JPS6017014B2 - Exterior parts for mobile watches - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exterior part for a portable watch made of a nickel-based alloy with improved corrosion resistance and workability.

Traditionally, austenitic stainless steel was used for watch exterior parts.
For example, 18Cr-I stainless steel has been widely used.

However, if the parts are complexly molded, such as exterior parts, sweat, seawater, etc. will act on the gaps during carrying and cause corrosion, making it difficult to use nickel-based alloys such as the well-known Cr-Ni-Mo alloy. However, no satisfactory product has been found, and the above-mentioned phenomenon is particularly severe when there are areas where the plating does not cover, such as mesh bands. In addition, in recent years, wristwatches have become increasingly thinner and smaller, and materials with excellent corrosion resistance, workability, and mechanical properties are now on sale as materials for exterior parts.

An object of the present invention is to provide a bag part for a portable watch made of a material with improved corrosion resistance and improved machinability.

The components of the alloy according to the invention are as follows in weight ratio:

Cr 18~23%Mo 7~10 Fe l~10 Cu 2-6 Nb 2 or less C.O. 06 or less Ni residual Next, the effect of adding each component and the reason for limiting the composition range will be described.

Ni is a base metal with sufficient solid solution of Cr and Mo,
It is an element involved in improving corrosion resistance and strengthening alloys. Cr is an element that has a remarkable effect of improving corrosion resistance and also improves the strength of the alloy.

In a Ni base, 13% shows a corrosion-resistant effect, but 18% or more is required to maintain sufficient corrosion resistance, and if it exceeds 25%, the alloy has poor malleability and becomes difficult to process. Mo exhibits excellent corrosion resistance in corrosive environments containing halogen ions, and has a 7% improvement in the corrosion resistance of mesh bands after plating.
The effect is more pronounced, and when it exceeds 10%, hot workability and machinability deteriorate.

Although Fe is an element that impairs corrosion resistance, it is useful for improving machinability. In order to treat the material as a ferroalloy for the purpose of manufacturing the material at low cost, the upper limit was set at 10% due to corrosion resistance, and the lower limit was set at 1% from the natural inclusion. Although Cu deteriorates chemical resistance, it has a high electrode potential with respect to hydrogen, increases the potential as an alloy, has the effect of improving local battery corrosion due to the potential difference with plating, and improving machinability.

It was set to 2% or more in terms of machinability, and 6% or less in terms of chemical resistance. Nb stabilizes C and prevents deterioration in corrosion resistance due to grain boundary precipitation of Cr charcoal, and at the same time increases the hardness of the alloy matrix.
It is an element that increases the degree of The effect of corrosion resistance increases in proportion to the amount added, but it was set to 2% or less in order to prevent deterioration of workability. Since C combines with Cr to form Cr charcoal and deteriorates corrosion resistance, it is necessary to reduce it as much as possible, and taking into consideration the effect of Nb, it is set to 0.06% or less.

Next, examples of the present invention will be shown. Table 1 shows composition examples in terms of weight ratio, and Table 2 shows the results.

The plate material for the corrosion resistance test sample had 25 x 25 ribs, and the mesh band was made from a wire rod with a diameter of 0.6 mm. 1st
Table 2 In Table 1, samples 1, 2 and 4 are the alloys of the present invention, and 3, 5
is a comparative alloy.

In Table 1, sample gunwale. 1, 2 and 4 are the alloys of the present invention; 3,
5 is a comparative alloy. The test methods were a salt water mist test according to JIS and a 5-day test using artificial sweat soaking bond 35qo.

In addition, in the case of SUS31 private village band as a comparison sample,
Noticeable red rust occurred on the entire band. However, the /-mind obtained according to the present invention showed almost no rusting. The value measured at 0.1 mA/ was taken as the pitting potential.

For machinability, a load of 500 grams was applied to a drill made from 3 ribs, and the degree of machinability was recorded.

Claims (1)

[Claims] 1 Weight ratio: Cr18-23%, Mo7-10%, Fe
1-10%, Cu2-6%, Nb2% or less, C0.06%
An exterior part for a portable watch, characterized in that the following alloy is used as a material, the balance being Ni and unavoidable impurities.