KR101567094B1 - Aluminum alloy for casting and forging casting and forged product for suspension and method for manufacturing the same - Google Patents

Abstract

The present invention relates to an aluminum alloy for casting forgings, and more particularly, to an aluminum alloy for casting forgings, which comprises 2 to 3 wt% of silicon, 0.6 to 0.9 wt% of magnesium, 0.2 to 0.8 wt% of copper, 0.2 to 0.6 wt% of zinc ), 0.03 to 0.2 wt% manganese (Mn), 0.01 to 0.1 wt% of titanium, 0.05 to 0.35 wt% of chromium, 0.001 to 0.05 wt% of strontium (Sr) (P) of 0.001 wt% or less, and aluminum (Al) of the remaining amount.

The present invention also relates to a cast forged article for a suspension device manufactured using the aluminum alloy for casting forging and a method of manufacturing the same.

Description

TECHNICAL FIELD [0001] The present invention relates to an aluminum alloy for casting forging, a casting forgings for suspension device, and a method for manufacturing the same. BACKGROUND ART [0002]

The present invention relates to an aluminum alloy for casting forgings, and more particularly, to an aluminum alloy for casting forgings which is excellent in castability and monocomponent composition and has a high strength and toughness to make a complicated shape.

The present invention also relates to a cast forged article for a suspension device manufactured using the aluminum alloy for casting forging and a method of manufacturing the same.

Al-Si-Mg-based casting alloys, Al-Mg-Si-based alloys and Al-Cu-Mg forging alloys have conventionally been used in a wide variety of fields with appropriate strength.

In this type of alloy, A356 (including AC4CH and AC4C) as the casting alloy, 6061 alloy and 2011 alloy as the forging alloy are typical alloys.

However, since the Al-Si-Mg casting alloy is formed by pouring the molten metal into the cavity of the metal mold, it is possible to easily form a complicated shape at low cost, but the strength and elongation are not sufficient, There is a problem that the material reliability is lacking (for example, casting defects) as compared with the alloy. In addition, the Al-Si-Mg casting alloy described above tends to cause forging defects such as forging cracks because the castability is deteriorated even if it is forged.

On the other hand, Al-Mg-Si and Al-Cu-Mg forging alloys are excellent in strength, elongation and reliability, while forging materials are forged through multiple processes (such as sulfur forging, forging and finishing forging) There is a problem that the forging cost is high and finally the manufacturing cost rises. Particularly, since the ability to form a product by one forging is limited, a plurality of times of sulfur forging and forging should be carried out in order to finally obtain a desired shape. In addition, there is a disadvantage in that it is not suitable for a product having a complicated shape because the forging performance of the forging alloy is limited.

Therefore, recently, by using a molten aluminum alloy having a main composition and a single composition, a preform having a shape similar to the final shape of the product is formed by casting, and then the preform is hot-forged, Al-Si-Mg alloys have been proposed as a method for producing cast aluminum alloys and cast forgings, which not only reduce the number of forging but also provide mechanical properties such as tensile strength and elongation to the same extent as forgings , And the weight reduction of chassis components (in particular, suspension devices) has been solved to some extent.

However, in the case of an aluminum alloy for casting forging mainly composed of the Al-Si-Mg-based alloy, there is a problem in that it is not sufficient in terms of strength and elongation.

Al-Mg-Si alloys (JIS 6000 series), Al-Cu-Mg series alloys (JIS 2000 series) and Al-Zn-Mg series alloys (JIS 7000 series) are known as high- Forging products made of these alloys are excellent in terms of strength and elongation, but their applications are limited to complicated shapes, and there is a disadvantage in that the cost of materials is increased because there are restrictions on use in terms of material recovery rate and recycling.

Accordingly, an object of the present invention is to provide an aluminum alloy for casting forging, which is excellent in castability and mono-composition, possesses high strength and toughness to make a complicated shape, .

It is another object of the present invention to provide a cast forged article for a suspension device manufactured using the aluminum alloy for casting forging and a method of manufacturing the same.

According to the aluminum alloy for casting forging according to the present invention, the above object is achieved by providing a casting forging aluminum alloy comprising 2 to 3 wt% of silicon, 0.6 to 0.9 wt% of magnesium, 0.2 to 0.8 wt% of copper, 0.2 to 0.6 wt% of zinc (Zn), 0.03 to 0.2 wt% manganese (Mn), 0.01 to 0.1 wt% of titanium, 0.05 to 0.35 wt% of chromium, 0.001 to 0.05 wt% of strontium (Sr) Fe), 0.001 wt% or less of (P), and the balance aluminum (Al).

According to another aspect of the present invention, there is provided a method of manufacturing a single cast article for a suspension, comprising: casting a molten aluminum alloy to form a preform; Preheating the preform; And preheating the preform at a reduction rate of 5 to 25% for one time.

At this time, the step of solution-treating the product, which has been subjected to hot forging, at 530 to 550 ° C; Quenching the product after the solution treatment is completed, and aging the product at 150 to 170 ° C or 170 to 180 ° C.

On the other hand, the above object is achieved by a cast forgings for a suspension device manufactured by the above manufacturing method.

INDUSTRIAL APPLICABILITY As described above, according to the present invention, there is provided an aluminum alloy for casting forgings which is excellent in castability and monocomponent composition and has high strength and toughness to make a complicated shape.

In addition, the present invention provides a cast forgings for a suspension device manufactured using the aluminum alloy for casting forgings and a method of manufacturing the same.

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

The aluminum alloy for casting forging according to the present invention is characterized by containing 2 to 3 wt% of silicon, 0.6 to 0.9 wt% of magnesium, 0.2 to 0.8 wt% of copper, 0.2 to 0.6 wt% of zinc, 0.03 to 0.2 wt% manganese (Mn), 0.01 to 0.1 wt% of titanium, 0.05 to 0.35 wt% of chromium (Cr), 0.001 to 0.05 wt% of strontium (Sr) (P) of less than or equal to wt% and aluminum (Al) of the remaining amount.

First, the reason why the chemical composition constituting the aluminum alloy for casting forging is limited as described above will be described in detail below.

(1) Silicon (Si) is one of the important features of the alloy of the present invention. When silicon (Si) content is increased, the casting fluidity is good, the casting shrinkage and hot tearing are suitable . In addition, Mg ₂ Si precipitates by heat treatment at the time of alloying with magnesium (Mg) serve to improve the strength. On the other hand, when the content of silicon (Si) is insufficient, the hot tearing sensitivity is increased and the casting fluidity is remarkably decreased.

At this time, when the content of silicon (Si) exceeds 3.0%, the hot brittleness sensitivity and casting fluidity are improved but the strength and elongation tend to be significantly lowered, so the content should be limited.

Accordingly, in the present invention, the content of silicon (Si) is limited to 2.0 to 3.0 wt% in consideration of the hot brittle sensitivity, casting fluidity, strength and elongation.

(2) Magnesium (Mg) plays a role in improving mechanical properties. That is, when magnesium (Mg) coexists with silicon (Si), Mg ₂ Si is precipitated by heat treatment to improve strength, and exhibits aging properties in the presence of Si-Zn. Magnesium (Mg) alone also exhibits a solid solution strengthening effect to increase strength and elongation.

However, it has a characteristic of generating a large amount of impurities during casting and deteriorating fluidity, and it is necessary to have a special circumstance when casting because it may cause oxide inflow due to strong bonding force with oxygen.

On the other hand, when the content of magnesium (Mg) is insufficient, the mechanical properties are insufficient, and when it is excessive, the casting, mono-composition, stress corrosion cracking and hot tearing sensitivity are high and elongation is decreased.

Therefore, in the present invention, the content of magnesium (Mg) is limited to 0.6 to 0.9 wt% in terms of mechanical properties.

(3) Copper (Cu) is good for increasing strength and hardness because it has aging property. At this time, when copper (Cu) is insufficient, mechanical properties are insufficient, and when it is excessive, the casting fluidity is deteriorated and hot tearing sensitivity is high.

Particularly, when copper (Cu) content is more than 0.8 wt%, corrosion resistance is very poor and stress corrosion cracking tends to occur.

Therefore, in the present invention, the content of copper (Cu) is limited to 0.2 to 0.8 wt%.

(4) Zinc (Zn) is effective for improvement of mechanical properties, but when applied to casting forging alloys, the sensitivity of hot tearing is very high and shrinkage of the preform is increased, The content should be limited.

When zinc (Zn) is insufficient, mechanical properties are deteriorated, and when it is excessive, casting, mono-composition, stress corrosion cracking, and elongation are decreased.

Therefore, in the present invention, the content of zinc (Zn) is limited to 0.2 to 0.6 wt%.

(5) Manganese (Mn) plays a role to prevent grain refinement and casting shrinkage. When copper (Cu) and silicon (Si) are contained, the effect of improving the high temperature strength is effective, and when the proper content is included, the elongation increasing effect can be obtained.

On the other hand, when manganese (Mn) is insufficient, the effect of increasing the elongation can not be obtained. In the case of excess, coexisting with Fe generates Al-Mn-Fe and adversely affects the strength.

In particular, in the present invention, when the content of manganese (Mn) is less than 0.03 wt%, the tensile strength and the yield strength are considerably high but the elongation is remarkably decreased. In the present invention, the content of manganese (Mn) is 0.03 to 0.2 wt% .

(6) Titanium (Ti) serves to refine the cast structure of an aluminum alloy. When the content is large, the precipitates of the inclusions are increased to deteriorate the mechanical properties. Therefore, in the present invention, the content of titanium (Ti) is limited to 0.01 to 0.1 wt%.

(7) Chromium (Cr) is an effective element which interferes with recrystallization of an aluminum alloy during forging. When it is contained in a large amount, hardening of matrix is increased and workability is lowered. Is limited to 0.05 to 0.35 wt%.

(8) Strontium (Sr) serves to refine the process silicon (Eutectic Si). When the content is less than 0.001 wt%, the above-mentioned characteristics can not be obtained. When the content exceeds 0.05 wt% The content of strontium (Sr) is limited to 0.001 to 0.05 wt% in the present invention.

(9) Iron (Fe) is limited to 0.15 wt% or less, and phosphorus (P) is limited to 0.001 wt% or less.

Iron (Fe) and phosphorus (P) are impurities which are likely to be mixed in the refining and casting process of aluminum. When the content is large, the mechanical properties are deteriorated. When aluminum is inevitably involved in refining and casting process, it is preferable that iron (Fe) is 0.15 wt% or less and phosphorus (P) is 0.001 wt% or less.

That is, when a large amount of iron (Fe) is contained, the elongation rate is lowered by crystallizing an Fe-based intermetallic compound, so that it is preferable to regulate the content of iron (Fe) to 0.15 wt% or less.

Further, when a large amount of phosphorus (P) is contained, the content of phosphorus (P) is preferably 0.001 wt% or less in order to prevent the effect of refining (improving treatment) of the process Si in the molten bath effectively.

Table 1 below shows alloy compositions and composition ranges for aluminum alloys for casting forging according to the present invention, composition and composition ranges of comparative alloys, and Table 2 shows alloys of Table 1 And then subjected to tensile test on the tensile test specimens obtained from the materials produced by solution treatment and aging treatment after casting and forging.

[Table 1]

No alloy Si Mg Zn Mn Cu Cr Fe Ti Sr P Al A Comparison 1
(A356 alloy) 6.5
~ 7.5 0.25
~ 0.45 0.1
Below 0.1
Below 0.2
Below 0.05
Below 0.2
Below 0.2
Below - - Honey. B Comparative material 2
(6061 alloy) 0.4
~ 0.8 0.8
~ 1.2 0.25
Below 0.15
Below 0.15
~ 0.4 0.04
~ 0.35 0.7
Below 0.15
Below - - Honey. C Comparative material 3
(2011 alloy) 0.4
Below - 0.3
Below - 5
~ 6 - 0.7
Below - - - Honey. D The
Alloy composition range 2.0
~ 3.0 0.6
~ 0.9 0.2
~ 0.6 0.03
~ 0.2 0.2
~ 0.8 0.05
~ 0.35 0.15
Below 0.01
~ 0.1 0.001
~ 0.05 0.001
Below Honey . One Comparison 1
(A356 alloy) 7.31 0.45 0.005 0.009 0.002 0.001 0.11 0.12 - 6 ppm Honey. 2 Comparative material 2
(6061 alloy) 0.77 0.92 0.01 0.03 0.23 0.14 0.22 0.04 - - Honey. 3 Comparative material 3 Correction alloy (2011 Correction alloy) 0.34 0.10 0.03 0.02 2.38 0.03 0.24 0.035 0.020 - Honey. 4 Comparison 4 1.11 1.05 0.02 0.03 0.21 0.14 0.30 0.04 - 46 ppm Honey. 5 Comparative material 5 5.40 0.60 0.03 0.002 0.70 - 0.12 0.14 0.02 8 ppm Honey. 6 Comparative material 6 2.54 0.77 0.24 0.007 0.56 0.13 0.10 0.03 0.028 6 ppm Honey. 7 Comparison 7 2.59 0.67 0.41 0.007 0.48 0.13 0.10 0.03 0.021 6 ppm Honey. 8 COMPARISON 8 2.15 0.68 0.41 0.06 0.17 0.10 0.09 0.05 0.020 6 ppm Honey. 9 Comparative material 9 2.15 0.65 0.75 0.06 0.44 0.11 0.09 0.05 0.015 6 ppm Honey. 10 The
Alloy composition 2.22 0.69 0.39 0.13 0.29 0.12 0.09 0.06 0.014 5 ppm Honey .

[Table 2]

No
alloy Manufacturing conditions Mechanical property casting
Shaped body minor
Shaped body
Remarks Solution
process prescription
process TS
(Mpa) YS
(Mpa) Elongation
(%) One Comparison 1
(A356 alloy) 530
~ 550 ° C 150
~ 160 ° C 309 232 10.7 Molding
possible <- - 2 Comparative material 2
(6061 alloy) 530
~ 550 ° C 150
~ 160 ° C 315 248 9.2 Molding
possible <- Macro
Casting inclusion 3 Comparative material 3 Correction alloy (2011 Correction alloy) - - - - - Molding
possible Molding
Impossible Property evaluation
Impossible 4 Comparison 4 530
~ 550 ° C 150
~ 160 ° C 293 223 7.9 Molding
possible <- Macro
Casting inclusion 5 Comparative material 5 530
~ 550 ° C 150
~ 160 ° C 367 306 4.6 Molding
possible <- - 6 Comparative material 6 530
~ 550 ° C 150
~ 160 ° C 326 279 2.8 Molding
possible <- - 7 Comparison 7 530
~ 550 ° C 150
~ 160 ° C 335 286 3.3 Molding
possible <- - 8 COMPARISON 8 530
~ 550 ° C 150
~ 160 ° C 334 269 7.5 Molding
possible <- - 9 Comparative material 9 530
~ 550 ° C 150
~ 160 ° C 342 264 7.2 Molding
possible <- - 10 The
Alloy 1 530
~ 550 ° C 150
~ 170 ° C 353 277 13 Molding
possible <- - 10-1 The
Alloy 2 530
~ 550 ° C 170
~ 180 ° C 373 326 5.1 Molding
possible <- -

In the above table, No. 1 is a conventional Al-Si-Mg casting A356 alloy, No. 2 is a 6061 alloy as a representative alloy for Al-Mg-Si forging, and No. 3 is a representative alloy for Al- Please note that this alloy is a slight adjustment of the Cu content of the 2011 alloy.

No 1 A356 alloy had the best casting among the alloys shown in [Table 2], but did not achieve a remarkable increase in strength and elongation.

No 2 6061 alloy had similar strength and elongation as A356 alloy but lower than the mechanical properties of hot forging manufactured by general hot forging process. This indicates that the content of silicon (Si) is low and the fluidity of the casting is low and the hot cracking sensitivity is high, so that a large number of Macro casting inclusions are generated in the internal structure.

As shown in Table 1, the modified alloy of No. 3 2011 contains a significantly higher content of Cu (2.38 wt%) as can be seen from the alloy component of Table 1. The casting mold can be molded by the casting process, Hot tearing could be seen as forging hot cracking through forging process and forging could not be done, so that the mechanical properties could not be grasped.

The comparative alloy No. 4 is a comparative alloy with a slightly increased content of silicon (Si) compared to Comparative Material 3 (2011 alloy) and Comparative Material 2 (6061 alloy). The strength and elongation of the comparative alloy 2 And it is found that the casting fluidity is insufficient in the range of about 1 wt% of silicon (Si).

The comparative alloy No. 5 is a comparative alloy in which the content of silicon (Si) is lower than that of the comparative material 1 (A356 alloy) and the content of silicon (Si) is slightly higher than that of the aluminum alloy of the present invention. The yield strength is remarkably high but the elongation is low. In the case of Al-Mg-Si alloy, Mg ₂ Si solid solution (Mg ₂ Si solution) is used. It is known to have a solubility of 1.85 wt% at the processing temperature.

The strength of the Mg ₂ Si precipitation hardening is increased by the T6 heat treatment by applying the casting forging method of the present invention, but the elongation rate is lowered due to the critical value of the magnesium (Mg) content and the critical content of manganese (Mn) Respectively. It is characterized by the existence of a threshold of the combination of silicon (Si), magnesium (Mg), and manganese (Mn) contents.

On the other hand, the elongation of the comparative alloys No. 6 and No. 7 is very low because the content of manganese (Mn) is less than the amount of the aluminum alloy of the present invention. As a result, It is possible to improve the elongation rate only when it is contained at the critical value.

(Cu) content (0.17 wt%) of the No. 8 comparative alloy is lower than the copper content (0.2 to 0.8 wt%) of the aluminum alloy of the present invention because copper (Cu) It shows that there is a threshold of content. At this time, the tensile strength and yield strength of No. 8 are superior to Comparative material 1 (A356 alloy) and Comparative material 2 (6061 alloy) by the casting / forging process but the elongation is slightly lower. The elongation was low.

In addition, the No 9 comparative alloy had mechanical properties similar to those of the No 8 comparative alloy, because the zinc (Zn) content (0.75 wt%) of the aluminum alloy of the present invention (0.2 to 0.6 wt %), Indicating that the strength and elongation were lower than the mechanical properties of the aluminum alloy of the present invention. When the zinc (Zn) content is increased, it is effective for improving the mechanical properties, but the casting fluidity and the hot-brittleness sensitivity are high, and the elongation rate is lowered compared with the aluminum alloy of the present invention.

The aluminum alloy of the present invention exhibits a change in yield strength and elongation according to the T6 heat treatment conditions. When the solution treatment conditions are the same and the aging temperature treatment conditions are changed, excellent results of strength and elongation at an aging temperature of 150 to 170 ° C 2, No 10).

On the other hand, the elongation was somewhat low at an aging temperature of 170 to 180 ° C, but the mechanical properties (Table 2, No. 10-1) with a yield strength of 310 MPa or more were obtained.

Hereinafter, a method of manufacturing a cast forgings (for example, a front steering knuckle) for a suspension using an aluminum alloy for casting forging according to the present invention will be described with reference to FIGS. 1 and 2. FIG.

First, the Al-based alloy for casting forging excellent in castability and mono-composition is melted.

After the dissolved molten metal is degassed, the molten metal is injected into the cavity of the metal mold at a filling speed of not more than 1 m / sec.

Water, Air and Water and Air Mixture cooling method is selected and solidified with molten metal to obtain cast preform (10) which is similar to the final product.

The cast preform 10 is similar in shape to the final product but forms a pressurizing portion 15 into which molten metal is injected, and the pressurizing portion 15 thus formed is removed by machining or forging.

After the molten metal for casting the molten metal is solidified into the cast preform 10, the cast preform 10 is separated from the metal mold.

The cast preform 10 is preheated to a forging preheat temperature of 500 to 550 占 폚. The reason for preheating the cast preform 10 is to increase the fluidity of the material and to reduce the pressing force in the hot forging process.

The cast preform (10) which has been preheated is hot-forged once at a reduction rate of 5 to 25%. This reduction rate can give reliability to the cast preform 10, that is, even if a casting defect occurs in the casting process, casting defects present in the cast preform 10 are lost while forging, .

Thus, the product molded by the hot forging process is referred to as a material 20 after the forging process. Generally, a flash (Flash) 25 is formed in the material after the forging process. Therefore, the casting forgings 30 are formed by removing the flash 25 by a trimming process.

Thereafter, the hot-forged product is subjected to a solution treatment at 530 to 550 ° C, and then the solution-finished product is quenched (generally quenched to room temperature) and then heated to a temperature of 150 to 170 ° C or 170 to 180 ° C It may be aged. At this time, the aging treatment is carried out in one stage, but the aging treatment in two stages may be carried out in some cases.

By performing the solution treatment temperature at 530 to 550 ° C and the aging treatment temperature at 150 to 170 ° C, it is possible to produce materials and products requiring relatively high strength and high elongation. That is, the tensile strength is 340 MPa or more, the yield strength is 270 MPa or more, and the elongation is 10% or more, so that the mechanical properties can be improved (see Table 2).

On the other hand, by performing the solution treatment temperature at 530 to 550 ° C and the aging treatment temperature at 170 to 180 ° C, it is possible to produce materials and products requiring relatively high strength. In other words, the tensile strength is higher than 360 MPa and the yield strength is higher than 310 MPa to improve the mechanical properties (see Table 2).

Finally, the finished product 40 is formed by machining and assembling the functional parts on the cast forgings 30.

At this time, since the flash 25 removed by the pressing unit 15 after the hot forging process is removed and the flash 25 removed by the trimming process can be dissolved again in the material melting process for forming the molten metal, Recycling is possible.

Hereinafter, the change in the cross-section and the shape of the cast preform 10 when the cast preform 10 is formed into the material 20 after the forging process by the hot forging will be described with reference to FIGS. 3 and 4 Describe in detail.

The cast preform 10 has a schematic shape and dimensions of the finished product 40.

Thus, the cast preform 10 having a rough shape and dimensions of the final finished product 40 is subjected to a forging process so as to have a shape and dimensions similar to those of the final finished product 40.

Generally, in mold forging, a spare material remaining after filling the cavity of the mold forms a flash 25, and Precision Forging or Flashless Forging is a method in which a product molded by a forging process is subjected to a desired final It is a near net-shape machining that is nearly equal to the dimensions of the product.

As shown in Fig. 3, the cast preform 10 is indicated by a solid line, and after the forging process in which the forging process is completed, the material 20 is changed into a shape including a dot.

Hereinafter, the main part in which the cross-section and the shape of the cast preform 10 are changed by the forging process will be mainly described.

(1) Before the forging process, the section AA of the cast preform 10 is indicated by a thin solid line as shown in Fig. 4 (a), and the entire portion corresponding to the upper portion of the finished steering knuckle The shape of the cross section is close to H character.

There are two places at the upper and lower sides with a height higher than the width of the center line of the cross section AA respectively and a groove with a lower height exists between the upper and lower portions at the upper and lower sides of the horizontal center line of the cross section AA . On the other hand, protrusions are protruded in the lateral direction on the outer side surface of the upper portion with respect to the horizontal center line of the section A-A.

 After completion of the forging process, the cross section AA of the material 20 after the forging process is shown by a thick solid line as shown in FIG. 4 (a), and a mold (not shown) used in the forging process is formed as a cast preform 10, the flow of the material occurs. At this time, the material to be moved moves in the direction of filling the cavity of the mold.

That is, the portion of the cast preform 10 having a high height is lowered in height, and the groove of the cast preform 10 is deepened. Further, the width of the cast preform 10 increases in the lateral direction, and protrusions formed on the outer side of the portion of the cast preform 10 having a high height by the forging process are further projected outwardly.

At this time, the reduction rate of the section A-A of the cast preform 10 is 24.8% according to an experiment.

(2) Before the forging process, the cross section B-B of the cast preform 10 is indicated by a thin solid line and corresponds to the middle part of the finished steering knuckle, as shown in Fig. 4 (b).

The overall shape of the cross-section BB of the cast preform 10 is that two high-height portions are present at the upper side with respect to the transverse center line of the cross-section BB, and between the high- Lt; / RTI &gt;

On the other hand, a protrusion slightly protruding downward is formed on the lower part of the end surface BB, a protrusion protruding outward is formed on the side surface of the end surface BB, and when the end surface BB is viewed from the front, .

After the forging process is completed, the cross section B-B of the material 20 after the forging process changes to a thick solid line as shown in Fig. 4 (b).

Therefore, the portion of the cast preform 10 having the high section of the section B-B becomes low, and the section of the section of the high section of the section B-B becomes deep.

On the other hand, a protrusion protruding downward at the lower portion of the cross section B-B further protrudes downward, and a width of the cross section B-B increases in a lateral direction, so that protrusions formed on the side surface of the cross section B-B protrude further outward. Further, when the cross-section B-B is viewed from the front, the concave portion formed in the right lower side becomes more concave in the inward direction.

At this time, the reduction rate of the section B-B of the cast preform 10 is 12.7% according to the experiment.

(3) The section C-C of the cast preform 10 is a thin solid line, and the section C-C of the material 20 after the forging process is changed to a thick solid line.

Section C-C of the cast preform 10 corresponds to the lower portion of the front steering knuckle as a finished product.

The overall shape of the cross section C-C of the cast preform 10 is as follows, see Fig. 4 (c).

First, when the section C-C is viewed from the front, the shape of the portion on the left side will be described.

A curve is formed on the upper right side from the left side of the lateral center line of the section C-C of the cast preform 10, and a curve formed uniformly on the upper right side is formed again on the lower right side.

On the other hand, a curve is formed on the lower right side from the left side of the transverse center line of the section C-C of the cast preform 10, and a curved line is formed upward from the lower right portion of the cross section of the cast preform 10.

The height of the cross section C-C of the cast preform 10 is reduced by the forging process (see a thick solid line).

Next, when the section C-C is viewed from the front, the shape of the portion on the right side will be described.

Is formed at a lower portion with respect to the transverse center line of the cross section C-C of the cast preform 10, and has a concave portion on the left side and a projection on the right side.

Between the concave portion and the projection, a high-height portion is formed, and a concave portion is formed at the bottom.

The height of the high-height portion formed between the concave portion and the projection is reduced by the forging process, and the concave portion of the concave portion at the bottom is enlarged (see a thick solid line).

At this time, the reduction rate of the section C-C of the cast preform 10 is 8.1% according to the experiment.

As described above, according to the present invention, not only is it possible to form a complicated shape with high castability and monotone, high strength and high toughness, but also to reduce the weight and weight of the product compared to the conventional Al- A cost saving effect can be obtained.

It is also possible to remove the sulfur / forging process for conventional alloys of Al-Mg-Si, Al-Cu-Mg and Al-Zn-Mg forgings by hot forging the cast preforms similar to the finished product It is possible to reduce the number of sulfur / constant forging processes.

In addition, since the molten metal can be reused by the molten metal after the casting and the flash after the forging, the manufacturing cost can be reduced.

In the above-described embodiment, the solution treatment time may be from 3 to 12 hours at 530 to 550 ° C. The time for the first stage aging treatment may be from 3 to 12 hours. The time may be 3 to 12 hours, but it goes without saying that the time may vary depending on the composition, material shape and size of the aluminum alloy of the present invention.

It will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims. .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a process diagram showing a method for producing a cast forging for a suspension device using an Al-based alloy for casting forging according to the present invention. FIG.

Fig. 2 is a view showing a process of completing a cast forged article (front-wheel knuckle) for suspension using an Al-based alloy for casting forging according to the present invention.

Fig. 3 is a view showing the preform of Fig. 2 together with the material after the forging process; Fig.

3 is a cross-sectional view taken along the line AA in Fig. 3, Fig. 3 (b) is a sectional view taken along line BB of Fig. 3, Fig. 4 Line section.

DESCRIPTION OF THE REFERENCE NUMERALS

1: preform 20: material

30: Cast forging 40: Finished product

Claims (4)

2 to 3 wt% of silicon, 0.6 to 0.9 wt% of magnesium, 0.2 to 0.8 wt% of copper, 0.2 to 0.6 wt% of zinc, 0.03 to 0.2 wt% of manganese, (Ti), 0.05 to 0.35 wt% of chromium (Cr), 0.001 to 0.05 wt% of strontium (Sr), 0.15 wt% of iron (Fe), 0.001 wt% or less of (P) Aluminum alloy for casting forging made of aluminum (Al). Casting a molten aluminum alloy casting forging according to claim 1 to form a preform; A preheating step of preheating the preform; And a hot forging step of subjecting the preheated preform to hot forging once at a reduction rate of 5 to 25% Wherein a different reduction ratio is applied to each part of the preform in the hot forging step. The method of claim 2, Treating the product for which the hot forging is completed at a temperature of 530 to 550 ° C; Further comprising the step of quenching the product after the solution treatment is completed, and aging the product at 150 to 170 ° C or 170 to 180 ° C. A cast forged article for a suspension device produced by the method of claim 1 or 2.

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