JPS6076249A - Sand core - Google Patents

Abstract

PURPOSE:To provide a sand core which assures substantial ventability and improves strength by reinforcing the inside of the core molded to a prescribed shape by using green sand with a mandrel of a hollow shape provided with a suitable number of fine holes. CONSTITUTION:This core 1 is molded of green sand 2 and the inside thereof is reinforced by a mandrel 3. The core is approximately cylindrical and the mandrel 3 is made into the cylindrical shape having a pointed tip. Many fine holes 4 for venting are punched to the mandrel 3. The molding of the core 1 is accomplished by inserting the mandrel 3 onto a bar member 9, opening a shutter between a core box 6 and a green sand feed port 7 and feeding the green sand 2 into the box 6. The shutter is then closed and a lower shutter is opened to advance the member 9 into the box 6 to compress the green sand 2 by about 30% thereby molding the core 1. The member 9 is drawn while the mandrel 3 is left in the box 6 and thereafter the core 1 is removed from the box 6.

Description

[Detailed description of the invention] [Field of technology] The present invention relates to a sand core used in casting.

[Prior art]

Various types of cores are used when manufacturing castings with long, narrow holes or hollow parts. In addition to sand cores, there are other types of cores such as metal cores, wax cores, etc., but sand cores are often used in consideration of mass productivity, disintegrability, cost, etc. Among sand cores, hollow sand cores are sometimes used because they have good disintegration properties after pouring and also have good degassing properties.

Such a hollow sand core has conventionally been disclosed in, for example, Japanese Patent Application Laid-Open No. 57-1
Publication No. 95555 (Japanese Patent Application No. 1983-SA).

As shown in 80), a rod member of a predetermined thickness is inserted into the cavity of a core box filled with green sand, the green sand is compressed and hardened, and then the rod member is pulled out to be shaped.

By the way, although this sand core (hereinafter simply referred to as core) has the advantages of good collapsibility, good degassing properties, and low cost, due to the low strength inherent in green sand, it cannot be used for thin, long, or even long items. If the core has a complex shape that tends to cause stress concentration, the core may be damaged or broken during handling or when storing the core, which is extremely inconvenient in handling.

Also, when handling the core, the surface of the core may be damaged by holding it or placing it on a stand.
After casting, defects such as poor casting surface and scratches may occur in the product.

[Purpose of the invention]

The present invention has been made to solve the problems of the prior art described above, and an object of the present invention is to provide a core that has improved strength while ensuring sufficient degassing performance.

[Structure of the invention]

According to the present invention, this object is achieved by a core formed into a predetermined shape using green sand and reinforced with a core having a hollow body shape provided with an appropriate number of pores. be done.

In the present invention, the core metal is a heat-resistant part made of metal, ceramic, etc.
A, and has a hollow body shape such as a cylindrical shape. This metal core is also used as a green sand compressor during core molding, so it is desirable that it has a shape that allows it to easily enter the green sand, and it is desirable that the tip has a pointed shape. . Also,
The pores are provided to ensure gas release properties, and are provided in an appropriate number on the core bar. The shape of this pore may be circular or slit-like. Further, the core bar itself can also be formed of a mesh.

The core according to the present invention is made by inserting a rod member of a predetermined thickness with a metal core on the surface into the cavity of a core box filled with green sand, and compressing and hardening the green sand by 20 to 50%. , and then the rod member is pulled out while leaving the core metal inside the core.

[Action/effect of the invention]

Since the core of the present invention is internally reinforced with a metal core, its strength is improved and there is no chance of it breaking or breaking.

In addition, since the core bar is hollow and has an appropriate number of pores, the degassing properties of the core are not inhibited in any way, and sufficient degassing properties can be ensured.

In addition, since the strength is improved, it can be used with a long and narrow core or a core with multiple shapes, thereby expanding the range of applications.

Furthermore, the strength is improved and it is not easily damaged, making it easier to handle.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

[First Embodiment] FIG. 1 is a sectional view showing a core according to a first embodiment of the present invention, and FIG. 2 is a schematic configuration diagram showing a manufacturing apparatus for molding the core of the present invention.

In Figure 1, 1 is a core, and this core 1 is green sand 2
The inside is reinforced with a core metal 3. This core 1 has an approximately cylindrical shape, and the core metal 3
It has a cylindrical shape with a pointed tip. Further, the core bar 3 is provided with a large number of pores 4 for venting gas.

This core 1 is molded by an apparatus shown in FIG. Second
In the figure, 5 is a frame, a core box 6 is fixed on top of this frame 5, and a green sand charging lower is provided on top of the core box 6. The boundary between this green sand input lower and the core box 6 can be opened and closed by a shutter (not shown). Further, a cylinder 8 is provided below the core box 6, and a rod member 9 connected to a piston (not shown) in the cylinder 8 is directed toward the inside of the core box 6. It is said that it can move forward and retreat freely. Incidentally, the lower part of the core box 6 can also be opened and closed by the illustrated hinge.

A core 1 shown in FIG. 1 was molded using this manufacturing apparatus. First, the core metal 3 is inserted into the outer surface of the rod member 9, and the shutter between the core box 6 and the green sand charging lower is opened, and the green sand 2 is charged into the core box 6.

Subsequently, this shutter is closed, the lower shutter is opened, and the rod member 9 is advanced into the core box G. As a result, the green sand 2 is compressed by about 30% to form the core 1. Subsequently, the rod member 9 is pulled out with the core metal 3 remaining in the core box 6.

Thereafter, the core 1 is taken out from the core box 6.

As a result of the above, the diameter is 36.8 mm and the length is 15 (1+m).

A plurality of cores with a wall thickness of 8.41 mm were molded.

Using this core, the bending strength and breakage rate when using the core were measured using a J-circumferential test.

The bending strength was measured by supporting the core at both ends and applying a load to the center, as shown in FIG. As a result, while the conventional core without a metal core broke under a load of 200 to 600 g, the core body of the core of the present invention broke under a load of about 10 kg. This shows that the core of the present invention has strength approximately 15 times or more than that of the conventional core.

In addition, while conventional cores were damaged by approximately 5% during transportation and approximately 15% when packed, the core of the present invention has a breakage rate of 0.
%.

In addition, since the core metal is hollow and provided with a large number of pores, the degassing performance was not inferior to that of a conventional core that does not use a core metal.

[Second Embodiment] FIG. 3 is a sectional view showing a core according to a second embodiment of the present invention.

The difference between the second embodiment and the first embodiment is that the shape of the core bar 3 in the second embodiment is a simple cylinder, and that a part of the core bar 3 protrudes outside. The rest is substantially the same as the first embodiment.

In the second embodiment, all the effects of the core of the first embodiment can be achieved, and a part of the core metal protruding to the outside can be used as a handle, so there is no need to directly touch the raw sand. Therefore, defects on the surface of the core such as chipping and falling of the green sand are significantly reduced. Moreover, by using a part of the core metal as a handle, handling of the core becomes easier2.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a sand core according to a first embodiment of the present invention, FIG. 2 is a schematic configuration diagram showing a manufacturing apparatus for molding a sand core of the present invention, and FIG. 3 is a cross-sectional view showing a sand core according to a first embodiment of the present invention. FIG. 4 is a cross-sectional view showing the sand core according to Example 2. FIG. 4 is an explanatory view showing an outline of the bending test. 1 --- One sand core 2 --- Green sand 3 --- One core metal 4 ---- Pore 5 --- One frame 6 --- One core box 7 ----- Life sand inlet 8 -- - Cylinder 9 ----- One rod member

Claims (1)

[Claims] (1) A core molded into a predetermined shape using raw sand,
A sand core characterized in that the inside thereof is reinforced by a core metal, the core metal is hollow, and is provided with an appropriate number of pores.