JP2017082281A - Small sized electronic device case, molding method thereof and aluminum alloy rolled laminate sheet material for small sized electronic device case - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small sized electronic device case capable of being molded by contraction processing at good efficiency and low cost and hardly generating molding defects.SOLUTION: An aluminum alloy rolled laminate sheet material is used for molding a small sized electronic device case by contraction molding, having 0.2% bearing force of 200 MPa or more and including a fibrous crystal structure extending in a direction orthogonal to a thickness direction.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a case of a small electronic device such as a tablet terminal, a portable communication terminal device, a notebook personal computer, a mobile phone, a portable music device, a digital camera, and a method for forming the case, and an aluminum alloy rolled plate used as a forming material for the case About.

Conventionally, as a case of a small electronic device, a case formed by cutting (entirely cutting out) a thick plate-like aluminum alloy extruded material is known (for example, see Patent Document 1 below).
The above case can be suitably used as a small electronic device case because it has excellent appearance, precision and strength.

  In general, drawing is also widely performed as means for forming a product having a predetermined shape from a metal plate such as an aluminum alloy plate.

JP 2012-246555 A

  However, in the case of a small electronic device case formed by cutting, since it takes a long time to cut the material, the manufacturing efficiency is low, and a large amount of cutting waste is generated along with the processing, and this is recovered. However, since a lot of energy is required, there is a problem that the cost becomes high as a result.

  On the other hand, in the case of drawing, since molding is performed in a short time, the manufacturing efficiency is excellent, and there is no generation of debris accompanying the processing, so that it can be manufactured at low cost. However, the form of the small electronic device case is generally provided with a bottom wall that is substantially rectangular when viewed from above and a side wall that rises from the periphery of the bottom wall. If the case having such a configuration is to be molded by drawing, there is a high possibility that the corner portion of the side wall is cracked, resulting in molding failure.

  An object of the present invention is to provide a small electronic device case that can be molded efficiently and at low cost by drawing, and is less prone to molding defects.

  In order to achieve the above object, the present invention comprises the following aspects.

1) An aluminum alloy rolled sheet for forming a small electronic device case by drawing, having a 0.2% proof stress of 200 MPa or more and having a fibrous crystal structure extending in a direction perpendicular to the thickness direction Aluminum alloy rolled sheet for small electronic equipment cases.

2) Mn: 0.2 to 0.7% by mass, Mg: 2.0 to 5.0% by mass, Al—Mn—Mg based alloy composed of the balance Al and inevitable impurities, Si: 0.2 to 0.8 % By mass, Mg: 0.4 to 1.2% by mass, Al-Si-Mg alloy composed of the balance Al and inevitable impurities, and Zn: 4.0 to 6.5% by mass, Mg: 0.5 to 3 The aluminum alloy rolled sheet for small electronic device cases according to the above 1), which is made of any one aluminum alloy among Al-Zn-Mg alloys composed of 0.0 mass%, the balance Al and inevitable impurities.

3) The aluminum alloy rolled sheet material for small electronic device cases according to 1) or 2), wherein the thickness is 0.5 to 3.5 mm.

4) A small electronic device case formed by drawing an aluminum alloy rolled sheet for a small electronic device case according to any one of 1) to 3) above.

5) A bottom wall and a side wall rising from the periphery of the bottom wall, the height of the side wall is 0.5 to 25 mm, and the angle of the side wall with respect to the bottom wall is 90 to 170 ° 4) Small electronic equipment case.

6) A method for forming a small electronic device case, wherein the aluminum alloy rolled sheet for the small electronic device case according to any one of 1) to 3) is drawn.

  According to the aluminum alloy rolled sheet for small electronic equipment case of 1) above, since 0.2% proof stress is 200 MPa or more, the strength of the desired case is ensured, and the thickness direction is orthogonal to Since it has a fibrous crystal structure that extends in the direction of bending, the strength of the plate material against bending is increased, and the formability by drawing is improved, so that the side wall of the molded case is wrinkled or the side wall Cracks are not generated at the corners of the mold and the occurrence of molding defects is suppressed.

  According to the aluminum alloy rolled sheet for small electronic equipment case of 2), any one of Al—Mn—Mg based alloy, Al—Si—Mg based alloy, and Al—Zn—Mg based alloy having the above-mentioned respective compositions. Since it is made of two aluminum alloys, forming by drawing is performed well, and a case with high precision and strength and excellent appearance can be obtained.

According to the aluminum alloy rolled sheet for small electronic device case 3) above, the thickness is 0.5 to 3.5 mm, so the following problems are avoided.
That is, when the thickness of the aluminum alloy rolled plate material is less than 0.5 mm, the strength of the final product is insufficient. On the other hand, if the thickness of the aluminum alloy rolled sheet material exceeds 3.5 mm, the radius (curvature radius) of the bent portion and the corner portion becomes too large.

  According to the small electronic device case of 4) above, the aluminum alloy rolled sheet material is formed satisfactorily by drawing, and a case with high precision and strength and a beautiful appearance can be obtained.

According to the small electronic device case of 5), the height of the side wall is 0.5 to 25 mm, and the angle of the side wall with respect to the bottom wall is 90 to 170 °, so the following problems are avoided.
That is, if the height of the side wall is less than 0.5 mm, the number of cutting parts increases in the subsequent process. On the other hand, if the height of the side wall exceeds 25 mm, the thickness of the small electronic device increases, which is not preferable.
Further, when the angle of the side wall with respect to the bottom wall is less than 90 °, that is, when the side wall is inclined inward, wrinkles are generated at the corner portion, and the processing becomes difficult. On the other hand, when the angle of the side wall with respect to the bottom wall exceeds 170 °, the depth of the case becomes shallow, and the number of components accommodated in the small electronic device decreases.

  According to the method for molding a small electronic device case of 6), a small electronic device case having high precision and strength and exhibiting a beautiful appearance can be efficiently formed at low cost by drawing.

It is a vertical sectional view which shows sequentially the process of drawing the aluminum alloy rolled sheet material for small electronic device cases by this invention, and shape | molding a small electronic device case. It is a perspective view of the small electronic device case by this invention. It is a perspective view for showing the section direction at the time of bending the aluminum alloy rolled sheet material and observing the fibrous crystal structure of the section. It is a microscope picture of the cross section (the cross-sectional direction with respect to a rolling direction: 90 degrees) of the bending material (inner round: 0 mm) of the aluminum alloy rolled sheet material. It is a microscope picture of the cross section (cross-sectional direction with respect to a rolling direction: 90 degrees) of the bending material (inner radius: 0.4 mm) of the aluminum alloy rolled sheet material. It is a microscope picture of the cross section (cross-sectional direction: 0 degree with respect to the rolling direction) of the bending material (inner round: 0 mm) of the aluminum alloy rolled sheet material. It is a microscope picture of the cross section (cross-sectional direction: 0 degree with respect to the rolling direction) of the bending material (inner radius: 0.4 mm) of the aluminum alloy rolled sheet material.

  Embodiments of the present invention will be described below with reference to FIGS.

The aluminum alloy rolled sheet material (1) for a small electronic device case according to the present invention has a 0.2% proof stress of 200 MPa or more, preferably 250 MPa or more, more preferably 300 MPa or more. Thereby, the intensity | strength of a desired case is obtained. In addition, as the aluminum alloy rolled sheet (2), one having an elongation at break of 5% or more and 20% or less is suitably used. Thereby, the moldability of the drawing process is improved. Here, “0.2% proof stress” and “breaking elongation” are based on a tensile test parallel to the rolling direction using No. 5 test piece defined in JIS Z2241-2011.
The aluminum alloy rolled sheet (1) has a fibrous crystal structure extending in a direction orthogonal to the thickness direction.
The fibrous crystal structure is formed by subjecting a homogenized aluminum alloy cast soul to heat treatment under a predetermined condition after hot rolling, and then cold rolling. The said heat processing is performed by hold | maintaining at 200-400 degreeC for 1 hour or more. By the heat treatment, Mg ₂ Si can be finely and uniformly precipitated, and processing strain existing in the rolled material can be reduced. It is possible to obtain a high-strength rolled aluminum alloy sheet within a range that does not impair subsequent workability by work hardening by subsequent cold working.
The conditions for the homogenization treatment of the aluminum alloy casting soul are not particularly limited, and it is preferably performed at 500 ° C. or more for 2 hours or more according to a conventional method.
In hot rolling, the same effect as quenching is obtained by a temperature drop during rolling at a predetermined temperature condition in an arbitrary pass process. Accordingly, the material temperature before the pass needs to be a temperature at which Mg and Si can be kept in a solid solution state, and is set to 350 to 440 ° C. In order to set the pass rising temperature in the temperature range of 200 to 400 ° C., forced cooling such as high pressure shower water cooling may be performed immediately after hot rolling. Further, in order to obtain a quenching effect, the cooling rate between passes is 50 ° C./min or more, the pass rising temperature is 250 to 340 ° C., the pass rolling rate is 50 m / min or more, and the ascending plate thickness is 10 mm or less. .
In cold rolling, the rolling reduction is 30% or more in order to obtain a predetermined strength by work hardening. A preferable rolling reduction is 50% or more.
Furthermore, the cold-rolled alloy plate can be finally annealed at a temperature of 130 to 150 ° C., if necessary. By performing the heat treatment at a low temperature, the strength can be further improved by age hardening, and the elongation can be improved. It also has the effect of stabilizing mechanical properties.
As the aluminum alloy rolled sheet (1), one made of any of the following aluminum alloys is preferably used.
i) Al—Mn—Mg-based alloy containing Mn: 0.2 to 0.7% by mass, Mg: 2.0 to 5.0% by mass, the balance being Al and inevitable impurities ii) Si: 0.2 -0.8 mass%, Mg: 0.4-1.2 mass%, Al-Si-Mg-based alloy iii consisting of the balance Al and inevitable impurities iii) Zn: 4.0-6.5 mass%, Mg: Al-Zn-Mg-based alloy containing 0.5 to 3.0% by mass, the balance being Al and inevitable impurities As the alloy of the above i), Si: 0.4% by mass or less, Mn: 0. 4-1.0 mass%, Mg: 4.0-4.9 mass%, Fe: 0.4 mass% or less, Cr: 0.05-0.25 mass%, Zn: 0.25 mass% or less The aluminum alloy which contains and consists of remainder Al and an unavoidable impurity is mentioned.
As the alloy of ii), Si: 0.2 to 0.6 mass%, Mg: 0.45 to 0.9 mass%, Fe: 0.35 mass% or less, Cr: 0.1 mass% or less, Zn: An aluminum alloy containing 0.1% by mass or less and composed of the balance Al and inevitable impurities may be mentioned.
As the alloy of the above iii), Si: 0.4 mass% or less, Mg: 2.1-2.9 mass%, Fe: 0.5 mass% or less, Cu: 1.2-2.0 mass%, Examples include an aluminum alloy containing Mn: 0.3% by mass or less, Cr: 0.18 to 0.28% by mass, Zn: 5.1 to 6.1% by mass, and the balance Al and inevitable impurities.
Among these, Si: 0.2-0.6 mass%, Mg: 0.45-0.9 mass%, Fe: 0.35 mass% or less, Cr: 0.1 mass% or less, Zn: An aluminum alloy rolled sheet material (1) made of an aluminum alloy containing 0.1% by mass or less and the balance Al and inevitable impurities is suitable as a molding material for a small electronic device case.
Further, the thickness of the aluminum alloy rolled sheet (1) to be used is appropriately set according to the molding conditions, the size of the case as a molded product, etc., but is preferably 0.5 to 3.5 mm, more preferably 0. .8 to 1.2 mm.

FIG. 1 shows a process of forming a small electronic device case by drawing the aluminum alloy rolled sheet (1).
First, an approximately square-shaped aluminum alloy rolled sheet material (1) cut to a predetermined dimension is set on the upper surface of a fixed female mold (die) (2) on the lower side of the mold (see FIG. 1 (a)). A lubricant made of, for example, a silicone-based lubricant, mineral oil, or synthetic petroleum-based lubricant is applied to at least the lower surface of the aluminum alloy rolled sheet (1) that is at the outer side of the case.
When the movable male die (punch) (3) on the upper side of the die is lowered, the portion of the aluminum alloy rolled plate material (1) excluding the peripheral edge is pressed downward at the tip of the male die (3). As a result, the straight portion of the peripheral edge is bent upward, and the corner portion of the peripheral edge is drawn.
Thus, a small electronic device case (10) is obtained.

FIG. 2 shows a small electronic device case (10). This case (10) is formed by subjecting a molded product obtained by drawing the aluminum alloy rolled sheet (1) to a partial cutting process and finish molding, and then anodizing the surface. .
The small electronic device case (10) includes a substantially rectangular bottom wall (11) and a side wall (12) rising from the periphery of the bottom wall (11).
The height of the side wall (12) (in other words, the molding height) is 0.5 to 25 mm, preferably 1 to 15 mm, and more preferably 2 to 10 mm.
The angle of the side wall (12) with respect to the bottom wall (21) is 90 to 170 ° (the one shown is about 90 °), preferably 90 to 145 °, more preferably 90 to 120 °.
The corners (12a) of the side walls (12) are also rounded at the boundary between the bottom wall (11) and the side walls (12). In these round portions, the fibrous crystal structure extends along the round.

The fibrous crystal structure can be confirmed by observing the cross section of the aluminum alloy rolled sheet (1) or the case (10) formed by drawing the aluminum alloy rolled sheet (1) using a polarizing microscope.
Preferably, the fibrous crystal structure is preferably observed even in a cross section cut in an arbitrary direction such as 0 °, 90 °, 45 °, and 135 ° with respect to the rolling direction of the aluminum alloy rolled sheet. The same can be observed in the bent portion and the corner portion.
Specifically, for example, as shown in FIGS. 3 (a) and 3 (b), a rolled aluminum alloy sheet (1) having a thickness of 0.25 mm is bent so that the inner radius is 0 mm or 0.4 mm. For these bending materials, a cross section cut in a direction (Y) of 90 ° (perpendicular) or 0 ° (parallel) with respect to the rolling direction (X) is observed with a polarizing microscope. Then, as can be seen from the micrographs of FIGS. 4 to 7, the inner radius is 0 mm, the cross-sectional direction with respect to the rolling direction: 90 ° (FIG. 4), the inner radius is 0.4 mm, and the cross-sectional direction with respect to the rolling direction is 90 ° (FIG. 5). ), Inner radius: 0 mm, sectional direction with respect to rolling direction: 0 ° (FIG. 6), inner radius: 0.4 mm, sectional direction with respect to rolling direction: 0 ° (FIG. 7) The structure extends in a direction orthogonal to the thickness direction of the plate material so as to be along the radius.

  Next, specific examples of the present invention will be described. However, the present invention is not limited to these examples.

<Example 1>
Si: 0.2-0.6 mass%, Mg: 0.45-0.9 mass%, Fe: 0.35 mass% or less, Cr: 0.1 mass% or less, Zn: 0.1 mass% or less The aluminum alloy casting soul containing the balance Al and inevitable impurities was homogenized at 580 ° C. for 10 hours, then face-cut, preheated at 500 ° C., and hot rolling was started. The final pass start temperature of hot rolling was 400 ° C., and after the pass, cooling was performed at a rate of 80 ° C./min. Thereafter, heat treatment was performed at 240 ° C. for 4 hours. Thereafter, cold rolling was performed at a reduction rate of 86%. Thus, a 1 mm-thick aluminum alloy rolled sheet material having a 0.2% proof stress of 310 MPa and a breaking elongation of 7% was obtained.
When the cross section of the plate was observed with an optical microscope and a deflecting lens, a fibrous crystal structure extending in a direction perpendicular to the thickness direction was observed.
This aluminum alloy rolled sheet was cut into a substantially rectangular shape having a length of 150 mm, a width of 82 mm, and a corner radius of 14.5 mm, thereby producing the molding material of Example 1.

<Example 2>
Si: 0.4 mass% or less, Mn: 0.4-1.0 mass%, Mg: 4.0-4.9 mass%, Fe: 0.4 mass% or less, Cr: 0.05-0. Aluminum alloy casting soul containing 25% by mass and Zn: 0.25% by mass or less and comprising the balance Al and inevitable impurities is homogenized at 580 ° C. for 10 hours and then face-cut, and preheated at 500 ° C. And hot rolling was started. The final pass start temperature of hot rolling was 400 ° C., and after the pass, cooling was performed at a rate of 80 ° C./min. Thereafter, heat treatment was performed at 240 ° C. for 4 hours. Then, after cold rolling at a reduction rate of 79%, final annealing was performed at 130 ° C. for 4 hours. Thus, an aluminum alloy rolled sheet material having a thickness of 1.5 mm having a 0.2% proof stress of 210 MPa and a breaking elongation of 7% was obtained.
When the cross section of the plate was observed with an optical microscope and a deflecting lens, a fibrous crystal structure extending in a direction perpendicular to the thickness direction was observed.
The aluminum alloy rolled sheet was cut into a substantially rectangular shape having a length of 150 mm, a width of 82 mm, and a corner radius of 14.5 mm to produce a molding material of Example 2.

<Example 3>
Si: 0.4% by mass or less, Mg: 2.1-2.9% by mass, Fe: 0.5% by mass or less, Cu: 1.2-2.0% by mass, Mn: 0.3% by mass or less , Cr: 0.18 to 0.28 mass%, Zn: 5.1 to 6.1 mass%, the aluminum alloy ingot consisting of the balance Al and inevitable impurities, the same process and conditions as in Example 2 Was rolled to obtain an aluminum alloy rolled sheet having a thickness of 1.5 mm and a 0.2% proof stress of 550 MPa and a breaking elongation of 9%.
When the cross section of the plate was observed with an optical microscope and a deflecting lens, a fibrous crystal structure extending in a direction perpendicular to the thickness direction was observed.
This aluminum alloy rolled laminated sheet was cut into a substantially rectangular shape having a length of 150 mm, a width of 82 mm, and a corner radius of 14.5 mm, thereby producing a molding material of Example 3.

<Comparative Example 1>
Si: 0.4 mass% or less, Mn: 0.4-1.0 mass%, Mg: 4.0-4.9 mass%, Fe: 0.4 mass% or less, Cr: 0.05-0. Extruded aluminum alloy with a thickness of 2 mm, containing 25% by mass, Zn: 0.25% by mass or less, consisting of an aluminum alloy consisting of the balance Al and inevitable impurities, 0.2% proof stress 230 MPa, and breaking elongation 14% Board material was prepared. The plate material is extruded and does not have a fibrous crystal structure extending in a direction orthogonal to the thickness direction.
The aluminum alloy extruded plate was cut into a substantially rectangular shape having a length of 150 mm, a width of 82 mm, and a corner radius of 14.5 mm, thereby producing a molding material of Comparative Example 1.

<Comparative example 2>
Si: 0.4% by mass or less, Mg: 2.1-2.9% by mass, Fe: 0.5% by mass or less, Cu: 1.2-2.0% by mass, Mn: 0.3% by mass or less , Cr: 0.18 to 0.28 mass%, Zn: 5.1 to 6.1 mass%, consisting of an aluminum alloy consisting of the balance Al and inevitable impurities, 0.2% proof stress of 510 MPa, elongation at break An aluminum alloy extruded plate material having a thickness of 1.5 mm and 11% was prepared. The plate material is extruded and does not have a fibrous crystal structure extending in a direction orthogonal to the thickness direction.
The aluminum alloy extruded plate was cut into a substantially rectangular shape having a length of 150 mm, a width of 82 mm, and a corner radius of 14.5 mm, thereby producing a molding material of Comparative Example 2.

<Comparative Example 3>
Si: 0.2-0.6 mass%, Mg: 0.45-0.9 mass%, Fe: 0.35 mass% or less, Cr: 0.1 mass% or less, Zn: 0.1 mass% or less The aluminum alloy casting soul containing the balance Al and inevitable impurities was homogenized at 580 ° C. for 10 hours, then face-cut, preheated at 500 ° C., and hot rolling was started. The final pass start temperature of hot rolling was 400 ° C., and after the pass, cooling was performed at a rate of 80 ° C./min. Thereafter, heat treatment was performed at 240 ° C. for 4 hours. Then, after cold rolling at a reduction rate of 57%, heat treatment was performed at 250 ° C. for 2 hours. Thus, a rolled aluminum alloy sheet having a thickness of 3 mm and a 0.2% proof stress of 150 MPa and a breaking elongation of 14% was obtained. The plate material has been subjected to natural aging treatment after cold rolling, and does not have a fibrous crystal structure extending in a direction perpendicular to the thickness direction.
The aluminum alloy rolled sheet was cut into a substantially rectangular shape having a length of 150 mm, a width of 82 mm, and a corner radius of 14.5 mm to produce a molding material of Comparative Example 3.

<Comparative example 4>
Si: 0.2-0.6 mass%, Mg: 0.45-0.9 mass%, Fe: 0.35 mass% or less, Cr: 0.1 mass% or less, Zn: 0.1 mass% or less An aluminum alloy rolled sheet material having a thickness of 2 mm, which is made of an aluminum alloy containing the balance Al and inevitable impurities, having a 0.2% proof stress of 145 MPa and a breaking elongation of 12%, was prepared. The plate material is obtained by cold rolling (33% reduction) of the extruded plate material, and does not have a fibrous crystal structure extending in a direction orthogonal to the thickness direction.
This aluminum alloy rolled sheet was cut into a substantially rectangular shape having a length of 150 mm, a width of 82 mm, and a corner radius of 14.5 mm, thereby producing a molding material of Comparative Example 4.

<Molding of small electronic equipment case>
The molding materials of Examples 1 to 3 and Comparative Examples 1 to 4 were coated with mineral oil as a lubricant on both sides, and then drawn using the drawing apparatus shown in FIG. A small electronic device case having a width of 70.5 mm, a side wall height (molding height) of 7 mm, and a side wall corner portion R of 2 mm was molded. The angle of the side wall with respect to the bottom wall was 90 °.
As a result of visual observation of each molded case, no wrinkles or cracks occurred in the corner portions of the side walls of the molding materials of Examples 1 to 3.
On the other hand, about the case which consists of a molding material of Comparative Examples 1-4, the wrinkles and the crack had arisen in the corner part of the side wall.

  The present invention can be suitably used for forming a case of a small electronic device such as a tablet terminal, a mobile communication terminal device, a notebook computer, a mobile phone, a portable music device, a digital camera or the like.

(1): Aluminum alloy rolled sheet
(2): Fixed female type
(3): Movable male type
(10): Small electronic equipment case
(11): Bottom wall
(12): Side wall
(12a): Corner part (side wall)

Claims (6)

  An aluminum alloy rolled sheet for forming a small electronic device case by drawing, has a 0.2% proof stress of 200 MPa or more, and has a fibrous crystal structure extending in a direction perpendicular to the thickness direction. Aluminum rolled sheet for small electronic equipment cases.   Al—Mn—Mg-based alloy containing Mn: 0.2 to 0.7% by mass, Mg: 2.0 to 5.0% by mass, the balance Al and inevitable impurities, Si: 0.2 to 0. 8% by mass, Mg: 0.4-1.2% by mass, Al—Si—Mg-based alloy consisting of the balance Al and inevitable impurities, and Zn: 4.0-6.5% by mass, Mg: 0 The aluminum alloy rolled for small electronic device case according to claim 1, which is made of any one aluminum alloy of Al-Zn-Mg based alloy containing 0.5 to 3.0% by mass and remaining Al and inevitable impurities. Board material.   The aluminum alloy rolled sheet material for a small electronic device case according to claim 1 or 2, wherein the thickness is 0.5 to 3.5 mm.   The small electronic device case formed by drawing the aluminum alloy rolled sheet material for small electronic device cases as described in any one of Claims 1-3.   The bottom wall and a side wall rising from the periphery of the bottom wall are provided, the height of the side wall is 0.5 to 25 mm, and the angle of the side wall with respect to the bottom wall is 90 to 170 °. Small electronic device case.   The shaping | molding method of the small electronic device case which draws the aluminum alloy rolled sheet material for small electronic device cases as described in any one of Claims 1-3.