JPH05154639A - Cast-in pipe casting method - Google Patents

Abstract

PURPOSE:To surely prevent defect of blow holes, etc., caused by gas generation around a pipe and to efficiently mass-produce the high quality cast products in high yield and low cost in the casting of the aluminum cast product forming pipe line by the cast-in of the aluminum pipe arranging a heat resistant film on the surface. CONSTITUTION:In the cast-in pipe casting method manufacturing the pipe line 5 of the aluminum cast product M by arranging the aluminum pipe 6 having a heat resistant film 8 on the surface and pouring the molten aluminum the aluminum pipe 6 providing plural small holes 7 penetrated from the inside to the outside on the peripheral surface is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pipe stuffing cast method for forming a pipe line of an aluminum cast product by loading and casting an aluminum pipe in a mold. 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 circulating 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. 1, 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.

In particular, the latter cast-in-gurg method has an advantage that the former mechanical work can be omitted and it is suitable for mass production, and a curved pipe line which is difficult or impossible to form by mechanical work can be easily formed. .. In particular, 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 may vary depending on the shape of the casting and the casting conditions. There is a problem in that gas is generated around the pipe due to the decomposition of the above, and defects such as porosity caused by the gas may occur, and in particular, when the wall thickness fluctuation around the pipe is large, defects are likely to occur.

In view of the above situation, an object of the present invention is to generate gas around the pipe in casting of an aluminum cast product in which a pipe is formed by a cast stuffed 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 that can reliably 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-mentioned object, in the pipe cast-in-girth casting method according to claim 1 of the present invention, an aluminum pipe having a heat-resistant coating on its surface is placed in a mold to melt the molten aluminum. In the case of the cast-in-gurumi casting method in which the pipe is cast to form a pipe line of an aluminum cast product by pouring molten metal, the aluminum pipe having a plurality of small holes penetrating inside and outside the peripheral surface is used. It adopts a configuration characterized by being used.

[0007] A pipe swirl casting method according to a second aspect of the present invention is the casting method of the first aspect, wherein the small holes have a diameter in the range of 0.5 to 2.0 mm. is there.

[0008]

[Function] When an aluminum pipe for forming a pipe is filled in a mold and molten metal is poured, elution of the pipe is prevented by a heat-resistant coating on the surface, but when the variation in wall thickness around the pipe is large Since the solidification is delayed in the thick part, 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 a gas, and this gas causes a porosity in the thick part. 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 blow holes caused by this gas can be reliably avoided.

The small holes of the aluminum pipe may be formed by drilling or pressing, but if the hole diameter is too large, the molten metal may flow into the pipe, and conversely if it is too small, gas may be discharged. Becomes insufficient, 1.0-
A hole diameter range of 2.0 mm is preferable, and it has been confirmed that gas can be efficiently discharged in this range without causing the above-mentioned inflow 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 casting, and the likelihood of cavities and the like that can be empirically known. 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 that have been conventionally used, for example, the 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 such as salts and chromates, and oxide coatings obtained by coating and drying a dispersion liquid of a metal oxide powder or an easily oxidizable metal powder 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 aluminum pipe having the heat-resistant coating and the small holes is set in the lower mold in a predetermined position before and after 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 into the pipe from the small holes,
It is recommended that the pipe is arranged such 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. 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 material (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 manufactured by applying the casting method of the present invention, and FIG. 3 (A) shows the casting of the manifold M. A vertical section along line III-III is shown below. 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 ... Mounting flange 3
And a cross bar 4 connecting the branch pipes 2 ... on the front side of the intermediate portion (FIG. 1) is provided, and the cross bar 4 is a straight pipe in a direction substantially perpendicular to each branch pipe 2. The PCV pipeline 5 forming the above 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 manufacturing the intake manifold M, as shown in FIG. 3 (B), first, a plurality of small holes 7 are formed on the peripheral surface of the aluminum pipe 6 so as to penetrate the inside and outside thereof, and then the pipe 6 is made. A heat resistant coating 8 is formed on the entire surface. 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 was 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 was 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 the respective joint portions 4a, the solidification of this portion is delayed compared with the other portions, and the heat resistant coating 8 is formed.
Although gas is likely to be generated due to partial decomposition of the gas, since the gas is discharged to the outside through the small holes 7 ... through the pipe 6, generation of porosity due to the gas is prevented. Next, an example in which actual casting is performed will be specifically described.

Examples 1 to 8 Small holes (hole diameters shown in Table 1 below) that 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 section 4 and the branch pipes 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 thin portion from the header 1 to each branch pipe 2 has a thickness of 3 to 5 m in the structure shown in FIGS. 1 and 2.
A m intake manifold cast product was produced.

Comparative Example An intake manifold cast product was produced in the same manner as in the example except that an aluminum pipe having a heat resistant coating formed without forming 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 molten aluminum inflow state into the pipe line 5) and the generation state of the porosity in the horizontal cross section 4 were examined, the results shown in Table 1 below were obtained.

[0019]

[Table 1]

[0020]

EFFECT OF THE INVENTION 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 its surface in the production of cast aluminum, the peripheral surface of the pipe 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.

Further, according to the second aspect of the present invention, there is an advantage that it is possible to reliably prevent the occurrence of defects such as the above-mentioned porosity without flowing the molten aluminum 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.

FIG. 3 (A) is a sectional view of a portion corresponding to the line III-III in FIG. 1 in the intake manifold after casting.

FIG. 3 (B) is a vertical cross-sectional view of a cast-mold aluminum pipe forming a PCV pipe line of the intake manifold.

[Explanation of symbols]

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

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[Procedure amendment]

[Submission date] November 26, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[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 a cross-sectional view of a portion corresponding to the line AA of FIG. 1 in the intake manifold after casting, and FIG. 3 (B) is a vertical cross-section of a cast aluminum tube constituting a PCV pipeline of the intake manifold. Face view.

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

Claims (2)

[Claims] 1. An aluminum pipe having a heat-resistant coating on its surface is placed in a mold to pour molten aluminum,
In the case of a round-the-wall cast casting method in which the pipe is cast to form a pipe line of an aluminum cast product, the aluminum pipe having a plurality of small holes penetrating inside and outside is used as the aluminum pipe. Pipe cast and cast method. 2. The pipe stuffed cast method according to claim 1, wherein the diameter of the small holes is in the range of 0.5 to 2.0 mm.