JPS5935853A - Casting method of thin walled casting - Google Patents

Abstract

PURPOSE:To make the draft on a bore surface zero and to obtain a casting product having high dimensional accuracy by disposing a metal mold for core covered thereon with molding sand in a metal mold for a master mold, casting molten metal into the space between both and producing the thin walled casting. CONSTITUTION:A recess 7a for casting a thin walled cylindrical casting W is formed of a metal mold 2 and the other metal mold. A round corner part 9 of a casting provided with flanges 8a, 8b at the ends such as a cylinder liner is vulnerable to be chilled and therefore a heat insulating material body 10 is embedded in a recess 11. A rod 6 of an air cylinder is extended to insert a metal mold 4 for core coated at the periphery thereof with a prescribed amt. of molding sand 14 into the recess 7a of the mold 2. Molten metal is cast into the space 15 between the mold 4 and the sand 14 and the object W is formed. Since the draft is zero, the mold 4 is easily removable after solidification and the higher dimensional accuracy is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for casting thin-walled castings, and more specifically, to a casting method in which thin-walled cylindrical castings are manufactured using a mold for manufacturing cast iron, the drafting slope of the inner diameter surface is set to zero. It is about the method.

Conventionally, when casting thin-walled cylindrical castings such as engine parts such as exhausts, brake bodies, and cylinder liners, sand molds have generally been used in consideration of the generation of chill that makes cutting difficult.

By the way, in some cases, when manufacturing cylinder liners,
Mold casting is carried out, but the coating material for the mold is 3 to 5 times.
The core surface is sand molded, and dimensional accuracy is an important issue with thin-walled castings, so to avoid the problem of chilling, it is necessary to cast thick-walled products and then machine cut them to make them thinner. There was a need.

For this reason, conventionally, when thin-walled cylindrical castings were cast using sand molds, it was always necessary to cast them in a thick-walled state and then perform mechanical cutting to ensure dimensional accuracy. There was a problem in that a large amount of cast iron was required, which increased costs.

This invention focuses on the problems caused by traditional sand mold casting, and manufactures thin-walled castings by metal mold casting.In order to reduce the amount of sand used during manufacturing, the mold core is coated with sand. The present invention provides a method for casting thin-walled castings that significantly reduces the amount of cast iron used, improves the dimensional accuracy and quality accuracy of the thin-walled castings, and reduces costs.

In order to achieve the above object, the present invention includes a core mold whose surface is coated with cast iron inside a main mold mold, and a core mold whose surface is coated with cast iron. The gist of this method is to pour molten metal between the mold and the main mold, solidify it, and then take out the core mold from the main mold to produce a thin-walled casting.

Hereinafter, the present invention will be described in detail based on the accompanying drawings.

FIG. 1 shows a thin cylindrical casting W (cylinder liner) formed by the casting method of the present invention, and this thin cylindrical casting W is cast by a mold body 1 as described below.

The mold body 1 is composed of a mold 2 and a mold (not shown) having a symmetrical shape with the mold 2, and when casting a thin-walled cylindrical casting W as described above, as shown in FIG. A hollow cylindrical core mold 4 as shown in FIG. 1 is used.

Note that 5 is a fixed flange that connects the mold 2 and a mold (not shown), 6 is a rod of an air cylinder (not shown) that takes the core metal/q'X mold into and out of the mold body 1;
Reference numeral 20 indicates a casting hole, and 21 indicates a gas vent hole.

With such a mold body 1, thin-walled cylindrical castings W
When casting (cylinder liner W), four parts 7a for casting the thin cylindrical casting W are formed in the mold 2 and a mold (not shown).

For thin-walled cylindrical castings W1, particularly for cast products having 7-rank parts 8a and 8b at the end portions, such as cylinder liners W, the 7-rank parts 8a.

At the corner radius portion 9 (chill generation position 9) where 8b is thin and comes into direct contact with the mold, it is rapidly cooled and so-called chill occurs. For this reason, in advance, the heat insulating material body 1 as shown in FIG.
0 is the place where the above chill is likely to occur, that is, the 7th rank part 8
It is buried in the four parts 11 that form a and sb, and arrangements are made to prevent the cast metal from cooling rapidly.

Further, as shown in FIG. 3, the heat insulating material body 10 is formed in a sandwich shape by a metal plate 12 (steel plate) and a heat insulating material 16 such as Kao wool or asbestos, and has fixing means such as bolts (not shown). It is fixed by The corner rounded portion 9 is configured so that the thermal conductivity can be freely changed and can also be used as a reinforcing member.

On the other hand, the peripheral surface of the core mold 4 is coated with a predetermined amount of cast iron 14, as shown in FIGS. 2 and 4. From this state, the two molds 2 and the mold (not shown) are fixed by the fixing flange 5 and fixing means such as bolts (not shown), and the rod 6 of the air cylinder (not shown) is extended into the four parts 7a of the mold 2. The core mold 4 covered with the cast iron 14 is inserted by actuation. The two molds 2, the recess 7a of the mold (not shown), and the cast iron 14 coated on the core mold 4.
Molten metal is poured into the space 15 between the two to form a thin-walled cylindrical casting W as shown in FIG.

The cast molten metal is gradually cooled by the heat insulating material main body 10 in the mold 2 and the corner radius portion 9 (not shown) of the mold, so there is almost no chilling in the 7 rank parts 8a and ab. Further, in the cylindrical portion 16 (4), since only a small amount of cast iron 14 is used, there is almost no need for mechanical cutting after forming.

In addition, when removing the core mold 4 after the molten metal has solidified, since the drafting slope is zero, it can be easily removed.
After removing the core mold 4, the amount of cast iron 14 taken out from the inner surface of the thin-walled cylindrical casting W is small, and the dimensional accuracy and quality of the cast product can be further improved.

In this invention, as described above, a core mold whose surface is coated with cast iron is disposed inside the main mold, and the cast iron coated on the surface of the core mold and the mold are connected. After the molten metal is poured in between and solidified, the core mold is removed from the mold to form a thin-walled casting, which significantly reduces the amount of cast iron used and improves the dimensional accuracy and quality accuracy of the thin-walled casting. This has the effect of improving performance and reducing costs.

[Brief Description of the Drawings] Fig. 1 is a perspective view of a thin-walled cylindrical casting cast by the casting method of the present invention, Fig. 2 is a cross-sectional explanatory view showing the casting process,
FIG. 3 is a perspective view of the heat insulating material body, and FIG. 4 is a sectional view showing the state of use of the heat insulating material body. 2... Mold 1 Mold not shown, 4... Mold for core,
14...Cast iron, W...Thin-walled casting (thin-walled cylindrical casting). Agent: Patent Attorney Makoto Ogawa − Patent Attorney: Ken Kenguchi Patent Attorney: Kazuhiko Saishita (7)

Claims (1)

[Claims] A core mold whose surface is coated with cast iron is placed inside the main mold, and molten metal is placed between the cast iron coated on the surface of the core mold and the main mold. 1. A method for casting a thin-walled casting, characterized in that after casting and solidifying, the core mold is removed from the main mold to produce a thin-walled casting.