JP2003260555A - Molten metal injection molding sleeve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a three-layered molten metal injection molding sleeve having an excellent heat retaining property wherein an external cylinder and an intermediate member, and the intermediate member and an internal cylinder are correctly bound and the entire sleeve is not loosened even if the external cylinder reaches a relatively high temperature when the sleeve is used for practical injection-molding of the molten metal. <P>SOLUTION: The sleeve so constituted that the internal cylinder comprising silicon nitride ceramics, the external cylinder comprising a heat resistant metal and the intermediate member comprising a thermal insulating material between the internal cylinder and the external cylinder are provided is characterized in that the expansion coefficient of the intermediate member at a room temperature is bigger than those of the internal cylinder and the external cylinder. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a melt injection molding sleeve which is required to have heat retention, wear resistance, corrosion resistance, thermal shock resistance and mechanical strength in melt injection molding.

[0002]

2. Description of the Related Art As a conventional melt injection molding sleeve,
For example, Japanese Patent Laid-Open No. 53-70034 discloses a two-layer molten metal injection molding in which an outer cylinder made of a heat-resistant metal is provided on the outer circumference of an inner cylinder made of silicon nitride ceramics having excellent wear resistance, corrosion resistance and thermal shock resistance. A sleeve for use is disclosed.

Further, Japanese Patent Laid-Open No. 6-79426 discloses that
A melt injection molding sleeve having a three-layer structure is disclosed, in which an intermediate cylinder made of zirconia ceramics is provided between an inner cylinder made of sialon or dense silicon nitride ceramics and an outer cylinder made of heat-resistant metal.

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention JP-A-53-70
In the double-layered sleeve of Japanese Patent No. 034, since the thermal conductivity of silicon nitride ceramics is relatively high, the heat insulating effect, that is, the heat retaining property is insufficient. Therefore, the temperature of the molten metal decreases during casting, and the temperature between the molten metal and the inner cylinder increases. A chill layer, which is a solidified layer of the molten metal, is formed, and the chill layer is mixed in the molten metal during repeated injection. Therefore, there is a problem that it not only causes defects in the product but also affects the flow of molten metal. Also, when manufacturing large castings,
It is necessary to raise the temperature of the molten metal in order to improve the flow of the molten metal. However, raising the temperature of the molten metal causes problems such as shortening the mold life, prolonging the solidification time, and difficulty in workability.

In the three-layer structure sleeve disclosed in Japanese Patent Laid-Open No. 6-79426, the inner cylinder has a coefficient of thermal expansion of 3.0 at room temperature.
˜3.4 × 10 ⁻⁶ / ° C., dense silicon nitride, the intermediate cylinder has a thermal expansion coefficient at room temperature of 7.0 to 10.5 × 10 ⁻⁶ / ° C.
Zirconia ceramics, SKD6 having an outer cylinder having a thermal expansion coefficient of 11.0 to 12.0 × 10 ⁻⁶ / ° C. at room temperature.
1 is used. Therefore, when melt injection molding is actually performed, when the temperature of the outer cylinder becomes high, the tightening force applied to the intermediate cylinder and the inner cylinder by the outer cylinder becomes small due to the difference in thermal expansion. There is a problem that the cylinder and the inner cylinder are not sufficiently restrained and loosening may occur in the entire sleeve.

The present invention has been made in view of the above-mentioned problems of the prior art, and is excellent in heat retaining property and the temperature of the outer cylinder becomes relatively high when the molten metal is actually injection-molded. Another object of the present invention is to provide a melt injection molding sleeve having a three-layer structure in which the outer cylinder and the intermediate member are accurately restrained, and the intermediate member and the inner cylinder are accurately restrained, and the entire sleeve is not loosened.

[0007]

The molten metal injection molding sleeve of the present invention comprises an inner cylinder made of sialon or silicon nitride ceramics, an outer cylinder made of heat-resistant metal, and heat insulation between the inner cylinder and the outer cylinder. And an intermediate member made of a flexible material, and the coefficient of thermal expansion of the intermediate member at room temperature is larger than that of the inner cylinder and the outer cylinder. In the present invention, the coefficient of thermal expansion of each member at room temperature is as follows: inner cylinder: 4.0 × 10
^-6 / ° C. or less, the outer tube: 6.0 × ^{10 -6} / ℃ below, the intermediate member: characterized in that it is 9.0 × ^{10 -6} / ℃ above. Further, the intermediate member is made of heat insulating ceramics.

[0008]

The inner cylinder of the present invention is preferably sialon, silicon nitride, or sialon ceramics containing sialon containing other additives, or silicon nitride ceramics containing silicon nitride containing other additives. In order to provide strength against heat and pressure received from the high temperature molten metal, it is preferable that the flexural strength is 800 MPa or more at room temperature, 700 MPa or more at 1000 ° C., and the thermal expansion coefficient is 4.0 × 10 ⁻⁶ / ° C. or less at room temperature.

The material of the outer cylinder of the present invention will be described. Book
The molten metal injection molding sleeve of the invention receives heat from the mold, etc.
Therefore, it must have excellent heat resistance and high strength.
Yes. In addition, SKD6 has a relatively large coefficient of thermal expansion at room temperature.
1 (11.0 to 12.0 x 10 ^-6/ ° C) etc. as the outer cylinder material
If it is used, the temperature of the outer cylinder is
Therefore, a gap is created between the intermediate member and the inner cylinder, and between the outer cylinder and the intermediate member.
And the sleeve becomes loose. Therefore, outside
The thermal expansion coefficient of the cylindrical material at room temperature is 6.0 x 10^-6/ ° C or less
The lower refractory metal is suitable. Even more preferably
4.0 x 10^-6/ ° C or lower.

As the intermediate member of the present invention, one having an excellent heat insulating property is used to the extent that the formation of a solidified layer in the inner cylinder during injection molding is eliminated. 5.0W thermal conductivity at room temperature
/ M · K or less and a thermal expansion coefficient of 9.0 × 10 ⁻⁶ / ° C. or more are suitable, and zirconia-based ceramics are particularly preferable. The intermediate member may be in the form of a tubular body, a tubular body divided into a plurality in the axial direction or the circumferential direction, a lump, or a powder.

The molten metal injection molding sleeve of the present invention satisfying the above conditions is excellent in heat retention and can prevent the fracture chill from being mixed into the product during casting, and enhance the quality stability of the product, and Even in the case of producing a large-sized cast product, since the heat retaining property is sufficient, stable production can be performed without raising the temperature of the molten metal.

In the molten metal injection molding sleeve of the present invention, the intermediate member made of a heat insulating material has a coefficient of thermal expansion larger than that of the inner cylinder and the outer cylinder. Therefore, even if the temperature of the outer cylinder becomes high during injection molding of the molten metal, the outer cylinder exerts a tightening force on the intermediate member and the inner cylinder, and the sleeve does not loosen. Highly stable manufacturing is possible in molding.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The melt injection molding sleeve of the present invention will be described with reference to the drawings. FIG. 1 is a schematic sectional view of a melt injection molding sleeve of the present invention. In FIG. 1, 1 is an inner cylinder made of silicon nitride ceramics, 2 is an intermediate member made of zirconia ceramics, and 3 is an outer cylinder made of heat-resistant metal. The intermediate member 2 and the outer cylinder 3 are joined by a clearance fit, and the inner cylinder 1 and the intermediate member 2 are joined by a shrink fit. The dimensions of the main part of each member are as follows: inner cylinder: inner diameter 90.001 mm, outer diameter 110.20.
3 mm, intermediate member: inner diameter 109.751 mm, outer diameter 12
3.741 mm, outer cylinder: inner diameter 123.983 mm, outer diameter 180.001 mm. Table 1 shows the thermal expansion coefficient (× 10 ⁻⁶ / ° C.) and thermal conductivity (W / m · K) of each member at room temperature.
Indicates. 4 is a plunger tip and 5 is a hot water supply port.
After the molten metal is poured into the hot water supply port 5, the inner surface of the inner cylinder 1 comes into contact with the high temperature molten metal, and the plunger tip 4 slides during injection.

[0014]

Next, an actual machine test was conducted to confirm the heat retaining property of the molten metal injection molding sleeve of the present invention. A 700 ° C. molten aluminum was poured into the molten metal injection molding sleeve of the present invention (Example) and injection was performed. Then, after pouring and after injection, the surface temperature of each inner cylinder was measured. The position where the temperature was measured is point A in FIG.

Table 2 shows the temperature measurement results. As Comparative Example 1, a two-layer structure sleeve composed of an inner cylinder made of sialon and an outer cylinder made of a heat-resistant metal which is a low thermal expansion material, and as Comparative Example 2,
The results of a single-structured sleeve whose entire sleeve is made of hot die steel SKD61 are also shown. In this test, the surface temperature of the inner cylinder was measured after 1 cycle, 10 cycles and 30 cycles, with pouring and injection (injection time 60 seconds) as 1 cycle.

[0017] Table 2             1 cycle      10 cycles      30 cycles           After pouring After injection After pouring After injection After pouring After injection           (℃) (℃) (℃) (℃) (℃) (℃) Example 614 287 639 403 645 431 Comparative Example 1 613 241 633 358 638 398 Comparative Example 2 553 180 575 287 592 341

From Table 2, in the sleeve of this embodiment, the temperature of the inner surface of the sleeve after pouring and injecting after 1 cycle, 10 cycles, and 30 cycles was the same as Comparative Example 1,
It is higher than that of Comparative Example 2, and it can be seen that the heat retaining property is very excellent.

Next, FIG. 2 shows the results of measuring the amount of looseness of the melt injection molding sleeve at high temperature when the outer cylinder is made of a heat-resistant metal of a low thermal expansion material and when the outer cylinder is made of SKD61. Show. Here, the looseness amount is an amount indicating a value obtained by adding the respective gaps generated between the intermediate member and the inner cylinder and between the outer cylinder and the intermediate member due to the difference in thermal expansion. That is, when the looseness amount shows a negative value, the outer cylinder and the intermediate member and the intermediate member and the inner cylinder are sufficiently restrained by the clearance fit and the shrink fit, but when the looseness amount shows the positive value. It shows that the entire sleeve is not sufficiently restrained.

It can be seen from FIG. 2 that the melt injection molding sleeve using the SKD61 as the outer cylinder becomes loose at 200 ° C. or higher. However, in the sleeve for melt injection molding using the outer cylinder, which is a heat-resistant metal of a low thermal expansion material having a thermal expansion coefficient smaller than that of the intermediate member of the present invention, looseness does not occur up to around 500 ° C, and the sleeve does not rise up to around 500 ° C. It can be seen that the whole is sufficiently restrained. Therefore, it is understood that stable molten metal injection molding at high temperature is possible.

[0021]

INDUSTRIAL APPLICABILITY The present invention is a material for a melt injection molding sleeve having a three-layer structure of an inner cylinder, an intermediate member, and an outer cylinder, which is excellent in heat retention, heat insulation, and mechanical strength, and is actually melt injection molded. Even if the outer cylinder becomes hot when performing, the entire sleeve does not loosen.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a molten metal injection molding sleeve of the present invention.

FIG. 2 shows the results of measuring the amount of looseness of the melt injection molding sleeve at high temperature.

[Explanation of reference numerals] 1 inner cylinder, 2 intermediate member, 3 outer cylinder, 4 plunger tip, 5 hot water inlet

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shingo Nogami             1-9-1 Kitahama, Wakamatsu-ku, Kitakyushu City, Fukuoka Prefecture               Hitachi Metals Co., Ltd. Wakamatsu Factory

Claims (3)

[Claims] 1. An intermediate member comprising an inner cylinder made of sialon or silicon nitride ceramics, an outer cylinder made of heat-resistant metal, and an intermediate member made of a heat insulating material between the inner cylinder and the outer cylinder. A molten metal injection molding sleeve having a coefficient of thermal expansion at room temperature higher than that of the inner cylinder and the outer cylinder. 2. The coefficient of thermal expansion of each of the members at room temperature is 4.0 × 10 ⁻⁶ / ° C. or less for the inner cylinder and 6.0 × 10 for the outer cylinder.
The molten metal injection molding sleeve according to claim 1, wherein the temperature is ^-6 / ° C or less and the intermediate member is 9.0 x 10 ^-6 / ° C or more. 3. The melt injection molding sleeve according to claim 1, wherein the intermediate member is made of heat insulating ceramics.