JP5800215B2 - Mold casting method - Google Patents

Description

  The present invention relates to a die casting method in which casting is performed while applying vibration to a molten metal during casting, and relates to a die casting method in which the metallographic structure of a cast product can be refined and shrinkage can be reduced.

  The mold casting method is a casting method in which a cavity formed in a mold is filled with a molten metal melted and cooled and solidified to obtain a cast product. The die casting method includes a gravity casting method in which a molten metal filling pressure is about several kPa to 1000 kPa, a low pressure casting method, and a die casting method in which a molten metal filling pressure exceeds 10 MPa and becomes a high pressure. Compared to the sand casting method, the die casting method has higher dimensional accuracy, has a fine metal structure, has excellent mechanical properties, and has high productivity. Has been widely applied to. On the other hand, for example, further improvement in mechanical properties is desired for cast products due to needs for weight reduction of automobiles and the like. Generally, in order to improve the mechanical properties of a cast product, it is said that it is effective to refine the metal structure and reduce shrinkage. In order to refine the metal structure and reduce shrinkage, it is necessary to control the cooling rate and solidification rate of the molten metal during casting.

  In order to control the cooling rate and solidification rate, there are methods such as providing a cooling mechanism in the mold to change the temperature distribution of the mold, or installing a large feeder and aiming for directional solidification with a coating agent. A sufficient effect cannot be obtained in a thick part of a cast product or a part where the mold temperature is high. Further, when a cooling mechanism is provided in the mold, there is a problem that the thermal strain of the mold increases and the mold life is shortened. As a method for refining the metal structure, a method of adding a finer agent to the molten metal is generally used. However, there are problems such as deterioration in material recyclability and an increase in raw material cost. In addition to the above-described method, a casting method in which vibration is applied at the time of casting has been proposed as one of methods for reducing the size of the metal structure and reducing shrinkage cavities.

  When the molten metal is vibrated during casting, the generation and growth of the primary crystal itself are suppressed, and the primary crystal is generated with a large number of equiaxed crystals as crystal nuclei and grows to equiaxed crystals. Further, even if the primary crystal is crystallized as a dendritic crystal, the dendritic crystal is broken or divided by vibration. As a result, the cast product has a metal structure composed of refined and granulated crystals, and can improve mechanical properties. Further, since the solid phase becomes fine granular crystals by vibration, the fluidity of the liquid phase in the solid-liquid coexistence state is improved, so that the replenishment of the molten metal to the final solidified portion accompanying solidification shrinkage can be further promoted. As a result, the occurrence of casting defects such as shrinkage can be expected to be suppressed, so that the mechanical properties of the cast product can be improved.

  As a casting method in which casting is performed while applying vibration, for example, in casting processing using a die casting machine or the like in Patent Document 1, when filling molten metal into a mold, directly or against the molten metal flowing in or the like A casting method for indirectly applying vibration such as ultrasonic vibration is disclosed. According to the casting method of Patent Document 1, by applying vibration such as ultrasonic vibration directly or indirectly to the molten metal filled in the mold, the crystal of the metal filled and solidified in the mold is uniform. In addition, it is said that the residual stress can be relaxed, the formation of nests generated inside can be suppressed, the adhesion to the mold can be improved, and the quality of the cast product can be improved.

  However, simply applying vibration by the conventional method does not sufficiently transmit vibration to the molten metal, and it is not always possible to obtain desired effects such as refinement of the metal structure and reduction of shrinkage cavities. When the vibration is directly or indirectly applied to the molten metal as in the casting method of Patent Document 1, the molten metal located near the vibration means attached to the mold or immersed in the molten metal can impart vibration relatively easily. It is difficult to efficiently vibrate the molten metal at a position away from the vibration means. In particular, when the cast product is large and / or has a complicated shape, a portion where vibration is not sufficiently transmitted is likely to occur, and the vibration effect cannot be obtained at such a portion. On the other hand, in order to obtain a vibration effect, applying a strong vibration or installing a large number of vibration means increases the size or complexity of the vibrator or vibration device, which increases the manufacturing cost. There is a problem that the load is accumulated in peripheral devices such as a mold body, a casting device, and a die-cutting device, resulting in failure of the device.

  Further, in the casting method for applying vibration, any type (type of vibration) (ultrasonic vibration, electromagnetic vibration, mechanical vibration, etc., if mechanical vibration, rotational motion, reciprocating motion, etc.) is applied to any vibration condition (parameter) ( There is no one that clearly suggests or discloses how much can be added in terms of frequency, displacement, speed, acceleration, etc., to achieve the effect of miniaturizing the metal structure and reducing shrinkage. Therefore, the actual situation is that trial and error are repeated in order to find an appropriate vibration condition. In the casting method of Patent Document 1, there is a description that the molten metal is irradiated with an ultrasonic wave having a frequency of 28 KHz as an example. However, the present inventors have examined that the metal structure of the metal structure is simply added by applying an ultrasonic wave having a frequency of 28 KHz. It was not always possible to expect sufficient effects in terms of miniaturization and shrinkage nest reduction.

Japanese Patent Laid-Open No. 5-329613

  An object of the present invention is to provide a mold casting method in which casting is performed while applying vibration to a molten metal during casting in view of the above-described prior art, and the metal structure of the cast product is refined to reduce shrinkage cavities. Therefore, it is providing the method which can improve a mechanical characteristic.

  In view of the above-mentioned object, the present inventors diligently studied focusing on the influence on the cooling rate with respect to vibration conditions and the like necessary for obtaining effects such as refinement of the metal structure and reduction of shrinkage cavities by applying vibration. As a result, it is found that the acceleration of the vibration to be applied and the surface roughness of the cavity in contact with the molten metal have a significant effect on the cooling rate, and at the same time the range of the acceleration and the surface roughness suitable for obtaining the desired effect. As a result, the present invention has been conceived.

That is, the mold casting method of the present invention is a mold casting method in which casting is performed while applying vibration to the molten metal during casting, and the cooling rate (A) of the molten metal in the solid-liquid coexistence region when vibration is not applied. When the ratio of the cooling rate (B) of the molten metal in the solid-liquid coexistence region when vibration is applied is (B / A), the acceleration of vibration is (B / A)> 1. The acceleration is such that 0 is obtained or higher, and the surface roughness of the cavity in contact with the molten metal is set to be equal to or higher than the surface roughness that provides (B / A)> 1.0.

  Here, the effect of vibration is that the adhesion between the molten metal and the cavity is improved by the vibration, and the contact area between the two increases, so that the vibration wave easily propagates to the molten metal and the heat from the molten metal to the cavity. It is presumed that the refinement / granulation of crystals is achieved by promoting the transfer (heat transfer). The improvement in the adhesion between the molten metal and the cavity and the promotion of heat transfer are thought to appear as an increase in the cooling rate of the molten metal, so the cooling rate of the molten metal was used as an evaluation index for vibration. However, since the cooling rate changes depending on the casting conditions such as the temperature of the metal material, the molten metal, and the mold, it was considered that the effect of vibration cannot be evaluated with the magnitude of the absolute value. Accordingly, the ratio (B / A) of the cooling rate (B) when the vibration is applied to the cooling rate (A) when the vibration is not applied is used as an evaluation index of the effect of the vibration. If the ratio (B / A) of the cooling rate exceeds at least 1.0, the cooling rate at the time of solidification of the molten metal becomes large (fast) by adding the vibration to the case where the vibration is not applied. Then, considering that the effect of vibration can be obtained, the vibration conditions for obtaining the cooling rate ratio (B / A)> 1.0 were examined.

  As a result of studying various vibration conditions such as vibration frequency, displacement, and acceleration, the present inventors have obtained knowledge that, among these vibration conditions, acceleration has a great influence on the cooling rate ratio (B / A). Thus, it was specified that the acceleration of vibration should be equal to or higher than the acceleration at which (B / A)> 1.0 is obtained. In addition to vibration conditions, the knowledge that the surface roughness of the contact surface on the cavity side at the interface where the molten metal and the cavity contact has a great influence on the cooling rate ratio (B / A) has been obtained, It was specified that the surface roughness of the cavity with which the molten metal comes into contact was equal to or greater than the surface roughness at which (B / A)> 1.0 was obtained.

In the mold casting method of the present invention, the molten metal is an aluminum alloy, the vibration acceleration is 100 to 2000 m / s ² , and the cavity surface roughness is 1 to 20 μm in terms of arithmetic average roughness (Ra). It is preferable to do. Although the metal material applied to the mold casting method of the present invention is not particularly limited, for example, various metals or alloys that can be conventionally used for castings such as aluminum alloys and magnesium alloys can be targeted. Among these, aluminum alloys are widely used as components for automobiles, railway vehicles, buildings, and the like. Therefore, if the mold casting method of the present invention is applied and the effect of improving the mechanical properties of the aluminum alloy is enjoyed, the contribution to society is great because it leads to weight reduction and resource saving. When vibration is applied to the molten aluminum alloy, the acceleration of vibration is defined as 100 to 2000 m / s ² , and the surface roughness of the cavity is defined as 1 to 20 μm in terms of arithmetic average roughness (Ra).

In the mold casting method of the present invention, it is preferable that the vibration is applied by a mechanical vibration type vibration means that performs a linear reciprocating motion. If a mechanical vibration type vibration means that performs a linear reciprocating motion is used as the vibration means, the acceleration of the vibration is an acceleration with a cooling rate ratio (B / A) exceeding 1.0, and the molten metal is an aluminum alloy. Easily obtains an acceleration of 100 m / s ² or more.

  The mold casting method of the present invention is a cavity in which the acceleration of vibration and the molten metal are in contact with each other as vibration conditions that significantly affect the cooling rate in the mold casting method in which casting is performed while applying vibration to the molten metal during casting. Since the surface roughness was found and the appropriate conditions were defined, the metal structure of the cast product was refined to reduce the shrinkage cavity, thereby improving the mechanical characteristics.

It is a graph which shows the relationship between the acceleration of a vibration, and the ratio of a cooling rate. It is a graph which shows the relationship between the surface roughness of the cavity which a molten metal contacts, and the ratio of a cooling rate. It is the schematic which shows an example of a structure of the casting apparatus which concerns on the metal mold | die casting method of this Embodiment. It is a figure which shows the cooling curve of the aluminum alloy which concerns on the metal mold | die casting method of this Embodiment. It is an optical microscope photograph which shows the microstructure of the aluminum alloy from which the acceleration of a vibration differs.

  Hereinafter, a die casting method as an example of an embodiment of the present invention will be described with reference to FIGS. FIG. 3 is a schematic diagram illustrating an example of a configuration of a casting apparatus according to the mold casting method of the present embodiment. In FIG. 3, a casting apparatus 1 includes a mold 2 formed in a separable manner, a cavity 3 for molding a cast product formed in the mold 2, a gate, a runner and a weir for injecting molten metal into the cavity 3. A plan part 4 comprising: a vibration means 5 which is attached to a part of the mold 2 and vibrates the mold 2 during casting to vibrate the molten metal; a base 6 on which the mold 2 is placed; Previously, a mold clamping means (not shown) for bringing the mold 2 from a separated state into a contact state, and a mold drawing means (not shown) for taking out a cast product after casting are provided. The mold 2 of the casting apparatus 1 includes a vibration measuring device 7 for measuring the acceleration of vibration and a molten metal injected into the cavity 3 in order to examine and evaluate the influence on the cooling rate due to vibration conditions to be described later. A thermocouple 8 for measuring the temperature during the cooling and solidification process, and a recorder (not shown) connected to the thermocouple 8 are installed. The cavity 3 and the plan part 4 are coated.

  Next, a cast product was cast using the casting apparatus 1 shown in FIG. 3, and the change in the cooling rate of the molten metal depending on whether vibration was applied to the molten metal was investigated. First, the casting in the case where vibration is applied to the molten metal will be described. The aluminum alloy of JIS AC4C, which becomes a cast product, is melted, while the mold 2 is heated to adjust its temperature to 420 ± 5 ° C., After making contact with the mold 2 formed in two by the mold clamping means, the vibration means 5 and the vibration measuring device 7 installed in the casting apparatus 1 were operated. Next, in a state where the vibration means 5 and the vibration measuring device 7 were operated, a molten metal whose pouring temperature was adjusted to 720 ± 5 ° C. was injected from the pouring gate of the design unit 4 to fill the cavity 3. After the molten metal was cooled and solidified, the vibration means 5 and the vibration measuring device 7 were stopped, and the cast product was naturally air-cooled, and then the cast product was taken out from the mold 2 by the mold releasing means. In casting, the temperature change of the molten metal cooled and solidified by the thermocouple 8 was measured and recorded on a recorder. On the other hand, with respect to casting when vibration is not applied to the molten metal, casting is performed under the same conditions as when vibration is applied to the molten metal except that the vibration means 5 and the vibration measuring device 7 are not operated, and the thermocouple 8 is cooled. -The change with time of the temperature of the molten metal to solidify was measured and recorded.

  FIG. 4 shows a cooling curve of the aluminum alloy according to the mold casting method of the present embodiment, obtained by measuring the temperature of the molten metal to be cooled and solidified in the above-described embodiment. In FIG. 4, the solid line represents the cooling curve of the aluminum alloy from the liquid phase to the solid phase when the vibration is applied and the broken line is the case where the vibration is not applied. Compared to the case where no vibration is applied to the molten metal in the entire temperature range from the liquid phase to the solid phase from FIG. 4, the time to reach the same temperature is shorter when the vibration is applied. I understand. From this, it was confirmed that the cooling rate was increased by applying vibration to the molten metal. The cooling rate was calculated from the cooling curve as the cooling rate (° C./sec) from the time difference during which the molten metal was cooled by a temperature difference of 25 ° C. from 605 ° C. to 580 ° C. in the solid-liquid coexistence region. In addition, when the casting and vibration conditions are the same, the cooling rate (B) when the vibration is applied is divided by the cooling rate (A) when the vibration is not applied and the ratio of the cooling rates (B / A ).

  Next, the results of investigations on the influence of the cooling rate on various vibration conditions such as vibration frequency, displacement, and acceleration, and the surface roughness of the contact surface on the cavity side at the interface between the molten metal and the cavity Will be described.

(Vibration acceleration)
In the above-described embodiment, casting was performed by applying vibration while changing the acceleration among the vibration conditions, and the acceleration was measured by the vibration measuring device 7. On the other hand, casting was performed without applying vibration under the same casting conditions. Regardless of whether or not vibration was applied, the cooling rate was obtained from the cooling curve measured and recorded for each casting, and the ratio (B / A) of the cooling rates was calculated. FIG. 1 is a graph showing the relationship between the vibration acceleration and the cooling rate ratio. As can be seen from FIG. 1, when the vibration acceleration is less than 100 m / s ² , the cooling rate ratio (B / A) does not change at about 1.0, and when the acceleration is 100 m / s ² or more, the cooling rate The change appears when the ratio (B / A) exceeds 1.0. It can be seen that when the acceleration is 100 m / s ² or more, the cooling rate ratio (B / A) increases as the acceleration increases.

Here, the effect of vibration was confirmed by observing the metal structure of the cast product having a cooling rate ratio (B / A) of around 1.0. FIG. 5 is an optical micrograph showing the microstructure of an aluminum alloy with different vibration accelerations obtained in the above embodiment. FIG. 5A shows the microstructure of the cast product with an acceleration of applied vibration of 80 m / s ² and a cooling rate ratio (B / A) of 1.0, and FIG. 5B shows the acceleration of 170 m / s ² and the cooling rate. The microstructure of a cast product having a ratio (B / A) of 1.3 is shown. 5A and 5B were cast with a mold having a cavity with which the molten metal contacts and a surface roughness of the coating surface of 7.5 μm. 5 (a) and 5 (b), the structure of (a) that gave the acceleration of the vibration with the cooling rate ratio (B / A) of 1.0 or less was the first to say that the vibration was applied. The size and shape of the crystal grains of the crystal 9 were not different from those in which the vibration was not applied, and the effect of vibration such as refinement and granulation of the crystal could not be obtained. On the other hand, in the structure of (b) that gave the acceleration of vibration exceeding the cooling rate ratio (B / A) of 1.0, the crystal of the primary crystal 9 was refined and granulated, and the effect of vibration was confirmed. It was done. From the above, in the mold casting method in which casting is performed while applying vibration to the molten metal during casting, when the ratio of the cooling rate of the molten metal in the solid-liquid coexistence region depending on whether vibration is applied is (B / A) In addition, it was confirmed that the acceleration of the vibration may be set to be equal to or higher than the acceleration at which (B / A)> 1.0 is obtained. The acceleration at which (B / A)> 1.0 is obtained varies depending on physical properties such as the specific gravity, surface tension, and viscosity of the molten metal material to be cast. According to the present embodiment, for a metal material to be cast, an appropriate vibration acceleration can be obtained by grasping the relationship between the vibration acceleration and the cooling rate ratio.

Here, in the aluminum alloy of the present embodiment, in order for the cooling rate ratio (B / A) to exceed 1.0, the vibration acceleration is set to 100 m / s ² or more. As can be seen from FIG. 1, the ratio of the cooling rate (B / A) also increases in proportion to the acceleration. Therefore, it is effective to increase the acceleration in order to make the vibration effect more remarkable. However, as the acceleration is increased, the acceleration applied to the casting apparatus etc. also increases. The load due to vibration is accumulated in peripheral devices such as the mold body, casting device, and die-cutting device, and problems such as device failure occur. Further, in order to increase the acceleration, in order to apply a strong vibration, the vibration means is enlarged and the manufacturing cost is increased. Therefore, considering the load on the casting apparatus or the like, it is necessary for the acceleration of vibration to have an upper limit of 2000 m / s ² for stable casting. If the acceleration is 2000 m / s ² or less, problems such as a failure of the casting apparatus and the like hardly occur, and stable operation is possible by regularly inspecting and maintaining the casting apparatus and the like. It should be noted that it is desirable to install a device or equipment having low durability against vibrations at a position as far as possible from the vibration means or to provide a buffer means. From the above, in the metal mold casting method of the present invention, when the melt was melt of an aluminum alloy, the acceleration of the vibration is preferably in the 100-2000 m / s ^2, and 105~1000m / s ² It is more preferable.

(Surface roughness of the cavity where the molten metal contacts)
In the aluminum alloy of the present embodiment, the acceleration of vibration is made constant at an arbitrary value of 100 m / s ² or more, and the surface roughness of the contact surface on the cavity side at the interface between the molten metal and the cavity is changed, Similar to the acceleration of vibration described above, the ratio (B / A) of the cooling rate depending on whether or not vibration was applied was calculated. FIG. 2 is a graph showing the relationship between the ratio of the surface roughness of the cavity in contact with the molten metal and the cooling rate when the vibration acceleration is 420 m / s ² (broken line) and 860 m / s ² (solid line) as an example. It showed in. The surface roughness is the arithmetic average roughness (Ra). As can be seen from FIG. 2, when the surface roughness of the cavity in contact with the molten metal is less than 1 μm, the cooling rate ratio (B / A) does not change at about 1.0, and when the surface roughness becomes 1 μm or more, The change appears when the ratio of cooling rates (B / A) exceeds 1.0. It can be seen that when the surface roughness is 1 μm or more, the ratio (B / A) of the cooling rate increases as the surface roughness increases. It can also be seen that if the surface roughness is the same, the ratio of the cooling rate (B / A) increases as the vibration acceleration increases. From the above, in the mold casting method in which casting is performed while applying vibration to the molten metal during casting, when the ratio of the cooling rate of the molten metal in the solid-liquid coexistence region depending on whether vibration is applied is (B / A) In addition, it is understood that the surface roughness of the cavity with which the molten metal comes into contact may be equal to or greater than the surface roughness that provides (B / A)> 1.0. In the aluminum alloy of the present embodiment, in order for the cooling rate ratio (B / A) to exceed 1.0, the surface roughness of the cavity in contact with the molten metal is 1 μm or more in terms of arithmetic average roughness (Ra). To do.

As can be seen from FIG. 2, the ratio of the cooling rate (B / A) increases in proportion to the surface roughness of the cavity with which the molten metal comes into contact. Therefore, in order to make the vibration effect more remarkable, the surface roughness is increased. It is effective to do. Although the upper limit of this surface roughness is not specifically limited, What is necessary is just to determine based on the surface roughness of the casting surface requested | required of a casting. In general, in the mold casting method, the surface of the mold that comes into contact with the molten metal, such as the mold cavity or the design part, is improved in gas venting, protected from the molten metal by insulation and coating, and removed from the molten metal. Coating is applied for the purpose of improving hot-water flow by suppressing heat and preventing galling by reducing mold release resistance during mold removal. When the mold is coated, the surface roughness of the cavity with which the molten metal contacts is the surface roughness of the coating surface. When vibration is applied to the coated mold, the casting surface and the casting mold are changed from the liquid phase to the solid phase as the surface roughness of the coating surface, that is, the surface roughness of the cavity in contact with the molten metal referred to in the present invention increases. The frictional force increases. Due to the increase in the frictional force, wear of the coating mold and peeling from the mold are likely to occur. The wear and delamination of the coating mold cause seizure between the molten metal and the mold and galling at the time of die-cutting, making stable continuous casting difficult. In the aluminum alloy of the present embodiment, when the mold is applied with a vibration acceleration of 100 m / s ² or more, the surface roughness of the cavity in contact with the molten metal (that is, the surface roughness of the mold surface in this case) is When it exceeds 20 μm, the wear and peeling of the coating mold become remarkable, which is not preferable. From the above, in the mold casting method of the present invention, when the molten metal is made of an aluminum alloy and the mold is coated, the surface roughness of the cavity with which the molten metal comes into contact is the arithmetic average roughness (Ra 1) to 20 μm, and more preferably 2 to 10 μm.

  When the lower limit of the surface roughness is 1 μm, even if there is a coating mold, the frictional force between the casting and the coating mold is small, so that wear and peeling do not pose a problem. Therefore, the lower limit value of the surface roughness is defined regardless of the presence or absence of the coating mold. Further, in place of the coating mold, it is possible to give the mold the same function as the coating mold by subjecting the mold to surface treatment or formation of irregularities (for example, embossing). If surface treatment or unevenness formation is performed on the mold itself, wear and delamination are less likely to occur compared to the coating mold, so that the surface roughness of the cavity with which the molten metal contacts can be increased. In that case, even in the above-described aluminum alloy, the upper limit of the surface roughness can be specified to 20 μm or more.

(Mechanical vibration type vibration means for linear reciprocating motion)
As the vibration means, there are types such as an ultrasonic vibration type, an electromagnetic vibration type, and a mechanical vibration type depending on a generation source of vibration. The ultrasonic vibration type and electromagnetic vibration type are expensive, and a large power supply is required to vibrate heavy objects such as casting molds. As a result, the equipment cost increases and the manufacturing cost increases. On the other hand, the mechanical vibration type is advantageous in that it is inexpensive and excellent in durability because the structure of the vibration device is relatively simple compared to the ultrasonic vibration type and electromagnetic vibration type. Mechanical vibration type vibration devices include a type in which eccentric weights are rotated by a motor, a type in which eccentric weights and balls are rotated by compressed air, a type in which weights in a cylinder are linearly reciprocated by compressed air, etc. is there. Among these, in order to give a large acceleration to a heavy object such as a metal mold, a vibration device of a type that reciprocates linearly is advantageous. Therefore, in the mold casting method of the present invention, the vibration is preferably applied by a mechanical vibration type vibration means that performs a linear reciprocating motion.

As mentioned above, although an example of typical embodiment of this invention was demonstrated, this invention is not limited to embodiment mentioned above, It can change in the range which does not deviate from the summary of invention. In particular, in the vibration means, the type of the vibration device and the portion to be installed are not limited to the type of the vibration device described above or the portion illustrated in FIG. 3, and in short, the acceleration of vibration defined in the present invention can be obtained. Any configuration may be used. For example, in this embodiment, the vibration is applied to the entire mold. However, a part of the mold may be a nesting system, and the vibration may be applied only to the nesting. If vibration is applied only to the nest, the cooling rate of the molten metal in the solid-liquid coexistence region can be locally changed, which is effective in preventing shrinkage.

1: Casting device 2: Mold 3: Cavity 4: Plan part 5: Vibrating means 6: Base 7: Vibration measuring device 8: Thermocouple 9: Primary crystal

Claims (3)

In the mold casting method in which casting is performed while applying vibration to the molten metal during casting, the cooling rate (A) of the molten metal in the solid-liquid coexistence area when vibration is not applied and the solid-liquid coexistence area when vibration is applied When the ratio of the cooling rate of the molten metal (B) to the cooling rate (B / A) is (B / A), the acceleration of vibration is not less than the acceleration at which (B / A)> 1.0 is obtained, and the molten metal is A die casting method characterized in that the surface roughness of the contacting cavity is equal to or greater than the surface roughness that provides (B / A)> 1.0. The molten metal is an aluminum alloy, wherein the vibration acceleration is 100 to 2000 m / s ² , and the surface roughness of the cavity is 1 to 20 μm in terms of arithmetic average roughness (Ra). 2. The mold casting method according to 1.   3. The mold casting method according to claim 1, wherein the vibration is applied by a mechanical vibration type vibration means that performs a linear reciprocating motion.