KR101786344B1 - Aluminum alloy for cylinder head method for manufacturing cylinder head using the same - Google Patents

Abstract

The present invention relates to an aluminum alloy for a cylinder head having excellent thermal conductivity and tensile strength at a high temperature formed during operation of a cylinder, and a method of manufacturing a cylinder head using the aluminum alloy. The aluminum alloy for a cylinder head according to an embodiment of the present invention, 1. An aluminum alloy for a cylinder head for use in an engine of a vehicle, comprising: 1 to 3% Si, 2 to 4% Cu, 0.1 to 0.4% Mg, 0.2 to 0.4% Fe, %, Ti: 0.02% or less (excluding 0%), the remainder Al and unavoidable impurities.

Description

Technical Field [0001] The present invention relates to an aluminum alloy for a cylinder head, and a method of manufacturing the cylinder head using the same. BACKGROUND OF THE INVENTION 1. Field of the Invention [0001]

The present invention relates to an aluminum alloy for a cylinder head and a method of manufacturing a cylinder head using the aluminum alloy. More particularly, the present invention relates to an aluminum alloy for a cylinder head having excellent thermal conductivity and tensile strength at high temperatures, And a method for producing the same.

The cylinder head is the main part of the engine, the part serving as the inlet of the fuel and air, and the outlet of the combustion gas. Normally, the bottom temperature of the cylinder head rises to about 200 ° C due to explosion in the combustion chamber. When the temperature of the combustion chamber rises, automatic ignition of the fuel occurs and knocking phenomenon occurs. When the knocking phenomenon occurs, the durability of the engine is lowered and the fuel consumption is lowered.

In order to prevent knocking in the combustion chamber, the heat generated after the explosion must be released quickly. Therefore, when a cylinder head is manufactured from a material having a high thermal conductivity, the heat transferred from the combustion chamber to the head is rapidly discharged to the outside, thereby preventing the knocking phenomenon.

Conventional cylinder heads are manufactured using AC2BH alloy and A356H alloy, which are alloys of Al-Si-Cu series.

The AC2BH alloy contains, by wt%, 5 to 7% of Si, 2 to 4% of Cu, 0.1 to 0.4% of Mg, 0.03% or less of Mn, 0.3% or less of Zn, 0.25% or less of Fe, By mass, Cu: not more than 0.2%, Mg: not more than 0.2%, Mn: not more than 0.05%, and most preferably not more than 0.03%, and the balance Al and inevitable impurities. , Zn: not more than 0.1%, Fe: not more than 0.2%, Ni: not more than 0.1%, Ti: not more than 0.25%, and the balance Al and unavoidable impurities.

The AC2BH alloy subjected to the T7 heat treatment exhibited a yield strength of 251 MPa, a tensile strength of 288 MPa, a elongation of 1.2%, a thermal conductivity of 154 W / mK at 25 ° C. and a transmittance of 160 W / mK at 200 ° C. The A356H alloy, A yield strength of 226 MPa, a tensile strength of 277 MPa, a elongation of 5.5% and a thermal conductivity of 114 W / mK at 25 DEG C and 117 W / mK at 200 DEG C.

They have improved strength and castability through the Al ₂ Cu strengthening phase and the Si crystallization. However, if too many of these crystallizations are produced, this will cause the thermal conductivity to decrease.

The cylinder head must maintain high strength and thermal conductivity under a high temperature environment. In the case of conventional AC2BH alloy or A356H alloy, however, the cylinder head satisfies the strength but lacks thermal conductivity.

Accordingly, there is a demand for a new aluminum alloy which can maintain the thermal conductivity at a high temperature (200 캜) formed while the cylinder is operating, while maintaining the same or higher strength as compared with the conventional alloy.

Korean Patent Publication No. 10-2004-0095437 (November 15, 2004)

An object of the present invention is to provide an aluminum alloy for a cylinder head capable of maintaining a high thermal conductivity and strength at a high temperature formed during operation of the cylinder, and a method of manufacturing the cylinder head using the same.

An aluminum alloy for a cylinder head according to an embodiment of the present invention is an aluminum alloy for a cylinder head used in an engine of a vehicle, which comprises 1 to 3% of Si, 2 to 4% of Cu, 0.1 to 0.4% of Mg, , Fe: 0.2 to 0.4%, Ni: 0.1 to 1%, Ti: 0.02% or less (excluding 0%), the remainder Al and unavoidable impurities.

Wherein the aluminum alloy has a thermal conductivity of 200 W / mK or more at 200 ° C and a tensile strength of 290 MPa or more.

Further, the aluminum alloy is characterized in that Al ₃ Ti is formed as a reinforcing phase.

At this time, the aluminum alloy is a strengthened phase and is characterized in that Al ₃ Ti is formed in an amount of 0.003 to 0.03 wt% relative to the total weight of the aluminum alloy.

A method of manufacturing a cylinder head according to an embodiment of the present invention includes a step of preparing a cylinder head for use in an engine of a vehicle, which comprises 1 to 3% of Si, 2 to 4% of Cu, 0.1 to 0.4% of Fe, 0.2 to 0.4% of Fe, 0.1 to 1% of Ni, 0.02% or less of Ti (exclusive of 0%), Al and unavoidable impurities are cast to produce a cylinder head shaped article , The molded product is subjected to a solution treatment and then an aging heat treatment is carried out so as to be overblown.

At this time, the aging heat treatment is performed at a heat treatment temperature of 180 to 200 ° C for 12 hours or more.

The aluminum alloy for a cylinder head according to the present invention and the method for manufacturing a cylinder head using the aluminum alloy according to the present invention have the following effects.

First, it is possible to maintain a high thermal conductivity at a high temperature formed during the operation of the cylinder, thereby preventing the knocking phenomenon.

Second, it can be used for a cylinder head while maintaining strength equal to or higher than conventional alloys.

1 is a graph showing types and amounts of reinforcing phases when an aluminum alloy according to an embodiment of the present invention is subjected to aging heat treatment at 190 ° C,
2 is a graph showing types and amounts of reinforcing phases when the aluminum alloy according to an embodiment of the present invention is subjected to an age heat treatment at 250 ° C,
FIG. 3 is a graph showing the types and amounts of reinforcing phases when an aluminum alloy containing 0.05% of Ti is subjected to an aging heat treatment at 190 ° C,
4 is a graph showing changes in thermal conductivity and tensile strength according to Ti content of an aluminum alloy according to embodiments of the present invention,
5 is a graph showing changes in thermal conductivity according to the aging heat treatment temperature and the Ti content of the aluminum alloy according to the embodiments of the present invention,
6 is a graph showing tensile strength changes according to the aging heat treatment temperature and the Ti content of the aluminum alloy according to the embodiments of the present invention,

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It will be apparent to those skilled in the art that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, It is provided to let you know.

Hereinafter, an aluminum alloy for a cylinder head according to a preferred embodiment of the present invention and a method for manufacturing a cylinder head using the aluminum alloy will be described with reference to the accompanying drawings.

Firstly, the aluminum alloy for a cylinder head is made of aluminum alloy containing 1 to 3% by weight of Si, 2 to 4% of Cu, 0.1 to 0.4% of Mg, 0.2 to 0.4% of Fe, 0.1 to 1% To 0.02%, residual Al and unavoidable impurities.

Next, the reason for the numerical limitation for each component will be described.

Si: As an element to be added for improving the casting composition, it is necessary to add 1% or more in order to secure castability. However, when added in an amount exceeding 3%, the thermal conductivity at a high temperature is greatly decreased. do.

Cu: Al ₂ Cu It is an element that forms a strengthened phase to increase the strength of the aluminum alloy. At least 2% addition is required for this. However, when it is added in an amount exceeding 4%, the strength is improved but the thermal conductivity is lowered.

Mg: Mg ₂ Si strengthening phase to improve strength. For this strengthening effect, addition of 0.1% or more is necessary. However, when it is added in excess of 0.4%, the production of the Mg-Cu-Ni-based crystallized product is increased and the thermal conductivity at high temperature is lowered.

Fe: It is an effective element for improving the strength and preventing mold sticking. For this effect, it is necessary to add 0.2% or more, but when it is added in excess of 0.4%, the fraction of the iron-based alloy phase is increased and the high-temperature thermal conductivity is lowered.

Ni: It is an element which forms an Al3Ni strengthened phase to improve the strength and improve the casting. In the present invention, the content of Si is decreased to decrease the main composition, which can be compensated by the addition of Ni. For this effect, the addition of 0.1% or more is required, but when it is added in an excess amount exceeding 1%, a large amount of crystallized product is formed and the thermal conductivity at a high temperature is lowered.

Ti: It is an element which is effective in improving the strength by making the crystal grain size fine and improving the strength through the Al ₃ Ti strengthening phase. In order to obtain such an effect, it is necessary to add 0.01% or more, but when it is added in excess of 0.02%, an excessive crystallization phase is formed and the thermal conductivity at high temperature is lowered.

The remainder of the aluminum alloy, except for the aforementioned components, consists of aluminum (Al) and other inevitable impurities.

In order to manufacture a cylinder head having excellent thermal conductivity and strength characteristics at high temperatures, molten steel having the above composition is manufactured using a conventional cylinder head manufacturing method. In a typical method for manufacturing a cylinder head, cast molten steel whose components are adjusted is cast to produce a molded product, followed by solution treatment, followed by aging heat treatment.

At this time, the solution treatment is carried out according to a conventional cylinder head manufacturing method, for example, at 520 DEG C for 7 hours or more.

However, aging heat treatment is performed for 12 hours or more at a heat treatment temperature of 180 to 200 占 폚, and it is preferable to perform aging heat treatment at 190 占 폚 for 12 to 24 hours. It is preferable that the aging heat treatment temperature is lowered than that of the conventional cylinder head manufacturing method and the treatment time is increased to induce the overshoot. Therefore, when the Ti content is very low, the Al ₃ Ti crystallization phase which is not generated at the conventional aging heat treatment temperature, for example, 250 ° C., is generated to improve the tensile strength. However, if too much Al ₃ Ti crystallization phase is generated at this time, since the effect of improving the thermal conductivity is reduced, it is necessary to limit the Ti content to 0.02% or less while observing the heat treatment temperature and time. After the aging heat treatment, an aluminum alloy having a thermal conductivity of 200 W / mK or more at 200 ° C and a tensile strength of 290 MPa or more can be produced, which has both high thermal conductivity and strength.

[Example]

The following examples further illustrate the present invention. These embodiments are only for illustrating the present invention, and the present invention is not limited thereto.

Experiments were conducted to produce final products according to the production conditions of commercially produced cylinder heads. However, as shown in [Table 1], it was found that the molten steel produced by changing the content of each component, An aging heat treatment was performed. The solution treatment was carried out at 520 ° C for 7 hours, and the aging heat treatment was carried out at 190 ° C for 12 hours or more.

The cylinder headers produced under the above conditions were measured for thermal conductivity and tensile strength in an atmosphere of 200 ° C, and the results are shown in Table 1.

No. Si Cu Mg Fe Ni Ti Al ₃ Ti fraction (wt%) Thermal conductivity
(W / mK) The tensile strength
(MPa) Remarks One 2.5 3 0.25 0.3 0.3 0 0 200 260 Comparative Example 2 2.5 3 0.25 0.3 0.3 0.01 0.003 203 293 Example 3 2.5 3 0.25 0.3 0.3 0.02 0.03 207 298 Example 4 2.5 3 0.25 0.3 0.3 0.05 0.11 195 309 Comparative Example 5 3 4 0.4 0.4 One 0.01 0.004 201 304 Example 6 3 4 0.4 0.4 One 0.05 0.11 185 315 Comparative Example

As shown in Table 1, the composition of the aluminum alloy according to the present invention, i.e., Si: 1 to 3%, Cu: 2 to 4%, Mg: 0.4 to 0.4%, Fe: 0.2 to 0.4%, Ni: 0.1 to 1%, Ti: 0.02% or less (excluding 0%), the remainder Al and unavoidable impurities. mK, and the tensile strength is maintained at 290 MPa or more. In addition, the fractions of the Al ₃ Ti crystallized phases were produced as 0.003 wt%, 0.03 wt%, and 0.004 wt%, respectively, so that desired tensile strength and thermal conductivity could be secured. Therefore, it is preferable to control the fraction of the Al ₃ Ti crystallization phase to the level of 0.003 to 0.03 wt%.

On the other hand, in the comparative example group No. 1 alloy does not contain Ti and maintains the thermal conductivity at a satisfactory level, but the Al ₃ Ti crystallization phase is not produced and the tensile strength is remarkably low.

Further, in Comparative Example group No. 1, 4 and 6 alloys were found to have too much Ti content, resulting in too much Al ₃ Ti crystallization phase and reduced thermal conductivity.

FIG. 1 is a graph showing the types and amounts of reinforcing phases when an aluminum alloy according to an embodiment of the present invention is subjected to aging heat treatment at 190 ° C, FIG. 2 is a graph showing the types and amounts of reinforcing phases when an aluminum alloy according to an embodiment of the present invention is aged FIG. 3 is a graph showing the types and amounts of reinforcing phases when an aluminum alloy containing 0.05% of Ti is subjected to an age heat treatment at 190 ° C. FIG.

As shown in Fig. 1, the cylinder head subjected to the aluminum alloy composition and aging heat treatment according to the present invention shows a relatively high Al ₂ Cu strengthened phase, relatively low Si, and a small amount of generated Al ₃ Ti. The amount of the Al ₂ Cu reinforced phase is large, so that a high strength can be obtained, and an increase in thermal conductivity can be suppressed due to low Si content.

FIG. 2 shows an aluminum alloy having the alloy composition of the present invention subjected to an aging heat treatment at 250 ° C for 3 to 5 hours, showing a low Al ₂ Cu strengthened phase and relatively high Si, and no Al ₃ Ti crystallization was produced.

FIG. 3 shows that the amount of Al ₃ Ti crystallized product is higher than that of the present invention, in which the content of Ti is 0.05%, which is outside the scope of the present invention.

4 is a graph showing changes in thermal conductivity and tensile strength according to Ti content of an aluminum alloy according to embodiments of the present invention.

As shown in FIG. 4, when the content of Ti exceeded the range of the present invention, it was confirmed that although the tensile strength was increased, the thermal conductivity at a high temperature (200 ° C) was remarkably lowered. This is because, when the amount of Ti added is increased during the aging heat treatment at 190 ° C., the amount of the AlTi-based crystallization product is increased and the high-temperature thermal conductivity is decreased.

FIG. 5 is a graph showing changes in thermal conductivity according to the aging heat treatment temperature and the Ti content of the aluminum alloy according to the embodiments of the present invention. FIG. 6 is a graph showing the aging heat treatment temperature of the aluminum alloy according to the embodiments of the present invention Tensile strength according to Ti content. In FIGS. 5 and 6, the aging heat treatment at 190 ° C. is the result of maintaining 12 hours, and the aging heat treatment at 250 ° C. is the result of maintaining the 5 hours.

As shown in FIG. 5 and FIG. 6, it was confirmed that the aging heat treatment at 190 ° C increased both the high temperature thermal conductivity and the tensile strength as compared with the aging heat treatment at 250 ° C.

When the engine cylinder head is manufactured using the above-described aluminum alloy, high thermal conductivity and high strength at a high temperature can be obtained. For a detailed explanation, please refer to the description of aluminum alloy.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, You will understand.

It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. The scope of the present invention is defined by the appended claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be interpreted as being included in the scope of the present invention .

Claims (6)

An aluminum alloy for a cylinder head used in an engine of a vehicle,
The steel sheet according to any one of claims 1 to 3, wherein the steel sheet comprises 1 to 3% of Si, 2 to 4% of Cu, 0.1 to 0.4% of Mg, 0.2 to 0.4% of Fe, 0.1 to 1% of Ni, 0.02% The remainder Al and unavoidable impurities,
A thermal conductivity at 200 占 폚 of 200 W / mK or more, and a tensile strength of 290 MPa or more.
delete The method according to claim 1,
Wherein the aluminum alloy is formed of Al ₃ Ti in a reinforcing phase.
The method of claim 3,
The aluminum alloy is an aluminum alloy for the cylinder head, characterized in that the Al ₃ Ti phase is formed 0.003 ~ 0.03wt% total compared to an aluminum alloy reinforced.
A method of manufacturing a cylinder head for use in an engine of a vehicle,
The steel sheet according to any one of claims 1 to 3, wherein the steel sheet comprises 1 to 3% of Si, 2 to 4% of Cu, 0.1 to 0.4% of Mg, 0.2 to 0.4% of Fe, 0.1 to 1% of Ni, 0.02% And the remaining part Al and unavoidable impurities are cast to manufacture a cylinder head shaped article and the solution is heat treated at a heat treatment temperature of 180 to 200 DEG C for 12 hours or more so as to become overactive Of the cylinder head.
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