KR100668644B1 - Preparation method of AlSiMg cast alloys with improved tensile strength properties and elongation - Google Patents

Abstract

The present invention relates to an AlSiMg alloy with improved tensile strength and elongation, and more particularly, to an AlSiMg alloy containing Fe as an impurity in order to improve tensile strength and elongation.

The present invention is to improve the tensile strength and elongation by improving the chemical composition of the alloy so that the impurity Fe, which is incorporated in AlSiMg, which is mainly used as an automotive aluminum wheel alloy, to lower the tensile property of the alloy, is changed into a factor that improves the tensile property and elongation. To provide an aluminum alloy that can be made.

In the present invention, AlSiMg alloy containing Fe as an impurity,

In order to improve tensile strength and elongation, the AlSiMg alloy containing 0.01-0.20 weight% of chromium (Cr) and 0.02-0.40 weight% of manganese (Mn) is shown.

In the present invention, the AlSiMg alloy without addition of chromium, manganese, and Fe as an impurity represents an AlSiMg alloy based on Al and containing 6.5 to 7.5 wt% Si and 0.25 to 0.45 wt% Mg.

Description

Preparation method of AlSiMg cast alloys with improved tensile strength properties and elongation

1 is a photograph showing the microstructure after heat treatment of a high-purity A356.2 alloy having an impurity Fe of 0.06 wt% or less and an A356 alloy having 0.20 wt% Fe impurities.

Fig. 2 shows the change of the α-Al (FeMn) Si solidification structure (2a to 2c) and the α-Al (FeMn) Si precipitated in the aluminum matrix according to the amount of Mn added to the A356 alloy having 0.20% by weight of Fe impurities. It is a photograph showing the shape 2d.

Fig. 3 shows the change of α-Al (FeCr) Si solidification structure (3a to 3c) according to the amount of Cr added to A356 alloy having 0.20% by weight Fe impurities and α-Al (FeCr) Si precipitated in the aluminum matrix. It is a photograph showing the shape 3d.

Fig. 4 shows the precipitation of α-Al (FeMnCr) Si-based solidified structure in shape 4a and aluminum matrix when 0.13% by weight Cr and 0.13% by weight Mn are added to an A356 alloy having 0.20% by weight Fe impurities. The photograph shows cross slips 4b and 4c of dislocations generated around α-Al (FeMnCr) Si particles.

FIG. 5 is a DSC curve showing precipitation temperatures of α-Al (FeMn) Si and α-Al (FeMnCr) Si in which Mn is added alone or Mn and Cr are precipitated in a composite additive alloy.

<Description of the symbols for the main parts of the drawings>

 1: Si particle 2: Primary aluminum

3: needle-like β-Al ₅ FeSi 4: coarsely improved α-Al (FeMn) Si

 5: α-Al (FeMn) Si precipitated particles 6: Goodly improved α-Al (FeCr) Si

 7: α-Al (FeCr) Si precipitated particles 8: very well improved α-Al (FeMnCr) Si

 9: α-Al (FeMnCr) Si precipitated particles 10: dislocation

 The present invention relates to a method for producing an AlSiMg alloy with improved tensile strength and elongation. More specifically, in an AlSiMg alloy containing Fe as an impurity, an AlSiMg alloy containing chromium and manganese to improve tensile strength and elongation is described. It relates to a manufacturing method.

The technique for controlling Fe in the aluminum main alloy is mainly AC8A alloy (JIS standard), that is, Al- (11.0-13.0)% by weight Si- (0.8-1.3)% by weight Cu- (0.7-1.3)% by weight Mg- ( max0.8) wt% Fe- (max0.15) wt% Mn- (0.8 to 1.5) wt% Ni alloys have been used.

In the aluminum main alloy, coarse needle-like β-Al ₅ FeSi is crystallized in the solidification process as the Fe content increases, and when the alloy is subjected to tensile stress, β-Al ₅ FeSi is preferentially destroyed so that the tensile strength and elongation rapidly decrease. Will decrease. In order to improve this problem, when the Mn content is added within 50% of the Fe content, various shapes of α-Al (FeMn) Si having less brittleness than the acicular β-Al ₅ FeSi are crystallized in the solidification process. In this way, the adverse effects on the tensile properties of the impurity Fe have been improved. However, these α-Al (FeMn) Si particles still reduce the tensile strength and elongation.

On the other hand, AlSiMg alloys in which the Fe content is controlled in a small amount are A356 alloys, Al- (6.5 to 7.5) wt% Si- (0.35 to 0.45) wt% Mg, or A357 alloys having a somewhat high Mg and Fe content.

The Fe content in the AlSiMg alloy is increased in the process of mixing Fe with the Fe-containing tool and contact friction, or adding a small amount of regenerated AlSiMg alloy to reduce the cost, before the AlSiMg alloy is dissolved. do.

Such impurity Fe is hardly dissolved in the aluminum base and crystallized to needle-like β-Al ₅ FeSi during solidification, and when the AlSiMg alloy is deformed, the needle-like β-Al ₅ FeSi portion is first destroyed, thereby rapidly increasing tensile strength and elongation. Decrease.

As a method of controlling Fe, the method of controlling the content of impurity Fe within 0.10 weight% is commercially available. Therefore, the high production cost of the product occurs in the process of maintaining a high purity of the A356 alloy. In addition, the Fe of the regenerated AlSiMg alloy increases to 0.30% by weight. The regenerated alloy cannot be directly dissolved and used, but is added in small amounts to the virgin alloy and finally Fe is used at 0.10% by weight or less.

Alternatively, to prevent the impurity Fe to produce a β-Al ₅ FeSi of the bed is, there is a method using Mn, Cr, Mo and Ni, etc., respectively to improve the β-Al ₅ FeSi of needle-like particle shape, Mn and Cr are mainly used. However, when Mn or Cr is added, α-Al (FeMn) Si or α-Al (FeCr) Si is formed during solidification instead of acicular β-Al ₅ FeSi, and the microstructure is improved to some extent and the tensile property is rapidly decreased. Although it can be prevented, α-Al (FeMn) Si or α-Al (FeCr) Si still act as a factor that inhibits tensile properties because it is coarse or acicular than Si particles in comparison with the microstructure of high purity A356 alloy. .

Meanwhile, a method of adding Be to 20 to 40% of Fe is already described in Korean Patent Registration No. 10-0226283. However, Be is not only limited to its use due to high toxicity, but also adversely affects the health of workers when manufacturing alloys. Also, Be has a disadvantage of improving the production cost of castings because it is a very expensive element.

The present invention is to improve the tensile strength and elongation by improving the chemical composition of the alloy so that the impurity Fe, which is incorporated in AlSiMg, which is mainly used as an automotive aluminum wheel alloy, to lower the tensile property of the alloy, is changed into a factor that improves the tensile property and elongation. An object of the present invention is to provide a method for producing an aluminum alloy.

The aluminum alloy according to the present invention is an inexpensive and low purity AlSiMg alloy can be provided as aluminum wheels for automobiles, aluminum casting parts for transportation equipment, and other component alloys.

In order to achieve the above-mentioned object, the present invention adds 0.01-0.20% by weight of chromium and 0.02-0.40% by weight of manganese to an AlSiMg alloy composition containing Fe as an impurity to precipitate α-Al (FeMnCr) Si in the alloy composition. It provides a method for producing an AlSiMg main alloy to form a.

In the present invention, the AlSiMg alloy before Fe, chromium and manganese are added as impurities in the present invention is AlSiMg (Al-6.5 to 7.5 wt% Si- based on Al and containing 6.5 to 7.5 wt% Si and 0.25 to 0.45 wt% Si. 0.25-0.45 weight% Mg) alloy.

Since various contents of chromium and manganese are applied in the AlSiMg alloy containing impurity Fe of the present invention, in order to improve tensile properties and elongation in AlSiMg alloy containing impurity Fe, it is preferable to use chromium and manganese in the above numerical range. good.

In the AlSiMg alloy of the present invention, the range of impurity Fe capable of controlling the Fe-based intermetallic compound by the weight% of chromium and manganese and improving tensile properties and elongation at the same time is 0.03 to 0.30% by weight.

The present invention of a conventional needle to AlSiMg alloy by the addition of chromium and manganese on AlSiMg alloy of Fe are contained as impurities _{β-Al 5 FeSi, α-} Al (FeMn) Si particles and an α-Al (FeCr) α instead of Si particles Tensile properties and elongation can be improved by forming -Al (FeMnCr) Si particles.

The AlSiMg alloy of the present invention precipitates α-Al (FeMnCr) Si, which is a unique phase on an aluminum matrix through a post-heat treatment process, and is a dislocation that is a kind of defect caused by deformation of the material around the α-Al (FeMnCr) Si particles. It is possible to obtain an AlSiMg alloy with improved tensile properties and elongation by causing the cross-slip to move along another crystal plane without piling up in one place.

By adding chromium and manganese to the AlSiMg alloy containing Fe as an impurity as described above, the low-purity and low-cost AlSiMg alloy was able to increase the tensile strength and elongation than the expensive high-purity commercial AlSiMg.

In the present invention, the melting temperature of the alloy is 750 to 770 ° C, the injection temperature is 745 to 750 ° C, the solution treatment is 535 ± 1 ° C / 10hs, and the aging treatment may be 160 ± 1 ° C / 6hs. To keep the cooling rate constant, the mold temperature can be maintained at 280 ± 1 ° C.

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

At this time, A356 alloy containing 0.20% by weight Fe was used as the AlSiMg main alloy, and Mn and Cr were used as the elements capable of controlling acicular β-Al ₅ FeSi.

As shown in Fig. 1, the solidified microstructure of the A356 alloy in which the impurity Fe is controlled to 0.07% by weight or less is composed of Si particles 1 and primary aluminum 2 (Fig. 1A). However, when 0.20% by weight Fe is incorporated into the A356 alloy as an impurity, coarse needle-like β-Al ₅ FeSi (3) is segregated and formed in the solidification process (FIG. 1B). Fe is very low in solubility in aluminum base, so it remains in the residual liquid phase and segregates in the final solidification process area.

As shown in Fig. 2, 0.13% by weight of Mn (0.22%), 0.20% by weight (Fig. 2B) and 0.40% by weight (Fig. 2C) were added to the A356 alloy containing 0.20% by weight Fe. The needle-like β-Al ₅ FeSi is controlled to produce α-Al (FeMn) Si (4) having a size of 5 to 20 µm and slightly different shapes depending on the amount of Mn.

These α-Al (FeMn) Si particles have been improved compared to β-Al ₅ FeSi up to 0.13% by weight Mn but still have short needles, and ribs and coarse needles at 0.20% by weight Mn and 0.40% by weight Mn added. These phases still have a difference in degree, and they break before the Si particles in the tensile stress state, which acts as a factor to lower the elongation.

However, when Mn is added, fine α-Al (FeMn) Si (5) having a size of about 200 nm is deposited on the primary aluminum matrix as shown in FIG. 2D. Originally, the main precipitated phase of the A356 alloy has an additional particle-shaped α-Al (FeMn) Si precipitated phase due to the addition of Mg ₂ Si or Mn.

As shown in Fig. 3, when 0.07% by weight (Fig. 3A), 0.13% by weight (Fig. 3B) and 0.20% by weight (Fig. 3C) of Cr are added to the same alloy, coarse needle-like β-Al ₅ FeSi is controlled. A short rod-like α-Al (FeCr) Si (3 to 15 µm) 6 is produced.

α-Al (FeCr) Si particles are finer than α-Al (FeMn) Si and are distributed relatively uniformly on the aluminum matrix. However, as shown in Fig. 3D, coarse rod-like α-Al (FeCr) Si (7) precipitates at a very low density on the aluminum matrix.

2 and 3 above, Mn has the advantage of generating a fine grain-like precipitated phase than the coarse needle-like control effect of coarse needle β-Al ₅ FeSi, on the contrary, Cr is β-Al ₅ FeSi Is very effective to control, but the disadvantage is that the deposited phase is very coarse, about 1㎛.

In the present invention, in order to utilize only the positive effects on the structure of Mn and Cr, 0.01 to 0.20% by weight Cr and 0.02 to 0.40% by weight Mn can be added to the A356 alloy containing 0.20% by weight Fe. For example, adding 0.13 wt% Cr and 0.13 wt% Mn to the A356 alloy completely improves not only coarse acicular β-Al ₅ FeSi but also short acicular α-Al (FeMn) Si as shown in FIG. 4A. As a result, α-Al (FeMnCr) Si (8), which is much finer than Si particles, was produced to 1 µm or less.

4B and 4C, the α-Al (FeMnCr) Si particles 9 deposited in aluminum are also about 100 nm in size, 1/2 of the conventional α-Al (FeMn) Si precipitated particles (FIG. 2D). Compared to the α-Al (FeCr) Si precipitated particles (FIG. 3D), it is about 1/10 finer. In addition, as the cross-slip of dislocation 10 occurs in the strained state around α-Al (FeMnCr) Si precipitated particles, uniform strain occurs to high elongation, which serves as another important factor to increase elongation and tensile strength. do.

The reason why the α-Al (FeMnCr) Si precipitated particles are refined when the Cr and Mn are added to the composite is that precipitation of α-Al (FeMnCr) Si that precipitates after the complex addition of Cr and Mn is shown in FIGS. 5A and 5B. This is because the temperature is about 15 ° C. higher than the precipitation temperature of α-Al (FeMn) Si which precipitates after Mn is added alone. That is, when the alloy is solvated at 530 to 535 ° C., α-Al (FeMnCr) Si precipitated at a temperature 15 ° C. higher than α-Al (FeMn) Si is less likely to grow, resulting in finer particles. do.

Meanwhile, in FIG. 5A, α-Al (FeMn) Si precipitates at a lower temperature in an after cast alloy in an alloy of As cast, which is a solution of α-Al (FeMn) during solution treatment. It means that Si is produced.

Hereinafter, the content of the present invention will be described in detail with reference to the following examples. However, these are intended to explain the present invention in more detail, and the scope of the present invention is not limited thereto.

<Example>

Impurity Fe content of 0.06% by weight A356.2 alloy, commercial A356 alloy, 0.20% by weight Fe contained in commercial A356 alloy (A356-0.20Fe), 0.20% by weight Fe, 0.07% by weight Mn in commercial A356 alloy Contained alloy (A356-0.20Fe-0.07Mn), 0.20% Fe by commercial A356 alloy, 0.13% Fe by Mn (A356-0.20Fe-0.13Mn), 0.20% Fe by commercial A356 alloy, 0.20 Alloy containing weight% Mn (A356-0.20Fe-0.20Mn), 0.20% Fe in commercial A356 alloy, Alloy containing 0.40% Mn (A356-0.20Fe-0.40Mn), 0.20 weight in commercial A356 alloy % Fe, alloy containing 0.07% by weight Cr (A356-0.20Fe-0.07Cr), 0.20% Fe by commercial A356 alloy, alloy containing 0.13% by weight Cr (A356-0.20Fe-0.13Cr), commercial A356 Alloy containing 0.20% by weight Fe, 0.20% by weight Cr (A356-0.20Fe-0.20Cr), alloy containing 0.20% by weight Fe, 0.13% by weight Cr, 0.13% by weight Mn in commercial A356 alloy (A356- 0.20Fe-0.13Cr-0.13Mn), 0.20% by weight Fe, 0.07% by weight Cr, 0.30% by weight Mn in commercial A356 alloy Tensile strength and elongation of the alloy containing (A356-0.20Fe-0.07Cr-0.30Mn) were measured by ASTM-related regulations, and the results are shown in Table 1 below.

Impurity Fe, addition alloy chromium and manganese were added as follows. First, the A356 alloy was dissolved at 750 to 770 ° C, and then added to the A356 alloy to contain 0.20% by weight of Fe using an Al-50% by weight Fe mother alloy, followed by complete dissolution. Then, the final chemical composition was adjusted by adding Al-20% by weight Cr and Al-20% by weight Mn master alloy to the A356 alloy so that Fe contained 0.20% by weight.

It can be seen that the tensile strength and the elongation of A356-0.2Fe, in which 0.20% by weight of Fe is added to the A356 alloy, are significantly lower than those of the high purity A356.2 alloy and A356 alloy.

When Cr or Mn was added to A356-0.2Fe containing 0.20% by weight of Fe in the A356 alloy, the tensile strength and elongation were inversely changed. Compared with the commercial A356 alloy, the tensile strength of A356-0.20Fe-0.20Cr with 0.20% by weight Cr was decreased, but the elongation was increased.In contrast, the tensile strength of A356-0.20Fe-0.40Mn with 0.4% by weight Mn was added. Increases, but elongation decreases.

That is, the addition of Mn is effective to increase the tensile strength because it not only controls the needle-like β-Al ₅ FeSi as shown in Fig. 2 and 3, but also precipitates fine particles on the aluminum matrix, and the addition of Cr Elongation of the alloy is effective to increase.

Impurities in A356-0.20Fe-0.13Cr-0.13Mn alloy with 0.13% by weight Cr and 0.13% by weight Mn or in A356-0.20Fe-0.07Cr-0.30Mn with 0.07% by weight Cr and 0.30% by weight Mn Even though Fe contained 0.20% by weight, the tensile strength and elongation were improved than those of commercial A356 alloy and high purity A356.2 alloy. This result comes from microstructure. In other words, α-Al (FeMnCr) Si, which is a particle produced during the solidification process, becomes fine at about 1 μm when Cr and Mn are added in combination, and thus does not adversely affect tensile properties, and α- precipitates on aluminum base after heat treatment. This is because Al (FeMnCr) Si particles are further refined.

As a result, when Cr and Mn are added in combination, Cr and Mn functionally control the coagulation and precipitation structures, respectively, and Cr contributes to increase the elongation and Mn contributes to increase the strength. Will be improved at the same time. In addition, the weight percentage of chromium and manganese to be added depends on the weight percentage of Si and Fe in the AlSiMg alloy, and 0.01 to 0.20 wt% when Si is changed to 6.5 to 7.5 wt% and Fe is incorporated as impurities to 0.30 wt%. By adding Cr and 0.02 to 0.40% by weight of Mn, the effect of improving the structure and improving the tensile property was excellent.

Table 1. Changes in tensile strength and elongation according to the amount of Cr and Mn added

Psalm Tensile Strength (MPa) Elongation (%) High purity A356.2 280 11.0 Commercial A356 270 9.7 A356-0.20Fe 265 5.5 A356-0.20Fe-0.07Mn 266 7.5 A356-0.20Fe-0.13Mn 275 10.0 A356-0.20Fe-0.20Mn 277 7.0 A356-0.20Fe-0.40Mn 280 6.3 A356-0.20Fe-0.07Cr 278 9.2 A356-0.20Fe-0.13Cr 270 11.0 A356-0.20Fe-0.20Cr 257 7.5 A356-0.20Fe-0.13Cr-0.13Mn 285 12.3 A356-0.20Fe-0.07Cr-0.30Mn 288 12.0

According to the effect of the present invention, a low-purity, low-purity AlSiMg alloy or a regenerated AlSiMg alloy having a high content of impurity Fe can be commercialized as an alloy for manufacturing automobile aluminum wheels.

Therefore, the import of expensive high-purity AlSiMg alloys is reduced, and the use of domestically recycled AlSiMg alloys or low-purity AlSiMg alloys reduces imports and activates the recycling industry of AlSiMg alloys, and reduces automobile aluminum wheel manufacturing costs. .

The AlSiMg alloy with improved tensile properties and elongation according to the present invention can be provided as an aluminum wheel for automobiles, aluminum casting parts for transportation equipment, and other parts alloys.

As described above, although described with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified and modified within the scope of the present invention without departing from the spirit and scope of the invention described in the claims below. It will be appreciated that it can be changed.

Claims (4)

A method for producing an AlSiMg main alloy in which α-Al (FeMnCr) Si precipitated particles are formed in an alloy composition by adding 0.01 to 0.20 wt% of chromium and 0.02 to 0.40 wt% of manganese to an AlSiMg alloy composition containing Fe as an impurity. The method of manufacturing an AlSiMg main alloy according to claim 1, wherein cross slip is generated around α-Al (FeMnCr) Si precipitated particles. delete delete

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