevenness of the metal component called "segregation" occurs due to the difference in solidification characteristics such as the difference in the precipitation temperature between the alloys. A molten metal liquid composed of an alloy containing a plurality of metals having a specific gravity difference, if the specific gravity of the solid phase initially crystallized is lighter than the specific gravity of the molten metal liquid, gravity is absorbed during solidification The effect of the crystallization of the solid phase will rise up in the molten metal.

In simple terms, the alloys will be solidified after separation in the alloy due to the difference in specific gravity of the alloys. In addition to the influence of gravity, the cause of segregation and internal defects is considered to be: because the main component of the mold is the material of foundry sand, the thermal conductivity is very low, and the heat preservation is high, so it is cast into the interior of the mold. The temperature of the molten metal liquid is not easily lowered, and as a result, segregation and internal defects are likely to occur.

There is a known method in which a metal having a high thermal conductivity is provided by a portion of the mold which is in contact with a molten metal liquid phase, and a rapid cooling can be performed by interposing between the mold and the molten metal liquid. "Cold gold" metal, which allows molten metal to cool faster than conventional methods. However, since the solidification shrinkage is carried out from the outer portion of the "cold gold", the solidified metal will be separated, and the cooling effect can only reach a localized place. In addition, due to the difference in the size of "cold gold", it sometimes causes: cracking, oozing, etc.

In view of the above-mentioned situation, because of gravity, the alloy with a specific gravity does not form a uniform metal structure when solidified, and has air on the earth, so air is mixed into the alloy during solidification. In this case, the metal structure is adversely affected by strength deterioration and the like. That is, if it is not a space like space space that is not dominated by gravity and there is no air, it cannot be freely manufactured: it consists of a plurality of metals with a difference in specific gravity. Alloy.

The technique of directly cooling the molten metal liquid cast into the mold itself, which is similar to the present invention, has been found in the prior art as disclosed in Patent Document 1 and Patent Document 2 below.

According to the invention disclosed in Patent Document 1, in a mold formed by hardening a cast sand in a casting frame, an extruding portion which is in contact with a casting product inside the casting mold is provided, and is stored in the soup portion. The soup is cooled and cooled using a cooling medium, and the cast product can be forcibly cooled by the soup. This is a technique in which the cooling pipe that has passed through the simmering portion is provided, and the simmering portion is directly cooled, whereby the heat of the metal can be utilized to effectively cool the cast product (refer to the abstract of Patent Document 1). Description).

According to the method disclosed in Patent Document 1, the cast product inside the mold is directly cooled by the forced cooling of the soup portion, and the high heat conductivity of the metal is used, so that it is placed after being cast into the molten metal liquid. Compared with the case of the mold, the effect that can be seen is that the cooling rate can be made larger, and since the cast product is directly cooled, the casting sand is not brought to the quality. The impact can also be reduced in terms of the labor required for the regeneration of the foundry sand.

However, in the invention disclosed in Patent Document 1, the cooling rate is not sufficient, and it takes about 60 minutes to lower the product temperature from 1100 ° C to 900 ° C (refer to Fig. 2 of Patent Document 1). If it is such a degree of cooling, in the case where a molten metal composed of a plurality of metals having a specific gravity difference is cast, it is impossible to prevent the influence of gravity. The resulting segregation. In addition, it is not possible to produce such an alloy which finely refines the metal structure without causing casting defects inside the casting.

The object of the invention disclosed in Patent Document 1 is to provide a problem of preventing the deterioration of the properties of the foundry sand due to the cooling method of the cast product to be used and the complication of the manufacturing equipment, and the casting product can be given Cooling control method for forced cooling castings. In contrast, the object of the present invention is to provide a casting method by rapidly cooling a molten metal from the inside even if it is directed to a molten metal composed of a plurality of metals having a specific gravity difference. It can prevent segregation caused by the influence of gravity. Further, it is a method for controlling the cooling rate of the molten metal after casting, and therefore is completely different in terms of technical idea.

The invention disclosed in Patent Document 2 is a casting method using a lost inner mold, which is characterized in that a vanishing inner mold in which a pipe is buried inside is produced, and the lost inner mold is buried in the foundry sand. At this time, the piping is connected to the cooling pipe, and after the molten metal is cast, the cooling material flows into the piping from the cooling pipe. According to this configuration, the solidification of the molten metal in the cavity is accelerated, and the occurrence of the casting can be suppressed. In addition, since the molten metal liquid around the pipe is rapidly cooled, the metal structure of the portion is made fine, and mechanical properties such as fatigue resistance, tensile strength, and elongation can be improved (refer to the summary of Patent Document 2). .

According to the method disclosed in Patent Document 2, it is possible to suppress the casting of the cast product, and it is possible to improve the mechanical properties such as fatigue strength, tensile strength, elongation, and the like. However, the casting side using the lost inner mold The method is a technique for forming a hollow portion inside a cast product. Specifically, it is a casting method for casting such a cast having a through hole in the direction of the center axis, and is not applicable to a shape having no through hole, and thus is limited in the shape of the cast product.

Further, according to the method disclosed in Patent Document 2, not only the shape is limited, but this method can only make the casting of the periphery of the pipe fine (according to the solution and paragraph in the abstract description of Patent Document 2) According to the description of 0004, the method cannot control the metal structure from the viewpoint of the miniaturization of the metal structure. The technical idea of the two is completely different from the method of controlling the cooling rate of the molten metal after casting as provided by the invention of the present invention.

In other words, in the methods disclosed in Patent Document 1 and Patent Document 2, it is only considered that the metal structure is promoted by accelerating the cooling rate, and the technical idea of controlling the metal structure is not included. The metal structure is made into a fine structure having a desired particle size and shape.

[Advanced technical literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2005-144461

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2000-263216

As for the personnel at the product development site, it is of course desirable to have a metal material that can achieve weight reduction, high durability, and thinness of the product. In order to solve such problems, the prior art is considered to be developed. A high-strength alloy that cannot be manufactured on the earth, an alloy with high toughness, an alloy with wear resistance, and the like. The composition of the metal that can solve these technical problems is a case where there is a case where the difference in specific gravity is small or a component that is not affected by gravity. However, the practical problem is that when it is intended to be a complex number having a specific gravity difference When the alloy was developed, it was still unable to escape the influence of gravity existing on the earth.

If it is a place in space space that is not subject to gravity, it is possible to manufacture an alloy composed of a metal having a difference in specific gravity. However, in the current situation, if it is to be manufactured in space, it needs a huge amount. The cost is simply not in line with reality. For the above reasons, in terms of the status quo, it is still impossible to escape the influence of gravity existing on the earth. Therefore, the development of new alloys is still in a state of being hit by a reef, so it is not expected to be developed: a manufacturing method is a method of producing an alloy composed of a metal having a difference in specific gravity even on the earth.

At present, among alloys having a metal component which cannot be produced on the earth, a metal component which can achieve weight reduction, high durability, and thinness of the product is contained, and therefore, an ultrahigh strength alloy and an alloy having ultra high toughness are required. Alloys with super abrasion resistance are highly likely to exist, and if these cannot be utilized, it is a pity that from the viewpoint of industrial development. For example, an alloy having the same excellent properties as a rare earth metal There is a possibility of existence, and even if rare earth metals can no longer be obtained in the future, as long as these alloys can be used, they are valuable as substitute materials for rare earth metals.

Furthermore, it is also expected to be able to develop a new technology which can suppress the unevenness of the material composition caused by segregation and suppress and prevent the inside of the material even for a large-sized large-sized member. A technique that produces defects and ensures material quality.

According to the casting method disclosed in the present invention, by cooling water or the like flowing through a cooling pipe penetrating a part of the end portion not constituting the product portion, even if it is not in the space of the universe, the difference in specific gravity can be suppressed. The distribution of a plurality of material components is uneven, and defects can be suppressed and prevented from occurring inside, and material quality can be ensured.

Further, according to the casting method disclosed in the present invention, the cooling rate can be controlled extremely accurately in accordance with the material, and thus the metal structure can be controlled. The molten molten metal immediately after casting will generate convection along the inner wall of the mold and flow inside the mold. When the temperature is high and the molten metal can flow in the mold, even if there is a difference in density among the plurality of alloys contained in the molten metal, if the convection becomes weak, a so-called " Segregation, therefore, it is necessary to lower the temperature as quickly as possible to the solidification start temperature, that is, the primary precipitation temperature.

In addition to this, a desired metal structure can be obtained by controlling the cooling rate from the initial precipitation temperature to the solidification end temperature. However, it is not necessary to simply crystallize the crystal. If you want to obtain certain material strength characteristics, you must also let it be called The columnar crystal of "dendrite" grows to some extent.

The refinement of the metal crystal is not only a primary crystal dendritic crystal, but more importantly, the eutectic or intermetallic compound formed thereafter needs to be fined as well. When the cooling rate is increased, the influence of the toughness of the cast product can be alleviated by making the metal structure fine. The method of minimizing primary crystal dendrites comprises: reducing the dendritic structure itself, suppressing the number of secondary branching arms derived from dendrites, and reducing the secondary branches. The spacing of the arms (the branches that are derived from the principal axis of the dendrites at right angles) is called the secondary branching arm.

In general, if the interval between the secondary branch arms of the dendrite is reduced, the eutectic and the compound distributed in the gap become smaller and become finely distributed throughout the whole. Moreover, it is known that the interval of the secondary branching arms of the dendrites is closely related to the cooling rate, and the faster the cooling rate, the smaller the interval of the secondary branching arms of the dendrites Propensity.

The spacing of the secondary branching arms of the dendrites, which are governed by the cooling rate, can have a large effect on the mechanical properties of the casting. That is, the faster the cooling rate is, the smaller the interval between the secondary branching arms of the dendrites becomes, and the strength and elongation are also greatly increased. The interval between the secondary branching arms of the dendrites is particularly important for the elongation, the ramming value and the fatigue strength of the toughness of the cast product.

The invention, in particular, by controlling the temperature from the initial precipitation The cooling rate during the solidification end temperature is not only the finening of the dendritic structure, but also the control of the metal structure by controlling the interval of the secondary branching arms of the dendrites, and further control: indicating the cast product Material properties such as toughness elongation, impact value, and fatigue strength.

In order to solve the above-described technical problem, the casting method of the present invention is a cooling method in which casting is performed by using a mold in which a cooling water supply pipe that passes through the mold is inserted through an internal space of the mold, and is characterized in that: After the molten metal is cast into the mold, the molten metal is rapidly cooled by flowing a cooling medium through the cooling water supply pipe.

In order to solve the above-described technical problems, the casting cooling method of the present invention is characterized in that the cooling medium is water.

In order to solve the above-described technical problem, the casting cooling method of the present invention is characterized in that the flow rate of water flowing through the cooling water supply pipe is 10 liters/min or more.

In order to solve the above-described technical problems, the casting cooling method of the present invention is characterized in that the pipe diameter of the cooling water supply pipe is 10~ 30.

In order to solve the above-described technical problem, the cooling system for casting of the present invention is a cooling system that performs casting by using a mold in which a cooling water supply pipe that passes through the mold is inserted through an internal space of the mold, and is characterized in that: by a cooling water supply pipe that penetrates the mold in the internal space of the mold, a water tank that stores water in advance, and a pressure pump that pressurizes the water to supply the cooling water supply pipe. Further, it is possible to control the cooling time from the initial precipitation temperature to the solidification end temperature.

According to the present invention, since the cooling is rapidly performed from the inside of the molten metal solution, segregation can be suppressed by extremely accelerating the solidification rate, and a metal material having a composition component which is not currently available can be developed. In addition, by rapidly cooling the inside of the molten metal liquid, the molten metal liquid is rapidly solidified, whereby the cast iron and the pinholes can be minimized, and the material strength can be sufficiently increased, and even under severe conditions can be developed. There are no problems with the materials that can be used. Further, by controlling the cooling rate (solidification speed) of the molten metal by an extremely simple operation of adjusting the amount of water flowing through the pipe, a cast product having desired material properties can be obtained.

Further, according to the present invention, even in the conventional production method, since the metal component has a difference in specific gravity, it is affected by gravity, and therefore an alloy which cannot be manufactured on the earth can be manufactured. Out: Ultra-high strength alloys, alloys with ultra-high toughness, and alloys with super abrasion resistance.

10‧‧‧Molding

20‧‧‧Products Department

30‧‧‧Cooling water supply piping

40‧‧‧ Tangkou

50‧‧‧

Fig. 1 is a cross-sectional view showing a mold at the start of solidification of the present invention.

Fig. 2 is a cross-sectional view showing a mold in the process of solidification of the present invention.

Figure 3 is a plot of temperature drop (comparison of the present invention with conventional cooling methods).

Fig. 4 is a cross-sectional view showing a mold in which a plurality of pipes of the present invention are provided.

A specific embodiment of the method for cooling a cast product of the present invention will be described in detail with reference to the drawings. Embodiments of the present invention are as shown in Fig. 1. Fig. 1 is a cross-sectional view showing the internal structure of the mold 10. As shown in Fig. 1, the present invention is characterized in that the cooling water supply pipe 30 is provided in a portion of the product portion 20 in the mold 10 in a penetrating manner. In the embodiment, after the molten metal liquid is poured into the mold 10, the cooling water is passed through the cooling water supply pipe 30, and the solidification start temperature of the molten metal liquid cast into the mold is also the primary precipitation temperature. In the temperature range between the solidification end temperature and the solidification end temperature, the cooling water is continuously supplied through the cooling water supply pipe 30, and almost all of the cooling water is vaporized to forcibly cool the cast product.

First, the molten metal liquid is cast from the soup mouth 40, and when the product portion 20 is filled with the molten metal liquid, that is, when the liquid level of the soup portion 50 reaches the surface of the metal mold 10, the molten metal liquid is finished. Cast into work. After the completion of the casting operation of the molten metal liquid, the lid is overlaid from above the soup mouth 40, and then the cooling water is passed through the cooling water supply pipe 30 to perform forced cooling. In the first drawing, it is shown that solidification starts from the periphery (hatched portion) of the cooling water supply pipe 30. In the second drawing, the state is gradually solidified from the periphery of the cooling water supply pipe 30 toward the soup mouth 40 as time passes.

Fig. 3 is a graph showing the relationship between the water passing time of the cooling water and the temperature drop curve. X is a temperature drop curve when cooling is performed by the cooling method of the present invention; Y is a temperature drop curve when the mold is not simply forced cooling, but simply leaving the mold. As shown in Fig. 3, the time taken for the temperature of the molten metal inside the mold to fall from 400 ° C at the start of casting to 377 ° C at the solidification start temperature is about 1 to 2 minutes. On the other hand, if the forced cooling is not carried out according to the conventional method, the time taken for the mold to be simply placed after casting, the time taken from the casting of the molten metal liquid to 337 ° C of the solidification temperature is 30. More than a minute. According to the present invention, the time from the start of solidification of the molten metal liquid to the start of solidification can be greatly shortened. This shows that since the product portion 20 is forcibly cooled, it is efficiently cooled by the heat of vaporization.

Therefore, according to the forced cooling method of the cast product according to the embodiment of the present invention, the time required for the cooling process can be greatly shortened, and the production efficiency can be improved. Further, the cooling water supply pipe 30 for supplying the cooling water is provided in the product portion 20, and the structure of the manufacturing equipment is extremely simplified, and the manufacturing cost can be suppressed.

As shown in Fig. 4, a plurality of (A, B, C) cooling water supply pipes 30 may be provided, and the cooling rate of the product portion 20 may be increased by the shape of a larger product. Improve cooling efficiency. In this case, first, the cooling water supply pipe 30 (A in FIG. 4) which is further away from the soup mouth 40 is cooled, and the progress of solidification in the vicinity of the cooling water supply pipe A is confirmed. The cooling water flows to the cooling water supply pipe B and the cooling water supply pipe C. The number of the cooling water supply pipes 30 differs depending on the shape of the mold and the metal structure to be obtained. Therefore, it is necessary to adopt different manufacturing techniques for each of the different metals (the timing of cooling and the flow to the cooling water supply pipe 30). Water volume, etc.).

In this embodiment, the cooling medium of the cast product, that is, the cooling water, is considered to be almost always evaporated, so that a large amount of heat of vaporization of the cooling water can be used for cooling. The heat of vaporization of water is 2250 KJ/kg, so a large amount of heat of vaporization must be used to solidify the molten metal. Further, in the embodiment of the present invention, the piping is formed inside the mold constituting the product portion 20, and the cooling water is directly supplied to perform direct cooling. Therefore, the water amount of the cooling water is adjusted easily, efficient cooling can be performed, and the cooling rate can be easily controlled.

Therefore, the forced cooling of the cast product by the present embodiment can greatly shorten the time required for the cooling process and can improve the production efficiency.

The above is a specific embodiment of the method for cooling a cast product of the present invention, but the present invention is not limited to the above. The embodiment can be implemented with various modifications within the scope of the invention. For example, in the embodiment of the present invention, water is used as the cooling medium, but in addition to water, ice cubes or dry ice may be used.

[Example 1]

Using the casting method disclosed in the present invention, an ingot (having a size of 200 mm × 600 mm × 100 mm) cast from a material called "FCD450" was produced, and the size of the metal structure was controlled. First, a mold 10 for a furan (FURAN) resin is produced, and two cooling water supply pipes 30 are placed so as to penetrate the mold 10, and the molten metal liquid is melted at a temperature of 1370 ° C. The mold 10 is cast from the soup mouth 40. The molten metal is poured into the two cooling water supply pipes 30, and the metal structure is controlled to cast the ingot. The cross section of the ingot produced by the above method was cut, the microstructure was observed, and the hardness was measured.

After observing the structure, it is known that the defects of castings, such as casts and pinholes, are extremely reduced, and the shape of the cracked graphite (generally in the form of a block) is not visible anywhere in the section. The shape is very stable. As for the hardness, it is generally a value of about 150 to 210 HB. However, according to the manufacturing method of the present invention, it is a value of about 180 to 230 HB, and it can be known that the hardness is also increased by 10%. According to the above facts, it can be known that the casting method according to the present invention can achieve the effect that cannot be achieved by the conventional method, that is, the material called "FCD450" can be cast into a conventional manner. Large ingot shape cast.

[Embodiment 2]

According to the casting method of the present invention which is the same as that of the first embodiment, a material called "ADC12" which is generally used for aluminum precision casting is used, and the casting shape is 400 mm × 400 mm in a state where the casting temperature is 680 ° C. The ingot of 500mm size is subjected to cutting treatment to form an engine block for trial review.

In order to measure the material of the ingot produced by the above method, the cross section was cut to observe the structure. In the ingot produced by the above-described method, the cooling water is sprayed to the cooling water supply pipe 30, and the product portion is subjected to a forced cooling treatment from the inside of the mold. By controlling the metal structure by this method, the portion of the product portion after the cutting is obtained, and a metal crystal structure similar to the product cast by the precision casting method can be obtained. The number of pinholes is also extremely small, and there is almost no problem in terms of practicality. In addition, the physical property values of the materials are measured in many places on the entire ingot, and the physical properties of the materials fall within the tolerance range. As a result, products close to actual vehicles can be produced.

If the ingot of such a size is cast by a general sand mold (water glass) or an iron frame and external water cooling, a large casting is generated in the center portion and cannot be used. Even if casting does not occur, the material cannot be stabilized due to the occurrence of segregation.

[Industrial availability]

The present invention can be utilized for: after casting a molten metal into a mold, by rapidly cooling the molten metal from the inside, even for a molten metal composed of a plurality of metals having a specific gravity difference, it is possible to prevent gravity from being affected by gravity. A technical field related to a method for producing molten metal in a casting process that affects segregation. Further, it is also possible to use a technique related to a method for producing an alloy in which the molten metal is rapidly cooled and solidified to promote the fineness of the metal structure without causing casting defects in the cast product.

10‧‧‧Molding

20‧‧‧Products Department

30‧‧‧Cooling water supply piping

40‧‧‧ Tangkou

50‧‧‧

Claims (2)

A method for cooling a casting by using a mold in which a plurality of cooling water supply pipes passing through the mold are inserted through an internal space of the mold to perform casting, and is characterized in that: molten metal is cast The step of molding the mold and the step of cooling the molten metal to allow the cooling water to flow to the plurality of cooling water supply pipes; and the step of allowing the cooling water to flow to the plurality of cooling water supply pipes is to allow the cooling water to pass from The cooling water supply pipe that is away from the soup mouth starts to flow, and the cooling water is supplied to the cooling water supply pipe closer to the soup mouth while checking the progress of the solidification in the vicinity of the cooling water supply pipe farther from the soup. The method of cooling the casting according to the first aspect of the invention, wherein the flow rate of the water flowing through the cooling water supply pipe is 10 liters/min or more.