JP2003253410A - Method of producing magnesium thin sheet and electronic equipment case made of magnesium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnesium thin sheet which is useful as various electronic equipment cases. <P>SOLUTION: A magnesium billet of is subjected to hot extrusion molding into a planar sheet having a sheet thickness of 0.4 to 1.5 mm. After that, at least one side of the planar sheet is subjected to facing so as to be finished into a product sheet thickness. The magnesium planar sheet obtained by the extrusion molding is faced, preferably, by a facing quantity of ≥0.09 mm per side. By this method, a magnesium thin sheet having a sheet thickness of 0.3 to 1.2 mm can be produced. The obtained magnesium thin sheet exhibits and excellent surface condition freed of die marks and oxide films produced on the extrusion molding by the facing, and is used as the casing material of various electronic equipments. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention has a plate thickness of 0.3 to 1.2 mm.
And a method for manufacturing a magnesium material thin plate, and an electronic device case using the magnesium material thin plate.

[0002]

2. Description of the Related Art Magnesium materials have been used as casing materials for portable electronic devices by taking advantage of their excellent electromagnetic shielding function, light weight, vibration damping ability and heat radiation ability. In the close-packed hexagonal crystal structure of magnesium, in addition to the bottom-bottomed system, which tends to occur relatively easily at room temperature, there are column-shaped and conical-sided systems that are hard to slide at high temperatures. Moreover,
It is also a material with a high work hardening rate. Therefore, the magnesium material is inferior in cold workability and is practically 10 to 20.
There is a limit to cold working of about%.

Although a manufacturing method of rolling → pressing or forging is partially adopted for manufacturing an electronic device case using a magnesium material thin plate, most of the manufacturing method is a die casting method in consideration of the material of the magnesium material. is there. In the die casting method, molten magnesium material is pressed into a mold to form the product shape, but wrinkles are likely to occur on the surface of the die casting, and the reinforcement rim provided on the inner surface of the casting, the boss for screwing, etc. Is likely to occur. If there are defects such as wrinkles or burrs, the appearance of die cast products will be significantly impaired.
A putty processing step for filling the defective portion is required. The putty treatment is a very inefficient process of visually observing the surface of the die cast casting and manually repairing the detected individual defective portions, and as a result, it is a factor of increasing the cost of the die casting product.

[0004]

If a thin plate-shaped magnesium material can be manufactured by a method that replaces the die-casting method, the putty treatment that causes a cost increase can be omitted, and a relatively inexpensive magnesium material thin plate can be provided. As such a method, there is a method of forming a cast tabular magnesium material into a thin plate shape by rolling, pressing, forging, or the like.
It is introduced in the Gazette. However, since the plate-shaped magnesium material is manufactured by the casting method, there is a limit to the plate thickness that can be cast, and even when the thixomold method, which requires a complicated equipment configuration, is used, the plate thickness is slightly less than 1 mm. Due to the restriction on the plate thickness that can be cast, it is necessary to set a large reduction rate in the subsequent processing steps such as rolling, pressing, forging, etc., which increases the rate of defective products due to processing defects.
Manufacturable magnesium material thin plates are also limited to Al-Mg alloys containing Al: 4 to 20% by mass, and thus lack versatility.

[0005]

The present invention has been devised to solve such a problem, and a magnesium material flat plate extruded into a flat plate shape is chamfered,
It is an object of the present invention to manufacture a magnesium material thin plate which is thinner than a conventional magnesium material plate and has a good surface property at low cost in a small number of steps.

In the manufacturing method of the present invention, in order to achieve the object, a billet of a magnesium material is hot-rolled to a plate thickness of 0.4.
After being extruded into a flat plate of up to 1.5 mm, at least one surface of the flat plate is chamfered to finish to a product plate thickness. The magnesium material flat plate obtained by extrusion molding is preferably chamfered with a chamfering amount of 0.09 mm or more per one surface.

According to this method, the plate thickness is 0.3 to 1.2 m.
It is possible to manufacture a sheet of magnesium material of m. The obtained magnesium material thin plate has a beautiful surface condition in which die marks and oxide film generated during extrusion molding are removed by chamfering, and if necessary surface treatment such as chemical conversion treatment, anodization and painting is performed. It is used as a casing material for various electronic devices. In this specification, pure magnesium and magnesium alloys are collectively referred to as “magnesium material”.

[0008]

[Function] With magnesium materials, the higher the material temperature, the lower the critical shear stress in the column-shaped conical system and conical conical system.
It can be said that the material is suitable for hot working because it can be worked by various methods at 0 to 400 ° C. Further, with the technical progress of the extrusion molding method, it has become possible to extrude a magnesium material into a thin plate having a plate thickness of about 0.4 mm. But,
An oxide film is formed on the surface of the magnesium material flat plate obtained by extrusion molding, and innumerable die marks extend in the longitudinal direction of the flat plate. The die mark and oxide film are reflected on the coating film surface even after coating the extruded product, and deteriorate the surface property of the product. In addition, variations in the thickness of the extruded magnesium material flat plate are unavoidable. On the other hand, the magnesium material has extremely excellent machinability as compared with the aluminum alloy, and does not generate long chips that hinder continuous cutting.

The present invention focuses on the fact that the magnesium material is excellent in hot workability and machinability, and by combining extrusion molding for producing a magnesium material flat plate and chamfering for making a product plate thickness, It is possible to manufacture a magnesium material thin plate of 0.3 to 1.2 mm. In extrusion molding, the flat plate of magnesium material is made to have a plate thickness of 0.4 to 1.5 mm, which is a plate thickness that can be sufficiently achieved by the current extrusion molding method. Milling machine, flap wheel,
A scarfer or the like is used to remove the oxide film and die marks on the surface of the extruded material of the magnesium material flat plate, and to eliminate the variation in the plate thickness.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Magnesium materials usable in the present invention include pure Mg and AZ31, AZ21,
There are ZK30, ZK10, ZK60, M1, M4, M5 and the like. A magnesium material is cast into a billet according to a conventional method, and if necessary, the skin is peeled off, and then the billet is heated to 130-45.
It is preheated to 0 ° C., set in an extruder, and extruded on a magnesium material flat plate having a plate thickness of 0.4 to 1.5 mm at an extrusion speed of 2 to 30 m / min. Generally, the lower the preheating temperature and the extrusion speed are set, the more the shape accuracy of the extruded product is improved, but the shape accuracy of the extruded product is not so required in the method of the present invention in which the product sheet thickness is finished by the chamfering after the extrusion molding. . Therefore, the preheating temperature and the extrusion speed can be increased, and the productivity of extrusion molding is improved. However, if there is an excessive variation in the thickness of the magnesium material flat plate obtained by extrusion molding, it is necessary to set a large amount of chamfering in the next step, resulting in a decrease in yield. In this respect, the preheating temperature is 130 to 450 ° C, the extrusion speed is 2 to
30 m / min is an extrusion condition effective for suppressing the variation of the plate thickness within the range of the target plate thickness ± 0.04 mm.

The target thickness of the magnesium material flat plate obtained by extrusion molding is selected in the range of 0.4 to 1.5 mm. As the target plate thickness approaches the lower limit of 0.4 mm, the preheating temperature and extrusion speed are set lower. On the other hand, since it is intended for electronic device cases, the upper limit of the target plate thickness is set to 1.5 mm in consideration of portability of electronic devices. The magnesium material flat plate is surface-oxidized by contact with the atmosphere when it is extruded from the die exit of the extruder, and the film thickness is several μm.
An oxidative discoloration layer of about m is formed. Further, due to friction with the bearing of the extrusion die, countless die marks extending in the longitudinal direction of the flat plate are attached to the flat plate of magnesium material. The plate thickness also varies within the target plate thickness ± 0.04 mm.

Defects such as an oxidative discoloration layer, die marks, and variations in plate thickness can be removed by chamfering following extrusion molding. That is, when a flat plate of a magnesium material having a plate thickness of 0.4 to 1.5 mm is chamfered, the oxidative discoloration layer and the die mark are removed from the plate surface, and the plate thickness variation is also eliminated. By setting the amount of chamfering to 0.09 mm or more, defects such as an oxidation discoloration layer, die marks, and variations in plate thickness are efficiently removed, and a flat plate of magnesium material is finished to a product plate thickness. The chamfered magnesium material flat plate has a beautiful metallic luster and has a good surface condition without uneven color or unevenness. Therefore, it can be used as a product even after being face-polished, but the designability can be improved by chemical conversion treatment, anodic oxidation, painting, etc. The coating film or coating film formed by the chemical conversion treatment or anodization prevents the magnesium material from directly contacting the oxidizing atmosphere and improves the oxidation resistance.

The magnesium material thin plate finished to the product plate thickness is processed into a product shape by pressing, forging or the like. For use as an electronic device case, pressing or forging is performed so that the surface of the chamfered magnesium material flat plate faces the outside. After processed into product shape, chemical conversion treatment, if necessary,
Surface finish such as anodic oxidation and painting is applied. The casing material produced in this way is used in various electronic devices such as mobile phones, portable players, and notebook computers by utilizing the excellent electromagnetic shielding properties, light weight properties, vibration damping properties, and heat dissipation properties of magnesium materials. It

[0014]

Example A billet having a diameter of 204 mm to be subjected to extrusion molding was prepared by peeling a billet obtained from various molten magnesium materials. After preheating the billet, the billet is loaded into a container of an extruder equipped with an extrusion die having a width of 100 mm and a slit corresponding to the plate thickness,
A magnesium material flat plate was extruded into each plate thickness shown in Table 1 at an extrusion speed of 5 m / min. When the surface of the obtained magnesium material flat plate was observed, numerous die marks and oxide films were detected. After the magnesium material flat plate was cooled to room temperature, the oxide film and the die mark were removed by chamfering, and the magnesium product thin plate of the target product thickness was finished.

[0015]

When observing the magnesium material thin plate after the surface cutting, the oxide film and the die mark were completely removed from any of the thin plates, and the appearance had a metallic luster without unevenness or color unevenness. The plate thickness variation was extremely small, and the product had high shape accuracy. A clear paint and a paint containing a coloring pigment were applied to each magnesium material thin plate, and a clear paint film and a colored paint film were formed by drying and baking. When the surface after coating was visually observed, no irregularities or coating film defects were detected, and both the clear coating film and the colored coating film had high flatness. Therefore, it is understood that the magnesium material thin plate manufactured according to the present invention can be used as a casing material having a beautiful surface texture.

For comparison, magnesium alloy AZ91 was melted and cast into a die casting mold at a molten metal temperature of 620 to 660 ° C. to cast a box-shaped casting having an average plate thickness of 1 mm. As a result of observing the box-shaped casting, wrinkles were found at the confluence of the molten alloy in the mold, and sink marks were detected at the rim and boss.
When a cast magnesium material having defects such as wrinkles and burrs is coated, the defects are reflected in the coating film and unevenness occurs on the coating film surface, so it was necessary to repair the defective portion with putty treatment.

[0018]

As described above, the present invention focuses on the fact that the magnesium material is excellent in hot workability and machinability, and extrudes a magnesium material flat plate having an intermediate plate thickness and Finished to product thickness. The oxide film and die marks generated on the surface of the magnesium material flat plate by extrusion are removed by chamfering, and the fluctuation of the thickness of the magnesium material flat plate is also eliminated by the chamfering, so the magnesium material thin plate with excellent surface properties and shape accuracy Is obtained. The obtained magnesium material thin plate is used as a casing material for various electronic devices such as mobile phones, portable players, laptop computers, etc. by utilizing the excellent electromagnetic shielding property, lightweight property, vibration damping property, and heat dissipation property of magnesium material. To be done.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B21K 23/00 B21K 23/00 // C22F 1/00 612 C22F 1/00 612 623 623 631 631Z 673 673 ( 72) Inventor Masayuki Kobayashi F-202, 1-2-1, Nishi 2-chome, Toride-shi, Ibaraki Limited F-term in Project One (reference) 4E029 AA07 4E087 CA21 DB04 DB24 HA91

Claims (3)

[Claims] 1. A magnesium material characterized by hot-extruding a billet of a magnesium material into a flat plate having a plate thickness of 0.4 to 1.5 mm, and then at least one surface of the flat plate is chamfered to obtain a product plate thickness. A method for manufacturing a thin plate of material. 2. The method according to claim 1, wherein the flat plate is chamfered with a chamfering amount of 0.09 mm or more per one surface. 3. An electronic equipment case made of a magnesium material, which comprises a magnesium material thin plate as a base material, which is machined into a product shape by press molding or forging so that the chamfered surface faces the outside of the case.