US20100037997A1

US20100037997A1 - Aluminum alloys for display frames

Info

Publication number: US20100037997A1
Application number: US12/190,429
Authority: US
Inventors: Leighton M. Cooper; Phillip A. Hollinshead; Jason Chen
Original assignee: Alcoa Inc
Current assignee: Howmet Aerospace Inc
Priority date: 2008-08-12
Filing date: 2008-08-12
Publication date: 2010-02-18
Also published as: WO2010019591A1; TW201012943A

Abstract

Described is a method for forming an internal frame configured to receive a flat screen display. Aggressive partial annealing is applied to a hard temper 5182 aluminum alloy material having magnesium content greater than or equal to 3.0 wt. %. The material is partial annealed to an extent that the hard temper aluminum alloy is substantially softened with respect to its initial hardened temper while not exceeding the point where recrystallization occurs. An internal frame for a flat screen display is formed from the partial annealed aluminum alloy.

Description

This application is a continuation-in-part of U.S. patent application Ser. No. 11/411,242 filed Apr. 26, 2006, the entire disclosure of which is incorporated herein by reference. This application includes material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent disclosure, as it appears in the Patent and Trademark Office files or records, but otherwise reserves all copyright rights whatsoever.

FIELD OF THE INVENTION

The present invention relates in general to the field of frames for computer and video display screens, and in particular to novel display screen frames comprising particular aluminum alloys and/or tempers.

BACKGROUND OF THE INVENTION

Flat screen video displays, such as LCD monitors, plasma televisions, and the like, have internal frames which provide a structural support for components of the display. Such frames further provide a degree of protection for components of the display such as the relatively fragile display panel, e.g., an LCD panel. These frames are typically formed from stainless steel. While stainless steel provides an acceptable combination of formability and strength, stainless steel is relatively expensive and heavy (high density).
Aluminum alloys have been suggested for use in LCD monitor frames. Several readily available aluminum alloys have seemingly appropriate properties for such applications. These alloys include, e.g., 6xxx (particularly 6061-T4 and -T6), 5182, and 5052 alloys. However, such aluminum alloys do not provide an adequate solution. In particular, some of these materials crack during forming due to insufficent formability. Others distort, due to inadequate strength, in a drop test.

OBJECTS AND SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide an improved video display frame which overcomes one or more limitations of the prior art.
It is a further object of the invention to provide an LCD display frame which is less costly to manufacture.
It is a further object of the invention to provide an LCD display frame which performs comparably to that of stainless steel, but which provides advantages in terms of cost, availability, reduced weight, and/or mechanical or electrical properties.
In one embodiment, the invention provides a method for forming an internal frame configured to receive a flat screen display. Aggressive partial annealing is applied to a hard temper 5182 aluminum alloy material having magnesium content greater than or equal to 3.0 wt. %. The material is partial annealed to an extent that the hard temper aluminum alloy is substantially softened with respect to its initial hardened temper while not exceeding the point where recrystallization occurs. An internal frame for a flat screen display is formed from the partial annealed aluminum alloy.
In an alternative embodiment, a sheet of 5182 aluminum alloy material is annealed to a fully soft O-temper condition. The sheet is then cold rolled to achieve thickness reduction in the range 20 to 30%. An internal frame for a flat screen display is formed from the annealed and cold rolled sheet material.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features, and advantages of the invention will be apparent from the following more particular description of preferred embodiments as illustrated in the accompanying drawings, in which reference characters refer to the same parts throughout the various views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating principles of the invention.

FIG. 1 is a graphical illustration of elongation values vs. TYS (MPa) for 1xxx, 3xxx, and 5xxx alloys.

FIG. 2 shows a chart illustrating change in TYS and elongation of a hard temper of 0.23 mm 5182 alloy annealed at 246° C. (475° F.).

FIG. 3 shows a perspective view illustrating a display including an aluminum alloy frame in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In an embodiment of the invention, a display frame is formed from a 5182 aluminum alloy as defined in the Aluminum Association's Aluminum Standards and Data book. Series 6xxx alloys are very difficult to produce in thin sheets due to distortion during quenching. Various tempers of 5052 (for example, H32) do not have adequate strength to resist distortion during drop testing. Hardened tempers of 5182 (for example, H39) do not have sufficient formability to endure the rigors of forming the parts.
However, aggressive partial annealing of hard tempers (e.g., H18 or H19) of high magnesium 5182 alloys provides a material that has a desirable combination of formability and strength for internal LCD monitor frames. Recrystallization should not be allowed to occur during the partial annealing treatment, otherwise the strength would become too low for the application. The extent of the partial annealing treatment should be sufficient to substantially soften the material from the initial hardened temper, while not causing recrystallization to occur. The softened temper imparts good formability to the sheet, and the high magnesium content imparts improved strength through rapid work hardening during forming of the part, and possibly also due to the distortion occurring during drop testing of the finished assembly.
FIG. 1 shows elongation values vs. tensile yield strength (MPa) for 1xxx, 3xxx, and 5xxx alloys in the Aluminum Standards and Data Book for which elongation values for 1.6mm thick specimens were given. It is observed that only alloys and tempers containing ≧3.0 wt. % magnesium generally can obtain attractive combinations of high yield strength (>200 MPa) and high ductility (elongation >10%). Even within the small group of high Mg alloys highlighted within the box in the plot of FIG. 1, the compromise between elongation and yield strength can be seen. An example of a hard temper of 5182 that had been aggressively partial annealed in accordance with this invention is also shown within the box. The TYS-elongation combination of this particular 5182 sample does not appear particularly impressive relative to many of the high Mg alloys within the box, but it should be noted that the measurement of elongation increases with sample thickness, and the 5182 in this case was at 0.23 mm compared to 1.59 mm for all the other samples.
Another potential method for achieving a desirable combination of TYS and elongation in 5182 is to anneal a sheet of 5182 aluminum alloy material to the fully soft O-temper condition and then cold roll the sheet to achieve thickness reduction in the range 20 to 30%. As an example, 5182 cold rolled to 26% thickness reduction has been found to achieve yield strength and elongation, when tested in the longitudinal direction, of 282 MPa (41.0 ksi) and 10.5%, respectively. A further possibility is to use a slightly hardened temper as the starting material, e.g. HX2, and cold roll that sheet a small amount in order to achieve an attractive combination of TYS and elongation.
An aggressive partial anneal of a hard temper of 5182 has been found to provide a very attractive combination of strength (TYS) and ductility (elongation) suitable for the production of items such as the internal frames for LCD displays.
Tensile tests were conducted on sheet samples of 0.23 mm thick hard temper 5182 aluminum alloy material before and after annealing for various times at 246° C. (475° F.). The non-annealed material had high TYS, but elongation was inadequate (<8%) for forming LCD monitor frames. FIG. 2 shows change in TYS and elongation of a hard temper of 0.23 mm 5182 alloy annealed at 246° C. (475° F.).
As can be seen from FIG. 2, after annealing for 0.5 or 1.0 hours, elongation improves to >12% and TYS is still very attractive (>250 MPa). Microstructural examination revealed that recrystallization was just beginning in the sample annealed for 1 hour. After annealing for 2 hours, the sample was observed to have about 3% recrystallization. Elongation had improved to over 13%, but TYS already had dropped to a level considered unattractive (>250 MPa). It was clear, therefore, that to retain attractive levels of TYS, recrystallization in even very low quantities could not be tolerated.
FIG. 3 shows a display including an aluminum alloy frame in accordance with an embodiment of the invention. An interior frame 301 receives and supports a display panel 303. The framed display panel 303, in turn, is received by an outer frame 305. As will be apparent to those of skill in the art, the display panel 303 may be any flat screen display type, including, e.g., LCD, TFT, plasma, DLP, or the like.
The material described herein may be manufactured using a conventional rolling mill or via the well-known micro mill process. The micro mill process is described in U.S. Pat. Nos. 5,470,405, 5,514,228, 5,356,495, 5,363,902, 5,515,908, 5,564,491, 5,496,423, 5,655,593, 5,894,879, 5,772,799, 5,772,802, 6,045,632, 5,862,582, 5,742,993, 5,769,972, 6,102,102, 6,391,127, 6,063,215, 6,044,896, 6,623,797, 6,082,659, D-433,206, 6,135,199, 6,672,368 and 7,182,825, which are incorporated herein by reference.
While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.
The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

Claims

1. A method for forming an internal frame configured to receive a flat screen display, comprising:

aggressively partial annealing a hard temper 5182 aluminum alloy material having magnesium content greater than or equal to 3.0 wt. %, said aluminum alloy material having an initial hardened temper prior to said step of aggressively partial annealing, said step of aggressively partial annealing comprising partial annealing to an extent that said hard temper aluminum alloy is substantially softened with respect to said initial hardened temper while not exceeding the point where recrystallization occurs; and,

forming an internal frame for a flat screen display from said partial annealed aluminum alloy.

2. The method for forming an internal frame configured to receive a flat screen display according to claim 1, wherein said hard temper 5182 aluminum alloy comprises an aluminum alloy with an H18 temper.

3. The method for forming an internal frame configured to receive a flat screen display according to claim 1, wherein said hard temper 5182 aluminum alloy comprises an aluminum alloy with an H19 temper.

4. The method for forming an internal frame configured to receive a flat screen display according to claim 1, wherein said hard temper 5182 aluminum alloy comprises an aluminum alloy with an H2X temper.

5. The method for forming an internal frame configured to receive a flat screen display according to claim 1, wherein said hard temper 5182 aluminum alloy comprises an aluminum alloy with a temper at least as hard as H18.

6. The method for forming an internal frame configured to receive a flat screen display according to claim 1, wherein said step of aggressively partial annealing results in an alloy having a yield strength greater than 200 MPa and elongation greater than 10%.

7. The method for forming an internal frame configured to receive a flat screen display according to claim 1, further comprising: forming said partial annealed aluminum alloy into a sheet prior to forming said internal frame.

8. A method for forming a flat screen display, comprising:

forming an internal frame for a flat screen display from a hard temper 5182 aluminum alloy material having magnesium content greater than or equal to 3.0 wt. %, said 5182 aluminum alloy having been aggressively partial annealed from an initial hardened temper such that the material is substantially softened while not exceeding the point where recrystallization occurs;

inserting a display panel into said internal frame;

inserting said internal frame into an external frame.

9. The method for forming a flat screen display according to claim 1, wherein said hard temper 5182 aluminum alloy comprises an aluminum alloy with an H18 temper.

10. The method for forming a flat screen display according to claim 1, wherein said hard temper 5182 aluminum alloy comprises an aluminum alloy with an H19 temper.

11. The method for forming a flat screen display according to claim 1, wherein said hard temper 5182 aluminum alloy comprises an aluminum alloy with an H2x temper.

12. The method for forming a flat screen display according to claim 1, wherein said hard temper 5182 aluminum alloy comprises an aluminum alloy with a temper at least as hard as H18.

13. The method for forming an internal frame configured to receive a flat screen display according to claim 1, wherein said step of aggressively partial annealing results in an alloy having a yield strength greater than 200 MPa and elongation greater than 10%.

14. A method for forming an internal frame configured to receive a flat screen display, comprising:

annealing a sheet of 5182 aluminum alloy material to a fully soft O-temper condition;

cold rolling the sheet to achieve thickness reduction in the range 20 to 30%; and,

forming an internal frame for a flat screen display from said annealed and cold rolled sheet material.

15. The method in accordance with claim 14, wherein said cold rolling step comprises cold rolling the sheet to achieve thickness reduction of 26%.