KR101950595B1 - Aluminium alloy and methods of fabricating the same - Google Patents

Abstract

The present invention relates to an aluminum alloy applicable to an aluminum plate for a vehicle and a manufacturing method thereof. According to one embodiment of the present invention, the manufacturing method of the aluminum alloy comprises: (a) a step of providing a strip casting process with a casting material including 0.16 to 0.24 wt% of Cr, 0.5 to 0.95 wt% of Cu, 0.1 to 0.2 wt% of Mn, 0.2 to 1.0 wt% of Mg, 0.25 to 0.45 wt% of Zn, 0.7 to 0.85 wt% of Si, 0.25 to 0.3 wt% of Ti, and the balance of Al and inevitable impurities; (b) a step of hot-rolling the casting material at 480 to 540°C by a reduction rate of 20 to 40% without a homogenization process; (c) a step of cold-rolling the hot-rolled casting material by a reduction rate of 20 to 40%; and (d) a step of performing recrystallization heat treatment for the cold-rolled casting material at 480 to 540°C for 20 to 60 min.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy,

The present invention relates to an aluminum alloy and a manufacturing method thereof, and more particularly, to an aluminum alloy having high strength and solidity formation and a method of manufacturing the same.

BACKGROUND ART [0002] In recent years, the social demands for lightening the weight of automobiles have been increasing. In order to respond to such demands, attempts have been made to apply aluminum alloy materials instead of steel materials such as steel plates partially in automobile body panels or reinforcing materials such as door beams. Further, in order to make the automobile body lighter, it is required to expand the application of aluminum alloy materials to automobile structural members such as frames and pillars, which contribute to weight reduction, among automobile members.

Related Prior Art Korean Patent Publication No. 2010-0049722 (published on May 13, 2010, entitled "High Strength Aluminum Alloy Casting") is available.

An object of the present invention is to provide an aluminum alloy which can be applied to an automotive aluminum plate which is required to form a solid having uniform mechanical characteristics, and a method for producing the same.

In order to accomplish the above object, the present invention provides a method of manufacturing an aluminum alloy, comprising the steps of: (a) providing 0.16 to 0.24 wt% of Cr, 0.5 to 0.95 wt% of Cu, 0.1 to 0.2 wt% of Mn, 0.2 to 1.0% by weight of Mg, 0.25 to 0.45% by weight of Zn, 0.7 to 0.85% by weight of Si and 0.25 to 0.3% by weight of Ti and the balance of Al and inevitable impurities step; (b) hot-rolling the cast material at 480 to 540 占 폚 at a reduction ratio of 20 to 40% without homogenizing heat treatment; (c) cold rolling the hot-rolled cast material at a reduction ratio of 20 to 40%; And (d) subjecting the cold-rolled cast material to recrystallization heat treatment at 480 to 540 占 폚 for 20 to 60 minutes.

In the step (a) of the method for producing an aluminum alloy, a Mg ₂ Si-enhanced phase to which Mn, Cr or Cu is bound is dendritically formed. In the step (b) and the step (c), the Mg ₂ Si- And the step (d) may include a step of recrystallization at the periphery of the Mg ₂ Si strengthened phase to produce an anisotropic texture, thereby further improving the moldability.

The Mg ₂ Si-enriched phase formed in the step (a) of the aluminum alloy production method has a size of 20 μm or less, and the Mg ₂ Si-enriched phase in the step (b) and the step (c) Size.

The step (a) of the aluminum alloy manufacturing method includes a step of forming a casting material having a thickness of 3 to 6 mm by cooling the alloyed melt at 700 ° C or higher to 300 ° C at a cooling rate of 100 to 150 ° C / s can do.

According to an embodiment of the present invention, there is provided an aluminum alloy including 0.16 to 0.24 wt% of Cr, 0.5 to 0.95 wt% of Cu, 0.1 to 0.2 wt% of Mn, 0.2 to 1.0 wt% of Mg, Zn : 0.25 to 0.45 wt%, Si: 0.7 to 0.85 wt%, and Ti: 0.25 to 0.3 wt%, the balance being Al and inevitable impurities.

In the above aluminum alloy, Mn, Cr or Mg ₂ Si strengthen the Cu is bonded phase having a size of less than 5 ㎛, the recrystallization to the Mg ₂ Si strengthening the periphery proceeds may be characterized in that the anisotropic texture produced .

According to the embodiment of the present invention, an aluminum alloy which can be applied to an automotive aluminum plate which requires uniform formation of mechanical properties, and a method of manufacturing the same can be realized. Of course, the scope of the present invention is not limited by these effects.

1 is a flow chart illustrating a method of manufacturing an aluminum alloy according to an embodiment of the present invention.
FIG. 2 is a graph illustrating the solidification conditions of castings in an aluminum alloy production method according to Examples and Comparative Examples of the present invention.
3 is a photograph of a microstructure of an aluminum alloy according to an embodiment of the present invention.
4 is a photograph of the microstructure of the aluminum alloy according to the comparative example of the present invention.
FIG. 5 is photographs taken to illustrate the strength enhancement by the strengthened phase of the aluminum alloy according to the embodiment of the present invention.
6 is photographs taken to explain the texture control by the strengthened phase of the aluminum alloy according to the embodiment of the present invention.
FIGS. 7 to 10 are graphs illustrating the tensile properties of an aluminum alloy according to an experimental example of the present invention.

Hereinafter, an aluminum alloy according to an embodiment of the present invention and a method of manufacturing the aluminum alloy will be described in detail. The terms used below are appropriately selected terms in consideration of functions in the present invention, and definitions of these terms should be made based on the contents throughout this specification.

When an aluminum plate material is manufactured using a cast material, mechanical properties due to uneven microstructure formation are reduced. On the other hand, it is possible to reduce costs by simplifying the rolling process when manufacturing the plate through the strip casting process, which is a low cost casting process, but it is difficult to control the fine structure between the surface portion and the center portion due to the simplification of the rolling process. The cost reduction effect due to the homogenization heat treatment and the post-treatment process of the natural casting material for the microstructure control becomes insufficient. Therefore, the strip casting process, a cost-saving process, is limited in its use due to uneven microstructure. That is, a strip casting method that is simpler than a direct chill casting method, which is a general plate material manufacturing process, is advantageous in a raw material, but in terms of achieving physical properties, rapid solidification control is difficult.

The present invention provides a method of manufacturing an aluminum alloy which can realize an aluminum alloy by a strip casting process which can reduce costs while considering the need for uniform mechanical properties in an automotive aluminum plate requiring high performance.

1 is a flow chart illustrating a method of manufacturing an aluminum alloy according to an embodiment of the present invention.

1, a method of manufacturing an aluminum alloy according to an embodiment of the present invention includes: (a) 0.16 to 0.24 wt% of Cr, 0.5 to 0.95 wt% of Cu, 0.1 to 0.2 wt% of Mn, 0.2 to 1.0% by weight of Mg, 0.25 to 0.45% by weight of Zn, 0.7 to 0.85% by weight of Si and 0.25 to 0.3% by weight of Ti and the balance of Al and inevitable impurities Step SlOO; (b) hot rolling the cast material at 480 to 540 占 폚 at a reduction ratio of 20 to 40% without homogenizing heat treatment (S200); (c) cold-rolling the hot-rolled cast material at a reduction ratio of 20 to 40% (S300); And (d) performing a recrystallization heat treatment (S400) on the cold-rolled cast material at 480 to 540 占 폚 for 20 to 60 minutes.

In the step (a) of the method for producing an aluminum alloy, a Mg ₂ Si-enhanced phase to which Mn, Cr or Cu is bound is dendritically formed. In the step (b) and the step (c), the Mg ₂ Si- And the step (d) may include a step of recrystallization at the periphery of the Mg ₂ Si strengthened phase to produce an anisotropic texture, thereby further improving the moldability.

The Mg ₂ Si-enriched phase formed in the step (a) of the aluminum alloy production method has a size of 20 μm or less, and the Mg ₂ Si-enriched phase in the step (b) and the step (c) Size.

The step (a) of the aluminum alloy manufacturing method includes a step of forming a casting material having a thickness of 3 to 6 mm by cooling the alloyed melt at 700 ° C or higher to 300 ° C at a cooling rate of 100 to 150 ° C / s can do.

The composition range of the cast material disclosed in the step (a) will be described.

Cr: 0.16 to 0.24 wt%

Cr is an element for refining the crystal grains. If the Cr content is less than 0.16% by weight, the effect of grain refinement is insignificant. If the Cr content exceeds 0.24% by weight, a coarse compound may be produced and the workability may be deteriorated. Therefore, the Cr content is limited to 0.16-0.44% Respectively.

Cu: 0.5 to 0.95 wt%

Copper (Cu) improves the mechanical properties of the aluminum alloy and increases the toughness by hardening most of the solid solution. However, when the content is less than 0.5 wt%, the effect of improving tensile strength is not significant. When the content exceeds 0.95 wt%, the formability decreases due to the precipitation of an intermetallic compound. Therefore, 0.5 to 0.95 wt%.

Mn: 0.1 to 0.2 wt%

Manganese (Mn) is an element that improves strength by solid solution strengthening. If the content of manganese (Mn) is less than 0.1% by weight, the effect of suppressing grain growth may be insufficient and the strength of the aluminum alloy may be lowered. On the other hand, when the content is more than 0.2% by weight, The extrudability can be lowered.

Mg: 0.2 to 1.0 wt%

Magnesium (Mg) is an element that improves the strength by forming silicon (Si) and Mg2Si compounds. When the content is less than 0.2% by weight, the effect of improving the strength is not significant. However, when the content exceeds 1.0% by weight, the extrudability, surface roughness, dimensional accuracy, etc. of the aluminum alloy may be greatly deteriorated. The oxidation tendency increases. Therefore, the content of magnesium (Mg) is limited within the range of 0.2 to 1.0 wt%.

Zn: 0.25 to 0.45 wt%

Zn is an element that precipitates the? 'Phase and / or the T' phase by coexisting with Mg in the aluminum alloy. By containing Zn together with Mg, an effect of improving the strength by precipitation strengthening can be obtained. When the content of Zn is less than 0.25% by weight, the precipitation amount of the? 'Phase and the T' phase is decreased, so that the effect of improving the strength is lowered. Therefore, the content of Zn should be 0.25 wt% or more. On the other hand, when the content of Zn is more than 0.45% by weight, when the content is 5.0% or more, the ductility may be lowered. Therefore, the content of Zn is set to 0.25 to 0.45% by weight.

Si: 0.7 to 0.85 wt%

Silicon (Si) is a major element affecting casting and strength. However, when the content is less than 0.7 wt%, the effect of casting and strength improvement is not significant. On the other hand, when the content exceeds 0.85% by weight, surface defects may occur at the same extrusion rate during the extrusion processing of the aluminum alloy.

Ti: 0.25 to 0.3 wt%

Titanium (Ti) is an element which improves casting and is added to an aluminum alloy, thereby contributing to the improvement of strength by refining the ingot texture. When the content of titanium (Ti) is less than 0.25%, cracking of the coarse alloy may occur in the cast structure at the time of melt casting. When the content of titanium (Ti) exceeds 0.3 wt%, the AlTi alloy A compound or the like is likely to cause point and streak patterns, which may result in insufficient appearance characteristics. Therefore, the content of Ti is set to 0.25 to 0.3% by weight.

FIG. 2 is a graph illustrating the solidification conditions of castings in an aluminum alloy manufacturing method according to Examples and Comparative Examples of the present invention.

2, in the method of manufacturing an aluminum alloy according to an embodiment of the present invention, the solidification condition (1) of the casting material is such that the molten alloy at 720 deg. C is cooled to 300 deg. C at a cooling rate of 114 deg. And the thickness of the formed cast material is 6 mm. Further, it was confirmed that the thickness of the cast material formed under the condition of controlled cooling of the molten alloy at 720 ° C. to 300 ° C. at a cooling rate of 100 to 150 ° C./s was 3 to 6 mm.

On the contrary, in the process for producing an aluminum alloy according to the comparative example of the present invention, the coagulation condition (2) of the casting material is a condition for controlling and cooling the molten alloy at 720 ° C. at a cooling rate of 40 ° C./s to 300 ° C., The thickness of the ash is 20 mm.

FIG. 3 is a photograph of a microstructure of an aluminum alloy according to an embodiment of the present invention, and FIG. 4 is a photograph of a microstructure of an aluminum alloy according to a comparative example of the present invention.

The aluminum alloy according to the comparative example of the present invention contains 0.3 wt% or less of Cr (more than 0 wt%), 0.3 wt% or less of Cu (but more than 0 wt%), 0.3 wt% (More than 0 wt%), Si: 0.2 to 1.0 wt%, Ti: less than 0.2 wt% (however, more than 0 wt%), Mg: 0.2 to 1.0 wt% And the balance consisting of Al and inevitable impurities and having a thickness of 15 mm; (b) homogenizing the cast material at 530 ° C for 4 hours; (c) hot rolling the cast material at a reduction rate of 20 to 40% at 480 to 540 占 폚; (d) cold-rolling the hot-rolled cast material at a reduction ratio of 20 to 40%; And (d) performing a recrystallization heat treatment on the cold-rolled cast material at 480 to 540 ° C for 20 to 60 minutes.

In the microstructure of the aluminum alloy according to the examples and comparative examples of the present invention, the recrystallization sizes were 30 탆 and 43 탆, respectively, and the recrystallization ratios were 85% and 62%, respectively.

FIG. 5 is a photograph taken to explain the strength enhancement by the strengthened phase of the aluminum alloy according to the embodiment of the present invention, and FIG. 6 is a view illustrating the texture control by the strengthened phase of the aluminum alloy according to the embodiment of the present invention These are the photographs taken for the purpose.

Referring to FIG. 5, the casting material of the article has a thickness of 6 mm and the thickness of the final plate is 1 mm. In the cast material of the present invention, a new crystallized phase of less than 20 μm is produced through the alloy design. The new crystallization phase is Mg ₂ Si combined with Mn, Cr or Cu. It is transformed into a spherical crystallization phase through hot rolling, cold rolling and recrystallization heat treatment, and is controlled to a size of 5 μm or less to improve the strength of the aluminum alloy. This enhancement of strength is achieved through disruption of dislocation progression by dispersed phases during plastic deformation.

Referring to FIG. 6, the stress concentrated around the crystallization phase in the cold rolling process is subjected to a recrystallization heat treatment process, thereby improving the formability due to the random recrystallization development in the periphery of the crystallization phase.

Hereinafter, preferred examples of the present invention will be described in order to facilitate understanding of the present invention. It should be understood, however, that the following examples are intended to aid in the understanding of the present invention and are not intended to limit the scope of the present invention.

Experimental Example

Some of the experimental examples form an aluminum alloy having the component system of Table 1 as an embodiment of the present invention. For example, the aluminum alloy according to Example 1 contains 0.184 wt% of Cr, 0.524 wt% of Cu, 0.119 wt% of Mn, 0.654 wt% of Mg, 0.372 wt% of Zn, 0.836 wt% of Si, 0.29% by weight, and the balance of Al and inevitable impurities. The aluminum alloy according to Example 2 is composed of 0.167 wt% of Cr, 0.502 wt% of Cu, 0.197 wt% of Mn, 0.230 wt% of Mg, 0.269 wt% of Zn, 0.735 wt% of Si, 0.258 wt% of Ti, And the balance of Al and inevitable impurities. The aluminum alloy according to Example 3 contains 0.235 wt% of Cr, 0.949 wt% of Cu, 0.102 wt% of Mn, 0.952 wt% of Mg, 0.440 wt% of Zn, 0.759 wt% of Si, 0.266 wt% of Ti, And the balance of Al and inevitable impurities.

Cr Cu Mn Mg Zn Si Ti Example 1 0.184 0.524 0.119 0.654 0.372 0.836 0.29 Example 2 0.167 0.502 0.197 0.23 0.269 0.735 0.258 Example 3 0.235 0.949 0.102 0.952 0.44 0.759 0.266

The alloyed molten alloy having the compositions of Examples 1 to 3 was controlled and cooled at a cooling rate of 120 DEG C / s from 720 DEG C to 300 DEG C to form a casting material having a thickness of 6 mm. Then, the casting material was rolled at 520 DEG C without homogenizing heat treatment Rolled at a rate of 30%, cold-rolled at a reduction ratio of 30%, and subjected to recrystallization heat treatment at 520 DEG C for 20 minutes, respectively. The tensile properties of the specimens are shown in FIGS.

7 and Table 2, the aluminum alloy according to Example 1 has a property value of a yield strength of 107 MPa, a tensile strength of 243 MPa, and an elongation of 29.2%. Referring to FIGS. 8 and 2, The aluminum alloy according to Example 3 had a yield strength of 73 MPa, a tensile strength of 195 MPa, and an elongation of 27.2%. Referring to FIG. 9 and Table 2, the aluminum alloy according to Example 3 had a yield strength of 127 MPa, A strength of 275 MPa, and an elongation of 30.4%.

Example 1 Example 2 Example 3 Y.S. (MPa) 107 73 127 T.S. (MPa) 243 195 275 E (%) 29.2 27.2 30.4

Fig. 10 is a graph showing the results of a comparative example of experimental examples in which 0.3% of Cr, 0.3% of Cu, 0.3% of Mn, 0.23% of Mg, 0.26% of Zn, 0.73% of Si and 0.15% (530 占 폚 for 4 hours), hot rolling (530 占 폚, 30% reduction), cold rolling (30% reduction), and a 500 mm thick slab composed of Al and inevitable impurities, And annealing (530 占 폚, 20 minutes) were successively carried out to evaluate the tensile properties of the aluminum alloy. The evaluation results of the tensile properties of the aluminum alloy according to the comparative example are summarized in Table 3. In Table 3, RD, TD, and 45 ° represent specific orientations relative to the rolling direction in the rolling process.

RD TD 45 ° Yield strength (MPa) 125 125 125 The tensile strength
(MPa) 248 242 239 Elongation
(%) 26.5 27 28.3

Comparing the results of the embodiments of the present invention shown in Table 2 with those of the comparative example of the present invention shown in Table 3, the material properties of the aluminum alloy realized by the manufacturing method according to the embodiment of the present invention were compared with those of the conventional manufacturing method ) Is equivalent to the material properties of the alloy implemented with the alloy. However, according to the embodiment of the present invention, it is possible to apply strip casting, which is a low-cost casting process, and it is possible to omit the homogenization heat treatment that is required when a thick-walled product is applied.

It is to be understood that the invention includes various modifications and equivalent embodiments that can be derived from the disclosed embodiments as well as those of ordinary skill in the art to which the present invention pertains. Accordingly, the technical scope of the present invention should be defined by the following claims.

Claims (6)

(a) 0.16 to 0.24 wt% of Cr, 0.5 to 0.95 wt% of Cu, 0.1 to 0.2 wt% of Mn, 0.2 to 1.0 wt% of Mg, 0.25 to 0.45 wt% of Zn and 0.7 to 0.7 wt% of Si in a strip casting process To 0.85% by weight, Ti: 0.25 to 0.3% by weight, the balance being Al and inevitable impurities;
(b) hot-rolling the cast material at 480 to 540 占 폚 at a reduction ratio of 20 to 40% without homogenizing heat treatment;
(c) cold rolling the hot-rolled cast material at a reduction ratio of 20 to 40%; And
(d) subjecting the cold-rolled cast material to recrystallization heat treatment at 480 to 540 占 폚 for 20 to 60 minutes;
≪ / RTI > The method according to claim 1,
In the step (a), the Mg ₂ Si-strengthened phase to which Mn, Cr or Cu is bound is crystallized in the form of dendrites. In the step (b) and the step (c), the Mg ₂ Si- wherein the step (d) includes recrystallization of the Mg ₂ Si-strengthened phase peripheral portion to produce an anisotropic aggregate structure, thereby further improving the moldability. 3. The method of claim 2,
The Mg ₂ Si-enriched phase formed in the step (a) has a size of 20 탆 or less, and the Mg ₂ Si-enriched phase in the steps (b) and (c) has a size of 5 탆 or less , A method for producing an aluminum alloy. The method according to claim 1,
Wherein the step (a) comprises cooling a molten alloy having a temperature of 700 ° C or higher to 300 ° C at a cooling rate of 100 to 150 ° C / s to form a cast material having a thickness of 3 to 6 mm . 0.1 to 0.2 wt% of Cr, 0.1 to 0.24 wt% of Cr, 0.5 to 0.95 wt% of Cu, 0.1 to 0.2 wt% of Mn, 0.2 to 1.0 wt% of Mg, 0.25 to 0.45 wt% of Zn, 0.7 to 0.85 wt% 0.25 to 0.3% by weight, the balance being Al and inevitable impurities
The Mg ₂ Si-strengthened phase to which Mn, Cr or Cu is bonded has a size of 5 탆 or less and recrystallization proceeds in the periphery of the Mg ₂ Si strengthened phase to form an anisotropic aggregate structure
Aluminum alloy. delete

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