JPS6076266A - Die and its production - Google Patents

Abstract

PURPOSE:To obtain a die having improved gas permeability by sintering metallic powder or a mixture composed of the metallic powder and ceramic powder to a part from the inside surface of the die up to the outside surface. CONSTITUTION:Metallic powder alone which passes a 65-mesh screen or a mixture composed of said powder and <=50wt% ceramic powder is packed into the cavity 2 of a mold 1 for forming a die. The powder 3 is heated and sintered in an inert gaseous atmosphere and is parted from the mold after the molding is allowed to cool. A die 4 of a sintered body is thus manufactured. The die 4 is constituted at least partly of the sintered body of the powder 3 and has high gas permeability and therefore the gas in the stage of casting is easily vented through the inside of the die 4 and sure and smooth venting of the gas is thus made possible.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention dramatically improves air permeability, which is widely used in casting molds for die casting, plastic molds, and pouring molds for refractories. [Prior Art] In mold casting, as molten metal is poured into the mold, air in the mold cavity must be quickly removed from the mold. No. In addition, it is also necessary to quickly remove water vapor and carbon dioxide scum generated by the mold. If the removal of gases such as air is insufficient, gas may be trapped in the molten metal and remain, resulting in so-called gas inclusion defects, or molten metal not filling all of the cavities of the mold, resulting in voids, resulting in so-called filling defects. etc. will occur. For this reason, conventionally, various means for venting gas have been abandoned, such as providing an air vent section with a small hole communicating with the outside near the parting surface of the mold. However, with the method of providing an air vent, after casting, small protrusions (firmness) remain in the vicinity of the part corresponding to the air vent part of the cast body, and the air vent part generally has pores of about 3 to 5τ. Therefore, problems such as clogging and inability to handle gas may occur. Also, it is not possible to install an air vent section in any part of the mold, so it is difficult to install it! There are many ljj terms. In particular, if the shape of the mold is complex, the restrictions will be severe.

Further, when the mold cavity is deep, it is necessary to install a large number of air vent sections, but it may be difficult to install a large number of air vent sections due to the limitations of the mold. As described above, depending on the installation of the air vent section, degassing cannot always be solved satisfactorily in many cases.

In special cases, as seen in vacuum die-casting technology, degassing is performed by forcibly sucking out the gas in the cavity from one part of the mold through an interlockable valve. has also been adopted. however,
In this method, the gas inside the cavity is not necessarily 7+'ii
In fact, not all of it is necessarily discharged, and it has the disadvantage of being inferior in reliability.

[Purpose of the invention]

An object of the present invention is to provide a mold that allows smooth and reliable degassing, and a simple manufacturing method thereof.

[Structure of the invention]

The present inventors (1. Conventional molds are generally cast iron, casting 1.1,
Focusing on the fact that the mold is made of metals such as graphite cast iron, chromium molybdenum, molybdenum, etc., and is made of a material that allows gas to pass through the inside of the mold, it is possible to use a mold made of a material that allows gas to easily penetrate and diffuse. For example, the present invention was completed based on the idea that the gas in the cavity can be discharged from the mold itself, and sufficient degassing can be performed.

That is, in the mold of the present invention, at least a portion of the mold that reaches from the mold inner surface to the mold outer surface is made of powder f'3b solids.
In addition, the method for manufacturing the mold of the present invention is a method for manufacturing the mold of the present invention described above, and is characterized by the following: A core forming a cavity and a member forming a part of a mold are arranged as necessary, and the powder is filled, the powder is sintered, and then the mold is released. The feature is to manufacture a mold that includes at least a part of the sintered body.

Conventional molds, such as cast steel molds, are usually manufactured by pouring molten metal into the mold and solidifying it, and in its internal structure, the metal densely occupies the air IHj with almost no voids. Therefore, it is almost impossible to effectively infiltrate and diffuse gas such as air into the mold. On the other hand, the mold of the present invention has an internal structure similar to that of a sintered body of powder, in which powder particles adhere to each other, and many voids are present. exists continuously. Therefore, gas such as air can easily pass through the interior of the mold of the present invention through the holes. That is, the mold of the present invention has high air permeability, and can achieve the above-mentioned high air permeability by simply configuring at least a portion of the mold from the inner surface of the mold to the outer surface of the mold with a sintered powder. Provides breathability. In order to obtain high air permeability, regardless of the type of powder, it is sufficient that a large number of continuous pores, which serve as gas passages, are formed.

Any sintered body of metal powder, ceramic powder, powder of other materials, or mixed powder thereof may be used. Furthermore, the larger the particle size of the powder, the more highly breathable the mold can be obtained.

In general, it is desired that the mold has a smooth inner surface so that the surface condition of the molded product is good when molded using the mold, and that it is hard and durable enough to be molded many times.

From these points, the sintered body is preferably a sintered body of metal powder with high surface smoothness and high rigidity. in particular,
Sintered powders of iron, iron alloys, nickel alloys, aluminum alloys, copper alloys, etc. are preferred.

Further, the metal powder and, for example, silicon carbide (SIC)
, silicon nitride (Si3N, ), alumina (At20
A mixture of ceramic powders such as 3) (however, the proportion of the ceramic powders is 50% or less) is also suitable. Although sintered bodies containing only ceramic powder and sintered bodies containing metal and ceramic mixed powders containing more than 50% by weight of ceramic powder have high air permeability, Table 0
``It is inferior in properties and durability. In addition, in the same way as above, it is preferable that the powder is a fine powder that passes through a sieve of 065 sieve.The surface of the sintered body is It may become rough and cannot be molded into a molded product with a good surface condition, or it may become brittle and the durability cannot be compromised.

As mentioned above, the mold manufacturing method of the present invention involves zero-mold casting, which is a method in which a fire-resistant mold is completely filled with powder, the powder is sintered, and then the mold is released. It consists of complex processes such as , molten metal preparation, and casting. Furthermore, there are generally many restrictions on the design of a mold, such as restrictions on the shape of the cavity, etc., and there are certain limitations on the shape of the mold that can be manufactured. Additionally, they are typically manufactured using large mold casting machines and are generally expensive to manufacture. In contrast, the manufacturing method of the present invention is a simple method that involves a single process of sintering. Furthermore, because of the sintering process, there are no strict restrictions on mold design, and molds with complex shapes can be easily manufactured. moreover,
Since it is based on a sintering process, manufacturing costs are also relatively low. In this case, the mold for molding must not only be able to withstand high-temperature heating during sintering, but also have extremely small changes in length and volume even when heated to high temperatures (temperatures below the melting point of the powder). I can't believe it. If the change in length or volume is large, a mold with a predetermined shape cannot be made accurately, making it unsuitable for manufacturing molds.

In this respect, fire-resistant molds are suitable, and among these molds, molds made of fire-resistant ceramics have excellent fire resistance and are very preferable. Specific examples include the so-called Shaw process and the new cast mold.

〔Example〕

The present invention will be explained below using examples.

Example 1 First, a fire-resistant mold f4' as shown in FIGS. 1 and 2 was prepared. The mold 1 for mold forming is an example of a mold used in a so-called "Nyo process" which is generally used for manufacturing casting molds. Then, into the cavity 2 of this mold 1, a powder filter of metal powder that passes through a 250 mesh sieve is uniformly and densely filled using a pie break or the like.
In an atmosphere of inert gas (Ar gas, etc.), heating was continued for 5 hours at 1200°C for sintering, and after cooling, the mold was released from the mold 1 to form a sintered body as shown in Figure 3. Mold 4 was manufactured.

Examples 2 to 5 Powder 6 of metal powder passing through six sieves of 200 mesh, 100 mesh, 65 mesh, and 45 mesh was filled into a fire-resistant metal mold forming mold 1 in the same manner as in Example 1. , sintered, and then released from the mold to produce molds 4 in which the powder 3 had different particle sizes.

Examples 6 to 9 Mixed powder 3 of metal powder that passes through a 200 meso sieve and easily available ceramic powder that passes through a 325 meso 7 sieve,
The weight ratio of both is 2so:2o.

60:40. so: so, 40:/) 0, and filled into the mold 1 for mold forming, and through the same sintering process as in Example 1, molds 4 having different mixing ratios were manufactured.

Examples 10-13 Example 10 ~1
6 molds 4 were manufactured.

[Test example]

Regarding Experimental Examples 1 to 16 and conventional @-made molds, the air permeability, surface texture, rigidity, bulk specific gravity, etc. were investigated. The air permeability was determined by installing a neglected box-shaped chamber 5 on top of the mold 4, blocking the intake hole 6 at the bottom of the chamber, and connecting it to the exhaust hole 7 at the top of the chamber, as shown in Fig. 4. This was determined by evacuating the air in the chamber 5 using a vacuum pump (not shown) with an exhaust capacity of 3 ooot/min, and measuring the degree of vacuum in the chamber 5 when equilibrium was reached. It can be said that the higher the degree of pressure reduction, the lower the air permeability of the mold 4. These measurement results Table 1: ◎Very good ○Sufficiently good △Good In other words, it can be seen that it has a high ventilation pressure. It can also be seen that the larger the particle size of the powder 3, the higher the air permeability. On the contrary, it can be seen that the larger the particle size of the powder, the worse the surface quality and rigidity, and the poorer the coarse powder that cannot pass through a 65-mesh sieve. It can also be seen that as the proportion of ceramic powder increases, the surface quality and rigidity deteriorate, and when it exceeds 50%, it becomes poor.

As can be seen from the above description, the mold of the present invention is composed at least in part of a sintered body of powder and has good air permeability, so that gas removed during casting passes through the inside of the mold. Although it is not easy to extract the gas, the gas can be removed smoothly and without any lead, and the above-mentioned occurrence of paris and clogging of the air vent part 9 are eliminated. 1. The mold manufacturing method of the present invention is a method of manufacturing a mold by sintering the powder filled in a durable metal mold forming mold, and the above-mentioned excellent mold can be manufactured by Not only can it be provided, but compared to conventional mold casting, etc., it is simple and easy to manufacture, even molds with complicated shapes, and the manufacturing cost is relatively low.

[Brief explanation of drawings]

FIG. 1 is a plan view showing an example of a powder-filled mold for large-sized objects, FIG. 2 is a sectional view taken along the river-■ line in FIG. 1, and FIG. FIG. 4 is a perspective view showing the example, and is a diagram showing a state in which the air permeability of the mold shown in FIG. 3 is measured. In the figure, 1...Mold forming mold 6...Powder 4...Mold. Figure 1 Figure 1 Figure 3 Figure 4

Claims (1)

[Scope of Claims] (1) A mold used for casting, etc., characterized in that at least a portion of the mold, which reaches from the inner surface of the mold to the outer surface of the mold, is composed of a solid body of powder. . (2) The mold according to claim 1, characterized in that the mold is made by using metal powder as the powder. (3) A mixture of all 1-width powder and ceramic powder in the powder (however, the blend of the ceramic powder is 50% by weight or less)
The mold described in item 1 of the patented HD license scope, characterized in that it is made by using. (4) Fine powder f passing through a 65-menonyu sieve:
The mold according to claim 1, characterized in that it is made by using the mold. (5) Place a core forming a cavity and a part forming a part of the mold as necessary in Colonel I's mold forming mold, fill it with powder, and fill it with powder. A method for manufacturing a mold, characterized in that the mold includes at least a part of the sintered body of the powder by sintering the powder and then releasing the mold. 6) The method of manufacturing a mold according to claim 5, characterized in that a mold forming mold made of refractory ceramic is used.