JPH0237937A - Precision casting method for casting having narrow mouth hollow part - Google Patents

Abstract

PURPOSE:To mold a molding shell having excellent collapsibility without any breakage and crack and to manufacture a sound casting without any defect by arranging dissolvable resin at narrow mouth hollow body made of wax pattern and further, filling up the hollow part with ceramic. CONSTITUTION:Refractory is coated on the surface of the wax pattern 11 having the narrow mouth hollow body 12 to form coating layer and after drying, the dissolvable resin 14 vertically attached to a core metal 15 is arranged in the hollow part 12 as penetrating the hollow part 12. After that, the fluidized ceramic 16 is poured into the hollow part 12, to fill up the hollow part 12 with this ceramic 16. Successively, after drying and hardening this ceramic, dewax treatment is executed with heating and the wax pattern 11 surrounded with the coating layer 13 is dissolved, vaporized and removed. Then, the molding shell for becoming pouring space is formed at the area, where the wax pattern 11 possesses. The whole body containing this molding shell is heated at the prescribed temp. to execute burning treatment and the coating layer is hardened and also the dissolvable resin 14 is dissolved, vaporized and lost. This mold is preheated and the prescribed molten metal is poured to manufacture the casting.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention applies to investment (
TECHNICAL FIELD The present invention relates to a method for casting a casting having a narrow hollow part by a lost wax process in investment) casting.

[Conventional technology] The lost wax method is the most typical precision casting method.
Due to its excellent cast surface and dimensional accuracy, it is widely used in industrial machinery, automobiles, telecommunications equipment, and aircraft parts.

FIG. 2 is a schematic diagram conceptually showing each step of this lost wax method. First, in step 1, a wax mold is obtained by injecting a brazing material. Then, in step 2, this wax mold is assembled to obtain a wax pattern, and then in step 3, it is immersed in slurry, and in step 4, it is sprinkled with sand as a refractory material, coated with refractory material, and dried. let This slurry dipping and refractory coating are repeated to form a mold layer of a predetermined thickness.

In the solid mold method, step 5a
In step 6a, the area around the refractory material mold layer is filled and backed up, and in step 6a, the wax is heated to remove wax, and the wax is completely burned and removed.

Next, in step 7a, molten metal is injected and left until solidification is completed.

Then, in step 8, the product is sanded, cut, and finished to obtain a product as shown in step 9.

In addition, in the ceramic shell mold method, as shown in step 5b, without backup processing,
As shown in step 6b, the molten metal is heated to perform dewaxing treatment, and then, in step 7b, the molten metal is poured.

[Problems to be Solved by the Invention] However, in the conventional casting method, in the case of a casting having an elongated cast hole or a casting having a blind hole, slurry and refractory material are deposited on the inner surface of these holes. It doesn't stick well and doesn't dry out easily.

As a result, the strength of the mold decreases, and the mold may break during dewaxing and firing, or the mold may not be able to withstand the thermal shock during casting of molten metal, and cracks may occur in the narrow hollow part, leading to leakage or Penetration is likely to occur, making it impossible to obtain a sound casting.

Techniques have also been proposed in which the above-mentioned drawbacks are solved by using a ceramic mold in the narrow hollow part or by injecting Ceracola into the narrow hollow part, but ceramic molds are expensive and The as-cast properties are also poor. Furthermore, with Ceracola, the above-mentioned disadvantages of insufficient mold strength and cracks occurring during dewaxing or firing processes, making it difficult to produce sound castings, cannot be overcome, and it takes a long time to dry. There is also a drawback.

As mentioned above, in the conventional lost wax casting method, it is extremely difficult to manufacture a casting having a narrow hollow part.

The present invention has been made in view of such problems, and includes:
It is possible to create a mold with no cracks in the narrow hollow part and excellent moldability, and it is possible to produce defect-free castings stably, quickly, and at low cost without causing any leakage. An object of the present invention is to provide a precision casting method for a casting having a narrow hollow part.

[Means for Solving the Problems] A precision casting method for a casting having a narrow hollow according to the present invention includes a step of applying a mold layer to the surface of a wax mold having a predetermined shape and having a narrow hollow. A step of inserting a fusible resin into the part, a step of filling the narrow hollow part with ceramics, a step of dewaxing, and a step of firing the mold layer and disappearing the fusible resin. and a step of injecting a predetermined molten metal.

[Function] In the present invention, after the fusible resin is placed so as to be inserted into the narrow hollow part of the wax type, the narrow hollow part is filled with ceramics. Next, after dewaxing, the mold layer that covers the wax mold is fired. is formed. Thereafter, the desired cast product is obtained by pouring the molten metal into the space from which the wax has been removed and casting. In this case, since the hollow part is filled with ceramics when pouring the molten metal, the mold strength is high.
This prevents damage to the mold. Furthermore, since the fusible resin disappears during firing and holes are formed, these holes function as gas vent holes, allowing the manufacture of sound castings. Furthermore, since this hole promotes the aging properties of the ceramic, it improves the as-cast properties of the narrow-mouthed hollow part.

[Examples] Examples of the present invention will be specifically described below with reference to the accompanying drawings. FIGS. 1(a) to 1(d) are schematic diagrams showing an example method of the present invention in the order of steps.

As shown in FIG. 1(a), first, a wax mold 11 having a narrow hollow part 12 is formed. Next, as shown in FIG. 1(b), the surface of the wax mold 11 is coated with a first layer and a second layer of refractory material to form a coating layer 13, as in the conventional method.
form. After drying this coating layer 13,
The fusible resin 14 attached vertically to the core bar 15 is placed in the hollow part 12 by passing through the hollow part 12. This fusible resin 1
4 is made of polyvinyl alcohol, for example, and has a string shape. The core bar 15 is a linear member having a diameter of 2 to 3 m+++, and is supported by a soft fusible resin 14 so as to maintain a linear posture. Then, the fusible resin 14 and the core metal 15 are inserted into the narrow hollow part 12 and arranged so as to be coaxial with the wax mold 11 at the center thereof.

Thereafter, as shown in FIG. 1C, a fluid ceramic 16 containing silicic acid sol as a binder and an alkaline curing agent is poured into the hollow part 12, and the hollow part is filled with the ceramic 16. The ceramic 16 is then dried and cured, and then the usual coating is repeated.

Note that since the ceramic 16 is dried by alcohol evaporation, the drying speed is fast.

Next, a dewaxing treatment is performed by heating, and the wax mold 11 surrounded by the coating layer 13 is melted, vaporized, and removed. Then, the coating layer 13 forms a mold front in which the area occupied by the wax mold 11 becomes the injection space.

Thereafter, as shown in FIG. 1(d), this coating layer 13 (
The coating layer 13 is fired by heating the entire body including the mold (before the mold) to, for example, 800 to 850°C. As a result, the coating layer 13 is cured, and the fusible resin 14 is melted and further vaporized and disappears.

Therefore, a thin gas vent hole 17 is formed in the portion occupied by the fusible resin 14. After preheating the mold manufactured in this way, the mold is taken out from the furnace and molten metal is injected into the space surrounded by the coating layer 13 and left to stand, whereupon it solidifies and a casting having a narrow hollow part is manufactured. . In this molten metal injection process, the ceramic 16 is applied to the coating layer 13.
Since it is supported behind the front of the mold, which is made up of
This avoids the occurrence of cracks. Moreover, since the hole 17 is formed in the part where the fusible resin 14 was present, and this hole 17 functions as a gas vent hole, a sound casting without cracks can be obtained.

After the injection of the molten metal and its solidification are completed, the ceramics 16 in front of the mold and on the inner surface are removed. This ceramics 16
The removal may be performed by applying vibration to the entire casting or by applying water pressure to the ceramics 16. In this case, the holes 17, which functioned as gas vent holes, promote the corrosion resistance of the ceramic in this as-cast process. Therefore, in this example, the casting time is short.

Next, the results of producing a magnesium alloy casting by the method of the present invention will be explained in comparison with a comparative example.

Table 1 below shows the casting conditions and results of Examples and Comparative Examples.

In Comparative Example 2 of Table 1, only a mold front made of a coating layer was provided as in the conventional method, but in this case, the mold collapsed and casting was impossible. On the other hand, in Comparative Example 1, since the ceramic was poured into the hollow part 12, molding was possible in the process of forming the narrow hollow part, but oxidation (oxide incorporation) occurred. However, when the fusible resin was disposed as in this example, a sound cast product was manufactured and the as-cast time was short.

[Effects of the Invention] In the present invention, a fusible resin is placed in the narrow hollow part of the wax mold, and this hollow part is further filled with ceramics, so that the mold shell is free from breakage and cracking and has excellent corrosion resistance. It is possible to mold and produce sound castings with no defects.

[Brief explanation of the drawing]

FIGS. 1(a) to 1(d) are schematic diagrams showing the method of the present invention in the order of steps, and the second section is a schematic diagram showing the conventional method. 11: Wax mold, 12: Narrow hollow part, 13; Covering layer, 14
; Fusible resin, 15; Core metal, 16; Ceramics, 17
;hole

Claims (2)

[Claims] (1) A process of applying a mold layer to the surface of a wax mold having a predetermined shape having a narrow hollow part, a process of inserting a fusible resin through the narrow hollow part, and a process of filling the narrow hollow part with ceramics. A narrow-mouthed hollow portion comprising the steps of filling, dewaxing, firing the mold layer and eliminating the fusible resin, and injecting a predetermined molten metal. Precision casting method for castings. (2) The precision casting method for a casting having a narrow hollow portion according to claim 1, wherein the fusible resin is attached to a core wire.