JP2011240392A - Casting apparatus, die structure, and casting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a casting apparatus capable of applying a riser without trouble even when casting at a low pressure; a die structure; and a casting method.SOLUTION: The casting apparatus includes: a die that has an upper mold 20 provided with a riser part 22 where the riser for replenishing molten metal is supplied and a lower mold 10 provided with a pouring opening 11; cooling units 23, 51, and 52 for cooling the riser; and temperature control unit 14, 24, and 53 for controlling the temperature of the riser by the cooling unit according to the temperature of the lower mold so that the point when the solidification of the riser is completed approaches the point when the solidification of the molten metal at the pouring opening is completed.

Description

  The present invention relates to a casting apparatus, a mold structure, and a casting method.

  In general, in the low-pressure casting method used for casting light alloys, the molten metal is laminarly filled into the mold at a low speed, so gas entrainment and oxide generation are suppressed as much as possible compared to other casting methods. Is done. For this reason, the low pressure casting method is widely used when producing a cast product with a high degree of soundness.

  However, conventionally, when producing a healthy product by the low pressure casting method, it is necessary to keep the mold surface temperature high to some extent in order to ensure the flow of the molten metal when filling the molten metal. Further, when the molten metal is solidified, it is necessary to promote directional solidification in order to maintain the effect of the hot water from the pouring gate. Therefore, when the mold is cooled, the balance of directivity must be maintained.

  Therefore, for example, Patent Document 1 proposes a technique for cooling the lower mold of the mold without breaking the directivity balance.

JP 7-164100 A

  However, such a conventional cooling technique cools the lower mold slightly within a range where the balance of directivity is not lost. Therefore, if the lower mold is strongly cooled in response to a request from the raw material of the molten metal, the directivity balance may be lost and a defect may be generated inside the raw material. As one of the methods for preventing the occurrence of such defects, a method in which a hot water is applied to the upper part of a portion where defects are likely to occur is often used in sand casting and gravity casting.

  In general, the hot water has a structure with high heat retention so that it becomes the final solidification part, and the solidification time is stabilized and slowed, whereas the molten metal near the pouring gate is easily affected by the temperature of the surrounding mold. In particular, when the mold temperature is low, such as when a series of casting cycles is started or when the casting cycle is restarted after stopping casting due to trouble, solidification is accelerated. For this reason, in several cycles immediately after starting or resuming the casting cycle, the hot water is not solidified at the time of mold release, and a mold release failure is likely to occur.

  On the other hand, if it is decided to wait until the hot metal solidifies so as not to cause mold release defects, the temperature of the mold will decrease during the waiting period, so the mold temperature will not rise no matter how many casting cycles are repeated. , Stable casting of good products is not possible. Therefore, at present, it is difficult to apply the hot water to low-pressure casting using a mold.

  An object of the present invention is to provide a casting apparatus, a mold structure, and a casting method capable of applying a hot water without trouble even when low pressure casting is performed using a mold in view of the state of the prior art. is there.

  The casting apparatus of the present invention includes a mold having an upper mold provided with a hot water portion to which a hot water for supplying molten metal is supplied and a lower mold provided with a pouring gate, and a cooling unit for cooling the hot water. And a temperature control unit for controlling the temperature of the hot water by the cooling unit according to the temperature of the lower mold (first invention).

According to this, when the molten metal is filled in the mold, if the temperature of the lower mold is low, the temperature control unit lowers the temperature of the hot water to speed up the solidification of the hot water and the hot water is solidified. The time point can be as close as possible to the time point when the molten metal at the gate is solidified. Thereby, since the time when mold release becomes possible can be advanced, mold release can be performed before the temperature of a lower mold falls again.
Further, even when the lower mold is forcibly and strongly cooled, the solidification of the hot water can be further accelerated accordingly, so that the hot water can be obstructed while enjoying the advantages of cooling the lower mold. Can be applied without.

  In the casting apparatus according to the first aspect of the invention, the temperature control unit is configured such that, at the start of a series of casting cycles, the time point at which the solidification of the molten metal is completed approaches the time point at which the solidification of the molten metal at the gate is completed. The temperature of the hot water is controlled (second invention).

  According to this, at the time of starting up a series of casting cycles, the next casting cycle can be started before the temperature of the lower mold is lowered, so that the series of casting cycles can be started from the stage of starting up. It is possible to quickly shift to the stable stage.

  In the casting apparatus according to the first or second invention, the cooling unit includes a flow path for flowing a cooling fluid provided in the upper mold, and a fluid supply unit for supplying the fluid to the flow path. A temperature sensor for detecting the temperature of the lower mold, and the temperature control unit controls the fluid supply unit according to the temperature of the lower mold detected by the temperature sensor, thereby The temperature of the hot water section is controlled (third invention).

  According to this, the period or flow rate of flowing the cooling fluid is determined in advance corresponding to the temperature of the lower mold that can be taken at the start of the casting cycle, and the temperature is controlled by controlling the fluid supply unit based on this. The control unit can easily control the temperature of the hot water.

  In the casting apparatus of each of the first to third inventions, the mold is for casting a cylinder head, and the hot water portion is provided in a portion of the upper mold corresponding to a portion directly above the combustion chamber of the cylinder head. (4th invention).

  According to this, even when the lower mold is strongly cooled in the molten metal part constituting the combustion chamber of the cylinder head, good directional solidification is promoted by replenishing the molten metal with the molten metal and optimizing the temperature gradient. It is possible to cast a cylinder head having a combustion chamber that enjoys the cooling effect of the lower mold without hindrance and has no defects and is excellent in high temperature and high pressure resistance.

  The casting apparatus according to the fourth aspect of the present invention further includes another cooling unit that cools the lower mold portion corresponding to the combustion chamber (fifth aspect).

  According to this, the cooling of the lower mold by the separate cooling section prevents the solidification delay in the molten metal portion corresponding to the combustion chamber, promotes directional solidification, and has no defects and high temperature and pressure resistance. Can be cast.

  The mold structure of the present invention detects a temperature of a lower mold having an upper mold provided with a hot water portion to which a hot water for supplying molten metal is supplied and a lower mold provided with a pouring gate. And a flow path provided in the upper mold for flowing a fluid for cooling the hot water in accordance with the temperature detected by the temperature sensor (a sixth invention). .

  According to this, similarly to the first invention, it is possible to advance the time when the mold release becomes possible and perform the mold release before the temperature of the lower mold decreases again. Moreover, even when the lower mold is forcibly cooled, the hot water can be applied without any trouble while enjoying the advantages of the lower mold.

  The casting method of the present invention is a casting method performed using a mold having an upper mold provided with a hot water portion to which a hot water for supplying molten metal is supplied and a lower mold provided with a pouring gate. The step of filling the mold cavity with the molten metal from the pouring gate, and the time when the solidification of the molten metal is completed after the filling of the molten metal is completed approaches the time when the solidification of the molten metal at the pouring gate is completed. And a step of controlling the temperature of the hot water in accordance with the temperature of the lower mold (seventh invention).

  According to this, similarly to the first invention, it is possible to release the mold before the mold can be released before the temperature of the lower mold decreases again, and forcibly cool the lower mold. Even in such a case, the hot water can be applied without any trouble while enjoying the advantages thereof.

It is sectional drawing containing the partial block diagram which shows the structure of the casting apparatus which concerns on one Embodiment of this invention. It is a figure which shows the table | surface which defined the period which cools hot water according to the temperature of the lower mold | type at the time of the start of the casting cycle by the casting apparatus of FIG. It is a figure which shows an example of the temperature change of a lower mold | type and a hot water when a casting cycle is repeated in the casting apparatus of FIG.

  Hereinafter, embodiments of the present invention will be described. FIG. 1 shows the configuration of a casting apparatus for casting a cylinder head by low pressure casting. FIG. 1 shows a cross section of a mold part forming a combustion chamber part of a cylinder head.

  This casting apparatus includes, as elements constituting a casting mold, a lower mold 10 disposed on the lower side of the cylinder head, that is, on the combustion chamber side, an upper mold 20 disposed on the upper side of the cylinder head, and a side surface side of the cylinder head. And a core 40 for forming the intake and exhaust ports of the cylinder head. A cavity 60 is formed inside the mold.

  Further, this casting apparatus opens and closes the valve 52 according to the temperature of the pipe 51 for supplying cooling water as a cooling fluid to the upper mold 20, the valve 52 provided on the pipe 51, and the lower mold 10. A control device 53 that performs control is provided.

  The lower mold 10 includes a pouring gate 11 for introducing molten metal supplied through a stalk (not shown) into the cavity 60 of the mold, an outer nest 12 provided in a nested manner at a position corresponding to the combustion chamber portion of the cylinder head, And an inner insert 13 provided in a nested manner with respect to the outer insert 12.

  Further, the lower mold 10 is provided with a temperature sensor 14 that detects the temperature of the lower mold 10 on the outer nesting 12 side of the gate 11. The inner insert 13 is provided with a flow path 15 through which a fluid for cooling the inner insert 13 flows.

  The upper mold 20 is provided with a hot metal mold 21 at a portion corresponding to a portion directly above the combustion chamber of the cylinder head. In the hot metal mold 21, a hot water part 22 to which hot water for supplying molten metal is supplied, a flow path 23 for circulating cooling water for cooling the hot water part 22, and a temperature sensor for detecting the temperature of the hot water. 24 is provided. The cooling water is supplied to the flow path 23 from a supply source (not shown) via the pipe line 51.

  The sliding mold 30 is composed of four mold elements divided in the left-right and front-rear directions. In FIG. 1, a cross section of only two mold elements divided in the left-right direction appears. These four mold elements are provided so that they can slide in the left-right direction or the front-rear direction with respect to the lower mold 10. The upper mold 20 is provided so as to face the lower mold 10 and move in the vertical direction.

  The control device 53 detects the temperatures of the lower mold 10 and the hot water based on detection signals from the temperature sensor 14 and the temperature sensor 24, and controls the opening and closing of the valve 52 according to the detection result. By this control, the period during which the fluid flows in the flow path 23 is determined, and the hot water in the hot water part 22 is cooled only during that period.

  In the casting apparatus configured as described above, when starting a series of casting cycles for casting the cylinder head, the sliding mold 30, the upper mold 20 and the core 40 are arranged at predetermined positions with respect to the lower mold 10. Clamped. Then, when the first casting cycle is started, the pressurized molten metal is supplied from the gate 11 to the cavity 60 and the feeder 22 and filled.

  The filled molten metal is solidified from a portion where the temperature becomes a predetermined value or less in a pressurized state. That is, it solidifies while showing the directivity from the part far from the gate 11 or the feeder section 22 or the part that is forcibly cooled to the gate 11 or the feeder section 22. At this time, the casting material shrinks due to solidification, but the molten metal that is insufficient due to this is replenished by the hot water in the hot water portion 22.

  During this time, cooling air or cooling water is circulated in the pipeline 15 and the inner insert 13 is forcibly cooled. Thereby, directional solidification is promoted in the molten metal part forming the periphery of the combustion chamber of the cylinder head, and the occurrence of casting defects due to the solidification delay is prevented.

  When solidification of the molten metal is completed, the mold is opened and the formed cylinder head is taken out. Thereafter, the next casting cycle is similarly started. When such a casting cycle is repeated several times, the lower mold 10 is sufficiently warmed, so that the series of casting cycles shifts from the startup stage to the stable stage.

  However, since the lower mold 10 is not warmed at the start-up stage, solidification of the molten metal at the pouring gate 11 proceeds faster than in the stable time when the lower mold 10 is sufficiently warmed. For this reason, if no allowance is provided, the casting in the feeder 22 is not yet solidified at the time when the solidification at the gate 11 is completed, so that the casting cannot be released.

  On the other hand, if it waits until solidification in the pouring gate 11 completes, the lower mold | type 10 will be cooled in the meantime, and it will return to the grade of the temperature at the time of a casting cycle start, A series of casting The cycle cannot be moved to the stable stage.

  Therefore, in this embodiment, the hot water is cooled by the control device 53 in the following manner during the pressurization period in each casting cycle at the stage of startup.

  The table in FIG. 2 defines a period for cooling the hot water in the casting cycle according to the temperature of the lower mold 10 at the start of the casting cycle. In the “lower mold temperature T” column in the table, a temperature category applied to the temperature of the lower mold 10 at the start of the casting cycle is described. In the “cooling period” column, the cooling period of the hot water corresponding to each temperature category is written. In the “cooling capacity” column, the cooling capacity exerted by each cooling period is described as a ratio of the cooling period to the pressurizing period to the molten metal. The pressurization period corresponds to the period from the start of the casting cycle to the point at which release is possible.

  Based on this table, the control device 53 opens the valve 52 in the casting cycle only during the cooling period corresponding to the temperature section to which the temperature of the lower mold 10 belongs at the start of the casting cycle. Thereby, the hot water can be cooled using the cooling capacity corresponding to the cooling period.

  That is, when the temperature of the lower mold 10 detected by the temperature sensor 14 at the start of the casting cycle is less than 400 ° C., the control device 53 performs the process from the start of pressurization to the molten metal to the end of the casting cycle. During the period, the valve 52 is opened to cool the hot water. In this case, since cooling is performed throughout the entire pressurization period, a cooling capacity of 100% is used.

  When the temperature of the lower mold 10 at the start of the casting cycle is 400 ° C. or higher and lower than 450 ° C., cooling is performed using only the latter half of the pressurization period in the casting cycle, that is, using a cooling capacity of 50%. When the temperature of the lower mold 10 at the start of the casting cycle is 450 ° C. or higher, the hot water is not cooled.

  FIG. 3 shows an example of the temperature change of the lower mold 10 and the temperature change of the hot water as the series of casting cycles progresses. In the figure, the horizontal axis represents time, the lower half of the vertical axis represents the temperature of the lower mold 10, and the upper half represents the temperature of the hot water.

  In FIG. 3, the lower curve 71 shows the temperature change of the lower mold 10, and the upper curve 72 shows the temperature change of the hot water. Pp is a pressurizing period in which pressure is applied to the molten metal filled in the mold, and Pc is a period in which the hot water is cooled, that is, a period in which the valve 52 is opened.

  As shown in FIG. 3, when the first casting cycle is started at time t0, the control device 53 immediately opens the valve 52 by opening the valve 52 because the temperature T0 of the lower mold 10 is less than 400 ° C. Start forced cooling. Thereafter, the temperature of the lower mold 10 rises as indicated by the graph curve 71 due to heat conduction from the molten metal filled in the cavity 60. In parallel with this, the temperature of the molten metal near the lower mold 10 is lowered.

  Thereafter, when the temperature difference between the temperature of the lower mold 10 and the molten metal adjacent to the lower mold 10 disappears, the temperature of the lower mold 10 starts to decrease. During this time, the temperature of the hot water also decreases rapidly from the temperature Ta at the start of the casting cycle due to forced cooling. At this time, the solidification of the molten metal proceeds, and when the time t1 is reached, the solidification of the molten metal and the solidification of the molten metal at the gate 11 are completed at the same time.

  At this time t1, the control device 53 detects that the temperature of the hot water has reached the separable temperature Tb by the temperature sensor 24, and closes the valve 52 accordingly. Therefore, the cooling period ends at the same time as the pressurization period ends. Thereafter, mold release is performed, and at time t2, the first casting cycle is completed, and the second casting cycle is started.

  At the start time t2 of the second casting cycle, the temperature T1 of the lower mold 10 is higher than the temperature T0 at the start time t0 of the first casting cycle, and is 400 ° C. or higher and lower than 450 ° C. Therefore, the control device 53 opens the valve 52 only in the second half of the pressurization period Pp in the second casting cycle. The temperatures of the lower mold 10 and the hot water change as in the first casting cycle.

  However, since the temperature of the mold is higher than that in the first casting cycle, it takes a longer time for the molten metal to solidify than in the first casting cycle, and solidification at the pouring gate 11 is completed at time t3. .

  As in the case of the first casting cycle, the control device 53 closes the valve 52 and terminates the cooling of the hot water portion 22 when the hot water is lowered to the temperature Tb at which the mold can be released at time t3. Also in this case, the solidification of the hot water and the solidification of the molten metal at the gate 11 are completed at the same time.

  Thereafter, mold release is performed, and a third casting cycle is started at time t4. The temperature T2 of the lower mold 10 at the time t4 is higher than the temperature T1 at the start of the second casting cycle and is 450 ° C. or higher.

  Therefore, the control device 53 does not cool the hot water supply unit 22. Further, it takes a longer time to complete the coagulation at the gate 11. Also in this case, the solidification of the molten metal and the solidification of the molten metal at the gate 11 are completed at the same time.

  The temperature of the lower mold 10 at the start of the third and subsequent casting cycles is the same temperature T2. That is, in the third and subsequent casting cycles, the graph curves 71 and 72 repeat the same pattern. Therefore, a series of casting cycles shifts from the third casting cycle to a stable stage.

  As described above, in the first and second casting cycles at the start of a series of casting cycles, since the mold is cold, the solidification of the molten metal proceeds quickly. Since it is cooled and solidification of the hot water progresses quickly, the solidification of the hot water is completed at the same time t1 or t3 as in the case of the molten metal at the gate 11. Therefore, at the time t1 or t3 when the pouring of the gate 11 is completed, the mold release is started without any trouble.

  In addition, since the hot water is forcibly cooled, the temperature of the lower mold 10 is higher than that in the case where the mold is released after waiting for the hot water to cool to the temperature Tb at which it can be naturally released. The next casting cycle is started before dropping to the extent of the temperature at the start time t0 or t2. Accordingly, the temperature of the lower mold 10 at the start of the casting cycle becomes the stable temperature T2 at the start of the third casting cycle, so that the transition to the stable stage is performed quickly.

  As described above, according to the present embodiment, the hot water is forcibly cooled only during a period corresponding to the temperature of the lower mold 10 at the start-up of the casting cycle, so that the solidification time of the hot water is reduced at the gate 11. Shorten to the same level as the solidification time of the melt. Thereby, when solidification of the molten metal at the gate 11 is completed, the mold can be shifted to the mold without any trouble, and a series of casting cycles can be quickly shifted to the stable stage.

  Therefore, even when the lower mold 10 is forcibly cooled, the cylinder head can be cast by low-pressure casting while applying the hot water without trouble. Thereby, combined with the effect of forced cooling of the lower mold 10, the temperature gradient in the molten metal constituting the combustion chamber is further optimized to promote directional solidification, and the combustion chamber is more excellent in high temperature and pressure resistance. Can be manufactured.

  Although the embodiment has been described above, the present invention is not limited to this, and can be appropriately modified and implemented. For example, although the above embodiment is a case where a cylinder head is cast, the present invention can also be applied to the case where other cast products are manufactured by low pressure casting.

  Moreover, in the said embodiment, although the period which distribute | circulates cooling water to the flow path 23 is changed, the cooling capacity used for cooling of hot water is controlled, but it replaces with this and distribute | circulates to the flow path 23. You may make it control by changing the flow volume of the cooling water to be made. Alternatively, as the cooling fluid, other liquid or air may be used instead of water.

  In addition, after the lower mold 10 has sufficiently warmed up and shifted to a stable stage in a series of casting cycles, the hot water is not cooled. Cooling may be performed.

DESCRIPTION OF SYMBOLS 10 ... Lower mold | type, 11 ... Spout, 12 ... Outer nesting, 13 ... Inner nesting, 14 ... Temperature sensor, 20 ... Upper mold | type, 21 ... Hot metal part mold, 22 ... Hot water part, 23 ... Channel, 24: Temperature sensor, 30 ... sliding type, 40 ... core, 51 ... pipe, 52 ... valve, 53 ... control device, 60 ... cavity, 71 ... graph curve, 72 ... graph curve, Pc ... cooling period, Pp ... addition Pressure period.

Claims (7)

A mold having an upper mold provided with a hot water portion to which a hot water for supplying molten metal is supplied and a lower mold provided with a water gate;
A cooling section for cooling the hot water;
A casting apparatus comprising: a temperature control unit that controls the temperature of the hot water by the cooling unit according to the temperature of the lower mold.   The temperature control unit controls the temperature of the hot water so that the time at which the solidification of the molten metal is completed is closer to the time at which the solidification of the molten metal at the gate is completed at the start of a series of casting cycles. The casting apparatus according to claim 1, wherein: The cooling section includes a flow path for flowing a cooling fluid provided in the upper mold, and a fluid supply section for supplying the fluid to the flow path,
The lower mold is provided with a temperature sensor for detecting the temperature,
The temperature control unit controls the temperature of the hot water by controlling the fluid supply unit according to the temperature of the lower mold detected by the temperature sensor. 2. The casting apparatus according to 2. The mold is for cylinder head casting,
The casting apparatus according to any one of claims 1 to 3, wherein the hot water portion is provided in a portion of the upper die corresponding to a portion directly above the combustion chamber of the cylinder head.   The casting apparatus according to claim 4, further comprising another cooling unit that cools a portion of the lower mold corresponding to the combustion chamber. A mold having an upper mold provided with a hot water portion to which a hot water for supplying molten metal is supplied and a lower mold provided with a water gate;
A temperature sensor for detecting the temperature of the lower mold;
A mold structure comprising: a flow path provided in the upper mold for flowing a fluid that cools the hot water in accordance with a temperature detected by the temperature sensor. A casting method is performed using a mold having an upper mold provided with a hot water supply portion to which a hot water for supplying molten metal is supplied and a lower mold provided with a water gate,
Filling the mold cavity with molten metal from the gate;
After the filling of the molten metal is completed, the molten metal is cooled according to the temperature of the lower mold so that the solidified time of the molten metal approaches the time point when the solidification of the molten metal at the gate is completed. A casting method comprising the steps of:

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