KR20030013958A - Method for manufacturing a cylinder head of cast aluminum alloy for internal combustion engine by rapid cooling using liquid Air - Google Patents

Abstract

PURPOSE: A method for micronizing structure of cylinder head of cast aluminum alloy for internal combustion engine is provided to manufacture stable cylinder heads of high quality by rapidly cooling a port portion using liquid air having a temperature of about -200 deg.C inside a dies. CONSTITUTION: The method comprises the steps of melting aluminum alloy as a material for the cylinder heads in a melting furnace having a temperature of 750 to 770 deg.C; injecting the melted aluminum alloy into a mold(30) in dies(10) that is designed in a certain shape; casting cylinder heads by forming the aluminum alloy injected into the mold at a temperature of 680 to 740 deg.C; manufacturing cylinder heads by adjusting cooling of the cast cylinder heads using the liquid air(60), wherein the method further comprises the step of preheating the dies to a temperature of 150 to 250 deg.C so as to prevent the melted aluminum from solidifying before the step of injecting the melted aluminum alloy into a mold in the dies(10).

Description

{Method for manufacturing a cylinder head of cast aluminum alloy for internal combustion engine by rapid cooling using liquid Air}

The present invention relates to a method for finely organizing a cylinder head, and more particularly, to melting aluminum alloy during casting of a cylinder head, injecting the molten alloy into a mold, forming a cylinder head, and cooling using a refrigerant. It relates to a method for miniaturizing the tissue of the cylinder head by performing a step.

The cylinder head for a vehicle engine has a tendency to increase the required physical property ratio due to the ignition at the start and the high output of the engine.

In particular, as shown in FIG. 1, the intake and exhaust ports 2 and 4 of the cylinder head are exposed to high heat due to explosion pressure and combustion, and therefore, improvement of quality is required.

As a method of improving the quality and increasing the physical properties while using the same material, there is a method of refining the tissue by rapid cooling during solidification.

In general, as shown in FIG. 2, a method of refining a structure by water cooling or air cooling of a mold during casting is used. In contrast, Toyota Corporation of Japan As shown in FIG. 3, the intake and exhaust ports of the cylinder using a high energy source 6 such as a TIG arc, a laser, a plasma arc, an electron beam, etc. 2,4) A tissue refining method is used in which the peripheral part is partially dissolved and then resolidified.

As described above, the prior art can be broadly classified into a method of refining the structure during casting by air cooling or water cooling, and a method of refining the structure by remelting using a high energy source after casting.

The conventional tissue refinement method causes the following problems.

First, the method of microstructure by remelting using a high energy source is solidified by rapid cooling after the alloy is melted, and thus internal defects such as fine pin holes, blow holes, or shrinkage cavities. It can have a and the area that can be remelted is limited, so the re-melting operation must be performed several times, so there may be a quality difference for each part.

In addition, the melting apparatus by the high energy source is difficult to control and there is a problem that the product cost increases when applied.

On the other hand, the structure microstructure method in casting using water cooling or air cooling has a limitation in miniaturizing the structure by the heat capacity.

Therefore, the present invention is to solve the above problems and to produce a more stable and high-quality cylinder head, a new method of rapidly cooling the port area by using a refrigerant (temperature about -200 ℃) in the mold It is an object of the present invention to provide a method for refining a structure of an engine cylinder head using a refrigerant.

1 is a schematic view showing a port portion of a cylinder head of an automotive engine;

Figure 2 is a conventional cylinder head manufacturing method, a schematic diagram showing a method of microstructure using water cooling or air cooling during casting,

3 is a schematic diagram showing a conventional method for manufacturing a cylinder head, a method for refining a tissue to remelt a high energy source after casting;

Figure 4 is a schematic diagram showing a method of achieving microstructure by performing rapid cooling of the port portion by using an insert mold in contact with the refrigerant inside the mold during the cylinder head casting of the present invention,

Figure 5 is a photograph of the surface observed with an optical microscope of the surface of the cylinder head prepared according to the embodiment of the present invention.

<Brief description of the major symbols in the drawings>

2: intake port 4: exhaust port

6: high energy source 10: mold

20: tap 30: mold

40: insert mold 50: ceramic insulation layer

60: refrigerant (liquid nitrogen, oxygen, etc.)

In order to achieve the above object, the present invention

Melting the aluminum alloy (step 1);

Injecting the molten aluminum alloy into the mold (step 2);

Molding at 680-740 ° C. (step 3); And

It provides a method for microstructure of the cylinder head consisting of a step (step 4) of cooling using a refrigerant.

Hereinafter, the present invention will be described in detail for each step.

In step 1, the aluminum alloy is melted in a melting furnace at 750 to 770 ° C. using the aluminum alloy as the material of the cylinder head.

As the high power of the engine is required, the aluminum alloy can achieve a light weight of the cylinder head while improving various mechanical properties including heat resistance in manufacturing a cylinder head that can withstand increasingly high loads, high temperatures, and high pressures.

In step 2, the molten aluminum alloy is injected into the mold in step 1.

Step 2, as shown in Figure 4, the molten aluminum alloy is injected into the mold 30 consisting of sand in the mold 10, but is slowly injected through the spout 20.

At this time, the mold 10 is preheated to 150 ~ 250 ℃ to prevent the molten aluminum is solidified.

The mold 10 used in the present invention includes a mold 30 made of sand to manufacture a port portion, an insert mold 40 in contact with a refrigerant for cooling the formed cylinder head, an insert mold 40 and a casting mold. 10 and the ceramic thermal insulation layer 50 for blocking the temperature, the refrigerant 60 for lower cooling.

The structure is not limited in the present invention, and various devices may be additionally added by those skilled in the art.

In step 3, the aluminum alloy injected into the mold in step 2 is molded at 680 to 740 ° C to cast a cylinder head.

In particular, step 4 completes the present invention by manufacturing a cylinder head by adjusting the cooling step using a refrigerant.

In the step 4, the surface of the cylinder head is refined by adjusting the cooling rate by using the apparatus consisting of the insert mold 40, the ceramic insulation layer 50, and the coolant 60 in the cylinder head being formed in the step 3.

As shown in FIG. 4, the insert mold in contact with the coolant is embedded in the mold 10 and serves to solidify the metal by absorbing heat in the mold after molding.

As a result, by using the refrigerant of the present invention, it is possible to overcome the risk of breakage and explosion of the mold, the porosity, and the quality difference for each part, which are problems in using the conventional method for fine tissue.

In addition, the cooling method using the refrigerant of the present invention makes it possible to manufacture a cylinder head having a uniform particle size with high mechanical strength by locally maintaining the cooling temperature at about -50 to 100 ℃.

According to the embodiment of the present invention, the observation of the surface of the cylinder head cooled by the refrigerant confirms that the alloy is uniformly distributed in an average size of 15 μm.

Therefore, according to the present invention, the cylinder head manufactured by melting an aluminum alloy and then molding it into a mold and cooling by using a refrigerant may have excellent mechanical strength and physical properties, thereby achieving lighter weight and higher output of the engine.

It will be described below in detail by the following examples.

The following examples are merely illustrative of the present invention, but the content of the present invention is not limited to the following examples.

<Example 1>

Specimens were prepared as follows using the cylinder head tissue micronization method of the present invention.

First, aluminum alloy was melted at 750 ° C. and injected into a mold preheated to 180 ° C. (see FIG. 4).

Injected into the mold 30 in the mold 10, but slowly injected through the spout 20 to form a cylinder head. Finally, the microstructure was completed by setting the upper temperature of the insert mold 40 connected to the refrigerant 60 to 10 ° C. and the cooling time of 4 minutes.

The surface of the cylinder head manufactured according to the embodiment of the present invention was photographed with an optical microscope and shown in FIG. 5.

The surface of the cylinder head was confirmed that the particle size is uniform 15㎛ on average.

Comparative Example 1

Specimens were prepared as follows by using a structure micronization method by water cooling when casting a cylinder head of the prior art (see FIG. 2).

First, the aluminum alloy was melted at 750 ° C. and injected into a mold of a mold preheated to 180 ° C. to form a cylinder head. Finally, the tissue micronization by water cooling was completed by injecting water at 20 ° C. as shown in FIG. 2.

Experimental Example 1

The specimens prepared in Example 1 and Comparative Example 1 were compared with the following mechanical strength and surface particle size.

Tensile strength (MPa): Tensile strength was measured by the test method of KS B0802 and the results are shown in Table 1 below.

Yield strength (MPa): Yield strength was measured by the test method of KS B0802 and the results are shown in Table 1 below.

Surface particle size: Surface particles were observed by the electron scanning microscope surface of the cylinder head and the results are shown in Table 1.

Mechanical Strength vs. Surface Particle Size division Tensile Strength (Mpa) Yield strength (Mpa) Surface Particle Size (㎛) Example 1 290 200 15 Comparative Example 1 250 180 25

As shown in Table 1, the tensile strength and the yield strength were greatly improved when the specimen prepared by the method of microstructure using the refrigerant of the present invention in the manufacture of the cylinder head was compared with the specimen prepared according to the prior art. The size is much smaller and uniform.

According to the above results, it can be seen that by using the microstructured microstructure method of the present invention, a cylinder head capable of withstanding high loads, high temperatures, and high pressures can be manufactured according to high engine output.

As described above, the present invention is more than a certain thickness to prevent the risk of explosion due to rapid breakdown of the mold, explosion of the molten metal and water when using the structure micronizing method during casting by water cooling and air cooling used in the past Not only does it eliminate the cooling line design problem, but also overcomes the porosity and the quality difference between parts due to rapid solidification after melting when using a separate high energy source. It is possible to obtain the desired cylinder head port quality.

Claims (2)

In the manufacturing method of the cylinder head Melting in a 750 to 770 ° C. melting furnace using aluminum alloy as the material of the cylinder head; Injecting the molten aluminum alloy into a mold in a mold designed to a predetermined shape; Casting the cylinder head by molding the aluminum alloy injected into the mold at 680 to 740 ° C; Manufacturing a cylinder head by adjusting to cooling using a refrigerant; Method for miniaturizing the structure of the engine cylinder head using a refrigerant. The method of claim 1, wherein the mold (10) is preheated to 150 to 250 ℃ to prevent the molten aluminum to solidify the method of miniaturizing the engine cylinder head using a refrigerant.