JPS6012401B2 - Method for producing granular metal bismuth - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing granular metal bismuth, which has conventionally been difficult to granulate because it is a low melting point metal.
More specifically, the present invention relates to a method of producing spherical particles by flowing molten bismuth into water.

Conventional methods for obtaining bismuth granular metal include 1) using nonflammable oil maintained at a temperature slightly lower than the melting point of bismuth as a cooling medium, and slowly cooling the metal bismuth melt by dropping it into the oil; 2) Adjusting the amount of molten metal flowing down by varying the depth of the molten metal on a thin slope with a large number of holes drilled therein, dropping the molten metal into water located at a distance of 3 mounds or less below the dripping thin plate, At this time, there is a method of heating the droplet in the middle of dropping with flame from the side (Hakama Seki Sho 57-19305).

However, method 1) requires post-processing such as degreasing after obtaining the metal particles, and there are cost problems due to consumption of media oil, and method 2) Since the molten material is heated by flame at the moment it falls from the perforated plate into the water, it is complex in terms of equipment and requires advanced operating techniques, and great care must be taken to equalize the particle size produced. I need. An object of the present invention is to solve the above-mentioned problems and provide a method for efficiently producing granular metal bismuth using simple operations.

In order to achieve this objective, the present inventors conducted intensive research on a method for obtaining granular materials by flowing a molten bismuth metal into water, and conducted experiments that found that almost spherical granular bismuth metal could be reliably obtained under certain conditions. We have arrived at the present invention based on this idea.

That is, in the method of the present invention, metal bismuth molten in a heating container is placed at a position of 25 to 35 sails above the water surface of an aquarium maintained at a temperature of 760°C or higher, preferably 80 to 85°C, and is preferably 1.5 feet or less in diameter. A perforated plate with a small hole of 0.3 to 1.5 sails in its bottom is installed, and in this perforated plate there is 330 to 360 qo, preferably 3 qo, which is about 100 qo higher than the melting point of bismuth.
A molten metal bismuth of 40 to 35 mm is supplied so as to maintain the layer thickness at 25 mm or less, and allowed to flow down and cool.

The molten material supplied to the perforated plate flows down through the holes in the perforated plate, and by the time it reaches the hot water surface, it forms a molten droplet and is rapidly cooled in the hot water to form the desired granular metal. In the method of the present invention, the diameter of the small hole formed in the bottom of the perforated plate used is 1.5 mm or less, preferably 0.3 to 1.5 mm.

If the diameter is larger than this, the melt will remain in the form of long and thin threads and will be quenched in water, resulting in a needle-like product. In order to avoid this, it is possible to set the perforated plate at a height above the water surface so that the filamentous molten material can be cut in the air.In this case, the filamentous material will be cut and the molten material will become shot-like, but it will not come into contact with the water surface. Perhaps due to the pressure, the spherical shape deforms and becomes a flat shape, which is not preferable.

Therefore, in the present invention, the perforation of the perforated plate is specified and the installation position of the perforated plate is limited to a height of 25 to 35 feet from the water surface. Next, the melt is poured into a perforated plate, and the depth of the melt when flowing down from the small holes of the perforated plate is set to 25 sides or less, but if the thickness exceeds this, the force to push it out of the perforated plate becomes stronger. Perhaps because of this, the amount of water flowing down increases and it falls to the water surface in the form of strings, leaving only needle-like pieces.

The temperature of the water that cools the melt flowing down from the perforated plate is 75:00.
Above, preferably 80 to 85%.

Below this temperature, most particles do not become spherical, but rather take on the shape of a tail, a tadpole, or a comb. However, if the water temperature exceeds 90 qo, the quenching effect is inhibited and the particles that have already arrived tend to aggregate with each other, so it is preferable to maintain the temperature within the above range so as not to get too high. By adjusting the water temperature in this way, a nearly spherical shape can be obtained, probably due to the slow cooling effect of the falling molten bottle. The various conditions for granulating bismuth metal according to the present invention explained above are essential requirements for obtaining the desired granular product with high uniformity, and since they are due to their combined effect, it is not necessary to omit even one condition. Can not.

For example, by setting the water temperature to around room temperature, increasing the distance between the position of the perforated plate and the water surface, and making the falling height of the molten material significantly higher than the level of the present invention described above, the falling molten material can be raised to a high level. When photographed with a speed camera, the molten material that passes through the holes in the perforated plate is initially string-like, and soon breaks into small pieces and becomes granular, but due to air resistance etc. when falling, it is unable to maintain its spherical shape, and it always falls vertically. You can see that it has fallen into the water with its head turned in the direction of its tail, which looks like a tamapod or a comb.
Thus, when it is immersed in low-temperature water and rapidly cooled, it remains in almost the same shape as when it fell, and it is almost impossible to obtain a uniformly shaped sphere. Next, regarding the temperature of the bismuth metal melt as another regulatory condition during granulation, it is necessary that the temperature of the melt during granulation be sufficiently higher than the melting point of bismuth. It is the same as in the case of granulation, but in the case of bismuth, care must be taken because even if the melt temperature is too high, granules will not be obtained and will become thin, amorphous, or powdery.

A suitable temperature of the melt during granulation is 330 to 36,000°C, more preferably 340 to 350°C. The material for the perforated plate may be any material as long as it does not contaminate bismuth, such as forming an alloy with bismuth.
1.2 iron plate material is preferred.

According to the method of the present invention, it is possible to efficiently produce nearly spherical shots with substantially uniform particle size, as shown in the examples below.

Examples will be described below.

Example 1 Metal bismuth was melted and the temperature was maintained at 350 qo.
A stainless steel perforated plate with a small hole of 1.2 ribs in diameter was placed three gunwales above the hot water surface at 0:00, and after keeping the perforated plate warm at 300q0, the molten material was poured into its layer thickness. The amount of injection was kept almost constant during injection so that it felt good on the skin.

The obtained granular product has a nearly spherical shape, and its particle size distribution is 14,000 mm (5.1%) and 14,000 to 3,360 mm (87.5 mm).
%, -3360〃7.4%.

Example 2 Bismuth metal 10.5k9 was melted and the temperature was maintained at 350°C, and a small hole with a diameter of 0.5 mm was made on the 1.2-thick side, above the surface of the hot water at 75-78°C. A perforated plate made of a stainless steel plate was placed, and after keeping the perforated plate at 300° C., the above-mentioned molten material was injected so that the layer thickness was i5 to 2 mm, and granulation was performed.

As shown in the table below, the results showed that the boar had a diameter of about 2 to 3 ribs and was nearly spherical.

Grain distribution ratio) Large grains were obtained with a bias in the range of 1.5 to 3 ribs in diameter.

As described above, according to the method of the present invention, particles with a narrow particle size distribution can be obtained, which is very convenient in use and contributes to an improvement in commercial value.

Claims (1)

[Claims] 1. A method for producing granular metal bismuth by flowing a metal bismuth melt down through pores into water, in which the melt is
diameter 1 held at a height of 25 to 35 mm above the water surface
．． Production of granular metal bismuth, characterized by supplying it into a perforated plate having pores of 5 mm or less, and cooling the melt by flowing it into water at 75° C. or higher while maintaining the depth of the melt to be 25 mm or less. Method.