KR20180046764A - Manufacturing method of hot stamping aluminuim case and hot stamping aluminuim case manufacturing by the method - Google Patents

Abstract

The present invention relates to a manufacturing method of a hot stamping aluminium case, and a hot stamping aluminium case manufactured thereby. The hot stamping aluminium case can tensile strength and elongation of an aluminium alloy, optimize a process to enalbe stable measurement, post-treatment, and a yield with respec to the tensile strength and elognation, and prevent occurrence of damage such as pinholing, contraction, cracks, and pore so as to increase property. Moreover, a process can be easily performed so that process costs of an aluminium alloy material and time can be reduced. At the same time, properties of the alloy such as strength and hardness can be maintained in an improved state.

Description

TECHNICAL FIELD [0001] The present invention relates to a hot stamping aluminum case and a hot stamping aluminum case made by the same. BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a hot stamping aluminum case,

The present invention relates to a method of manufacturing a hot stamped aluminum case and a hot stamped aluminum case manufactured by the method. More particularly, the present invention relates to a hot stamped aluminum case manufactured by a method of manufacturing a hot stamped aluminum case, And a hot stamped aluminum case made by the method.

Aluminum alloy is an alloy that is widely used in almost all industrial fields such as automobile, aircraft, construction, machinery, and electronics because it is light in weight and excellent in corrosion resistance and processability. In general, aluminum (Al) is easy to cast, is well alloyed with other metals and alloys, is easily processed at room temperature and high temperature, has strong resistance to the atmosphere in the atmosphere, and has excellent electric and thermal conductivity.

Since the strength of aluminum itself is not high compared to other metals, aluminum alloy which is made by mixing other metals with aluminum is widely used. The aluminum alloy may be a metal such as copper (Cu), silicon (Si), magnesium (Mg), zinc (Zn), iron (Fe), manganese (Mn), nickel (Ni) , And it can be classified into an aluminum alloy for casting such as sililmine and a router and an aluminum alloy for processing such as duralumin, hydrotalcite and almin, depending on the type and content of the metal to be mixed together.

In addition, die casting is widely used as a method for producing a product using such an aluminum alloy. Die casting is performed by injecting molten metal into a precisely machined die according to a required casting shape to obtain the same casting as a die Precision casting method.

According to the die casting described above, since the dimensions of the product to be produced are accurate, there is little need to finishing the product, the mechanical properties are excellent, the mass production is possible and the production cost is low, And measuring instruments.

However, in the case of die casting, a large amount of silicon (Si) added has a disadvantage that it can not express the luster and texture inherent to the metal. The manufacture of the metal case using such a die casting process has been optimized I can not stand it. Accordingly, it is necessary to develop a manufacturing process that can improve the physical properties of the aluminum alloy while saving the inherent luster and texture of the metal, while being easier and more productive.

In this connection, Korean Patent Laid-Open Publication No. 10-2012-0085397 discloses that aluminum silicon zinc alloy for die casting can be used to cast thinner and lighter interior and exterior materials for portable electronic devices. However, in the case of conventional die casting, 1) the alloy used for die casting has low tensile strength and elongation, 2) the process for stable dimension, post-processing and increase of yield is not optimized, and 3) Defects such as dimensional discrepancies occur, and 4) there is a problem that post-processing and surface treatment are difficult.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and it is an object of the present invention to solve the problems of the prior art by increasing tensile strength and elongation, optimizing processes for stable dimension, post- , A method of manufacturing a hot stamped aluminum case in which defects such as shrinkage, cracks and pores are not generated, and a hot stamped aluminum case manufactured by the method.

Also, by a method and a method for manufacturing a hot stamped aluminum case, which can reduce the processing cost and time of the aluminum alloy material by facilitating the process, and at the same time, the physical properties such as strength and hardness of the alloy can be kept excellent Another object is to provide a manufactured hot stamped aluminum case.

(2) a step (3) of extruding the preheated aluminum alloy to a flat bar; (3) a step of extruding the preheated aluminum alloy into a flat bar; Hot stamping the flat bar to a temperature equal to or higher than the solvus temperature of the alloy, (4) quenching the hot-stamped flat bar, and (5) heating the quenched flat bar, The hot stamping step in the step (3) provides a method of manufacturing a hot stamped aluminum case that does not include a solution processing step.

According to a preferred embodiment of the present invention, the Al-Zn-Mg-Cu-based aluminum alloy in the step (1) comprises 1.0 to 2.2 wt% of Mg, 4.0 to 5.5 wt% of Zn, 0.1 to 0.9 wt% And the remaining Al and unavoidable impurities.

According to another preferred embodiment of the present invention, the preheating temperature of step (1) may be 350 to 550 ° C.

According to another preferred embodiment of the present invention, the extrusion ratio of the cross-sectional area of the aluminum alloy may be 30 to 60 before and after extrusion in the step (2).

According to another preferred embodiment of the present invention, the heating temperature in the hot stamping in the step (3) may be 350 to 550 ° C, and the heating time may be 5 seconds to 1 hour.

According to another preferred embodiment of the present invention, the hot stamping step of the step (3) may not include a solution process.

According to another preferred embodiment of the present invention, the quenching in the step (4) may be performed with a fluid or water.

According to another preferred embodiment of the present invention, the quenching in the step (4) may be performed within 30 seconds after the step (3).

According to another preferred embodiment of the present invention, quenching in the step (4) may be performed within 3 seconds after the step (3).

According to another preferred embodiment of the present invention, the artificial aging in the step (5) is performed by: 1) a first heat treatment step performed for 4 to 6 hours at a temperature of 100 to 110 ° C; and 2) And a second heat treatment step performed for about 8 hours, and the temperature raising rate may be 0.5 to 50 ° C / min.

In order to solve the above-mentioned problems, the present invention provides a method of manufacturing a semiconductor device, comprising: a step of forming a first insulating layer made of 1.0 to 2.2 wt% of Mg, 4.0 to 5.5 wt% of Zn, 0.1 to 0.9 wt% of Cu, and the balance of Al and unavoidable impurities, A hot stamped aluminum case of 50 to 65 HRB is provided.

A method of manufacturing a hot stamped aluminum case according to the present invention and an aluminum case produced by the method increase the tensile strength and elongation of an aluminum alloy and optimize processes for stable dimensions, post-processing and yield, Defects such as pinholes, shrinkage, cracks, pores and the like can be prevented from occurring and the physical properties can be increased.

Further, the process can be easily performed, thereby reducing the processing cost and time of the aluminum alloy material, and at the same time, the properties such as the strength and hardness of the alloy can be kept excellent.

1 is a flowchart of an aluminum case manufacturing process using a hot stamping process according to an embodiment of the present invention.
Figure 2 schematically illustrates an extruded aluminum alloy flat bar according to one embodiment of the present invention.
3A is a photograph of an aluminum alloy flat bar and a specimen after performing the extrusion step according to an embodiment of the present invention.
3B is a photograph of a specimen of an aluminum alloy flat bar after performing the quenching step according to an embodiment of the present invention.
3C is a photograph of a specimen of an aluminum alloy flat bar after the artificial aging heat treatment step according to an embodiment of the present invention.
4A is an optical microscope photograph of an aluminum alloy flat bar after performing an extrusion step according to an embodiment of the present invention.
4B is an optical microscope photograph of an aluminum alloy flat bar after performing the quenching step according to an embodiment of the present invention.
4C is an optical microscope photograph of an aluminum alloy flat bar after the artificial aging heat treatment step according to an embodiment of the present invention.
FIG. 5A is an image and a graph of an EDS measurement of an aluminum alloy flat bar specimen after the extrusion step according to an embodiment of the present invention. FIG.
FIG. 5B is an image and a graph of an EDS measurement of an aluminum alloy flat bar specimen after performing a quenching step according to an embodiment of the present invention.
6 is a photograph of a metal case forging die for hot stamping according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. It should be understood, however, that the embodiments are not intended to limit the scope of the present invention, which should be construed to facilitate understanding of the present invention.

As described above, there is a problem that the inherent luster and texture of the metal can not be expressed due to a large amount of silicon (Si) added at the time of manufacturing the aluminum alloy metal case using the conventional die casting method, and the tensile strength and elongation are low There is a problem that the process for stable dimension, post-processing and increase of yield is not optimized, and defects such as pores and dimensional mismatch occur during the die casting process, and there is a problem that post-processing and surface treatment are difficult.

(2) a step of extruding the preheated aluminum alloy into a flat bar; (3) a step of extruding the flat bar to a heating temperature of the alloy (4) a step of quenching the hot-stamped flat bar, and (5) an artificial aging step of heating the quenched flat bar. So as to solve the above-mentioned problems. By this, it is possible to increase the tensile strength and elongation of aluminum alloy, optimize the process for stable dimension, post-processing and increase the yield, and prevent defects such as pinholes, shrinkage, Can be increased. It is also possible to express the gloss and texture inherent in the metal.

That is, according to the present invention, the hot stamping process, which is one of the forging processes used in steel but not the die casting process, is followed by a quenching step and an artificial aging step, It is possible to obtain an aluminum case having excellent physical properties in a simple process by preventing defects such as pinholes, shrinkage, cracks and pores from occurring in the aluminum alloy material and increasing the physical properties such as strength and hardness of the aluminum alloy.

1 is a flowchart of an aluminum case manufacturing process using a hot stamping process according to a preferred embodiment of the present invention. As shown in the figure, in the aluminum case manufacturing process of the present invention, the Al-Zn-Mg-Cu-based aluminum alloy is preheated and the flat bar is extruded. Solvus Temperature) and performing quenching after hot stamping.

First, (1) a step of preheating an Al-Zn-Mg-Cu-based aluminum alloy will be described.

The aluminum alloy used in the present invention is an Al-Zn-Mg-Cu-based aluminum alloy and is a quaternary alloy. It is an Al-Zn-Mg-Cu heat-treated aluminum alloy of the 7000 series which is the highest strength among aluminum alloys of the 7000 series which is a heat-treated type aluminum alloy of Al-Zn-Mg-Cu type. 7000 series aluminum alloys are extrusion alloys with the highest strength among aluminum alloys and can be used as aircraft structural materials, machinery parts, ships and automobile parts and structural materials along with 2000 series alloys. When manufacturing the aluminum case using the 7000-based aluminum alloy, the 7000-based aluminum alloy has a strength as high as about 60% as compared with other aluminum alloys, and can be easily broken by the impact, It can be mainly used as a frame of an electronic device and has a function of protecting the electronic device from breakage due to impact or the like.

According to a preferred embodiment, remind The Al-Zn-Mg-Cu based aluminum alloy may be composed of 1.0 to 2.2% by weight of Mg, 4.0 to 5.5% by weight of Zn, 0.1 to 0.9% by weight of Cu and the balance of Al and unavoidable impurities.

The contents, properties, roles and functions of the respective components of the aluminum alloy contained in the aluminum case according to the present invention will be described below.

Magnesium (Mg)

Magnesium (Mg) is added to improve corrosion resistance, strength and elongation, and to improve lighter weight and machinability. In addition, the magnesium (Mg) can rapidly form an oxide layer (MgO) on the surface of the product, and the oxide layer (MgO) acts as a coating film on the surface to improve the corrosion resistance.

The magnesium may be contained in an amount of preferably 1.0 to 2.2% by weight, more preferably 1.3 to 2.0% by weight. If the added amount of magnesium is less than 1.0% by weight, the effect of the addition is insufficient and the corrosion resistance, the strength and the elongation are lowered, and the weight reduction and the machinability effect are reduced. On the other hand, when the amount of magnesium added exceeds 2.2% by weight, the problem of foaming may occur as the ignition of Mg starts.

Zinc (Zn)

Zinc (Zn) is added to improve corrosion resistance and strength. In addition, the zinc can improve the strength of the aluminum alloy case through age hardening.

The zinc may be included in an amount of preferably 4.0 to 5.5% by weight, and more preferably 4.2 to 5.2% by weight. If the added amount of zinc is less than 4.0% by weight, corrosion resistance and strength may be lowered. If the added amount of zinc exceeds 5.5% by weight, properties such as corrosion resistance and weldability may be deteriorated.

Copper (Cu)

Copper (Cu) is added to improve hardness, strength through precipitation hardening and ductility. Further, the copper can improve the corrosion resistance, improve the fluidity of the alloy melt, and improve the strength.

The copper may be contained in an amount of preferably 0.1 to 0.9 wt%, more preferably 0.3 to 0.9 wt%, and still more preferably 0.5 to 0.8 wt%. If the addition amount of copper is less than 0.1% by weight, the flowability of the molten aluminum alloy is lowered, and the surface of the aluminum case may be easily damaged due to corrosion. If the addition amount of copper exceeds 1.2% by weight, corrosion resistance, weldability and extrudability may be deteriorated and corrosion may occur.

Aluminum (Al)

Aluminum (Al) is added to improve stable interstice and high strength properties and increase fluidity.

The aluminum may preferably constitute the remainder of the aluminum alloy except for magnesium, zinc, copper and unavoidable impurities.

In addition, impurities in aluminum which can cause corrosion of the alloy when the Al alloy is contained in a proportion of not less than a certain weight percent by weight are adjusted so as not to exceed 0.005% by weight during the manufacturing process, so that hot A stamped aluminum case can be manufactured.

5A is an image and a graph showing the EDS of the aluminum alloy flat bar specimen after the extrusion step according to the first embodiment of the present invention. FIG. 5B is a graph showing the EDS of the aluminum alloy flat bar specimen after performing the quenching step according to the first embodiment of the present invention And EDS of the aluminum alloy flat bar specimen after the test.

5A, the composition of the aluminum alloy flat bar specimen of the present invention is 1.34 wt% of Mg, 4.42 wt% of Zn, 0.69 wt% of Cu, and 93.55 wt% of Al. This confirms that the composition ratio of the alloy is maintained as originally designed even after the extrusion step is carried out.

5b, the composition of the aluminum alloy flat bar specimen of the present invention still had a composition of Mg: 1.34% by weight, Zn: 4.42% by weight, Cu: 0.69% by weight, Al: 93.55% % ≪ / RTI > That is, even if the extrusion, hot stamping or quenching step is performed, the composition ratio of the initially designed alloy is maintained.

Meanwhile, the Al-Zn-Mg-Cu-based aluminum alloy is preheated in the step (1) before the hot stamping of the present invention is performed. The preheating temperature may preferably be 350 to 550 ° C , Lt; RTI ID = 0.0 > 500 C. < / RTI > In the case of preheating the aluminum alloy in the temperature range described above, it is possible to maintain the temperature that is easy to perform the hot stamping step by complementing the temperature loss occurring during the movement in the forging machine and the subsequent temperature loss due to the delay of the quenching before performing the hot stamping step.

If the preheating temperature is lower than 350 deg. C , the above-mentioned temperature loss can not be sufficiently compensated, so that it is difficult to perform the hot stamping step. If the preheating temperature is higher than 550 ° C , the process may be more complicated and the productivity may be lowered.

In addition, the preheating time in the preheating may be preferably within 2 hours, more preferably within 1 hour, and the heating speed during preheating may preferably be 5 to 50 ° C / min.

Next, (2) a step of extruding the preheated aluminum alloy to a flat bar will be described.

The aluminum alloy billet can be extruded into a rectangular cross-section through the step of directly flat-extruding the aluminum alloy, whereby a desired aluminum case can be easily manufactured.

The extrusion container to be used in the extrusion may be any shape and size as long as it can be made into a flat bar having a rectangular cross section after the extrusion step. Preferably, The diameter may be 10 to 1000 mm and the cross-sectional area may be 300 to 5000 mm ² . The extrusion speed may be 3 mm / sec or more.

2 schematically shows an extruded aluminum alloy flat bar according to an embodiment of the present invention. In order to extrude such a flat bar, the extrusion ratio representing the ratio of the cross-sectional area of the aluminum alloy before and after extrusion may be preferably 30 to 60, more preferably 35 to 55. When the extrusion ratio is within the above range, a flat bar having no cracks or the like on the surface can be obtained. If the extrusion ratio is less than 30, the extrudability may deteriorate. If the extrusion ratio exceeds 60, the extrusion load may increase and the surface of the flat bar may be cracked.

4A is an optical microscope image of an aluminum alloy flat bar after the extrusion step according to the first embodiment of the present invention. FIG. 4B is an optical micrograph of the aluminum alloy flat bar after performing the quenching step according to the first embodiment of the present invention. FIG. 4C is an optical microscope photograph of an aluminum alloy flat bar after performing the artificial aging heat treatment step according to Embodiment 1 of the present invention. FIG.

First, it can be seen from the optical microscope photograph of FIG. 4A that the microstructures of the flat bars after extrusion exhibit a typical structure of the extruded specimen. Also, ED and ND surface images show that the size of the grain is small and round at the corner, because the hot extrusion causes recrystallization but the crystal growth is not done properly due to the rapid cooling rate. On the other hand, at the center of the ED and ND surfaces, the relative size of the crystal grains was relatively large because the cooling rate was relatively slow after hot extrusion. Further, although the grain size varies slightly depending on the portion of the specimen, defects such as pinholes, shrinkage, cracks, pores and the like are not observed, so that it can be seen that excellent physical properties can be maintained even if the extrusion is proceeded.

Next, the microstructure of the flat bar after the hot stamping and quenching step was observed through the optical microscope photograph of FIG. 4B, and the microstructure in the flat part showed general forging texture and the shape of the crystal grain was formed long can confirm. In addition, it can be seen that, at the corners of the deformed portion, the structure is deformed by the bending of the specimen due to the stress, and defects such as pinholes, shrinkage, cracks and pores are not observed in the specimen as in the flat bar after the extrusion step. .

Lastly, optical microscope photographs of specimens of the aluminum alloy flat bar after the artificial aging heat treatment step of FIG. 4 (c) show no defects such as pinholes, shrinkage, cracks, pores, etc., have.

Next, (3) a step of hot-stamping the flat bar to a temperature equal to or higher than the solvus temperature of the alloy will be described.

Hot stamping is a kind of processing heat treatment technique that transforms a part into a hard tissue at the same time as forming a part in a mold. It is a technology that can improve the strength while processing a shape. The hot stamping step can be performed to obtain a strength that can be attained when a conventional high-strength steel forming process is used with a normal steel grade material and a small molding load.

Further, the hot stamping step may preferably proceed to 1) the heating of the plate material 2) the press processing of the die 2).

First, 1) The heating temperature for the heating of the sheet material is higher than the heating temperature of the aluminum alloy used. The heating temperature means a temperature at which the steel is dissolved in solid solution, and according to one preferred embodiment of the present invention, the solidus temperature of the aluminum alloy is in the range of 400 to 440 캜. That is, if hot stamping heating is performed at a temperature higher than the above-mentioned solubility temperature, the aluminum alloy of the present invention can be dissolved as a solid solution, so that subsequent processing can be performed.

Accordingly, the heating temperature during the hot stamping step may be 400 to 600 ° C, and the heating time may be 5 seconds to 1 hour. More preferably, the heating temperature may be 420 to 550 ° C, and the heating time may be 30 seconds to 30 minutes. If the heating temperature is less than 400 ° C or the heating time is less than 30 seconds, the aluminum alloy may not sufficiently dissolve in the solid solution, which makes it difficult to carry out the subsequent process and the target strength may not be achieved. If the heating temperature exceeds 600 DEG C or the heating time exceeds 1 hour, the strength may be lowered after hot stamping.

After the heating step is performed, press processing using 2) a mold can be performed. 6 is a photograph of a metal case forging die for hot stamping according to an embodiment of the present invention. The heated flat bar can be press-worked by using the forged metal mold as shown in the above drawings to perform hot stamping molding, thereby obtaining an aluminum case having a desired material, shape and strength. The press working can be performed under the conditions of a descending speed of the press of 100 to 700 mm / sec.

According to a preferred embodiment of the present invention, the hot stamping process may not include a solution process. Solution heat treatment refers to a process for heating the alloy to a temperature higher than the melting point of the solid solution and keeping it for a sufficient time and quenching it to prevent its precipitation. In the case of performing the heat treatment process of conventional aluminum alloy, The processing of the aluminum alloy was performed in such a manner that the solution process at the temperature was necessarily included and the temperature and time of the solution process were controlled to inhibit the expansion of the bubbles contained in the aluminum alloy produced or block the blister formation .

However, the present invention can perform the aluminum alloy process without including such a solution-forming process, thereby satisfying the ease of processing by reducing the excessive processing cost and the visibility, and at the same time, Can be manufactured. That is, the present invention can produce an aluminum case having excellent physical properties such as strength and hardness as in the case where the solution step is performed by a simple process that does not include a solutioning step, Has an increasing effect.

Next, (4) a step of quenching the hot-stamped flat bar will be described.

The quenching step has the effect of keeping the shape and characteristics of the high-temperature flat bar formed through the hot stamping step. Preferably, the quenching step is performed while the press mold is closed after hot stamping. This is because the inside of the mold is maintained at a high temperature immediately after the hot stamping molding, so that when the mold is immediately opened to perform cooling, the characteristics and shape of the material may be deformed.

Further, the quenching may preferably be performed with a fluid or water. Specifically, it may be carried out by quenching in liquid water or by using water in a spray state such as a fine droplet. Further, it may be cooled by using a fluid such as oil whose temperature is relatively higher than that of water.

Meanwhile, according to a preferred embodiment of the present invention, the quenching may be performed within 30 seconds after performing the hot stamping in the step (3), more preferably within 24 seconds, more preferably, 12 seconds, and most preferably within 3 seconds. When hot stamping in the step (3) is performed and quenching is performed within a short time in the above range, the tensile strength and elongation of the aluminum alloy are increased and defects such as pinholes, shrinkage, cracks and pores are not generated, Can be improved.

If quenching is performed in excess of 30 seconds after the hot stamping, defects such as pinholes, shrinkage, cracks, pores, etc. may occur and physical properties may be deteriorated.

A method of manufacturing a hot stamped aluminum case according to the present invention and an aluminum case produced by the method increase the tensile strength and elongation of an aluminum alloy and optimize processes for stable dimensions, post-processing and yield, Defects such as pinholes, shrinkage, cracks, pores and the like can be prevented from occurring and the physical properties can be increased.

Further, the process can be easily performed, thereby reducing the processing cost and time of the aluminum alloy material, and at the same time, the properties such as the strength and hardness of the alloy can be kept excellent.

Next, (5) an artificial aging step of heating the quenched flat bar will be described.

The aluminum flat bar subjected to the quenching step after the hot stamping may be further subjected to an artificial aging step for heating to increase the strength. The strength is improved through the artificial aging heat treatment, and the aluminum casing is improved in physical properties without defects such as pinholes, shrinkage and cracks.

Also, the artificial aging step is preferably performed by 1) a first heat treatment step performed at 100 to 110 ° C for 4 to 6 hours, and 2) a second heat treatment step for 6 to 8 hours at 170 to 180 ° C And the rate of temperature increase during the heat treatment step may be 0.5 to 50 ° C / min. When the artificial aging heat treatment is performed within the range of the heating temperature and the heating time and the temperature raising rate is maintained within the above range, defects such as pinholes, cracks and shrinkage are not found in the aluminum case, The incidence of blisters due to the expansion of the bubbles present in the aluminum alloy is significantly lowered, and excellent physical properties such as high strength and hardness can be exhibited.

If the temperature exceeds 110 ° C during the first heat treatment step, the temperature exceeds 180 ° C during the second heat treatment step, or the heat treatment time exceeds 6 hours and 8 hours, respectively, when the first and second heat treatments are performed , The compressed bubbles existing in the aluminum alloy expand, and the blister may increase. If the temperature of the first heat treatment step is less than 100 ° C, the temperature of the second heat treatment step is less than 170 ° C, or the heat treatment time of the first and second heat treatment is less than 4 hours and less than 6 hours, The physical properties such as strength and hardness may be deteriorated.

Furthermore, the hot stamped aluminum case obtained by the present invention is made of an Al-Zn-Mg-Cu alloy, and there is no limitation as long as it can be obtained through the above-described manufacturing process which does not include a solution-forming process . Preferably, however, the hot-stamping aluminum case obtained by the present invention is such that the Al-Zn-Mg-Cu alloy contains 1.0-2.2 wt% of Mg, 4.0-5.5 wt% of Zn, % And remaining Al and inevitable impurities, and an average Rockwell B hardness of 50 to 65 HRB.

Hereinafter, the description will be briefly described except for the content overlapping with the above description.

The Rockwell hardness refers to a hardness measured by a Rockwell hardness meter as a resistance against deformation, and preferably refers to a Rockwell hardness B measured by the Rockwell hardness scale B. [ The average Rockwell B hardness was measured for four specimens except for two specimens after cutting the artificially aged flat bar into six specimens. Specifically, the Rockwell B hardness is measured five times for each specimen, the maximum and minimum values are removed, and the average is taken to derive the average Rockwell B hardness value.

The average Rockwell B hardness of the hot stamped aluminum case obtained through the present invention is 50 to 65 HRB. In addition, the average Rockwell B hardness may preferably be 55 to 63 HRB, and more preferably 58 to 61 HRB. The aluminum case having the Rockwell B hardness value within the above range is resistant to deformation and can withstand the force or impact exerted from the outside, and can have excellent strength.

That is, through the present invention, it is possible to obtain an aluminum case having excellent Rockwell B hardness values as described above. In this case, since the solution case is not included, the hardness value is excellent and the surface has fewer defects such as cracks and voids And is excellent in processability. If the average Rockwell B hardness is less than 50, a problem that the aluminum case is easily deformed due to external force or impact may occur. In addition, if the average Rockwell B hardness exceeds 65 by the solution process, an aluminum case with excellent physical properties can be obtained, but more defects are found on the surface of the process, and the process is complicated and takes a long time. The problem of falling can occur.

Specifically, Table 3 shows Rockwell B hardness of the aluminum case according to various embodiments of the present invention, and the hot stamped aluminum case according to the present invention has an average Rockwell B hardness of 50 to 65 HRB. In addition, it can be seen that the average Rockwell B hardness value exhibits properties similar to those of the aluminum alloy materials of Comparative Examples 1 to 6 manufactured through the process including the solution-forming step. That is, it is possible to reduce the process time by a simpler process by carrying out the process without including the solution-forming step, and at the same time, obtain an aluminum case having properties similar to those in the case of performing the process including the solution- .

The aluminum case for hot stamping, which can be obtained through the present invention, can be used as a case for a mobile device, although it can be used without limitation if it is necessary to alleviate impact and the like. This is because the hot stamped aluminum case of the present invention can express the gloss and texture inherent to the metal and has excellent strength to easily protect the weak mobile device from impact.

As a result, the hot stamping aluminum case manufactured through the hot stamping process using the 7000 series aluminum alloy of the present invention does not include a solution process, and can express the gloss and texture inherent to the metal, The stamping process is performed to improve the processability, and the process can be performed stably. Thus, the yield is increased, the productivity is excellent, defects such as cracks and shrinkage are not generated, and the strength can be enhanced to have increased physical properties.

In addition, the aluminum case of the present invention can be utilized not only in cases where impact reduction is required but also as a case for a mobile device.

Example

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of a multipurpose safety glove and a method of manufacturing the same according to the present invention will be described in detail.

Example  One

7000 series aluminum alloy was designed to have a composition of 1.34% by weight of Mg, 4.42% by weight of Zn, 0.69% by weight of Cu and 93.55% by weight of Al. A cylindrical billet having a diameter of 5 inches (127 mm) cast according to the above alloy design was preheated at 470 DEG C for 1 hour from a billet preheating furnace, and then a hot extruded mold made of SKD61, 81 mm, Was extruded. The diameter of the container was 135 mm, the cross-sectional area was 14,314 mm 2, the cross-sectional area of the product was 308 mm 2, and the extrusion ratio was 46.5. Thereafter, a hot stamping process consisting of two steps of 1) heating of the sheet material and 2) press working by the die was performed. At this time, the plate material was heated at 470 캜 for 300 seconds, and hot stamping molding was performed by press processing using a die. Thereafter, the hot-stamped flat bar was immediately quenched in water within 3 seconds to perform the quenching step. The flat bars subjected to the hot stamping and quenching processes were subjected to a primary heat treatment at 105 ° C for 5 hours and a secondary heat treatment at 175 ° C for 7 hours to perform two stages of artificial aging treatment.

Example  2 to 18

A hot stamped aluminum case was prepared in the same manner as in Example 1, depending on the amount of Cu in the aluminum alloy, the time and temperature of the process, and the temperature in Table 1 below.

[Table 1]

Comparative Example

Comparative Example  One

A hot stamping aluminum case was manufactured in the same manner as in Example 1, except that the solution-casting process was carried out at 470 캜 for 20 minutes in the hot stamping process.

Comparative Example  2

The hot stamping process was carried out at 470 ° C for 20 minutes, followed by a primary heat treatment at 105 ° C for 5 hours, followed by a secondary heat treatment at 175 ° C for 3 hours, followed by a 2-step heated artificial aging treatment A hot stamped aluminum case was prepared in the same manner as in Example 1. The hot-

Comparative Example  3

In the hot stamping process, the solution was subjected to the solution treatment at 470 ° C. for 20 minutes, the first heat treatment at 105 ° C. for 5 hours, the second heat treatment at 175 ° C. for 5 hours, and the second heat aging treatment A hot stamped aluminum case was prepared in the same manner as in Example 1. The hot-

Comparative Example  4

During the hot stamping process, the solution was subjected to the solution treatment at 470 ° C. for 20 minutes and the first heat treatment at 105 ° C. for 5 hours, followed by the second heat treatment at 175 ° C. for 9 hours to carry out the second step heat aging treatment A hot stamped aluminum case was prepared in the same manner as in Example 1. The hot-

Comparative Example  5

During the hot stamping process, the solution was subjected to the solution treatment at 470 ° C. for 20 minutes, the first heat treatment at 105 ° C. for 5 hours, the second heat treatment at 175 ° C. for 11 hours, A hot stamped aluminum case was prepared in the same manner as in Example 1. The hot-

Comparative Example  6

6013-T6, a commercially available product manufactured by Samsung Electronics Co., Ltd., including a solution-forming process in the hot stamping process, was used.

[Table 2]

Table 2 shows the specifications of the reagents used in the experimental examples of the present invention.

Experimental Example  One. Optical microscope  Used observation

1) Flat bar specimens before hot stamping 2) Flat bar specimens after quenching after hot stamping 3) Microstructure of artificially aged flat bar specimens Respectively. First, the surface of each flat bar specimen was finely polished to 0.04 μm and etched using a Keller solution (75 mL distilled water, 20 mL nitric acid (HNO ₃ ), 3 mL hydrochloric acid (HCl), 2 mL hydrogen fluoride (HF) Observation was made using an optical microscope. In this case, the magnification of the optical microscope was observed at x50 to 1000.

In the case of the flat bar specimen after the hot stamping and the quenching step, mounting of the ED side was performed using a clip to observe the change of the microstructure of the specimen through hot stamping, Cold mounting was carried out because the specimen may deform even in a slight heat.

3A is a photograph of an aluminum alloy flat bar and a specimen after performing the extrusion step according to an embodiment of the present invention. FIG. 3B is a photograph of the aluminum alloy flat bar and specimen after the quenching step according to an embodiment of the present invention. FIG. 3c is a photograph of a specimen of an aluminum alloy flat bar after performing the artificial aging heat treatment step according to an embodiment of the present invention. FIG. When these specimens are observed through an optical microscope, as shown in FIG. 3B, the microstructures are observed by dividing the specimens into a plurality of specimens. Respectively.

Experimental Example  2. Energy dispersive X-ray spectrometer (EDS, energy dispersive  x-ray spectroscopy)

(EDS mapping) using FE-SEM (JEOL-6500F) 1) Flat bar specimens before hot stamping 2) Flat bar specimens after hot stamping Were independently measured. In this case, the beam exposure time was limited to 1 minute, and the magnification was measured at x2000.

Experimental Example  3. Rockwell  B Measurement of hardness

1) Flat bar specimens before performing hot stamping 2) Flat bar specimens after performing hot stamping and after quenching 3) Artificial aged flat bar specimens Rockwell B hardness was measured. The hardness of each flat bar was measured with the remaining specimens except for two specimens, which are the corner portions of the six specimens. Specifically, Rockwell B hardness was measured by measuring Rockwell B scale five times per one specimen, removing the maximum value and the minimum value, and averaging to measure Rockwell B hardness.

Experimental Example  4. Defect measurement of manufactured aluminum case surface

In this Experimental Example, defects on the surface of the aluminum case manufactured through the above Examples and Comparative Examples were measured. Defects such as pinholes, shrinkage, cracks, pores and the like were observed on the surface of the aluminum case. When 0 to 2 defects were observed,?, 3 to 5 defects were observed, 6 to 8 defects were found to be? X or more, respectively, and the results are shown in Table 3 below.

[Table 3]

As can be seen from Table 3, Examples 1 to 18 show that the average Rockwell B hardness was lower than that of Comparative Examples 1 to 6, in which solution casting was carried out even though hot stamping was performed without solvent solution, It has a similar value. In addition, an aluminum case excellent in physical properties without any occurrence of defects such as pinholes, shrinkage, cracks and voids on the surface of the aluminum case manufactured through the above examples can be obtained .

That is, the aluminum case manufactured through the present invention can achieve process easiness by reducing the process cost and time by performing the process without performing the solution process, and at the same time, Hardness, strength and the like similar to those of the case and fewer defects on the surface, so that an aluminum case having remarkably excellent physical properties can be obtained.

Claims (10)

(1) preheating an Al-Zn-Mg-Cu-based aluminum alloy;
(2) extruding the preheated aluminum alloy into a flat bar;
(3) hot-stamping the flat bar at a temperature equal to or higher than the solvus temperature of the alloy without any separate solution process;
(4) quenching the hot stamped flat bar; and
(5) An artificial aging step of heating the quenched flat bar.
The method according to claim 1,
The Al-Zn-Mg-Cu-based aluminum alloy in the step (1) comprises 1.0 to 2.2% by weight of Mg, 4.0 to 5.5% by weight of Zn, 0.1 to 0.9% by weight of Cu and the balance of Al and unavoidable impurities A method of manufacturing a hot stamped aluminum case.
The method according to claim 1,
Wherein the preheating temperature of step (1) is 350 to 550 占 폚.
The method according to claim 1,
Wherein the extrusion ratio of the cross-sectional area of the aluminum alloy before and after extrusion in the step (2) is 30 to 60.
The method according to claim 1,
Wherein the heating temperature during the hot stamping in the step (3) is 400 to 600 占 폚, and the heating time is 5 seconds to 1 hour.
The method according to claim 1,
Wherein the quenching in the step (4) is performed with a fluid or water.
The method according to claim 1,
Wherein the quenching in the step (4) is performed within 30 seconds after the step (3) is performed.
The method according to claim 1,
Wherein the quenching in the step (4) is performed within 3 seconds after the step (3).
The method according to claim 1,
The artificial aging in the step (5)
1) a first heat treatment step performed for 4 to 6 hours at a temperature range of 100 to 110 ° C; and
2) a second heat treatment step of performing a heat treatment in a range of 170 to 180 ° C for 6 to 8 hours, characterized in that the rate of temperature rise in each heat treatment step is 0.5 to 50 ° C / min Said method comprising the steps of:
Characterized in that it comprises 1.0 to 2.2% by weight of Mg, 4.0 to 5.5% by weight of Zn, 0.1 to 0.9% by weight of Cu and the balance of Al and unavoidable impurities with an average Rockwell B hardness of 50 to 65 HRB. case.

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