JPS6017013B2 - 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-Kunaj stainless steel has been widely used.

However, if the structure is complex, such as an exterior part, sweat, seawater, etc. may act on the gaps during carrying, causing corrosion, so nickel-based alloys such as the well-known Cr-Ni-Mo alloys are not used. 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 desired as materials for exterior parts.

An object of the present invention is to provide an exterior part for a portable watch using 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 16-23%Mo 7-10 Fe l~10 Cu 2-6 Col. 5-2.5 V.O. 25-0.30 C.O. 05 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.

13% in Ni base shows corrosion resistance effect, but 16% or more is required to maintain sufficient corrosion resistance.
If it exceeds %, the alloy will have poor malleability and will be difficult to process. M
o exhibits excellent corrosion resistance in corrosive environments containing halogen ions, and has a more pronounced effect on corrosion resistance after plating of mesh bands than 7%, and when it exceeds 10%, hot workability and machinability deteriorate. to degrade.

Although Fe is an element that impairs corrosion resistance, it is useful for improving machinability. For the purpose of manufacturing the material at low cost, it is treated as a ferroalloy, so it is inevitably included, but the upper limit was set at 10% for corrosion resistance, and the upper limit was set at 1% lower than the inevitable content. 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.

Co and V are qualitatively said to have no effect on the pitting corrosion potential, but Cr, Mo, Fe, Cu
In the coexistence with C and C, the pitting corrosion resistance is enhanced by controlling the crystal grain size or by fixing C.

Since C combines with Cr to form Cr charcoal and deteriorates corrosion resistance, it must be reduced as much as possible, and taking into account the effect with V, it is set to 0.05% 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 thickness of 0.6 skin ◇. 1st
Table 2 Table 2 ◎ Good ○ Fair [Tensile strength, 40+ Red] △ Slightly inferior × Poor In Table 1, sample repair 1 is the invention alloy, and samples 2 to 5 are comparative alloys.

In Table 1, sample location. 1 is the invention alloy, and 2 to 5 are comparative alloys. As for the test method, a salt water mist test according to JIS was carried out in an artificial sweat immersion groove at 35 pm for 5 days.

In addition, in the case of a band made of SUS31 & material as a comparison sample,
Noticeable red rust occurred on the entire band. However, in the band obtained according to the present invention, almost no rust was observed. The value of the pitting corrosion potential was defined as the value measured at 0.1 mA/me.

Machinability was determined by applying a load of 500 grams to a 3-class high-speed steel drill and calculating the degree of machinability.

Claims (1)

[Claims] 1. Cr 16-23% by weight. Mo7-10%, Fe1-10%, Cu2-6%, Co
1.5-2.5%, V0.25-0.30%, C0.0
An exterior part for a mobile watch, characterized in that an alloy is used as a material, with a content of 5% or less and the balance being Ni and unavoidable impurities.