JPH055259U - Low pressure casting mold - Google Patents

Abstract

(57) [Abstract] [Purpose] Casting a sound casting with no casting defects by directionally solidifying the molten metal without causing thermal fatigue cracking of the die itself due to direct contact of cooling water with the die surface. A mold for low pressure casting capable of being obtained is obtained. [Structure] In a portion of the mold 1 where a temperature gradient is to be provided, a cooling water flow pipe 3 for passing cooling water is provided in the vicinity of the cavity along the same, and a high thermal conductivity is provided between the cooling water flow pipe 3 and the mold surface. The heat-transfer cement 4 as a filler is disposed so as to be sandwiched.

Description

[Detailed description of the device]

[0001]

[Industrial application]

 The present invention relates to a low-pressure casting mold used for low-pressure casting of an aluminum alloy or the like, and more specifically, to a mold surface without causing thermal fatigue cracking of the mold itself due to direct contact of cooling water with the mold surface. The present invention relates to a low-pressure casting mold in which high-quality cast products can be obtained by eliminating casting defects by directionally solidifying the poured molten metal.

[0002]

[Prior Art]

 As is well known, in the low-pressure casting method, a molten metal holding crucible 52 provided in a closed holding furnace 51 is used to store molten metal by using an apparatus as shown in FIG. The molten metal surface is pressurized with a gas body or air pressurized with a relatively low pressure of, and the molten metal in the molten metal holding crucible 52 is pushed up in the direction opposite to gravity through the hot water supply pipe 53 (stoke), and the holding furnace 51 Is a method in which the casting is performed by pouring the molten metal into the cavity 55c of the die 55, which is arranged on the die plate 54 provided above the die 55 and is composed of the upper die 55a and the lower die 55b. . In FIG. 5, 56 is an upper frame, 57 is a mold clamping cylinder, 58 is a movable platen, and 59 is an extruding plate, which constitute a mold operating mechanism.

In such a low-pressure casting method, solidification is sequentially started from the molten metal in contact with the mold of the final filling portion, so-called directional solidification occurs, and casting defects such as shrinkage cavities and blowholes are less likely to occur, The feature is that a dense and sound casting can be obtained.

However, depending on the shape of the casting to be cast, the molten metal does not necessarily solidify in order from the final filling portion to the sprue, and a thin portion exists in the cavity between the final filling portion and the sprue. In the case where there is a thick portion, conversely, the heat balance for causing the directional solidification of the molten metal is lost, and defects are likely to occur in the cast product.

Therefore, in order to impart a temperature gradient in the mold for the purpose of directional solidification of the molten metal, a low-pressure casting mold provided with a cooling water passage for passing cooling water or an air passage for passing compressed air is provided. Are known.

[0006]

[Problems to be solved by the device]

 However, in a conventional low-pressure casting mold in which a cooling water passage is provided in the mold, since water directly contacts the mold surface, cracks may occur in the mold due to thermal fatigue, and water cooling may occur. It has the disadvantage that the die life is shorter than that of the case where no heat treatment is applied, and the inspection work for checking the presence or absence of thermal fatigue cracking also takes time. Also, in order to avoid thermal fatigue cracking of the mold, if a cooling water passage is provided at a position far from the cavity in the mold, the mold will be cooled over a wide area as well as the part where the temperature gradient should be applied. As a result, the running property of the molten metal deteriorates.

On the other hand, in a conventional low-pressure casting mold in which an air passage is provided in the mold, it is possible to cool a portion of the mold where a temperature gradient is to be given, but the cooling capacity is cooling water. Since it is inferior to the one provided with a passage, it takes time to cool the molten metal for directional solidification, and when used in a low-pressure casting apparatus, the cycle time required for one shot is long and the productivity is poor.

This invention has been made in order to solve the above-mentioned drawbacks, and indirectly uses water having a large cooling capacity as a cooling medium in a portion of the mold where a temperature gradient is to be given. By enabling efficient cooling, the molten metal is directionally solidified without causing thermal fatigue cracking of the mold itself due to direct contact of cooling water with the mold surface, and a sound casting with no casting defects can be performed. It is an object of the present invention to provide a die for low pressure casting that can obtain a casting.

[0009]

[Means for Solving the Problems]

 In order to achieve the above object, the low-pressure casting mold according to the present invention pushes up the molten metal stored in a closed container through a hot water supply pipe in the direction opposite to gravity by pressurizing the molten metal surface with a pressurized gas. , In the mold used in the low-pressure casting method in which the molten metal is poured into the cavity of the mold located above the closed container for casting, the part in the mold where temperature gradient should be Along with this, a cooling water flow pipe for passing cooling water is arranged with a filler having a high thermal conductivity interposed between the cooling water flow pipe and the mold surface.

[0010]

[Action]

 When the cooling water flows in the cooling water flow pipe, heat is taken from the vicinity of the cavity in the portion where the temperature gradient is to be given in the mold through the filler having high thermal conductivity, and the mold is cooled. The part to be subjected to the temperature gradient is cooled indirectly without the cooling water coming into direct contact with the mold surface. Thereby, the molten metal can be directionally solidified without causing thermal fatigue cracking. In this case, since the cooling water flow pipe is disposed with the filler having a high heat conductivity interposed between the cooling water flow pipe and the mold surface, a gap is formed between the outer peripheral surface of the cooling water flow pipe and the mold surface. It is closely attached through the filling material without being generated and is efficiently cooled indirectly. Examples of the filler having such a high thermal conductivity include heat transfer cement having a thermal conductivity of about 8 to 10 Kcal / min · h · ° C.

[0011]

【Example】

 The present invention will be described below based on embodiments. In this embodiment, a low-pressure casting mold for low-pressure casting of aluminum wheel disc parts and casting results using the same will be described including a comparative example and a conventional example. FIG. 1 is a sectional conceptual view for explaining the structure of a die for a low pressure casting machine according to an embodiment of the present invention, FIG. 2 is an enlarged sectional view of an essential part of FIG. 1, and FIG. 3 is a cooling water distribution pipe shown in FIG. Is a plan view and FIG. 4 is a side view thereof.

1 and 2, 1 is a lower mold body, 1a is a spout as a cavity thereof, 2 is a short cylindrical cooling water flow pipe having a flange portion at one end side (lower side in FIG. 1) It is a fixed body. A semicircular concave surface corresponding to the outer peripheral surface of an annular cooling water distribution pipe 3 described later is formed along the circumference of the upper end peripheral portion of the cooling water distribution pipe fixed body 2. Around the sprue part 1a of the lower mold body 1, a semicircular concave surface corresponding to the outer peripheral surface of the cooling water distribution pipe 3 and the cooling water distribution pipe fixing body 2 are provided close to the sprue part 1a. A space corresponding to the shape is provided.

Then, in this embodiment, heat transfer having a thermal conductivity of about 8 to 10 Kcal / min.multidot.h.degree. C. is applied to the surfaces of the semicircular concave portions of the cooling water flow pipe fixing body 2 and the lower mold body 1. The cement 4 is thinly applied, and the cooling water flow pipe fixing body 2 in a state in which the cooling water flow pipe 3 is arranged on the applied heat transfer cement 4 is fitted into the lower mold body 1, and the lower metal mold is fixed by a bolt (not shown). The structure is fixed to the mold body 1.

As shown in FIGS. 3 and 4, the cooling water flow pipe 3 is formed in an annular shape by using a stainless steel pipe in this embodiment, and the cooling water flow pipe 3 is formed at the opposite portion thereof. A cooling water inlet pipe 5a for guiding the cooling water to and a cooling water discharge pipe 5b for discharging the water from the cooling water distribution pipe 3 are connected to each other.

A lower mold having the above structure and a corresponding upper mold (not shown) are set in a low-pressure casting apparatus, and the size is about 440 mm, the weight is about 5 kg, and Al-Si-Mg is about 5 kg. We performed low pressure casting of aluminum wheel disc parts made of aluminum alloys. For comparison, as Comparative Example 1, the cooling water flow pipe 3 is arranged in the lower mold without sandwiching the heat transfer cement 4 between the mold surface, and as Comparative Example 2 in the lower mold. A disk component of the above-mentioned aluminum wheel was manufactured by preparing a cooling water flow passage in which cooling water is in direct contact with the mold surface, and a conventional mold in which an air passage is provided in the lower mold. Low pressure casting was also performed. Table 1 shows the casting results obtained by each low pressure casting mold.

[0016]

[Table 1]

As shown in Table 1, when the low pressure casting mold according to Comparative Example 2 is used, it is possible to directionally solidify the molten metal and eliminate casting defects such as shrinkage cavities and blow holes. However, as mentioned above, there is a risk of thermal fatigue cracking in the mold, and the mold life is short. When the low pressure casting mold according to Conventional Example 1 is used, the molten metal is directionally solidified to eliminate casting defects and there is no risk of thermal fatigue cracking in the mold, but water is used as the cooling medium. Since the cooling ability is lower than that of the ones, it takes time to cool the molten metal for directional solidification, and the cycle time required for one shot becomes long, resulting in poor productivity.

On the other hand, in the case of using the mold for low pressure casting in which the cooling water flow pipe 3 is arranged without sandwiching the heat transfer cement 4 having a high thermal conductivity between the mold surface according to Comparative Example 1 and Has no risk of thermal fatigue cracking in the mold, but a gap may be created between the cooling water flow pipe 3 and the mold surface, so that the molten metal can be reliably directionally solidified. Instead, defects may occur in the cast product.

On the other hand, in the case of using the low-pressure casting mold according to the embodiment of the present invention, the cooling water is provided in the vicinity of the cavity along the portion of the mold where a temperature gradient is to be given. Since the heat transfer cement 4 is disposed between the flow pipe 3 and the mold surface, the mold surface and the cooling water flow pipe 3 are adhered to each other via the heat transfer cement 4 without forming a gap. Now, the portion of the mold where a temperature gradient is to be applied is efficiently and indirectly cooled without the cooling water coming into direct contact with the mold surface. As a result, there is no thermal fatigue cracking of the die itself due to direct contact of the cooling water with the die surface for a sound casting in which the molten metal is directionally solidified and has no casting defects. It became possible to cast with high productivity.

[0020]

[Effect of the device]

 As described above, in the low-pressure casting mold according to the present invention, a cooling water flow pipe for passing cooling water is provided in the vicinity of the cavity along the portion of the mold where a temperature gradient is to be imparted. Since the filler having a high thermal conductivity is sandwiched between the mold surface and the cooling surface, the mold surface and the cooling water flow pipe are closely contacted with each other through the filler without any gap. Without causing thermal fatigue cracking of the mold itself due to direct contact of the cooling water with the mold surface, indirectly using a water with a large cooling capacity as the cooling medium in the part where a temperature gradient is to be applied in the mold Can cool well.

Thus, by performing low-pressure casting by the low-pressure casting device using the low-pressure casting mold according to the present invention, a sound casting in which the molten metal is directionally solidified and has no casting defects can be obtained by the above-mentioned heat treatment of the mold itself. Since there are no fatigue cracks, it is possible to cast with good productivity in a short cycle time with a long mold life.

[Brief description of drawings]

FIG. 1 is a schematic sectional view for explaining the structure of a die for a low pressure casting machine according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a main part of FIG.

FIG. 3 is a plan view of the cooling water flow pipe shown in FIG.

FIG. 4 is a side view of the cooling water flow pipe shown in FIG.

FIG. 5 is a structural explanatory view of a low pressure casting apparatus.

[Explanation of symbols]

1 ... Lower mold body 1a ... Gate part 2 ... Cooling water distribution pipe fixed body 3 ... Cooling water distribution pipe 4 ... Heat transfer cement 5a ... Cooling water introduction pipe 5b ... Cooling water discharge pipe

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kazuhiko Oku, 3-chome, Momogaoka, Komaki 39-11 (72) Koichi Ozaki 2-183, Kitamatsuyama-cho, Seto

Claims (1)

[Claims for utility model registration] [Claim 1] The molten metal stored in the closed container is pushed up through the hot water supply pipe in the direction opposite to gravity by pressurizing the molten metal surface with a pressurized gas, and above the closed container. In a mold used in a low-pressure casting method in which molten metal is poured into a cavity of a mold to be cast, cooling water is provided in the vicinity of the cavity along a portion of the mold where a temperature gradient is to be given. A low-pressure casting mold, characterized in that a cooling water flow pipe for passing through is arranged with a filler having a high thermal conductivity sandwiched between the mold surface and the mold surface.