JPH03131B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a method for manufacturing a portable watch dial using a metal that exhibits superplasticity in a specific temperature range.

(Prior art) The dial of a portable watch usually has two or more legs planted on the back side in order to position and fix it to the movement. A time index, a maker mark, etc. are integrally formed on the surface of the watch by implantation. Therefore, in addition to requiring many difficult machining steps to manufacture conventional dials, there is also the problem that the dial is easily subject to thermal deformation when brazing the supports, etc. It had

To solve this problem, the technology proposed in Japanese Patent Application Laid-Open No. 50-55521 uses a metal that exhibits superplasticity in a specific temperature range to create a dial that includes time indicators, maker marks, supports, etc. The idea is to reduce costs by molding the whole part in one piece, but when considering the allowable plate thickness for a dial of a portable watch, the molding load becomes excessive, resulting in, for example, corner parts. , protruding parts perpendicular to the dial, etc.
For areas where a large amount of deformation is required on a thin dial,
Breakage due to overstretching of the material, insufficient molding due to a decrease in plastic flow, and unfilled areas called ghosts are likely to occur on the surface of the dial where the supporting foot molding is located, so the above technology is not suitable. The problem is that it is impossible to mold high-quality dials.

(Purpose) The present invention was made in view of the above problems, and its purpose is to provide a time indicator having a height several times the thickness of the dial without causing deformation of the dial itself. An object of the present invention is to provide a new method for manufacturing a dial of a portable watch, which enables accurate and easy protrusion molding of a support, a foot, etc. on a dial.

(Means for Achieving the Object) That is, the present invention is a dial manufacturing method for achieving the above object, in which superplastic working is performed until a certain strain or a certain load necessary for molding is reached, and then a certain By keeping the load applied to the material and causing it to creep deform, the apparent strain rate of the material is reduced, and the height on both sides of the dial is one to several times the thickness of the material. The indicators and supports can be easily and completely molded down to the smallest detail.

(Example) Therefore, the details of the present invention will be explained below based on an example.

FIG. 1 shows an example of a manufacturing process for a dial of a portable watch based on the method of the present invention, and reference numerals 1 and 2 in the figure are upper and lower molds used for this molding.
The lower die 1 has a supporting foot 3 to be formed on the back side of the dial plate 3.
A recess 1a corresponding to d is bored, and
The upper die 2 disposed oppositely thereon is used to form time indicators 3a, maker marks 3b, and calendar display window frames 3c to be formed on the surface of the dial 3, as shown in FIG. The recess 2a is accurately carved.

A metal that exhibits superplasticity at a specific temperature, for example, a metal with a weight ratio of 20 to 24% is added to the lower mold 1 configured as described above.
The basic composition is a Zn-Al eutectoid alloy containing Al, and a Zn-Al-Cu-Mg alloy with a microcrystalline powder structure is made by adding 0 to 4.0% by weight of Cu and 0 to 1.0% by weight of Mg. A disk-shaped metal material A that has been heat-treated to bring about a maximum of 1500% or more plastic deformation in a temperature range of 200 to 300°C is placed, and this material A is heated through molds 1 and 2 depending on its composition. a specific temperature range determined by
For example, heat it to 200-300℃ and under this condition,
The upper mold 2 is rolled down onto this material A at a constant speed.

By the way, the deformability of metals that generally exhibit superplasticity depends on the strain rate.On the other hand, when the same forming is applied to a material using compressive force, the rate of deformation of the material after forming or the thickness of the material The smaller the value, the larger the value.
In other words, the smaller the thickness of the material, the more strain it will undergo during superplastic processing, and if this becomes excessive, it will lead to material breakage, so the period until a certain stage of forming, that is, the forming The upper mold 2 is rolled down at a slow speed of, for example, about 5 mm/min until the strain or load required for this reaches a certain level.

As this superplastic working progresses, the upper and lower surfaces of the material A have recesses 1a and 2 of the molds 1 and 2, as shown in FIG.
An incomplete convex portion is formed in the material A, and together with this, a large internal stress is generated in the material A. When these reach a certain stage, the upper mold 2 is stopped while a constant load is applied.

This operation reduces the apparent strain rate of the material A, and during this time the material A undergoes creep deformation and penetrates into the minute portions of the recesses 1a and 2a of the molds 1 and 2, completing the molding.

〔Example〕

22 wt% Al, 0.5 wt% Cu, 0.05 wt%
Manufacturer: A thin disc-shaped material with a thickness of 0.53 mm and a diameter of 30 mm based on a Zn-22% Al eutectoid fine-grained superplastic alloy containing Mg, with a time display and a Geneva pattern with a height of 0.30 mm on the surface. The upper die with the mark engraved and the diameter
It is placed between the lower mold with a 0.65 mm and 1.65 mm deep foot-forming recess, and while the above material is heated to 260°C and a maximum load of 6 kg/mm ² is applied,
Plastic processing was performed at an initial forming speed of 5.0 mm/min, and then
When the material was subjected to creep deformation by applying the above load for 300 seconds, it was observed that the time indicators and supporting legs grew on the upper and lower surfaces of the material at the speed shown in Figure 2, and the height was relatively high. low time index is 150-240
While the molding was completed in seconds, the long legs, which are three times as thick as the material, continued to grow at a constant rate and reached the required length in approximately 300 seconds. Furthermore, when this method was compared with the conventional implantation method, it was found that the resulting product had no significant difference in appearance and the manufacturing cost could be reduced to 1/12.

(Effects) As described above, according to the present invention, a superplastic metal sheet material is subjected to superplastic processing until forming reaches a certain stage, and then a certain load is applied to this thin sheet material to cause creep deformation. As a result, the stress that inevitably occurs inside the thin plate material due to superplastic processing is reduced by creep processing, resulting in less residual stress and
A dial plate with high reliability in terms of strength can be integrally molded. In addition, the creep processing that follows superplastic processing can create a state where the apparent strain rate is reduced, so the elongation of the thin plate material in an environment exhibiting superplasticity can be used to improve the fine details on the mold surface. It becomes possible to easily and completely transfer even the uneven portions to the thin plate material, and a high-class portable watch dial can be easily and inexpensively manufactured.

[Brief explanation of the drawing]

Figures 1A and 2B are diagrams showing the process of molding a portable watch dial based on the method of the present invention, Figure 2 is a diagram showing the progress of molding in the creep process, and Figures 3A and 3B are FIG. 3 is a cross-sectional view and a plan view of a watch dial formed by the same process as above. 1...Lower mold, 2...Upper mold, 3...Clock dial, A...Superplastic metal thin plate material.

Claims (1)

[Claims] 1. A superplastic metal thin film material is interposed between one mold formed by carving a recess corresponding to a time indicator, etc. and the other mold formed by carving a recess corresponding to a foot, and the thin A first step of superplastically working the thin sheet material at a strain rate corresponding to its thickness while heating the sheet material to a temperature determined by its composition; From the stage when distortion occurs to the extent that it affects the molding process until the molding is completed, a load to the extent that creep deformation occurs is applied to the mold, and each surface of the thin plate material is provided with the time indicator and support. A method for manufacturing a portable watch dial in which a time indicator, etc. and supporting legs are integrally formed on the front and back surfaces of the dial by a second step of growing the legs.