JPS6160133B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an iron-containing zinc alloy shot for blasting.

Blasting is a well-known method for cleaning metal surfaces. The blasting method is a method of removing scale, etc. that adheres to the surface of the object to be treated by projecting particles onto the surface of the object to be treated.The projecting particles include steel shot, stainless steel cut wire, aluminum cut wire, alumina particles, and various other materials. something is being used. Generally, when shot blasting die-cast products, it is desirable to change the blasting shot material depending on the material to be blasted. Usually, a metal shot of the same type as the object to be blasted is used. However, when blasting aluminum die castings or small die castings, there is a high risk of explosion of the powdered aluminum when using aluminum cut wire (aluminum cannot be made into shots, so the wire is cut), so steel shot or stainless steel cut wire is used. wire is used. However, when a steel shot is used, rust occurs due to adhesion of pulverized iron powder, and when a stainless steel cut wire is used, there are problems such as deep cuts at the edges and damage to the material. Therefore, instead of these, zinc shots have recently become important. Due to its moderate softness and other physical properties, zinc shot exhibits good blasting action (abrasive action) without damaging the material, does not impair the beauty or corrosion resistance of the product, and is relatively inexpensive.

In general, zinc shots for blasting are manufactured by shooting high-purity zinc, which is called the purest zinc. As a preferred shotting method, a method in which the molten metal is allowed to fall naturally into water from a molten metal reservoir placed on a water tank through a nozzle with a fine pore size has been advocated, and good results have been obtained. 1000~1400μ
Spheroidized shots without sharp edges can be produced, mainly in the particle size range of .

It has been found that when such zinc shots are used to plaster aluminum die-cast products in particular, blackening of the die-cast surface can occur. The finished state of shot blasted products is determined by the material of the product to be treated, the material and form of the shot, and the blasting conditions (shot discharge speed, number of discharged particles, etc.), and the cause of blackening is a mixture of various factors. It seems that there is. As a result of many studies, it has been found that it is effective to increase the hardness of the zinc shots a little more than before as one measure to prevent blackening.

Adding alloying elements can be considered as a method for improving the hardness of zinc shots.Additional elements can improve hardness and improve grain boundaries, ductility,
It must not have a detrimental effect on the properties of the shot such as toughness. Furthermore, when producing shots by the above-mentioned underwater gravity drop method, the viscosity of the molten metal has a large effect on the shape and other properties of the formed shot, so the alloying elements must not increase the viscosity of the molten metal. . It has been discovered that iron is effective as an additive element that satisfies these requirements. By adding 0.01 to 1.0% iron, a zinc alloy shot for blasting having a suitable hardness with a Vickers hardness of 40 to 60 can be produced. Preferably, the iron-containing zinc alloy shot is produced by an underwater gravity drop method.

Thus, the present invention provides a zinc alloy blasting shot comprising zinc alloy grains containing 0.01 to 1.0% iron by weight. . Furthermore, the present invention provides 0.01 to 1.0
A molten zinc alloy containing 0.01 to 1.0 wt.
A method of making zinc alloy blasting shot comprising zinc alloy grains containing % iron by weight is also provided.

The present invention will be explained in detail below.

The blasting zinc alloy shot according to the present invention contains iron in an amount of 0.01 to 1.0% by weight. Iron content is 0.01%
If the amount is less, the desired hardness improvement effect will not be achieved;
If it is more than 1.0%, the hardness becomes too high. Impurities that are unavoidably contained in the zinc used during manufacturing are mixed into zinc alloy shot, but the amount of impurities should preferably be maintained at the level of the purest zinc, or at the worst, the level of impurities of distilled zinc or runoff zinc. It is. Cadmium is easily entrained in zinc, but cadmium should be reduced to a minimum for environmental hygiene reasons at shotblasting sites.

Zinc alloy shot is produced by shooting a molten metal of purest zinc with a specified amount of iron added by several methods. Further, since distilled zinc and runoff zinc already contain a specified amount of iron, the molten metal may be prepared using these molten metals as they are or by adding iron up to a specified amount. Furthermore, since distilled zinc and runoff zinc still contain a considerable amount of impurities, it is also advantageous to pass them through a rectification column once to remove impurities. For example, by passing distilled zinc once through a purifying column, a molten zinc alloy containing approximately 0.03% iron, substantially free of cadmium, and having a low content of expensive indium can be obtained.

Shotting can be effected using a number of granulation methods known in the art, such as spraying, impingement, in which the molten metal is poured onto a disc for dispersion, but the preferred method is the natural underwater method. be. This method is
As mentioned above, droplets of molten metal are allowed to fall gently and naturally into water from a molten metal reservoir installed on a water tank through a nozzle, and the molten metal temperature, the depth of the molten metal in the molten metal reservoir, the shape and dimensions of the nozzle, and the distance between the nozzle and the water surface are By carefully controlling the water temperature, etc., shots with appropriate particle shape and particle size distribution can be produced.

FIG. 1 shows an example of equipment for carrying out the above-mentioned molten metal gravity fall method. This equipment consists of a water tank 1 and a molten metal reservoir 10. The water tank 1 is composed of a molten metal dripping section 2 and a produced shot extraction section 3. The melt dripping section 2 is provided with an inclined bottom wall 4 and the product shot extraction section 3 is provided with a stainless steel wire mesh basket, for example, for receiving the product shot produced in the melt dripping section 2 and discharged along the inclined bottom wall 4. A collection container 5 like this is housed at the lower end. A molten metal reservoir 10 is installed directly above the molten metal dripping section 2 by a suitable support structure 11. Molten metal reservoir container 10
is divided into a pouring chamber 12 and a reservoir chamber 13, and a nozzle 15 is installed on the bottom wall of the reservoir chamber. A thermocouple 16 for measuring the temperature of the molten metal and a float 17 for measuring the depth a of the molten metal are provided in the reservoir chamber 13. The distance between the lower end of the nozzle 15 and the water surface L is displayed as b. Water is supplied to the water tank 1 through a water injection pipe 6, while water is discharged through an overflow portion 7. Furthermore, a circulating water pipe 8 incorporating a suitable pump is provided. A thermometer 9 for measuring water temperature and a heater 20 for controlling water temperature are provided in the water tank dripping section 2, and an immersion heater 21 is provided in the shot extraction section 3. These heaters 20 and 21 are connected to a thermistor.

The molten zinc stored at a predetermined depth and temperature in the molten metal storage container 10 is discharged through a nozzle 15 to the water surface directly below it, and is cooled and solidified by the water at a predetermined temperature in the water tank 1. It becomes a shot and accumulates in a collection container.

Preferably, the nozzle 15 is made of, for example, alumina,
It is made of ceramic such as silicon nitride or silicon carbide. It has been found that the produced shot is greatly influenced not only by the nozzle diameter but also by the nozzle material, and that it is better to use ceramic rather than metal for the zinc shot grains that are the object of the present invention. This seems to be related to the problem of wettability between the molten zinc metal and the nozzle surface, and when the molten zinc metal droplets are released from the nozzle, the better the breakage of the molten zinc metal droplets from the nozzle, the more easily the generated shots become spherical. It is also easy to stabilize. An example of nozzle 15 is shown in Figures 2 and 3, here of a five-hole type. The number of nozzles used in the reservoir and the number and arrangement pattern of nozzle holes in each nozzle can be determined as appropriate in relation to the production rate and the like. The nozzle 15 is fitted into a hole formed in the bottom wall of the reservoir 10 so that its lower end slightly protrudes from the hole. The nozzle hole formed in the nozzle 15 has a profile as shown in FIG. greatly influenced,
The nozzle hole diameter referred to herein is defined.

Stable production of zinc alloy shot for blasting is possible by selecting an appropriate combination within the following conditions: Zinc molten metal temperature 550-610℃ Zinc molten metal depth 30-60cm Nozzle hole diameter 0.3-0.7mm Nozzle bottom end ~Water surface distance 10mm or less Water temperature 30~50℃ The temperature of the molten metal in the reservoir is controlled at a temperature of 550~610℃. If the molten metal temperature falls below 550°C, the produced shots will not become spherical and will tend to become linear, making production unstable. On the other hand, when the temperature exceeds 610°C, evaporation of the molten zinc increases, and the resulting shots become spheroidized and the particle size distribution becomes unstable.

The molten metal depth provides a static pressure head as a driving force for the molten metal dripping through the nozzle, and if it is less than 30 cm, the production rate will decrease and the yield will also deteriorate.
A molten metal depth exceeding 60 cm results in spheroidization of the formed shot and poor stability of particle size distribution.

The nozzle hole diameter should be 0.3 to 0.7 mm, preferably 0.5 mm in order to obtain a shot with a main diameter of 1.4 to 0.7 mm.
It is said to be before and after. If the nozzle hole is smaller than this range, clogging will easily occur, and if it is larger than this range, the generated shot will become larger.

The distance between the lower end of the nozzle hole and the water surface is preferably 10 mm or less and as small as possible. As this distance increases, the impact that the molten metal dripping from the nozzle hole receives on the water surface increases, making it more likely to flatten. However, if this distance is made too small, the tip of the nozzle will be submerged in the water due to the shaking of the water surface, hindering the continuity of operations. The nozzle is also more likely to crack. A spacing of about 3 to 5 mm is preferable.

The water temperature is 30 to 50°C, preferably around 45°C. If the temperature is lower than 30°C, the cooling effect will be too strong and it will be difficult for the produced shots to become spherical, while if it exceeds 50°C, the number of shots with large particle sizes will increase and the yield of 1.4 to 0.7 mm diameter shots will decrease.

The zinc alloy shot used in the present invention is
These are mainly spherical shots with a particle size of 500 to 2000μ, especially 1000 to 1400μ. The Bitkers hardness ranges from 40 to 60, making it suitable for blasting various die-cast products, especially aluminum die-cast products.

EXAMPLE A zinc alloy shot was manufactured using the equipment shown in the figure. Adding galvanized wire to the purest zinc
Molten alloys of 0.05% Fe-Zn and 0.10% Fe-Zn were prepared. The test conditions were as follows: Molten metal temperature: 600℃ Molten metal depth: 50cm Nozzle: Made of silicon nitride Nozzle diameter: 0.6mm Water surface to nozzle distance: 3mm Water temperature: 40 to 47℃ The particle size distribution of the produced shot was as follows. +1680μ 43% −1680～+1400 21.6% −1400～+1000 62.9% −1000～+710 11.0% −710μ 0.3% Bitkers hardness of production shot (test load 100
g) is shown below along with that of a shot using the purest zinc.

Vickers hardness purest zinc 36.1 0.05%Fe-Zn 43.3 0.10%Fe-Zn 48.9 It can be seen that the hardness of shot can be increased by adding iron. When this shot was used to blast an aluminum die-cast product, a clean appearance was obtained.

As described above, the present invention has succeeded in developing a zinc alloy shot having improved hardness and other properties that is particularly suitable for shot blasting of die-cast products, and which provides an extremely excellent finished appearance. be.

[Brief explanation of the drawing]

FIG. 1 is a partially sectional front view of an example of shot manufacturing equipment, FIG. 2 is a top view of the nozzle, and FIG. 3 is a sectional view of the nozzle taken along the line X--X in FIG. 1: Water tank, 2: Molten metal dripping part, 3: Shot extraction part, 5: Collection container, 10: Molten metal reservoir container, 1
5: Nozzle, L: Water surface.

Claims (1)

[Claims] 1. A zinc alloy shot for blasting comprising zinc alloy grains containing 0.01 to 1.0% by weight of iron. 2 Zinc alloy particles containing 0.01 to 1.0 wt% iron are produced by holding a molten zinc alloy containing 0.01 to 1.0 wt% iron in a reservoir equipped with a nozzle on the bottom wall, and allowing it to drip naturally into water through the nozzle. A method of manufacturing a zinc alloy shot for blasting comprising: