KR20040088857A - Composition of aluminum alloy for cylinder head with improved fatigue/intensity property - Google Patents

Abstract

PURPOSE: An aluminum alloy composition for cylinder head with improved strength and fatigue properties is provided in which aluminum is used as a matrix, and accurate composition ranges of Cu, Si, Mg, Mn, Ti and Sr and limit composition values for Fe, Zn, Ni, Sn, Cr and Pb are prescribed. CONSTITUTION: The aluminum alloy composition for cylinder head with improved strength and fatigue properties comprises aluminum as a matrix, 8.0 to 12.0 wt.% of silicon (Al), 0 to 0.5 wt.% of copper (Cu), 0.2 to 0.5 wt.% of magnesium (Mg), 0 to 0.2 wt.% of iron (Fe), 0.3 to 1.0 wt.% of manganese (Mn), 0 to 0.1 wt.% of zinc (Zn), 0 to 0.05 wt.% of nickel (Ni), 0 to 0.05 wt.% of tin (Sn), 0 to 0.05 wt.% of chromium (Cr), 0 to 0.05 wt.% of lead (Pb), 0.1 to 0.2 wt.% of titanium (Ti), and 0.008 to 0.03 wt.% of strontium (Sr).

Description

Composition of aluminum alloy for cylinder head with improved fatigue / intensity property

The present invention relates to an aluminum alloy composition for a cylinder head of an engine, and more particularly, based on aluminum, wherein the precise composition ranges of Si, Cu, Mg, Mn, Ti, Sr and Fe, Zn, Ni, Sn By defining the limit composition values for the Cr, Pb, and Pb components, the conventional aluminum alloy material that mainly regulates the Si and Mg components, and the main Si, Mg, Cu, Fe, Mn, Zn components, and Ni and Ti components are regulated. The present invention relates to an aluminum alloy composition for producing a cylinder head, in which strength and fatigue properties are remarkably improved as compared with conventional aluminum alloy materials having improved strength characteristics.

In general, the cylinder head for a vehicle engine has a tendency to gradually increase the physical properties required for the material used due to the high output and compact size of the engine.

However, aluminum alloys, which have recently been spotlighted as materials for cylinder heads, have lower strength, stiffness, and fatigue properties than conventional cast iron materials.

In order to increase the physical properties of the cylinder head, a conventionally developed aluminum alloy material includes a material (A) which mainly regulates two components, Si and Mg (Table 1).

However, the development of high-temperature, high-pressure, high-power engines is required to improve the strength and fatigue properties, and according to this trend, the main Si, Mg, and Cu, Fe, Mn, Zn, Ni, Ti components are regulated. Therefore, the material (B; JIS AC4CH) having improved physical properties compared to the existing material is used a lot (Table 1).

As described above, the conventional aluminum alloy material is an "A" material that mainly regulates the Si and Mg components, and the main Si, Cu, Mg, Fe, Mn, Zn components, and Ni and Ti components to improve the strength characteristics. B "material.

However, the above two conventional materials cause the following problems.

Specifically, in the case of the "A" material which mainly regulates only Si and Mg, it is impossible to precisely control the change in physical properties due to the addition of other components such as Fe, Mn, Zn, Ni, and Ti.

For example, in the case of Fe component, the brittleness of the material is increased when it is contained in a large amount of material, thereby rapidly decreasing the impact strength and the strength property.

In addition, the "B" material that defines the main Si, Cu, Mg, Fe, Mn, Zn components, and Ni and Ti components significantly improves the strength characteristics of the aluminum alloy material in which the two components of Si and Mg are regulated. .

However, in the case of the engine cylinder head, it is important to improve the strength and high temperature characteristics as the high temperature, high pressure, high output, and compactness are gradually increased, and the "B" material cannot satisfy the strength and fatigue properties currently required.

For this reason, the upper limit of the content of Fe, a brittle element, is so high that it is difficult to control the brittleness structure in the material due to the Fe component, so that the fatigue resistance is not excellent, and the Cu, Ti, and Mn component ranges are not regulated. , There is a disadvantage that the fatigue properties can be reduced by not adding the Mn component.

In the present invention, by defining the precise composition range of Cu, Si, Mg, Mn, Ti, Sr among the aluminum alloy components and the limit composition values for Fe, Zn, Ni, Sn, Cr, Pb components, the existing material "A" And an alloy composition (C) which significantly improves the strength and fatigue properties than the existing material "B" which has improved the strength properties through the regulation of the main components.

It is therefore an object of the present invention to provide a new aluminum alloy composition which can be used as the material in the manufacture of high temperature, high pressure, high power cylinder heads.

Specifically, the object of the present invention is based on aluminum, and here the exact composition range of Cu, Si, Mg, Mn, Ti, Sr and the limit composition values for Fe, Zn, Ni, Sn, Cr, Pb components It is to provide an aluminum alloy composition for a cylinder head with improved strength and fatigue properties.

The aluminum alloy composition for a cylinder head of the present invention for achieving the above object is based on aluminum, where copper (Cu) 0 to 0.5% by weight, silicon (Si) 8.0 to 12.0% by weight, magnesium (Mg) 0.2 0.5 wt%, iron (Fe) 0-0.2 wt%, manganese (Mn) 0.3-1.0 wt%, zinc (Zn) 0-0.1 wt%, nickel (Ni) 0-0.05 wt%, tin (Sn) 0 -0.05% by weight, chromium (Cr) 0-0.05% by weight, lead (Pb) 0-0.05% by weight, titanium (Ti) 0.1-0.2% by weight, strontium (Sr) 0.008-0.03% by weight It is done.

1 is a graph showing the tensile test results of the aluminum alloy material of the present invention and the conventional aluminum alloy material

Figure 2 is a graph showing the fatigue test results of the aluminum alloy material of the present invention and the conventional aluminum alloy material

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The present invention provides an aluminum alloy composition for a cylinder head of a vehicle engine, that is, an aluminum alloy composition having improved strength and fatigue characteristics used as a material for manufacturing a cylinder head of a high pressure, high output direct injection diesel and gasoline engine.

In the present invention, Cu, Si, Mg, Fe, Mn, Zn, Ni, Sn, Cr, Pb, Ti, and Sr components are shown in Table 2 in order to improve the strength and high temperature characteristics of the aluminum alloy material for the cylinder head. It is prescribed together.

Looking at the content range of each component constituting the aluminum alloy composition provided by the present invention.

(1) Cu: 0 to 0.5 wt%

When the content is excessive, the thermal conductivity is reduced, hot brittleness is generated during casting, and when a small amount is added, the high temperature strength is greatly improved, so it is 0 to 0.5% by weight.

(2) Si: 8.0-12.0 wt%

When the Si content is low, the strength and castability deteriorate, and when the content is high, the strength is increased but the elongation is decreased. In order to minimize the decrease in elongation and to improve the strength and reduce the density of the dendrite arm spacing (DAS), 8.0 ~ Let it be 12.0 weight%.

(3) Mg: 0.2 to 0.5 wt%

When the content is excessive, the thermal conductivity decreases and the oxide is formed in the casting, so the elongation decreases due to the influence of casting quality and heat treatment, and when the content is insufficient, the strength decreases, so it is 0.2 to 0.5% by weight to secure strength and elongation.

(4) Fe: 0 to 0.2 wt%

When the content is excessive, brittle compounds are produced, so the content is made 0.2 wt% or less.

(5) Mn: 0.3 to 1.0 wt%

When the content is added, the dispersoid is formed inside the tissue during solidification without additional heat treatment, and thus 0.3 to 1.0 wt% is considered.

(6) Zn: 0 to 0.1 wt%

When the content is added in an excessive amount, the thermal conductivity and the corrosion resistance are reduced, so that the content is 0.1% by weight or less.

(7) Ni: 0% to 0.05% by weight

It is added as an impurity, and when added in excess, the strength property of the material is lowered, so the content thereof is made 0.05 wt% or less.

(8) Sn: 0% to 0.05% by weight

It is added as an impurity, and when added in excess, the strength property of the material is lowered, so the content thereof is made 0.05 wt% or less.

(9) Cr: 0% to 0.05% by weight

It is added as an impurity, and when added in excess, the strength property of the material is lowered, so the content thereof is made 0.05 wt% or less.

(10) Pb: 0 to 0.05 wt%

It is added as an impurity, and when added in excess, the strength property of the material is lowered, so the content thereof is made 0.05 wt% or less.

(11) Ti: 0.1-0.2 wt%

If the content is excessive, brittleness may increase, so the maximum amount is 0.2% by weight or less, and when it is not added, the size of the metal structure becomes coarse, and thus the strength property is lowered, so the minimum is 0.1% or more.

(12) Sr: 0.008 to 0.03 wt%

If the content is excessive, brittleness may increase and the strength property may be lowered, so the maximum is 0.03% by weight or less, and when it is not added, the shape of the Si structure cannot be spheroidized, and thus the mechanical properties such as strength are reduced, so the minimum is 0.008% by weight or more.

The aluminum alloy composition of the above composition may be prepared by a conventional casting method in the art, but the present invention is not limited thereto.

As a result of the physical property evaluation using the specimen prepared from the aluminum alloy composition according to the present invention, it can be seen that the aluminum alloy composition of the present invention has significantly improved both strength and fatigue properties as compared with the conventional aluminum alloy composition.

Therefore, the aluminum alloy composition of the present invention can be suitably used for the cylinder head, and particularly when used as a material of the high pressure high power direct injection diesel and gasoline engine aluminum cylinder head can significantly improve the strength characteristics of the engine.

Hereinafter, the present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples.

Example

Using a conventional alloy production method, the alloy composition was prepared in the following content of the range of the composition according to the present invention shown in Table 2.

At this time, the content of Si 10.2%, Cu 0.1%, Mg 0.3%, Fe 0.15%, Mn 0.5%, Zn 0.02%, Ni 0.02%, Sn 0.01%, Cr 0.03%, Pb 0.04 weight%, Ti 0.15 weight%, Sr 0.015 weight%, Al 88.465 weight%.

In order to measure the physical properties (strength, elongation, fatigue, etc.) of the obtained alloy composition, the alloy composition was melted at 750 ° C. and then injected into a mold preheated to 100 ° C. to prepare a specimen having a predetermined standard.

Comparative example

Using a conventional alloy production method, the alloy composition was prepared in the following content of the composition range of the material "B" shown in Table 1.

At this time, the content of Si 6.9%, Cu 0.04%, Mg 0.35%, Fe 0.2%, Mn 0.02%, Zn 0.02%, Ni 0.03%, Ti 0.02%, Pb 0.02%, Sn 0.01 weight%, Cr 0.03 weight%, Al 92.36 weight%.

In order to measure the physical properties of the obtained alloy composition, the alloy composition was melted at 750 ° C. and then injected into a mold preheated to 100 ° C. to prepare specimens of the same standard as in Example.

Test Example 1

First, the strength and elongation at room temperature were measured using the specimens prepared in Examples and Comparative Examples, and then compared.

(1) tensile strength (MPa)

Tensile strength was measured using the test method specified in KS B0802, and the results are shown in Table 3 and FIG.

(2) yield strength (MPa)

Yield strength was measured using the test method specified in KS B0802, and the results are shown in Table 3 and FIG.

(3) Elongation (%)

Elongation was measured using a tensile tester, the results are shown in Table 3 and Figure 1 attached.

As shown in Table 3 and FIG. 1, when comparing the material of the present invention obtained according to the embodiment with the conventional material obtained according to the comparative example, the tensile strength and the yield strength were improved by about 14% at room temperature. The elongation hardly decreased compared with the increase in strength.

Test Example 2

On the other hand, using a specimen prepared in the above Examples and Comparative Examples was compared after performing a fatigue test at room temperature.

The fatigue test was carried out using a hydraulic fatigue tester, was carried out under the conditions of 10Hz, R = 0 in the stress range of 150 ~ 220MPa, the results are shown in Table 4 and FIG.

Figure 2 is a graph showing the fatigue test results of the aluminum alloy material and the conventional aluminum alloy material of the present invention, X-axis (cycle life) means the life until fracture under a given cyclic stress conditions, Y The axis (stress) represents the loading conditions applied to the specimen.

In general, under the above load conditions, if the stress applied is short, the service life is short, and if the stress is small, the fatigue life is long.

In addition, in FIG. 2, not broken is a fatigue that the test is stopped without breaking the specimen, which corresponds to the above fatigue, and generally 10000000 cycles are reported as fatigue.

As shown in Table 4 and FIG. 2, the fatigue life was greatly improved by 1000% (10 times) as a result of comparing the material of the present invention obtained according to the example with the conventional material obtained according to the comparative example.

From the above results, it can be seen that in the material of the present invention, the strength and fatigue characteristics, which are important for the cylinder head, are significantly improved. When the material of the present invention is used according to the above results, the materials of the present invention are subjected to high temperature, high pressure, and high power according to high engine power. It can be seen that it is possible to produce a cylinder head that can withstand it.

As described above, in the present invention, aluminum is used as the base, and the exact composition ranges of Cu, Si, Mg, Mn, Ti, and Sr, and the limit composition values for Fe, Zn, Ni, Sn, Cr, and Pb components By providing an aluminum alloy composition having a new composition, the strength and fatigue properties can be significantly improved compared to the existing aluminum alloy materials, thereby making it possible to manufacture a cylinder head capable of withstanding high temperature, high pressure, and high power. It works.

Claims (1)

Based on aluminum, there are 8.0 to 12.0 wt% of silicon (Si), 0 to 0.5 wt% of copper (Cu), 0.2 to 0.5 wt% of magnesium (Mg), 0 to 0.2 wt% of iron (Fe), and manganese ( Mn) 0.3-1.0 wt%, Zinc (Zn) 0-0.1 wt%, Nickel (Ni) 0-0.05 wt%, Tin (Sn) 0-0.05 wt%, Chromium (Cr) 0-0.05 wt%, Lead ( Pb) 0 to 0.05% by weight, titanium (Ti) 0.1 to 0.2% by weight, strontium (Sr) 0.008 to 0.03% by weight, the aluminum alloy composition for a cylinder head with improved strength and fatigue characteristics.