JPS61143502A - Production of granular material of lead alloy - Google Patents

Abstract

PURPOSE:To obtain easily a spherical granular material of a lead alloy by forming a cooling liquid such as liquid paraffin contained into a rotary drum under high speed rotation into a laminar state by the centrifugal force of said drum and injecting the molten lead alloy from a nozzle onto the above- mentioned cooling liquid layer. CONSTITUTION:Any of the liquid paraffin, glycerol or aq. glycerol soln. as the cooling liquid (a) is put into the rotary drum 1 having an end plate 2 and the drum 1 is rotated at high speed by an electric motor 3 via a belt 4. The liquid (a) receives the centrifugal force from the drum 1 and is formed into the laminar state with the plate 2 as a gate. Molten solder is then continuously injected from a nozzle 5 under the gaseous pressure exerted thereto. The continuous flow of the molten solder injected from the nozzle is cut by the shearing force of the liquid (a) run at the peripheral speed corresponding to the high- speed rotation of the drum 1 and is granulated in the liquid (a), by which the spherical solder grains for cream solder are obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an improvement in a method for producing lead alloy particles, and is useful for producing solder powder used in cream solder.

Prior Art and Problems The present inventors have studied the practical application of the rotary water spray method as a method for producing metal powder or fine wire, and have
Considerable results have been achieved with Al-based alloys.

FIG. 1 shows the apparatus used in the rotary water atomization method. In FIG. 1, l is a drum, has an edge plate 2 at the upper end, and is rotated at high speed by an electric motor 3 via a belt 4. 5
The nozzle continuously sprays molten metal under pressure using gas pressure.

When producing, for example, metal powder by the rotary water atomization method, first, a cooling medium is placed in a drum, and the drum is rotated at high speed. The cooling medium is subjected to centrifugal force depending on its specific gravity, circumferential speed, etc., and when the centrifugal force becomes considerably larger than the gravity acting on the cooling medium, as shown in Figure 1, the cooling medium a is formed in a layered manner using the edge plate 2 as a dam. Then,
A nozzle injects molten metal in a continuous stream toward a layer of cooling medium. However, the layer surface is running at a circumferential speed associated with the high-speed rotation of the drum, and this speed is faster than the flow speed of the continuous flow of molten metal, so a shearing force acts on the molten metal flow, and this shearing force When a certain value is reached, the molten metal is sheared (divided) and granulated in the presence of a cooling medium. The shear force acting on the molten metal flow reaches the above-mentioned constant value when the amount of contact of the molten metal with the cooling medium reaches a certain value. It is done.

In this method for producing metal powder using the rotary water atomization method, the production conditions can be made constant by making the drum rotation speed constant and the molten metal jetting rate constant, and since this constant can be easily ensured, metal particles uniformity can be easily achieved.

Furthermore, the nozzle can be brought close to the surface of the layer of the cooling medium, and the contact time of the molten metal with air can be kept to a very short time, so that oxidation of the metal particles can be sufficiently prevented.

The present inventors focused on the advantages of the rotary water spray method, and
An attempt was made to apply the rotary water spray method to the production of solder grains used in cream solder.

' So, cooling water circumferential speed: 30~60 m/1tec
It is known that the above solder particles can be produced with the particle size required for cream solder under the following conditions: drum rotation speed 23000 to 6000 rpm, nozzle diameter = 0.5mm, solder injection pressure 2ka/(4). I got it.

However, the obtained solder grains were flaky and flaky.

By the way, in the solder grains used for cream solder,
To prevent oxidation due to air contact during storage, e.g.
Measures such as vacuum storage have been taken, but it is desired that the surface area subject to oxidation be as small as possible, and the flaky shape is not preferred, and a spherical shape is advantageous.

OBJECTS OF THE INVENTION In view of the above, an object of the present invention is to provide a method for producing lead alloy granules by which spherical solder particles for cream solder can be produced by the above-mentioned rotary water spray method.

Structure of the Invention The method for producing lead alloy granules according to the present invention includes placing one of liquid paraffin, glycerin, and an aqueous glycerin solution as a cooling liquid in a rotating drum, and rotating the rotating drum to form a cooling water liquid by centrifugal force. This method is characterized in that the lead alloy is formed into a layer, and the molten lead alloy is continuously injected from a nozzle into the cooling liquid layer to granulate the lead alloy.

The particle size of the metal particles obtained by the rotary water spray method is determined by the injection speed of the molten metal, the injection temperature, and the circumferential speed of the coolant. Since the required particle size is 20 to 80 μm,
The injection speed is 6 to 8, preferably 7 m/B with a nozzle diameter of 0.5 mm, and the injection temperature is 120 to 200°C.
The circumferential speed of the coolant is 30 to 60 m/flee.

The alloy system of the lead alloy is adjusted so that injection can be performed under the above-mentioned injection temperature, and in the examples, for example, P b
-Bi alloy is used. The amount of Bi added is 32 to 5
Q wt 96 de Ruru.

DESCRIPTION OF EXAMPLES Hereinafter, examples of the present invention will be described in comparison with comparative examples. The lead alloy used was 55.8wt%Bi-44.
, 2wt% pb.

Example 1 Glycerin was used as the coolant. This cooling liquid was put into a rotating drum having an inner diameter of 5001 nm, and the drum was rotated so that the peripheral speed of the inner surface of the cooling layer formed by centrifugal force was 40 rrL/sec. Under such rotation, the diameter (L
The Bi-pb alloy described above was injected onto the coolant surface from a 5 fi* graphite nozzle at an injection temperature of 200° C. and an injection rate of 7 WL/geC. The obtained granules are shown in Figure 2 (A) (2
As shown in the 40x micrograph), it is almost spherical and oriented.
The particle size was approximately 30 μm.

Example 2 The same procedure as Example 1 was carried out except that an 80% glycerin aqueous solution was used as the cooling liquid. The obtained granules were approximately spherical.

The particle size was 48.4 μm.

Example 3 The same procedure as in Example 1 was carried out except that a 36% glycerin aqueous solution was used as the cooling liquid. The obtained particles were approximately spherical and had a particle size of 67.5 μm.

Example 4 The same procedure as on the actual flow side 1 was carried out except that liquid paraffin was used as the cooling liquid. The obtained particles were almost spherical, as shown in Figure 2B (240x photograph), and the particle size was about 30 μm.

Comparative Example 1 The same procedure as Example 1 was carried out except that water was used as the cooling liquid. The obtained granules were flaky and flaky as shown in Figure 3A (240x photograph).

Comparative Example 2 The same procedure as in Example 1 was carried out except that a 1% aqueous solution of polyethylene glycol 4000 was used as the cooling liquid.

The obtained granules were flaky and flaky as shown in Figure 3B (240x photograph).

Comparative Example 3 The same procedure as Example 1 was carried out except that a 2% aqueous solution of polyethylene glycol 2000 was used as the cooling liquid.

The obtained granules were flaky and flaky as shown in FIG. 3C (photograph magnified at 240 times).

Effects of the Invention The method for producing lead alloy granules according to the present invention involves the selection of a cooling liquid (liquid paraffin , glycerin solution) to obtain spherical particles. Since it is spherical, it has a small surface area and is advantageous in preventing oxidation during storage, making it useful as a method for producing solder grains for 6D and cream solder. Furthermore, since paraffin and glycerin are the 7-lux components of the cream solder, the solder grains can be mixed with flux and used as they are without washing, making it easy to manufacture the cream solder.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the rotary water spray device used in the present invention, FIG. 2 A1 and FIG. FIG. 3C is an enlarged photograph (240x magnification) showing lead alloy grains in a comparative example. In the figure, l is a drum and 5 is a nozzle. Procedural amendment band (method) April 2, 1985 Patent A No. 265022 No. 3, person making the amendment Relationship with the case Patent applicant address 1-32-21 Higashi-Toyonaka-cho, Toyonaka-shi, Osaka Name Onaka Itsuo 4, Agent 662 Address 15-11-6 Kadosho, Nishinomiya City, Hyogo Prefecture Subject of amendment (1+ Brief description of drawings column 7 of specification, Contents of amendment

Claims (1)

[Claims] (1) Liquid paraffin as a cooling liquid in the rotating drum.
Add either glycerin or glycerin aqueous solution, rotate the rotating drum to form the above cooling liquid into a layer by centrifugal force, and continuously inject molten lead alloy into the above cooling liquid layer from the nozzle. A method for producing lead alloy granules, which comprises granulating a lead alloy.