JPH02277702A - Exterior parts for watch using stainless steel sintered body and manufacture thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a watch exterior part using a stainless steel sintered body and a method for manufacturing the same.

[Conventional technology]

Conventionally, the methods for forming parts include plastic processing, mainly forging,
Casting processing centered on die casting, lost wax, etc.
A typical example is fine cutting. However, recently, the needs of the market have diversified, and the range has expanded from simple shapes to complex shapes. In particular, for stainless steel used in watch exterior parts that require good appearance and environmental resistance, the above manufacturing methods have advantages and disadvantages, and it is often difficult to select a manufacturing method.In some cases, it is difficult to select a manufacturing method. Sometimes.

[Problems to be Solved by the Invention] The present invention provides an economical exterior part for a watch that has excellent appearance and environmental resistance even if it has a complicated and diverse shape as described above, and a method for manufacturing the same. The purpose is to provide

[Means for Solving the Problems 1] The exterior parts for watches using the stainless steel sintered body of the present invention and the manufacturing method thereof have an average particle size of 20 LLm or less and a carbon content of 1.0% by weight (hereinafter referred to as wt%). ) A corrosion-resistant coating is applied to the surface of a stainless steel sintered body obtained by molding, degreasing, and sintering an injection molding compound made by mixing the following stainless steel powder and an organic binder mainly composed of wax, resin, etc. This is an exterior part for a watch using a stainless steel sintered body having layers.

The manufacturing method involves mixing injection molding stainless steel powder produced by the atomization method with an average particle size of 20 μm or less and a carbon content of 10% by weight or less, and an organic binder mainly composed of wax, resin, etc. After molding an exterior part for a watch in an injection molding machine using an injection molding compound made of A method for manufacturing a watch exterior part using a stainless steel sintered body, which is characterized in that the sintered body is made into a sintered body, and the surface of the sintered body is subjected to a corrosion-resistant coating treatment. The sintering temperature was set at 1350℃ in a reduced pressure atmosphere.
The following is a method for manufacturing a watch exterior part using a stainless steel sintered body, which is characterized by adjusting the carbon content of the sintered body to 0.08 wt% or less.

Hereinafter, the exterior part for a timepiece according to the present invention will be specifically explained along with its manufacturing method.

In this invention, the composition of the stainless steel powder used in the exterior parts for watches using a stainless steel sintered body using the injection molding method and the manufacturing method thereof is such that the carbon content is 1.0 wt%.
In the following (hereinafter simply referred to as %), other constituent elements are the same as those of known stainless steels.

Normally, corrosion resistance is the most important environmental resistance for watch exterior parts made of stainless steel, and specularity is the most important for the appearance. Therefore, in the manufacturing process of molten stainless steel, it is necessary to reduce the amount of carbon content. I am making an effort.

However, when manufacturing stainless steel sintered bodies using the injection molding method, even if raw material powder with low carbon content is used, no advantage can be expected in the manufacturing process, and the carbon content of the sintered bodies is It has also been found that there is no advantage in reducing the amount due to carbon contamination caused by the organic binder during degreasing. However, it has been found that by sintering in a reduced pressure atmosphere, both carbon originating from the raw material powder and carbon originating from the organic binder can be removed in the same way.

The reasons for limiting the numerical value of the carbon content of stainless steel powder will be explained below.

The amount of carbon contained in a sintered body obtained by injection molding a mixture of stainless steel powder and a thermoplastic resin binder, degreasing the molded body, and subjecting it to 4H vacuum sintering (00001 torr), which is commonly used in industry. The relationship between the amount of added carbon and the amount of added carbon in stainless steel powder is shown in Figure 1. As is clear from Figure 1, if the raw material powder carbon content exceeds 1.0%, the carbon content of the sintered body will not be sufficiently reduced, so the upper limit of the added carbon content of stainless steel powder is set at 1.0%. Limited.

Next, in order to increase the density of the final sintered body, it is important to set the particle size of the stainless steel powder to an average particle size of 20 microns or less, more preferably an average particle size of 10 microns or less. That is desirable.

Next, the composition of the injection molding compound will be described.
The injection molding compound referred to here is mainly composed of the above-mentioned stainless steel powder having a composition of Cr-containing stainless steel such as austenitic stainless steel or ferritic stainless steel, thermoplastic resin, and wax. It is a mixture of an organic binder containing a plasticizer, lubricant, degreasing accelerator, and surfactant.

When the above injection molding compound is injection molded and sintered after degreasing, it is necessary to carry out at least the first stage of the sintering process in a reduced pressure atmosphere.

Here, the first stage of the sintering process refers to the process until the density ratio of the sintered body reaches about 90%.When the density ratio of the sintered body exceeds 90%, most of the pores in the sintered body disappear. CO becomes a closed pore and is generated by reduction and decarburization reactions under a reduced pressure atmosphere as described below.
This is because it becomes difficult to remove gas from the pores of the sintered body, making it impossible for this reaction to proceed efficiently.

In addition, the sintering atmosphere needs to be an atmosphere that can reduce oxides such as Cr that inhibit atomic diffusion during sintering, and can also remove carbon that is largely contained in the degreased body after degreasing. . To meet this requirement, hydrogen and a reduced pressure atmosphere can be used, as in the production of ordinary stainless steel sintered materials.

However, the reduction and decarburization reactions in hydrogen are as follows, respectively: M O + Ht = M + H20 (M: Gold a:)
... Reduction of HgO→CO+H, (Dan; solid solution carbon)・
...The lower the decarburization PH20/PH, the more the reduction progresses, and the P
Since decarburization progresses when Ha O/PH* is high,
It is difficult to make both reactions proceed efficiently at the same time. In particular, when stainless steel contains hard-to-reducible Cr oxide and the degreased material contains high carbon, it is not recommended to use a hydrogen atmosphere. It's not a good idea.

On the other hand, reduction and decarburization in a reduced pressure atmosphere are as shown in the following equation: MO+nee M+CO...reduction and decarburization proceed simultaneously, and the reaction can be made more efficient (proceeding) by removing CO gas by ζ exhaust. Furthermore, the values of oxygen and carbon contained in the final sintered body are lower under reduced pressure than in a hydrogen atmosphere, so in the manufacturing method according to the present invention, sintering is performed under reduced pressure. In order to efficiently progress the reduction and decarburization of Cr oxides, the pressure of the reduced pressure atmosphere is preferably 0.01 torr or less, and the hot water temperature range is preferably 1050°C to 1350°C. , is necessary only during the process in which the decarburization reaction is in progress; therefore, in the process after the completion of the reaction, a non-oxidizing atmosphere such as an inert gas (nitrogen, argon) or a low dew point hydrogen atmosphere is used as a protective atmosphere other than reduced pressure. It is preferable that

As mentioned above, the surface of the stainless steel sintered body for watch exterior parts, which is obtained by sintering in a reduced pressure atmosphere and has excellent corrosion resistance, is coated with plating, ion blating, etc.
By applying a corrosion-resistant coating layer, it is possible to obtain an exterior part for a watch that has excellent corrosion resistance and mirror finish.

Next, the sintering method according to claim 3 will be described.

As mentioned above, the amount of residual carbon in the sintered body is determined by the decarburization reaction under reduced pressure before sintering.

However, by keeping the temperature at which decarburization reaction is possible at 800°C to 1200°C for a certain period of time, the amount of residual carbon decreases, and by reducing the amount of carbon in the sintered body to 0.08 wt% or less, It was found that the density of cohesion was improved.

As described above, by the method of the present invention, it is possible to efficiently manufacture a watch exterior part using a high-density stainless steel sintered body having excellent corrosion resistance.

[Example] Stainless steel powders having the compositions shown in Table 1 were produced by water atomization method, and the results of investigating the powder properties of these steel powders are summarized in Table 2. A compound obtained by kneading 46vo and 1% organic binder was injection molded into a test piece with a width of 40 mm, a length of 20 mm, and a thickness of 2 mm at an injection nozzle temperature of 145° C. and a mold temperature of 30° C. The injection molded product was heated to 600°C from room temperature at a rate of +10°C/h in a nitrogen atmosphere, and then heated to 600°C.
Degreasing treatment was carried out by holding the sample for 1 hour. Sintering is 0.0001t
After holding the temperature at 1135°C for 2 hours in a reduced pressure atmosphere of
I held it for h.

Table 2 also shows the results of the investigation on the produced sintered body.

From Tables 1 and 2, it can be seen that the steel powder of the present invention has excellent injection moldability in a wide range of stainless steel compositions, and the sintered body properties are equivalent to those of conventional products.

Regarding the thus obtained sintered watch exterior parts, a product application example of a band piece, which is one of the exterior parts for a wristwatch, using the manufacturing method according to the present invention, and an MIM method that does not use the manufacturing method according to the present invention. Table 3 shows the results of testing and evaluation of comparative application examples and general melted materials.

Table 4 ■) Sintered density is measured using the Archimedes method.

2] Corrosion resistance test was conducted in a sealed container at 40°C ± 1°C semi-immersion, and the presence or absence of rust was observed using a 20x scope.5 3) For specularity, polishing was performed with #1200 waterproof paper. Thereafter, the puff was coated with an A1.01 abrasive material and polished, and the results were visually confirmed by five people based on the melted material.

4) For each evaluation, ◯ indicates good, X indicates poor, and △ indicates that it is unclear.

5) Artificial seawater is 5% NaCL.

Further, in Table 4, the wristwatch band pieces of the product application examples according to the present invention shown in Table 3 were subjected to surface treatment, and their corrosion resistance and adhesion were evaluated.

1) The corrosion resistance test was carried out in a sealed container at 40°C±l'C semi-immersion, and the presence or absence of rust was observed using a 20x scope.

2) Regarding adhesion, a test piece of a wristwatch band piece was held in a vise and bent at 90 degrees, and the presence or absence of peeling of the film was checked using a 20x scope.

As can be seen from Table 4, it was confirmed that the surface treatment properties were also comparable to those of ingot material.

Next, the machinability of the sintered body according to the present invention was evaluated. Table 5 shows the results.

(Test conditions) (1) Machine used: High-speed drilling machine (2) Drill used: φ1mm high speed steel (3) Number of revolutions: 7.90ORPM (4) Cutting oil
Nijiron CS Table For comparison, Table 5 is a comparison of the number of holes that can be penetrated when the materials used in the test are 1 mm thick plates and drilled with a high-speed drilling machine.

The reason why the penetration value differs depending on the number of experiments is that
This may be due to variations in the polishing conditions of the drill or the materials selected, so it seems appropriate to look at the average value, so the average value is shown.

As can be seen from Table 5 above, the material according to the present invention has better machinability than the ingot material.

Furthermore, since exterior parts for watches are polished to give them decorative properties, polishability is also an important factor. Therefore, the polishability was evaluated.

Using a sintered body according to the present invention Bramedia Walnut Corn In the process of wet barrel → dry barrel completion ■　MIM ■Forging ■ Lost wax 3 levels were mirror polished. The results are shown in Table 6.

Table 6 O: Good Δ: Inferior These results show that the sintered body of the present invention is superior to forged products or lost wax products.

Photo 1 is an internal photo of a wristwatch band piece according to the present invention, and Photo 2 is an internal photo of a wristwatch band piece according to the comparative application example shown in Table 3.

You can see the difference in bore diameter and density. Furthermore, as can be seen from Table 5, the corrosion resistance and specularity were comparable to those of the ingot material, demonstrating the superiority of the present invention.

The present invention is applicable not only to wristwatch band pieces, but also to exterior parts in all fields, such as wristwatch cases, decorative items such as cufflinks and buckles, and knobs and decorative parts for mined products.

[Effect of the invention] The present invention provides particles with an average particle diameter of 2, produced by the atomization method.
Corrosion resistance is achieved by molding, degreasing, and predetermined sintering using an injection molding compound made by mixing injection molding stainless steel powder with a diameter of 0 μm or less and a carbon content of 1.0 wt% or less and an organic binder. In addition to improved machinability and mirror finish, it is also possible to stably provide metal parts with improved mechanical properties, even complex parts such as exterior parts for watches. Furthermore, it is expected that the present invention will improve the characteristics of stainless steel parts and expand the range of application.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between the carbon content of a stainless steel sintered body and the raw material powder content. Photo 1 is a photo showing the crystal structure of the stainless steel sintered body of the present invention. Photo 2 is a photo showing the crystal structure of the conventional example (comparative application example). Applicant: Seiko Epson Corporation

Claims (1)

[Claims] 1. The average particle size is 20 μm or less, and the carbon content is 10% by weight (
A stainless steel sintered body obtained by molding, degreasing, and sintering an injection molding compound made by mixing stainless steel powder (hereinafter referred to as wt%) and an organic binder whose main components are wax, resin, etc. Exterior parts for watches using a stainless steel sintered body with a corrosion-resistant coating layer on the surface. 2. Average particle size 20 μm manufactured by atomization method
In the following, we use an injection molding compound made by mixing injection molding stainless steel powder with a carbon content of 1.0% by weight or less and an organic binder whose main components are wax, resin, etc., and use an injection molding machine to make a watch. After forming a molded body for an exterior part for a watch, the molded body is degreased and then sintered, at least the first stage is sintered in a reduced pressure atmosphere to form a sintered body for an exterior part for a watch, and then the sintered body is A method for producing an exterior part for a watch using a stainless steel sintered body, characterized in that the body surface is coated with a corrosion-resistant coating. 3. The sintering temperature was set to 135 in a reduced pressure atmosphere before sintering.
4. A method for manufacturing a watch exterior part using a stainless steel sintered body according to claim 2 or 3, characterized in that the carbon content of the sintered body is adjusted to 0.08 wt% or less at a temperature of 0° C. or lower.