JP2013169554A - Casting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a casting method for removing a metal core without going through secondary heating.SOLUTION: There is provided a casting method for carrying out casting by pouring molten metal into a cavity formed between a metal mold and a metal core arranged in the metal mold, the casting method being characterized in that: a melting point of the metal core is lower than a congealing point; and a temperature of the metal core and a temperature of the molten metal in pouring are preset so that the metal core may begin to melt after an inner solidified layer is formed, the inner solidified layer nearby a surface contacting the metal mold being solidified from among the molten metals after poured. The metal mold is released after an outer solidified layer is formed with the molten metal after poured being solidified nearby the surface contacting the metal mold, and a casting after mold-released is tilted after the metal core is at least molten nearby a surface contacting the inner solidified layer to let the metal core having been molten flow out by its own weight.

Description

  The present invention relates to a casting method for casting a casting having a hollow portion using a metal core.

Cast iron casting using iron or an iron alloy is excellent in terms of workability, casting strength, price, and the like, and is widely used for manufacturing various parts.
For example, when producing a cast iron casting having a hollow portion, usually, molten iron is poured into a main mold in which a sand core is installed, and the sand core is cast, and after the molten iron has solidified, the sand core is collapsed. The method of taking it out is used. However, when casting using a sand core, there is a problem that costs are required, for example, a facility for performing sand treatment is required.

Moreover, the technique shown below is known as a technique which manufactures the cast iron casting which has a hollow part using a metal core.
That is, Patent Document 1 describes a technique for removing a casting core (metal core) by melting it with an acid or the like after casting.

Patent Document 2 describes a technique for leaching a fusible core by immersing a mold casting in a molten metal made of a low melting point alloy of the same material as the fusible core (metal core). Yes.
Patent Document 3 discloses a technique in which a metal core having a melting point lower than that of an aluminum alloy is cast as a material for the metal core, and the core is heated and eluted for a predetermined time after the casting is removed from the mold. Have been described. In this technique, the outer peripheral surface of the metal core is coated with a coating agent.

JP 2007-283382 A Japanese Patent Laid-Open No. 3-146241 JP-A-8-206780

However, when the metal core is eluted with an acid as in the technique described in Patent Document 1, there is a problem that time and cost are very long.
In the techniques described in Patent Documents 2 and 3, as a pretreatment for removing the low melting metal core, the casting is completely solidified and then heated to a predetermined temperature again (hereinafter referred to as “secondary”). It is premised on performing "heating". In the secondary heating, the metal core is eluted only by heating to a temperature not higher than the melting point of the casting and not lower than the melting point of the metal core.
Therefore, even when the techniques described in Patent Documents 2 and 3 are used, there is a problem that it takes time and cost to perform the secondary heating described above.

  Then, this invention makes it a subject to provide the casting method which removes a metal core, without passing through secondary heating.

  In order to solve the above problems, the present invention is a casting method for pouring and casting a molten metal in a cavity formed between a mold and a metal core disposed in the mold, The melting point of the metal core is lower than the freezing point of the molten metal, and the temperature of the metallic core and the temperature of the molten metal during pouring are solidified in the vicinity of the contact surface with the mold of the molten metal after pouring. After the inner solidified layer is formed, the metal core is preset so as to start melting, and after pouring, the vicinity of the contact surface with the mold of the molten metal is solidified to form an outer solidified layer. After the mold is released, the metal core is melted at least near the contact surface with the inner solidified layer, and then the melted metal core flows out by its own weight by tilting the released casting. It is characterized by making it.

According to such a configuration, the melting point of the metal core is lower than the freezing point of the molten metal, and the temperature of the metallic core and the molten metal during pouring are in the vicinity of the contact surface with the mold in the molten metal after pouring. It is preset so that the metal core begins to melt after solidification and formation of the inner solidified layer. Therefore, when the molten metal is poured into the cavity, the heat transfer between the metal core and the molten metal solidifies near the contact surface of the molten metal with the metal core to form an inner solidified layer. Begins to melt.
That is, when the metal core starts to melt, an inner solidified layer having a predetermined thickness is formed in the vicinity of the contact surface of the molten metal with the metal core. Therefore, the shape of the casting can be maintained even when the metal core is melted.

  In addition, after pouring, the vicinity of the contact surface with the mold of the molten metal is solidified to form an outer solidified layer and then released. That is, at the time of releasing, an outer solidified layer having a predetermined thickness is formed in the vicinity of the contact surface with the mold in the molten metal. Therefore, the shape of the casting can be maintained even after releasing the mold.

  In addition, after at least the vicinity of the contact surface with the inner solidified layer of the metal core is melted, the molten metal core is caused to flow out by its own weight by tilting the released casting. Therefore, the metal core can be quickly removed from the casting without undergoing secondary heating.

Moreover, in the said casting method, it is preferable to use copper, a copper alloy, or graphite as said metal mold | die, and to use an aluminum alloy or a brass alloy as said metal core.
According to such a configuration, by using copper, a copper alloy, or graphite as the mold, and using an aluminum alloy or a brass alloy as the metal core, the melting point of the metal core is higher than the freezing point of the molten metal. Lower.

  Further, as described above, when the metal core starts to melt, an inner solidified layer having a predetermined thickness is formed in the vicinity of the contact surface of the molten metal with the metal core, and without undergoing secondary heating. The metal core can be quickly removed from the casting.

In the casting method, it is preferable that the mold includes a protection portion that prevents the molten metal flowing in toward the metal core from hitting the tip of the metal core.
According to such a configuration, since the inflowing molten metal is provided with a protective portion that prevents the molten metal from hitting the tip of the metal core, it is possible to more reliably prevent the metal core from being melted. Can do.

In the casting method, the metal core preferably includes a protective cap that prevents the molten metal flowing toward the metal core from hitting the tip of the metal core.
According to such a configuration, since the protective cap for preventing the flowing molten metal from hitting the tip of the metal core is provided, it is possible to more reliably prevent the metal core from being melted. Can do.

Further, in the casting method, it is preferable that the metal core is rod-shaped, and pouring is performed so that an axial direction of the rod-shaped metal core and an inflow direction of the molten metal are substantially parallel to each other.
According to such a configuration, turbulent flow is less likely to occur in the molten metal by pouring so that the axial direction of the rod-shaped metal core and the inflow direction of the molten metal are substantially parallel. As a result, it is possible to more reliably prevent the occurrence of melting damage.

  According to the present invention, it is possible to provide a casting method for removing a metal core without undergoing secondary heating.

It is a front view of the fixed mold | type used for the casting method which concerns on 1st Embodiment of this invention. (A) is a schematic diagram at the time of arrange | positioning and clamping a metal core, (b) is a schematic diagram of the state after pouring, (c) is the AA line shown to (b). It is sectional drawing at the time of cut | disconnecting by the plane containing. (A) is explanatory drawing which shows the location which detected temperature in the area | region K shown in FIG.2 (b), (b) is a temperature change in the position P, Q, R, S shown in (a), and a comparison. It is a graph which shows the temperature change inside a molten metal at the time of using a sand type | mold and an iron type | mold as an example. (A) is a schematic diagram which shows the state immediately after pouring, (b) is a schematic diagram which shows the state in which the inner side solidified layer, the upper solidified layer, and the outer side solidified layer were formed, (c) is mold release (D) is a schematic diagram showing a state in which the metal core is melted, and (e) is a schematic diagram showing a state in which the metal core flows out by tilting the casting. It is the schematic diagram of 2nd Embodiment type | system | group of this invention, (a) is a schematic diagram which shows the state immediately after pouring, (b) has formed the inner side solidified layer, the upper solidified layer, and the outer side solidified layer. It is a schematic diagram which shows a state, (c) is a schematic diagram which shows the state which released, (d) is a schematic diagram which shows the state which a part of metal core melt | dissolved, (e) is a casting. It is a schematic diagram which shows a mode that it inclines and flows out a metal core. It is a schematic diagram of 3rd Embodiment of this invention, (a) is a schematic diagram which shows the state immediately after pouring, (b) is the state in which the inner side solidified layer, the upper solidified layer, and the outer side solidified layer were formed. (C) is a schematic view showing a released state, (d) is a schematic view showing a state in which a part of a metal core is pulled out, and (e) is a view in which a casting is tilted. It is a schematic diagram which shows a mode that the remaining metal core is made to flow out. In 4th Embodiment of this invention, (a) is a schematic diagram at the time of arrange | positioning and clamping a metal core, (b) is a schematic diagram at the time of pouring, (c) is (b) ) Is a cross-sectional view when cut along a plane including the line C-C, (d) is a cross-sectional view when cut along a plane including the line D-D of (b), and (e) is (b) It is sectional drawing at the time of cut | disconnecting by the plane containing the EE line | wire of ().

  Modes for carrying out the present invention (hereinafter referred to as embodiments) will be described in detail with reference to the drawings as appropriate. In each figure, common portions are denoted by the same reference numerals, and redundant description is omitted.

<< First Embodiment >>
<Configuration of casting apparatus>
Below, according to each process of cast iron casting, each structure is demonstrated one by one.
FIG. 1 is a front view of a fixed mold used in the casting method according to the present embodiment. FIG. 1 shows, as an example, a fixed mold 100 in the case of casting a camshaft used for an internal combustion engine of an automobile, and the shaded portion is recessed on the back side of the drawing. The movable mold 200 (see FIG. 2C) has the same configuration as the fixed mold 100, and is disposed on the front side of the paper so as to face the fixed mold 100 in FIG.
In the present embodiment, first, the metal core 50 (see FIG. 2A) is placed at a predetermined position in a space formed by the fixed mold 100 and the movable mold 200 (hereinafter collectively referred to as “mold”). ) And perform mold clamping.

  The fixed mold 100 shown in FIG. 1 is clamped with the movable mold 200 in a state in which the metal core 50 (see FIG. 2) is arranged, so that the gate 10 described below, the vertical runner 20, and the horizontal A runway 30 is formed between the movable mold 200. Further, in the clamped state, cavities 40 and 40 corresponding to the shape of the camshaft are formed between the mold (that is, the fixed mold 100 and the movable mold 200) and the metal core 50. It is like that. In FIG. 1, only the surface on the fixed mold 100 side forming the cavities 40 and 40 (see FIG. 2A) is shown.

  Moreover, the gate 10 is opened at the upper end of the mold when the mold is clamped, and the vertical runner 20 extends downwardly in communication with the gate 10. The vertical runway 20 branches to the left and right near the lower end and communicates with the horizontal runways 30, 30. Furthermore, each side runway 30,30 is connected with the cavity 40,40 extended upwards.

Fig.2 (a) is a schematic diagram at the time of arrange | positioning and clamping a metal core. The range shown in FIG. 2A corresponds to the range G shown in FIG. 1, and B− when cut at the boundary surface H (see FIG. 2C) between the fixed die 100 and the movable die 200. It is B line sectional drawing.
In addition, as a metal mold | die (namely, the fixed mold | type 100 and the movable mold | type 200) shown to Fig.2 (a), a water-cooled copper metal mold | die with high heat conductivity can be used, for example. Here, the “water-cooled copper mold” means a copper mold in which the temperature is controlled by continuously flowing cold water through the water channels 101 and 102 provided therein, and the cooling capacity is improved. Yes.

As the metal core 50 shown in FIG. 2A, an aluminum alloy having a low melting point and high thermal conductivity (for example, A2024: melting point 500 to 600 ° C.) can be used. Here, the above-mentioned “low melting point” means that the melting point of the metal core 50 is lower than the freezing point (about 1200 ° C.) of the molten iron 60 (see FIG. 2B).
Thus, by using a water-cooled copper mold as the mold and using an aluminum alloy as the metal core 50, the molten iron 60 poured can be quickly cooled.

In addition, the metal core 50 extends in the radial direction and is disposed at a predetermined position in the mold (the fixed mold 100 and the movable mold 200) by a plurality of bar-shaped kelens 70 disposed vertically. For example, by drilling a plurality of holes (not shown) in the metal core 50 and the mold in advance at predetermined locations, and clamping the mold 70 with the kelen 70 inserted into the holes of the metal core 50 and the mold, respectively. The metal core 50 can be arranged at a predetermined position.
Note that the kelen 70 is made of the same material as the molten iron 60 and is cast with solidification of the molten iron 60.

After performing mold clamping as described above, the molten iron 60 is poured from above toward the gate 10 (see FIG. 1). Then, the molten iron 60 poured from the gate 10 falls in the vertical runway 20 due to gravity and heads toward the horizontal runways 30, 30 communicating with the left and right. Further, the molten iron 60 that has moved to the horizontal runways 30, 30 is pushed into the cavities 40, 40 by the pressure from the molten iron 60 that is continuously poured from the vertical runways 20, and the cavities 40, 40 Inside, the liquid level of the molten iron 60 rises. That is, the molten iron 60 flows upward in the cavities 40 and 40.
Further, the metal core has a rod shape and is arranged such that the axis is along the vertical direction.

Therefore, as shown in FIG. 2A, the axial direction of the rod-shaped metal core 50 and the inflow direction of the molten iron 60 are substantially parallel. This makes it difficult for turbulent flow to occur around the metal core 50, so that the lower end of the metal core 50 can be prevented from melting during pouring.
The time for pouring the molten iron 60 and the flow rate per unit time are set in advance so that the molten metal is filled to the predetermined positions of the cavities 40, 40 when the time has elapsed from the pouring start time. Yes.

FIG.2 (b) is a schematic diagram of the state which poured from the state of Fig.2 (a) and the said pouring was complete | finished. Moreover, FIG.2 (c) is sectional drawing at the time of cut | disconnecting by the plane containing the AA line shown in FIG.2 (b).
As described above, cold water continuously flows through the water channels 101, 102, 201, and 202 provided in the mold. In this embodiment, the water channels 101 and 102 are provided in the fixed mold 100 and the water channels 201 and 202 are provided in the movable mold 200 so as to surround the cavity 40. The cold water flows through the water channels 101, 102, 201, 202 when cold water stored in an external water storage tank (not shown) is pumped by a pump (not shown). . This makes it possible to appropriately control the temperature of the mold while promoting heat dissipation from the molten iron 60 to the mold.

  The flow rate of cold water (the flow rate supplied per unit time) is such that a solidified layer (an outer solidified layer 61 described later) having a predetermined thickness is formed in the vicinity of the contact surface between the molten iron 60 and the mold when the mold is opened. It is preset to be formed.

After pouring, the mold opens when a predetermined time elapses, that is, the fixed mold 100 and the movable mold 200 are separated. Rods (not shown) are respectively installed on a fixed base (not shown) on which the fixed mold 100 is installed and a movable base (not shown) on which the movable mold 200 is installed. By moving the rod, the fixed mold 100 and the movable mold 200 can be approached / separated.
And after performing mold opening, the casting 600 (refer FIG.4 (c)) which the outer surface solidified is taken out, and also the metal core 50 in which one part or all part melt | dissolved is taken out. The details of mold opening and removal of the metal core 50 will be described later.

<Temperature change of molten iron and metal core>
FIG. 3A is an explanatory diagram showing a location where the temperature is detected in the region K shown in FIG. The position P in FIG. 3A indicates the position inside the metal core 50 (that is, near the central axis of the rod-shaped metal core 50). Further, the position Q indicates a position near the contact surface with the molten iron 60 in the metal core 50.
A position R indicates a position near the contact surface of the metal core 50 in the molten iron 60. Further, the position S indicates the position inside the molten iron 60. Incidentally, “inside the molten iron 60” is a position where the distance to the outer surface of the metal core 50 and the distance to the inner surface of the mold (the fixed mold 100 and the movable mold 200) are substantially equal.

Next, temperature changes of the metal core 50 and the molten iron 60 will be described with reference to FIG. FIG. 3 (b) shows the temperature change at positions P, Q, R, and S shown in FIG. 3 (a) and the inside of the molten metal when a sand mold and an iron mold are used instead of the water-cooled copper mold as a comparative example. It is a graph which shows a temperature change.
In addition, the horizontal axis | shaft of the graph shown in FIG.3 (b) is the elapsed time [sec] from the iron melt arrival time, and a vertical axis | shaft is the temperature [degreeC] of each part. Here, “the molten metal arrival time” is the time when the liquid level of the molten iron 60 ascending the cavity 40 reaches the temperature detection position (positions P, Q, R, and S shown in FIG. 3A) ( t = 0).
In this embodiment, the case where the above-described water-cooled copper mold is used as the mold and an aluminum alloy is used as the metal core 50 is illustrated. Moreover, the case where the temperature of the iron melt 60 is about 1350 ° C. and the temperature of the metal core 50 is about 0 ° C. at the start of pouring is illustrated.

At the time when the molten iron 60 arrives at the positions R and S shown in FIG. 3A (time t = 0 in FIG. 3B), the temperature of the metal core 50 at the positions P and Q is 0 ° C. The temperatures of the molten iron 60 at positions R and S were all 1350 ° C.
Thereafter, the poured molten iron 60 is rapidly cooled by dissipating heat to the metal core 50 made of aluminum alloy having high thermal conductivity, and the temperature at the position R (iron melt surface: Cu type) shown in FIG. It decreases rapidly (time 0 to t1). Moreover, the temperature of the position S (inside molten iron: Cu type) gradually decreases due to the heat dissipation (time 0 to t2).

On the other hand, since the metal core 50 absorbs heat from the poured molten iron 60, the temperature at the position Q (metal core surface: Cu type) shown in FIG. 3A rapidly increases (time 0 to t3). ). In addition, the temperature at the position P (inside the metal core: Cu type) gradually increases due to the endotherm (time 0 to t4).
By the way, the molten iron 60 that has been poured is radiated to a water-cooled copper mold having high thermal conductivity, so that the temperature in the vicinity of the contact surface of the molten iron 60 with the mold is also rapidly reduced. Is not shown.

  At time t1, the temperature at the position R shown in FIG. 3A (iron melt surface: Cu type) falls to about 1200 ° C., which is the freezing point of the iron melt 60. That is, the molten iron 60 at position R is solidified at time t1. In the following description, a solidified layer formed by solidification of the vicinity of the contact surface with the metal core 50 in the iron melt 60 is referred to as an “inner solidified layer”.

  At time t <b> 2, the temperature at the position S (inside the molten iron: Cu type) shown in FIG. 3A decreases to about 1200 ° C., which is the freezing point of the molten iron 60. That is, the molten iron 60 at the position S is also solidified at time t2. Incidentally, when the molten iron 60 at the position S is solidified, the vicinity of the contact surface with the mold of the molten iron 60 is already solidified (not shown). In the following description, the solidified layer formed by solidifying the vicinity of the contact surface with the mold in the molten iron 60 is referred to as an “outer solidified layer”.

In the present embodiment, the water-cooled copper mold is used as described above, but in FIG. 3B, as a comparative example, the inside of the molten iron 60 in the case of using a sand mold and the case of using an iron mold. The temperature (the temperature at the position S shown in FIG. 3A) is also shown. Incidentally, an aluminum alloy metal core was used in all cases.
As shown in FIG. 3 (b), when a sand mold or an iron mold is used, the rate of decrease in the temperature inside the molten iron 60 is smaller than in the case of a water-cooled copper mold.
For example, the sand mold is inferior in terms of heat conductivity as compared with the water-cooled copper mold, and the heat of the molten iron 60 is not easily radiated to the sand mold. Therefore, when the sand mold is used, the temperature inside the molten iron 60 is about 1280 ° C. even after 3 seconds have elapsed since the arrival of the molten metal, so the inside of the molten iron 60 (freezing point: about 1200 ° C.) is at least solidified. Absent.

At time t3, the temperature at the position Q (metal core surface: Cu type) shown in FIG. 3A rises to about 580 ° C., which is the melting point of the aluminum alloy. That is, the core of position Q melts at time t3.
At time t4, the temperature at position P (inside the metal core: Cu type) rises to about 580 ° C., which is the melting point of the aluminum alloy. That is, the metal core 50 (aluminum alloy) at the position P is also melted at time t4.
Then, the temperatures at the positions P, Q, R, and S approach the temperature corresponding to thermal equilibrium (near 950 ° C.) as time passes.

Thus, in this embodiment, melting | fusing point (about 580 degreeC) of the metal core 50 is lower than the freezing point (about 1200 degreeC) of the molten iron 60, and the temperature (about 0 degreeC) of the metal core 50 at the time of pouring The temperature of the molten iron 60 (about 1350 ° C.) is such that, after pouring, the vicinity of the contact surface with the mold of the molten iron 60 is solidified and the inner solidified layer 62 is formed, and then the metal core 50 begins to melt. Is set in advance.
As a result, when the casting 600 is tilted after the mold release and the metal core 50 flows out, the inner solidified layer 62 having a predetermined thickness has already been formed (see FIG. 4C), and the shape of the casting 600 is reduced. Can be kept sufficiently.

  Incidentally, the cooling rate in the vicinity of the surface of the metal core in the molten iron 60 is preferably 450 ° C./sec or more, and the cooling rate in the molten iron 60 is preferably 90 ° C./sec or more. Details of mold release and outflow of the metal core 50 will be described later.

<Details of casting method>
Fig.4 (a) is a schematic diagram which shows the state immediately after pouring. In FIG. 4, the description of the water channels 101 and 102 is omitted (the same applies to FIGS. 5 and 6 described later).
As described above, a water-cooled copper mold having a relatively high thermal conductivity is used as the mold, and cold water continues in the water channels 101, 102, 201, and 202 (see FIG. 2C) in the mold. It is flowing in. Therefore, as shown in FIG. 4 (a), when molten iron 60 (the temperature at the start of pouring is about 1350 ° C. and the freezing point is about 1200 ° C.) is poured, the vicinity of the contact surface with the mold of the molten iron 60 is Immediately solidifies to form the outer solidified layer 61 (see FIG. 4B).

The metal core 50 is also made of a material having a relatively high thermal conductivity (aluminum alloy), and the metal core 50 has a predetermined temperature (for example, 0 ° C .: see FIG. 3B) at the start of pouring. Has been cooled to. Therefore, when the molten iron 60 is poured as shown in FIG. 4A, the vicinity of the contact surface of the molten iron 60 with the metal core 50 is immediately solidified to form an inner solidified layer 62 (FIG. 4 ( b)).
The inner solidified layer 62 functions as a heat insulating layer between the metal core 50 and the molten iron 60 flowing outside the inner solidified layer 62, and can maintain the shape of the casting 600.

  Further, an upper solidified layer 63 that is cooled and solidified by air is formed at the upper end portion of the molten iron 60 poured into the cavity 40. Incidentally, the kelen 70 is made of the same material as the molten iron 60, and is cast by the molten iron 50.

  Next, as shown in FIG. 4C, the mold 600 is opened and the casting 600 is taken out while there is sufficient residual heat in the casting 600 (a molded product in which at least a part of the molten iron 60 is solidified). An outer solidified layer 61 having a predetermined thickness is formed on the outer surface of the mold 600 that has been opened. In addition, an inner solidified layer 62 having a predetermined thickness that can sufficiently maintain the shape is formed near the contact surface with the metal core 50 against the flow of the molten iron 60 caused by vibration associated with mold opening. . Further, the upper end portion of the molten iron 60 poured into the cavity 40 is cooled with air to form an upper solidified layer 63.

  Moreover, as shown in FIG.4 (c), the inside of the iron melt 60 is not solidified at the time of mold opening, but is in the high temperature state. In this way, by releasing the mold at an early timing after the pouring is finished, it is possible to prevent the surface of the mold from being melted by the high-temperature iron melt 60 and to keep the mold life long. Moreover, after the outer solidified layer 61 having a predetermined thickness is formed, the mold is immediately released, so that the residual heat of the molten iron 60 is efficiently radiated to the metal core 50 without being lost to the mold. Can do. That is, melting of the metal core 50 can be promoted.

  And when predetermined time passes after mold opening, as shown in FIG.4 (d), all the metal cores 50 will fuse | melt. The temperature of the molten iron 60 at this point is preferably a predetermined temperature (for example, about 700 ° C.) higher than the melting point (500 to 600 ° C.) of the metal core 50 of the aluminum alloy.

  Further, the solidification of the molten iron 60 proceeds with the heat radiation from the molten iron 60 to the metal core 5, and the inner solidified layer 62 becomes thicker. Furthermore, by dissipating heat to the outside air, the outer solidified layer 61 and the upper solidified layer 63 also become thicker.

When all of the metal core 50 is melted, the melted metal core 51 is caused to flow out by its own weight as shown in FIG. That is, the casting 600 is inclined so that the end (the upper end shown in FIG. 4D) on the side where the metal core 51 is open to the outside is located downward. Then, the molten metal core 51 falls by gravity and flows out downward.
When the metal core 50 is an aluminum alloy, the metal core 50 can be removed by the heat of the casting 600 by releasing the mold within 20 seconds after pouring.
Incidentally, as shown in FIG. 4E, a container U for receiving the melted metal core 51 is disposed in advance, and the metal core 51 that has flowed into the container U can be reused.

<Effect 1>
According to the casting method according to the present embodiment, the metal core 50 can be removed without performing secondary heating. Therefore, the time and cost required for cast iron casting can be reduced and productivity can be improved. Further, as described above, the inner solidified layer 62 having a sufficient thickness is formed in the molten iron 60 at least when the surface of the metal core 50 starts to melt. Therefore, there is no possibility that the metal core 50 is melted by heat conduction from the molten iron 60 and the shape cannot be maintained by the pressure from the unsolidified molten iron 60.
As described above, in the casting method according to the present embodiment, the inner solidified layer 63 is formed on the iron melt 60 prior to the melting of the metal core 50 while utilizing the melting point difference between the metal core 50 and the iron melt 60. As described above, the temperature is adjusted in advance.

  Further, since the inner solidified layer 62 having a sufficient thickness is formed on the molten iron 60, it is not necessary to coat the metal core 50. Further, since the casting 600 is tilted after being released (that is, not tilted with the mold), the equipment can be made compact.

For example, compared with the case where a sand core is used, the metal core 50 which concerns on this embodiment is easy to install, and can reduce work burden. Further, as described above, secondary heating is not required, and the molding and the melting outflow of the metal core 50 can be performed continuously.
Therefore, the time required for casting per casting 600 (for example, camshaft) can be greatly shortened.
Further, it is not necessary to use a sand core when providing the hollow portion in the casting 600. Therefore, it is not necessary to provide a sand treatment facility, so that the cost can be reduced and the working environment can be improved. In addition, steps such as core sand removal and cast blast shot blasting are not required, so that work efficiency can be improved.

Incidentally, when the sand core is used, the sand core may be broken during casting, or a gas defect may occur in the sand core. On the other hand, the metal core 50 is used in this embodiment. Therefore, since the metal core 50 is not broken or gas deficiency occurs during casting, the yield can be improved.
In addition, the sand core is difficult to cut and polish, and its handling property is low. On the other hand, in this embodiment, it can respond to various processes by using the metal core 50.

  Moreover, in this embodiment, the pouring is performed by gravity casting so that the axial direction of the rod-shaped metal core 50 and the inflow direction of the molten iron 60 are substantially parallel. This makes it difficult to generate turbulent flow around the metal core 50, so that it is possible to more reliably prevent the vicinity of the lower end of the metal core 50 from being melted during pouring.

<< Second Embodiment >>
The casting method according to the present embodiment is different from the casting method according to the first embodiment in that the upper end portion that is not surrounded by the inner solidified layer 62 is not melted, but is otherwise the same as in the first embodiment. is there.
Therefore, the different parts will be described, and the description of the other parts will be omitted.

As shown in FIG. 5A, in the state where the metal core 50 is disposed and the cavity 40 is formed between the metal core 50 and the mold, the metal core 50 is not surrounded by the molten iron 60 (hereinafter, It is written as a skirting board (see region M in FIG. 5A). The baseboard means a portion of the metal core 50 that is longer than a required dimension in order to accurately and surely install the metal core 50 in the mold. Incidentally, the baseboard is supported from the radial direction by the keren 70.
When the molten iron 60 is poured, as shown in FIG. 5B, the molten iron 60 is cooled to the mold and the metal core 50, and the outer solidified layer 61 and the inner solidified layer 62 are formed. Further, the molten iron 60 is cooled by the outside air, and the upper solidified layer 63 is formed.

Next, when a predetermined time elapses after the mold release shown in FIG. 5C, the metal core 50 is surrounded by the inner solidified layer 62 of the molten iron 60 as shown in FIG. 5D. All the part 51 is melted. On the other hand, of the metal core 50, the portion of the baseboard not surrounded by the inner solidified layer 62 (see reference numeral 52) is maintained in a solid state without melting.
Next, as shown in FIG. 5E, the casting 600A is tilted, and the metal core 50 including the melted portion 51 (that is, the melted portion 51 and the baseboard portion 52 remaining as a solid state). Is caused to flow out by its own weight.

<Effect 2>
According to the casting method according to the present embodiment, in addition to the same effects as those described in the first embodiment, the metal core 50 can be more accurately attached to the mold by providing the baseboard having a predetermined length. And it can be installed reliably.

«Third embodiment»
Compared with the casting method according to the second embodiment, the casting method according to this embodiment has a width before all of the metal core 50 surrounded by the inner solidified layer 62 of the molten iron 60 is melted. The second embodiment is different from the second embodiment in that the metal core 51 (ie, the molten metal core) is allowed to flow out by tilting the casting 600B and pulling out the wood 600B. It is the same.
Therefore, the different parts will be described, and the description of the other parts will be omitted.

  6 (a) to 6 (c) are the same as FIGS. 5 (a) to 5 (c) described above, and a description thereof will be omitted. As shown in FIG. 6 (d), when a predetermined time elapses after the mold is opened, the portion 51 surrounded by the inner solidified layer 62 of the molten iron 60 in the metal core 50 is melted. That is, the rod-shaped metal core 50 arranged in the vertical direction gradually melts inward in the radial direction from the outer surface of the metal core 50 in contact with the inner solidified layer 62. Further, the lower end portion of the metal core 50 is gradually melted upward.

  In the present embodiment, as shown in FIG. 6 (e), before the metal core 51 surrounded by the inner solidified layer 62 of the molten iron 60 is completely melted, the remaining melted portion 53 is pulled out. As described in the second embodiment, the baseboard portion remains in a solid state without melting. Therefore, the baseboard remains in a solid state integrally with a portion close to the axis of the rod-shaped metal core 50 (a portion not yet melted).

Here, as shown in FIG. 6E, the solid portion 53 of the metal core 50 is pulled out. Then, the melted metal core 51 accumulates in the lower part of the cavity 40 by its own weight. The molten metal core 51 is maintained in a liquid state by absorbing heat from the high-temperature molten iron 60.
Then, as shown in FIG. 6 (f), the casting 600B is tilted, and the molten metal core 51 is caused to flow out by its own weight.

In this embodiment, a rod-shaped metal core 50 having a diameter of 16 mm is used and a molten iron 60 having a temperature of 1400 ° C. is cast. In addition, the maximum diameter of the product portion (that is, the portion corresponding to the camshaft) in the cavity 40 was 26 mm. Then, a cure time of 8 seconds was provided using a water-cooled copper mold. Here, the cooling rate of the molten iron 60 during the cure time was 190 ° C./sec.
Then, after 1 second from the end of the curing time, the metal core 53 was pulled out and the casting 600B was held upside down. As a result, the melted portion 51 of the metal core 53 was completely discharged by its own weight and could be removed. . Thereafter, the casting 600 was cooled, and a camshaft as a cast iron casting (FCD700) could be cast.

<Effect 3>
According to the casting method according to the present embodiment, in addition to the same effects as those of the second embodiment described above, the metal core 50 can be removed at an earlier timing, and the time required for the casting process can be further shortened. .
Incidentally, the metal core 50 and the molten iron 60 are gradually cooled by the outside air. Therefore, it is preferable that the molten metal core 51 flows out earlier. In this embodiment, before all the parts other than the baseboard of the metal core 50 are melted, the solid part 53 is pulled out, and the cast metal 600B is tilted to melt the melted metal core 51. Therefore, the timing for removing the metal core 50 can be advanced, and all of the molten metal core 50 can be surely discharged.

<< Fourth Embodiment >>
Compared with the casting method according to the first embodiment, the casting method according to the present embodiment includes protective portions 110 and 210 that prevent the molten metal 60 from hitting the tip of the metal core 50. The other points are the same as in the first embodiment.
Therefore, the different parts will be described, and the description of the other parts will be omitted.

Fig.7 (a) is a schematic diagram at the time of arrange | positioning and clamping a metal core in this embodiment, and has shown sectional drawing cut | disconnected by the boundary surface of a fixed mold | type and a movable mold | type. As shown in FIG. 7A, the mold (the fixed mold 100 and the movable mold 200) prevents the molten iron 60 flowing into the metal core 50 from hitting the tip of the metal core 50. A protection unit 110 (and 210) is provided.
When pouring from the state of FIG. 7A, the molten iron 60 poured into the gate 10 (see FIG. 1) flows through the vertical runner 20 and the horizontal runner 30 and flows into the cavity 40. And the liquid level of the molten iron 60 which flowed into the cavity 40 gradually rises to a state shown in FIG.

FIG.7 (c) is sectional drawing at the time of cut | disconnecting by the plane containing CC line shown in FIG.7 (b), FIG.7 (d) is the case at the time of cut | disconnecting by the plane containing DD line. FIG. 7E is a cross-sectional view taken along a plane including the EE line.
As shown in FIG. 7D and FIG. 7E, the fixed mold 100 is radially inward from the portion corresponding to the tip of the metal core 50 (that is, from the axis of the rod-shaped metal core 50). A columnar protective portion 110 that protrudes in the direction of heading is provided. Similarly, the movable mold 200 includes a columnar protection portion 210 that protrudes radially inward from a portion corresponding to the tip portion of the metal core 50.
A water channel 103 extending radially inward is formed in the protection unit 110, and a water channel 203 extending radially inward is formed in the protection unit 210. And cold water flows through the water channels 101-103, 201-203 continuously.

  When the fixed mold 100 and the movable mold 200 are clamped, the distal end of the protective part 110 and the distal end of the protective part 210 are brought into contact with each other in the radial direction (see reference numeral N in FIG. 7E). And the cylindrical holes 103 and 203 are formed in each said front-end | tip part faced | matched. The holes 103 and 203 are arranged so that the lower end of the metal core 50 is positioned above the holes 103 and 203 so that cold water continuously flows through the holes 103 and 203.

Thus, in the state where the mold is clamped, the protective part 110 of the movable mold 200 and the protective part 210 of the fixed mold 100 are in contact with each other so as to wrap the metal core 50 from below, so that the molten iron 60 flows from below. Thus, the lower end portion of the metal core 50 is protected.
In the state where the mold is clamped, the molten iron 60 flowing from below through the vertical runway 20 and the horizontal runway 30 (see FIG. 1) is the gaps X and Y provided by the protection portions 110 and 210. (Refer to FIG. 7D and FIG. 7E) flows upward to fill the cavity 40.

<Effect 4>
According to the casting method according to the present embodiment, the mold (the fixed mold 100 and the movable mold 200) includes the protective portions 110 and 210 that prevent the molten iron 60 from hitting the tip of the metal core 50. If the protection parts 110 and 210 are not provided, the hot iron melt 60 flows into the lower end of the metal core 50. Therefore, since the lower end portion of the metal core 50 is more easily melted than other portions, it is desirable that the flowing high-temperature iron melt 60 does not directly hit.

  According to the casting method according to the present embodiment, the tip of the metal core 50 is melted before the inner solidified layer 62 is formed by the high-temperature iron melt 60 flowing from below the metal core 50. This can be surely prevented. Therefore, it is possible to accurately manufacture a casting having a hollow structure corresponding to the metal core 50.

≪Modification≫
As mentioned above, although the casting method concerning this invention was demonstrated by each embodiment, the embodiment of this invention is not limited to these description, A various change etc. can be performed.
For example, in each of the embodiments described above, a water-cooled copper mold is used as the mold (the fixed mold 100 and the movable mold 200), but the present invention is not limited to this. That is, even if cold water is not passed through the mold, copper can absorb heat sufficiently from the molten iron because of its high thermal conductivity. Moreover, it is good also as promoting heat dissipation from the molten iron 60 to a metal mold | die with a radiation fin instead of water cooling.

  Moreover, in each said embodiment, although copper was used as a member of a metal mold | die, it is not restricted to this. For example, a copper alloy or graphite may be used as the mold. By the way, when cast by the method of the first embodiment using a metal core of an aluminum alloy and a graphite mold, the metal core can be removed while maintaining the shape of the casting as with the copper mold. It was. At this time, the cooling rate of the molten iron was 100 ° C./sec.

  In each of the above embodiments, an inexpensive aluminum alloy is used as the metal core 50, and the molten metal temperature when the metal core 50 is taken out is set to 700 ° C. or higher. However, the present invention is not limited to this. For example, an inexpensive brass alloy (for example, C2600: melting point 800 to 900 ° C.) may be used as the metal core. In addition, when using the metal core of a brass alloy, it is preferable that the molten metal temperature at the time of taking out the said metal core shall be 900 degreeC (melting | fusing point of a brass alloy) or more.

Moreover, although each said embodiment demonstrated the case where the iron melt 60 and the metal core 50 of an aluminum alloy were used, it is not restricted to this.
For example, a combination of molten aluminum alloy and a metal core of lead alloy, bismuth (Bi), or Sn (tin) may be used. That is, the metal core 50 has only to have a melting point lower than the freezing point of the molten metal and keep the shape against the flow of the molten metal while absorbing the heat from the molten metal and forming the inner solidified layer 62 in the molten metal. .

Moreover, in the graph of FIG.3 (b) shown in 1st Embodiment, after the inside of the iron melt 60 solidified (refer time t2), the case where the surface of the metal core 50 melt | dissolves was shown (time t3). Reference), but not limited to this.
That is, if the above-described inner solidified layer 62 is formed on the molten iron 60 (that is, molten metal surface solidification shown in FIG. 3B: see time t1), the solidification inside the molten iron 60 and the metal core 50 are performed. The front-rear relationship with the melting of the surface may be opposite to that described above.
Note that these can be adjusted by appropriately setting the temperature of the metal core 50 and the temperature of the molten iron 60 during pouring.

Moreover, although 4th Embodiment demonstrated the case where a metal mold | die was equipped with the protection parts 110 and 210 which prevent the molten iron 60 from hitting the front-end | tip of the metal core 50, it is not restricted to this. For example, the metal core 50 may be provided with a protective cap (not shown) that prevents the incoming molten iron 60 from hitting the tip of the metal core 50.
The protective cap is made of the same material as the molten iron 60 and is installed so as to cover the lower end of the metal core 50. Accordingly, it is possible to reliably prevent the tip of the metal core 50 from being melted before the inner solidified layer 62 is formed by the high-temperature iron melt 60 flowing from below the metal core 50. it can.
Incidentally, the protective cap is cast in the molten iron 50.

  Moreover, although each said embodiment demonstrated the case where a camshaft was cast as casting, it is not restricted to this. For example, in addition to a long casting such as a cylinder, castings of various shapes can be cast.

100 Fixed mold (mold)
110 Protection part 200 Movable type (mold)
210 Protective part 10 Pouring gate 40 Cavity 50 Metal core 60 Molten iron 61 Outer solidified layer 62 Inner solidified layer 63 Upper solidified layer 70 Keren

Claims (5)

A casting method in which a molten metal is poured into a cavity formed between a mold and a metal core disposed in the mold,
The melting point of the metal core is lower than the freezing point of the molten metal,
The temperature of the metal core and the temperature of the molten metal at the time of pouring are determined after the molten metal is solidified in the vicinity of the contact surface with the mold and the inner solidified layer is formed. Preset to start melting,
After pouring, the vicinity of the contact surface with the mold of the molten metal is solidified to form an outer solidified layer, and then released from the mold.
Casting characterized in that, after at least the vicinity of the contact surface with the inner solidified layer of the metal core is melted, the melted metal core is caused to flow out by its own weight by tilting the released casting. Method. As the mold, copper, copper alloy, or graphite is used,
The casting method according to claim 1, wherein an aluminum alloy or a brass alloy is used as the metal core. The said metal mold | die is equipped with the protection part which prevents the said molten metal which flows in toward the said metal core from striking the front-end | tip of the said metal core. The Claim 1 or Claim 2 characterized by the above-mentioned. Casting method. The said metal core is equipped with the protective cap which prevents that the said molten metal which flows in toward the said metal core hits the front-end | tip of the said metal core. The Claim 1 or Claim 2 characterized by the above-mentioned. Casting method. The metal core is rod-shaped,
The casting method according to any one of claims 1 to 4, wherein the pouring is performed such that an axial direction of the rod-shaped metal core and an inflow direction of the molten iron are substantially parallel to each other. .

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