JPS626734A - Casting method - Google Patents

Abstract

PURPOSE:To partially reinforce a casting by preliminarily embedding a reinforcing material having a low m. p. into part of an expendable pattern then executing casting by using such pattern. CONSTITUTION:A foaming agent is impregnated into polystyrene and is heated to foam in a metallic mold. The expendable pattern 10 having a runner 12 and a sprue 13 is manufactured by such method. Plural pieces of tin (Sn) wires 14 are preliminarily embedded at prescribed intervals into the part C of the pattern 10 corresponding to the desired part of the casting. A molten metal adjusted in components to meet the characteristics of the casting in the position corresponding to D of the pattern 10 is then poured into the mold through the sprue 13. The molten metal flowing into the part C melts the wires 14 and is replaced with the pattern 10. The structure having much pearlite is formed in the part C of the product and the structure having much ferrite which does not receive the influence of tin is formed in the part D by the above- mentioned method. The casting is thus partially reinforced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application rt) The present invention relates to a casting method that is applied to produce a cast product with locally enhanced properties.

(Prior art) Conventionally, so-called special casting methods include the lost wax method, which uses wax for the disappearing model, and the full mold method, which also uses foamed resin such as polystyrene or polyethylene for the disappearing model. Other methods include the ceramic shell mode method, centrifugal casting method, vacuum casting method, and mold casting method.

Among these, the casting method that uses a vanishing model has the excellent feature of being able to mass-produce parts with complex shapes with high precision.Among these, the full molding method that uses a vanishing model made of foamed resin is It has excellent features such as being able to be divided into cores, molding cores, and inserting cores, as well as being relatively easy to process the model material and being inexpensive.

FIG. 6 is a diagram illustrating a casting method using such a vanishing model made of foamed resin, in which 101 is the vanishing model made of foamed resin, 102 is foundry sand, 103 is a casting flask, and 104 is the vanishing model 101. The sprue part 105 is the runner part of the vanishing model 101. Then, when molten metal is poured from the sprue 104 during production of a cast product, the molten metal gradually burns and vaporizes the vanishing model 101 due to its heat, progresses into the interior, replaces the vanishing model 101, and becomes the vanishing model 101. Castings of the same shape are produced. In addition, as a prior art of precision casting using such a disappearing model made of foamed resin,
There is a Utility Model No. 47-42481.

(Problems to be Solved by the Invention) As mentioned above, the precision casting method using such a vanishing model has the advantage of being able to improve the precision of the vanishing model and the cast product, and being suitable for mass production. However, for example, when the cast product is a steering knuckle, which is an automobile axle part, as shown in Figure 6, the part (pole joint part) A and the part where wear resistance is required. When there is a part (thrust part) B where elongation is required,
For example, a molten metal whose composition matches the part A where Fa# abrasion resistance is required (for example, 1 molten spheroidal graphite cast iron, Sn, Cu, etc.)
When casting is performed using a molten metal to which pearlite stabilizing elements such as When casting is performed using a molten metal whose composition matches the part B to be obtained (for example, a molten metal in which pearlite stabilizing elements are not added to the spheroidal graphite cast iron molten metal, and the ferrite content increases after !9 hardening), the In the cast product, there was a problem in that the wear resistance of the part A, which is required to have wear resistance, was insufficient.

This invention was made by focusing on these conventional problems, and it is possible to produce a cast product that satisfies these requirements when different characteristics are required for the parts of the cast product. The purpose is to provide a casting method.

[Structure of the Invention] (Means for Solving the Problems) This invention aims to locally strengthen the characteristics of a cast product in a casting method for manufacturing a cast product using a disappearing model that is vaporized by the heat of molten metal. A reinforcing substance with a melting point lower than the melting point of the cast product is embedded in advance in a part of the disappearing model corresponding to the part, and the reinforcing substance is cast using the disappearing model in which the reinforcing substance is embedded, and the part of the disappearing model is partially filled with the reinforcing material. The feature is that the material is dispersed to produce a strengthened cast product.

The material of the cast product to which this invention is applied is not particularly limited,
Metals (including alloys) with appropriate flowability required for casting
is used.

Further, as the disappearing model that vaporizes and disappears due to the heat of the molten metal, a foamed resin such as foamed polystyrene or foamed polyethylene that burns and vaporizes due to the heat of the molten metal is used. This vanishing model can be produced by cutting out the required shape from a block that has been foam-molded to a predetermined size and assembling it into the shape of a cast product, or by foam-molding it using a mold that has the same shape as the cast product. The latter is more suitable for mass production. When producing the vanishing model, a reinforcing substance having a melting point lower than that of the casting is embedded in a portion of the vanishing model that corresponds to the part where the properties of the casting are desired to be strengthened. In this case, the reinforcing substance used is powder, linear, net, flake, etc., and after casting, the reinforcing substance is dispersed in specific parts of the cast product. shall be strengthened. Note that it is also desirable to apply a coating material to the surface of the disappearing model to prevent seizure, if necessary.

(Example) In this example, a case where the cast product is a steering knuckle which is an axle part of an automobile will be described.

First, by impregnating polystyrene with a foaming agent and heating and foaming it in a mold, a product part 11 having a shape corresponding to the shape of the steering knuckle as shown in FIG. 2, and a runner part 12, A vanishing model 10 having a sprue part 13 was manufactured. In this case, in order to strengthen the wear resistance of the pole joint part of the steering knuckle (corresponding to part C in Fig. 2), a tin (S n) wire 14 is attached to a predetermined part of the vanishing model 10 corresponding to this part. In this example, a total of nine trees were buried, three horizontally and three vertically, at 5mm intervals.

Next, this disappearing model 10 is placed in the PI frame 2 as shown in FIG.
It was buried in foundry sand 22 in 1.

Next, molten spheroidal graphite cast iron having the composition shown in Table 1, whose composition was adjusted so as to obtain the required elongation in the thrust part of the steering knuckle (position corresponding to D in Figs. 1 and 2), was poured from the sprue 13. I poured it.

Table 1 By pouring this molten metal, the disappearing model 10 is
The molten metal gradually burns and vaporizes and disappears from the part 3, replacing it with metal, and the molten metal flows into the product part 11 through the runner part 12. In this case, the vaporized polystyrene penetrates into the interstices of the foundry sand 22, is cooled by the foundry sand 22, and binds the sand grains.

The molten metal then flows to the part corresponding to the thrust part of the steering knuckle (part D in Figure 1), and
Part corresponding to the pole joint part (part C in Figure 1)
The molten metal flowing into the C portion corresponding to the pole joint replaces the disappearing model 10 while melting the tin wire 14.

At the time when the disappearance model 10 has completely disappeared, the C part corresponding to the pole joint part has become a molten metal with a high Sn concentration, and after the reception, pearlite is formed as shown in the macrostructure in Fig. 3. The structure has a large amount of ferrite (the part that looks white in the figure), and the part that is not affected by Sn has a structure that has a lot of ferrite (the part that looks black in the figure), as shown in FIG. Figure 4 shows a part with a structure containing a lot of pearlite (part E in Figure 3 (b))
Figure 5 shows the micrometallic structure of the part with a lot of ferrite (section F in Figure 3(b)), where the black round part is graphite and the white part is ferrite. , the black part is perlite.

Therefore, the pole joint part of the steering knuckle has a lot of pearlite structure and has excellent wear resistance, and the thrust part has a lot of ferrite structure and has excellent elongation and toughness because it is not affected by the Sn. ing.

[Effects of the Invention] As explained above, according to the present invention, in a casting method for manufacturing a cast product using a disappearing model that is vaporized by the heat of molten metal, it is possible to locally strengthen the characteristics of a cast product. A reinforcing substance with a melting point lower than that of the cast product is embedded in advance in the part of the disappearing model corresponding to By dispersing and strengthening the cast product, it is possible to make different parts of the cast product have different properties. For example, a certain part of the cast product has high hardness and has excellent abrasion resistance, and A very excellent effect is brought about in that it is possible to produce a cast product that has contradictory properties such as low hardness and excellent elongation or toughness in a certain part.

[Brief explanation of drawings]

Figures 1 and 2 are a sectional view of the mold used in the casting method of the present invention, a front view of the disappearing model, and Figure 3 (a).
)(b) is a micrograph and a copy showing the macrometal structure of the cast product, FIG. 4 is a micrograph showing the micro metal wire #a (metal structure with a lot of pearlite) in the reinforced part of the cast product, and FIG. The figure is a micrograph showing the micrometallic structure (metallic structure with a lot of ferrite) of the unreinforced part of the cast product.
FIG. 6 is a sectional view of a mold formed by a conventional casting method using a vanishing model. 10... Disappearance model, 14... Tin vQ (reinforcing substance). Representative Patent Attorney Yutaka Oshio Figure 21

Claims (2)

[Claims] (1) In a casting method in which a cast product is manufactured using a vanishing model that vaporizes due to the heat of molten metal, the parts of the vanishing model that correspond to the areas where you want to locally strengthen the properties of the cast product are placed in advance from the melting point of the cast product. A reinforcing substance with a low melting point is embedded in the casting product, and a cast product in which the reinforcing substance is partially dispersed is produced by casting using a disappearing model in which the reinforcing substance is embedded. Casting method. (2) The cast product is made of spheroidal graphite cast iron, the reinforcing substance is a pearlite stabilizing element such as Sn or Cu, and the reinforced part has a structure with a large amount of pearlite. A casting method according to claim (1).