JPH07102442B2 - Pipe casting - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pipe stuffed cast method for forming a pipe line of an aluminum cast product by loading an aluminum pipe into a mold and casting the aluminum pipe. It is suitable for use in the production of various cast aluminum products.

[0002]

2. Description of the Related Art In recent years, in an air supply manifold for an automobile engine, an exhaust gas circulation pipe and a PCV are provided together with a distribution pipe for supplying an original fuel gas-air mixture to each cylinder.
The one with a conduit for (purge control valve) is commonly used. A cast product made of an aluminum alloy is generally used for such an air supply manifold. However, when the circulation pipe line, the PCV pipe line and the like are integrated into the manifold body, the pipes are thin and long, and therefore, cast. Since it is difficult or impossible to set with the mold configuration of No. 3, the thick part previously provided in the casting is perforated by mechanical processing after casting, or it is cast by loading an aluminum pipe in the mold (pipe gurney method) Thereby, the means for forming the conduit is adopted.

[0003] In particular, the latter case of the cast-in-gurgling method is advantageous in that the former can eliminate the trouble of mechanical processing and is suitable for mass production, and can easily form a curved pipe line which is difficult or impossible to form by mechanical processing. . Particularly, by forming various heat-resistant coatings such as the chemical conversion coating disclosed in Japanese Patent Publication No. 57-31499 on the surface of the pipe, it is possible to prevent melting damage of the pipe during casting.

[0004]

However, when an aluminum pipe having a heat-resistant coating on the surface as described above is used in the pipe casting process, a part of the coating depends on the shape of the casting and the casting conditions. There is a problem in that gas is generated around the pipe due to decomposition of the gas, and defects such as cast holes caused by the gas are generated, and defects are likely to occur particularly when the wall thickness fluctuation around the pipe is large.

In view of the above-mentioned situation, the object of the present invention is to generate gas around the pipe in casting an aluminum cast product in which a pipe path is formed by a cast hole of an aluminum pipe having a heat-resistant coating on its surface. It is an object of the present invention to provide a casting method excellent in practicability, which can surely prevent defects such as cavities and enables high-quality cast products to be mass-produced efficiently at low cost with high yield.

[0006]

[Means for Solving the Problems] As means for achieving the above object, according to a first aspect of the present invention, in a cast-pipe stuffing and casting method, an aluminum pipe having a heat-resistant coating on its surface is placed in a mold to melt an aluminum melt. In the case of the cast-in-turn casting method in which the pipe is cast to form a pipe line of an aluminum cast product by pouring, the aluminum pipe having a plurality of small holes penetrating the inside and outside of the peripheral surface is used. It adopts a configuration characterized by being used.

[0007] In the above-mentioned pipe-casting stuffing method, small holes
It is intended to be within the range in diameter of 0.5 to 2.0 mm.

[0008]

When the aluminum pipe for forming the pipeline is poured into the mold and the molten metal is poured, the elution of the pipe is prevented by the heat-resistant coating on the surface, but when the variation in the wall thickness around the pipe is large Since solidification is delayed in the thick wall portion, the heat resistant coating at that position has a long contact time with the high temperature molten metal and is likely to be partially decomposed to generate gas. Defects such as (so-called shrinkage cavities) will occur. However, in the configuration of the present invention, since the above-mentioned gas is discharged to the outside through the inside of the pipe through the small hole of the pipe, defects such as blowholes caused by this gas can be reliably avoided.

The small holes of the aluminum pipe may be formed by drilling with a drill or pressing, but if the hole diameter is too large, the molten metal may flow into the pipe, and if it is too small, gas is discharged. Is insufficient, so 1.0-
A hole diameter range of 2.0 mm is preferable, and it has been confirmed that gas can be efficiently discharged without causing the above-mentioned inflow in this range due to the viscosity of the molten aluminum and the like. Further, the number and position of the small holes may be appropriately set according to the shape and thickness of the pipe casting portion of the aluminum cast product, and the easiness of occurrence of cavities and the like that can be empirically known, but focus on the thick portion. It is better to set it to be placed in.

The heat-resistant coating formed on the surface of the aluminum pipe is not particularly limited, and various coatings conventionally used, for example, phosphates and halogens disclosed in the above Japanese Patent Publication No. 57-31499. Various chemical conversion coatings formed by surface treatment using an aqueous salt solution of salts such as salts and chromates, and oxide coatings obtained by coating and drying dispersion liquids of metal oxide powders and easily oxidizable metal powders are preferably used. obtain.
The coating can be formed before the formation of the small holes, but from the viewpoint of avoiding elution of the inner peripheral surface of the small holes, it is possible to form the coating on the inner peripheral surface after forming the small holes. desirable.

During casting, the upper and lower molds are preheated, and the lower mold is set to the required position where the aluminum pipe having the heat-resistant coating and the small holes is formed in front of and behind the core. The upper mold may be covered with the lower mold, and molten aluminum may be poured into the mold. Therefore, it is preferable that the inside of the pipe communicates with the outside of the mold at least at one end side. Also, in order to avoid the inflow of molten aluminum from the small holes into the pipe,
It is recommended that the pipes be arranged so that the small holes are slightly displaced from the inflow direction of the molten aluminum. The preheating temperature is usually 330 to 430 ° C. for the upper mold and 280 to 3 for the lower mold.
About 30 ℃, the temperature of molten aluminum is 670-750 ℃
It is a degree. The term aluminum used in the present invention includes aluminum and its alloys.

The pipe formed by casting the aluminum pipe may be either a straight pipe or a curved pipe, and in the case of a curved pipe, a bent pipe may be used. In addition, by loading a heat-resistant solid material such as a metal rod-shaped material (for straight pipes) or a metal stranded wire (for curved pipes) into the pipe within the range where the air permeability inside the pipe can be secured, It is also possible to increase the heat capacity of the pipe and decrease the temperature rise of the pipe.

[0013]

1 and 2 show an intake manifold M for a four-cylinder automobile engine made of an aluminum casting produced by applying the casting method of the present invention. FIG. 3 (A) shows the casting of the manifold M. The longitudinal cross section in the subsequent figure AA line is shown. In this manifold M, four branch pipes 2 ... Corresponding to each cylinder of the engine extend from an intake header 1 that introduces a gasoline-air mixture, and the ends of these branch pipes 2 ... Is provided with a mounting flange portion 3 for connecting the branch pipes 2 to the front side of the intermediate portion (FIG. 1). A PCV conduit 5 having a straight tubular shape extending in a substantially right-angled direction is formed by casting an aluminum pipe 6. The wall thickness around the PCV conduit 5 is large at the joint portion 4a between the cross rail 4 and each branch pipe 2.

In the manufacture of the intake manifold M, as shown in FIG. 3B, first, a plurality of small holes 7 ... A heat resistant coating 8 is formed on the entire surface. It should be noted that in this case, two small holes 7 are arranged at a position corresponding to each joining portion 4a of the cross rail 4 and each branch pipe 2, and a total of eight small holes 7 are arranged on a straight line along the pipe longitudinal direction. It is provided. Next, the pipe 6 is set with the core in the lower mold of the preheated mold with the small hole 7 being slightly displaced from the inflow direction of the molten aluminum, and the lower mold is covered with the preheated upper mold. The molten aluminum is poured into the inside, taken out from the mold after solidification, and then machined to form mounting tap holes etc.
And the structure of FIG.

However, during casting, since the thickness of aluminum is large around the pipe 6 at each of the joint portions 4a, solidification of this portion is delayed compared to other portions, and the heat resistant coating 8 is formed.
Although gas is apt to be generated due to partial decomposition of the gas, the gas is discharged to the outside through the small holes 7 ... Next, an example of actual casting will be specifically described.

Examples 1 to 8 Small holes (hole diameters shown in Table 1 below) which penetrate the inside and outside of the aluminum pipe (melting point 660 ° C.) having a thickness of 1 mm and an outer diameter of 10 mm are formed on the peripheral surface of FIG. After forming two pipes at positions corresponding to the joint portions 4a of the portion 4 and each branch pipe 2, the pipes were degreased with an aqueous sodium hydroxide solution, neutralized with an aqueous nitric acid solution, and washed with water. It was immersed in a 3 wt% aqueous zinc fluoride solution at room temperature for 10 minutes, washed with water and dried at 100 to 120 ° C. for 10 minutes to form a heat resistant coating. Next, a small hole is placed in the lower mold of the mold preheated to 280 to 350 ° C. from the inflow direction of the molten aluminum.
Set it with the core in the direction shifted by 5 degrees, cover this lower mold with the upper mold preheated to 330 to 430 ° C., and then 670
The molten aluminum is poured at ˜750 ° C., the solidified casting is taken out from the mold after 2 minutes, and the thickness of the thin portion from the header 1 to each branch pipe 2 is 3 to 5 m in the structure shown in FIGS. 1 and 2.
m intake manifold cast product was produced.

Comparative Example An intake manifold cast product was manufactured in the same manner as in the example except that an aluminum pipe having a heat resistant coating formed without small holes was used.

The pipe 6 (PCV) was attached to each intake manifold cast by the methods of the above-mentioned examples and comparative examples.
When the state of inflow of the molten aluminum into the pipe line 5) and the state of generation of the porosity in the horizontal rail portion 4 were examined, the results shown in Table 1 below were obtained. As is clear from Table 1, the diameter of the small hole
Is within the range of 0.5 to 2.0 mm, the
It is confirmed that there is almost no inflow of Lumi molten metal and no occurrence of porosity.
It has been certified.

[0019]

[Table 1]

[0020]

According to the cast-in-gurney casting method of the present invention, when a pipe path is formed by cast-inducing aluminum pipe having a heat-resistant coating on the surface thereof in the production of cast aluminum, the peripheral surface of the pipe is formed. By a simple means of only providing a small hole for degassing, it is possible to prevent the occurrence of defects such as blowholes due to the gas generation around the pipe, and thus to obtain a high-quality cast product having the above-mentioned pipeline with a high yield. It can be manufactured efficiently and at low cost.

In the present invention, the diameter of the small holes is 0.5 to.
Within the range of 2.0 mm, it is possible to reliably prevent the occurrence of defects such as the above-mentioned porosity without causing the molten aluminum to flow into the cast aluminum pipe.

[Brief description of drawings]

FIG. 1 is a front view of a four-cylinder intake manifold for an automobile engine, which is an example of an aluminum cast product manufactured by applying the present invention.

FIG. 2 is a side view of the intake manifold.

3 (A) is an enlarged cross-sectional view taken along line AA of FIG. 1 in the intake manifold after casting, and FIG. 3 (B) is the intake manifold.
Aluminum pad for cast doll that composes hold PCV conduit
A vertical cross-sectional view of the ip .

[Explanation of symbols]

 5 PCV Pipeline (Pipelined Pipeline) 6 Aluminum Pipe 7 Small Hole 8 Heat Resistant Coating M Intake Manifold (Aluminum Cast)

Claims (1)

[Claims] 1. An aluminum pipe having a heat-resistant coating on its surface is placed in a mold and molten aluminum is poured,
In the case of the cast-in-gurumi casting method in which the pipe is cast to form a pipe line of an aluminum casting, the diameter of the aluminum pipe that penetrates the inside and outside of the peripheral surface is in the range of 0.5 to 2.0 mm.
A cast-in-a-roll casting method characterized by using one having a plurality of small holes.