JPH02241644A - Core for manufacturing hollow casting - Google Patents

Abstract

PURPOSE:To prevent gas defect caused by decomposed gas of resin by mixing metal powder, which is melted at higher temp. than softening temp. and lower temp. than the decomposed-gasifying temp. of the resin and generates endothermic reaction, with the thermosetting resin powder at the specific vol. ratio and compacting. CONSTITUTION:To the thermosetting resin powder, the metal powder of metal or alloy, a part of the whole of which is melted at higher temp. than the softening temp. of this resin and lower temp. than the decomposed-gasifying temp. of this resin to generate the endothermic reaction, is mixed in the range of 5-60vol.% and compacted. This core 1 is inserted into one pair of porous fibrous forming bodies 2 and set as pressing in the die 3, and by pouring molten metal 5, the high pressure casting is executed while quickly applying the pressure with a pressurizing plunger 4. A hole 8 penetrated to the internal chilling part of the core 1 from outside of a casting product (hollow casting) 7 manufactured in such a way, is opened and the heat treatment is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a core used when manufacturing a cast product having an internal cavity by a pressure casting method, and particularly to a core made of heat-resistant resin.

[Conventional technology]

Conventionally, when manufacturing products with internal cavities, such as pistons with internal cooling channels for cooling oil, by pressure casting, the cores used were salt cores or Na (sodium) cores. SO low melting point metal
Core enclosed in S pipe (stainless steel pipe), etc.
Alternatively, a core made of heat-resistant resin was used.

Among the cores mentioned above, the pressure casting method using a salt core is as follows:
For example, there is a method for manufacturing a piston for an internal combustion engine disclosed in JP-A-60-119348, and documents disclosing a pressure casting method using a core made of heat-resistant resin include, for example, JP-A-52-1989. There is a method for manufacturing hollow castings disclosed in Japanese Patent No. 16865.

[Problem to be solved by the invention]

Here, among the conventional cores, the salt core has low toughness, so it is difficult to avoid mechanical stress when setting it in the mold, or
Due to the thermal stress generated during casting, cracks are likely to occur, and as a result, molten metal may be inserted into the product, making it impossible to form the desired cavity inside the product.

On the other hand, cores made of SUS vibrator filled with Na or cores made of heat-resistant resin have high toughness and are easy to handle, so defects caused by insertion of molten metal like the salt cores mentioned above do not occur. do not.

However, in the former core, SU surrounding Na
Since the S-pipe remains encased in the casting, if a cooling cavity is required, there is a problem that the cooling efficiency is poor due to the low thermal conductivity of the SUS pipe.

Although the latter core made of heat-resistant resin does not have the same problems as the salt core or the core in which Na is sealed in a SUS vibe, there is another problem. That is, since thermal decomposition gas of the resin material is generated on the surface of the core during casting, there is a problem that gas defects occur in the casting.

Therefore, the present invention is intended to prevent the drawbacks of the heat-resistant resin core, and suppresses the generation of thermal decomposition gas from the resin material by suppressing the temperature rise of the core during pouring. The purpose is to

[Means to solve the problem]

Therefore, the present invention provides a core for hollow casting mainly composed of a thermosetting resin, in which the thermosetting resin powder is heated at a temperature higher than the softening temperature of the resin and A metal powder of a metal or alloy that partially or completely melts and causes an endothermic reaction at a temperature lower than the decomposition vaporization temperature.
It is characterized by being mixed in a volume ratio of 5 to 60% and formed by compression molding.

[Effect]

According to the present invention, the metal powder inside the core melts before the thermosetting resin decomposes during casting, and at that time, the heat of fusion taken from the surroundings prevents the temperature of the core from increasing. Maintained below the decomposition temperature of the curable resin. As a result, no gas is generated from the thermosetting resin during casting.

〔Example〕

Next, the present invention will be explained using the following examples and comparative examples.

First, a core sample according to an embodiment of the present invention will be explained based on FIGS. 1 to 3.

FIG. 1 is a schematic sectional view of a core set showing a state in which the core is wrapped in a fiber molded body to be cast into molten metal.

The core 1 of the sample is made of epoxy resin powder (ρ-1,2) with an average particle size of 0.5 mm and Sn with an average particle size of 0.1 ml.
Powder Cp=1.3) was mixed at a weight ratio of 1:2.61 and a volume ratio of 7:3 to give a total amount of 29.7g, and after stirring thoroughly, this was placed in a mold at 150°C. It was compression-molded in a vacuum chamber to form a disk shape with a diameter of 50 mm and a length of 5 mm.

This disk-shaped core 1 has Sn powder dispersed in an epoxy resin at a volume ratio of 30%.

As shown in FIG.
It was sandwiched between a pair of porous fiber molded bodies 2 having one recess. This porous fiber molded body 2 is made of AI.

0s-52%5ift ("
Arsilon") with a volume percentage of 7% was used.

This porous fiber molded body 2 is intended to be cast into a cast product to strengthen the metal and make it into a fiber-reinforced metal.

Next, as shown in FIG. 2, which is a schematic cross-sectional view of high-pressure casting, the porous fiber molded body 2 with the core 1 sandwiched therein is press-fitted into a mold 3 at room temperature, and the temperature of the molten metal is JI at 740℃
S AC8A (Aj2-12%5i-1%Cu-1%
A molten metal 5 of Mg) was poured and high-pressure casting was performed while immediately applying a pressure of 1000 kg/- with a pressurizing plunger 4. After casting, the cast product is pushed out from the mold 3 using a knockout bin 6 and taken out.

As shown in the cross-sectional view of the cast product in FIG. 3, a hole 8 with a diameter of 10 mm is made from the outside of the cast product 7 manufactured in this way to the ingot part of the core 1, and then heat treatment is performed. Ta. The heat treatment is the usual AC8AC10 stabilization treatment, so-called Tn treatment, which includes solution treatment at 490°C for 3 hours, followed by water quenching, aging at 220°C for 6 hours, and then air cooling. do.

When the cast product 7 after the heat treatment was examined, it was found that the core 1 was hollow, and no defects such as cavities due to the generation of decomposed gas from the epoxy resin were found in the cast product 7.

Incidentally, the cavity formation is performed by decomposing and vaporizing the epoxy resin during solution treatment. At this time, the Sn powder is oxidized to become SnO□, which remains in the cavity as a solid powder, and is washed away with running water during water quenching.

In Example 1, Sn powder is mixed into the epoxy resin powder that forms the core 1, and the melting point of this Sn powder is 232°C, which is the decomposition point of the epoxy resin that is the main material of the core 1. Since the temperature is lower than 250°C, when the temperature of core 1 is increased, the temperature of core 1 is increased before the epoxy resin decomposes.
The Sn powder inside is melted. At this time, the Sn powder absorbs a large amount of heat of fusion from the surroundings, which prevents the temperature of the core 1 from rising, and serves to prevent the epoxy resin, which is the main material of the core 1, from decomposing.

Therefore, when a conventional core made of epoxy resin was used, the surface part decomposed and gas was generated during pouring, whereas in the case of core 1 of this example 1, when pouring Since the epoxy resin is kept at a temperature below its decomposition temperature, no decomposition gas is generated and healthy cast products can be manufactured.

Such an effect can be obtained not only by using Sn powder but also by using various metal powders. Furthermore, the resin that is the main component of the core is not limited to epoxy resin, but can also be made by using a highly heat-resistant thermosetting resin and combining it with a metal powder whose melting point is lower than the decomposition temperature of this resin. Good.

Therefore, the metal powder (sample) to be mixed with the epoxy resin powder, which is the main component of the core, was replaced with the Sn powder (corresponding to sample 6 below): Sample 1: Powder diameter is 0.5 mm, melting point is 419 ° C. Zn powder sample 2
: Powder diameter is 0.5+nm, melting point is 410℃ (solidus temperature 3
Pb-10 wt% Zn powder at 15°C), sample 3: powder diameter Q, 1 mm, melting point 370°C (solidus temperature 19
Sample 4: Mg-5011 with a powder diameter of 0.3 mm and a melting point of 340°C
1t% Zn powder, sample 5: Pb powder sample 6 with a powder diameter of 0.1 mm and a melting point of 327°C
: Sn powder with a powder diameter of Q, 1 mm, and a melting point of 232°C (the Sn powder described above), Sample 7: Sn powder with a powder diameter of Q, 1 mrn, and a melting point of 228°C
- When using seven types of 1 wt% Al powder and further using the powder of sample 7, the volume % of the polyimide resin powder, which is the main material, was not only 30% but also (A) 3%, (B) 5%, (C) 10%.

(D) 30%, (E) 60%, (F) 70%,
Core 1 was molded under the same conditions as for the 3n powder, except that the compression molding temperature was 180°C.

Then, a cast product 7 was manufactured using the same casting material and casting conditions as when using the Sn powder.

As a result, as shown in Table 1, the metal powder to be mixed with the epoxy resin other than the Sn powder was the metal powder of sample 3, and the metal powder of sample 7 had a volume ratio of ( Good results were obtained when mixing at the mixing ratios shown in C) to (E).

Seiden ■-1 Next, as a comparative example, core 1 using only epoxy resin
A cast product 7 was manufactured using the same method and under the same conditions as in the case of casting using the core 1 of Example 1, and as shown in FIG. 3, a through hole 8 was provided and a T7 treatment was performed. .

When this cast product 7 was investigated, as shown in FIG. 4, although a cavity 9 was formed inside, it was found that cavities 10 were formed in a part of the cast product 7 due to epoxy resin decomposition gas.

Further, as Example 2, in Example 1, instead of the epoxy resin, polyimide resin having a decomposition vaporization temperature of 350° C. was used as the main material of the core 1, and as in Example 1, various metal powders were used. I changed it and molded the core.

The polyimide resin in Example 2 has a powder diameter of 1.
The metal powder (sample) to be mixed with this polyimide resin powder was the same as in Example 1.
When using seven types of metal powders from Samples 1 to 7, and further using the powder from Sample 7, the volume percentage of the polyimide resin, which is the main material, relative to the powder was only 30%, as in Example 1. In this test example, the compression molding temperature was changed to 7 stages (A) to (F).
Core 1 was prepared under the same conditions as in Example 1 except that the temperature was 0°C.
was molded.

Then, a cast product 7 was manufactured using the same casting material and casting conditions as in the case of casting using the core 1 of Example 1.

As a result, as shown in Table 1, in the case of core 1 made of polyimide resin mixed with 30% by volume of the metal powder of Samples 2 to 6, good cavities could be formed in the cast product 7, and no cavities etc. No gas defects occurred.

Furthermore, when the metal powder of Sample 7 was used, similarly good casting products 7 were obtained in the cores 1 whose volume ratios to the polyimide resin were expressed by the above (B) to (E).

This Atsumei-1 Next, as Comparative Example 2, using only polyimide resin,
As a result of molding a core] under the same conditions as in Example 2, and manufacturing a cast product 7 using the same casting material and casting conditions as in the case of casting using core 1 of Example 2, the inside of the product also As shown in FIG. 4, the occurrence of cavities 10 due to polyimide resin decomposition gas was observed (described in Table 1).

Furthermore, as Example 3, in Example 2, except that a phenol resin with a decomposition vaporization temperature of 320°C was used instead of the polyimide resin, and the compression molding temperature was 150°C.
Core 1 was molded under the same conditions as in Example 2 above.

However, when using the metal powder of sample 7, other samples 1 to 6
As in the case of using the phenol resin, the core 1 was molded with a volume ratio of only 30% to the phenol resin.

Then, using the same casting material and casting conditions as in the case of casting using the core 1 of Example 2, a cast product 7 having a shape as shown in FIG. 3 was manufactured.

As a result, as shown in Table 1, good results were obtained with sample 2, a metal powder of 3.6°7, as the metal powder to be mixed with the phenol resin.

Seiden A-Main Next, as Comparative Example 3, using only phenolic resin,
As a result of molding a core under the same conditions as in Example 3, and manufacturing a cast product 7 using the same casting material and casting conditions as in the case of casting using core 1 of Example 3, the inside of the product also The occurrence of cavities due to phenol resin decomposition gas was observed in Table 1.

Further, as Example 4, in Example 3, an unsaturated polyester resin having a decomposition and vaporization temperature of 200°C, the lowest decomposition and vaporization temperature compared to the above resin, was used instead of the phenol resin, and compression molding was performed. Core 1 was molded under the same conditions as in Example 3 except that the temperature was 80°C.

A cast product 7 was manufactured using the same casting material and casting conditions as in the case of casting using the core 1 of Example 3. As shown in Table 1, the metal powder mixed with the resin was the same as that of sample 3. Good results were obtained only with Zn-30%wtSn powder.

Kitasarago - ↓ Next, as Comparative Example 4, a core 1 was molded using only unsaturated polyester resin under the same conditions as in Example 4, and further, casting using core 1 of Example 4 was performed. As a result of manufacturing casting product 7 using the same casting material and casting conditions as in the case of Example 1, the occurrence of cavities due to unsaturated polyester resin decomposition gas was also observed inside the product (listed in Table 1).

Below is the margin △: A good cavity was formed, but a nest occurred.

×: Much gas is generated, and a cavity of the desired shape cannot be obtained.

...Other defects have occurred.

As can be seen from the above test results, when no metal powder is added to the core 1 whose main material is a thermosetting resin, the thermosetting resin, which is the main material, is made of epoxy resin, polyimide resin,
Whether phenolic resin or unsaturated polyester resin is used, gas defects 10 as shown in FIG. 4 occur inside the cast product 7.

On the other hand, it can be seen that gas defects can be prevented in the core 1 to which metal powder is added.

For example, when the main component of the core I is a polyimide resin, good results are obtained except in the case of Zn powder having a melting point higher than 350° C., which is the decomposition temperature of the polyimide resin. In the case of this Zn powder, since it does not melt and is stable up to 419° C., the effect of inhibiting the decomposition of the resin due to heat absorption during melting cannot be obtained.

On the other hand, the alloys Sample 2: Pb-10%Zn'- or Sample 3: Zn-30%Sn have melting points of 410°C and 370°C, respectively, and both melt at temperatures higher than the decomposition temperature of polyimide resin. However, in these cases, 3
Partial melting (corresponding to the solidus temperature in the phase diagram) occurs at 15° C. or 195° C., so an endothermic reaction suppresses the temperature rise and inhibits resin decomposition.

These things apply to other resins other than polyimide resins, and are effective when using metal powder that melts in whole or in part and causes an endothermic reaction at a temperature below the decomposition temperature of the resin that is the main component of the core. It turns out that

Here, the lower the melting point of the metal powder, the better.This is not the case; if it is too low, for example, if it melts below the resin molding temperature, the molten metal will aggregate during core molding, and later the casting Since the metal powder cannot be removed from the cavity 9 inside the product 7, it can be said that the melting point of the metal powder must be higher than the softening point of the resin.

Next, regarding the amount of metal powder added, the required amount is the combination of the polyimide resin of Example 2 and Sample 7 (Sn-1% AI! powder), and the combination of the epoxy resin of Example 1 and Sample 7.
From the results of the combinations, there is a difference in heat resistance of the resins, and when the polyimide resin of Example 2 is used as the main material, the volume ratio is 5%.
It can be seen that good results can be obtained with the above conditions, and in the case of the epoxy resin of Example 1, good results can be obtained with a volume ratio of 10% or more. The mixing ratio may be adjusted as appropriate depending on the combination of the resin, which is the main material of the core 1, and the metal powder to be mixed.

Note that when the mixing ratio is 70% or more by volume, no gas is generated and the core can be cast well. Problems such as requiring a long time to remove the resin component, or 2) the metal powder becoming sintered together after the resin removal and making it impossible to remove it from the cavity 9 of the cast product 7 may occur. Mixing ratio of metal powder (in volume ratio)
is preferably 60% or less.

Additionally, the size of the metal powder added to the resin powder of core 1 is not particularly restricted, but if it is too small, the metal powder tends to aggregate and sinter, and if it is too large, the resin powder The size of the metal powder to be added is 10 μm to 1 wm+ because the resin cannot be dispersed uniformly when mixed with the metal powder and the resin decomposes and vaporizes in areas where there is no metal powder during pouring.
It is preferable that it is in the range of .

As described above, JIS AC8A (AI-12%5t-1) is a cast product to which the core 1 according to the embodiment of the present invention is applied.
%Cu-1%Mg), the core of the present invention can be used not only for cast products made of the aluminum alloy, but also for cast products made of various metals such as magnesium alloys and zinc alloys. It can be used for manufacturing. In short, any resin may be used as long as it can be gasified and removed at the heat treatment temperature for casting.

〔effect〕

As described above, according to the present invention, the metal powder inside the core melts before the thermosetting resin, which is the main material of the core, decomposes during casting, and the heat of fusion is absorbed from the surroundings at that time. This prevents the temperature of the core from rising and keeps it below the decomposition temperature of the thermosetting resin, which has the excellent effect of preventing the occurrence of gas defects due to resin decomposition gas.

In addition, since the core can be molded using heat-resistant resin, it has the advantage of being easy to handle, inexpensive, and highly productive.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view of a core set showing a state in which a core according to an embodiment of the present invention is wrapped in a fiber molded body to be cast into molten metal, and FIG. 2 is a schematic cross-sectional view of a core set according to an embodiment of the present invention. Fig. 3 is a cross-sectional view of a cast product manufactured using a core according to an embodiment of the present invention, and Fig. 4 is a schematic cross-sectional view showing a state in which high-pressure casting is performed using a core. FIG. 1 ... Core 7 ... Casting product (hollow casting)

Claims (1)

[Claims] (1) A core for manufacturing hollow castings whose main component is a thermosetting resin, wherein the thermosetting resin powder has a temperature higher than the softening temperature of the resin and a decomposition vaporization temperature of the resin. Metal powder or alloy powder that partially or completely melts and causes an endothermic reaction at a temperature lower than
1. A core for manufacturing hollow castings, characterized in that the mixture is mixed in a range of 60% and formed by compression molding.